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THE 66% SOLUTION

by Craig Schmidt

"You should go live with Dr. Gizmo" my wife shouted. "See how he likes running the vacuum cleaner around all of these speakers and space heaters (my tube amps)". "And now you want to build these monsters (pointing to my drawings)". "But remember honey, I could be out drinking (which I do) and chasing women (which I don’t)". She walked away muttering about the good doctor and farm animals. This meant that I was free to start my latest project aptly named because it is 2/3 horn and 1/3 wideband. (I feel I should warn you that this speaker system uses a complex crossover. So people with stomach problems should stop here or else have a bucket, bag, or something to ease the burden just in case.)

I wanted to try and build a cabinet with non-parallel sides. The pictures show what I came up with. The cabinet is three layers. inch MDF is first, followed by inch solid red oak, then American walnut veneer. I think they look cool especially when they are positioned in the corners. I also wanted to recess the drivers this time around. What a pain in the ass that was for me (even with a circle jig) but it came out fine. I did put in one 2 by 3 brace front to back. A pound and a half of Acousta Stuff was used on the insides and one strip of my secret stuff placed on the back wall.

I would like to discuss the driver choices a little as they go against the normal somewhat. The wide band driver is a 12 inch Beyma G125. It goes down to about 40 Hz. And up to just over 6 kHz.

For about 60 U.S. dollars each, these are such a bargain I think I am going to start to cry. The chassis on this baby is massive. Solid cast aluminum. There is no flexing here. (In my opinion this is a very important criteria especially when you are dealing with a driver this size.) It also comes with a huge ferrite magnet, and a real 2inch copper voice coil. The mass is low compared to other 12 inch units I checked out. The Beyma is about 98 dB efficient. The cabinet came to about 3.4 cubic feet. I used two 4inch ports to serve this giant, as one would have been ridiculously short plus I feel you should use the biggest total port size you can. Two ports are better than one.

Moving up the ladder is the Morel MHT-36 horn loaded tweeter. This driver uses a cloth cone (hand doped to optimum whatever) and has a gigantic magnet assembly for a high efficiency rating (97 dB).

These were very hard to get. I could not find anybody who stocked them and none of the vendors volunteered to order them except for Parts Express. The problem with that was I got better pricing from the distributor than P.E. They cost 75 dollars each.



Now last but not least is the midrange (my favorite part). Sorry, but I have to ramble on here a bit.

There must be special place in Heaven for people who can build wood horns. They are magical, mystical, and just plain beautiful. When you hold one it’s like holding a newborn, that is if you get the right ones which at first I did not! The black horns you see in the picture are from Raft Craft through EIFL. They were a little cheaper than the Fostex 400 horns but they were Japanese so the quality has to be there, right? Wrong! The horns function fine, in fact they sound great but at $320 each, plus a hundred each to ship them, the quality of construction that the Japanese are famous for is just not there period! There are paint runs, spots that were not painted properly, and areas that were not sanded properly. Chips in the wood (under the paint), plus poor hole alignment for the driver was the last straw for me. Oh, they offered to replace them but at almost a total of $400 more for shipping (neither EIFL or Raft offered to compensate me in any way for the shipping which really pissed me off!) it just was not going to happen.

I decided to replace them with what I should have purchased in the first place, the Fostex H400’s. They list at $500 each but they are worth it! They are perfectly built with a beautiful finish. (I sit and stare at them. My wife comes over and feels my forehead a lot when I do this.) For what it is worth, I found a place that discounts Fostex products and has, in my opinion, better service than EIFL. HIFIDO gave me a 17% discount on these horns and I have heard from other people I have turned on to them, they are getting the same discounts. (If anyone would like further details on this please email me.)








It was only natural to use the Fostex D1405 driver. In my opinion all Fostex drivers are works of art. This unit is no exception. (I wish I could figure out why wood horns sound so natural like this combo does.) While a lot of horn drivers are designed for p.a. or studio use, these are designed for hifi use and you can hear it! Now get some coffee or some other beverage and I will extrapolate on the crossovers.

I am not a fan of these devices but how else was I going to get all of these units working together. (As it turned out from extensive listening, I did not need all you see in the pictures). In all honesty, I had a load of fun working on these and did learn a little too. I did get help though. North Creek Music sells the best (my opinion) parts for crossovers. (They have a website. If I remember correctly it is northcreekmusic.com). Their coils are hand wound under low tension to exact specs. And they are automatically matched. The wire size you use is important because resistance builds up. They recommend 10 to 8 gauge for woofers! The best I could do was 12. Let me tell you that with 12 gauge solid copper wire, a 2.8 mH coil is HUGE and HEAVY! I can only imagine 8 gauge looks like. North Creek’s capacitors are also something else. They recommend cascading (paralleling) the capacitors until the required value is reached. The bottom line is they are very high quality and very expensive but once again you get what you pay for. The pots are the now very famous Fostex R80b’s. I will not bore you with construction details except to say that soldering these coils was a pain in the ass. The lacquer, or whatever it is that is used an insulator, is tuff stuff and has to be taken off first. I had to scrape it off with my Xacto knife down to raw copper and then solder with a gun. Forget about using an iron unless it’s a high wattage unit!

The basic design for this crossover evolved from a suggestion that comes with the D1405. The woofer crosses over at around 900 Hz at 12 dB per octave, the tweeter at around 10 kHz but 6 dB per octave. This is ok because the Morel can actually go down below 1 kHz although I would never run it that low. The midrange is a band pass. I took Fostex’s suggestion here thinking they know what is good for their own driver.

Now when I first started listening to the completed speaker the sound was quite acceptable but I noticed some harshness from the Beyma especially when I was close to the driver (meaning having my ear right up to it). After farting around with it for a while, I bypassed the low pass crossover totally for the wideband unit. The strange noise magically disappeared! I cursed for a while over this because I could not figure out why a coil and a cap could cause what was happening but figured that I should be happy that I was able to get rid of the problem by removing rather than adding.

As always , the famous question, how do they sound?

The soundstage that these speakers present is life size and while I thought they would beam, they do not! Depth is also excellent. I could go on but what’s the point. You would have to hear them for yourself. Yet, there really is a point. One is, wood horns sound wonderfully realistic and second, awfully expensive. This project cost me a lot of money in more ways than one. (I had to appease the little woman.) So if you are married and still want to enjoy the sound of wood horns, you must either be a master craftsmen with angel wings or you must stop at the bank for funds for the speaker project and jewelry for your spouse (unless of course she is a hifi nut like you and I). I sent along a picture of my wife for Dr. Gizmo. My wife says she wants a picture of him for the dartboard. Isn’t she sweet?

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