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Discussion Starter #1
I just added my first subwoofer (Rythmik D15SE) to my system back in April – Wow what fun!! I have spent hours reading here at the Shack about measuring and equalizing (what a great resource!) – but I am a little overwhelmed and feel just a tad over my head!

The room is a large Great Room – 4000 cu feet and it opens onto another 4500 cu feet. I have completed my first measurements and attached – 1st is sub only and the second is sub plus Boston VR2 mains. How do they look? I guess I’m not sure what to do next. Suggestions?
 

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Looks pretty good, except for a dip around the crossover area (which I presume is 80Hz).

Did you play with the subs phase control to try and smooth that out?

brucek
 

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Discussion Starter #3
Thanks for the fast reply. Yes, crossover is 80hz. I adjusted phase by playing an 80hz tone and adjusted the phase until i got max spl on my spl meter. Is there a better way??

Do you have any suggestions about determining the best crossover between 60 and 80hz??

Jay
 

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Is there a better way??
Use the RTA in REW and watch the crossover dynamically while adjusting the phase.

Do you have any suggestions about determining the best crossover between 60 and 80hz??
Run a mains only measure and see if they're capable of a 60Hz crossover.

brucek
 

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Discussion Starter #5
Ok. I ran RTA and adjusted my phase from current 180 back to zero. At 0, I trade the null at 70Hz for one at 50Hz. The Phase at 90 gives nulls at both 50 and 70 Hz.
RTA compare of current phase180 (black) with phase 0:
sub+mains_phase180_0.jpg

RTA comparison of current phase180 (black) with phase90:
sub+mains_phase180_90.jpg

I also ran a FR for the Mains only using the subwoofer calibration: (I see there is a dip at 80Hz - the current xover and at 55Hz.
mains_only_070209.jpg

Do you think my Boston VR2 mains have enough low end to lower the xover to 60Hz?

Thanks, Jay
 

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Do you think my Boston VR2 mains have enough low end to lower the xover to 60Hz?
It's more than just a matter of them being able to play low. Power handling capacity is relevant, too, especially with small woofers like the VR2s have. I had some speakers with 8" woofers and a 10" passive that went down to 30 Hz, but they didn't work with a 60 Hz crossover with movies. I had problems with the woofs bottoming out. Once I moved the crossover point up to 90 Hz, I had no more problems.

The problem with movies is that many of them, especially action flicks, have severely boosted bass levels that can essentially blow out the crossover, exactly the same way that severely boosting with an equalizer would do. For instance, with a 60 Hz crossover, the signal will only be down 12 dB or so at 45 Hz. Not too hard for boosted movie bass to flatten that out.

If you try the 60 Hz Xover, put in a bass-heavy action flick and keep an eye on the speakers. If you're getting violent cone movement, raise the crossover point.

Regards,
Wayne
 

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I have VR3s and I keep the crossover at 80hz. It's not too difficult to get good subwoofer capability up to 80hz, and if worse comes to worse, you can always add more subwoofers. With speakers, your displacement capability is fixed, so the goal is let them excel in a range they can easily handle without any chance of degredation.

A lot of people go bonkers with their subwoofers but then suffer in the 80-250hz range due to lack of competency in that range from their speakers - this is very noticable if you know what to listen for. By keeping your crossover at 80hz, you give those four 6.5" drivers a greater capacity to excel, as they shouldn't have to break a sweat in all but the most extreme circumstances.
 

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Discussion Starter #9
I have been out of pocket for the last few weeks –so I haven’t posted.

First - Thanks to both Steve and Wayne for their suggestions on crossover – I have decided on 80hz. I have also been adjusting location and experimenting with BFD filters.

The first two graphs are without any filters – SubOnly and Sub+Mains:
SubOnly
subonly_073109_nofilters.jpg
Sub + Mains
sub+mains_073109_nofilters.jpg

The next two graphs show REW fow SubOnly and Sub+Mains measured with the following 2 BFD filters:
2 Filters 073109.JPG
SubOnly
subonly_073109_2filters.jpg
Sub+Mains
sub+mains_073109_2filters.jpg

How does this look? I would appreciate any comments or suggestions!

Thanks!
 
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