My subwoofer doesn't have "sub" / first time REW

[tebling]

My system isn't terribly high end, but I've certainly known that its big weakness is my budget oriented Audiosource 10" subwoofer, which I've had for the last seven years or so. Today I fired up REW for the first time with a laptop and "trusty" Radio Shack SPL meter. I used the RS calibration file linked with the REW download.

Given that I don't have fine EQ control with my Yamaha receiver, my goals were:

1) See if the levels between the sub and mains were well matched.
2) See how "budget" my sub really is.
3) Experience REW!

All of the above were accomplished, and here's what I generated:



Green = sub alone
Blue = mains alone
Red = mains + sub

The receiver crossover is set to 80Hz. Here are my novice observations:

• The levels seem pretty well matched - even more so than I had expected based on simply using the pink noise generator in the receiver.
• The dip centered around 90Hz isn't due to phase cancellation beween the sub and the mains. Maybe I should try using the subwoofer's crossover, which is variable - and set it a bit higher than 80Hz if my mains are falling off there? Actually I should do a run with the crossover disabled first before making assumptions there.
• The subwoofer doesn't deserve the name, as it runs away in terror when approached by anything under 40Hz. I guess sometimes you don't get what you don't pay for
• REW is a fantastic piece of software!

I have an av123 MFW-15 on order, but it's going to be a few months before it arrives. That should certainly remedy the almost complete lack of LFE. In the meantime I'm not sure there's much I can do to improve things here...?

[brucek]

The levels seem pretty well matched - even more so than I had expected based on simply using the pink noise generator in the receiver.

Pink noise in the receiver usually does a good job.

The dip centered around 90Hz isn't due to phase cancellation beween the sub and the mains.

Don't really know why you draw that conclusion. It is exactly the reason I would say is causing the dip, given that neither the sub only or mains only have room induced dips around the crossover and the resultant additive signal isn't adding, it's cancelling. Adjust your phase or sub distance setting to remove the dip.

it runs away in terror when approached by anything under 40Hz

Yep....

REW is a fantastic piece of software

Yep...

brucek

[tebling]

brucek wrote:

Don't really know why you draw that conclusion. It is exactly the reason I would say is causing the dip, given that neither the sub only or mains only have room induced dips around the crossover and the resultant additive signal isn't adding, it's cancelling. Adjust your phase or sub distance setting to remove the dip.

That makes perfect sense. I ended up misleading myself because each of the curves seemed to generally overlap around the crossover frequency. What you say about the lack of additive gain makes perfect sense. I'll play with the phase and see if I can post a flatter curve here.

Thanks for the explanation!

[Canadian_Dude]

You thought your sub was bad..... Mine cuts off at 60 Hz LOL. 8" JBL is definitely not enough.

[tebling]

Unfortunately my sub only offers 0 or 180 degrees of phase offset rather than a continuous sweep. Here's the response comparing the two settings:



Red is 0 degrees, and green is 180. Rather than making anything better, it appears to simply create some cancellation above 100Hz. I'll stick with 0 degrees for now.

[thxgoon]

Play with your distance settings in your receiver as they are just a fine 'delay'. It's a finer way of adjusting phase than 0 or 180. Also, have you played around with room placement?

[Wayne A. Pflughaupt]

Don't really know why you draw that conclusion [that the dip centered around 90Hz isn't due to phase cancellation beween the sub and the mains

Perhaps because it shows up with the sub-only measurement, not just mains and sub?

Regards,
Wayne