I have a pair of Tang Band W6-789S 6.5 in. mid-woofs looking for gainful employment. I was thinking of using them in some largish bass reflex wooden bowl speakers, but got intrigued by the article on the Omega Quarterwave Reflex in the Oct 03 issue of AudioXpress. I was thinking of using these drivers either in the Omega or a Metronome with single order crossover to a tweeter at, say, 10k or so. Comments on the pros and cons between the two speaker types? Not really full range, but almost there...
Omegas are a blanket approach to stuffing a driver into a box, each metronome is tuned for the specific driver.
IMO, a Met is prettier too.
dave
Note: i helped Rick with that article (graphics, proofing, suggestions), there some things in it i objected to, do read the follow up letters to the editor
IMO, a Met is prettier too.
dave
Note: i helped Rick with that article (graphics, proofing, suggestions), there some things in it i objected to, do read the follow up letters to the editor
Very shortly after the article, probably in the 3 or 4 months following. They were mostly "political" not technical, ie claims to have invented things that had been around for some time.
Omega is a generalized approach that will work OK with any driver as opposed to a specific solution that will get the most out of a specific driver.
Note for instance the driver offset....
dave
For what it's worth I built a pair of Omegas for Peerless 831882 5.5" and am pleased with the results. Selection of the speaker is critical in determining box size which can be huge (Tall)in many cases.Planet 10 is right in noting the furor that the article created although it doesnt lend any help in improving the design . I trust Rick .. He's been around for a while.
I ran through the numbers in a preliminary fahsion for an Omega using the Tang Band 6.5" woofers, and the inital results give me cabinets nearly 6ft tall and 130 in^2. This sounds plausible, but I may need to check to see if the equation a grabbed from the article is correcly parsed, as it has some ambiguity that could have been solved by a sprinkling of parentheses.
Well, WRT an OQR: fiberglass damping = 62.22in long, pipe CSA 173.676in^2, vent CSA 17.368in^2, stuff 0.367lbs ft^3. Polyfill damping = 67.1in, pipe CSA 135.081in^2, vent CSA 13.508in^2, stuff 0.735lbs ft^3.
An MLTL (well, one way of doing it at any rate) would be 52in, CSA 102.26in^2, Zd 19in, Zp = 50.5in, vent = 3in diameter x 1.25in long. Line top, back & one diade to just below the driver with 1in acoustic fiberglass, wool carpet underlay or similar.
Metronome = 60in, Zd = 30in. St = 8in^2. Sl = 125in^2. Vent = 3in diameter x 1.25in long. Same damping as MLTL. See different attached plots. Adjust the vent & damping on all to tailor the response to suit.
OQR is just one set of alignment tables. Does the job; not ideal IMO.
An MLTL (well, one way of doing it at any rate) would be 52in, CSA 102.26in^2, Zd 19in, Zp = 50.5in, vent = 3in diameter x 1.25in long. Line top, back & one diade to just below the driver with 1in acoustic fiberglass, wool carpet underlay or similar.
Metronome = 60in, Zd = 30in. St = 8in^2. Sl = 125in^2. Vent = 3in diameter x 1.25in long. Same damping as MLTL. See different attached plots. Adjust the vent & damping on all to tailor the response to suit.
OQR is just one set of alignment tables. Does the job; not ideal IMO.
Attachments
My numbers for the OQR with polyester stuffing came out pretty similar to the ones cited above, so I must have interpreted the equation in the article the right way - quite a cabinet for a leetle 6.5" driver.The OQR seems to have a teensy bit more low end extension than the other two alternatives, but not enough to get me really hot and bothered. The big thing the OQR ha going for it is straight lines, suited to my rudimentary woodworking skills. I'll have another look at the Metronome, though, to see if I can figure out how to do one.
The Tang Band mid-woof reportedly has a really benign high-end roll-off well suited to a versatile tweeter and low order crossover. Is this for real?
The Tang Band mid-woof reportedly has a really benign high-end roll-off well suited to a versatile tweeter and low order crossover. Is this for real?
As I said, a teensy bit different. Why the Metronome, then? I have absolutely no WAF concerns. Don't get me wrong, I've heard a Metronome at BA1 using an 8" hemp driver that sounded very nice (I even got to play it with one of my amps). However, what would be the compelling difference between this and the OQR?
how's about you build 'em all, get some help with a blind listening session, then try to decide?
Appearance, primarily. That's the Metronome's forte.
For the rest, I could have tuned the others for a lower Fp or done one to squeeze out a few Hz extra extension had I felt so inclined. I didn't. They're all tuned about as low as I'd take it in a vented box, and you're unlikely to notice any difference in LF extension between the three in practice. Theoretically, the MLTL (remember the OQR also falls under this catagory; it's just a specific simplified variation) should be the more accurate generally; it doesn't need anything like as much damping as the OQR either, so it should sound rather more lively. It's a bit smaller too. YMMV as always of course.
For the rest, I could have tuned the others for a lower Fp or done one to squeeze out a few Hz extra extension had I felt so inclined. I didn't. They're all tuned about as low as I'd take it in a vented box, and you're unlikely to notice any difference in LF extension between the three in practice. Theoretically, the MLTL (remember the OQR also falls under this catagory; it's just a specific simplified variation) should be the more accurate generally; it doesn't need anything like as much damping as the OQR either, so it should sound rather more lively. It's a bit smaller too. YMMV as always of course.
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