Bi-Amping ESL-9 Classics

[Brewnoser]

I have been bi-amping my Aerius-i's for 20 years. Just replaced them with ESL-9's, Problem is, what worked on the Aerius doesn't seem to be enough on the bass end with these.
I had been running a McIntosh 275, restored original, on the panels, and a restored MC-240 on bass (the 275 just sounds better). The pre-amp is a McIntosh C-2200. The sound was balanced and very enjoyable on the Aerius, but with these I can't get enough volume on the bass end to keep up with the panels. Yet if I run one amp for the entire speakers, with the jumpers on, they sound great. Anyone have any idea what I might need to do to get the balance? I currently have a Bryston 3B (100 wpc @ 8 ohms, more at 4) in there and it almost keeps up, but the panels are still too forward, especially when a full suite of music (band/orchestra and not a solo voice or guitar) is playing. I know I can switch them and run 75 wpc of tube power for ass, but I can't understand why the difference. Again, if I don't bi-amp, the sound is balanced. I know I can always just do that, but I don't understand why this doesn't work.

 

[VideoVic]

Hello! If you read the Classic 9 owner's manual section regarding horizontal biamping, you'll see that M-L recommends both amps have the SAME GAIN. It doesn't matter that the wattages of both amps are close, or even the same.

I ran into a similar situation when attempting to bi-amp my ESL-X speakers. You need to check the MAC and Bryston 3B specs to see how much "GAIN" they each have. It has to be very close, identical is best. Most likely, the gain of both MAC amps is the same, and chances are the Mac just has more gain than the Bryston. My old Rotel only had 22dB of gain compared to my new SANDERS MAGTECH which has 32dB of gain. Huge difference. Couldn't use it to biamp as it would not output the same volume level as the Magtech.
the gain of the amps you want to use isn't the same you might need to find a different amp to drive your 9's woofers, or get an active external crossover device that has adjustable gain outputs to equalize the levels coming out of your two amps.

 

[Brewnoser]

OK, thanks for this (a lot). I am not an electrical engineer (water and dirt is my world). Here are the original specs for my McIntosh amp, I don't know how close the current performance is to them

ELECTRICAL: 75w/ch stereo, 150w mono. Response 16-40kHz (+0 -0.1dB). Distortion 0.5%. Noise & hum -90dB. Output impedance 4, 8, 16, 67 and 600 ohms. 600 ohm center tap internally grounded. (2, 4, 8, 16 and 32 ohms in mono). Output voltages 25V (isolated), 70.7V (one side grounded) and 230V (center tap grounded). Internal impedance less than 10% of rated impedance. Input impedance 250k. Input sensitivity: 0.5V (in mono or twin amp). 2.0V in stereo.

Would the gain be 25V-2V = 23V So (20 * log10(23) = 27dB? (stereo) ?

The MC240 appears to be the same gain if those are the right numbers I used, but less watts.

The 3B I have is old, and I can't find a spec for it yet.

 

[VideoVic]

OK, thanks for this (a lot). I am not an electrical engineer (water and dirt is my world). Here are the original specs for my McIntosh amp, I don't know how close the current performance is to them

ELECTRICAL: 75w/ch stereo, 150w mono. Response 16-40kHz (+0 -0.1dB). Distortion 0.5%. Noise & hum -90dB. Output impedance 4, 8, 16, 67 and 600 ohms. 600 ohm center tap internally grounded. (2, 4, 8, 16 and 32 ohms in mono). Output voltages 25V (isolated), 70.7V (one side grounded) and 230V (center tap grounded). Internal impedance less than 10% of rated impedance. Input impedance 250k. Input sensitivity: 0.5V (in mono or twin amp). 2.0V in stereo.

Would the gain be 25V-2V = 23V So (20 * log10(23) = 27dB? (stereo) ?

The MC240 appears to be the same gain if those are the right numbers I used, but less watts.

The 3B I have is old, and I can't find a spec for it yet.

Glad I was able to help you some, but I have reached the limit of my understanding of amplifiers. I suspect your calculation is probably correct. Maybe another member could step in here to confirm? That being said, I suggest you send email request to both Mac and Bryston customer service asking for the gain spec to be sure. I am certain they can supply those numbers. But the fact remains, unless both amps are within 0.5 dB gain of one another, you'll probably hear an imbalance between the panels and the woofers.

 

[Tmort]

I found a discussion on audiokarma where they calculated the gain of the MC 275 at 26.2 db.

 

[Brewnoser]

I think I can overcome some difference with the gain control on the Bryston, It apparently should have a gain of about 30 db.... But it's the one I want louder...? The gain on the 240 would be similar to the 275 which is why it sounded ok, but it didn't like being run at a higher gain/lower sensitivity.

 

[Tmort]

A google search of the Bryston 3B states that the gain is switchable. At having settings of 23 or 29 db.
So if your bass is lagging it’s probably on the 23 db setting…..try the 29 setting.
I’m running a Magtech on my panels (26 db), and an anthem mca225 mk2 (29 db) on the woofers of my classic 9’s and it sounds great

 

[Brewnoser]

A google search of the Bryston 3B states that the gain is switchable. At having settings of 23 or 29 db.
So if your bass is lagging it’s probably on the 23 db setting…..try the 29 setting.
I’m running a Magtech on my panels (26 db), and an anthem mca225 mk2 (29 db) on the woofers of my classic 9’s and it sounds great

I am hitting the same Google end points as you.

I think what I’m hearing right now is a combination of the speakers still new and a bit bright and the PSvane tubes also being new and a bit bright.

I’m letting it run for a while.

 

[VideoVic]

I think I can overcome some difference with the gain control on the Bryston, It apparently should have a gain of about 30 db.... But it's the one I want louder...? The gain on the 240 would be similar to the 275 which is why it sounded ok, but it didn't like being run at a higher gain/lower sensitivity.

Not sure how to advise you here. Assuming your preamp has identical outputs for both amps, then the Bryston, with approx. 30dB of gain should have provided a sufficient level of output for your 9's woofers to more closely match the level coming from your 9's panels. I don't understand how the woofer level was so far below the panel level. Are you using the same interconnect cables preamp to amp and amp to speaker speaker cables??

 

[Brewnoser]

The connects are same, Preamp has multiple outs. Speaker cables are different, but I've never noticed this issue before. I am thinking that what I am hearing is more related to the panels sounding a bit bright - they are under 50 hours use - and the tubes in the amp also being a bit brighter than I was using before. I may just retube with a lower output tube, from KT88 to 6550. I can always turn the Bryston down. Might even mess with the tone control.

 

[VideoVic]

Good point! The woofers need breaking in too. I think you'll really start to hear them come into their own after 100 hours, so stick with the bi-amping and re-evaluate after you get about 200 hours on them.