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High power inductor

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June 10, 2004 8:43:42 AM

Archived from groups: rec.audio.high-end (More info?)

Hi all,

I'm doing some crossover calculations for my 4-way, 2000 watt speakers
that I'm planning on building and of course the first roadblock is the
very large physical size of the inductor coils that will be necessary
to split the sub and the mid-bass at 300 Hz. I would very much
appreciate some advice on how to create a 12 mH inductor in the
smallest amount of space possible, and still can safely handle about
1500 watts. I've seen different types of cores that can be used to
reduce the number of windings but I've also heard of the various
acoustical drawbacks to having non-air cores, and so I'm hoping that
there's an alternative out there. Anybody have some ideas?

thanks in advance,
Sean

More about : high power inductor

Anonymous
June 11, 2004 5:08:57 AM

Archived from groups: rec.audio.high-end (More info?)

"Sean" <delphiconsultingguy@yahoo.com> wrote in message
news:2GRxc.74236$Ly.52521@attbi_s01...
> Hi all,
>
> I'm doing some crossover calculations for my 4-way, 2000 watt speakers
> that I'm planning on building and of course the first roadblock is the
> very large physical size of the inductor coils that will be necessary
> to split the sub and the mid-bass at 300 Hz.

First off, I'd be curious as to why you would cross a sub at such a high
frequency. 100Hz or lower is more common. In a 3 way system 300 Hz would
be about right, but not IMO, for a subwoofer.

I would very much
> appreciate some advice on how to create a 12 mH inductor in the
> smallest amount of space possible, and still can safely handle about
> 1500 watts. I've seen different types of cores that can be used to
> reduce the number of windings but I've also heard of the various
> acoustical drawbacks to having non-air cores, and so I'm hoping that
> there's an alternative out there. Anybody have some ideas?
>
You can pick up a copy of AudioXpress and check the ads for custom winding,
or do what I beleive is more practical and go to Adire Audio's web site and
check out their subwoofer amps. www.adireaudio.com .
They offer several amps for sub use and 2 in particular that should meet
your needs quite well, the HS 500 at 750Watts at 4 ohms for $629.00 or the
HS 1400 with 1400 Watts for $899.00. They both have electronic xovers and
therefore eliminate the need for inductors of any size.

> thanks in advance,
> Sean
>
Your welcome.
June 11, 2004 5:20:02 AM

Archived from groups: rec.audio.high-end (More info?)

> I'm doing some crossover calculations for my 4-way, 2000 watt speakers
> that I'm planning on building and of course the first roadblock is the
> very large physical size of the inductor coils that will be necessary
> to split the sub and the mid-bass at 300 Hz. I would very much
> appreciate some advice on how to create a 12 mH inductor in the
> smallest amount of space possible, and still can safely handle about
> 1500 watts. I've seen different types of cores that can be used to
> reduce the number of windings but I've also heard of the various
> acoustical drawbacks to having non-air cores, and so I'm hoping that
> there's an alternative out there. Anybody have some ideas?
> thanks in advance,
> Sean

Use active filter and separate amplifiers. It is a bloody waste of energy
to use passive networks with such powers. What is more, your sound will
improve dramatically.
Grtx, Wendy
Related resources
Anonymous
June 11, 2004 8:17:50 AM

Archived from groups: rec.audio.high-end (More info?)

On 6/10/04 12:43 AM, in article 2GRxc.74236$Ly.52521@attbi_s01, "Sean"
<delphiconsultingguy@yahoo.com> wrote:

> Hi all,
>
> I'm doing some crossover calculations for my 4-way, 2000 watt speakers
> that I'm planning on building and of course the first roadblock is the
> very large physical size of the inductor coils that will be necessary
> to split the sub and the mid-bass at 300 Hz. I would very much
> appreciate some advice on how to create a 12 mH inductor in the
> smallest amount of space possible, and still can safely handle about
> 1500 watts. I've seen different types of cores that can be used to
> reduce the number of windings but I've also heard of the various
> acoustical drawbacks to having non-air cores, and so I'm hoping that
> there's an alternative out there. Anybody have some ideas?

Large fans? If you are planning on running that amount of power - the coil
is likely to get really hot - making a fan work much better.
Anonymous
June 11, 2004 4:56:54 PM

Archived from groups: rec.audio.high-end (More info?)

"Sean" <delphiconsultingguy@yahoo.com> wrote in message
news:2GRxc.74236$Ly.52521@attbi_s01...
> Hi all,
>
> I'm doing some crossover calculations for my 4-way, 2000 watt speakers
> that I'm planning on building and of course the first roadblock is the
> very large physical size of the inductor coils that will be necessary
> to split the sub and the mid-bass at 300 Hz. I would very much
> appreciate some advice on how to create a 12 mH inductor in the
> smallest amount of space possible, and still can safely handle about
> 1500 watts. I've seen different types of cores that can be used to
> reduce the number of windings but I've also heard of the various
> acoustical drawbacks to having non-air cores, and so I'm hoping that
> there's an alternative out there. Anybody have some ideas?

With that kind of power, ferrite cores will saturate like crazy. An air core
is possible but it will be huge, and I don't think any are made that big
commercially. 12 mH transformer cored inductors are readily available and
they might be your best bet. I'd suggest you have a word with a manufacturer
of transformer cored inductors regarding power handling. You might be lucky.

Stephen
June 12, 2004 3:46:12 AM

Archived from groups: rec.audio.high-end (More info?)

Hi all again,

I appreciate all the advice so far but I'm hell-bent on making a
passive crossover for this setup. If someone can please tell me how
to get the highest inductance possible in the smallest space possible,
or perhaps suggest a completely different mechanism for adding
inductance to a circuit, I'd be most grateful.

thanks again,
Sean
Anonymous
June 12, 2004 8:57:01 PM

Archived from groups: rec.audio.high-end (More info?)

Sean,

I'm not sure where you are getting the 1500 Watt figure for the
inductor power handling. If it needs to handle that much power, your
speaker cables may melt long before the inductor is bothered. Let's
assume an inductor with a DC resistance (DCR) of 0.75 Ohms (i.e., at
low frequencies). If it must handle 1500 Watts, this equates to a
current through the inductor of:

square root (1500 / 0.75) = about 45 Amps

If that power is being consumed by the inductor, then your speaker
cable needs to pass that current on to the inductor.

I suggest looking at this another way. Let's assume that the 12 mH
inductor you've described will be in series with your low frequency
driver, perhaps as part of a 2nd order LC filter (especially since any
inductor in the high frequency driver path should very likely be of
much smaller value). Now start with your low frequency loudspeaker
driver, which you intend to feed 2000 Watts (I assume peak). If it's
an 8 Ohm driver, the maximum current requirement for the driver would be:

square root (2000 / 8) = about 16 Amps

and the maximum voltage across the driver would be:

square root (2000 x 8) = about 130 Volts

Thus at low frequencies, you'll have at most 16 Amps flowing through
your speaker cables and through any in-line (i.e., in series)
inductor. And with a music signal, the average signal power level
will be much lower:

- about 10x lower for rock music (200 Watts, 5 Amps, 40 Volts)
- about 30x lower for jazz (75 Watts, 3 Amps, 25 Volts)
- about 50x lower for classical (40 Watts, 2.2 Amps, 18 Volts).

At 0 Hz an inductor with 0.75 DCR in series with an 8 Ohm loudspeaker
driver need handle only:

16 x 16 x 0.75 = about 200 Watts

At a crossover frequency of 300 Hz, the inductive reactance of the 12
mH inductor will be:

2 x pi x 300 x 0.012 = 22.6 Ohms

and, ignoring any capacitor for now, the impedance of the inductor-low
freq driver leg as seen by the amplifier will now be:

22.6 + 8.0 = 30.6 Ohms

with a maximum current flow of:

130 Volts / 30.6 Ohms = 4.25 Amps

giving an inductor power requirement of:

4.25 x 4.25 x 22.6 = about 410 Watts

These are peak power levels. As noted above, your average power
levels will be 10-50x lower depending on the type of music. This does
not seem to be a particularly onerous requirement as long as you pay
attention to saturation issues at peak power. Potential sources:

http://www.alphacore.com/inductor.htm [12 GA, foil, air core - they
can probably make a custom 12 mH inductor for you, but it will be
large, expensive and heavy]

http://www.madisound.com/inductors.html [15 GA, permeable steel core -
they don't say what the power handling is on these before saturation,
but you can call and ask; if it's under 450 Watts you can always buy 4
of their 12 mH inductors, connect two each in parallel, then connect
the two parallel sets in series for an equivalent 12 mH inductor with
4x the power handling capability]

If you are looking for a maxed out solution at reasonable cost, you
can go with the second choice here and use the suggested 4 inductors
per side in a series-parallel connection for lots of headroom before
saturation - cheap at $65.00 per equivalent inductor, and likely able
to handle a full 1500 Watts or better with ease. This would probably
cost you 1/3 of the equivalent AlphaCore air core inductor, be much
lighter, have half the DCR, and have a smaller footprint.

Best regards,

Terry

Sean wrote:
>
> Hi all,
>
> I'm doing some crossover calculations for my 4-way, 2000 watt speakers
> that I'm planning on building and of course the first roadblock is the
> very large physical size of the inductor coils that will be necessary
> to split the sub and the mid-bass at 300 Hz. I would very much
> appreciate some advice on how to create a 12 mH inductor in the
> smallest amount of space possible, and still can safely handle about
> 1500 watts. I've seen different types of cores that can be used to
> reduce the number of windings but I've also heard of the various
> acoustical drawbacks to having non-air cores, and so I'm hoping that
> there's an alternative out there. Anybody have some ideas?
>
> thanks in advance,
> Sean
Anonymous
June 12, 2004 8:57:42 PM

Archived from groups: rec.audio.high-end (More info?)

"Sean" <delphiconsultingguy@yahoo.com> wrote in message
news:cadg8404v6@news3.newsguy.com...
> Hi all again,
>
> I appreciate all the advice so far but I'm hell-bent on making a
> passive crossover for this setup. If someone can please tell me how
> to get the highest inductance possible in the smallest space possible,
> or perhaps suggest a completely different mechanism for adding
> inductance to a circuit, I'd be most grateful.
>
> thanks again,
> Sean

As I said before, pick up a copy of audio and check the ads, or check with
the DIY places like Madisound, Speaker City, and Zalytron.
If they can't help you directly, they will know who can.

Now, lets assume you get what you want, this is going to be a stand alone
sub or part of a single box system? Maybe something like one of the side
fire models? If it's going to be stand alone, why 300 Hz? Free standing
subs are useful because they can be positioned for best flat response. To
do that they need low crossover points, lower than 300 Hz.

I'm very curious as an sometime DIYer why that crossover point, particularly
if it's a free standing sub.
June 12, 2004 8:58:39 PM

Archived from groups: rec.audio.high-end (More info?)

Sean wrote:
> Hi all again,
>
> I appreciate all the advice so far but I'm hell-bent on making a
> passive crossover for this setup. If someone can please tell me how
> to get the highest inductance possible in the smallest space possible,
> or perhaps suggest a completely different mechanism for adding
> inductance to a circuit, I'd be most grateful.
>
> thanks again,
> Sean

Sean,
your approach and the level of your understanding guarantees an acoustical
desaster with these speakers. You have to take in account the
interdependence of your speaker and the xover components. The loudspeaker
resonance will alter the desired characteristic or has to be compensated.
The baffle size will strongly influence the radiation in the midrange. All
this can be calculated and simulated. I suggest the very good simulation
software Akabak. To operate this software will require a steep learning
curve.

A coil is just that- a wire wound many times in a circle. If you use air
core, which means there is no saturation with higher current and the
inductivity will stay constant, you need a lot of turns. since this is the
case you have to use a big diameter wire. There is no trade off with space
and cost. If you want a 12mH choke, the cost for a ready made unit will be
around 200 bucks for the amount of current (20Arms with 4R speakers). There
are ways to make crossovers to use only 1 coil both for the highpass and
lowpass. But again simulation will be needed to find the right values.
The midrange will need a lowpass and a highpass in series. Both will
influence each other and additionally interact with the speaker impedance.
Only a lengthy simulation can find the optimal values.
Another problem will be the capacitors. Forget about electolytics, this
amount of power needs a lot of paralleled MKT foil capacitors, I have here a
47uF/160V in the size of a coffee mug, and you will need a couple of them.
If you do a 3-way xover you will need at least 500 bucks in parts and
lengthy simulation and measuring.
The loudspeaker measuring hard- and software will be pricey and it will take
a long time to get reasonable results. I want to encourage you though to go
this way, it is satisfying to learn and understand this matter when you like
music.
--
ciao Ban
Bordighera, Italy
http://www.pupazzo.page.ms/
Anonymous
June 13, 2004 5:47:48 PM

Archived from groups: rec.audio.high-end (More info?)

On Thu, 10 Jun 2004 04:43:42 GMT, delphiconsultingguy@yahoo.com (Sean)
wrote:

>Hi all,
>
>I'm doing some crossover calculations for my 4-way, 2000 watt speakers
>that I'm planning on building and of course the first roadblock is the
>very large physical size of the inductor coils that will be necessary
>to split the sub and the mid-bass at 300 Hz. I would very much
>appreciate some advice on how to create a 12 mH inductor in the
>smallest amount of space possible, and still can safely handle about
>1500 watts. I've seen different types of cores that can be used to
>reduce the number of windings but I've also heard of the various
>acoustical drawbacks to having non-air cores, and so I'm hoping that
>there's an alternative out there. Anybody have some ideas?
>
>thanks in advance,
>Sean

OK, here goes:
inductance in uH is: (.315 * r * r * N * N)/(6r + 9l +10d)
r is radius in cm
N is # of turns
l is length of coil (cm)
d is depth of winding (cm)

let's use 5 cm for radius, 10 cm for length, 1 cm for depth (this is a
guesstimate). Set inductance to 12000 (in uH), solve for N. I get 89
turns (which is not all that bad)!.
Now take the 89 turns, convert it to legth (89 * 2pi * r), convert
to feet, and I got 91.7 feet. Resistance for 91 ft is:
14 AWG: .23 ohms
12 AWG .14 ohms
10 AWG .09 ohms

Assume your current is 20 amps (that is a grossly high estimate,
because it assumes you are running the amp flat out). I also assume
your speaker resistance is about 4 ohms. Power dissipated by the coil
would be:

14 AWG: about 90w
12 AWG: 60w

10 AWG: 37w not too bad for the size of coil, but give it
room to dissipate heat. My guess is that it
would run 60-100 degrees Celcius. There isn't much
to happen if it gets too hot, as long as it doesn't char or catch
something on fire. By that time your voice coil will be flaming!

Since you seldom run a speaker flat out (what do think would happen
to your voice coil with 1500 watts across it for 20-30 sec.), you
could assume a current of, say 10 amps, then because power is
proportional to current squared, you could reduce the above powers by
4.
The inductor is not all that atrocious. Due to the high powers
involved, I'd recommend some form of sustained overcurrent protection.
If you DID put 20 amps continuous into this system, there are
possibilities of fire! Use a coil form that is not flammable (and not
metallic). I would also put a breaker on the power amp, on the 110 or
220 volt supply, and have it trip at say, 500 W. That way the amp can
deliver its peak powers without problem but will trip if the sustained
power exceeds 500 W (which is going to sound pretty rough, because of
the limited headroom).

-Paul
................................................................
Paul Guy
Somewhere in the Nova Scotia fog
Anonymous
June 13, 2004 8:42:23 PM

Archived from groups: rec.audio.high-end (More info?)

Keep in mind that the room will also have an effect on the speaker's
impedance. I had good results before by building the speakers first, putting
them in place, measuring what I ended up with and then designing the
crossover. Something no manufacturer can give you.


"Ban" <bansuri@web.de> wrote in message
news:3DGyc.32803$HG.2253@attbi_s53...
> Sean wrote:
> > Hi all again,
> >
> > I appreciate all the advice so far but I'm hell-bent on making a
> > passive crossover for this setup. If someone can please tell me how
> > to get the highest inductance possible in the smallest space possible,
> > or perhaps suggest a completely different mechanism for adding
> > inductance to a circuit, I'd be most grateful.
> >
> > thanks again,
> > Sean
>
> Sean,
> your approach and the level of your understanding guarantees an acoustical
> desaster with these speakers. You have to take in account the
> interdependence of your speaker and the xover components. The loudspeaker
> resonance will alter the desired characteristic or has to be compensated.
> The baffle size will strongly influence the radiation in the midrange. All
> this can be calculated and simulated. I suggest the very good simulation
> software Akabak. To operate this software will require a steep learning
> curve.
>
> A coil is just that- a wire wound many times in a circle. If you use air
> core, which means there is no saturation with higher current and the
> inductivity will stay constant, you need a lot of turns. since this is the
> case you have to use a big diameter wire. There is no trade off with space
> and cost. If you want a 12mH choke, the cost for a ready made unit will be
> around 200 bucks for the amount of current (20Arms with 4R speakers).
There
> are ways to make crossovers to use only 1 coil both for the highpass and
> lowpass. But again simulation will be needed to find the right values.
> The midrange will need a lowpass and a highpass in series. Both will
> influence each other and additionally interact with the speaker impedance.
> Only a lengthy simulation can find the optimal values.
> Another problem will be the capacitors. Forget about electolytics, this
> amount of power needs a lot of paralleled MKT foil capacitors, I have here
a
> 47uF/160V in the size of a coffee mug, and you will need a couple of them.
> If you do a 3-way xover you will need at least 500 bucks in parts and
> lengthy simulation and measuring.
> The loudspeaker measuring hard- and software will be pricey and it will
take
> a long time to get reasonable results. I want to encourage you though to
go
> this way, it is satisfying to learn and understand this matter when you
like
> music.
> --
> ciao Ban
> Bordighera, Italy
> http://www.pupazzo.page.ms/
>
Anonymous
June 14, 2004 8:03:33 PM

Archived from groups: rec.audio.high-end (More info?)

High power inductor -- one of the critical elements of switch mode power
supply design is specification of the inductors -- if you can get it there
is a 2-part series of article in the amateur radio experimenter magazine
"QEX" (probably at a university library) -- Sept/Oct 2002 and Jan/Feb 2003
which goes through the math and core selection. You want to select a
material which won't saturate at the current you are pumpling thought. The
QEX series of articles explains the heat transfer which has to be dealt with
in coil design -- of course the problem is that at such high current the
wire size becomes problematic.

A good source for ferrite and iron core toroids is Amidon, Inc.
www.amidoncorp.com

"Sean" <delphiconsultingguy@yahoo.com> wrote in message
news:2GRxc.74236$Ly.52521@attbi_s01...
> Hi all,
>
> I'm doing some crossover calculations for my 4-way, 2000 watt speakers
> that I'm planning on building and of course the first roadblock is the
> very large physical size of the inductor coils that will be necessary
> to split the sub and the mid-bass at 300 Hz. I would very much
> appreciate some advice on how to create a 12 mH inductor in the
> smallest amount of space possible, and still can safely handle about
> 1500 watts. I've seen different types of cores that can be used to
> reduce the number of windings but I've also heard of the various
> acoustical drawbacks to having non-air cores, and so I'm hoping that
> there's an alternative out there. Anybody have some ideas?
>
> thanks in advance,
> Sean
>
June 15, 2004 2:16:11 AM

Archived from groups: rec.audio.high-end (More info?)

> If it's going to be stand alone, why 300 Hz?

Hi Michael, I chose 300 Hz because my subwoofer is faithful to 500 and
my woofer is faithful down to 70, so I chose the happy medium in the
middle such that the power distribution is biased to the big speaker.
The final product I'm shooting for will be a pair of 4-way speakers
with the mid and tweeter being satellites (separate enclosure). Most
of the time though they will operate as a single stacked unit.
Anybody else feel I should lower the sub crossover point?

Ban, Thanks for the software recommendations, though I wouldn't mind
hearing from other people on this forum about how much I really have
to gain from this approach. I'm not looking for perfectly faithful
speakers in terms of intrinsic flatness (my apologies to audiophiles
out there), I'm merely looking to have a very, very loud set of
speakers that I don't mind digitally eq'ing the heck out of to flatten
the signal. In this light, the simulator and the accompanying
learning curve may be overkill.

Stephen, I did some research about cored inductors and found a lot of
information about transformers and inductors but I'm not sure if
there's some hybrid that you're specifically mentioning here.

Terry, I like the alphacores and will probably be pursuing that route
for my inductance needs. Your suggestion about parallel-serializing 4
small inductors seems only impractical in the sense that they still
individually need to be 12 mH each, meaning that there would be 4 very
large coils instead of 1 super-large one, but I think the super-large
one would still be smaller in net volume than the other 4 combined.
Not to mention $$$. I'm hoping that alphacore will be able to help me
out with a super-coil. Thanks for the links!

Sean
Anonymous
June 15, 2004 7:04:17 AM

Archived from groups: rec.audio.high-end (More info?)

On Sat, 12 Jun 2004 16:57:01 GMT, Zagar <openskyseven@comcast.net>
wrote:

>Sean,
>
........some stuff deleted.....


>
>At a crossover frequency of 300 Hz, the inductive reactance of the 12
>mH inductor will be:
>
> 2 x pi x 300 x 0.012 = 22.6 Ohms
>
>and, ignoring any capacitor for now, the impedance of the inductor-low
>freq driver leg as seen by the amplifier will now be:
>
> 22.6 + 8.0 = 30.6 Ohms
>
>with a maximum current flow of:
>
> 130 Volts / 30.6 Ohms = 4.25 Amps
>
>giving an inductor power requirement of:
>
> 4.25 x 4.25 x 22.6 = about 410 Watts
>

You cannot calculate dissipated power of an inductor by multiplying
its impedance by the current squared. The power dissipated by an
inductor (ignoring iron and eddy losses) is simply the current squared
times the DC RESISTANCE of the coil.
It is true that there is a power (stored energy) associated with
the reactive element (2*pi*f*L), but it does not release as heat, it
is released back into the circuit itself.
You can have an enormous reactive power, and yet get no heat. If I
place a good (oil) capacitor across 110 volts, I can draw several
amps, yet the capacitor will dissipate no heat. That is because the
current and voltage are 90 degrees out of phase - the product averages
out to zero.

I'd find it easier to use air coils, simply because there are
accurate formulae to determine the inductance, you don't need a
difficult core, and you never need to worry about saturation,
hysterisis, losses etc. It might use a few pounds of copper, but you
could always make a "pancake" style coil which would easily fit
against the inside of the cabinet. Once you have a large diameter
coil, it does not take a lot of turns to make up a high inductance.
However, you DO need a fair length of wire.
I'm assuming you did your homework and have determined the proper
crossover frequency, phase response, etc., for a smooth transition
with minimal phase or directional artifacts. I have pretty limited
familiarity with crossover technology, but it does not seem all that
simple. It is not as simple as determining impedance at crossover,
since you need to remember that both speakers are active at crossover,
and they have their own phase shifts, along with the fact that they
are separated by a distance that will cause effects at the listeners
position. If my memory serves me... you want a 4th order Linkowitz
network???? or something like that. I believe John Vanderkooy or/and
Stan Lipschitz from Waterloo did a fair bit of work with this. Dick
could probably fill you in with the relevant theory and history.

-Paul

................................................................
Paul Guy
Somewhere in the Nova Scotia fog
Anonymous
June 16, 2004 4:09:46 AM

Archived from groups: rec.audio.high-end (More info?)

Keep in mind that the room will also have an effect on the speaker's
impedance. I had good results before by building the speakers first, putting
them in place, measuring what I ended up with and then designing the
crossover. Something no manufacturer can give you.

"Sean" <delphiconsultingguy@yahoo.com> wrote in message
news:Lspzc.35982$eu.12652@attbi_s02...
> > If it's going to be stand alone, why 300 Hz?
>
> Hi Michael, I chose 300 Hz because my subwoofer is faithful to 500 and
> my woofer is faithful down to 70, so I chose the happy medium in the
> middle such that the power distribution is biased to the big speaker.
> The final product I'm shooting for will be a pair of 4-way speakers
> with the mid and tweeter being satellites (separate enclosure). Most
> of the time though they will operate as a single stacked unit.
> Anybody else feel I should lower the sub crossover point?
>
> Ban, Thanks for the software recommendations, though I wouldn't mind
> hearing from other people on this forum about how much I really have
> to gain from this approach. I'm not looking for perfectly faithful
> speakers in terms of intrinsic flatness (my apologies to audiophiles
> out there), I'm merely looking to have a very, very loud set of
> speakers that I don't mind digitally eq'ing the heck out of to flatten
> the signal. In this light, the simulator and the accompanying
> learning curve may be overkill.
>
> Stephen, I did some research about cored inductors and found a lot of
> information about transformers and inductors but I'm not sure if
> there's some hybrid that you're specifically mentioning here.
>
> Terry, I like the alphacores and will probably be pursuing that route
> for my inductance needs. Your suggestion about parallel-serializing 4
> small inductors seems only impractical in the sense that they still
> individually need to be 12 mH each, meaning that there would be 4 very
> large coils instead of 1 super-large one, but I think the super-large
> one would still be smaller in net volume than the other 4 combined.
> Not to mention $$$. I'm hoping that alphacore will be able to help me
> out with a super-coil. Thanks for the links!
>
> Sean
>
Anonymous
June 16, 2004 7:03:34 AM

Archived from groups: rec.audio.high-end (More info?)

"Sean" <delphiconsultingguy@yahoo.com> wrote in message
news:Lspzc.35982$eu.12652@attbi_s02...
> > If it's going to be stand alone, why 300 Hz?
>
> Hi Michael, I chose 300 Hz because my subwoofer is faithful to 500 and
> my woofer is faithful down to 70, so I chose the happy medium in the
> middle such that the power distribution is biased to the big speaker.
> The final product I'm shooting for will be a pair of 4-way speakers
> with the mid and tweeter being satellites (separate enclosure). Most
> of the time though they will operate as a single stacked unit.
> Anybody else feel I should lower the sub crossover point?
>

A xover at 300 Hz does not IMO qualify as a subwoofer. A driver with an f3
of 70 Hz doesn't either.

A crossover at 300 hz should be to something like a midrange of about 5.5".

I think a 4 way may be overkill, but would very likely work well if the sub
is a real one crossed at 100 Hz or lower from a driver that can't go down to
20 Hz.

Eq is fine, but you need to consider excursion limits. A good 12'' sub like
the Adire Shiva can move a lot of air with bottoming out and play loud as
hell, without EQ. A lesser woofer, may blow itself out out it's voicecoil
if it isn't built for big xmax.

> Ban, Thanks for the software recommendations, though I wouldn't mind
> hearing from other people on this forum about how much I really have
> to gain from this approach. I'm not looking for perfectly faithful
> speakers in terms of intrinsic flatness (my apologies to audiophiles
> out there), I'm merely looking to have a very, very loud set of
> speakers that I don't mind digitally eq'ing the heck out of to flatten
> the signal. In this light, the simulator and the accompanying
> learning curve may be overkill.
>
> Stephen, I did some research about cored inductors and found a lot of
> information about transformers and inductors but I'm not sure if
> there's some hybrid that you're specifically mentioning here.
>
> Terry, I like the alphacores and will probably be pursuing that route
> for my inductance needs. Your suggestion about parallel-serializing 4
> small inductors seems only impractical in the sense that they still
> individually need to be 12 mH each, meaning that there would be 4 very
> large coils instead of 1 super-large one, but I think the super-large
> one would still be smaller in net volume than the other 4 combined.
> Not to mention $$$. I'm hoping that alphacore will be able to help me
> out with a super-coil. Thanks for the links!
>
> Sean
>
Anonymous
June 19, 2004 6:35:15 PM

Archived from groups: rec.audio.high-end (More info?)

Paul Guy wrote:
>
> On Sat, 12 Jun 2004 16:57:01 GMT, Zagar <openskyseven@comcast.net>
> wrote:
>
> >Sean,
> >
> .......some stuff deleted.....
>
> >
> >At a crossover frequency of 300 Hz, the inductive reactance of the 12
> >mH inductor will be:
> >
> > 2 x pi x 300 x 0.012 = 22.6 Ohms
> >
> >and, ignoring any capacitor for now, the impedance of the inductor-low
> >freq driver leg as seen by the amplifier will now be:
> >
> > 22.6 + 8.0 = 30.6 Ohms
> >
> >with a maximum current flow of:
> >
> > 130 Volts / 30.6 Ohms = 4.25 Amps
> >
> >giving an inductor power requirement of:
> >
> > 4.25 x 4.25 x 22.6 = about 410 Watts
> >
>
> You cannot calculate dissipated power of an inductor by multiplying
> its impedance by the current squared. The power dissipated by an
> inductor (ignoring iron and eddy losses) is simply the current squared
> times the DC RESISTANCE of the coil.
> It is true that there is a power (stored energy) associated with
> the reactive element (2*pi*f*L), but it does not release as heat, it
> is released back into the circuit itself.

Thanks for pointing this out. The sources I've read to date have
really not delved into this, but had led me to believe that the
reactance values could be used in the power formula when dealing with
a 2-port component. I'd appreciate any reference you can provide here
for my future use.

> You can have an enormous reactive power, and yet get no heat. If I
> place a good (oil) capacitor across 110 volts, I can draw several
> amps, yet the capacitor will dissipate no heat. That is because the
> current and voltage are 90 degrees out of phase - the product averages
> out to zero.

With an AC signal, I agree that it averages to zero, but I was trying
to deal with worst case peak values to make a point to Sean. If there
are two sine waves 90 degrees out of phase, at regular intervals their
product will have an absolute peak value of 0.5 (=0.707 x 0.707),
which would have put my 300 Hz calculation off by a factor of 2 too high.

Best regards,

Terry
!