ESL and 8" Servo Subs

HT cOz · « **on:** 11 Nov 2012, 04:07 pm »

Earlier this year, I contacted Kim Beumer of Crescendo Systems about creating an ESL speaker that could be matched with Danny's new 8" Servo Subs. The thinking was to build something for Lonestar Audio Fest 2013. Since then I've become completely consumed with the 9-5 job, but I wanted to share the vision and work that Kim created.

The vision is simple, 8" servo subs can play high enough to be matched with a reasonably sized ESL panel. The subs can also play low enough to create a true full range speaker. The size of the Hybrid is very attractive to people that don't have giant rooms etc.

The total dimensions are 5' high, 1' wide with 3' for the panel and 2' for the woofers. There are a few options for finish out that were being explored. The design still has some flushing out to do around the sizing of the bass sections. But you can get an idea of what is possible.

The first option is not to do anything and leave the woofers uncovered.

The second option is to cover the woofers with the front stator (which is perforated) giving it a very clean look.

The third option is to use regular loudspeaker cloth to cover the woofers front.

I think this is an exciting project and someday it may be completed. For now it is an exercise in what is possible. ESL panels and 8" Servo Subs could be a killer combination.

Cheers,
Robert

rollo · « **Reply #1 on:** 11 Nov 2012, 04:34 pm »

Second option looks real good.

charles

Jazzman53 · « **Reply #2 on:** 11 Nov 2012, 06:18 pm »

I like option two also.

Hank · « **Reply #3 on:** 11 Nov 2012, 10:14 pm »

Interesting and I like the second one also. For quite a while I've been studying planar speakers and am looking for used candidates. I read what Roger Sanders had to say about incorporating dynamic woofers with ESL'.s. I also read what Bob Carver did and have learned a bit about the type of driver needed to mate seamlessly with ESL's. What has "worked" in the past is specific Q, thin, very lightweight cone, small magnet, etc. I've thought that if I buy a used hybrid that I might use one of Danny's 12" survo subs as a replacement dynamic driver. I've thought about his new 8", but it would take at least 2, as you are contemplating. Good success on your project

mykyll2727 · « **Reply #4 on:** 11 Nov 2012, 10:38 pm »

Another vote for option 2. Also much success with your endeavor. I'm really looking forward to updates.

persisting1 · « **Reply #5 on:** 11 Nov 2012, 10:52 pm »

Will this be using an existing panel from Cresendo or are you looking to design something new?

richidoo · « **Reply #6 on:** 12 Nov 2012, 01:49 am »

2 and 3 are nice. I like the concept.

How high does the servo 8 play? Where would you need your crossover to be? 4th order?

I hope you find the time to build these.

gregfisk · « **Reply #7 on:** 12 Nov 2012, 02:20 am »

I like the second and third options as well, this seems like a fun project, please keep us posted with what you end up doing.

beun · « **Reply #8 on:** 12 Nov 2012, 05:10 am »

Since I have no pre-made panels in stock, it is going to be custom made. The construction method though is going to be the same. Personally I also like the look of option 2, although I am a little apprehensive about the sound quality. It is definitely not going to be as open as no covering or a cloth finish.

Ultimately it cannot be too bad since ML uses this method as well. a panel this size should be crossed over at around 200-250Hz, which should be well within the capability of a 8" woofer.

Kim Beumer
Crescendo Systems

Danny Richie · « **Reply #9 on:** 12 Nov 2012, 02:20 pm »

I had been thinking about doing something similar to this with the newer Maggies, but it was going to require redoing the frame structure, support, and mounting system. And frankly I just don't have time to deal with heading that project.

I'd be glad to work with Kim or support him on the project. I think they would be a really good match.

A narrow design like that would have a really good look and wife acceptance factor. And with the panels not having to play down low that will really relieve them. They could then hit some higher SPL levels without fear of shorting the panels out from them touching the grid.

And Martin Logan never really had the speed from their lower woofers to integrate them very well. I think these will integrate really well plus add a lot of flexibility with the refinements and adjustments of the servo amps.

Great idea!

beun · « **Reply #10 on:** 13 Nov 2012, 04:25 am »

Danny,

I think I would need input on the best way how to create the optimal H-shape for the woofers. I looked at the really cool curved design of the supervbox and I wondered if it is only for aesthetics or if it has an acoustical advantage like spreading out the cavity resonance.

Kim

HT cOz · « **Reply #11 on:** 13 Nov 2012, 04:40 am »

The full length Stator is the obvious aesthetic choice as it looks just awesome

Would the woofers put too much pressure behind the Stator? If this route is taken should a 3 woofer configuration be considered? Are these questions that can't be answered until some experimentation is tried?

HT cOz · « **Reply #12 on:** 13 Nov 2012, 04:46 am »

Quote from: beun on 13 Nov 2012, 04:25 am

Danny,

I think I would need input on the best way how to create the optimal H-shape for the woofers. I looked at the really cool curved design of the supervbox and I wondered if it is only for aesthetics or if it has an acoustical advantage like spreading out the cavity resonance.

Kim

Kim,

One idea would be to build the H frame boxes, widen the from panel 1"-2" and keep the curved sides. That might also allow the Stator to meet the woofers at 200hz more comfortably. Certainly any thoughts of widening the design have to be considered against keeping the design small, but I'm not sure anyone would notice a very small amount of widening to accommodate the fully build H frames?

Danny Richie · « **Reply #13 on:** 13 Nov 2012, 03:22 pm »

The woofers just need to be in a H frame just deep enough to cover the depth of the magnets. And it is pretty important that the sides be fairly thick and solid. So the curved sides as drawn would be good to go over the outside of a complete H frame to help keep it solid.

On the Super-V there is a black four sided box on the back side of the driver only. Then the thicker (1.25" thick) side panels finish out the front half of the top box and the back half of the lower box. This was done to keep the width of the box down.

jparkhur · « **Reply #14 on:** 13 Nov 2012, 03:30 pm »

You could take a MMG and sandwich it in between to vertical rails, attach to the lover servo woofers... Ummmmm Yummy........ The image may be off, too high.. only one twelve would work better instead of two.. two 8's would be similar... still very yummy.

JP

Rclark · « **Reply #15 on:** 13 Nov 2012, 10:17 pm »

I don't think so, MMG's like to be elevated some, but you could also do horizontal 8's across the bottom. Agreed, that would be one sweet speaker.

beun · « **Reply #16 on:** 14 Nov 2012, 06:09 am »

Danny,

That is a very illustrative picture, I know get exactly how it all fits together. Let me create another drawing an incorporate what I just learned.

Hank · « **Reply #17 on:** 14 Nov 2012, 12:31 pm »

If you're never going to move/ship these anywhere, then the "unibox" is fine and looks great. However, for shippable speakers, you'd want to have the planar section detachable from the woofer, like Magnepan and the hybrid electrostatic manufacturers.

mboxler · « **Reply #18 on:** 14 Nov 2012, 03:20 pm »

Quote from: jparkhur on 13 Nov 2012, 03:30 pm

You could take a MMG and sandwich it in between to vertical rails, attach to the lover servo woofers... Ummmmm Yummy........ The image may be off, too high.. only one twelve would work better instead of two.. two 8's would be similar... still very yummy.

JP

Would this work? A pair of these...

attached over a pair of these...

each filled with a SW-12-16FR and a A370PEQ?

Could be detached for moving.

Mike

jparkhur · « **Reply #19 on:** 14 Nov 2012, 03:28 pm »

Those are my boxes, and they are not open baffle, that is the cut for the amp. That 16 ohm would need 4 cubic feet... So if you wanted to do OB with the MMG, you could. That is set up for a 4 ohm driver and one amp per side. You could do two twelves or multiple 8's on one side with the correct ohm rating for parallel wiring. I think the MMG would be too high off the ground to have the correct user sound. It maybe above 35 inches isn, which is where my ear ends up when sitting. I wonder if, anyone can comment, you could fire through the MMG, fire downward in a vented sealed box, or side fire two drivers on each side. I could see using two twelves side firing on each MMG, hiding them behind the panel. The MMG's are 14 inches wide.. this would just give you enough room (width wise) to mount two of them with a space between the vents on the backs of the coils. That would be cool. You would remember that the box would cause some issues with it being in the way of the panel.. uhhhh.. That wont work will it... ok.. just buy two GR 12's and put them around the MMG.. There.. fixed..

Jon