1st draft hybrid ESL with 10" woofer

[CharlieM]

Hello all,
Attached is a first draft of my planned ESL. I will be bi-amping with two Carver TFM25's (225W/channel each) and active X-over. I'm still working out the enclosure design for the woofer (an area where I have no experience or aptitude for associated puter programs). I didn't figure a 8" would have the punch I'm wanting; hence the 10" woofer. Sanders' guidelines indicate a 500hz to 550Hz X-over and I'm thinking a 24db slope with a woofer good into the lower midrange. I'm looking at a Aurum Cantus 10" woofer because it's good to 3Khz and has 8mm X-max but I'm not sure it's suitable for a TL (Qts .33). I need a minimal box volume to meet my design goal and to keep the overall height to 6ft-- which requires some compromises, of course.

Please everyone have a look and feel free to advise the newbie :-) All suggestions / alternatives are welcomed.

thanks!
Charlie

[CharlieM]

Forgot to mention the TL line's cross sectional area behind the woofer is about 100-% of the woofer's piston area, and tapering down a 7 1/2 ft line to about 70% of the woofer's area at the terminus. Sanders' book suggests these areas as absolute minimums. Again, I'm not at all sure the Aurum Cantus woofer is suitable for a TL. Please advise, thanks
Charlie

[stokessd]

That looks good, a couple comments that may or may not be useful:


In my experience with a 48” x 20” ESL panel, an 8” woofer in a TL enclosure was more and sufficient. I used a good motor woofer with lots of xmax (I used a seas excel) and low distortion to mate with the panel nicely. A lot of folks think that more woofer in better, but if you are concerned with space and would like to reduce the TL volume, an 8” woofer may be the way to go. You won’t reduce it a lot, but every bit helps.

Make your crossover so you can try different crossover points. In my experience, crossing over that high made the speaker sound phasey and odd. I settled on 130 Hz as my crossover point. This may or may not work for you depending on how you build your panel. I used support dots rather than support strips. This supports the mylar well enough to prevent collapse, but the resonant frequency is actually very low compared to narrow ESL cavities based on support strips. This gave me the freedom to move the crossover point up and down and tune where I wanted it to be. My panels 18” x 46” active area panels have 5 or 6 support dots running down the center and have a resonant frequency of around 40 Hz (although I haven’t retested that after aging, I bet it’s a lot lower).

I like your design although I wouldn’t do the plexiglass box, in favor of the whole thing looking like wood, but that’s just a personal preference. I’d think about how to remove the panel in your design in case you have to move. You’ll be happy if you can take it off and protect it in a box and remove the tall wings for ease of transport.

Also, I tend to make my TL’s following a 125% - 100% rule of thumb, and I pack them with about 0.5lb/ft^3 of polyfill. But TLs’ are surprisingly forgiving so I bet the 100% to 70% will work out well. I was already building huge speakers, so I did everything I could to make mating the woofer to panel go as smoothly as possible.

Good luck with it, it’s looking nice.


Sheldon