With all the outside forces pulling me away from these projects, I thought if I posted this in public, it might help shame me or otherwise pressure me to actually get my derriere in gear and put some focus on actually getting these things done......
Richidoo has built me a set of woofer cabinets that will form the basis for 4+ different speakers in one. His original woofer cabinet design plans are attached to this first post.
Basically, the idea breaks down like this:
- dual 15" woofer enclosure, each with it's own sealed enclosure space within the larger box... The same woofers will be used in all speaker designs.
- 4 separate 1.5" thick pieces of birch plywood "mounting plates" that are the same dimensions as the top of the woofer module. To those "plates" will be mounted a JBL 2509a adjustable position bracket (
http://www.jblpro.com/components/2500ser_02.htm). I have two pairs of the JBL2509a mounts for now, one pair for each pair of horns I plan to experiment with. To those 2509a mounts will be bolted one of two different horns and one of 3-4 different compression drivers. The "mounting plates" are substantial enough to be free standing. But they will be sitting loose on top of the woofer box, likely on some sort of isolation material (I'll experiment). whenever you want to swap the horn/CD combo being played, just lift the assembly off the box and put the other mounting plate assembly in place. Crossovers will be external to allow easy swapping of the horns and CDs.
Horns:
SEOS 24 1.5" entry horn/waveguide in black gel coat fiberglass finish from vendor in Poland:
http://www.diysoundgroup.com/plastic-seos-12/fiberglass-seos/seos24.htmlIWATA-300 2" entry horn/waveguide in black gel coat fiberglass finish from vendor in Poland:
http://www.diysoundgroup.com/horns/autotech-horns/iwata300.html I also have a pair of JBL 2352 1.5" entry cinema horns for $hits and giggles that can be used for comparison
Compression Drivers:
JBL 2446 2" exit compression driver with Truextant beryllium replacement diaphragms installed in place of the factory 4" titanium diaphragms.
JBL 2447 1.5" exit compression drivers with factory diaphragms installed (they were supposed to be for the SEOS 24s but the bolt pattern doesn't match and I'm not screwing with building a custom mount plate. I've got a pair of JBL 2450SL 1.5" neo CDs in a holding pattern that I could drop the other set of beryllium replacement diaphragms in to listen to on the SEOS24 horn. but I'm going to start with the BMS 4505ND CD listed below and make a decision later
BMS 4592ND 2" exit neo compression driver. This is a coaxial compression driver with a mid and high frequency diaphragm inside the same assembly. The manufacturer's reasoning is that it allows for much better high frequency extension, while also allowing a 400hz midrange crossover point on an appropriate horn. Each diaphragm can work within its ideal operating range without having to stress and extend beyond its capabilities. So with the appropriate horn you can get 400hz - >20K without having to resort to multiple horns and multiple CDs.
BMS 4595ND 1.5" exit neo compression driver. Again, this is a coaxial CD design to allow extension in both directions without the typical beaming or HF extension issues associated with a single diaphragm.
In the woofer cabinet, the top 15" woofer closest to the horns will be the Acoustic Elegance TD15M....
http://www.aespeakers.com/drivers.php?driver_id=4 ... This is a very efficent woofer that (if manufacturer specs are to be trusted) can easily extend up past 2K off axis before crossing over to the high frequency drivers. I don't intend to run them that high... but we'll get to that in a second. By running the TD15M sealed in this size enclosure, it's a nice overall Qts figure and it should start a nice controlled rolloff (before room forces factor in) at ~80Hz.
The bottom 15" woofer will be the Acoustic Elegance TD15H
http://www.aespeakers.com/drivers.php?driver_id=10 This woofer will be powered separately by a pro style amplifier that has DSP, EQ, and crossovers built in. The idea is that I will use it to essentially be my subwoofer/midwoofer and cross it in wherever the TD15M rolls off, as well as use the EQ to level out the bass response of the system as flat as possible in room. The bass load will also be taken off the TDB15m and horn system so that I can use lower powered amplifiers on that setup and let the solid state pro amp handle the heavy lifting down low... If boosting is necessary to flatten out the deepest ranges given the sealed enclosure versus porting it, no problem as it has enough Xmax to allow a little boost. I dont' intend to play the system at insane volumes. The idea is to explore high efficiency, low compression drivers and see if they offer any advantages over lower efficiency consumer options that are typically employed in a lot of commercial speakers out there.... basically try to build a speaker setup that takes advantage of some of Sol's lower powered amp designs, or some lower powered tube options out there.
The entire system has to be measured and crossovers designed for all the various incarnations of the horns and compression drivers available.... I'll be targeting as low a crossover point between the horn/CD and TD15M woofer as possible... but will ultimately settle on whatever crossover point sounds the best. It will likely be ~500Hz... time will tell. Regardless, it should still be in a range that the TD15M shouldn't strain to cover...
So far, the woofer boxes were designed and built on a budget thanks to Richidoo. They are 1.5" thick walls all around with MDF and 13-ply dense birch plywood laminated together to manipulate cabinet wall resonances... cabinets are braced pretty well by Rich, but I may add a few more after stuffing with the blackhole material, stuffing, and giving them a listen... maybe more cross and front to back braces if the cabinets still are not dead silent... Other than putting the casters on so I can roll these behemoths around, little else has been done in the couple weeks I've had them here..... I really have zero time to do these DIY experiments but I really want to play with them....... I'm going to play with some cabinet finishing techniques on these boxes first before doing anything else.... hopefully in another week or so, if I dont' get too much flak from the "Boss" or the inevitable slew of interruptions in personal life, I'll be ready to start the measurement process to commence crossover simulations/design.