Mono amp or Bi-amplification

[opus111]

I would love to know how someone copies the sound of a Mundorf silver/gold oil capacitor.

I wouldn't know either - are you of the belief that capacitors somehow add enhancement to the original signal?

 

[RBFC]

Here's an example of active crossovers that can be customized to your specific speaker:

http://www.marchandelec.com

Accessing the connections to the individual drivers is not the "end of the world" in difficulty, as the crossover components are housed in the base of the big B&Ws. I know there is another company that sells external crossovers specifically designed for the B&W Matrix series, and I'll post it if I can find it. There may be simple diagrams that outline how to connect an external crossover on the site too.

Lee

 

[RBFC]

Here's the company, but the external crossovers are merely upgraded passive units. However, you may be able to find out a great deal about the active possibilities from them. Certainly worth a call.

http://www.northcreekmusic.com/801web.html

Lee

 

[microstrip]

I wouldn't know either - are you of the belief that capacitors somehow add enhancement to the original signal?

I know that if I change the type of capacitors in a crossover the sound will change significantly. I am assuming that the designer voiced the speaker for the selected components. IMHO, if someone wants to create his own speaker he should go the DIY way, not modifying expensive speakers.

 

[opus111]

Yes, the B&W guys spend quite some time selecting the right capacitors for their XOs to get the sound they're looking for.(Then purchasing undo all that by looking for a cheaper supplier, but I digress ) But that's not the same thing as thinking a capacitor can add something. My take is they're choosing the caps that subtract the least.

 

[Barry]

There's a thread in the Tech Forum that shows this, IIRC. Been a while since I did it. Bi-amping does not provide more power, unless you use more powerful amps, just better directs the power you have.

I'll try two ways:

1. If you have a single 300 W amp then all drivers get a maximum of 300 W. If you split the signal into two bands, high and low, and use two 300 W amps, then the highs get a max of 300 W and the lows get a max of 300 W as before. Just through different signal paths.

2. Amplifiers look like voltage sources to the speakers. (I'll ignore esoteric design configurations.) The power into a resistive load is P = V^2 / R. A 300 W amp can deliver a certain maximum voltage and thus a certain maximum power (if it has enough current drive ability). If you use two 300 W amps, then the maximum voltage has not changed, and you do not get more power into a given R load. The only way to increase the power is to use a higher-power amp that has more voltage swing.

In practice you might realize a hair more power at clipping if say the LF signal is at clipping and the HF are not since they are usually much lower in amplitude; then when the LF amp clips the HF amp does not. The benefit is minor at best (I would say insignificant in the real world).

HTH - Don

p.s. For me it's a no-brainer if I am not pulling the speaker crossover out: a pair of 600 W mono amps provides 3 dB headroom compared to a pair of 300 W amps on each side.

I'm afraid I'll stick with what Nelson Pass says on this no matter what the Tech Forum says: "Higher power. Typically two amplifiers driving a speaker with an electronic crossover will deliver peak wattages almost 4 times the peak (8 times the rms) wattage rating of a single amplifier of the same power rating. This is because the voltage waveforms coming of the high and low pass filters are not mixed, and the high pass voltage does not ride on top of the low pass voltages. When the waveform of a low frequency approaches the limit of the
amplifier, there is no voltage left over for the high frequency. With an electronic crossover, the available voltage is nearly doubled, and power is quadrupled."

Like Gary I also have a Pass Labs XVR-1-3 (3way). For those bi or tri-amping, you're unlikely to get a decent soundstage without electrically balancing all the outputs (Use a function generator and DMM). There is no way I can come remotely close to DMM-matched results adjusting by ear although maybe you might get lucky. Duelund Cast are the best passive parts rivaling the transparency of an active crossover but they are a bear to break in if you have higher parts values. I used a cable cooker!

 

[c1ferrari]

IMO, the biggest benefit from bi-amping occurs from using an external line-level crossover and connecting the amplifier outputs straight to the drivers, no crossovers in the speaker box. That allows the amplifiers to control the drivers directly, and the crossover allows you to precisely set the crossover frequencies, gain, phase, delay etc. to optimize the speaker's output.

A very enthusiastic...+1

 

[DonH50]

I'm afraid I'll stick with what Nelson Pass says on this no matter what the Tech Forum says: "Higher power. Typically two amplifiers driving a speaker with an electronic crossover will deliver peak wattages almost 4 times the peak (8 times the rms) wattage rating of a single amplifier of the same power rating. This is because the voltage waveforms coming of the high and low pass filters are not mixed, and the high pass voltage does not ride on top of the low pass voltages. When the waveform of a low frequency approaches the limit of the
amplifier, there is no voltage left over for the high frequency. With an electronic crossover, the available voltage is nearly doubled, and power is quadrupled."

Like Gary I also have a Pass Labs XVR-1-3 (3way). For those bi or tri-amping, you're unlikely to get a decent soundstage without electrically balancing all the outputs (Use a function generator and DMM). There is no way I can come remotely close to DMM-matched results adjusting by ear although maybe you might get lucky. Duelund Cast are the best passive parts rivaling the transparency of an active crossover but they are a bear to break in if you have higher parts values. I used a cable cooker!

While I am sure many will be quick to point out I am no Nelson Pass, I respectfully disagree; I do not think the HF signal level is equal to the LF signal in most music etc. That is what the last paragraph of my post describes, but I assumed the HF energy is significantly lower than the LF energy. If they are equal, then his analysis is correct. the lower the crossover, the more likely you are to see power benefits from bi-amping. (This excludes the "passive bi-amping" scheme many AVRs do, since they send a full-range signal to both amps and depend upon the speaker crossover to reject the out-of-band signals.) BUT, you still do not get 600 W anywhere.

There are a couple of typos in that quote. I think peak and RMS are backwards: Vrms = Vpk/sqrt(2) = Vpp/2/sqrt(2) so a given peak voltage yields lower RMS voltage, and there is no such thing as "RMS power".

Marchand makes both active and passive crossovers, even tubed if you like (I had an old ARC tube crossover for a while with my Maggies). On the pro audio side, dbx makes nice inexpensive crossovers in SE and balanced configurations, as does Rane. They also make much more expensive units such as the dbx Driverack (very powerful, programmable, system). Behringer makes several DSP units. Bryston makes a couple of crossovers (one regular, one for subs). On the inexpensive end of DSP-based units are the various miniDSP products. And many DIY kits, in-line passive filters, etc. etc. etc.

 

[microstrip]

As I always calibrate my systems for maximum power, I will add a few personnel comments. Only very exceptionally I reach at any time a voltage over 40% of the maximum allowed RMS voltage of my amplifiers. However for some time I had a Dartzeel system at home and I tried passive bi- amplification. The Dartzeel is even prepared to for tri- amplification, as the preamplifier has three independently low impedance buffered outputs, and uses 50 ohm BNC plugs and cables. The overall gain in sound quality was large, mainly in airiness and the system seemed "faster". If it was not my excessive love for the Audio Research Anniversary and other tube preamplifiers, my current system would probably include three Dartzeel NHB 108s. All IMHO.

 

[DonH50]

I thought on this a little more, and one easy thing to look at are the old Fletcher-Munson loudness curves. If we assume everything else is flat so these curves are the main contributors to power levels in music, then there is a pretty significant range of loudness (perhaps 50 to 120 dB) for which the power at 1 kHz and 200 Hz is roughly the same. There is a dip at 3 kHz or so (meaning we are more sensitive to that frequency, which also happens to be about where a baby's cry occurs) that increases as SPL goes up, and a rise (meaning we are less sensitive) at 100 Hz at below. The LF response keeps rising, and the HF response inflects after about 4 kHz and begins to rise again.

So, if we use a 1 kHz reference, then a typical crossover of perhaps 300 Hz to the woofer means roughly equal power in the woofer and midrange/tweeter amps. If we use 3 kHz, the upper midrange where too loud sounds harsh to most of us, then the upper amp would only use about 1/10th the power of the LF amp.

Bottom line, it depends upon where the crossover is set, and spectrum of music in the mix.

It does not change the fact that bi-amping does not add more power, which is what I said, but does mean there may be more usable power, as Nelson Pass said. As we both imply, and was stated by others, it depends upon how much power is normally required. If you normally only use a few watts, as is pretty common, then bi-amping will not help; it only adds headroom at clipping, and the benefit very much depends upon the source material and crossover point in addition to the usual caveats (power required to deliver desired SPL at the listening position, a function of room size, speakers, etc.)

So the answer is, as happens so often, "it depends".

Passive bi-amping implemented in AVRs does not add any voltage headroom.

I still maintain the biggest benefit in the vast majority of cases is due to better driver (speaker) control that arises from replacing the passive power crossover with a line-level device before the power amps.

FWIWFM - Don

 

[ack]

It does not change the fact that bi-amping does not add more power, which is what I said, but does mean there may be more usable power, as Nelson Pass said. As we both imply, and was stated by others, it depends upon how much power is normally required. If you normally only use a few watts, as is pretty common, then bi-amping will not help; it only adds headroom at clipping, and the benefit very much depends upon the source material and crossover point in addition to the usual caveats (power required to deliver desired SPL at the listening position, a function of room size, speakers, etc.)

I started writing a response when I saw this, and basically I completely agree. Not only do I also think Pass got the RMS vs. Peak claim backwards (or he was perhaps quoted backwards), but the real takeaway is basically the following: When the waveform of a low frequency approaches the limit of the amplifier, there is no voltage left over for the high frequency. Though simplistic, it basically says what we already know and you said: multi-amping adds dynamic headroom, should you need it, not extra power (assuming impedances seen by amplifier(s) do not change from one set-up to another - admittedly, a potentially big assumption).

 

[dcc]

During 14 years, I had an active bi-amped system (Infinity IRS driven by 2 Krell KSA 200s). When I parted with the Infinity, I kept the 2 Krell amps and was able to experience passive bi-amplification with my new loudspeakers. It did not bring more power but it definitely added head-room. The improvement was actually quite substantial. When I retired the KSA 200S, the obvious choice was to take more powerful mono power amplifiers.

 

[Barry]

Read the Pass Labs XVR-1 manual. It's not just about headroom and power. Very insightful for some for the benefits of bi-amping even if, yes, the peak and RMS power is backwards.

http://passlabs.com/manuals/

Rod Elliott's site is also useful for those wanting to learn more or even build something.

http://sound.westhost.com/bi-amp.htm

 

[wes]

Read the Pass Labs XVR-1 manual. It's not just about headroom and power. Very insightful for some for the benefits of bi-amping even if, yes, the peak and RMS power is backwards. http://passlabs.com/manuals/

Rod Elliott's site is also useful for those wanting to learn more or even build something. http://sound.westhost.com/bi-amp.htm

Great but honestly, I don't think I ill mess with the 800D and try to put active crossover by opening the base!

I am not qualified to do so and would worry to do more harm than good, so the question still remain with passive crossover like in the B&W 800Diamond is it worth bi-amping or should I just use a single amp!

 

[DonH50]

@Barry: I agree with the benefits listed in the XVR-1 manual (math typos aside) but wonder about the actual audibility of some of them; it is very amp- and speaker-dependent, and in some cases e.g. changing from 0.1% to 0.01% (or whatever) IMD in the amp is buried in the distortion generated by the speakers themselves.

However, the only thing I addressed in this thread was the power issue.

@wes: As is probably evident I would choose a single amp with twice the power, but the only way to know for sure is to try both ways, with an active crossover before the amps so you actually gain the benefits of improved amp headroom. Do you know the crossover frequency of the hi/lo terminals on the back?

 

[RBFC]

Wes,

If you don't wish to open the crossover on your 800's, then this would be an excellent alternative:

http://bryston.com/products/power_amps/28BSST-2.html

Lee

 

[microstrip]

Great but honestly, I don't think I ill mess with the 800D and try to put active crossover by opening the base!

I am not qualified to do so and would worry to do more harm than good, so the question still remain with passive crossover like in the B&W 800Diamond is it worth bi-amping or should I just use a single amp!

You are a wise man. It seems that the answer to your question will depend a lot on the amplifiers you are considering and the sound levels you usually listen.
Also, as you currently already have one excellent amplifier, I can imagine that there will be also some economic aspects to consider.

 

[wes]

Wes,

If you don't wish to open the crossover on your 800's, then this would be an excellent alternative:

http://bryston.com/products/power_amps/28BSST-2.html

Lee

I currently use Classe CA-M600

 

[wes]

You are a wise man. It seems that the answer to your question will depend a lot on the amplifiers you are considering and the sound levels you usually listen. Also, as you currently already have one excellent amplifier, I can imagine that there will be also some economic aspects to consider.

Thank you, yes i think that messing around with opening up the 800D would not be a wise decision, at least for me!

For movies I would say 95db max except when there are explosion, for music probably 85db if that

 

[AudioExplorations]

I too am interested in this question and still dont feel I have found the answer. Can someone summarize in short, what benefits may be gained from bi-amping assuming leaving the speaker crossovers in place as they are (and you have two sets of binding posts on the speakers).

If an amplification channel is connected only to a tweeter, let's say, will it still work to amplify the mid low frequency signals? Since the downstream (loudspeaker) load is not being driven for low frequencies does this mean the amp does not need to work to amplify this part of the signal?

I have been told that although you will not get more SPL you will get more "slam in the bass" and "slight increase in transparency" (this last one I was told from Herve of DartZeel).