OK, got a few minutes tonight to do a quick measurement on the BA/SEOS18 combination (both kindly lent to me by Erich). One problem: the mounting holes on the SEOS18 are spaced 3" apart (like on the DE250) but the BA's mounting holes are 4" apart (because of the larger diaphragm?). So, I measured with the waveguide placed on top of the driver, facing upwards. Just response so far, no distortion (I'm inside, with family, loud sweeps are not usually appreciated). Response, on axis, 1m away: Looks pretty healthy down to about 600Hz, which is great since the directivity of the SEOS18 should be good to around 650Hz. The high end looks quite sweet -- that's an essentially unsmoothed response (1/48th octave). Someone asked about the waterfall (I don't put a lot of meaning on WFs, but they're easy to do, so---): And the Impulse Response looks very nice:
Bill, most of the fiberglass units I got from Autotech don't have predrilled holes in the mdf flange. So the end user had to drill them anyway. I think Autotech did drilled some on the second pallet of waveguides, but I can't recall. I guess the one you're testing does have the predrilled holes for the smaller drivers. But there's no reason you can't go ahead and mark some other holes and get that BA mounted properly. It won't bother me at all. So does the BA have some nice speaker potential?
Bill, can a spectrogram be derived from that impulse response? I wanted to do an apples to apples comparision with the BMS 4550/SEOS-12 measurements done by jzagaga:
I see the BA is now listed at $1 and out of stock... any ideas on the final price? It seems like it would be a great choice for some unity horns. If my memory serves me correctly one of the reasons Tom Danley recommends the BMS 4550 is because of it's low fs. Crossing over a healthy distance from the fs of the compression driver prevents any phase issues when combining two drivers in a unity horn.... or at least that what I remember Tom saying : . Either way if the price was right it looks like a interesting driver.
The first ones I have are going to be around $150 each. That's cheap and they probably won't stay like that if I order more because shipping will be higher. All the CD parts came in on the container shipment, so shipping costs per item was very low. But if I buy more parts, they will likely have to be shipped on a pallet so shipping costs per item will be more. I just have to add in Paypal fees and packaging material. Should be around $155.
bwaslo, Any more numbers on the BA's? I put in an order for a pair to go with SEOS 18 and TD15m's. Have you done any work on passive crossovers for this combination yet? I might go active. Haven't made up my mind yet. Considering the [SIZE=small]Dayton Audio OmniMic V2 Precision Measurement System with the miniDSP.[/SIZE] ...Roy
Hi Roy, No sorry, I haven't neen able to. Been having some back problems (sciatica) so been out of any work that. involves lifting much more than a bag of apples. For a while it willl have to wait (unless we can talk Erich into mounting them into a box for me measure from). If you go active (Minidsp) then you can pretty much do it on the fly (assuming an Omnimic or other meas system).
Sorry about the back. Just the BA @ 10lbs could present a problem by itself let alone moving boxes around. I'll probably end up going active. I already have the amps so I wouldn't save much going passive and I'm rather interested in active and the advantages it has over passive. I might just build a bass bin and build a separate open back box for the waveguide so I'll have some flexibility for future experimentation. Looks like I'll need to beef up the WG flange a bit to support the BA. Perhaps I could integrate a metal (aluminum?) rear support bracket that would double as a flange strengthening solution.
If you already have amps and a preamp output on your receiver (or use an old school preamp) then you will likely find it to be less expensive to go the MiniDSP route. Decent big inductors cost real money. And you can get a nicer result (time delay - no problem! response ripples -trivial!), too.
Presently, my rig consists of a pair of rebuilt/modded Heathkit W5m tube (6L6, KT66) monoblocks...25W/ch. Class D audio 50/ch amp http://classdaudio.com/class-d-audio-amplifiers-1/mini-class-d-audio-power-amplifier.html. My pre is AVA T7 tube hybrid. I don't have an AVR. I'll probably use the Class D for the woofers. Tubes for the tweeters. The AVA pre has substantial gain. The nice thing about active is that if I change amps, I can go back to the miniDSP and make adjustments. It'll definitely be a learning experience.
Distortion looks good, but what's the dip ar 550Hz? One of the drivers not reaching or a phase cancellation?u
;D I got the BA-750 and the SEOS-18 today. Is this really a tweeter? Put a blindfold on someone and put it in their hands, and they'll tell you it's a 8" JL Audio etc subwoofer It'll be a while before I'll have mounting holes drilled, and put this driver in a real box before I go and do any real measurements (it's Day 2 of school already!) But I was hoping I could get to some rough fun simulating done in PCD, if you don't mind providing the files, Bill, for a TD15M + SEOS-18/BA-750? I suspect the apollo TD15 I got will have a different impedance curve though.
Sorry, I've never run files for the BA, just took some curve shots during early testing. You have new ground to break. (particularly if you drop it on said ground!)
I may have gone a bit overboard, but it is just the one project for the time being, so i'm sure it'll suffice As for the apollo, the extra power handling probably just doesn't matter at all. But I could not resist the extra two shorting rings :O
That sounds fun! Will these speakers be in the same room as your Philharmonics? If so, it will be interesting for me and presumably others to read your take on narrow(ish) vs. very wide midrange directivity after you build these speakers and get 'em dialed in.
Their final home is a much more narrow room where they'd take a big edge over the Phils. But yes, they will be designed in the same room as and A/B'd next to the Phils. I suspect they'll sound great on brass and wind, but I can't help but be skeptical of the doped titanium diaphragm. Once you've spent two months with the ability of the raal to paint high frequencies over a "black" canvas, it's hard to be willing to want any even mildly, inaudibly imperfect tweeter. I already want a Be Diaphragm for the BA-750 - and I have not heard it yet! O_O Not to drag this thread off-topic, but I'd really like to see a Boron Carbide option for this tweeter!
I'll second the request for a beryllium diaphragm for the BA 750. I've never heard of a Boron Carbide tweeter.
Boron Carbide IMO is a more cost effective option than Be while getting the majority of the performance. I think some alternate diaphragm options would really be welcome...
I agree. My attitude is since I've already spent the money on the best parts, (TD15M/ SEOS18/ BA750), I might as well go for the gusto and spend some more $, within reason of course, for the best diaphragm available. I take it that a different diaphragm doesn't require major changes in the stock BA.
