Compact 3-way questions (Seas / Scanspeak)

[scudinc]

5th element, Thanks for your very detailed post.

I can see the points you have made, especially about low distortion of the Seas Excel magnesium cones. After searching a lot of websites I can see the Seas driver is likely to have 6db~10dB less 2nd+3rd harmonic distortion than the Scanspeak 10F/8424G00. Probably a much bigger difference in intermodulation products if my high pass filter is letting too much bass though. However I'm not going to settle on the W12CY001 partly because its sensitivity is only 84db/2.83V. I'm worried by the time I include a complicated band-pass filter I will actually drop voltage across the filter and be running out of SPL on the midrange driver. I also need to crossover at 3kHz with LR4 slopes, so I would need a RL trap for the cone resonance.

Any 7" woofer is going to limit your SPL sooner than any mid, even the 10F. See 5th element's spiel above.

Right now I'm probably looking at the Scanspeak 18W/8431G00 Bass driver (8 ohm). I'm reluctant to pay almost the same amount for a Satori branded driver, unless there is a clear advantage. I admit I haven't studied distortion plots yet.

Regarding woofers, the SB23MFCL45-4 has >87 dB sensitivity and would work in a 25 L box (passive radiators would be advisable). It has very low distortion and surprisingly wide bandwidth. Also consider the SS 18WU woofer with a Peerless (neé Vifa) NE123W mid.

I was interested in your comments about Eton. Do you know if the Eton 4-212/C8/25 would retain similar advantage to their no obsolete midrange? I feel a bit suspicious there could be some nasty cone breakup mode that doesn't appear on the data sheet. I found some other carbon fibre drivers had that in the past.

Another driver I overlooked for some reason was the Seas MCA12RC. It has a larger surface area than the Scanspeak 10F, so that can help distortion. Its 86dB/2.83V is probably ideal to combine with the 18W/8431G00. It looks like it should do the same or better job than the Scanspeak 10F. Please let me know what you think.

The Eton 4-212 has been tested, and so has the SS 10F. The SEAS mid is not going to have lower HD than the SS, but it is a competent mid and better value than the Eton.

This guy has tested several of the mids that have been mentioned. His tests are a bit inconsistent and incomplete but you should be able to compare within the set. That discontinued Mg cone Eton was very good, but the newest iteration (with Eton's sandwich cone) appears somewhat disappointing.

 

[John_wr]

I measured 10F in prototype cabinet with 22W and D2004, see results here:
hififorum.sk • Zobrazit tema - Ze zvedavosti - regalove tripasmo 8+3+0.75 Scan Speak
It was not finished, I had too many projects running in parallel. If I were doing it again, I would have used tilted baffle to allow for LR2..

Hi Pida, your 3 way design looks quite good. Did you use any modelling to decide the placement of the drivers on the baffle? Otherwise it seems quite fortunate you got a nice smooth response. I have some software for modelling diffraction, but I'm not sure if I can trust it.

 

[John_wr]

Scudinc, thanks for your suggestions and the links to test results that were useful to me. So far it looks like the 10F/8424 mid is going to work well with my choice of 18W/8531 woofer. I expect it will be loud enough for my usage at modest SPL. I prefer to keep the narrow baffle dimension as an aesthetic consideration so thats the reason I wont have anthing bigger than a 7" woofer. Vifa NE123 also looks good, but the 10F seems a bit more refined for use as a midrange and seems like a good match with the 18W woofer.

 

[John_wr]

Baffle diffraction simulation of Scanspeak 10F

Here is a simulation of the baffle diffraction for the 10F/8424G00 midrange placement. I'm not sure how accurate it is. Any ideas or comments?

 

[PKAudio]

Yes, Basta and VituixCAD. It was quite wide baffle for tweeter and small mid. I had to balance horizontal offset of mid and tweeter. I wanted to have drivers vertically aligned, and optimal tweeter offset was not optimal for mid, and vice versa.

Hi Pida, your 3 way design looks quite good. Did you use any modelling to decide the placement of the drivers on the baffle? Otherwise it seems quite fortunate you got a nice smooth response. I have some software for modelling diffraction, but I'm not sure if I can trust it.

 

[John_wr]

Yes, Basta and VituixCAD.

I will have to download those so I can compare results. There are some interesting projects on the VituixCAD website as well.