Where does the SEOS12 start to lose directivity?
I am bound to the smaller dimensions in my home theater but not for my living room system. WAF falls off sharply for the SEOS12.
The SEOS 10 is probably fine down to 1400hz, but it's not holding it's pattern as well. Those graphs make it look like it's holding pattern down to 1khz or lower. The SEOS 12 managed a lot better for me, like 1khz before it blew up. The SEOS 10 has some directivity left over around 1400hz, but not like that graph appears.
Do you have Bill's post handy? I wonder how the WG was mounted, that little wrinkle at 1400hz around -10db makes me wonder if some diffraction effects aren't contributing to the directivity. Also, the axial response looks -3db there. So ya, the -6db point looks about 45 degrees there in those charts, but that doesn't really match what I was getting. Maybe I screwed up
I crossed to a 10" woofer around 1500hz with mine. The blending of the narrowing woofer and widening waveguide worked out fine. So yes, no problem there. Just compared to the SEOS 12 which firmly held directivity down to 1khz, it's quite different.
Do you have Bill's post handy? I wonder how the WG was mounted, that little wrinkle at 1400hz around -10db makes me wonder if some diffraction effects aren't contributing to the directivity. Also, the axial response looks -3db there. So ya, the -6db point looks about 45 degrees there in those charts, but that doesn't really match what I was getting. Maybe I screwed up
I crossed to a 10" woofer around 1500hz with mine. The blending of the narrowing woofer and widening waveguide worked out fine. So yes, no problem there. Just compared to the SEOS 12 which firmly held directivity down to 1khz, it's quite different.
It's 13.5" wide, and only 6.5" tall, so it looses horizontal directivity around 1000 Hz and vertical directivity around 2300 Hz.
Should be in the middle between the SEOS 10 and 15
.Attachments
Last edited:
I would personally recommend the BMS 4540ND, or one of the JBL compression drivers that offer some refinements on the BMS ring radiator design. (Basically JBL sells some ring radiators that are very similar to BMS, but the phase plug is different.)
I am too lazy to walk to the garage to get the part number, but I've posted some threads on it here.
Here's a list of reasons why I would go with the JBL:
1) The JBL has a smaller diaphragm, and the smaller diaphragm extends the high frequency response and improves the cumulative spectral decay
2) The JBL would NOT be a good match for a low crossover point, but you won't be using a low crossover point because you are not using a large waveguide. With your 10" waveguide you're probably looking at a crossover point of 1350hz or so, and the JBL works fine for that xover. If you were using a 15" waveguide and a 900hz crossover the BMS 4550 or the B&C DE250 would make more sense.
3) The JBL is cheaper.
Here's my experience with these:
I have some Gedlee Summas here with the DE250, some homebrew Synergy horns that are a work in progress that use the JBL*, my old car used the BMS 4540ND.
* http://www.diyaudio.com/forums/multi-way/244508-monster-massive-9.html
** Creating The Perfect Soundstage - Car Audio | DiyMobileAudio.com | Car Stereo Forum
The consensus was that there is little difference between comp drivers. I bought the BMS 4550 for its greater power handling and low end extension. This may one day be more important as the one constant of this hobby is that you will build another system one day which may one day make use of these qualities with a bigger WG. The rest of the specs indicated more efficiency, less distortion down low, and more extension up top. If these differences are irrelevant then the only thing hurt was the cost which was irrelevant to me. I saw nothing that showed anything being a short coming for the BMS. People who have it have no complaint.
It already shipped so I will play with it with some mid-bass drivers to see how a various crosses sound with it.
Thanks for all the input.
It already shipped so I will play with it with some mid-bass drivers to see how a various crosses sound with it.
Thanks for all the input.
Terry,
The VHF level of a compression driver on a constant directivity horn or waveguide may be as much as 10-15 dB lower than mid band, which may be similar sensitivity as a 10" driver.
So while the compression driver's midrange needs attenuation, it is common to use a HF capacitor bypassing the attenuation pad, the driver running "wide open" up high.
Art
Art is correct here. In my systems the DE250 just makes the passband level of the system at 10 kHz. If its sensitivity were lower then I would have to pad out the woofer. This is only going to be true for a true CD system. A horn that beams at HFs won't have this problem so you may not see it in practice depending on how well your horn/waveguide can hold CD at HFs.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.