dynamic dipole design opinions and issues

[thadman]

I was looking through lists of measurements and found that the Dayton Reference RS52 performs with incredible low distortion from 800hz-4khz, which makes a perfect crossover point for a ribbon tweeter which I've also been longing to integrate properly into a system. The 800hz crossover point is low enough to integrate with most low distortion 8s, specifically the Dayton Reference RS225-4. A pair of RS225-4s crossed at 800hz would provide enough displacement for high SPL with a relatively narrow dipole baffle (<300mm) and low XO point (100-150hz). I'd like to preserve dipole radiation throughout the bandwidth of the system, so as to preserve uniform power response.

I'd arrange them in this order (ie TMWW)

Fountek NeoCD2.0 (front and rear firing)
Dayton Reference RS52 (front and rear firing)
(2) Dayton Reference RS225-4

The 8s would be crossing to a pair of h-frame bins below them.

Are there any issues with front and rear firing dome midranges/ribbon tweeters?

Is the 800hz crossover point high enough for dynamic reproduction from the RS52 (limiting xmax/increasing power handling)? I'd like to be able to achieve high SPL with low distortion (105dB+), and feel the high sensitivity of the dome midrange coupled with a relatively high crossover point is the best solution for this. Am I wrong, would a cone midrange be more suitable?

[gtforme00]

I have a similar design planned with a Radioshack Dipole module on the top end! I'm looking for a suitable midrange as well.

For the RS52 there are no xmax or sd figures available, but for similar dome midranges I have found the following figures: sd: 26 cm^2, xmax: 1.3 mm p-p, .65 mm one way.

Putting that into Linkwitz's spl_max1.xls spreadsheet, for a 300mm baffle the max spl on axis for the RS52 at 800Hz would be 109 dB.

The SPLdipole=monopole frequency for a 300mm baffle is down around 389 Hz, so for all frequencies above that, the dipole configuration is actually helping the RS52 out.

Mind you, I don't know the exact excursion of the RS52 and this is just a simulation, but IMHO you would be safe running the RS52 down to 800 Hz.

David

[Hara]

The SPLdipole=monopole frequency for a 300mm baffle is down around 389 Hz, so for all frequencies above that, the dipole configuration is actually helping the RS52 out.

Note that the RS52 is sealed in the back, so it should function as a monopole.

[thadman]

Originally posted by Hara


Note that the RS52 is sealed in the back, so it should function as a monopole.

In my post, I mention that I'm using front and rear firing midranges (ie dipole RS52s)

[Hara]

Ah yes, I overlooked that.

[gtforme00]

The news gets better thadman. The 109dB SPL at 800Hz is only for one driver (dipole pair). The figure goes up 6dB for a pair (of dipole pairs) and up another 6dB if you include the 800Hz contribution of the woofer (with a LR4 crossover). This means that you can have up to 121 dB of 800Hz for your ear splitting pleasure .