[Vipers]

Hi There,
I've been reading this forum for some time now as I've been deciding on which components I need to build my dedicated 2ch system, but this is my first post. Obviously I've decided to build a Bryston system after being blown away by the BCD-1, I've also started a Bryston thread on AVForums in the UK which is the biggest forum of its type in Europe, please feel free to pop over  :-

http://www.avforums.com/forums/audio-processors-power-amps/1205531-bryston-owners-thread.html

I've just taken delivery of a shiny new 17" 4B SST2 and will be getting my BP26MC on Wednesday and having already got the BCD-1 my system is starting to come together nicely, I'm also getting my Michell Orbe turntable next week, but I've got just one quick question.

My Speakers are PMC EB1i's and I've got the opportunity to get another 4B SST2 at a reasonable price and I was wondering would my speakers get any benefit from running 2 x 4B SST's or is 1 more than enough, if 2 4B's are the way to go is bridged or Bi-amping the better option.

I've been getting mixed replies to this question over here, some say 1 x 4B is better as its better to work an amp a little harder to get the best performance from it others have told me more power is always preferable.

Thanks in advance 

[WBimmer]

From my experience with my 28B-SST2, I would say more power and underwork them.

My amps are putting out 1300 watts a piece and I'm probably listening to music at the lowest volumes ever.  With smaller amps and my previous Yamaha RX-Z1, I had to crank it up to feel the music, otherwise it just sounded flat.  Now I can keep the volume low and still get way more feeling from everything I listen to.

Another option would be to pass on the other 4B-SST2 and trade in your 4B-SST2 for a pair of 7B-SST2...  There are definate advantages to mono-blocks...

Wayne.

[adol290]

I had my EB1i's running on a single 4B-SST2. They sounded great, but the EB1i's like lots of power.

I upgraded to 2 X 7BSST2's and what a difference. Better bass and separation of instruments.

If you can afford the 7BSST2's go for it. You will not be disappointed.

[James Tanner]

Hi Vipers,

Welcome!

The only issue when you 'bridge' a stereo amp is the amplifier 'see's' the speaker load at 1/2 the value it does normally.  So 8 ohms becomes 4 ohms and 4 ohms becomes 2 ohms as far as the amplifier is concerned. The amplifier is asked to deliver more current as the impedance of the speaker goes down and at some point may start to current limit or protection circuits cut in.

A lot depends on the type of low impedance load as well because some loads (electrostatics) are very 'reactive' while other loads (typical dynamic speakers) are more beign at low impedances. Also where the low impedance is in the frequency response will be a factor as well in the amps ability to drive the load adequately. 

Long story short if your looking for more 'juice' then the 4B bridged would work fine - if your looking for more 'refinement' in the sound then I would recommend a larger amp per side rather than bridging.

james

[Viajero5000]

Hi Vipers, first of all, I'm sure you'll enjoy your new system; the Bryston/PMC combo is very synergistic. 

With regards to amplification, a 7B or 14B2 amp will definitely be a nice step up from a single 4B, and would probably be preferable to running a pair of bridged 4Bs.  However, this obviously entails selling your brand new amp, which is a hassle after all that effort.

Purchasing a good source/pre-amp and getting room acoustics/speaker positioning right is a better spend than getting a second amp for a passive speaker.  You've already taken care of the first by getting the BCD-1/BP26. However, if (and this is a big if) you have a reasonably sized, acoustically ok room and don't want to swap the 4B for a 7, I would say that adding a second amp as a horizontal (stereo) bi-amp will probably add more resolution, dynamic "bite" and ease to your system's presentation (or so I would like to imagine as far as my own system goes). The theory is that dedicating one amp to the bass will take the load off the second one on the mid/tweet and hence result in lower overall distortion for both amps; however, I'm no scientist at this, it's all hearsay, and passive bi-amping is more of a 'touchy feely' area.  Many PMC owners do seem to prefer bi or tri-amping, so why not get a 3B or 4B on a loaner and judge for yourself?

Let us know how your system comes together; I'm coincidentally also awaiting delivery of my new BP26, and will be happy to play around with bi-amping and let you know my thoughts once i get my system back up and running again. Good luck. 

[Vipers]

Long story short if your looking for more 'juice' then the 4B bridged would work fine - if your looking for more 'refinement' in the sound then I would recommend a larger amp per side rather than bridging.

james

Thanks for the replies so far guys.

So it looks like 2 x 7B's are really the way to go to get the most from my speakers, so maybe I should keep the 4B to get me going and when funds permit move on the 4B to make way for 2 x 7B's.

Hi James, thanks for the reply also, out of interest and taking you're above comment into consideration, if I was to go with 2 x 4B's, would Bi-amping add more refinement compared to Bridging as I'll always choose refinement over out and out power.

[vegasdave]

Hi Vipers,

Welcome!

The only issue when you 'bridge' a stereo amp is the amplifier 'see's' the speaker load at 1/2 the value it does normally.  So 8 ohms becomes 4 ohms and 4 ohms becomes 2 ohms as far as the amplifier is concerned. The amplifier is asked to deliver more current as the impedance of the speaker goes down and at some point may start to current limit or protection circuits cut in.

A lot depends on the type of low impedance load as well because some loads (electrostatics) are very 'reactive' while other loads (typical dynamic speakers) are more beign at low impedances. Also where the low impedance is in the frequency response will be a factor as well in the amps ability to drive the load adequately. 

Long story short if your looking for more 'juice' then the 4B bridged would work fine - if your looking for more 'refinement' in the sound then I would recommend a larger amp per side rather than bridging.

james

So, James, which is better...bi-amping or bridged?

[James Tanner]

I would opt for bi-amping.

james

[vegasdave]

Cool deal. 

[Vipers]

One last question, I take it 2 x 4B SST2's bi-amped would still be inferior to 2 x 7B SST2's?
Thanks.

[vegasdave]

Good question.

[Viajero5000]

One last question, I take it 2 x 4B SST2's bi-amped would still be inferior to 2 x 7B SST2's?
Thanks.

The 7B is a better amp overall and conventional wisdom would probably say yes, but I know at least one forum member who strongly preferred two or three smaller amps wit his PMCs in passive bi/tri-amp mode as opposed to one pair of larger mono-blocks.  Ask your dealer to loan you a 7B and another 4B for audition and let your own ears decide.

[vegasdave]

Good idea. Hopefully I can do that when the time is right.

[Anonamemouse]

One last question, I take it 2 x 4B SST2's bi-amped would still be inferior to 2 x 7B SST2's?
Thanks.

Cool! I actually right now am wearing a t-shirt with your avatar!
Inferior is a very strong word here. There will be a difference in quality. It's more a matter of ÿour wallet agreeing with the price difference" and whether you think the difference in sound is worth the extra money.

[James Tanner]

One last question, I take it 2 x 4B SST2's bi-amped would still be inferior to 2 x 7B SST2's?
Thanks.

It's a tough call on that one Vipers. A lot will have to do with the speaker itself. The ‘quality’ of Bryston amps are all the same so the difference between a 4B and a 7B is more a matter of application rather than performance. Think of it like a car engine – do you need a 4 cylinder or a 6 cylinder – the engine quality is the same but the acceleration and handling required on a specific car will be different.

So if the speaker/amplifier combination has more than enough power to provide for large musical transients then ‘passive’ bi-amping can add some relative performance advantages. If the speaker can benefit from much larger power reserves (believe me those transients take a lot more power than people realize) then the larger single amplifier would be the better option.

Remember too that some speakers are designed to have a simpler circuit path if used in a bi-amp/tri-amp mode because you connect directly to each section of the internal passive crossover/driver so again it may be a better option given a specific speaker. Check with the speaker manufacture to see if the circuit path changes when bi-amping or tri-amping.

Hope this helps

james

[vegasdave]

So, you would have to try both and see?

[Viajero5000]

 Check with the speaker manufacture to see if the circuit path changes when bi-amping or tri-amping.

I'd be interested in knowing what PMC's advice is on this.  During a casual conversation, a PMC staff member recommended tri-amping, while during another chat a PMC rep suggested using the larger mono-blocks.  However I've never formally asked PMC this question.

[Vipers]

 Check with the speaker manufacture to see if the circuit path changes when bi-amping or tri-amping.

Hope this helps

james

Thanks for the input again guys, PMC are fairly local to me, only about 10miles away, I'll try and give them a bell this week to see direct from the horses mouth whether bi-amping would be benificial.

[Vipers]

Cool! I actually right now am wearing a t-shirt with your avatar!

Its a small world Its a hang over from when I had my Hennessay Viper, sold it to start my own business, that was a sad day.

[Vipers]

Another quick question guys, if I decide to go with this other 4B and Bi-amp, the only problem is that it comes with a 19" faceplate and my new 4B has a 17", is it easy for me to swap over and has anyone got any idea of cost for a new 17" faceplate in the UK?