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Subwoofer to lighten load on ESL 63

G

gustavm

pfm Member
I was thinking of getting some elderly ESL63s restored, and as a longer-term possibility, thinking about building a pair of open-baffle sub-woofers to use with them. Motivation for this is not so much to increase the bass output, but to relieve the ESLs of some of the low-frequency energy, to give them more headroom.

So - I was thinking along the lines of an active system where the ESL power amplifier is fed via a high-pass filter (maybe fc = ~150-200Hz, 12dB/octave) while the sub-woofer is fed via a DSP system with a response derived via microphone measurement.

What I'm not sure of though, is how much this would really help. I wouldn't want to move fc to a much higher frequency because this would probably spoil the extreme clarity and coherence of the ESLs.


How does the peak excursion of a driver unit fall off as the high-pass cut-off is increased?

Anyone any quantitative knowledge of this?

Thanks in advance......
 
I can only say that my stock 63s are not missing anything I can hear in my room and system. Mine are lifted 25cm or so above ground and tilted backwards - I always wondered what raising them another 10-15cm would do, but I am not unsatisfied as-is and wonder what additional sound quality is possible if source and amp are up to the job. What Problem exactly are you trying to solve?

Richard
 
gustavm said:
How does the peak excursion of a driver unit fall off as the high-pass cut-off is increased?
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An acoustic roll-off of 12 dB/octave will maintain a constant displacement. This is usually not a good idea because you will be hearing the distortion from high displacement in the rolled-off frequency region without the benefit of any significant output. A higher acoustic roll-off would be normally used.
 
Dowser said:
I can only say that my stock 63s are not missing anything I can hear in my room and system. Mine are lifted 25cm or so above ground and tilted backwards - I always wondered what raising them another 10-15cm would do, but I am not unsatisfied as-is and wonder what additional sound quality is possible if source and amp are up to the job. What Problem exactly are you trying to solve?

Richard
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It depends what kind of music you listen to, and at what level. I listen almost entirely to classical music, of all types. It is well know that classical orchestral music and opera can have a very large dynamic range, so listening at realistic levels, I slightly fear damage to the ESLs. (Someone on another forum reported blowing one panel on the opening to the 5th Movement of Mahler's 10th symphony - which features a series of isolated thwaks on the bass drum).

Hence the objective I described above - to maintain a realistic sound level while trying to relieve the ESLs of some of the LF duty.
 
I run ESL63s with diy Gradient clone subs, which I added for much the same reasons that you mention. When my Quads were serviced by One Thing Audio before I added the subs I mentioned my plans to them and their thoughts were roughly the same as Dowser’s. After adding the subs I did notice a little more deep bass on certain orchestral pieces and movies (they do TV duty too) but no noticeable increase in overall level handling. Recently I sold one of the two amps I was using and connected the ESLs back up as full range units. I was a little distressed to find that I preferred the SQ that way. Obviously that was not the correct answer, so I am now considering a DSP solution. It’s low priority at the moment, though.
 
Did you connect the Quads via a high-pass filter?

This is just a whimsical thought at the moment, not a definite. I am hopeful my ESL63s will maybe improve anyway after a service - they date back to early 1980's and one has a pronounced "sizzle", so the panels are probably not giving of their best.

I've seen mixed reports of both OneThing and Quad, but I've decided to go to Quad for the service (actually full re-build).
 
I use(d) this active crossover.

I’m happy with OTA, they replaced all eight panels in mine soon after I bought them. I hate to think when that was, must be 12 years, and all is still fine.
 
Its not DIY but i have been using the most recent Gradient subs (the sw-s) with their combined crossover /amp that has 4 channels of Hypex NCORE power at 240W each. The crossover is set at 110Hz. The subs are an open baffle design - 2x12 inch drivers per channel. To my ears the sound feels completely strain free at the top and bottom end. The bass goes a LOT lower too. The downside (after weeks of listening) is that the mid range doesn't sound quite as lifelike as before (without the subs and using EAR 509s). Fortunately the crossover has a line level out for the mids and highs so i can use the EARs together with the Hypex power for the bass. Haven't tried that yet but will do shortly.
 
gustavm said:
Did you connect the Quads via a high-pass filter?

This is just a whimsical thought at the moment, not a definite. I am hopeful my ESL63s will maybe improve anyway after a service - they date back to early 1980's and one has a pronounced "sizzle", so the panels are probably not giving of their best.

I've seen mixed reports of both OneThing and Quad, but I've decided to go to Quad for the service (actually full re-build).
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Have you removed socks and grills to look at panels yet? Probably worth doing, glue fails at right/left edges of stators allowing them to flap about. Simple reglueling, if you get it early enough, will get rid of sizzle. There’s a thread here somewhere with photos of how i fixed mine.
 
And if not, ask Quad for the original panels back...I’ll give you £50 for them :) Basically, Quad will fit new panels, but they’re fixable if caught early enough!
 
gustavm said:
I've seen mixed reports of both OneThing and Quad, but I've decided to go to Quad for the service (actually full re-build).
Click to expand...

I bought my 989's because they had been fully serviced by Quad.

Though as I found Quad only replace the panels that have failed.

When adhesive failure starts it eventually affects all the panels.
 
I asked for replacement of all panels + protection circuitry + caps. So the quote should cover all of that (except they said its only the caps on the EHT board that give problems and they will check rather than replace).

I think I'd rather just replace the lot, but in their quote the labour cost is limited to a certain amount per speaker, so I guess they avoid doing anything they think is unnecessary.
 
FWIW I've been using ESL63s and their 'children' for 30+ years with >200Wpc amps. And also modified a QUAD 33's bass lift to extent the LF. Never had a problem with the drive levels. Point being that in reality the peak levels I need are well below what would reach the speaker's spec limits, but sounds loud enough.

So I'd suggest before deciding that you get a scope or a peak-reading meter or something like that and monitor the actual peak levels you are putting into the speakers.

Also, do you know what issue board they are? The protection system varied. (Although if you're replacing them I assume it would become the last issue?)
 
I think it would be a great idea, although I would suggest getting a DSP crossover so you can play with steep slopes. Fourth order is my goto slope, and with bass crossovers it can make sense to go steeper.
 
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