Is there such a thing as audiophile parametric eq?

What mid bass frequencies are you tryind to tame?

As far as I am concerned, notch filtering is only effective below 100 HZ. Above 100 Hz the problem of room size comes into play. 100 Hz = roughly 10 feet of wavelength, which means the distance between peak and trough is only 5 feet. At 200 Hz the distance between peak and trough is a mere 2.5 feet. This means you only have to move the microphone a couple of feet to get a totally different response from room modes.

Therefore if you try to PEQ "room mode" notch filter above 200 Hz then you are basically chasing your tail...move the mike a foot and you get a different plot. So don't go there unless you are correcting a deficiency in the system or severe seating position problem (like up against a wall). I may be a bit weird but I expect my system to sound good from all around the room...only three feet and less from walls do I normally expect a poor frequency response.

Also remember that notch filters are quite sharp....so they introduce phase distortion. Phase distortion is unimportant at less than 100Hz as you can't even tell which direction these low frequency sounds are coming from. This is not the case above 100 Hz...so a sharp filter above 100 Hz may cause some audible degradation...it may change the timbre of sounds.

I run my Behringer PEQ ONLY to the subwoofer signal for these very reasons.

Rives,

Thanks for the thumbs up! You undoubtedly know a lot more about this than I do, since you build the well known and highly praised PARC.

Jlambrick,

FWIW, I haven't encountered a problem with the Behringer PEQ (I actually have the Feedback Destroyer Pro), however, this is definitely a really cheap piece of kit - so partly for fear, I only use it in the 0.1 channel below 80 Hz. If Eldartford says it is good then it reinforces my experience. I use a Ratshack meter to check settings and I walk around so as not to adjust for one single spot - a very slow and cumbersome process which in the end the "ear" adjudicates. In my defence of such an approximate process, room mode "bumps" are to me fairly obvious. Furthermore, I don't seek to squash everything flat ....I just take the "edge" of the nastiest bumps. My approach is minimalist, I guess. I am also slightly distrustful of automated software algorthms - I like to know what is going on and how much adjustments are being made - rather than let the software take over.

But be warned, I also own a cheap analog mixer by Behringer and it was totally unusable as it degraded the sound. So in general, as the old saying goes, you get what you pay for (I was lucky so far with PEQ and not so lucky with the mixer). Like all those cheap toys with lead paint being returned by Mattel to China, my constant fear with an amazing "bargain" is quality, will it work properly and will it last. Another issue is that you practically need an engineering degree to work the darned Behringer Feedback Destroyer, although I understand the PEQ 2496 is a little easier!

My comments are based on experience and a little back of the envelope physics. My comments also apply only to correction for room modes in the LF. If you want to "tailor" the sound (rather than correct for room modes) then an EQ can do the job well over the full range, the basic rule is to always use it sparingly. As you may now realize, I may be overly fearful of using such a cheap item over the entire frequency range.

Restick,

I am with Rives. You should not average listening points to get an "average" signal as this totally defeats the purpose of correcting for room modes by smearing/smoothing out the problems.

However, in contrast, you should not seek to iron out every bump/null at every 1 Hz data point and get a ruler flat response at one spot....who is to say that one spot is the most representative of the signal quality within your sweetpot area (and after all your ears are 6 inches apart and do some averaging themselves). Who is to say that your zealous corrections are not making it worse 2 feet to the side or causing phase irregularities from sharp filters, for example?

Go for the big broad bumps at lowish frequencies and forget chasing 2 Hz nulls. Once you are satisifed take some measurements around the sweetspot and see how wide an area you can achieve. The biggest sweetspot comes from having a largish room and from treating all the corners and as much of the room as you can with absorption (includes furniture) that works down to say 50 Hz (big thick absorbers). Another factor is leakage....a room that leaks (wood frame) is better than a basement with five surfaces that are concrete. (although a leaky room may disturb others in your home it is usually better sounding)

Perhaps Rives can add whether it is best to stick with 1/6 octave or to do each frequency Hertz by Hertz up to 200 Hertz or so?

Remember also that many speakers produce 10% or more harmonic distortion at realistic levels when driven at low frequencies below 80 Hz (especially small ported designs) In this case your response plot may become misleading, as what you think is a mid bass problem may be caused by excessive harmonics from low frequencies causing mid bass bloom.

A bass guitar with fundamental notes between 50 and 100 Hz will produce 2nd harmonic between 100 and 200 Hz the second harmonic and higher will be part of the signature sound of the bass guitar anyway. However, your ears are roughly 10 decibels more sensitive to 150 Hz than 75Hz and therefore a second harmonic that is only 30% as loud as the fundamental will sound equally as loud as the fundamental note. If you add typical speaker or harmonic amplifier distortion to this then you can easily see how mid bass can get over boosted and the guitar much stronger than the musican/recording engineer intended...all without even considering any room mode problems.

Good luck...