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Bi-Amp question

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Anonymous
December 23, 2004 8:07:35 AM

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

I have a Technics SA-DX1040 5.1 receiver/amp that has bi-amp capability.
Should I be able to use this function across two different pairs of
speakers, or will it only work properly with a single pair designed for
bi-amp operation? I currently have a pair of LX5 bookshelf speakers with
ribbon tweeters and a pair of large floor standing speakers with 15"
woofers. I would like to send the HF to the LX5s and the LF to the floor
speakers. When I wire it accordingly and put the amp in bi-amp mode I get
greatly reduced volume and very poor sound. Its almost like I have the HF
and LF swapped, but I know I wired it right. Should the commons (grounds)
be wired together? I haven't pushed much power through it this way because
it's obviously not right and I don't want to break anything. It's also
obvious that I don't know what I'm doing! Any advice would be appreciated.

Alan Chapman

More about : amp question

Anonymous
December 23, 2004 12:08:52 PM

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

In <rosyd.2080$i11.608493@twister.southeast.rr.com>, on 12/23/04
at 05:07 AM, "Alan Chapman" <achapman@nc.rr.com> said:

>I have a Technics SA-DX1040 5.1 receiver/amp that has bi-amp

I'm not familiar with your unit, but I have not encountered a home
theater unit claiming to offer "bi-amp", however, I can imagine a
contorted method of strapping some of the ZONE2 capabilities (if your
unit has them) to accomplish this. Having "A" and "B" front speaker
switching is not bi-amping. If you have pre-out and main-in patching on
your unit, you could brew up bi-amping for simple stereo by re-patching
the rear amplifiers to run the upper or lower frequency speakers.

>capability. Should I be able to use this function across two different
>pairs of speakers, or will it only work properly with a single pair
>designed for bi-amp operation? I currently have a pair of LX5
>bookshelf speakers with ribbon tweeters and a pair of large floor
>standing speakers with 15" woofers. I would like to send the HF to
>the LX5s and the LF to the floor speakers. When I wire it accordingly
>and put the amp in bi-amp mode I get greatly reduced volume and very
>poor sound. Its almost like I have the HF and LF swapped, but I know
>I wired it right. Should the commons (grounds) be wired together? I
>haven't pushed much power through it this way because it's obviously
>not right and I don't want to break anything. It's also obvious that
>I don't know what I'm doing! Any advice would be appreciated.

Rather than bi-amp, I suspect that the speakers are wired in series.
You can easily prove or disprove this by disconnecting *ONE* speaker.
If both this speaker and it's bi-amp mate are muted, they are wired in
series and you are not bi-amping.

Another possibility, if you are interpreting the "A" and "B" speaker
switches as bi-amp and the speakers are switched in parallel, is that
the impedance the amplifier sees is a bit too low and it is balking.

Other issues:

Have you strapped the speakers to use only the woofer in the LF
speakers and only the tweeter/mid section of the LX5s? Have you
provided for level matching of the two different speakers? Do you have
the correct crossover frequency set on the Receiver?

-----------------------------------------------------------
spam: uce@ftc.gov
wordgame:123(abc):<14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15
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-----------------------------------------------------------
Anonymous
December 23, 2004 8:28:42 PM

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

In <MrHyd.11$aM4.10594@twister.southeast.rr.com>, on 12/23/04
at 10:15 PM, "Alan Chapman" <achapman@nc.rr.com> said:

[ ... ]

>I've been informed that I should be using the term Bi-Wire, instead of
>Bi-Amp (even though my amp does have a "Bi-Amp" light that comes on
>when I push the Bi-Wire switch. I also probably muddied the water by
>saying it was a 5.1 receiver (which it is) because the Bi-Wire/Bi-Amp
>function is only available when in stereo mode.

There are two definitions of bi-amp floating around. "Bi-amp" implies
two amplifiers per audio channel. The old definition includes a filter
ahead of each amplifier to limit the frequencies presented for
amplification. Cleverly, we choose the filters to compliment the
speakers. The new definition simply splits the signal with a "Y" cable
and each amplifier operates over the entire frequency range.
Crossovers, if any, are the domain of the loudspeakers.

I like the results gained by the old method. I'm not a fan of the new
method.

>There are A and B speaker outs for the front L & R channels, they can
>either be used as separate pairs (A or B or both simultaneously) like
>a typical amp and in this way both A & B carry full range sound.
>Alternatively one can switch to bi-wire mode and the A R&L output is
>supposed to be HF, the B R&L output LF, as printed on the back at the
>speaker terminals.

>>
>> >capability. Should I be able to use this function across two different
>> >pairs of speakers, or will it only work properly with a single pair
>> >designed for bi-amp operation? I currently have a pair of LX5
>> >bookshelf speakers with ribbon tweeters and a pair of large floor
>> >standing speakers with 15" woofers. I would like to send the HF to
>> >the LX5s and the LF to the floor speakers. When I wire it accordingly
>> >and put the amp in bi-amp mode I get greatly reduced volume and very
>> >poor sound. Its almost like I have the HF and LF swapped, but I know
>> >I wired it right. Should the commons (grounds) be wired together? I
>> >haven't pushed much power through it this way because it's obviously
>> >not right and I don't want to break anything. It's also obvious that
>> >I don't know what I'm doing! Any advice would be appreciated.
>>
>> Rather than bi-amp, I suspect that the speakers are wired in series.
>> You can easily prove or disprove this by disconnecting *ONE* speaker.
>> If both this speaker and it's bi-amp mate are muted, they are wired in
>> series and you are not bi-amping.

[ ... ]



>There is no provision for selecting the crossover frequency.

That's odd because the amplifier manufacturer can't know the optimum
crossover frequency for your unique situation.

>An external crossover shouldn't be necessary because the amp is already
>separating the freqs, its just not adjustable. I'm thinking that by
>applying the HF and LF bi-wired outputs to two full range speaker
>pairs then who cares if the tweeters on one pair get nothing and the
>woofers on the other pair get nothing, the best parts of the
>respective pairs (i.e. ribbon tweeters on the LX5s and 15" woofers on
>the others) are what are being driven.

There is some merit in that approach ... if the choice of crossover
frequency was lucky. Is there a way of adjusting the low and high
frequency levels to match the efficiencies of your speakers?

>Problem is, it just sounds
>very low level when I do it, like most of the power is going to waste
>or like there is an impedance mismatch somewhere. The unit also has a
>"Low IMP" mode but both pairs are 8ohms so that shouldn't be necessary
>and I haven't tried it.

As a quick check, switch back to the multi-channel mode and work with
the A and B speaker outputs. Is everything OK if you use A or B, or A
and B?

There could be some level trims that are set too low.

----

Check your owner's manual to make sure that you are using the bi-amp
mode correctly. It is possible that a receiver menu option is clouding
the issue. Consider that only the low frequency effects are being
routed to the LF output. If that is true, then you would not have the
lows from a stereo source routed to the LF channel. Setting the main
speakers to "small" on the surround sound menu may help.

The level trims for the LF and HF sections may be on the surround
menus.

-----------------------------------------------------------
spam: uce@ftc.gov
wordgame:123(abc):<14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15
13> (Barry Mann)
[sorry about the puzzle, spammers are ruining my mailbox]
-----------------------------------------------------------
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Anonymous
December 24, 2004 1:15:08 AM

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

Thanks for your reply.

"Barry Mann" <zzzz@zzzz.zzz> wrote in message
news:41cad5d8$1$avgroveq$mr2ice@wcnews.cyberonic.com...
> In <rosyd.2080$i11.608493@twister.southeast.rr.com>, on 12/23/04
> at 05:07 AM, "Alan Chapman" <achapman@nc.rr.com> said:
>
> >I have a Technics SA-DX1040 5.1 receiver/amp that has bi-amp
>
> I'm not familiar with your unit, but I have not encountered a home
> theater unit claiming to offer "bi-amp", however, I can imagine a
> contorted method of strapping some of the ZONE2 capabilities (if your
> unit has them) to accomplish this. Having "A" and "B" front speaker
> switching is not bi-amping. If you have pre-out and main-in patching on
> your unit, you could brew up bi-amping for simple stereo by re-patching
> the rear amplifiers to run the upper or lower frequency speakers.

I've been informed that I should be using the term Bi-Wire, instead of
Bi-Amp (even though my amp does have a "Bi-Amp" light that comes on when I
push the Bi-Wire switch. I also probably muddied the water by saying it
was a 5.1 receiver (which it is) because the Bi-Wire/Bi-Amp function is only
available when in stereo mode.

There are A and B speaker outs for the front L & R channels, they can either
be used as separate pairs (A or B or both simultaneously) like a typical amp
and in this way both A & B carry full range sound. Alternatively one can
switch to bi-wire mode and the A R&L output is supposed to be HF, the B R&L
output LF, as printed on the back at the speaker terminals.

>
> >capability. Should I be able to use this function across two different
> >pairs of speakers, or will it only work properly with a single pair
> >designed for bi-amp operation? I currently have a pair of LX5
> >bookshelf speakers with ribbon tweeters and a pair of large floor
> >standing speakers with 15" woofers. I would like to send the HF to
> >the LX5s and the LF to the floor speakers. When I wire it accordingly
> >and put the amp in bi-amp mode I get greatly reduced volume and very
> >poor sound. Its almost like I have the HF and LF swapped, but I know
> >I wired it right. Should the commons (grounds) be wired together? I
> >haven't pushed much power through it this way because it's obviously
> >not right and I don't want to break anything. It's also obvious that
> >I don't know what I'm doing! Any advice would be appreciated.
>
> Rather than bi-amp, I suspect that the speakers are wired in series.
> You can easily prove or disprove this by disconnecting *ONE* speaker.
> If both this speaker and it's bi-amp mate are muted, they are wired in
> series and you are not bi-amping.

I'll have to try that.

>
> Another possibility, if you are interpreting the "A" and "B" speaker
> switches as bi-amp and the speakers are switched in parallel, is that
> the impedance the amplifier sees is a bit too low and it is balking.
>

> Other issues:
>
> Have you strapped the speakers to use only the woofer in the LF
> speakers and only the tweeter/mid section of the LX5s? Have you
> provided for level matching of the two different speakers? Do you have
> the correct crossover frequency set on the Receiver?

There is no provision for selecting the crossover frequency. An external
crossover shouldn't be necessary because the amp is already separating the
freqs, its just not adjustable. I'm thinking that by applying the HF and LF
bi-wired outputs to two full range speaker pairs then who cares if the
tweeters on one pair get nothing and the woofers on the other pair get
nothing, the best parts of the respective pairs (i.e. ribbon tweeters on the
LX5s and 15" woofers on the others) are what are being driven. Problem is,
it just sounds very low level when I do it, like most of the power is going
to waste or like there is an impedance mismatch somewhere. The unit also
has a "Low IMP" mode but both pairs are 8ohms so that shouldn't be necessary
and I haven't tried it.

Thanks again for your reply.

Alan


>
> -----------------------------------------------------------
> spam: uce@ftc.gov
> wordgame:123(abc):<14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15
> 13> (Barry Mann)
> [sorry about the puzzle, spammers are ruining my mailbox]
> -----------------------------------------------------------
>
Anonymous
December 28, 2004 1:18:02 AM

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

The first thing is to get the service manual and look first at the test
procedure, if one is there, which will give you a good idea as to what
is going on. The block diagram is also very helpful, if present.

"Bi-amp" means that the signal is separated for LF and HF ahead of the
amplifiers. "Bi-wire" is the same signal going to different posts that
are otherwise strapped: it's really a gimmick.

If all else fails, we get out Mr. Audio Generator and Mr. Voltmeter.
A PC sound card and cable will probably do for this.
!