question about power handling in modeled enclosure


2013-04-03 6:58 pm
I have decided to build a set of active bi-amped speakers for my cottage. I'll use a minidsp for the active crossover and 100w t amp modules for power.

I've selected and purchased the BG neo8pdr for >800hz (plan is for an open baffle) and the Morel MW-266 for <800 hz which will be in a cabinet.

Like many of us I want to balance cabinet size with F3. Using speakerbuilder software I can model a ported cabinet of 95 litres (as large as I can go given the space) that displays F3 about 30hz and an F10 below 20hz. This puts significant group delay below 20hz with the intention that I use the active crossover EQ to highpass at 20hz, managing the group delay.

The possible problem is that the model shows I hit xmax with 5watts between 30hz - 40hz. 5 watts for these drivers produces about 93db @ 1m.

Whereas at 70hz I can get to about 102db before hitting xmax.

So, my question is how loud will these perceptually get at 30hz? I don't need a lot of volume but I do need to be able to listen comfortably to them. Typical listening distance is about 10'. The cottage itself is an open concept about 800 sq feet on the main floor with a 200 sq ft loft and a peaked roof over the loft.

The alternative is a sealed box of similar dimension that models F3 ~ 35hz and F10 ~23 hz and hits xmax at 7w about 25hz

I appreciate all thoughts!

In the case of a BR you will benefit of a bigger box.
In the case of the sealed your F3 will be detrimental (for the big cottage also to consider). So probably your BR in this case will have a better performance. Make it 125L, with less distortion (magnitude of cone movement) if you can or add 50% to the internal volume. It looks promising either way.


2013-04-03 6:58 pm
Thanks for the very quick thoughts. There is only one usable location for the speakers and that is either side of a low cabinet which ends up restricting space. This means maximum interior box footprint is 10" x 16". Given my desire to use the neo8 as a dipole I had restricted the woofer height to 36" with the neo above the box. I could possibly put 45 angle deflector behind the neo and extend the box height at the rear but I was concerned about how high that rear portion would have to be to add useful volume and also my preference is to not get overly ambitious in box design. Much to think on...
That's not a problem then, if you treat the output with the EQ is not going to make such a considerable difference. (It's just the way they show on paper/computer). Maybe this is enough to help you in not using that extra load of speaker volume & space. The BR is already very (in)comfortable with low freq. extension. Maybe you can just add a couple liters, ex. 100 L, the max. you can for a good design. (EQ in mind)