Bi-amp option or one single powerful amp

[coolposter]

Hello guys,

I'm running my upgraded Sequel II (SL3 panel and board upgrade by ML) with a Bryston 4B ST. I have been thinking of going for bi-amp for a while. However, it's pretty difficult to find a used 4B ST on the market nowadays. So the option I currently have are:

1, sell my 4B ST, buy a pair of 3B ST or something else, do passive bi-amp.
2, Buy a Bryston 10B active cross over and buy another less powerful amp for woofer (solid state) or a tube for panel while 4B ST drives woofer.
3, Sell 4B ST, get a Sunfire 300X2 or better. Again, Sunfire 300X2 is not too easy to find, except those early models.

Thanks in advance.

 

[Rich]

All three options have their advantages. Depends on what you are looking for out of the upgrade. Personally, I think putting a quality solid state amp (like your Bryston) on the woofers, with a quality tube amp on the panels, will result in some of the best sound you can get out of your older ML speakers.

 

[Spike]

Another option

Hi Coolposter,
How about keeping your Bryston 4B-ST for bass duty if it's working fine and get a good amplifier (preferably tube) for the panels. I've looked into actie bi-amping with the Logans and it came to a deadend. Active bi-amping will work, but requires that you're handy like JonFo and possess the knowledge to bypass the internal crossover circuitry of the Sequel. Assuming the internal crossover remains, adding an active crossover kinda defeats the purpose since you're adding more circuitry upstream which will affect the purity of the signal. In my opinion, I like to keep the component count in the circuit path down to the minimum as much as possible in order to preserve the signal purity. Specifically for the Logans since the internal crossover is considered an integral part of the speakers, it's most straightforward if you passively bi-amp.

Good Luck
Spike

 

[coolposter]

Thanks guys.

If I go tube/SS passive bi-amp route. How do I adjust the balance between tube and SS? What is the correct way to test "imbalance" in the first place?

 

[MrBT]

Thanks guys.

If I go tube/SS passive bi-amp route. How do I adjust the balance between tube and SS? What is the correct way to test "imbalance" in the first place?

That's very good question. I've read recently on this forum people posts about ss/tube combination but what about different voltage gains of different amplifiers? This surely would cause "imbalance".

 

[coolposter]

Found some good tubes on agon:

Conrad Johnson MV45/52/60
Cary CAD 40M

Since both outputs (RCA/XLR) on my Krell can work simultaneously that saves me a pair of Y splits. But then again, there's no level adjustment knob on any of these tubes, nor on my 4B-ST. The woofer -3db switch on speaker is the last resort?

 

[tsv_1]

I've bi-amped in several configurations in the past and it's never really worked out for me. It's not just the potential mismatch in amplifier gain between top and bottom, but also group delays, THD, and other measurable differences that can, when taken as a whole, actually negatively impact the coherency of the musical presentation. Same reason I actually steer clear of bi-wiring. I've just always felt the system was less than fully coherent. Of course that's just the opinion of one guy and his limited sample size of system configs and experimentation... but you did ask for input

Now... having said all that, I know there are lots of folks who are very happy bi-amping, even with wildly different amplifiers top and bottom. To that end, you could (potentially) simply add a fixed attenuator to the inputs of the "hotter" amps. In-line RCA attenuators are fairly easy to come by... here's one on Amazon: http://www.amazon.com/Harrison-Labs-Line-Level-Attenuator/dp/B0006MZN72/ref=pd_bxgy_e_text_c

The other option, if you love breathing solder smoke, like so many of us do, is to make your own attenuators allowing you to dial in the the fixed loss to better match your amps... or go a step further, pull the cover off your amps and throw a resistive voltage divider right there at the input... of course warranty voiding, yadda yadda, fine print, etc.

Or, as Spike eluded to... another potential option is to seek out a good active EQ (and enjoy the ride).

Cheers and good luck with everything,

-Todd


(p.s. oh, and testing for imbalance... best way, although perhaps not the easiest... kinda depends on the crowd you swing with...is to find a buddy who has an oscope and a signal generator... that'd take maybe 5 minutes to determine any drive mismatch. Another way is by ear (yikes) )

 

[coolposter]

(p.s. oh, and testing for imbalance... best way, although perhaps not the easiest... kinda depends on the crowd you swing with...is to find a buddy who has an oscope and a signal generator... that'd take maybe 5 minutes to determine any drive mismatch. Another way is by ear (yikes) )

What about a SPL meter? Here's the idea I have in mind: play test tones in different range, then compare the readings. Say 120hz will/should only come from woofer unit and 1khz will/should only come from panel. Is this good enough?

 

[tsv_1]

What about a SPL meter? Here's the idea I have in mind: play test tones in different range, then compare the readings. Say 120hz will/should only come from woofer unit and 1khz will/should only come from panel. Is this good enough?

theoretically, it should work...if you do the testing in an anechoic chamber... but in your listening environment you likely have room nodes (resonances) that, for example, enhance the bass at the point where you are taking the measurement ... then you have to assume the SPL meter is well calibrated and flat down to the low octaves, etc.

I'd go with a scope if possible. Better yet, drive the entire speaker with one amp

Cheers

oh... another easier route to all this... just choose an amp that has close to the same gain (as listed in the manufacturers specifications) as the one you're already using. This may narrow down your "top amp" choices, but it should at least make the integration process a lot easier. Or, just use one amp to drive the entire speaker... where have I heard that before?

 

[Rich]

You either have to make sure the amp you buy for the panels has the same voltage gain as the amp for the woofers (easiest). . . or you have to purchase an attenuator (basically, an external volume control switch) for one of the amps. Put the attenuator switch onto the amp with the highest voltage gain, and adjust down until it sounds seamless.

 

[coolposter]

You either have to make sure the amp you buy for the panels has the same voltage gain as the amp for the woofers (easiest). . . or you have to purchase an attenuator (basically, an external volume control switch) for one of the amps. Put the attenuator switch onto the amp with the highest voltage gain, and adjust down until it sounds seamless.

Thanks Rich. The 0/-3db switch on my Sequel II works too right?

 

[Rich]

Thanks Rich. The 0/-3db switch on my Sequel II works too right?

That's not really what that switch is for, but it could suffice in some situations. That switch is meant to adjust the bass response in your room to adjust for room effects (such as excessive bass due to the speakers being placed too close to the corners of a room). But if your amps were within 3 db of each other, I suppose you could use that switch to blend them together better. Just try to find a tube amp you like that is within a few db of gain from your Bryston and you should be set.

Otherwise, you will probably want something along the lines of one of these: DACT Audio Attenuators

 

[Bernard]

Otherwise, you will probably want something along the lines of one of these: DACT Audio Attenuators

I cannot say enough about how good the DACT stepped attenuators are. Anyone who has a cheap pot for a volume control should replace it with a DACT. I stated in my system thread that I did just that when the pot in my ARC preamp became noisy. I was astounded at the top to bottom improvement, all for $200.

 

[bud1451]

I too have been thinking about bi-amping my Prodigys, currently using Bryston 7bst in parrallel mode which is about 600 watts into 2ohms. I would like to use the 7bs on the woofers in series (500 watts 8 ohms), does anyone know the ohms on the woofers? Then using a Classe CA-201 on the panels, 400 watts in 4 ohms, 800 into 2 ohms. Thinking this combination would be quite nice at higher volumes, the Bryston does get bright when turned loud, but great bass.

 

[Tj Bassi]

I tried bi-amping a pair of Requests on a few occasions, and none of my attempts gave anything but poor results. To do it correctly you would probably need an outboard crossover and an attenuator as mentioned above. I was always under the impression that the Requests, and likely other models of the same era, would benefit most from a woofer upgrade...bi-amped or not.

Th

 

[Rich]

I got a huge improvement bi-amping my Ascents with a solid state amp on the woofers and a CJ Premier 140 tube amp on the panels. I just used the internal ML crossover (passive biamping) and didn't need an attenuator because my amps' voltage gains were very close. I saw an improvement in sound from top to bottom -- better bass, smoother, more liquid midrange, clearer highs, and much better overall dynamics.

 

[coolposter]

After some research, here's what I can do:

Upgrade my 4B-ST to a Krell, say KSA-250
Or, get a tube, Conrad Johnson MV60/Cary 40M/BAT VK55, etc.

I will let you guys know which option I take. Still debating myself.