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Here's a stupid idea I'll probably do anyway

Bauhausler

Bauhausler

Rational Subjectivist
Hey, all. I've been fooling with a batch of AR speakers, trying to get a pair working with all live drivers. It looks like I'll have a pair of cabinets and woofers left over. I had a cab on my bench removing the tweet and mid, and I was thinking over what might fit in there to make a complete speaker out of it again. I love the bass of these ARs, but the mids and treble just aren't my absolute favirite. OTOH, the Kef B-110 is one of the best sounding drivers that I have on hand from about 200 hz to 3khz. Coincidentally, this driver has exactly the same external diameter and BCD as the AR mid. It will drop right in. Because the B-110 is open backed, I'd have to come up with some kind of more or less airtight housing to keep the woofer backwave away from the B-110's cone. Rough measurements indicate that I can adapt a metal coffee can, cut down to the right depth, as a housing for the back of the midrange. The housing would need some kind of stuffing as well, but fiberglass should work fine there. For a tweeter, the Kef T-27 can be adapted to fit the AR cabinet. The T-27 and B-110 are the classic combination used in several famous speakers, including the BBC LS3/5A, Fried H, JR 149 and others. I have two different crossovers built that would work for the B-110/T-27. In practice, I think I would mount 6 terminals on the back of the speaker cabinet for the connections to all 3 drivers. This would allow much better access for fooling with crossovers. Also, the speaker could be actively biamped, which might be necessary due to mismatched sensitivity between the woofer and other drivers.
Attached are pix with two views of the cabinet with the AR woofer, B-110 and T-27 placed in the baffle.
 

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willyrover said:
I definitely prefer the first view. So much more lifelike.
Click to expand...

Oops. That's what I get for using my phone cam for snapshots. I haven't got the software figured out yet.
The first pic is Martin. he's a 14 year old 135 lb Spur Thighed Tortoise. He's the housepet of a local pet shop where I buy earthworms for my pet turtles. Martin has the run of the place. I was in there last week and Martin was out for a walk. My wife fed him a piece of Romaine lettuce and I took his picture with my phone. You can't really see how big he is in the photos. I've seen a junior high kid ride on him and it hardly slowed him down at all.
 
Back when we were renting it was at the end of a cul-de-saq that abutted some woods and a stream. One day we saw this big turtle cross the road- his shell had to be at least 15" wide by over 20" long. I had no desire to mess with him.
 
let us know how it sounds and what you do with the xo.
i love the kef mid you're using. actually the best mid i've ever heard so far.
 
merrylander said:
Back when we were renting it was at the end of a cul-de-saq that abutted some woods and a stream. One day we saw this big turtle cross the road- his shell had to be at least 15" wide by over 20" long. I had no desire to mess with him.
Click to expand...

Probably a snapper, and definitely to be avoided if it was. They're the meanest thing around.
Martin's harmless, but I make sure I don't get in his way. I only outweigh him by 15 lbs and he's a lot lower to the ground.
I'll probably try out the AR/Kef frankenspeakers today. I suppose I could call them an AR3/5A or something. Looking at the mounting for the B-110, the T-nuts in the cabinet are in exactly the right places for the B-110's mounting holes, but the T-nuts are 1/4-20 and the B-110's mounting holes are sized for 6mm screws. A 1/4-20 screw won't fit. I'd have to drill different holes, OR...
Here's another idea that kills 2 birds with one stone. I can use 4 lengths of #8 threaded rod to mount the driver. They would be nutted on the outer surface of the frame, pass through the T-nuts on the cabinet, pass through the 'can' rear enclosure, out the back of it and be nutted on the back of the 'can' to hold it all in place. I think that's much easier than trying to attach the can to the back of the baffle with screws from the inside or something. I might have to stiffen the back of the can with big fender washers or a Masonite plate to keep the nuts from pulling through, but I doubt that would be a problem. All pretty basic carpentry.
 
On that mid range cup, I would go buy a pet dish that has a lip on it then screw/ glue that lip to the hole. I know there are several sizes available and some are in stainless steel as well. Just a thought here.
DC
 
How to build Darwin speakers:

1) Buy two large 135 pound turtles
2) Remove shells
3) Eat the meat
4) Use shells as cabinets

Steve
 
One of your speakers looks a heck of a lot like a giant turtle...

Who'd you get to make you such a realistic speaker cabinet? LOL
 
dc270 said:
On that mid range cup, I would go buy a pet dish that has a lip on it then screw/ glue that lip to the hole. I know there are several sizes available and some are in stainless steel as well. Just a thought here.
DC
Click to expand...

I was looking around the kitchen for ideas on cheap/easy enclosures. I stumbled across a pair of tubular cardboard midrange enclosures that I removed from Wharfedale W60D cabinets. They're exactly the right diameter. The problems with mounting the enclosure directly to the back of the baffle are:
1) interference. There's a brace right next to the edge of the hole, which would prevent any flange from being mounted to the baffle.
2) access. Very difficult to drill holes & install screws in the tight space inside the cab.
3) permanent alteration. I'd prefer not to make holes where there aren't any now.

I'm going to scrounge for some threaded rod now. I think I need 8 lengths about 8" long.
I really should be doing something 'productive' instead...
 
JBL used flower pots, plastic and "machet." Sonotube is also common, or PVC pipe with a cap.

Just glue it in with silicone from the rear. If it's a failue, cut it out with a utility knife; all that will be left is some silicone residue on the back of the baffle....
 
Zilch said:
JBL used flower pots, plastic and "machet." Sonotube is also common, or PVC pipe with a cap.

Just glue it in with silicone from the rear. If it's a failue, cut it out with a utility knife; all that will be left is some silicone residue on the back of the baffle....
Click to expand...

I'm using these cardboard tubes from the Wharfedale W60D speakers. They're EXACTLY the right diameter. I cut them down to 7" length. From a sheet of Masonite I cut a circle for the bottom, and drilled 7/16 holes to match the pattern of the bolt circle on the baffle. I cut 1/4-20 threaded rod t othe exact length to fit between the T-nut in the baffle and the back of the cabinet. I've threaded two rods through and against the back of the cabinet. Washers and nuts have gone against these to press the back on the tube. The seam is sealed with hot glue, as are the lead wire hole and the shaft holes. To seal the 'top' edge of the tube against the back of the baffle, I took a length of 1/2" backer rod, slit it halfway through and pressed it over the edge of the tube. This is a pressure fit against the back of the baffle from the force of the nuts against the back of the tube end. This is much cleaner than using glue in a confined space where I can't see what I'm doing. Other advantages: very rigid, can be disassembled, independent of the driver's mounting screws, braces the baffle against the cabinet back to some extent, wastes little space.
I did have to have one compromise: I'll have to drill new holes to mount the B-110 driver, but they will be small and can be filled in later if needed.
 

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One AR3/5A Frankenspeaker is done

This afternoon I finished assembling one AR3/5A Frankenspeaker. The Kef B-110 midwoofer has been screwed to the baffle and sealed. The cabinet has been heavily stuffed with poly batting and fiberglass. Each of the drivers has a pair of terminals on the back panel. This allows me to experiment with different amping and crossover arrangements. At the moment I'm running this single speaker biamped. A line level 18db/octave crossover is set at 200hz. The woofer is driven directly by one channel of an Accuphase P-300 amp. The mid and tweeter are fed by another channel of the same power amp, with 200hz high pass from the line level crossover. The amp high output goes to a passive crossover that is a copy of an LS3/5A circuit.
So far this sounds pretty good, but it's only one speaker and of course a pair will sound quite different. The second one will probably take at least 4 hours to properly assemble.
I'm eager to test the bass response. The cabinet volume is compromised by the midrange's back enclosure. I want to find out how this affects the woofer response. Luckily, I have this same woofer installed in an identical cabinet to compare it to.
I hope this works out to be something that's actually listenable. I really don't need more speakers, but it would be good if the time and (considerable) expense weren't wasted on the project.
More updates as things develop.
 

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