LeCleac'h Horn Loudspeaker System

I have been jealous of Jean-Michel LeCleac'h's speaker system since I first saw photos of it five years or so ago, but building such a system would have cost a couple thousand bucks I didn't feel like spending on speakers.

In the fall of 2010, I was driving the kids to choir practice, and I saw a bunch of public-address horns and drivers sitting on the curb. I pulled over, hopped out of the car, and asked the man raking leaves whether he intended to be giving away the gear for free. He said he was, so I wedged it all into the back of my van and got glared at by the kids. I was now in a position to wheel-deal myself into a LeCleac'h system. I sold two of the horns and one of the drivers, along with a bunch of other old gear.

I first heard of Martin Seddon's fiberglass horns in the context of his AH-160 for Lowther drivers. Martin had used the (acoustically sweet) horn curvature developed and published by LeCleac'h to make molds for fiberblass layup. Martin very generously described his whole design/build process to me in email, but he recommended that the mold-making process had been a royal pain in the ass, and he recommended that I buy horns from him rather than make my own molds. This seemed like good advice, but it stalled me out for a few years.

Once I had the money together from the sold-off salvage, I immediately ordered a pair of his AH-425 horns, which were designed for the remaining pair of salvaged Altec 288C drivers.

The horns simply bolt onto the drivers, so there's nothing to "build" here.

Those drivers on those horns cover (conservatively) around 800Hz to around 8,000Hz, so I still needed to cover 30-800Hz and 8,000-20,000Hz:

30-70Hz: ???
80Hz-800Hz: ???
800-8,000Hz: Altecs/Azuras
8,000-20,000Hz: ???

(The photo for this step is from Martin's website.)

I already had a 12" subwoofer from Parts Express that I like well enough, so that's 30-70Hz covered nicely:

30-70Hz: Subwoofer
80Hz-800Hz: ???
800-8,000Hz: Altecs/Azuras
8,000-20,000Hz: ???

I also already had some Fostex FT17H supertweeters. I used my dad's plunge router and a Jasper Circle Jig to mill some donuts out of 1x8 alder, mounted the tweeters in the donuts, and stuck the donuts (via brass threaded-inserts screwed into the donuts) on universal joints mounted to bass-drum mic stands.

That's 8,000-20,000Hz covered. So now we've got:

30-70Hz: Subwoofer
80Hz-800Hz: ???
800-8,000Hz: Altecs/Azuras
8,000-20,000Hz: FT17H's

I used some of the salvage money to buy a pair of JBL 2225H woofers salvaged from a closed-down movie theater.

I used WinISD to design some 3ft3 bass-reflex boxes tuned to 40Hz, and then manipulated the cabinet dimensions (keeping the volume constant) so the boxes would fit inside the built-in cabinets in my office (if I un-mounted the cabinet doors).

The 2225 data sheet specifies a "highest recommended crossover point" of 1,200Hz, so these should cover my 70-800Hz range:

30-70Hz: Subwoofer
80Hz-800Hz: JBL 2225H Bass Reflex
800-8,000Hz: Altecs/Azuras
8,000-20,000Hz: FT17H's

I'll detail the cabinet build in the next few slides.

I went to the lumber yard and bought three half-sheets of 3/4" MDF. (I know from experience that I can neither lift nor haul full sheets, so I buy half or quarter sheets whenever I can.)

I don't own a table saw, so I wrote up a cut plan and used a circular saw with a fresh carbide blade, a tape measure, a big L-square and one of those nice clamp-on straightedges from Rockler. My panels actually turned out more square than the last couple of times I've cut big panels on a table saw.

I wanted to use biscuits as a hack to hold the panels in square during glue-up. I'm not graceful with big pipe clamps.

I used WAY too many biscuits, as you can see...but the process was very satisfying and worked great!

(The one thing I would do differently next time is that I would adjust the joiner so the panel edges come out just slightly proud, and then trim them off with a router after glue-up. My joints this time were wacky by a 32nd of an inch in some places, and I'd prefer to avoid that.)

I used regular yellow wood glue.

I painted five sides (all but the front) of each box with gloopy, gloppy black DuraTex texture paint, because:
- I like the way DuraTex looks
- I didn't want to spring for enough veneer to cover all six sides
- Those five sides were going to be hidden by the built-ins anyway.

I cut the holes for the woofers and the port tubes in the front baffles with a plunge router and a Jasper Circle Jig. I drilled pilot holes for the port tube screws and woofer bolts, and installed T-nuts on the inside of the panels for the woofer bolts.

I used iron-on cherry veneer from tapeease.com. Boy, was that easier than using contact cement! I recommend it! You can make your own iron-on by rolling yellow wood glue onto plain paper-backed veneer and letting the glue dry, but I couldn't be bothered.

I sanded the veneer carefully and finished it with "natural" color Watco Danish Oil, then glued the baffles into place.

Per Wayne Parham's standard advice, I installed braces made of 1x2 aspen between the woofer hole and the port-tube holes. (One brace front-to-back, and one brace side-to-side.) (This is to add some acoustic deadening to the panels. 3/4" MDF panels are just the starting point for how dead you'd like for acoustic perfection. I'd use double walls with sand in between if I could stand the work and the weight.)

Also per Wayne, I glued R11 fiberglass insulation to the top, back, cross-brace and one full side. (This is to prevent unwanted standing-wave resonances inside the boxes.)

I ran 18ga zip cable from the terminals to the woofers and screwed and bolted everything on.

The woofer boxes are DONE!

I already had a Rane AC23 stereo three-way active crossover and a bunch of preamps and amps.

What's going on in the photo is:

The iPod (full of 256K VBR MP3's) runs to the TCC TC-754.

The TC-754 runs to the Rane.

I have the Rane set up to split the audio signal into three chunks: 0-70Hz, 70-800Hz, 800Hz and up.

The 0-70Hz chunk goes to the subwoofer.

The 70-800Hz chunk goes to the Dayton DTA-100 30-watts-per-channel amplifier. The DTA-100 goes to the 2225 speakers.

The 800Hz-and-up chunk goes to the Sonic Impact T-Amp 6-watts-per-channel amplifier. The T-Amp goes to both the Altecs (via an L-pad that pads each Altec down so it's the same volume as its supertweeter) and the supertweeters (each via a capacitor, which keeps sub-8K frequencies from hitting it).

Cable spaghetti!

I like it!

I'll be messing with the exact crossover points and levels for a while (and I'm itching to repair a couple of my vacuum-tube amplifiers so I can swap them in), but I'm losing a lot of sleep listening to music, and that's my baseline for a successful system!