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How about these?
Winter project is to design an old school home theater speaker system. A TMM, a TM, and a possible even a MTM using those sweet 4" SB Acoustics OEM drivers and the round Fountek knock-off from GRS. I'll be reaching out to someone with a CNC and heated shop to help me knock together cabinets, but for now here are preliminary ideas. Everything was modeled with a pretty reasonable series resistance.
TMM using a pair of the 8 ohm. 1 cubic foot. F3 of 38Hz, little wavy on the bottom end but not at all terrible considering the 1db scale. Slender tower. Will likely be somewhat different on bottom end from modeled since I will stuff it 'til the tower resonance is minimized, similar to how I ended up with essentially an MLTL on Taiga. This could be built as a stand-mount, sealed, with an F3 of 79Hz in 0.5 cubic feet. This would integrate pretty well with a subwoofer in sealed mode.
And the proposed baffle (note: all three would have 1" round-overs. Performance difference between 3/4" and 1" should be minimal, I know 3/4" round-over bits are far more common)
Up next is the TM using the 4 Ohm version. 0.25 cubic feet. F3 of 49 Hz. Could also be built sealed with F3 of 93Hz, but that is pushing it fairly high for integrating with a subwoofer.
Here is the proposed baffle:
Lastly is a MTM using a pair of the 8 ohm drivers. 0.5 cubic feet. F3 of 79 Hz. Can be built as a tower with same cabinet dimensions as the TMM with the same F3 of 38Hz.
Proposed baffle in what would likely be the orientation it would see in a typical home theater:
The 8 ohm models very well from a cone excursion perspective, here is modeled cone excursion for a pair of them in the tower, at 10W input:
The little fellers have an advertised Xmax of 5mm, that helps. The TMM will not exceed Xmax until 37Hz at 92db when considering baffle step losses. This is phenomenal, in my opinion of course, for a pair of 4" drivers.
A 2nd order 40Hz high-pass raised F3 to 41Hz with a bit of a shelf:
Here is excursion modeled with 20W input:
This drives peak SPL to 94db when considering baffle step losses. This is pretty good since it would personally give me 6db of headroom at my loudest personal listening levels, and 12db at my typical listening levels. I imagine distortion remains very low at 82db peaks. Boundary reinforcement would offer useful bass below 30Hz. The MTM will have similar performance, of course.
If I get to the MTM stage, I will do one version with full BSC for people who like to listen to MTM as mains and one with maybe 3db of compensation for those who would use them as a CC.
I will definitely be building the TM and the TMM tower.
Note: these will not be all that inexpensive due to the overpriced tweeter but the performance will be there and my guess is my absolute value score on a scale of 1-10 (with 1 being an all Elipticor 3-way using their new midrange ((obviously a great performer but diminishing returns ruins the value perspective, not that people shelling out $2500 for a dome mid give two shits about value lol) and a 10 being that recent 3-way GRS design I did) these should fall in the 6-7 category due primarily to the cost/performance ration of the mid-woofers. Those offset the tweeter cost quite a bit.
I wish the OEM 8" modeled better, would make a cool matching subwoofer with a pair of the 8 ohm.
Comments
I've been awaiting your findings on the round GRS ribbon tweeter . . .
I was told that the GR$ version is the same as the Fountek. "Someone" purchased the Fountek tooling.
I was also present for that conversation. Ditto.
Without trying to be a downer, I wonder if those drivers will meld well. I just did a sim with the 4" coax of the PFCR series, and xovers below 3kHz are preferable for the woofer due to the response. I asked Chuck and he agreed. The broad dipping shelf before breakup makes it more "INTERESTING" in use.
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Wolf - Did you use just the woofer on the SBPFCR Coax or are you referring to using the entire Coax unit with an XO below 3KHz?
I suspect the former, where the XO was from the Coax woofer alone to the GRS round ribbon tweeter.
Just looking for some clarification, sir.
Being that the ribbons have a tendency to xover higher than domes, my guess is that they may not meet in the middle due to the tendency of ALL of the SB12PFCR drivers/woofers to have this kind of response profile.
While I did apply the coax tweeter as you suggest, my comments are still relevant.
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OK, so you did not XO the SBPFCR woofer to a GRS ribbon but extrapolated that the SBPFCR woofer had a dip that would preclude the use of the GRS ribbon at a suitable XO point then.
Possibly, yes. JR has the chops to do it justice if it can be.
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JR is a machine, for sure - thanks for the clarification.
Just a question... Are these for a specific use or just a fun design for others to make? If for others, would they work with the 0.23 cf and 0.56 cf Denovo knock-down cabinets?
Always been a fan of those PFC drivers - was even more of a fan when they came out with the round frames!
Unfortunately they didn't improve in FR as a result - not sure why . . . but they certainly are much easier to flush-mount.
JR, I like where you are going with these. I've been eyeing those little woofers for a while now. I don't know why, but I've been scheming about designs using 4" woofers for the past year. Now, I sure don't need any more drivers or speaker boxes at this point, but I may have to cave and order a quad of those little SBs.
They would work fine, the diffraction signature would be somewhat different than what I will account for in the crossover.
No specific use other than give people an option for a full ribbon tweeter home theater without the costs associated with designs like The Statements. I have no idea what I will do with whichever I end up building - probably gift them like I do with a lot of my designs.
Not seeing the broad dipping shelf:
In any event, these will be designed (as so many of mine are) for best performance with minimal toe-in. The off-axis of these is pretty controlled. It will be more than fine at the projected 4K crossover point.
For reference, check out the significant response difference between the "normal" driver and the coaxial:
What the charts show is the importance of compensating for removing a dust-cap.
I've been very busy with 4" drivers this year! I'm going to keep a friends CNC busy all winter too, if I want to get this killer 3-way built that I have been designing in my head the last couple years.
JR, I think you mistakenly showed the wrong FR plot. That one is for the 8 ohm version. The 4 ohm version is even better! Less peaking around 1600 Hz.
Oops! Rereading this thread I now see that you in fact are using both versions.
All I know is that Chuck said his pair had that broad dip too. These look a lot better than the coax and what he and I had discussed.
I hope they look more like these above, as that will be great and work just fine.
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Towers started.
Here is a screen shot from PCD of my measured response. Taken on the tweeter axis from about 1m IIRC. Tweeter was at 90db. Gated response of 5ms.
Not enough baffle meat !!! ~~
curious how you skin the front facing baffle
That ^ looks like the Coaxial woofer response - is this what the graph is about, sir?
1-1/8" stair tread material.
Nope, this is the raw woofer response of the 12PFCR-4 from my Kallah build.
Hmmm. Sure seems a miss for SB. I'm forging ahead regardless. I ain't afeard of any dip.
Got to thinking...(Woke up way too early this morning) and I do believe I am going to go with a traditional dome tweeter. I have one good Beast Mode© tweeter here, cheap enough to order a second. Only concern there is I hope these are something people will build, of course and given how Tymphany is giving us indications that they are pulling out of the DIY market I am afraid they will go NLA on us.
Another option is the venerable BC25TG, but same concerns there. Great budget tweeter IMHO.
Ideally, it should be a model that Meniscus sells or would consider selling. Not really soliciting opinions - just thinking out loud. I do not have any tweeters here but the single Beast Mode© that fits the bill. My tweeter collection is eclectic and range from several pair of AliExpress goodies (some cool looking AMT, a pair of ceramic dome that look promising, and those copper nipple and small form factor dome Vifa knock-offs), one last pair of the big Viawave ribbons, a pair of those huge Beston things that I have no idea why I bought them, two pair of TL with square faceplates, a pair of the Tymphany little horn loaded BC tweeters, those GRS ribbons. So other than the little Vifa horn thing there is only the Beast Mode© that fits the bill. Honestly, with the baffle width and 1" round-over I am using the horn-loaded Vifa would be great - except the fear of NLA happening. Maybe I will use it anyways, I'm not really a kit-chaser.
Anyways, gotta go to work.
Enough bracing for these little fellers. Going with XT25, classic.
Do you purchase dumbbells' in bulk to use in place of wood clamps to save money?
Is that stair-tread thickness (1-1/8") Particle board?
Stair tread, yes. I use the dumb bells because it is all the clamping force you need for cabinets.