Got AVIA, SVS doesn't kick in until 50Hz... placement? (1 Viewer)

[Willem Vos]

At first I was using the THX-optimode test, which wasn't really telling me a lot.
I got AVIA a couple of days ago, and have discovered measuring the LFE 20-100 frequency sweep, that the SPL-meter indicator stays at -10 until the sweep reaches 50Hz at which point the SVS causes the indicator to go to +6
this stays on till about 40Hz at which point it goes back to 0. It goes up again, and then dies down after 26Hz.

The low frequency performance is without any question, but as I understand, I have a big gap between 100 and 50Hz! That can't be right, can it?

The range on the RS-SPL-meter is set to 80, C-weighting, slow response, the volume on the denon avr was set to -25. The sub is a SVS 20-39PCi

It was suggested on another post that I should position the sub in my seating position, and walk around to measure the optimum subwoofer location. I'm going to try that next, but I just wanted to check if anyone has another idea to solve this thing. Thanks for any help.

 

[John Garcia]

Putting an SVS in your seating position is not exactly the simplest thing to do , but the method is a good one.

What you haven't said is what your other gear is and how it is set up (specifically your receiver), since that is very likely where your issue lies. How is your SVS hooked up and crossed over? The next possibility is that your mains are where your gap is coming from... It is highly unlikely that your room would be cancelling EVERY frequency between ~50 and 100Hz, so I would take a look at your system settings first.

 

[Willem Vos]

Well, the lowest possible crossover setting on the avr is at 80Hz. I have tried it at 80, 100 and 120Hz but it makes no difference. Also, at 120, I think the subwoofer should be kicking in a lot sooner that 50Hz, but nope...

I have set the crossover of the SVS to disabled, and all my speakers are set to small.
100Hz-50Hz seems like a big gap to me as well, I must be doing something wrong... but what?!

 

[John Garcia]

What are the main speaker and/or what is their low end response? What receiver specifically?

Changing the crossover setting should have made a difference, so there may be another setting somewhere that may be causing this problem. It may be an LFE setting, independent of the bass management settings, that filters everything above 50Hz in this case.

 

[Willem Vos]

What are the main speaker and/or what is their low end response? What receiver specifically?

Main Speakers: B&W 601S3, center LCR60S3
Low-end response of the 601's is at -6dB at 48Hz
Receiver Denon 3802
No DNR switched on...

 

[MarcVH]

You may just be getting some room response giving you a big hump in the 40-50 Hz range, leaving you without so much audible sound other places.

It's also possible you have a phase problem, and the SVS and your mains are competing with each other. Try reversing the phase on the sub and see if that changes anything. I had a similar issue that was fixed by a phase reversal, although my hole was much smaller than yours.

 

[Bill Polley]

turn the radio shack meter down 1 spot. See if you get any response from the meter at the 50-100Hz frequencies. You may just have a large room resonance from 25-50 Hz that needs to be tamed. I had a room resonance that was +12 db at 48 hz.

 

[Willem Vos]

No, it's not the phase, I just set it to 180. Didn't do anything. There is just almost no movement on the meter until approx. 55Hz at which it shoots up.

If it's a hump at 50-30, shouldn't there be at least 65dB at -20 volume level in the beginning of the sweep? I don't even get that... would that be solved by moving the sub?
At 100Hz the sub isn't participating, but neither is anything else ...

turn the radio shack meter down 1 spot. See if you get any response from the meter at the 50-100Hz frequencies. You may just have a large room resonance from 25-50 Hz that needs to be tamed. I had a room resonance that was +12 db at 48 hz.

How much did you have to move the sub to tame this large hump? Looks like that has to be it...I can't think of anything else...that would mean I have something like +20dB at 50Hz. Ouch.

Thanks for the help so far, guys.
I'm just going to have to try the place-sub-at-seating trick. This thing is driving me nuts!

 

[Bill Polley]

I bought a Behringer Feedback Destroyer. ($120 from Zzounds). It is a stereo 12 band digital fully parametric EQ. It is perfect for equalizing most, if not all, of the room response irregularities out of your sub.

Try this: http://www27.brinkster.com/jmag999/

or this: Link Removed

 

[Willem Vos]

Looks like a good piece of equipment to have...
Is it possible to solve this my a mere relocation of the sub, though?

Don't want to rush out and get a BFD just yet.

 

[Bill Polley]

Finding the best sub location will help somewhat, but sticking the sub in a corner is like doubling the amplifier power. The sub interacts with the walls in a way that gives louder playback for the same power. (plus, the SVS is out of the way!). Then you can use the BFD to tame the resonances.

Try setting the sub at your listening position, then walk around the room and find the best bass. That is where your sub should be located. If it is in a bad spot, say...right in front of the TV, then put it in the corner and buy a BFD.

 

[Willem Vos]

Okay, that sounds like a good plan.

After more experimentation, something is puzzling me now, though. I've tried the LFE frequency sweep 100-20, with the mains set to small (crossover always at 80Hz), and large. With large, I get the subwoofer options: LFE or LFE+Main. The final Bass-management option is to set the subwoofer to "no".

Only when setting the last option, does sound come from my main speakers during the LFE sweep, which explains this post...
This is not logical, right? Avia itself says that there should be a crossing-over from the mains to the sub. How can there ever BE a crossing-over if the only way sound comes out of the mains is by bypassing the sub by setting it to "no"?!

 

[Tyler DJW]

Hi Willem,
The avia test tone doesn't come through the LFE channel but through the left or right or one of the full range channel. I think what you observed does make sense when you know where the signal is coming from. With the subwoofer set to "NO" on your receiver you're telling it NOT to implement the crossover and redirect the bass to the sobwoofer. Ideally, your speakers should be set to small, and subwoofer set to "Yes" and "LFE".

When i first started reading this thread my first thought was that you had the crossover enabled on your SVS. If that's not the case I would run the freqency sweep again and check the driver on the SVS visually or by touch. You should be able to tell whether it is actually giving you anything above 50Hz or not this way.

Despite what the SPL meter says, can you still hear the tone in the 100-50Hz range?

Best of luck getting it working for you. I wouldn't by the BFD unless you really can't make an adjustment in the room/receiver/sub. I don't have any experience with it, but I'd hold onto the cash personally.

 

[Willem Vos]

Despite what the SPL meter says, can you still hear the tone in the 100-50Hz range?

Yes, there is sound coming from the sub in the 100-50 range. But not as much as when it reaches 50Hz, though...
I guess the AVIA LFE test is pretty useless for testing the crossover. I'll stick to the separate-speaker frequency sweeps:

Measurements of AVIA frequency sweep 200-20 Left-Front to subwoofer (volume on receiver at -25):

 

[Bill Polley]

Get some closer frequencies...1/12 octave is good. Then plot your graph. ABFD will easily tame all of the peaks, but the nulls (valleys) should only be boosted a little (if any). It is possible that the room null will cancel the sound at that frequency no matter what. If you boost it and nothing happens, leave it alone. All you would be doing is putting a lot of stress on the sub and its amp.

 

[Jeremy Anderson]

Despite what Tyler says, the LFE sweep test -IS- encoded solely to the .1 channel (see Title 6, Chapter 52 of Avia). The separate speaker sweeps can be used to check crossover performance, but only with speakers set to SMALL. What Tyler is likely referring to is that there is no separate LFE-only tone for level calibration. However, there is a 6-channel pan under Verification/Evaluation in which the LFE channel is encoded at the same dB level electrically as the other channels, which can be used to verify that the LFE is being played back at the proper level.

After more experimentation, something is puzzling me now, though. I've tried the LFE frequency sweep 100-20, with the mains set to small (crossover always at 80Hz), and large. With large, I get the subwoofer options: LFE or LFE+Main. The final Bass-management option is to set the subwoofer to "no".

This is because that sweep is in the LFE channel only, as I said before. The only way to make that tone come from the mains is to set your receiver so that LFE comes from the mains (i.e. setting subwoofer to NO). It is performing as it should. Since the crossover is not being used at all on this sweep, proper phase can not be determined. To find the proper phase, run one of the separate speaker sweeps with all speakers set to SMALL and subwoofer ON. Take SPL readings as it passes through the crossover range. Then reverse the phase and repeat. Leave the subwoofer set to the phase setting that produces the least dip at the receiver's crossover point. DO NOT use the crossover on the SVS and the crossover on the receiver at the same time, or you'll get a giant hole due to crossover cascading. Disable the crossover on the SVS or simply turn it to its highest frequency setting.

Your only options as far as smoothing out the subwoofer response, as others have said, is to reposition the subwoofer or get an EQ to tame the peaks.

IMPORTANT NOTE: The Radio Shack SPL meter is inaccurate as the frequency drops. Be sure to use the correction chart included in the book that came with your meter. In case you don't have it handy, here it is:
20Hz: +7.5 (meaning 70 on meter = 77.5 real reading)
22: +6.5
25: +5
28: +4
31.5: +3
36: +2.5
40: +2.5
45: +2
50: +1.5
56: +1.5
63: +1.5
71: +1.5
80: +1.5
89: +1.5
100: +2
111: +1
125: +0.5
142.5: +0.5
160: -0.5

 

[Mike Matheson]

Willem,

Do you have a CD burner? You could create your own test disc with discrete frequencies (say, every 1 hz) to more finely measure your response.

Good luck with it all.

BTW, I use a BFD myself with great success. Also the ETF software for sort of an RTA (realtime analyzer) effect--makes seeing your response curve MUCH easier/faster.

 

[Willem Vos]

Get some closer frequencies...1/12 octave is good.

Pretty hard thing to do, the measurements of the graph I took with AVIA disc were already tricky to get right . (Wished the measuring range of the SPL-indicator went from -20 to +20...)
I'll have to burn a Test-CD like Mike said...

On another note, I tried the timbre-test (alternating pink-noise between Main-Left and the Center speaker, but it went haywire with some pops, and then just stopped (looping is on). I tried it on another HT (downstairs) and it worked fine. Problem with the DVD-player (Pioneer DV-525)?

 

[Jeremy Anderson]

Willem, I had that same problem with my old GE 1105p DVD player. The timbre-matching test for the center channel would just make a popping noise and then lock the player up. Works fine on my Panny RP-56 though.

 

[Mike Sloan]

With the Denon 3802 when you set Front speakers to large...the receiver only sends the LFE to the sub...It strips the LFE out of the mains. If you are going to run your Fronts large make sure the sub is set to LFE+MAIN. Its the same with the 4802 and the 5803. The only way to get the LFE to the mains is to select sub off. Off subject but just a little more info.

Have you tried a different sub to see if you get the same results?