[mlundy57]

I ran REW in my new room today. There is about a 6dB dip between 60 and 200 Hz. This is so whether the crossover controls on the A370 amps are set on 80 (halfway) or 120 (wide open). The red line is the left speaker/sub only, the green line is the right speaker/sub only, and the blue line is both speakers/subs.





Here are a couple pics of the room. As you can see, there is not a lot of flexibility here.






Any ideas?

Thanks,

Mike

[Folsom]

Turn the phase knob on the crossover and see what happens.

[mlundy57]

Turn the phase knob on the crossover and see what happens.

I’ve tried that at 0, 90, and 180. I’ve also tried reversing the phase on the NX-165 drivers with the sub at those 3 positions. No difference

I have also moved the microphone closer to the speakers by 1’ and 2’. The dip got worse.

[Tyson]

I’ve tried that at 0, 90, and 180. I’ve also tried reversing the phase on the NX-165 drivers with the sub at those 3 positions. No difference

I have also moved the microphone closer to the speakers by 1’ and 2’. The dip got worse.

What are your other settings set to on the amp?

[mlundy57]

What are your other settings set to on the amp?

The crossover is at max (120). There was no difference in the dip between the 12 o’clock position on the crossover and the max position. The line in filter is on AVR 12, rumble filter off, extension 14 Hz, low damping.

Volume is at 11 o’clock. Any higher and the lower bass is too much. As it is I have PEQ on with gain at 1 o’clock, bandwidth at minimum, and frequency at 12 o’clock to tame a 40Hz peak.

[Tyson]

Turn off the main amp driving the top speakers and take measurements with just the subs on. 

After that, turn off the subs, turn back on the main amp, and take measurements of just the top sections running. 

I also recommend putting the rumble filter on, setting the damping to high and the extension to 28hz.

I suspect that you're room's too small and the low bass is overwhelming it, causing the very low end to be very boosted to the mid/upper bass.  These settings should help ameliorate that.

Don't worry, your still gonna get very strong low bass.  Trust me

[Danny Richie]

That's a pretty big room suck out. It will have a lot to do with the size and length of the room verses how far the speakers are out into the room.

Try pulling the speakers further out into the room and see what happens.

It also helps to shoot the output of the MTM and sub separately then overlay them to see how they sum.

And stick with just looking at one speaker at a time.

[Danny Richie]

And what Tyson just said...

[mlundy57]

Turn off the main amp driving the top speakers and take measurements with just the subs on. 

After that, turn off the subs, turn back on the main amp, and take measurements of just the top sections running. 

I also recommend putting the rumble filter on, setting the damping to high and the extension to 28hz.

I suspect that you're room's too small and the low bass is overwhelming it, causing the very low end to be very boosted to the mid/upper bass.  These settings should help ameliorate that.

Don't worry, your still gonna get very strong low bass.  Trust me

I’ll try the changing the toggle switchs tomorrow.

I’ve already done the rest. The first thing I did was measure the left speaker with the sub off to find out where it was 6dB down. Then I turned the power amp off and the sub amp on. Then I adjusted the sub to get it 6dB down at the same point. Then I pulled down the peak at 40Hz. Next I turned the power amp back on and measured both sections together. I expected them to be additive and pull the dip up but it didn’t happen. I increased the crossover point on the sub to see if it would help but it didn’t.

Next I did the same process with the right speaker and got the same result.

Finally I measured both speakers together. The SPLs were higher but the pattern, including the dip, remained.

[Danny Richie]

I'd still like to see the individual responses.

Not only pull them out into the room further but change the toe in and see what happens too.

[mlundy57]

That's a pretty big room suck out. It will have a lot to do with the size and length of the room verses how far the speakers are out into the room.

Try pulling the speakers further out into the room and see what happens.

It also helps to shoot the output of the MTM and sub separately then overlay them to see how they sum.

And stick with just looking at one speaker at a time.

Currently the back of the subs are 3’ into the room. That puts the sub’s baffles 42” into the room and the MTM’s baffles 50”. Inside to inside the speakers are 74” apart (89” center to center) and 94” (almost 8ft) from the listening position. The LP is 19” off the back wall.

The room is pretty small, 12’x14’x8’

[mlundy57]

I'd still like to see the individual responses.

Not only pull them out into the room further but change the toe in and see what happens too.

More or less on the toe in?

[Danny Richie]

More or less on the toe in?

Both. It will change the off axis cancellation pattern and how the room is loaded.

[mlundy57]

Both. It will change the off axis cancellation pattern and how the room is loaded.

Ok. Have to wait until tomorrow. Wife has gone to bed so I’m banned from running sweeps for the rest of the night. The bedroom is below my music room 

[mlundy57]

Ok, I've adjusted rumble filter, extension, and damping settings. The only real difference was with rumble on the low bass was actually louder but it didn't affect the dip.

I moved the speaker (only working with the left speaker at this point) up to 6" into the room, 6"closer to the front wall, 6" closer to the center, and 6" closer to the side wall.

I adjusted toe in incrementally until the speaker almost faced the side wall and crossed in front of the LP like a horn.

I also tried removing the diffraction/absorption (GIK Alpha panel) at the first reflection point.

The only thing I really managed to do was turn the dip into a bi-modal dip at 125Hz and 175Hz.





Mike

[Danny Richie]

Just to confirm you can make sure each is playing down to or up to to the range they are suppose to cover. To do this you can turn level way down and take a near field of the upper woofer and of the lower mid. And by near field I mean from about 1/4" away from the woofer dust cap or phase plug. Then we'll know what the drivers themselves are doing. 

[mlundy57]

Just to confirm you can make sure each is playing down to or up to to the range they are suppose to cover. To do this you can turn level way down and take a near field of the upper woofer and of the lower mid. And by near field I mean from about 1/4" away from the woofer dust cap or phase plug. Then we'll know what the drivers themselves are doing.

I’ll try that this evening when I get back from a birthday party

[mlundy57]

Just to confirm you can make sure each is playing down to or up to to the range they are suppose to cover. To do this you can turn level way down and take a near field of the upper woofer and of the lower mid. And by near field I mean from about 1/4" away from the woofer dust cap or phase plug. Then we'll know what the drivers themselves are doing.

The drivers are doing what they are supposed to

[JLM]

The dip is the room 'talking' to you.

Why are the subs located under the mains?  (Probably the worse place for them.)

Have you tried various sub locations, including raising one up? 

Have you tried running one of the subs out of phase?

Have you tried the 'sub crawl' to properly locate the subs?

Why not just EQ the 6 dB dip out?

[mlundy57]

The dip is the room 'talking' to you.

Why are the subs located under the mains?  (Probably the worse place for them.)

Have you tried various sub locations, including raising one up? 

Have you tried running one of the subs out of phase?

Have you tried the 'sub crawl' to properly locate the subs?

Why not just EQ the 6 dB dip out?

It is the way they were designed. They are two part full range open baffle speakers. They could have been built as a single cabinet but they are easier to move around (especially up stairs) in two pieces.

As I understand it, raising a dip is not a good idea.