Beyma CP21F match for Beyma TPL150H

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#31 Re: Beyma CP21F match for Beyma TPL150H

Post by Toppsy »

The Bass may become its own independent build, so that it could be used to work with the ESL 57's.
John,
If you are intending to use those large 15" bass drivers to use with your 57's the only possible speaker configuration that could keep pace with the ESL panels would be a isobaric type speaker or similar configuration design. Based on my own experience OB configuration simply will not be able to keep pace with the ESL panels. I know from bitter experience of many attempts to get a conventional sealed box sub woofer and OB bass driver to work with my 57's without success. The slower moving cones of the conventional speaker simply lagged behind the lightning fastness of the ESL panels and there was always noticeable timing issues I never resolved. You may have better luck. If you decide to go this way with the bass drivers it would be worth you researching isobaric speaker design. Other folk that have experimented with trying to get a conventional bass driver to fully integrate successfully with a ESL speaker may be able to advise to better. I know Martin Logan use a cone bass with their ESL panels but those that I have heard all suffer to some degree this timing lag issue.
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#32 Re: Beyma CP21F match for Beyma TPL150H

Post by chris661 »

Colin, I'm curious - why would isobaric drivers help?

I'd be really interested to try making a bass module for some ESLs - I think it'd need some work in terms of processing, but I see no particular reason it can't be done.

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#33 Re: Beyma CP21F match for Beyma TPL150H

Post by ed »

chris661 wrote: Mon Dec 02, 2019 8:10 am Colin, I'm curious - why would isobaric drivers help?

I'd be really interested to try making a bass module for some ESLs - I think it'd need some work in terms of processing, but I see no particular reason it can't be done.

Chris
I've thought about this for more than a long time....and all I could come up with was the idea that it would involve something like the quad delay system. Instead of aiming for the point source solution try delaying the whole panel to align with a bass driver. I'm not sure how ML do it but as Colin has mentioned, it's not a complete solution, not to my ears anyway.
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#34 Re: Beyma CP21F match for Beyma TPL150H

Post by Toppsy »

chris661 wrote: Mon Dec 02, 2019 8:10 am Colin, I'm curious - why would isobaric drivers help?

I'd be really interested to try making a bass module for some ESLs - I think it'd need some work in terms of processing, but I see no particular reason it can't be done.

Chris
Chris,
I seem to remember seeing a hifi magazine article (may even had been published in Klang+Ton?) where they had designed and built a isobaric woofer to go underneath some quad ESL's, firing at 90-deg to the ESL's. I think they were 63's. If my failing memory serves they reported this went a long way to sorting the timing issue. I can only think it may be that the isobaric driver arrangement gave a dipole response more in keeping with the ESL panels? Must admit though that I never tried it as I had moved on from ESL speakers by then. You also have to remember that at that time there was not digital processing available. that today may address the issue. But John is wanting to do his designs using passive XO'ers.
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#35 Re: Beyma CP21F match for Beyma TPL150H

Post by pre65 »

There was a DIY design for a Quad compatible subwoofer in an old Hi-fi World DIY supplement, from Noel Keywood if memory serves.

Our Greg may remember more, and possibly have a copy of the article ?
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#36 Re: Beyma CP21F match for Beyma TPL150H

Post by JohnG »

A option on the table for the Bass Section, before expensive cap,s are purchased, is to connect the Bass to a available Panel Amp, so they will have their own power source and frequency adjustment.
This is new to me, but I am reading it as a type of active sub woofer.
I remember NoelKeywoid covering the Gradient Dipole Bass for a ESL 63, I also know a rarer design was done for 57,s.
I have many of the HFW Diy supplements from the 90's. I can have a search too.
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#37 Re: Beyma CP21F match for Beyma TPL150H

Post by Ali Tait »

Delay could be accomplished with a miniDSP unit very easily, a cheap way of trying it.
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#38 Re: Beyma CP21F match for Beyma TPL150H

Post by Scottmoose »

I suspect what Colin's referring to is the Celestion SL6000 & the various DIY variations thereof. Actively EQ'd ripole variations in effect with twin drivers mounted front-to-front. Per channel, obviously.

Not that I imagine anyone gives two hoots, assuming you select a sealed box with a Qtc of 0.5 ('transient perfect') then that's as 'fast' as it gets in the LF itself, although a very low tuned EBS vented box (as in tuned to infrasonics: 20Hz doesn't cut it) runs that quite close in terms of overhang or lack thereof in the majority of the bass range. The price is typically large size, so as Colin alludes to, isobaric loading is a good way of achieving either of these while keeping size in check as far as possible.

I don't pretend to be up on the subject as ESLs aren't my forte, but my assumption has always been that the issue with blending subs to ESL mains is that

1/ The selected load for the LF units has excessive overhang: as far as I can see, many appear to be stuffed into quite small volumes in order to, say, fit under a main panel, and acoustically small volumes tuned low typically = a longer decay time.

2/ The crossover between the LF leg and the main panel isn't right. Assuming a decent load for the former, the LF may be fine, but it's not like a crossover is a brick wall (and it wouldn't be much good even if that could be achieved); it's a more-or-less progressive rolloff, so in the case of bass drivers, you still need to pay some attention to what they're doing above your desired crossover frequency. If it's starting to struggle as frequency rises, that can be audible. Depends how far its been attenuated.
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#39 Re: Beyma CP21F match for Beyma TPL150H

Post by simon »

Scottmoose wrote: Mon Dec 02, 2019 11:31 am Not that I imagine anyone gives two hoots, assuming you select a sealed box with a Qtc of 0.5 ('transient perfect') then that's as 'fast' as it gets in the LF itself
To a relative speaker numpty this caught my attention. Whenever I've modelled (read - stuck some parameters in to a design/simulator app) I've aimed for Qtc of 0.7. I appreciate this might be a short question with a very long answer but what are the relative merits of different Qtc? I've seen the effects on peaking response, f3 and box volume but I haven't considered Qtc as low as 0.5.

I have a SB Acoustics sealed sub I use below 100Hz with two Alpair 12Ps in a tv console. It's okay as it's relatively compact (high WAF!) but sound is adequate rather than great. I used 0.7 Qtc and I'm now wondering if a different value might be better?

Apologies to John for heading OT.
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#40 Re: Beyma CP21F match for Beyma TPL150H

Post by Scottmoose »

Well, as you know Qtc (sealed box system Q) is the measure of energy at resonance. Therefore:

0.5 = Critically damped (transient perfect). Single 'let go' ringing frequency and no overshoot to the step response
0.577 = Bessel. Fastest settling after impulse, slight overshoot.
0.707 = Butterworth. Maximally flat, lowest possible F3, slightly more overshoot
1.0 = [one of many] Chebyshev alignments, with ripple in the passband. +1dB peaking at resonance, more overshoot. As Q rises, this trend continues, as you'd expect.

This is basically just electrical filter theory as applied to loudspeakers. Note that amplifier output impedance, wire & connection resistance have the effect of artificially increasing driver / system Q, so ideally needs to be factored into the enclosure / baffle alignment.

For a given drive unit, as box size reduces, so system Q rises, and visa versa. Technically, anything below 0.5 is overdamped and anything over 0.5 is underdamped. The lower Q alignments have a higher F3 than Butterworth, but technically superior transient performance. This is not to say any one is 'better' or 'worse' than any other, just illustrating how they differ.
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#41 Re: Beyma CP21F match for Beyma TPL150H

Post by IslandPink »

Group delay also increases steadily as you got up from Qtc = 0.5
Hence the low bass goes more out of phase with the upper bass and mids.
Which drive unit did you use for OB, Colin ?
There is the problem that any mass-loaded driver ( even at Qtc 0.5 ) will be operating a quarter-wave behind the driving voltage - which might not be the case for ESL's, even at low frequencies.
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#42 Re: Beyma CP21F match for Beyma TPL150H

Post by Toppsy »

Which drive unit did you use for OB, Colin ?
Mark,
I used the Monacor SP-382PA. Two per panel wired in parallel to increase the efficiency up to equal the 10" coax midrange/treble driver I already had in stock. https://www.monacor.co.uk/categories/15-3/vnr/103320/
Cheap as chips if you have a trade account., but a surprisingly good performer in OB.
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#43 Re: Beyma CP21F match for Beyma TPL150H

Post by IslandPink »

But was that what you were using to try & mate to the ESL's ?
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#44 Re: Beyma CP21F match for Beyma TPL150H

Post by simon »

Thanks Scott, very interesting. The apps don't tell me (in a way that's obvious to me anyway) about transient response, and group delay. I suppose then that my 0.7 Qtc is a little higher with other effects taken in to consideration. Food for thought.
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#45 Re: Beyma CP21F match for Beyma TPL150H

Post by Toppsy »

IslandPink wrote: Mon Dec 02, 2019 6:11 pm But was that what you were using to try & mate to the ESL's ?
Ah! thought you were referring to my OB experimental speakers.
In answer to your query: No I was using a dedicated Peerless subwoofer driver. Can't remember the actual driver reference now but it will be long out of production. I was trying to improve the lower bass on my ER Audio ESLIII speakers. I first tried it on a OB configuration and then in a sealed box recommended by the manufacturer for the actual driver. The sealed box was part of the solid oak frame of the speakers and mounted directly below the ESL panels. The ESLIII had 2 x dedicated bass panels with a central treble panel as per the Quad57's. I used a plate amp to drive the dedicated bass woofer. The only reference I can now on the forums is this: http://www.audio-talk.co.uk/phpBB3/view ... II#p121898. Worth reading the observations of the designer of these DIY ESL speakers.
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