newbie needs help with dipole woofer hybrid esl

Hello all.

Has anyone here built a 12x48 esl hybrid with dipole woofer? I'm needing help with the basic wiring and amping setup and with bass EQ issues. First choice would be a 12" dipole woofer but may use a 8" in a TL, depending on difficulty and $$$

I'm new to speaker building and I've just committed myself to a hybrid esl. I have Sanders' cookbook but the electronics are over my head. I'm dead in the water trying to figure how to wire up the bass with the esl's, figure out the X-over's, how to EQ the bass and whether or not it can be done with passive filters and/or if I need to bi-amp. Rather than spend the next few years(?) teaching myself basic electronics, I'm not too proud to beg or copy someone's similar working configuration if anyone out ther has such a beast and is willing to share their schematics, etc.

For power I'll be using a Carver C1 preamp, Carver TFM-25 225w/ch power amp and (if necessary) I have an old Kenwood 100W/ch integrated amp that can possibly be rigged as a bi-amp for the woofers. DS spacing will be

For better or worse, I've already ordered and paid for the following items:

* (4) .063 perf'd steel 12" x 48"
* 10-meter roll 6-micron mylar
* 2 oz diaphram coating solution from Just Real Music
* ESL electronics kits from Russ at Just Real Music:
bias power supplies, M299 transformers (100:1 I
think) and 225 hz passive high-pass filters to chop off
the bass to the esl's.

Now: How do I marry up the bass drivers to the esl's with descent results?

Thanks in advance y'all,


2004-04-14 10:51 pm
Maine, USA
I'd suggest that you bi-amp, and if the electronics are completely new territory, consider making the crossover a little less DIY than the rest of the project. Have you considered purchasing a commercial crossover---maybe something like the Behringer DCX2496? It would allow you to conveniently play with crossover points and slopes without having to mess with changing resistor or capacitor values in a DIY op amp circuit.

Also, based on my experience, unless you're going to run your ESL quite low in frequency (probably lower than your suggested 12 x 48 inch panel will like) many 12 inch woofers will have a hard time reaching high enough in frequency to blend nicely with the ESLs. I'm sure it would possible to find some drivers that'll do it, but I ran into problems in my own set-up, as described in this link. I vote for a smaller woofer or array of smaller woofers.

Thanks FEW,
I wish I could do the commercial X-over thing but I blew the budget on a Carver system to push the esl's (ex-wife & 2 teens to support too). However, I'm thinking you're right about the smaller woofers. I like a pair of 8" Dayton References in TL's under the esl's.
I will post a drawing when I get it done. Given my lack of funds and smarts, I think my starting point has to be bi-amping thru passive filters... at least for now. I can use the 225 Hz 12/db hi-pass's supplied with the ESL kits from JRM, then build some matching 225 Hz low-pass filters for the woofers. I've got Dickerson's Cookbook too so I should be able to figure out the low pass filters. That said, I'm not confident that passive filters will give stable x-over points on the esl's, as everything I've read says esl impedences vary so much with frequency. I figure I will end up with some suckout on the midbass too, which will need to be EQ'd and that's where I'm not confident what to do.
Other than my ears, I don't have the means to plot response curves and model correcting circuits so I'm in the dark, as it were. I do have an old Audio Control C-101 graphic EQ which has a rudimentary RTA with a mic and pink noise generator - - maybe I can do something with that??

I will keep posting as the components arrive.
Everyone please keep those suggestions coming!!



2005-11-15 12:32 pm
If both the ESL and woofer are open baffle you only need a 1st order low pass filter at the lowest starting frequency of the woofer.

The woofer and ESL will get a natural 1st order filter tuned by the baffle width (sound circulation).

I own a system like this that you can buy at
Starting frequency is 50 Hz (1st order roll off) and the baffle width is tuned at 400 Hz.
Have you tried doing a web search for some of the free software available for speaker testing? If you already have the microphone you might be able to get something useful up and running at little or no cost. It can take awhile to figure out how to do (and interpret) sophisticated speaker measurements, but without too much trouble you could probably get something that would help you set the relative levels of your woofer(s) and ESL panel, for example. I think you'll feel like you're shooting blind if you try to move forward with your project without any measurements at all. Your RTA system might be of some use, but that'll depend strongly on what sort of resolution (SPL and frequency) it has. Unfortunately it won't allow you to do any quasi-anechoic measurements, which are very helpful when doing measurements in real rooms.