I can't help but wonder if the BMS 4550 is worth the extra cost over the DNA360? Does the BMS driver really add that much more detail and over all SQ to the top end?
What the BMS 4550 does is take advantage of lower crossover points - BMS recommends 800 Hz but that's for pro use, it can probably be crossed lower in a home environment. The DNA360 needs to be crossed ~1000 Hz or over. I suppose one might sound better than the other in similar implementations, but it's sort of apples and oranges. The BMS is currently enjoying a godlike reputation because it was used in the smaller JTR Noesis, a line of high-end HT speakers that are apparently very impressive to those that hear them. (Apologies if you already knew this.) I'd be more interested in a comparison between the 4550 and Erich's BA-750, which apparently can be crossed at 600 hz, only costs ~$150 and was measured in a SEOS 18 waveguide by bwaslo at http://www.diysoundgroup.com/forum/index.php?topic=31 edit: not a coax cd
FWIW, the Noesis doesn't use the 4550, it uses one of the BMS coax CDs like the[font=verdana, arial, helvetica, sans-serif] 4593ND or such.[/font] [font=verdana, arial, helvetica, sans-serif]Also IIRC, Geddes crossed the B&C 250 ~900 in his Summa with apparently great results. The 360 should be similarly capable. Considering the SEOS15 doesn't hold pattern below thereabouts anyhows, might not be worth worrying too much about capability below that.[/font]
Ops, seems I spoke too soon -- wasn't aware of the Noesis 228HT. Mea culpa. That confirmed to use the 4550?
As far as I know no one has directly compared the 4550 to the DNA-360. I am planning on doing a design for bass addict on AVS using the 4550, at that point I should be able to list my thoughts on how the 4550 compares to the 360. For sure DNA-360 can be crossed lower then 1000hz especially if you use a larger/deeper waveguide then the SEOS-12. I have used the DNA-350 in my synergy horns crossed at 950hz. Even the extra depth of the EOS-10 helps the bottom end of the 360, you could probably get 800hz out if it in that configuration. It is usually where the waveguide gives up directivity control and also where the woofer's directivity matches the waveguide that determines the crossover point if a DI matched design is the goal. Here is what the FR of the DNA-360 looks like in the EOS-10:
You know what? I spoke too soon too - I referred to the 4550 as a coaxial CD, and that isn't the case. The US Speaker web page for the 4550 refers to it as a coaxial in the HTML "description" tag, so the link in the top Google result says "BMS 4550 is a 1 inch coaxial high frequency compression driver". I've been taking that as gospel for weeks, and it was a goof by whoever put in the info for usspeaker.com. My bad.
Sweet, I look forward to hearing your thoughts. The majority of the CD comparisons I've seen end up falling into a general "4550 is more detailed/extended, 250 is smoother" kinda bucket. Granted, more recent DE250s (and the DNA-360) seem like they have a little more high end than the older DE250s, and who knows which vintage DE250s were involved in the comparisons. FWIW, I have a pair of poured SEOS15s headed my way and a pair of TD15Ms that just arrived (go go GB 2011!) that will be used with either the 4550s or DNA360s. I think Coctostan is still planning on whipping up a XO with his GB 4550s and TD15Ms and making that available, and then Bill's passive XO for the 360s has also been posted, so either way I should be set. I'll probably end up with the 360s and pocketing the extra $100+ unless Matt/Max come back saying that the 4550 is zomg so much more betterer.
How low does the Seos15 and the Seos12 go down to? Would they be ok down to say...800hz or perhaps 700hz? I looked at the Seos18 but it seems to only go down to 800hz, right? Do you think that the Seos18 with a BMS 4550 would be better than a Seos15, (or Seos12), with the same driver? Is the Seos18 or Seos24 available in plastic? All that I see are the fiberglass ones and they are super expensive! I would love to go with a pair of Seos24's with Radian 951's but that would be over $1,200 dollars for just the waveguides and CD's. I might consider that, though. What advantages does the Seos18 have over the Seos15 or Seos12? Is it just strictly a frequency responce thing? For example, the Seos12 needs to cross at 1k or more and the Seos18 can cross at 700hz to 800hz. I will likely just order the Seos15's or Seos12's and do a build with the DNA-360 and then sometime down the road when my business picks up at the end of the summer I could then purchase a pair of the Seos24 and a pair of Radian 951PB's with the Truextant Be diaphragms. Until then............
You can look at how low a waveguide can be used two ways. First is how low the frequency response extends with a given compression driver, there really is no easy way to determine this without measuring it. You can figure that a larger/deeper waveguide will have a more extended low end then smaller/more shallow ones. So in theory the SEOS-15 will extend lower with the same CD as the SEOS-12 would and same goes for the SEOS-18 compared to the SEOS-15. Second is at what point does that waveguide looses control over directivity. This is how the SEOS waveguides are rated, those minimum recommended crossover points are where the pattern starts to widen and is no longer controlled by the waveguide.