[Wayne A. Pflughaupt]

There’s no free lunch. Any outboard equalizing is going to increase S/N and reduce dynamic range. Boosting will increase noise from the equalizer (this is true of both analog and digital equalizers). Cutting will increase noise elsewhere in the signal chain. Take your pick.

The question comes down to, “Is it audible?” That’s something the end user has to determine for himself. Fortunately, most modern home electronics spec so well they have more than enough S/N and dynamic range to spare. More info here and here.

In this particular situation, we decreased the sub's S/N drastically by feeding it an extremely low signal, which required boosting its gain control substantially (a low signal/high gain scenario is a know recipe for increased noise). And, we increased output below 20 Hz, which can only exact a headroom penalty on the amp.

So, in this case, excessive cutting has cost us both S/N and headroom. To the sub amplifier anyway - I assume the BFD's S/N is intact via a maximized input signal. (Not sure what the advantage of that is if it sacrifices the downstream component. Perhaps someone can enlighten me.)

By the way, impulse response is an acoustical measurement. I doubt things like S/N or dynamic range, which are electrical measurements, have any bearing on it, but I’m sure John M. can speak to that better than I can.

Regards,
Wayne