Choice of BD15 for our High-end Hifi project? (BD-Design)

by Jose Hidalgo , Monday, April 16, 2007, 01:07 (6229 days ago) @ Bert

Hi Bert, thanks for that quick answer.

This depends if you want to use a subwoofer below or not. Without
subwoofer a dampened 165-225 liter reflex system with relative large ports
would be the best choice for the BD15 (even better with a matrix inside).

Well, there will eventually be a sub (a real one : JBL W15GTI, Adire Tumult, Beyma 18LX60...), but we'd prefer to use it only for HT applications. For Hifi, if the BD15's can go low enough, why would we want to turn on the sub ? I believe that in most music CDs there's almost no information below 30 Hz (provided you don't listen to big organ music of course). Take a look at these five graphs ( http://petoindominique.fr/php/caisson.php , scroll down the page). No problem if you don't understand french, the graphs are self-explanatory !

So we would have two separate Ozone configs : one Hifi config, without sub and with a low crossover for the DB15 (about 30 Hz), and one HT config, with a sub and with a slightly higher crossover for the DB15 (about 40-50 Hz).

It is not possible to get a BD15 with a lower impedance. These are not 20
ohms either (15ohm flat with impedance correction) but still, you are
making an active system, so what's the problem then?

All right, 15 Ohm is good. The only eventual problem was related to our DIY amplifiers' max power. I have contacted their creator, and he has just answered me at the moment. In fact they can deliver 160W/8Ohm and 80-90W/16Ohm. Theoretically (WinIsd), with a BD15 @ 80W in a 165L BR enclosure tuned @ 38,9Hz we can already get 105dB @ 30Hz, so that should be enough for a Home Hi-Fi application, even a High-end one. :wink:

Regarding the enclosures, your BR enclosures would suit us well. However, I have noticed (WinIsd) that a big BR enclosure (165L or more) will create a lot of group delay under 60 Hz, while allowing us to gain very few SPL (which we don't want since we're already over 105). Moreover, the Xmax (6mm, right ?) will be exceeded before 30 Hz. A smaller enclosure (120L ?) would allow us to have less group delay, at the price of a single dB @ 30 Hz (104 instead of 105 - big deal ), and with an Xmax exceeded under 30 Hz. Wouldn't that be better for us ? Or do you see other problems with a smaller enclosure ?

One last question : does someone have some measurement graphs for the DB15 ? We'd really like to have a look at the distorsion and impedance graphs for instance. I hope it's possible. Thanks in advance.

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