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Best "bang for the buck 15" driver?

#41
I'm fighting for EVERY OUNCE(B-Square says I'm a tough boss)(HAH!). The target is under 25lbs, and so far we're on it! Hopefully we can actually hear the first cab this weekend. I have a couple amps to try out on it. One of my old Peavey mark 3's and a semi-old Trace 1215. If it sounds good or within tweaking range, we'll do the second version (with the Low B optimization). Once we get a couple prototypes working, I'll likely be hosting an open get-together "road-test" session for all interested testers and their heads....
Happy Thanksgiving. y'all!

Josh

PS: B-Square is a bit hyper-critical of the way the panels turned out. While not perfect, they are quite nice.
 
#42
Busy day today. The cabinet is curing up in it's fabulous Bellair clamping fixture till tomorrow morning. We were introduced to a very nice(to work with) carbon filled glue. It's very strong and light. Total of 300 grams used, including the inner fillet. Here are some pix from today's session.....

Josh

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#43
Just finished the first "loose fit and try/tweak" session with this cabinet. In a word "beautiful". Very "high-fi" for P.A. So much so that we gave it some time with a keyboard. It out-performs the Trace 1215(also single 15" driver/4" ports) extension cab it ran with. It's louder and a bit clearer, with more mids. We're quite happy, so far! I took it apart for finishing this week, and it will be presented to the SMWTMS meeting next weekend. From there, it gets fully measured. Bob will post the relavant results after that. I'm thinking I'll present it to some of the TB'ers in this area once we get the second cab done. Maybe an "open-house" type of thing. I'd really like to have it heard in person with a variety of equipment running through it(even keys!). Oh, yeah, so far it weighs 22lbs.!

Stay tuned!

Josh
 
#44
Before painting we are going to add bracing across the back and sides that will not add much weight but will be in the HI FI direction I am going. The Trace Elliot wooden cab vibrated the same as the carbon fiber and that is what I wanted to know before I went ahead and braced it. A guitar speaker is designed to create a "sound" but I believe for bass it should be a neutral "clean slate" to apply fuzz or phasing electronically to. We are doing this without a midrange to get clarity. This is where the "Bellair magic" comes in.
 
#46
Measurements will be made by Tom Nousane of Sound & Vision magazine. We will do on axis, 15, 30 & 45 degrees and the woof and tweet separately to see the crossover. Besides feq response we will putting velocity sensors around the cabinet to map resonances. And of course impedance. I will have him do his regular procedure to determine system efficiency.:smug:
 
#47
Ok a lot has gone down since the last post. Incredible response from everyone trying out the cabs. First thing is the output is around 101 db efficiency due to the carbon fiber construction and internal bracing (the 15" driver is rated at 98 db) The clarity is the first thing remarked about and there has been no other cab that has come close to it. It also works great as a keyboard speaker. The first one has two tweeters and the second has two 5" midranges. The tweeters crossover at 12 db/octave @ 3000 hz and allow some off axis notching from 1000 to 3000 hz in the woofer. The midranges crossover at 6 db/octave @ 1000 hz overlapping the woofer 4 db under woofer level and basically eliminate off axis notches. This off axis response difference has not been as important as people have stated but we are still investigating real world examples. The tweeters go out beyond human hearing (especially musician hearing) and the mids go flat to 10,000 hz. This all gives a little different "voice" to each cab and we are trying to get as many opinions as we can (still working on this). The main thing is the output that competes with double 15" cabs and the weight - 26 lbs plus the clarity that makes everyone call this a home run with bases loaded. The downside is the work, cost and time involved to do this. But they are beautiful! Pictures do not do it justice. I am now working on cheaper composite construction ideas and making a three way system next. Anyone interested in trying these cabs out? We also encourage anyone to bring their equipment to compare.
 

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#49
One cab is in Eastpointe Mich and the other is in Livonia. I just found out the 15" driver's specs have been changed and it is listed at 100.8 db efficiency so the claim for Carbon Fiber increasing efficiency is not valid. Oh well it still sounds great and kicks ass.
 
#51
The finish is a two part paint that can be applied very thick to get the mirror finish. Unfortunately the Carbon fiber has many little holes in the surface where the resin has not completely infused and capillary action sucks the paint into them. This requires many coats to fill them and I was not around during this process so 3 to 4 coats were applied. This resulted in an additional 6 pounds to the cabinet. The two mid ranges and grills also made this one heaver than the first cab and it ended up at 32.5 lbs. Oh well it still sounds great but not crazy light as the first.
 
#52
Bellair Audio said:
The finish is a two part paint that can be applied very thick to get the mirror finish. Unfortunately the Carbon fiber has many little holes in the surface where the resin has not completely infused and capillary action sucks the paint into them. This requires many coats to fill them and I was not around during this process so 3 to 4 coats were applied. This resulted in an additional 6 pounds to the cabinet. The two mid ranges and grills also made this one heaver than the first cab and it ended up at 32.5 lbs. Oh well it still sounds great but not crazy light as the first.
Click to expand...

You can and probably should use spot putty and/or Bondo to seal the pinholes before painting if lightest weight is a primary design goal? I used to do sailboard repairs and in that case pinholes are really bad juju since they can allow water to get into the foam core.

Cool build. I've had some similar ones on my to-do list for a while now. Gotta get rid of some cabs before I even think about building any more though...;)
 
#53
I have not found a clear putty or Bondo or I would have used it. I am now building a cheaper composite using wood instead of carbon fiber or Kevlar. It will be a three way with one midrange and two tweeters. As soon as it is finished we will hold a "open house" and jam session to identify the best sound direction to go. This one will be in the 35 lb range but far cheaper.
 

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