[Wayne A. Pflughaupt]

adogand6kids wrote:

The pink noise test tone is made up of all the frequencies in the bass spectrum, so when it plays, it will measure at the SPL of the loudest part of the spectrum.

Yes and no. The meter is only going to display what it “sees” as the hottest frequency, whatever that may be. You noted that you have created an upward slope from 80 to 30 Hz. Using the old correction values for the Shack meter (I think they have been somewhat discredited in recent years, but we’ll use them here anyway for the sake of argument), the meter starts to roll out below 50 Hz. So with a house curve, assuming a picture-perfect one (big assumption), the meter would be reflecting what it “sees” at the highest level. That would be 50 Hz, since equalizing is dropping everything above that point, and the meter’s response is dropping everything below that point. The meter is down 3 dB at 31.5 Hz. Your house curve may or may not be fully making up for that – you’d have to have a greater than 3 dB increase at 31.5 Hz compared to 50 Hz for it to register on the meter as the indicated SPL reading. Otherwise, the meter is reflecting 50 Hz with a house curve.

But even this isn’t in stone. The problem with pink noise is that it’s something of a random signal. You’ll notice on an SPL meter that the reading will jump around a lot compared to say, a steady-state sine wave tone. With a broadband pink noise signal, all frequencies will be jumping around like that. You can see on a real time analyzer - at any given second, one frequency will be hotter than another (assuming a baseline of flat response).

If I use my test tones to set my sub level equal to my mains, I will be setting the mains to match the SPL of the low end of the bass response (because this is playing the loudest), when in reality I want it to match the high end of the bass response (where it crosses over with my mains). Am I correct?

It should be obvious at this point that with an SPL meter, it’s impossible to do a clinically accurate level setting. If that’s your goal, your best bet would be to use a real time analyzer. As Terry mentioned, REW can work, but it would be better for this to use coarse smoothing – between 1/3 and 1-octave.

Not to sound rude, Wade, but IMO you’re really overanalyzing all of this. At the end of the day a house curve is 100% subjective. Personally I’d just toss the meter and set the levels by ear. If the bass sounds weak once you pop in a DVD or CD, then turn the sub up until it sounds right. If it seems like the upper bass frequencies are too strong, then go back in to the EQ settings and tame them as needed. And so on.

Second question. I have heard people saying that you can use your BFD presets to have a couple different sub responses. One preset can be used for a flat response and another can be used for a housecurve. But, if what I said above is correct about matching levels, then if you set levels using a flat response you will be down 10 dB at the crossover when you switch to a house curve. And, if you set levels using a house curve, then you will be up 10 dB over the whole bass spectrum when you switch it over to the flat response. Again, am I right in my thinking here?

That could be a problem since the BFD has no provision for adjusting signal levels, much less per-preset. Your best bet would be to EQ your “flat” curve along the regular target line, as you did the house curve along that target line. Make sure both target lines are at the same level where they peak, and you should be set. If that doesn’t do it, your only option (and it’s admittedly a lame one) is to tweak equalizer filters as defacto level adjustments.

Regards,
Wayne