Help with very strange subwoofer curve

[Matt1980]

Hi I ha have just done my first analysis to set up my subwoofers (two) using REW and a minidsp 2x4 hd. However the curves I get are very strange compared to what I see online. I'm not sure how to intrepet them. If there is something wrong with the settings or if my subs are not good. I have 2 focal air subs in a small room. Thanks for the help.

 

[John Mulcahy]

Make sure you don't have any crossover filters active in the miniDSP, a HP crossover filter might be in the path.

 

[Matt1980]

Thanks, I did deactivate them with the bypass filter and had that curve...so it must be something else...

 

[Matt1980]

This is the full curve

 

[John Mulcahy]

Try measuring very close (a few cm) to one of the subs with the other off to see what the sub's near field response looks like. The Focal Air is fairly small as subs go, so it won't go that far down. Spec does say -3 dB at 40 Hz though.

 

[Matt1980]

Thanks, I'll try that. So I should use the mic with the normal calibration file instead of the 90° and position the mic next to the subs instead of the listening position? Correct ?

 

[John Mulcahy]

Yes. The cal files should be the same at low frequencies anyway. Watch out for clipping, will need to test at a lower volume being so close.

 

[Matt1980]

Ok, thanks so much. Then, if I'm not taking the measures from the listening position. How would I calibrate for the delay of the subs being in different places in the room?

 

[John Mulcahy]

This is just to understand whether there is some problem affecting the response of the subs.

 

[Matt1980]

Still a similar curve putting the mic next to the speaker

 

[Matt1980]

Here is the whole curve

 

[John Mulcahy]

Looks like there is a high pass/crossover filter (80 Hz?) somewhere in the path.

 

[Matt1980]

Where should I check that ? I'm using a Marantz 5014 avr and I set all speakers to small, crossover to 250hz, LFE only and 120hz

 

[Matt1980]

Where should I check that ? I'm using a Marantz 5014 avr and I set all speakers to small, crossover to 250hz, LFE only and 120h

 

[Matt1980]

I the subwoofer I set the crossover to LFE setting (maximum) and volume to mid position (12 o'clock)

 

[John Mulcahy]

Try removing the miniDSP from the chain first to make sure that isn't having any effect. Could also try connecting the PC headphone output directly to a sub to see how it looks with nothing else in the path.

 

[Matt1980]

Ok, I'll try those

 

[Matt1980]

If I connect the PC out directly to the sub, how is the pink noise reproduced ? Currently it is reproduced from the front left channel.

 

[John Mulcahy]

Select the PC's headphone output as the output.

 

[Matt1980]

Hi John, I've tried taking the minidsp out of the chain and I still get a similar curve

 

[Matt1980]

I've now tried setting the volume in the Subwoofer to max, and I think I get a better curve

 

[John Mulcahy]

It looks the same. Have you tried connecting the sub directly to the PC and measuring it that way?

 

[Matt1980]

Yes, here you have the curves connected directly to the PC. In violet its connecting both rca inputs and below in green connecting only to LFE input.

 

[John Mulcahy]

Did you mean to post an image?

 

[Matt1980]

Yes, here you have the curves connected directly to the PC. In violet its connecting both rca inputs and below in green connecting only to LFE input.