# Problem with FBQ2496



## Guest (May 21, 2008)

I bought the FBQ2496 as it is supposed to be better than the DSP1124P

I noticed that the FBQ is lowering the entire output even if I have appled negative gain at one frequency. I verified this by sending the FBQ full range signal. Then I lowered the gain of
just one filter at some 35hz. But the entire output got lowered as the volume of the speakers
dropped as I lowered the gain on that one filter. This is not due to bandwidth. The max. bandwidth
FBQ allows is 10Hz. So if I apply a gain of some -5db at 35hz with a 10Hz bandwidth, there is no way the entire signal volume will drop. Similarly when I increase the gain of just that one filter, the entire
output level goes up.

I wanted to confirm if this is a defect before I return the unit.

My first DSP1124P was defective. Then I got another. Then I noticed significant
degradation in sound quality when I sent full range signal. So I bought the FBQ2496 as
it is supposed to have better circuitry.


----------



## brucek (Apr 11, 2006)

> I noticed that the FBQ is lowering the entire output even if I have appled negative gain at one frequency.


No, it doesn't do that (unless you have a fault of course).

Hopefully you realize the panel entry of an FBQ is in octaves and not hertz (Hz).

A 10 bandwidth entry into a FBQ would be a filter that was 707 Hz wide at the half gain points. That's a very low Q filter and would appear to modify the level of sound from your speakers.

To perform a better test, simply hook up REW to your receiver and output a sine wave at 1000Hz and then enter a simple -20dB filter into the FBQ at 100Hz that has a reasonable bandwidth of 0.333 (23.6Hz at half power points). The 1K tone should not alter its level.

Play around off-line with REW and look at how wide the filters are and how much they'll affect levels quite a distance away.

brucek


----------

