How low does the BD15 go with your enclosure (BD-Design)

by GC, Wednesday, March 07, 2007, 06:40 (6271 days ago) @ finecognac
edited by GC, Wednesday, March 07, 2007, 09:09

I wonder if I need a seperate sub to extend them down to 20Hz

Thanks

It is of course interesting to discuss the theoretical "How low does my woofers go"?
And it certainly also have an influence on how "big" you may percieve your sound stage. E.g.: a concert hall.
If the michrophones used for the recording goes low, they will catch any rumble appearing in the concerthall acc. to it's own abilities in the lows.

A studio recording will likely have a cut off around the 20 Hz as many instuments are plugged directly into the mixer etc. and the digital equipment often cuts at 20 Hz as well.

Now having said that, and there are of course much more to be said about it (here I just keep it very simple), it is a completely different case when we talk about "how low" when we place a bass speaker in our living rooms.

We have a box in box situation here.

True is that the cut off is defined by the cabinet and the Fr of the used driver etc; but forgotten is very often the rooms own amplification of the bass.

Most rooms shows a 12 db/oct rise (amplification) from approx. 200 Hz and down. Just check that by meassuring with a mic in you listening position and compare to a close mic meassurement (1 cm from the woofer).

Taking this fact into account a well designed speaker also have to take that fact into account.

There is no point in designing a flat down to 10 Hz speaker. It will sound awefull. Too much bass spoils the musical event like a thick fog of over preassure overlaying the whole sound.

The cab and the driver together should form a relative low Q, meaning a soft roll off, and best is around 12 db/oct roll off to compensate for the similar rise of a given room.

The BD15s are excactly low Q'ed enough to provide linear bass down to the "enough point" in a "normal" room given the right cabinet. (The SWING cabs as example)

I have a room cut off here around 15 Hz. Enough to picture Royal Albert Hall fantastic acoustics and the size of this enourmous hall. And enough to simulate a 10 Hz tone from a crazy synthesizer. The brain will sample down the missing octave and fill in the gap, should the speaker/room be unable to produce sound that low.
Finally: Really low bass are not heard but felt.

GC

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