AVIA Calibration - What's the deal with the LFE sweep? (1 Viewer)

[Willem Vos]

Hi,

I've got a similar thread running at speakers & subwoofers, but I'm not getting much response there...
I recently got the AVIA Calibration disc, and have been running the LFE-sweep 100Hz to 20Hz. Is it normal for it to slope up from 100Hz to 65Hz? I'm measuring zilch (well, a little) response from the sub from 100hz to 70hz

I know crossovers slope at the crossover points, and are not solid boundaries.

So I set my crossover to 120Hz and my speakers to small. My mains are not participating when running the sweep, which is logical.

But this would mean the full 120-20 LFE bandwith would be sent to the sub, but funnily enough this is not the case. What gives?

 

[Dave Poehlman]

So I set my crossover to 120Hz and my speakers to small.

Do you mean you set the rolloff on the receiver or the sub itself? If you set it on the receiver, check the active crossover (if there is one) on the sub to make sure it's turned all the way up. That's the only thing I can think of.

 

[Willem Vos]

Thanks for the reply Dave.
Yes, I am using the crossover on the receiver. The crossover on the sub is disabled. I'm all out of ideas...

 

[Anthony_Gomez]

I would burn a test sweep from 10-100hz on an audio track. Then hook up the sub amp to the L/R output on you reciever and make sure that they mains are set to LARGE (IE crossover in the amp is dissabled).

If you do this and the sub is still somewhat attinuated in the 100-70hz region, then the XO is NOT dissabled on the sub amp and you are hearing almost zilch because you sum your 2nd order xos to a 4rth order (-24db/octave).

hope I was clear enough

good luck!

 

[Willem Vos]

Thanks, Anthony.

That would be a sure fire way to test the existence of crossover. I'll try it out.

 

[Pete Mazz]

So I set my crossover to 120Hz and my speakers to small. My mains are not participating when running the sweep, which is logical.

Avia does not use the LFE channel. It relies on the BM of your processor. If your mains are set to large, no signal will be sent to the sub (unless set to double up the bass).

Even with a 120 Hz xover, your mains will still be getting a fair amount of signal at the beginning of the sweep.

Pete

 

[Willem Vos]

Even with a 120 Hz xover, your mains will still be getting a fair amount of signal at the beginning of the sweep.

But still, shouldn't the amount of bass information at 100Hz sent to the sub change considerably if I choose the 120 crossover instead of the default 80hz? I'm noticing no change...
the sub really starts playing from 65Hz onward, no matter what.

 

[Anthony_Gomez]

just turn the LFE off and let the LFE get set to the mains which are set to large.

 

[Pete Mazz]

shouldn't the amount of bass information at 100Hz sent to the sub change considerably if I choose the 120 crossover instead of the default 80hz?

Not really. Depends on the slopes of your xover. Anthony's method will take the mains out of the equation and let you just test the sub (recommended).

Unless you are doing a nearfield SPL test, the room will have much more to do with your results than xover settings.

If you want to listen to the difference the xover makes to your mains, then try disconnecting your sub and changing xover points.

Pete

 

[Willem Vos]

just turn the LFE off and let the LFE get set to the mains which are set to large.

Did it. The test cd I burned with the 1-12 octaves popped a lot when switching tracks, though, so I did the AVIA LFE sweep again (Mains set to Large, only sub connected as one of mains. Main speakers disconnected)
with the volume to -30, the meter reads 54dB until 70Hz at which it goes up to 62 and keeps rising to a peak of 82dB at 51Hz.

 

[Willem Vos]

I would burn a test sweep from 10-100hz on an audio track. Then hook up the sub amp to the L/R output on you reciever and make sure that they mains are set to LARGE (IE crossover in the amp is dissabled).

Hooking the sub to the L/R pre-out would allow signals above 120Hz to be sent to the sub... Is this bad for the sub in any way?

 

[Pete Mazz]

Hooking the sub to the L/R pre-out would allow signals above 120Hz to be sent to the sub... Is this bad for the sub in any way?

The sweep only goes to 100 Hz.

Pete

 

[Willem Vos]

The sweep only goes to 100 Hz.

Hmm, you're giving me a very strong "Duh" feeling there
I guess I didn't pose the question very clearly.

Pete, I know the sweep is 100Hz max, but when you play the AVIA disc, there is the intro sound etc.
I turned down the volume before the intro, just in case, but in theory: would sending signals above 120Hz be damaging to the sub?

 

[Brian Bunge]

would sending signals above 120Hz be damaging to the sub?

Not in theory or in practice. A sub driver is a transducer just like any other speaker. You could send it 20KHz tones if you want. It won't damage it.

 

[Willem Vos]

Thanks, Brian. That's good to know.