OffTopic (Drive Units)

by Bert , Wednesday, April 18, 2007, 18:23 (6211 days ago) @ Jose Hidalgo

Jose,

Just a reminder for Bert, if he comes across this topic. I'd like an
answer to the following questions please :

Sorry, missed that one while the "war" started in that topic. Somehow the new messages posted within that topic doesn't show on the threaded topics list....the reason for moving your questions to a new topic.

1°) 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 of the BD15 (6mm, is it right ?) will be exceeded before 30 Hz in
that case. 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 well under 30 Hz. Wouldn't that be
better for us ? Or do you see other problems with a smaller enclosure ?

Xmax is 7mm. If you would build a dampened reflex enclosure then the group delay isn't so bad.... the bigger enclosure gives a nice gradual roll-off which can be EQ-ed more simple and less strong (saving some power on the amps).

2°) One last question : does someone have some measurement graphs for the
DB15 ? We'd really like to have a look at the response, distorsion and
impedance graphs for instance. I hope it's possible. Thanks in advance.

I never did any distortion plots on the BD15's so I can't help you with that. I am sure that they will give a lot of second harmonic distortion when they are moving a lot...

My ears made the selection for the used paper cone, stiffness, surround, spider, coil (and former) and magnet strength. I have had several prototypes here and the BD15 came out most balanced in terms of audible distortion and dynamical behaviour related to the Q, etc.

Bert

--
BD-Design - Only the Best!

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