Malcolm, a SEOS12 Center (Middle?) Channel speaker

Here it is, an Ewave type center channel, dubbed "Malcolm". It uses a SEOS12 and (currently) one of Erich's "less good" clone drivers.

Weather was good tonight and I had a little time to set up outside and take some pattern measurements.

Woofers are 4x DS-115-8, cleverly (or so I think) arranged as a shaded horizontal line source. Near crossover, the middle pair plays dominantly to match the SEOS12 pattern, with the outer pair cutting in a few hundred Hz lower and continuing directivity like a 20" driver. The effect is rather good constant horizontal directivity down to about 500Hz, in a box only 12" high and 21" wide. 8" deep. The speaker cabinet looks a lot better than it appears in the camera photo (the flash does funny things inside the waveguide contours). The crossover mess on top, though, is every bit as ugly as it looks here -- needs to be put on a board and mounted inside.

The box is ported, tuned to 60Hz and has an F3 of about 57Hz when mounted against a wall (above or below an LCD monitor is the intention).

Here are the Horizontal curves, unsmoothed. 0 to 60degress in 7.5 degree steps-

Pretty good, huh? Check it out in the usual 1/6th Octave smoothing (0 to 90deg):


These are some color polar plots of the horizontal performance (map and cylinder formats):



In the vertical, the waveguide can only control directivity down to about 3kHz or so and the woofers (being only 4"ers) don't control it at all. But the very close 5.5" CTC keeps the curves smooth and useful so what does go vertically off axis is at least well-behaved. Vertical Upwards, 0 to 60, unsmoothed:
\
Vertical Downwards:


And here's the high-tech measuring "lab", including speaker precariously balanced on a ladder with a sheet of MDF clamped below to try to simulate an LCD screen. The whole arrangement is about a foot from the door behind it, so bass wasn't as good as it should be.

 

Here is schematic and partslist for Malcom 1


266-552 Qty 2 1.5mH
255-044 Qty 1 0.8mH
255-026 Qty 2 0.25mH
255-038 Qty 1 0.55mH

027-940 Qty 1 22uF
027-406 Qty 1 0.47uF
027-438 Qty 1 25uF
027-427 Qty 1 6.2uF (use for 6uF)
027-410 Qty 1 1uF
027-364 Qty 1 150uF
027-354 Qty 1 50uF

015-.5 Qty 1 0.5 Ohm // Combine with 1.0 ohm to make 1.5 ohm
015-1.0 Qty 1 1.0 Ohm //

//These two could be replaced with an L-Pad if adjustment is wanted:
015-3.0 Qty 1 3.0 ohm
015-12 Qty 1 12 ohm (use in place of 13 ohm, close enough)

015-10 Qty 1 10 ohm
016-1.2 Qty 1 1.2 ohm
015-1.8 Qty 1 1.8 ohm
015-3.3 Qty 1 3.3 ohm

260-407 Qty 2 1.5"D Ports (shorten each by 1").

295-424 Qty 4 4" Designers' Series woofers
SEOS12 Waveguide Qty 1 (get from Erich)
Horn driver: Qty 1. Designed using "lesser" clone from Erich. "Better" clone will work nearly same (slightly smoother). B&C DE250 (294-605) will work as well also, though expensive.

Box made with 0.5" ply, baffle is 3/4" MDF. Outside dimensions are 21" wide, 12" high, 8" deep. Woofers spaced with 0.5" between edges. Box has internal window brace (with cutouts to allow air flow) between top section and woofer section. More bracing might be a good idea.


____________

BTW, there has been a Malcolm2 version made. And it was a complete flop! I used 4 of the Aura6 woofers, mounted on top of the short, wide, box so that they were up against the back wall, really well-made plywood box, no pieces had to be remade, I should've known something was wrong. I miscalculated the distance beween the woofers and their "reflections" on the wall, The center-to-center of those was about 6.5" and the listener is getting the wave from the reflection delayed by about 0.5msec, making a BIG suckout right at the 1kHz crossover point... oops. So that really nice box is firewood. I have a plan for a Malcolm3 but that will have to wait until I have time again, whenever that happens.....

 

You da man, Bill! Thanks for your tireless efforts with the designs.
Malcom in the Middle. You really crack me up!

 

This is great! Love the horizontal line array, bwaslo. I'm looking forward to Malcom 3. Is there any chance of a version using 2x NS6 drivers instead of 4 as a small surround?

 

How did the Malcom 2 behave when pulled out from the wall?

 

Bass falls off, as you'd expect. It counts on boundary reinforcement.

 

IMO, this speaker is the most interesting thing yet to come out of the SEOS project.


Very creative, Bill. And it looks like a very room-friendly way to get a properly identical front trio of mains.


How do you think the response would suffer if it was scaled up a bit, to say 4 NS6's in your shaded array. (Something about the idea of all NRT motored drivers - NS6's, NS-series subs - from ~1kHz down seems just "right" to me. And unfortunately Madisound seems permanent sold out of the old Ford GT/McIntosh blue-coned Aura 5" drivers.)


Would that really need an SEOS15 (and higher price, because they're only available in fiberglass) or would an SEO12 still work, and get the kind of on-axis response and polars you're getting with the DS5/SEOS12 combo?

 

Thanks, glad you like it.

If you want to use the same design for side channels, too, you'd need to put something below them for boundary reinforcement. Something behind them would be a good idea, too.

The one above the monitor will be against the wall and facing forward, but the ones on the sides really need to be toed-in (otherwise, IMO, you're just wasting the effects of using a waveguide -- see http://www.diysoundgroup.com/forum/index.php?action=articles;sa=view;article=1). Toe-ing in will bring them away from the wall, which is probably not a great idea (though EQ may be able to deal with it).

You should be able to use NS6 drivers, but the speaker will get taller, nearly square-shaped. Not too consmetically appealing above an LCD screen, but maybe something can be done with grille cloth?

 

I'd probably just build angled cabinets for the side speakers, so they're all close to the front wall. I've been a believer in "overtoeing" and since some DIYA posts by Dr. Geddes convinced me to try it.

I was thinking of mounting the LCD a bit high, so the front trio could be at an identical elevation below it.

At any rate, it'll probably look better than this:



Or, prior to the Nathan Funk cabs, this:



A single guy can get away with that. Dr. DS-21, wonderful as she is, just won't let me next get away with it next go-around.

So I gotta figure out a way to get decent front mains in an aesthetically appealing package. (Though until your Malcolm design got my brain moving my leading idea was to put my existing Tannoy-based speakers on wall-mounts up high and run a thin drape across the top.)

 

Ceiling hugging waveguide speakers maybe? There was a discussion of that in the "hey guys" thread at AVS. A sketch, too. Put the NS6s against the ceiling, the seos beneath. If I have time I may try that.

 

Bill, do you even use a center?

 

No, not yet. Have it built, but need to come up with a way to hold it above the screen. Don't really feel a strong need to get on with it, the phantom center works very well with the toed wgs on the fronts. But I did the Malcolm because people kept asking about ewave centers. Sometime I'll make up a bracket or something to hold it up.

 

bwaslo,

I have an idea for a SEOS/E-Wave center, but it involves a smaller SEOS, like the SEOS 6. Use two 10" high sensitivity 16 Ohm woofers run in parallel up to 500Hz, (Eminence Delta10B, or pricier Faital Pro drivers), flanking a 6" high sensitivity pro midrange, with SEOS 6 or similar (maybe a Denovo?) waveguide above. 12" tall, 28" wide, 95+ dB sensitivity, and able to reach reference with only receiver power. Catch? Can only be tuned to ~65Hz and highpassed, unless you use pricier drivers.

Stack the drivers vertically, and you have a main/center solution for non-acoustically transparent screens.

Another option would be using a coaxial in the center, like the JTR offerings that can be placed vertically or horizontally. I have not seen a DIY version that I know of.

I have yet to experiment with CBT solutions to see if reference is do-able with receiver power in a slim package, but I plan to this summer.

JSS

 

Bill & MM,
Any new progress on these center channel designs?

 

Yeah, I'm trying to cajole Erich into making me a Malc olm-like cabinet with 4 six inchers. If he gets to it, I'll work up a crossover for it. Should get nice directivity and bass spl

 

Any luck in your cajoling? :-D


In my room, I have to mount my side surrounds up at the wall/ceiling corner so am considering the modded design you mentioned to DS-21 above and earlier here:
http://www.avsforum.com/t/1291022/hey-guys-we-need-a-little-rallying-here/3360#post_21846794

Did you still have plans to attempt that configuration at some point?

 

Bill,


What do you think of an SEOS-8 and 2 4" Dayton Designer Series woofers for surrounds?

 

Sounds ok, but the SEOS 8 is hard to get and expensive. I think Erich has found a good alternate 8" waveguide that might work if time or $ are problems.

 

Bill,

Adding "Malcom" questions. I am the newbie pursuing the Malcom with 4 x NS6 drivers.

1) On the attached do you see any concerns with recessing the NS6 drivers and then "overlapping" the bottom edge of the SEOS in order to save some height?

 

Bill,

Sorry this "sent" before I added the sketch - here it is.
Also; how about the spacing between the NS6 drivers - am planning for 1/2" ?

Thanks!

 

Recessing the woofers more than the waveguide will move the crossover null downwards some. If the speaker is above the monitor, probably not a very bad thing, but I'd still try to keep them on the same plane if I were you. To save height, maybe move the woofers right to the edge of the cabinet (the mounting ring of the woofer would be right over the bottom wall).

Spacing between the NS6 of 1/2inch should be fine.

 

Thanks Bill!

I have enough vertical height on my baffle to employ these suggestions!
Appreciate your input!!

 

Hello all,

Would angling the woofer baffle (like the JBL Everest's) help the horizontal response measurement any; or would the angled baffle present a problem for the waveguide? I'm not saying the Malcolm measures badly now, just curious.

Also, if using the Malcolm, would it be preferred to use 5 identical channels; or could one escape with three Malcolm's up front and two more conventional SEOS waveguides for the surround channels?




EDIT: BTW, count me as interested in the ceiling hugger design as well. That's an elegant solution for addressing room clutter and WAF.

 

The angled baffle in the Everest is used to form the sides of the midrange horn. It's a cosmetic thing, and not applicable to SEOS (which already has sides!).

Malcolm was designed to be a center channel to be used with SEOS speakers (usually 10 or 12" woofers under a SEOS12) as the fronts or surrounds. Of course, a Malcolm could be used for any or all of the speaker positions, but its shape is a bit odd for non-center ones. As front channels, you'd want to use them toed-in (see http://www.diysoundgroup.com/forum/index.php?topic=20.0O which could look kind of weird with such short wide speakers. They'd also loose some bass if pulled away from the walls for toe-in.

 

Bill,


Still trying to figure out my surrounds. Someone mention doing the 8" seos with the poured concrete. However I started wondering if I could use 3 of the Dayton DS-115-8's under the SEOS 12 for surrounds, but have them very close together? I know it may sound pointless, but it's more for aesthetic reasons. Plus the Malcolm looks pretty beastly for surround purposes. I'd like to have something smaller. Thoughts?