EQ sub with mains on/off? (DIY Tempest) (1 Viewer)

[KyleGS]

I finished up my newest 100L sealed Tempest design. I also picked up a used ART 351 for practically nothing on eBAY. I've been EQ'ing all morning and got my freq response +- 5 db from 18-100hz. The graph looks great. I knocked out two huge room gains and bumped the low, low end up 1-2db.
I then turned my mains on and now... +- 15db from 20-100hz! I expected some change but not this much. I've run phase checks and everything is ok there. Should I EQ with my mains on?
I'm testing with 1/6th octave tones via CD with SPL and mains on small.

 

[Wayne A. Pflughaupt]

Yes, you should EQ with both mains and subs on – you’ve seen what happens if you use only the sub.

The new peaks are time-alignment (phase) problems – that is, you have bass signals arriving at the test mic a slightly different times. I’m guessing most of the new problems are showing up an octave or so above and below the crossover point, right? Not sure what you mean by “phase check” – if you have a continuously variable phase control, you can eliminate most of the new peaks with the proper setting.

The new problems you’re seeing might not be so bad as it may seem. Often phase problems are manifested as vary narrow peaks or valleys – 1/6-octave or less – and are barely audible.

In your case, using a 1/3-octave equalizer, you’re kinda limited as to how much precise equalizing you can do. I suggest making a note of your previous settings, then start over and re-EQ for both mains and subs. In the end, I would go with whichever settings sound best.

Regards,
Wayne A. Pflughaupt

 

[Kevin C Brown]

This is a good question. I always start with just the sub. But then I compare mains+sub with and without the eq. The last time I did this was eye opening: I started with 5 set filters and got a really nice curve for my sub alone. When I added the mains, got worse. I kept removing filters until I got something I was happy with. Know what I ended up with? 1 filter.

Oh yeah, you might want to take a look at the following. Much, much easier to use than a test CD:

http://www.etfacoustic.com/

I would also heavy duty suggest that when you do look at the mains plus sub curve, make sure you are in phase to begin with. Easy way: play the tone at the crossover freq, mains + sub. Get the SPL for that at the listening position, now flip the polarity switch on the sub, which ever result is louder is in phase.

 

[KyleGS]

I have the PE 250w plate amp with 0-180 deg variable phase. I tweaked it a little more and I will see if that helped here in a little while. I know I'm limited to the 1/3oct EQ but that's what I have and thats what I have to make work. Maybe one day I'll look into the BFD. I think I will start all over and EQ with the mains ON. Thanks for the help once again Wayne.

 

[Kevin C Brown]

Here are 2 more suggestions for CD test discs: Autosounds disc #101, and Stryke. Autosounds is every Hz from 10-98Hz. Stryke has 1/6 octave.

 

[KyleGS]

I have access to ANY freq I want. I have more test tones (1/12th) than time to test. My problem is that I only have a 1/3 oct EQ.

However- I did re-EQ with the mains on and did adjust the phase a little and got +-3 db from 18-100hz. The sound is absolutely great now and I cannot stop listening to it. I'm really happy now. I still have one question. I use an H/K AVR120 for HT duties. This is the receiver used to calibrate and EQ my subs, mains, all levels, etc. Everything is all set-up for that.

NOW- I use an analog H/K 3470 for 2.1 stereo duty. This has no bass management. Does this throw all EQing, phase, levels, calibrating etc. off? I usually just switch the speaker wire over quickly when listeing to CDs. Two receivers- one set of mains...this could get complicated.

 

[Kevin C Brown]

Dude- You should look into a Behringer BFD 1124p. They only cost ~$120 or so. You get up to 12 filters, and any combination of freq set pt, bandwidth, and attenuation amount you want.

 

[KyleGS]

I know, I know. I'll be getting one soon enough. I didn't want anything complicated and only wanted to knock down and couple room gains. I didn't want to spend alot of money on an EQ so I just pick up a used ART 351 for ~50 on eBAY.

 

[Kevin C Brown]

Cool. Actually, if you look around, you can find the previous rev, 1100p (20 bit, not 24 bit), for about the same price at the ART.