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In Reply to: RE: There is another option! posted by John Marks on April 09, 2022 at 10:59:39
The 2,5 way can be made using the same woofer and tweeter as the 2 way. Giving the manufacturer two different products from the same tweeter and woofer stock of parts, just using a change in crossover and the cabinet.
But the main selling point of most 2,5 way loudspeakers is louder bass!
Follow Ups:
Might get 2 to 4db that way depending on midbass used
Topmost woofer crosses to the midrange. Middle woofer fills in the baffle diffraction loss. Bottom one supplements the other two at the very lowest frequencies, increasing bass extension a bit.
A clever and complex approach, and apparently successful judging from the reviews. Only trouble is, all three woofers are in parallel at the lowest frequencies, resulting in a wicked-low impedance. Only high current muscle amplifiers need apply.
Didn't know if at least one (say, the upper one) could have a little higher intrinsic impedance to help with the overall impedance when all are in parallel? Or would that cause problems?
Mark in NC
"The thought that life could be better is woven indelibly into our hearts and our brains" -Paul Simon
JA's measurements, linked below, show an impedance minimum of 3 Ohms around 120 Hz, and a broad band slightly above 4 Ohms from 300 to 700 Hz. This is consistent with three nominal 8 Ohm woofers rolled out at different frequencies.
whether woofers with a bit higher individual impedances could be used in order to raise that 3 ohm combined minimum a bit. Not referring specifically to this speaker model, but a theoretical but similar design.
Just speculating.
Mark in NC
"The thought that life could be better is woven indelibly into our hearts and our brains" -Paul Simon
Your suggestion will work and has been used in speakers before
But to do any serious change to minimum, all three drivers would need to be to 12 to 16 ohm to even have a chance of getting 4ohm minimum (including most xover designs)
Madisound had some 16 Ohm, 6.5" Silver Flute woofers awhile back, but they sold out while I was still sketching out cabinet and crossover ideas for them.
I honestly don't know of any others that are readily available.
Nt.
Mark in NC
"The thought that life could be better is woven indelibly into our hearts and our brains" -Paul Simon
Yes, I know that the usual 2.5-way uses identical woofer-mid and woofer drivers; the difference is the inductor on the low woofer.
But (even though it was about 25 years ago) I think I remember that because they were making their own 7-inch drivers, Wilson Benesch had the luxury of being able to specify different compliances for the upper and lower 7-inch drivers surrounds. IIRC.
One thing I forgot to mention was that in the 2.5/TMM DIY kit I recommended, another function of the lower woofer is to raise the efficiency or sensitivity of the woofer function as a whole which means that the very efficient ribbon tweeter has to be padded down less radically in the crossover.
IIRC, the Fountek NeoCD3.0 ribbon tweeter is 93dB sensitive, and it is very hard to find a conventional woofer that is that sensitive.
atb,
john
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