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SLeeperz . . . .
Dang, I went and did it again - got an idea in my head for these old Acculab speaker cabinets and bought a bunch of drivers/stuff.
Seemed like a great idea at the time of purchase . . .
The cabinet(s) is a 1.7 cu ft gross-internal Acculab (not expensive but well constructed) --> https://duckduckgo.com/?q=Acculab+speakers&t=brave&iax=images&ia=images&iai=https://i.ebayimg.com/00/s/MTEyMFgxMTEw/z/GawAAOSwdQhf6ava/$_58.JPG
Exterior dimentions = 25.5" H x 14.25" W x 10.75" D . . . Stand mounts . . . maybe with a hand-truck built-in? (The Drivers are very heavy).
Woofer (XO @ 800 Hz) is 96 db and is 3 db-down at 55 Hz using Win ISD in 1.5 cu ft net volume (after drivers, ports and bracing installed) - I selected this one --> https://www.parts-express.com/Dayton-Audio-PA310-8-12-Pro-Woofer-295-032
Cabinets get 2 each of these ports on the back somewhere --> https://www.parts-express.com/Port-Tube-2-1-2-ID-Adjustable-260-386
Midrange (Bandpass 800 ~ 4 KHz) --> https://www.parts-express.com/Timpano-Audio-TPT-D250X-1-Exit-Phenolic-Compression-Driver-294-3348
Horn has a cutoff freq of 700 Hz for the Mid ^ above --> https://www.parts-express.com/Celestion-H1SC-9040-1-Exponential-Horn-90x40-1-3-8-18-TPI-294-2948
Tweeter is --> https://www.parts-express.com/Timpano-Audio-TPT-DH175-1-Exit-Plastic-Horn-with-Dome-Compression-Driver-294-3352
(These are threaded and will be installed on the following horn --> https://www.parts-express.com/B-52-PHRN-15-12.5-x-6-Plastic-Horn-Waveguide-299-2309
XO's will be done active with the MiniDSP 4x10HD unit initially and if I don't break my back moving the finished speakers will be looking for some passive XO's later.
These should pack a punch in a compact box.
Any feedback/thoughts/guidance welcomed.
Comments
Cabs look the part. Why put the tweeter in a bigger horn than the mid?
Cut-off freq / available horns . . .
Upon closer inspection, looks like the depth is the difference.
The tweeter horn looks redundant with the midrange horn. The horn cut off frequency is based on the perimeter of the horn mouth. The cut off determines where you have pattern control down to, it doesn't guaranty the compression driver can get that low. I'd definitely measure those horn combinations on a dummy baffle before committing to a 3-way.
It reminds me of a Klipsch Heresy, a speaker I have always though was cool. Nice project, I get the three way idea. A set of short angled stands would be just the ticket.
Kinda what I thought on the mouth opening, haven't dabbled enough with them. I think I'd be inclined to roll with the horn already on the tweet and use a large opening horn for the mid. I kinda question their assessment of "cut off frequency" per horn lens.
The Freq Response/range of the two CD's are different.
But your guidance is noted - thanks.
The small horn (comes with the tweeter) on the tweeter CD is 45* horizontal dispersion pattern and the horn selected for the Mid CD is 90*
Wont using the two different dispersion pattern horns create a narrow listening window?
The speakers will be used in fairly small rooms and not from very far away (3 ~ 5 M)
Yes, the real difference in the horns' size and dispersion is the depth of them - I suspect efficiency/air coupling is greater with the deeper horn.
This one looks more like a wave-guide (in my hands) than a horn thus its much more shallow depth --> https://www.parts-express.com/B-52-PHRN-15-12.5-x-6-Plastic-Horn-Waveguide-299-2309
Ideally, the wider horizontal dispersion of the midrange horn would match nicely with the woofers dispersion at the crossover frequency. The mid horn might well be narrowing at the top end and hand off nicely to the 45 degree tweeter dispersion.
Billet raises a good point. Without measuring, kinda in the dark on the dispersion characteristics.
Beauty!
Looks like the Woofer to Mid XO @ 800 Hz is going to be just fine and the XO @ 4KHz from the mid to Tweeter will be fine if I flush mount the Mid horn and surface mount and over lap the Tweeter horn rim.
Sweet.
Gutted the cabinets and the knock test reveals how resonant they are - no internal bracing and ring like a dull bell.
I also underestimated the cabinet volume - they are actually 1.5 cu ft so I am going to need to add a box extension to bring them up to around 1.8 cu ft to get the F3 of 53 Hz I had modeled.
I wonder if I line them with Kilmat and foam over that once I add a few braces if it will dull them more . . .
Off to the shop to break out the routers to cut the existing baffles out while the weather is good and make a mess outside . . .
OK, got ahead of the days heat and this was more work than expected (pics can speak from here out) -->
Pic1
Pic2
Diatribe:
Got about a shovel full of sawdust out each cabinet - no way I would have done this indoors in my shop.
The little cyclone separator from Onieda is good kit for clean-up.
.
As far as I can tell, I tried pretty much your identical midrange cd/horn combo and was less than impressed.
The CD and horn were technically different brands than yours but all the "D250X" appear to be clones of each other or from the same manufacturing plant, just with different brand stickers.
The horn was a knockoff from ebay, but had identical dimensions and appearance to the H1SC-9040 (right down to the little reinforcement ribs)
Basically the horn would chop off anything above about3khz for any CD I put on it. Those results actually led to me dumping the 3-way idea I had and just going with a D220ti/H812 combo for a 2-way instead.
YMMV, but I highly suggest measuring the response before committing.
Ill see if I can get a screenshot of my results.
Ugh, it was even worse than I remember. At one point I added some vinyl peel and stick deadening to the horn to see what that would do. I don't remember if this measurement was before or after that.. but I don't think there was much real gain.
The D250X may work OK in another horn, but by that point I found the 2nd one was dead and I just cut my losses and went a different direction.
Hey Drew!
Thanks for chiming-in here on this project with your observations.
I am definitely interested in seeing your results/screenshots.
Did you break-in the CD's at all with some play-time on them and concerning the horns cutting-off the mid CD's around 3KHz - was this on-axis or what?
I was hoping to push the mids to over 4KHz and let the tweeter CD pick up the rest . . .
I guess I will put the cd's and horns together and sweep them here soon before I do a bunch of baffle work.
I have a pair of ESS AMT tweeters coming this week so I may just go two-way and skip the horns/CD's on this build if they aren't going to work out.
Thanks, man!
Steve.
Wow - that sux!!
Got me concerned that I may I have some useless parts . . .
No, I didn't really do much break-in. I don't know that it would make all that much of a difference. The measurements were on-axis. Also with no baffle, but that seems common for basic horn testing.
I think the biggest issue was that horn itself. I tried a couple other CDs on it but they both took a very similar nosedive around that 2.2khz mark. Here was the D250X on a different horn..
So there is atleast some hope for the driver itself.
I'm in the same boat as far as useless parts. But fortunately I bought the UMM-6 measurement mic just before proceeding too far into the build. If you don't have a mic yet.. I'm sure you can see how useful they are.
I do have the Omni-Mic set-up - thanks again for your insights - hopefully, I will have better luck with my stash of parts in my space - I will keep you posted.
After more modeling in WinISD I find that I am gaining nothing worth the effort by spending the time/energy trying to increase the cabinet volume beyond the 1.5 cu ft it already has with this woofer since everywhere I plan to listen to them already has a subwoofer for the bottom octave.
Additionally, I think it best that I move the mid and tweeter to a separate cabinet placed on top of the woofer cabinet which will make my life easier concerning further driver experiments.