Question on sub frequency response.... (1 Viewer)

[Vader]

Based on the feedback of all here, I think I am going to go with an SVS20-39PCi. Prior to putting the Boston Acoustics on ebay, I was testing the frequency response via DVE, running a test tone from 5-150Hz. According to the specs, the frequency response for the PV400 should be nearly flat up to 150Hz (+/- 3dB), and yet the test tone rolled off at around 120Hz. The bass was smooth, so I don't think anything is blown (I hope). I want to put it on ebay, but not if there is anything wrong with it. Any ideas?

 

[Carl P]

Could it be that your crossover in your receiver is starting to roll it off? Personally I wouldn't worry about it as most people don't crossover that high anyway.

 

[Vader]

The crossover in my receiver (Denon AVR-2105) is set to 80Hz. My main concern is that if the sub is somehow rolling off prematurely (?), stuff between 120 and 150Hz on the LFE (not subject to the crossover, to my understanding) is missing. Following that reasoning, since it is on the dedicated LFE, the mains (set to small) would not pick up the slack. I know that the LFE test signals on DVE are about 13dB to hot, but have not heard anything about any other problems....

 

[Edward J M]

You would need to feed the sub a test signal directly to determine its upper FR limits.

The Dolby Digital spec calls for a brick wall filter at 120 Hz on the LFE channel, and your AVR rolled off the signal above that that frequency (DVE uses the LFE channel for sub tones).

I'm quite sure the sub can play above that frequency, and I wouldn't worry about it.

Regards,

Ed

 

[Vader]

Thanx, Ed!

One question: Why would DVE feed an LFE test tone up to 150Hz if the playback is limited by the filter at 120Hz?

 

[Edward J M]

Beats me. Maybe so you can see the effect of the filter at 120 Hz?

I know DVE uses the LFE channel for the sub calibration tone. It's possible it uses redirected bass and a speaker channel for one of the sweeps - you would have to research the menu location and sweep number/description to be sure.

I know Avia has both - an LFE channel reverse sweep (from 100 Hz IIRC) and the redirected bass speaker channel reverse sweep (from 200 Hz IIRC). The RB sweep will only transition to the sub if the speakers are set to small and the sub is set to on/yes.