Adding an external power amplifier

[dlaloum]

Thanks again. I've heard bi-amping is much more effective than bi-wiring. Also my av10 allows for BTL, which is how I have my fronts wired. Thoughts?

BTL basically exposes the speakers to the amp at half the impedance - so an 8ohm speaker then presents as a 4ohm speaker - so the amp needs to be able to handle the impedance presented (not usually an issue for an 8ohm speaker, but if the speaker is 4ohm, then you will be asking the amp to drive a 2ohm load - many amps won't be happy with that!)

If your speakers want mostly Volts rather than Amps... BTL will give you double the power, double the Volts....

The Impedance / Frequency chart is measured & presented for the earlier 702s2 here:

Bowers & Wilkins 702 S2 loudspeaker Measurements

Sidebar 3: Measurements

www.stereophile.com

It shows the impedance dropping at around 120Hz and 7khz to circa 3ohm...

When running in BTL mode, that is effectively 1.5 ohm - lots of amps won't do well into such loads

If the amp is fine into 2 ohm or 1 ohm loads then that will not be a problem - most amps don't do well in that situation!

I have a pair of amps that do fine with 1 ohm loads, and I tried them in BTL mode... but in my setup, it made absolutely no difference, so I put them back into normal mode.

 

[highfigh]

Thanks again. I've heard bi-amping is much more effective than bi-wiring. Also my av10 allows for BTL, which is how I have my fronts wired. Thoughts?

How do you mean 'bi-amping', passive or active? Active bi-amplification is more efficient since the input and output levels can be set for unity gain, passive filters have insertion loss.

IMO, your speakers are the limiting factor in the SPL, not your amplification but I would still ask- How loud do you need it to play and are you operating at an extreme SPL on average, or for peaks?

The answers to those questions are part of what's included in system design. Until they're defined, you won't find the solution to your perceived problems.

 

[philly]

BTL basically exposes the speakers to the amp at half the impedance - so an 8ohm speaker then presents as a 4ohm speaker - so the amp needs to be able to handle the impedance presented (not usually an issue for an 8ohm speaker, but if the speaker is 4ohm, then you will be asking the amp to drive a 2ohm load - many amps won't be happy with that!)

If your speakers want mostly Volts rather than Amps... BTL will give you double the power, double the Volts....

The Impedance / Frequency chart is measured & presented for the earlier 702s2 here:

Bowers & Wilkins 702 S2 loudspeaker Measurements

Sidebar 3: Measurements

www.stereophile.com

It shows the impedance dropping at around 120Hz and 7khz to circa 3ohm...

When running in BTL mode, that is effectively 1.5 ohm - lots of amps won't do well into such loads

If the amp is fine into 2 ohm or 1 ohm loads then that will not be a problem - most amps don't do well in that situation!

I have a pair of amps that do fine with 1 ohm loads, and I tried them in BTL mode... but in my setup, it made absolutely no difference, so I put them back into normal mode.

Just to clarify my fronts are B&W 702s3 if that matters

 

[everettT]

Just to clarify my fronts are B&W 702s3 if that matters

Your speakers dip very low and through the difficult part of the power band FYI.

 

[philly]

Your speakers dip very low and through the difficult part of the power band FYI.

So that's a good or a bad thing with my amp10? Lol

 

[everettT]

So that's a good or a bad thing with my amp10? Lol

It demands a lot of the amplifier already, and if your amp isn't designed for lower than 4 ohm in bridged tie mode, I personally wouldn't bother. It's easier just to size the amp correctly and move on. At low level it will be fine, above that I wouldn't.

Bi-amping isn't much better than passive bi-wiring, you still have to deal with the passive crossover. I will note, however, there are some speakers that it would be a benefit to, but the majority, not. Active crossovers are where bi-amping will provide the best results. Marketing gets people all the time.

 

[philly]

Yeah sorry I'm definitely not as knowledgeable as you guys are with this technical stuff! But I'm learning. I guess I'm confused as to how the resistance varies up and down, and whether it's a speaker and/or amp thing? Mine are rated at 8ohms.

Also someone said above that your speakers might need voltage or wattage. I thought they all used wattage, how would I know?

 

[philly]

It demands a lot of the amplifier already, and if your amp isn't designed for lower than 4 ohm in bridged tie mode, I personally wouldn't bother. It's easier just to size the amp correctly and move on. At low level it will be fine, above that I wouldn't.

Bi-amping isn't much better than passive bi-wiring, you still have to deal with the passive crossover. I will note, however, there are some speakers that it would be a benefit to, but the majority, not. Active crossovers are where bi-amping will provide the best results. Marketing gets people all the time.

Yes I have heard biwiring is useless. but the tech that helped me set up my room and the rep at B&W said biamping is beneficial in that it sends a separate channel to the high and mid and a separate channel to the woofer. So more efficient. I'm not sure if this is true but like I said mine is set to BTL. There's so many articles, reviews, vids, and recommendations on my amp10 and av10 as well as the av10 336 page manual lol, that it's kind of confusing what to think are the best connections?!

 

[everettT]

Yes I have heard biwiring is useless. but the tech that helped me set up my room and the rep at B&W said biamping is beneficial in that it sends a separate channel to the high and mid and a separate channel to the woofer. So more efficient. I'm not sure if this is true but like I said mine is set to BTL. There's so many articles, reviews, vids, and recommendations on my amp10 and av10 as well as the av10 336 page manual lol, that it's kind of confusing what to think are the best connections?!

The short and skinny is that in your particular case, there is no benefit. The power, whether a single amp channel or two combined, the signal still has to go through the passive crossover power divide. In this hobby, active bi-amping should be considered the only bi-amping option and in your case, isn't possible.

 

[philly]

The short and skinny is that in your particular case, there is no benefit. The power, whether a single amp channel or two combined, the signal still has to go through the passive crossover power divide. In this hobby, active bi-amping should be considered the only bi-amping option and in your case, isn't possible.

Ok sorry to keep asking questions for understanding you don't have to answer if you don't feel like it! Lol. but how do I set the crossover and how do I know if my biamping is active or passive??

 

[lovinthehd]

@philly do you have a sub? Is the AV10 your pre-pro?

 

[philly]

@philly do you have a sub? Is the AV10 your pre-pro?

Yes I have two Martin Logan 1100X Dynamo Subs. the av-10 is my processor, the amp10 is my amp. I have a 5.2.2 configuration, with the floors in btl wired mode.

 

[lovinthehd]

Yes I have two Martin Logan 1100X Dynamo Subs. the av-10 is my processor, the amp10 is my amp. I have a 5.2.2 configuration, with the floors in btl wired mode.

So you run the speakers full range, never set up a crossover? Did you run Audyssey to do initial setup? Do you use the LFE or LFE+Main mode for the speakers' bass mode?

 

[philly]

So you run the speakers full range, never set up a crossover? Did you run Audyssey to do initial setup? Do you use the LFE or LFE+Main mode for the speakers' bass mode?

No I don't run them as large. My crossover is set at 80 HZ and I have it set for LFE + Main. yes I did run Arc, but the levels all seemed too low.

 

[lovinthehd]

No I don't run them as large. My crossover is set at 80 HZ and I have it set for LFE + Main. yes I did run Arc, but the levels all seemed too low.

Not much point to LFE+Main if running the speakers as small (small just means use bass management, i.e. redirecting bass from speakers to the sub). 80hz is a decent crossover most of the time but I'd experiment higher and lower as well. ARC as in Anthem Room Correction on a Marantz? Or Audyssey? What seemed low about levels?

 

[everettT]

Ok sorry to keep asking questions for understanding you don't have to answer if you don't feel like it! Lol. but how do I set the crossover and how do I know if my biamping is active or passive??

You're passive bi-amping because the crossovers are in your speakers, passively post amplification. Active is when the crossovers would be in the digital domain prior to amplification.

 

[lovinthehd]

You're passive bi-amping because the crossovers are in your speakers, passively post amplification. Active is when the crossovers would be in the digital domain prior to amplification.

Altho to be fair if using subs it could be considered active bi-amping between speakers and subs....

 

[philly]

I ran

Not much point to LFE+Main if running the speakers as small (small just means use bass management, i.e. redirecting bass from speakers to the sub). 80hz is a decent crossover most of the time but I'd experiment higher and lower as well. ARC as in Anthem Room Correction on a Marantz? Or Audyssey? What seemed low about levels?

Audyssey on the preamp, arc on the subs. Still confused about the lfe setting.

 

[lovinthehd]

I ran

Audyssey on the preamp, arc on the subs. Still confused about the lfe setting.

LFE setting means use bass management between subs and speakers and setting a crossover point in between (keep in mind a crossover is a crossing over of a low pass filter slope (for subs) and a high pass filter slope (for speakers). LFE+Main setting enables you to run fronts full range and still redirect bass to sub instead of limiting it in the fronts (and the crossover acts as half crossover in this case, just low pass for sub). I forgot your subs have their own setup (and I'd generally run that on the subs first, then incorporate everything with an Audyssey run after that). Are you using the Audyssey MultEQ Editor or the MultEQ-X apps?

 

[lovinthehd]

Still curious what you felt was "low" from the auto setup particularly.