Thoughts on my dual VTF-3 measurements?

[pg_rider]

I did a simple measurement of my subs using the Hsu CD test tones. Ran through them three times -- left sub only, right sub only, and both subs together.

The left sub is a Mk III set to Max Extension mode. The right sub is a Mk IV also set to Max Extension with a Q of .5.

Both subs are gain matched, which also worked out perfectly to also be a perfect level match. My crossover is set to 80 Hz. I have the combined sub level set about 3-4 dB hotter than the rest of the speakers in the system. The subs are each located at the 1/3 points of the front wall. Here's a picture of my room and setup (sorry for the poor quality):

Here's the raw data along with a basic graph. Note that I didn't correct the Radio Shack meter readings -- these are the raw numbers. Not good for absolute interpretation, but suitable for comparison sake between the two subs.

Here's what I can glean from the data:

• As expected each sub has different readings. Whether this is due to room effects, or differences between the Mk III and Mk IV, I don't know. There's a 6 dB difference at 31.5 Hz and a 9 dB difference at 63 Hz -- I can't understand how there can be such a delta!

• The response at 50 Hz is significantly down -- I'm guessing this is a room effect?

• The 16Hz and 20 Hz response is impressively strong. However, the mid-bass is frustratingly weak. This actually jives with what I hear -- I've never felt that I had great "thump" from bass drums even though I get great rumble and shake from low bass effects.

• The subs seem to stop contributing anything above 100 Hz, as the combined level is no higher than the individual levels. I assume this is purely based on the crossover doing its job.

Anyway, it was definitely interesting to see the results. I'd like to try and level out the response either by reducing the deep bass or boosting the mid/upper bass. Any suggestions?

 

[fuzz092888]

How serious are you about getting your subs dialed in? $100 serious? If so, I would strongly advise getting a measurement mic from Cross Spectrum Labs and downloading REW. You'll get a ton more information about what the subs are doing and get graphs that will be a bit more useful. What you've done is a great start, but if you want to start making adjustments and maybe even applying some EQ down the road, a measurement mic is invaluable. It can also help with your speakers as well.

 

[shadyJ]

Your subs are symmetrically placed. This might help smooth out the response width wise for your room, but my not effect the nulls that result from lengthwise cancellations. You might check this paper out for tips on different placements. Equalization will help tame the peaks but isn't as effective as dealing with nulls. Optimal placement is the best way to deal with frequency response, after that I would think about equalization. If you can, try mid-wall placements, corner placements, near-field placements, ect. I personally like the near-field placement effect.