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Crest, Crown, or QSC?

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Anonymous
August 8, 2005 2:02:45 PM

Archived from groups: rec.audio.pro (More info?)

Hi,

I'm buying a power amp to power two JBL MP418S subwoofers - which are
rated as taking a maximum of 600 watts at 4-ohms.

I haven't bought a power amp in 25 years, so I know very little about
current amps, and I will likely not be able to hear the differences
between amps in a demo environment anyway. So I'm (once again) looking
to the knowledgeable folks on this board for advice. Budget is a
concern, but I'll spend more if there is a significant audible
difference. I *think* the most likely candidates are:

QSC RMX2450 (about $600)
Crest CPX2600 (about $530)
Crown CE2000 (about $650)

I'm leaning toward the Crest because it has a built-in crossover, has
the power I need, is the least expensive, and because Crest amps seem
to enjoy a good reputation. Do others agree?

As always, thanks in advance for all opinions and thoughts. This board
is a godsend to someone like me in my efforts to keep up with current
audio technology.

Dean

More about : crest crown qsc

Anonymous
August 8, 2005 5:14:01 PM

Archived from groups: rec.audio.pro (More info?)

In article <1123520565.516600.116090@g47g2000cwa.googlegroups.com>,
>
>I'm leaning toward the Crest because it has a built-in crossover, has
>the power I need, is the least expensive, and because Crest amps seem
>to enjoy a good reputation. Do others agree?

The Crown and QSC amps are fine too. I think some of the RMX series
QSC amps can also be ordered with a built-in crossover.

As always, make sure the crossover is complete and is both high and
low pass networks rather than just a low-pass.

>As always, thanks in advance for all opinions and thoughts. This board
>is a godsend to someone like me in my efforts to keep up with current
>audio technology.

I think all of these are fine amps and you should buy the one from the
dealer you like the most.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 8, 2005 9:04:36 PM

Archived from groups: rec.audio.pro (More info?)

"drichard" <DRichard@wi.rr.com> wrote in message
news:1123520565.516600.116090@g47g2000cwa.googlegroups.com
> Hi,
>
> I'm buying a power amp to power two JBL MP418S subwoofers
> - which are rated as taking a maximum of 600 watts at
> 4-ohms.
>
> I haven't bought a power amp in 25 years, so I know very
> little about current amps, and I will likely not be able
> to hear the differences between amps in a demo
> environment anyway. So I'm (once again) looking to the
> knowledgeable folks on this board for advice. Budget is a
> concern, but I'll spend more if there is a significant
> audible difference. I *think* the most likely candidates
> are:
>
> QSC RMX2450 (about $600)
> Crest CPX2600 (about $530)
> Crown CE2000 (about $650)
>
> I'm leaning toward the Crest because it has a built-in
> crossover, has the power I need, is the least expensive,
> and because Crest amps seem to enjoy a good reputation.
> Do others agree?

In terms of market penetration and reputation, it's probable
that QSC and Crown are well ahead of Crest. None of these
are shabby amps by any means but they are lower end of the
respective manufacturer's line. If you are interested in
stretching a buck, but still getting something that has a
decent reputation, there are always the Behringer Europower
EP2500.
Related resources
August 8, 2005 9:04:37 PM

Archived from groups: rec.audio.pro (More info?)

In article <H8mdndVZCrJCVWrfRVn-3g@comcast.com>,
"Arny Krueger" <arnyk@hotpop.com> wrote:

> If you are interested in
> stretching a buck, but still getting something that has a
> decent reputation, there are always the Behringer Europower
> EP2500.

i'm not certain that Behringer and "decent reputation" belong in the
same sentence.
--
Digital Services Recording Studios
http://www.digisrvs.com
Anonymous
August 8, 2005 9:59:50 PM

Archived from groups: rec.audio.pro (More info?)

John wrote:
> i'm not certain that Behringer and "decent reputation" belong in the
> same sentence.

See much past debate here and on the other audio newsgroups. There is
disagreement on this topic.
Anonymous
August 8, 2005 10:15:17 PM

Archived from groups: rec.audio.pro (More info?)

Crest for overall quality or Peavey CS Series for bang/buck performance.

Jonny Durango
Anonymous
August 8, 2005 10:35:23 PM

Archived from groups: rec.audio.pro (More info?)

John <are.you.crazy@sendmenomail.com> wrote:
> "Arny Krueger" <arnyk@hotpop.com> wrote:
>
>> If you are interested in
>> stretching a buck, but still getting something that has a
>> decent reputation, there are always the Behringer Europower
>> EP2500.
>
>i'm not certain that Behringer and "decent reputation" belong in the
>same sentence.

I would tend to agree. But more importantly, I'd MUCH rather have a
bottom-of-the line product from a high-grade manufacturer than a top
of the line product from a low-grade one.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 9, 2005 1:12:12 AM

Archived from groups: rec.audio.pro (More info?)

"Scott Dorsey" <kludge@panix.com> wrote in message
news:D d8mnb$g88$1@panix2.panix.com
> John <are.you.crazy@sendmenomail.com> wrote:
>> "Arny Krueger" <arnyk@hotpop.com> wrote:
>>
>>> If you are interested in
>>> stretching a buck, but still getting something that has
>>> a decent reputation, there are always the Behringer
>>> Europower EP2500.
>>
>> i'm not certain that Behringer and "decent reputation"
>> belong in the same sentence.
>
> I would tend to agree. But more importantly, I'd MUCH
> rather have a bottom-of-the line product from a
> high-grade manufacturer than a top of the line product
> from a low-grade one. --scott

We all would I'm sure, except for that little thing called
money.
Anonymous
August 9, 2005 10:55:51 AM

Archived from groups: rec.audio.pro (More info?)

Hi Arny, Scott, and all,

I appreciate the responses so far. I am still leaning toward the Crest
if I buy new, as the built-in crossover negates some of the price
difference. But I didn't realize the Behringer offered as much power as
it does at that price point, so I'll keep it in mind. I've bought some
Behringer gear and am not ashamed to say so, but I'm reluctant to skimp
when powering subwoofers. The Crest seems to offer some nice features
that might protect the speakers from being blown if something goes
awry.

There's also the possibility that I'll come across a great deal on a
used unit of one of the better amps, and that would be one way for me
to go. Anything I should be looking out for if I buy used?

Thanks again for all of the comments,

Dean
Anonymous
August 9, 2005 12:39:43 PM

Archived from groups: rec.audio.pro (More info?)

Hi Arny,

It's in the Crest performance series. It's at
www.crest-performance.com. I wish the crossover was between 100-120 for
my purposes, and you might be right that it won't end up being useful,
but 150hz might be OK.

Dean
Anonymous
August 9, 2005 12:51:59 PM

Archived from groups: rec.audio.pro (More info?)

Hi Arny,

I'm sorry, but I got lost in your technical explanation. Are you saying
the QSC is likely to have the least, or most, success powering a low
impedance load? The JBL subwoofers are rated at 4-ohms.

What is it about the Behringer amps that you find appealing, besides
the price?

I think all of the amps I looked at have a damping factor rated as
"greater than 300".

Dean
August 9, 2005 1:15:14 PM

Archived from groups: rec.audio.pro (More info?)

In article <1123595751.524371.310770@f14g2000cwb.googlegroups.com>,
DRichard@wi.rr.com says...
> Hi Arny, Scott, and all,
>
> I appreciate the responses so far. I am still leaning toward the Crest
> if I buy new, as the built-in crossover negates some of the price
> difference. But I didn't realize the Behringer offered as much power as
> it does at that price point, so I'll keep it in mind. I've bought some
> Behringer gear and am not ashamed to say so, but I'm reluctant to skimp
> when powering subwoofers. The Crest seems to offer some nice features
> that might protect the speakers from being blown if something goes
> awry.
>
> There's also the possibility that I'll come across a great deal on a
> used unit of one of the better amps, and that would be one way for me
> to go. Anything I should be looking out for if I buy used?
>
> Thanks again for all of the comments,

Since we're speaking of powering subwoofers, wouldn't the damping
factor be something worth looking at? I have heard that the higher
it is, the tighter the bass will be (and although I've done no
extensive tests, my experience seems to bear that out somewhat).
--
---Mikhael...
Anonymous
August 9, 2005 1:16:25 PM

Archived from groups: rec.audio.pro (More info?)

Hi,

I have some further questions for you and the others reading this,
since it's obvious the people answering my posts have a lot more
experience in these matters than I.

I'm getting back into a band, after being away from it for a long time
while my kids were younger. I envision this band will be playing small
to medium clubs and the occasional private party initally, eventually
some small outdoor festivals, and larger clubs, etc. Because they will
not be used in a permanent installation, speaker and amp protection are
factors in my buying decisions. I need a full-range PA since all
instruments will go through it.

I have a pair of Klipsch LaScala speakers left over from my old days as
a performer that I still consider nice speakers that should meet my
initial needs for mains. But they have always been a little shy in the
very deep low end. So I'm thinking that to start off I'll continue to
use the Klipsch as mains, but add subwoofers to get a stronger bottom
end, and biamp the system. I've listened to the JBL subwoofers, and
like them. So my plan right now is to buy a decent power amp and the
JBL subs, and if necessary, a crossover. To my ears, the Klipsch get a
little "boxy" (for lack of a better word) sounding around 80 hz or so,
which is why I thought crossing over at 100-150 hz made sense. I have
no experience to back that statement up, it just seemed logical to me.
If more experienced people than I feel that 150 hz is too high to cross
over, it will negate that advantage for the Crest amp, though are still
things about it that appealed to me. Are you familiar with the Klipsch
speakers?

Anyway, that's what I'm doing and how I'm going about it, and I'm
trying to benefit from the experiences of you and the others here to
make good decisions going forward. I very much appreciate yours and
Scott's and everyone's feedback. And I'm open to further suggestions.

Thanks,

Dean
Anonymous
August 9, 2005 2:13:31 PM

Archived from groups: rec.audio.pro (More info?)

"drichard" <DRichard@wi.rr.com> wrote in message
news:1123595751.524371.310770@f14g2000cwb.googlegroups.com
> Hi Arny, Scott, and all,
>
> I appreciate the responses so far. I am still leaning
> toward the Crest if I buy new, as the built-in crossover
> negates some of the price difference.

I'm kinda surprised and a little dismayed by the fact that
the Crest web site doesn't seem to know about CPX-series
amplifiers:

http://www.crestaudio.com/products/

Am I missing something?

I did manage to find that the built-in crossover is:

"150 Hz 24 dB per octave Linkwitz-Riley filter, tuned for
subs"

at least per www.zzounds.com .

I question the utility of a fixed-frequency crossover this
high for anything but rough-and-tumble SR.
Anonymous
August 9, 2005 2:59:19 PM

Archived from groups: rec.audio.pro (More info?)

"Michael" <ra3035@NOTfreescale.com> wrote in message
news:MPG.1d62766ce16ca3f498977f@news.freescale.net

> Since we're speaking of powering subwoofers, wouldn't
> the damping factor be something worth looking at?

With modern amps, just about any halfways decent amp is
going to have its source impedance in the LF range so low
that the DC resistance of most speaker cables swaps it.
Ironically, source impedance effects at very high
frequencies are prone to be larger.

Of the amps specificed, the QSC amp is most likely to have a
slightly elevated output impedance at very low frequencies
since the same circuit feature that allows its output
transistors to be mounted on a grounded chassis without
insulators seems to effectively put the power supply filter
caps in series with the speaker line, and outside the
feedback loop.

> I have
> heard that the higher it is, the tighter the bass will be
> (and although I've done no extensive tests, my experience
> seems to bear that out somewhat).

This is a more significant issue when comparing SS amps to
tubed amps, or tubed amps to other tubed amps.
Anonymous
August 9, 2005 3:26:24 PM

Archived from groups: rec.audio.pro (More info?)

Arny Krueger <arnyk@hotpop.com> wrote:
>"Michael" <ra3035@NOTfreescale.com> wrote in message
>news:MPG.1d62766ce16ca3f498977f@news.freescale.net
>
>> Since we're speaking of powering subwoofers, wouldn't
>> the damping factor be something worth looking at?
>
>With modern amps, just about any halfways decent amp is
>going to have its source impedance in the LF range so low
>that the DC resistance of most speaker cables swaps it.
>Ironically, source impedance effects at very high
>frequencies are prone to be larger.

This is still an issue when dealing with very-low-Z loads. Lots
of the PA guys will double-up cabinets for 4-ohm loads, and there
are some subwoofers out there that dip well below 8 ohms at some
frequencies even though they are rated as 8 ohms nominally.

So damping factor (which is really a silly way of describing actual
amplifier output impedance) can be important in the real world too.

A good rule of thumb is that if the 4 ohm power rating is twice the
8-ohm power rating, you have pretty good output Z. If the 2 ohm
power rating is actually twice that, you are doing even better.

>> I have
>> heard that the higher it is, the tighter the bass will be
>> (and although I've done no extensive tests, my experience
>> seems to bear that out somewhat).
>
>This is a more significant issue when comparing SS amps to
>tubed amps, or tubed amps to other tubed amps.

The problem is that a lot of older speakers are actually voiced to
be driven off of amplifiers with comparatively high output impedance.
If you put an Altec A-7 onto a brand new Hafler, you'll find the low
end is very depressed. On the other hand, if you put a typical EAW
cabinet onto an old Altec tube amp, the low end will be kind of bloated
and out of control (although it will probably be better on the 4-ohm tap).
It's because the speaker isn't designed to deal with an amp with that
impedance output.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 9, 2005 3:46:30 PM

Archived from groups: rec.audio.pro (More info?)

Hi Scott,

Yes, I planned to use a real crossover, as I'm aware of how efficient
the Klipsch are. I've got a 70's vintage QSC 400 watt power amp (don't
have the model number handy) that I used to power the LaScalas when
they were new, and it seems to work OK. Initially at least, I can use
it. Would you recommend the 2-ohm resistor even so? I'm buying the
Crest/QSC/Crown/Behringer power amp for the subwoofers only, not for
the Klipsch.

The whole idea is to reuse as much of my old stuff as I can, and the
LaScalas seem adequate for starters. I don't seem to mind them as much
as you, though I never liked the way they sound at the very low end.
But they sure were good to me when I was playing clubs in the 70's and
80's. I will probably replace them eventually but first the band has to
get off the ground. But I consider the subs/power amp combo almost a
requirement. I'll also look for a Rane crossover.

Thanks again,

Dean
Anonymous
August 9, 2005 4:02:28 PM

Archived from groups: rec.audio.pro (More info?)

"drichard" <DRichard@wi.rr.com> wrote in message
news:1123601983.004363.99590@z14g2000cwz.googlegroups.com
> Hi Arny,
>
> It's in the Crest performance series. It's at
> www.crest-performance.com. I wish the crossover was
> between 100-120 for my purposes, and you might be right
> that it won't end up being useful, but 150hz might be OK.
>

Thanks for the hint.

I notice that Crest says the following about their
crossover:

"Built-in 150Hz/18dB/octave Subwoofer"

That's significantly different from what zzounds said:

"150 Hz 24 dB per octave Linkwitz-Riley filter, tuned for
subs"

If I knew more about the application, I'd have a better
feeling about how this could work out.
Anonymous
August 9, 2005 4:05:06 PM

Archived from groups: rec.audio.pro (More info?)

"drichard" <DRichard@wi.rr.com> wrote in message
news:1123602719.359020.269470@g14g2000cwa.googlegroups.com


> I'm sorry, but I got lost in your technical explanation.
> Are you saying the QSC is likely to have the least, or
> most, success powering a low impedance load?

What I'm saying is that it might be a little different from
all the rest.

> The JBL subwoofers are rated at 4-ohms.

Shouldn't be aproblem.

> What is it about the Behringer amps that you find
> appealing, besides the price?

Price, price and oh by the way did I say price? ;-)

> I think all of the amps I looked at have a damping factor
> rated as "greater than 300".

That's pretty much what I see. Unfortunately that spec is
generally given without a frequency range. In general
assuming that it holds 20-20KHz is a mistake. It is more
likely to hold 20-2KHz, than 2 KHz 20 KHz.
Anonymous
August 9, 2005 4:45:03 PM

Archived from groups: rec.audio.pro (More info?)

Hi Scott,

Know of any collectors looking for them? Where would I find someone?
They're kind of beat up from many years of one-nighters, but work fine.
They are the industrial split model, black, and not as nice to look at
as the fine wood ones. I'd be happy to sell them for a good price.
Shipping would be an issue, of course.

Dean
Anonymous
August 9, 2005 4:45:55 PM

Archived from groups: rec.audio.pro (More info?)

What about the FA901? Where's it at?

drichard wrote:

>Hi Arny,
>
>It's in the Crest performance series...
>
>
Anonymous
August 9, 2005 6:04:37 PM

Archived from groups: rec.audio.pro (More info?)

drichard <DRichard@wi.rr.com> wrote:
>
>I have a pair of Klipsch LaScala speakers left over from my old days as
>a performer that I still consider nice speakers that should meet my
>initial needs for mains. But they have always been a little shy in the
>very deep low end. So I'm thinking that to start off I'll continue to
>use the Klipsch as mains, but add subwoofers to get a stronger bottom
>end, and biamp the system. I've listened to the JBL subwoofers, and
>like them. So my plan right now is to buy a decent power amp and the
>JBL subs, and if necessary, a crossover. To my ears, the Klipsch get a
>little "boxy" (for lack of a better word) sounding around 80 hz or so,
>which is why I thought crossing over at 100-150 hz made sense. I have
>no experience to back that statement up, it just seemed logical to me.
>If more experienced people than I feel that 150 hz is too high to cross
>over, it will negate that advantage for the Crest amp, though are still
>things about it that appealed to me. Are you familiar with the Klipsch
>speakers?

Yes, I agree with Steve Miller that the La Scalas "make my guitar go
straight ahead for miles and sound like it's coming through a telephone."

Lots of honk. Lots and lots of honk. These are speakers that are designed
for efficiency at all costs, from an era where amplifier power was very
expensive.

If you want to add subwoofers to these, you will need a real crossover,
not just a low-pass filter. I would suggest using an amplifier with
a very low damping factor on them too... or try just putting a big 2 ohm
power resistor in series with them. They are voiced to be driven off of
a ten-watt tube amp with a very high output impedance.

The boxiness and the honkiness isn't going to go away, although damping
the horn down with tar and sand might help a little. But the series
resistance may clean the bass up a lot.

I don't know what frequency you want to cross over at. It will depend
on the subs you use and your personal taste, as well as how loud you want
to run the system. That's why you need an adjustable crossover.

>Anyway, that's what I'm doing and how I'm going about it, and I'm
>trying to benefit from the experiences of you and the others here to
>make good decisions going forward. I very much appreciate yours and
>Scott's and everyone's feedback. And I'm open to further suggestions.

Try using your existing amps on the subs, get something like the baby
Hafler for the La Scalas and operate it with a series resistor. Get
a used Rane AC-22 crossover, which is nothing amazing but is cheap and
usable.

The smallest RMX-series amp from QSC is also not bad. Remember, ten
watts into the La Scala will fill an auditorium... you don't need a lot
of power.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 9, 2005 6:35:11 PM

Archived from groups: rec.audio.pro (More info?)

Hello All,

I have a couple of Mackies in the basement (1400i), and they've seemed fine,
but I don't ride 'em very hard, ... they don't get moved, etc. Sometimes I
think adding amps for monitors, or subwoofs, etc.,.... I always thought I'd
just add more Mackies, ... are they not well thought of in the industry
(anymore, or ever)? For service, quality, or value? Would they rate with the
three mentioned?

Thanks, Chris B.




"Scott Dorsey" <kludge@panix.com> wrote in message
news:D dahv0$6jf$1@panix2.panix.com...
> Arny Krueger <arnyk@hotpop.com> wrote:
> >"Michael" <ra3035@NOTfreescale.com> wrote in message
> >news:MPG.1d62766ce16ca3f498977f@news.freescale.net
> >
> >> Since we're speaking of powering subwoofers, wouldn't
> >> the damping factor be something worth looking at?
> >
> >With modern amps, just about any halfways decent amp is
> >going to have its source impedance in the LF range so low
> >that the DC resistance of most speaker cables swaps it.
> >Ironically, source impedance effects at very high
> >frequencies are prone to be larger.
>
> This is still an issue when dealing with very-low-Z loads. Lots
> of the PA guys will double-up cabinets for 4-ohm loads, and there
> are some subwoofers out there that dip well below 8 ohms at some
> frequencies even though they are rated as 8 ohms nominally.
>
> So damping factor (which is really a silly way of describing actual
> amplifier output impedance) can be important in the real world too.
>
> A good rule of thumb is that if the 4 ohm power rating is twice the
> 8-ohm power rating, you have pretty good output Z. If the 2 ohm
> power rating is actually twice that, you are doing even better.
>
> >> I have
> >> heard that the higher it is, the tighter the bass will be
> >> (and although I've done no extensive tests, my experience
> >> seems to bear that out somewhat).
> >
> >This is a more significant issue when comparing SS amps to
> >tubed amps, or tubed amps to other tubed amps.
>
> The problem is that a lot of older speakers are actually voiced to
> be driven off of amplifiers with comparatively high output impedance.
> If you put an Altec A-7 onto a brand new Hafler, you'll find the low
> end is very depressed. On the other hand, if you put a typical EAW
> cabinet onto an old Altec tube amp, the low end will be kind of bloated
> and out of control (although it will probably be better on the 4-ohm tap).
> It's because the speaker isn't designed to deal with an amp with that
> impedance output.
> --scott
> --
> "C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 9, 2005 7:38:05 PM

Archived from groups: rec.audio.pro (More info?)

drichard <DRichard@wi.rr.com> wrote:
>
>Yes, I planned to use a real crossover, as I'm aware of how efficient
>the Klipsch are. I've got a 70's vintage QSC 400 watt power amp (don't
>have the model number handy) that I used to power the LaScalas when
>they were new, and it seems to work OK. Initially at least, I can use
>it. Would you recommend the 2-ohm resistor even so? I'm buying the
>Crest/QSC/Crown/Behringer power amp for the subwoofers only, not for
>the Klipsch.

The resistor is to reduce the damping from the amplifier... you are
increasing the output impedance of the amplifier so it is closer to
what the speaker is voiced for. Try it and see. Either you'll like
what it does to the low end or you won't.

You know, you can sell those La Scalas to a collector for good money,
then use the cash to buy something more appropriate for the application, too.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 9, 2005 8:53:42 PM

Archived from groups: rec.audio.pro (More info?)

"chris berbaum" <qa1090@email.mot.com> wrote in message
news:D db0hg$kpf$1@avnika.corp.mot.com
> Hello All,
>
> I have a couple of Mackies in the basement (1400i), and
> they've seemed fine, but I don't ride 'em very hard, ...
> they don't get moved, etc. Sometimes I think adding amps
> for monitors, or subwoofs, etc.,.... I always thought I'd
> just add more Mackies, ... are they not well thought of
> in the industry (anymore, or ever)? For service, quality,
> or value? Would they rate with the three mentioned?
>

My Mackie 1200 was fine until the ribbon cables gave out,
and its fine now that the ribbon cables are replaced.

At the time I bought it, the 1200 seemed like a lot of amp
for the price, but now it looks pretty overpriced.
Anonymous
August 9, 2005 10:16:27 PM

Archived from groups: rec.audio.pro (More info?)

drichard <DRichard@wi.rr.com> wrote:
>
>Know of any collectors looking for them? Where would I find someone?
>They're kind of beat up from many years of one-nighters, but work fine.
>They are the industrial split model, black, and not as nice to look at
>as the fine wood ones. I'd be happy to sell them for a good price.
>Shipping would be an issue, of course.

I don't know. I'd start here, or in rec.audio.high-end. Do a search
on completed ebay auctions and see how many have gone on ebay and at
what prices. That's always interesting to start out with.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 10, 2005 1:42:32 AM

Archived from groups: rec.audio.pro (More info?)

Michael wrote:

> In article <1123595751.524371.310770@f14g2000cwb.googlegroups.com>,
> DRichard@wi.rr.com says...
> > Hi Arny, Scott, and all,
> >
> > I appreciate the responses so far. I am still leaning toward the Crest
> > if I buy new, as the built-in crossover negates some of the price
> > difference. But I didn't realize the Behringer offered as much power as
> > it does at that price point, so I'll keep it in mind. I've bought some
> > Behringer gear and am not ashamed to say so, but I'm reluctant to skimp
> > when powering subwoofers. The Crest seems to offer some nice features
> > that might protect the speakers from being blown if something goes
> > awry.
> >
> > There's also the possibility that I'll come across a great deal on a
> > used unit of one of the better amps, and that would be one way for me
> > to go. Anything I should be looking out for if I buy used?
> >
> > Thanks again for all of the comments,
>
> Since we're speaking of powering subwoofers, wouldn't the damping
> factor be something worth looking at? I have heard that the higher
> it is, the tighter the bass will be (and although I've done no
> extensive tests, my experience seems to bear that out somewhat).

The damping factor of *any* decent modern amplifer will be more than
adequate.

You should remember that a couple of feet of speaker cable will add more
resistance in circuit then the amplifier's own output impedance and make the
spec essentially meaningless anyway.

Funnily enough in days of old, *low* damping factor was used to enhance bass
response by allowing the speaker to resonate a bit more at it's natural
resonant frequency..

Graham
Anonymous
August 10, 2005 1:45:31 AM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:

> Arny Krueger <arnyk@hotpop.com> wrote:
> >"Michael" <ra3035@NOTfreescale.com> wrote in message
> >news:MPG.1d62766ce16ca3f498977f@news.freescale.net
> >
> >> Since we're speaking of powering subwoofers, wouldn't
> >> the damping factor be something worth looking at?
> >
> >With modern amps, just about any halfways decent amp is
> >going to have its source impedance in the LF range so low
> >that the DC resistance of most speaker cables swaps it.
> >Ironically, source impedance effects at very high
> >frequencies are prone to be larger.
>
> This is still an issue when dealing with very-low-Z loads. Lots
> of the PA guys will double-up cabinets for 4-ohm loads, and there
> are some subwoofers out there that dip well below 8 ohms at some
> frequencies even though they are rated as 8 ohms nominally.
>
> So damping factor (which is really a silly way of describing actual
> amplifier output impedance) can be important in the real world too.
>
> A good rule of thumb is that if the 4 ohm power rating is twice the
> 8-ohm power rating, you have pretty good output Z. If the 2 ohm
> power rating is actually twice that, you are doing even better.

To be honest Scott, that spec tells more about the power supply that the
actual *output impedance*.


> >> I have
> >> heard that the higher it is, the tighter the bass will be
> >> (and although I've done no extensive tests, my experience
> >> seems to bear that out somewhat).
> >
> >This is a more significant issue when comparing SS amps to
> >tubed amps, or tubed amps to other tubed amps.
>
> The problem is that a lot of older speakers are actually voiced to
> be driven off of amplifiers with comparatively high output impedance.
> If you put an Altec A-7 onto a brand new Hafler, you'll find the low
> end is very depressed. On the other hand, if you put a typical EAW
> cabinet onto an old Altec tube amp, the low end will be kind of bloated
> and out of control (although it will probably be better on the 4-ohm tap).
> It's because the speaker isn't designed to deal with an amp with that
> impedance output.

Indeed, although modern amps don't give the luxury of messing around like
that.

Graham
Anonymous
August 10, 2005 1:46:37 AM

Archived from groups: rec.audio.pro (More info?)

chris berbaum wrote:

> Hello All,
>
> I have a couple of Mackies in the basement (1400i), and they've seemed fine,
> but I don't ride 'em very hard, ... they don't get moved, etc. Sometimes I
> think adding amps for monitors, or subwoofs, etc.,.... I always thought I'd
> just add more Mackies, ... are they not well thought of in the industry
> (anymore, or ever)? For service, quality, or value? Would they rate with the
> three mentioned?

The technical performance is ok I believe but they're prone to self-destruction
due to overheating.

Not recommended for live work.

Graham
Anonymous
August 10, 2005 1:52:10 AM

Archived from groups: rec.audio.pro (More info?)

drichard wrote:

> Hi,
>
> I'm buying a power amp to power two JBL MP418S subwoofers - which are
> rated as taking a maximum of 600 watts at 4-ohms.
>
> I haven't bought a power amp in 25 years, so I know very little about
> current amps, and I will likely not be able to hear the differences
> between amps in a demo environment anyway. So I'm (once again) looking
> to the knowledgeable folks on this board for advice. Budget is a
> concern, but I'll spend more if there is a significant audible
> difference. I *think* the most likely candidates are:
>
> QSC RMX2450 (about $600)
> Crest CPX2600 (about $530)
> Crown CE2000 (about $650)
>
> I'm leaning toward the Crest because it has a built-in crossover, has
> the power I need, is the least expensive, and because Crest amps seem
> to enjoy a good reputation. Do others agree?
>
> As always, thanks in advance for all opinions and thoughts. This board
> is a godsend to someone like me in my efforts to keep up with current
> audio technology.

The RMXs are decently build and widely regarded but I'm not really
impressed by the circuitry which I consider to be rather 'agricultural'.
It's certainly no 'audiophile' amp.

I know some of the older Crest amps and they have the cleanest electronics
design of any of the big name amps IMHO and have better heatsinking than
QSC. No idea if the range you're looking at continues the tradition but
worth considering. I hope they aren't just a re-badged Peavey design now.
The Peaveys such as the CS range were also somewhat 'agricultural' in
their design.

Can't comment on the Crowns you mention but they've made some rubbish over
the last few years.

Graham
Anonymous
August 10, 2005 4:22:53 AM

Archived from groups: rec.audio.pro (More info?)

"Jonny Durango" <jonnydurango1BUSH_FROM_OFFICE@comcast.net> wrote in message
news:946dnVGkusyLnmXfRVn-vQ@comcast.com...
> Crest for overall quality or Peavey CS Series for bang/buck performance.

FYI: Peavey has owned Crest for the last 6 years. The story on Peavey's site
says they were initially approached by Crest specifically to outsource
amplifier production, and went from there to a deal to buy the company
outright.

Sean
Anonymous
August 10, 2005 8:44:55 AM

Archived from groups: rec.audio.pro (More info?)

Of the choices you list I have used the QSC RMX2450
in a live band (loud rock) situation. It performed
adequately. It also has built-in limiters (defeatable)
and sub-sonic filters that I like to have available.

drichard wrote:

> I have a pair of Klipsch LaScala speakers left over from my old days as
> a performer that I still consider nice speakers that should meet my
> initial needs for mains. But they have always been a little shy in the
> very deep low end. So I'm thinking that to start off I'll continue to
> use the Klipsch as mains, but add subwoofers to get a stronger bottom
> end, and biamp the system. I've listened to the JBL subwoofers, and
> like them. So my plan right now is to buy a decent power amp and the
> JBL subs, and if necessary, a crossover. To my ears, the Klipsch get a
> little "boxy" (for lack of a better word) sounding around 80 hz or so,
> which is why I thought crossing over at 100-150 hz made sense. I have
> no experience to back that statement up, it just seemed logical to me.
> If more experienced people than I feel that 150 hz is too high to cross
> over, it will negate that advantage for the Crest amp, though are still
> things about it that appealed to me. Are you familiar with the Klipsch
> speakers?

I'd suggest using an adjustable crossover.
If you tune the crossover point (and levels) till it sounds
right you might be surprised at the frequency you end up
with, particularly with the mix of components you describe.
I certainly would want to be able to go below 150.

> Anyway, that's what I'm doing and how I'm going about it, and I'm
> trying to benefit from the experiences of you and the others here to
> make good decisions going forward. I very much appreciate yours and
> Scott's and everyone's feedback. And I'm open to further suggestions.

RMX2450 and Rane AC22 or equivalent.

good luck
rd
Anonymous
August 10, 2005 1:48:03 PM

Archived from groups: rec.audio.pro (More info?)

Hi Graham,

Well, I did a little digging. It seems likely to me that the Crest
Performance series amps are actually the same as Peavey PV series amps,
after all. The Crest CPX2600 is on its own separate "performance
series" website, and bears an uncanny resemblance to the Peavey PV2600
in specs and features.

Dean
Anonymous
August 10, 2005 3:22:28 PM

Archived from groups: rec.audio.pro (More info?)

"Arny Krueger" <arnyk@hotpop.com> wrote in message
news:o 6qdna8i9rtMimTfRVn-qQ@comcast.com...
> "chris berbaum" <qa1090@email.mot.com> wrote in message
> news:D db0hg$kpf$1@avnika.corp.mot.com
> > Hello All,
> >
> > I have a couple of Mackies in the basement (1400i), and
> > they've seemed fine, but I don't ride 'em very hard, ...
> > they don't get moved, etc. Sometimes I think adding amps
> > for monitors, or subwoofs, etc.,.... I always thought I'd
> > just add more Mackies, ... are they not well thought of
> > in the industry (anymore, or ever)? For service, quality,
> > or value? Would they rate with the three mentioned?
> >
>
> My Mackie 1200 was fine until the ribbon cables gave out,
> and its fine now that the ribbon cables are replaced.
>
> At the time I bought it, the 1200 seemed like a lot of amp
> for the price, but now it looks pretty overpriced.
>
>
So, ... what do you like these days? Anyone that stands out from the rest? I
think Mackie has a 2600i now, ... anything up in that range? Thanks for your
thoughts, clb
Anonymous
August 10, 2005 4:22:28 PM

Archived from groups: rec.audio.pro (More info?)

Hi RD,

Thanks for the advice. Between you and the others I've pretty much made
up my mind that I'll need an adjustable crossover.

Dean
Anonymous
August 10, 2005 7:38:17 PM

Archived from groups: rec.audio.pro (More info?)

Pooh Bear <rabbitsfriendsandrelations@hotmail.com> wrote:
>Scott Dorsey wrote:
>>
>> A good rule of thumb is that if the 4 ohm power rating is twice the
>> 8-ohm power rating, you have pretty good output Z. If the 2 ohm
>> power rating is actually twice that, you are doing even better.
>
>To be honest Scott, that spec tells more about the power supply that the
>actual *output impedance*.

It's the same thing! The total output impedance is the impedance of the
power supply, plus the series impedance of the output stage. And yes,
the power supply impedance is the dominant term there.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 10, 2005 7:44:43 PM

Archived from groups: rec.audio.pro (More info?)

"chris berbaum" <qa1090@email.mot.com> wrote in message
news:D dd9k6$rpn$1@avnika.corp.mot.com
> "Arny Krueger" <arnyk@hotpop.com> wrote in message
> news:o 6qdna8i9rtMimTfRVn-qQ@comcast.com...
>> "chris berbaum" <qa1090@email.mot.com> wrote in message
>> news:D db0hg$kpf$1@avnika.corp.mot.com
>>> Hello All,
>>>
>>> I have a couple of Mackies in the basement (1400i), and
>>> they've seemed fine, but I don't ride 'em very hard, ...
>>> they don't get moved, etc. Sometimes I think adding amps
>>> for monitors, or subwoofs, etc.,.... I always thought
>>> I'd just add more Mackies, ... are they not well
>>> thought of in the industry (anymore, or ever)? For
>>> service, quality, or value? Would they rate with the
>>> three mentioned?
>>>
>>
>> My Mackie 1200 was fine until the ribbon cables gave out,
>> and its fine now that the ribbon cables are replaced.
>>
>> At the time I bought it, the 1200 seemed like a lot of
>> amp for the price, but now it looks pretty overpriced.
>>
>>
> So, ... what do you like these days? Anyone that stands
> out from the rest? I think Mackie has a 2600i now, ...
> anything up in that range? Thanks for your thoughts, clb

I also own 3 older QSCs. I'm house poor these days, so if I
needed another amp, it just might be a Behr,
Anonymous
August 10, 2005 8:19:50 PM

Archived from groups: rec.audio.pro (More info?)

"Scott Dorsey" <kludge@panix.com> wrote in message
news:D ddl39$7ch$1@panix2.panix.com
> Pooh Bear <rabbitsfriendsandrelations@hotmail.com> wrote:
>> Scott Dorsey wrote:
>>>
>>> A good rule of thumb is that if the 4 ohm power rating
>>> is twice the 8-ohm power rating, you have pretty good
>>> output Z. If the 2 ohm power rating is actually twice
>>> that, you are doing even better.
>>
>> To be honest Scott, that spec tells more about the power
>> supply that the actual *output impedance*.
>
> It's the same thing! The total output impedance is the
> impedance of the power supply, plus the series impedance
> of the output stage. And yes, the power supply impedance
> is the dominant term there.

Other than oddities like QSC's output stage, the output
impedance of the power supply is usually isolated from the
load by a number of factors. Clarification - I'm talking
about source impedance of the amp, not dynamic range. If the
amp's power supply has a high output impedance, this can
ruin dynamic range.

For one thing if the output stage is the usual big composite
emitter follower, it's high collector impedance isolates the
power supply(s) from the load.

That's one reason why stepped power supplies can work. You
can change the power supply voltage dramatically on the fly,
and as long as there's enough voltage to keep the output
stage well out of saturation, it all works pretty much the
same.

You can put 100 ohm resistors in series with +VCC and -VCC
and while that will mangle the amp's dynamic range, its
output impedance will hardly change. Been there, done that
as a lab experiment.

Secondly, as Graham mentioned, there's the slight matter of
loop feedback. The output impedance of the amp is basically
determined by the source impedance of the output stage
(usually a big composite emitter follower), divided by the
feedback factor.
Anonymous
August 11, 2005 12:04:26 AM

Archived from groups: rec.audio.pro (More info?)

On 10 Aug 2005 15:38:17 -0400, kludge@panix.com (Scott Dorsey) wrote:

>Pooh Bear <rabbitsfriendsandrelations@hotmail.com> wrote:
>>Scott Dorsey wrote:
>>>
>>> A good rule of thumb is that if the 4 ohm power rating is twice the
>>> 8-ohm power rating, you have pretty good output Z. If the 2 ohm
>>> power rating is actually twice that, you are doing even better.
>>
>>To be honest Scott, that spec tells more about the power supply that the
>>actual *output impedance*.
>
>It's the same thing! The total output impedance is the impedance of the
>power supply, plus the series impedance of the output stage. And yes,
>the power supply impedance is the dominant term there.
>--scott

No. The output impedance of the power supply can be just fine. What
the power change with load tells you about is the current delivery
capacity of the supply. That is what makes it sag with lowered load
impedance.

The average amplifier these days has an output impedance of perhaps a
milliohm, so that will cause essentially no power loss at lowered
impedance.

d

Pearce Consulting
http://www.pearce.uk.com
Anonymous
August 11, 2005 12:04:27 AM

Archived from groups: rec.audio.pro (More info?)

Don Pearce <donald@pearce.uk.com> wrote:
>
>No. The output impedance of the power supply can be just fine. What
>the power change with load tells you about is the current delivery
>capacity of the supply. That is what makes it sag with lowered load
>impedance.

Again, how is this different?

>The average amplifier these days has an output impedance of perhaps a
>milliohm, so that will cause essentially no power loss at lowered
>impedance.

It might at 1 KHz, but I bet it doesn't at 10 Hz.... because of the
feedback, the effective series resistance of the output stage might
be zero, but the power supply is still in series with the whole thing
and the impedance of the supply is still nonzero at low frequencies
even though (due to lots of decoupling) it could be very close to zero
at high ones.

These are two ways of looking at the same thing, I think.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 11, 2005 12:04:28 AM

Archived from groups: rec.audio.pro (More info?)

> The average amplifier these days has an output impedance
> of perhaps a milliohm, so that will cause essentially no
> power loss at lowered impedance.

Really?

I own Krells. One of the reasons I bought them was that were among the very
few amplifiers whose output doubled with each having of the load impedance,
down to 2 ohms. (Well, that's what the spec sheet said.)

Try to find an amplifier whose power output varies directly with the load
impedance. You'll have trouble finding any.
Anonymous
August 11, 2005 12:52:54 AM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:

> Pooh Bear <rabbitsfriendsandrelations@hotmail.com> wrote:
> >Scott Dorsey wrote:
> >>
> >> A good rule of thumb is that if the 4 ohm power rating is twice the
> >> 8-ohm power rating, you have pretty good output Z. If the 2 ohm
> >> power rating is actually twice that, you are doing even better.
> >
> >To be honest Scott, that spec tells more about the power supply that the
> >actual *output impedance*.
>
> It's the same thing! The total output impedance is the impedance of the
> power supply, plus the series impedance of the output stage. And yes,
> the power supply impedance is the dominant term there.

I'm afraid you're somewhat mistaken there Scott.

Negative feedback is applied around the amplifier. The output impedance is
determined by the natural output Z of the output stage ( maybe a few 100
milliohms for an emitter follower ) divided by the 'feedback factor'.

It's easy to porove by simply measuring it. Output Z ( reciprocal function of
damping factor ) doesn't rise at LF - and damping factor doesn't fall.

Graham
Anonymous
August 11, 2005 12:56:59 AM

Archived from groups: rec.audio.pro (More info?)

drichard wrote:

> Hi Graham,
>
> Well, I did a little digging. It seems likely to me that the Crest
> Performance series amps are actually the same as Peavey PV series amps,
> after all. The Crest CPX2600 is on its own separate "performance
> series" website, and bears an uncanny resemblance to the Peavey PV2600
> in specs and features.

I figured that may be the case when you said they were on a different
website. In which case they're simply as you say - a rebadge of the PVs.
Good news is that the PVs are better than the old CS series.

We have a PV schematic somewhere. I'll dig it out if I can and scrutinise
the circuitry. I had a quick look once before and it actually didn't look
too bad at a glance.

Graham
Anonymous
August 11, 2005 1:32:33 AM

Archived from groups: rec.audio.pro (More info?)

Pooh Bear <rabbitsfriendsandrelations@hotmail.com> wrote:
>
>It's easy to porove by simply measuring it. Output Z ( reciprocal function of
>damping factor ) doesn't rise at LF - and damping factor doesn't fall.

Output Z does rise at LF, because the power supply capacitors start to
peter out and the power supply impedance rises.

Am I missing something here?
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 11, 2005 2:03:28 AM

Archived from groups: rec.audio.pro (More info?)

"William Sommerwerck" <gizzledgeezer@comcast.net> wrote in
message news:h-OdnYLMeoM3CmffRVn-pg@comcast.com

>> The average amplifier these days has an output impedance
>> of perhaps a milliohm, so that will cause essentially no
>> power loss at lowered impedance.

> Really?

Right, output impedance is always taken at some amount of
output where the amp isn't clipping.

> I own Krells. One of the reasons I bought them was that
> were among the very few amplifiers whose output doubled
> with each having of the load impedance, down to 2 ohms.
> (Well, that's what the spec sheet said.)

You got sold a bill of goods. See below.

> Try to find an amplifier whose power output varies
> directly with the load impedance. You'll have trouble
> finding any.

Including Krells. Actual measurements on Krell amps show
much more than rated output with high-Z loads. IOW they lied
about the output into hi-z loads to make the actual
performance into low-Z loads look better.


The moral of the story is that you want an amp that puts Q
watts into Z ohms then buy one that does that, and forget
about whether or not it puts exactly Q/2 watts into Z*2
ohms.
Anonymous
August 11, 2005 2:03:29 AM

Archived from groups: rec.audio.pro (More info?)

> > Try to find an amplifier whose power output varies
> > directly with the load impedance. You'll have trouble
> > finding any.
>
> Including Krells. Actual measurements on Krell amps show
> much more than rated output with high-Z loads. IOW they lied
> about the output into hi-z loads to make the actual
> performance into low-Z loads look better.

I have no trouble with that. I don't mind lies if they make the amp look
worse than it reaally is.


> The moral of the story is that you want an amp that puts Q
> watts into Z ohms then buy one that does that, and forget
> about whether or not it puts exactly Q/2 watts into Z*2 ohms.

The rationale, however, is that we want an amplifier that looks like a
"perfect" voltage source, as load interaction is once source of differences
in amplifier "sound". (Pace, Arny). Stereophile uses what is supposed to be
a plausible speaker load. I suspect it's downright pathological, because
even expensive sold-state amplifiers (including Krells) show some
interaction with it. What it does to tube amps is downright horrifying.
Anonymous
August 11, 2005 3:00:30 AM

Archived from groups: rec.audio.pro (More info?)

On 9 Aug 2005 09:16:25 -0700, "drichard" <DRichard@wi.rr.com> wrote:

> I need a full-range PA since all
>instruments will go through it.
>
>I have a pair of Klipsch LaScala speakers left over from my old days as
>a performer that I still consider nice speakers that should meet my
>initial needs for mains. But they have always been a little shy in the
>very deep low end.

LaScala's have the same drivers and same horn flare
rates as the Klipsch corner horns, but with the bass
horn chopped off at 2x2 feet and stuck out in free air.

Way back when I owned a pair, I made lightweight
"mouth extenders" that continued the horn somewhat
further into the room. It's okay to use comparatively
flimsy material, even cardboard, to test the idea.

Might be enough for rock band use to minimize the
bare speaker's ringing around 80 Hz and maybe add a
touch of EQ. Price is right, anyway.

Good fortune,

Chris Hornbeck
Anonymous
August 11, 2005 3:45:19 AM

Archived from groups: rec.audio.pro (More info?)

On 10 Aug 2005 18:41:32 -0400, kludge@panix.com (Scott Dorsey) wrote:

>Again, how is this different?

They're talking small signal and you're talking (and
clearly stated in your post) large signal.

Chris Hornbeck
Anonymous
August 11, 2005 4:53:11 AM

Archived from groups: rec.audio.pro (More info?)

Chris Hornbeck wrote:

> On 10 Aug 2005 18:41:32 -0400, kludge@panix.com (Scott Dorsey) wrote:
>
> >Again, how is this different?
>
> They're talking small signal and you're talking (and
> clearly stated in your post) large signal.

There's still more to it than that. The low output Z at LF will still be
there at tens of amps.

It's actually all about circuit design theory ( and practice too ) and
understanding device models.

Graham
Anonymous
August 11, 2005 4:53:12 AM

Archived from groups: rec.audio.pro (More info?)

On Thu, 11 Aug 2005 00:53:11 +0100, Pooh Bear
<rabbitsfriendsandrelations@hotmail.com> wrote:

>> They're talking small signal and you're talking (and
>> clearly stated in your post) large signal.
>
>There's still more to it than that. The low output Z at LF will still be
>there at tens of amps.

Sure, until clipping. That's what Scott posted about.
's all i'm sayin'.

Rock-n-roll,

Chris Hornbeck
!