What's going on around my crossover freq?

[pg_rider]

Did some basic measurements with the Hsu bass disc test tones and my Radio Shack meter. I got some very curious results that I wanted your thoughts on.

First, my setup. I've got dual Hsu VTF-3's placed symmetrically up front with my LSA One Monitors. I've run Audyssey XT32 with my Denon X4000, then raised the summed sub level by 3dB. Finally, I left Dynamic EQ on for all measurements.

I ran the tones four times, each with a different crossover setting (80Hz, 100Hz, 60Hz, and 120Hz). At the 80, 100, and 60 Hz settings it appears I have a big problem (dip) in the 80-100Hz range. However, at a 120Hz crossover the response balances out quite nicely. Below 80Hz and above 100Hz the response is very even regardless of the crossover setting.

For the lower crossover settings, does this mean Audyssey is doing a poor job blending the subs and mains around the XO frequency? At first I thought I simply had a bad null around 80-100Hz (which seemed too wide of a band to have a null in), but with the 120Hz XO setting the results are much better. Is that because the sub is flatter through that range than my mains and therefore doing a better job?

Interested to hear your thoughts. Oh, I know using this limited set of test tones and a Radio Shack meter isn't a very high fidelity test, but it at least gives me some data to work with.

 

[ski2xblack]

Nice looking room!

This is a situation where better rta gear would make your life much easier. Have you tried adjusting phase independent of what Audyssey is doing? Seems to me that if the frequencies and slopes are correct, being out of phase will result in a dip at the crossover freq, but done right should sum flat.

 

[pg_rider]

Thanks for the reply ski2xblack. I haven't played around with phase or distance settings yet. Several folks on the Hsu forum have suggested that Audyssey actually does a poor job of optimizing the sub distances in relation to the mains to ensure a smooth blend through the crossover. I may simply try changing the sub distances and see what I get. Longer term I'll likely invest in an REW setup...

 

[ReUpRo]

Pg, 2.2 measurements cannot be used to determine root cause of the dip in FR. You need to take the measurements with all processing, (including DEQ) off. This will eliminate Audyssey as the variable and you see the speaker+room FR, aka. room response. Further, measure one channel at a time, L, R full range (Pure direct will have this effect) and then both subs individually with the cross over set as high as possible. The goal is to get all four channels optimized BEFORE running Audyssey. That way the need for correction is minimized and correspondingly, processing is less heavy handed.

Back to your issue, let's see the L, R, Sub 1 and Sub 2 FR and take it from there.

 

[j_garcia]

Have you experimented with different speaker placements? My guess is curtains on one side and a large opening on the other.

 

[aarons915]

Not sure if OP is still around but what is happening is your mains are ported and extend down to 42hz per their specs so when you cross them over with a 2nd order high pass combined with a 4th order low pass like your Denon and most receivers use, you get different slopes which gives you a large notch at the crossover region as shown in your graphs. Your high pass needs to be a 4th order slope which you can achieve electronically or if your speakers came with port plugs that should also give it a higher rolloff point and a 2nd order acoustic rolloff which will combine with your 2nd order high pass filter for a 4th order sum.