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Discussion Starter #1
Hi there,

I ran Audyessy on my diy dual 18" sealed sub today and it came up with a really short distance of 0.3 metres. Can anyone explain why this is and what I can do to fix it if it is wrong.

One thing I did notice was that when the cal came around to the sub the radiator rattled. Would this have an effect on the distance calibrating.

cheers

Graham
 

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I would think that any noise beyound what the reciever makes will mess up your results so I would stop the rattle and run it again. You can always set the distance manually also.
 

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Discussion Starter #3
Hi there,

So if I set the sub manually to the distance it should be how different will that sound and what effect on it will it have.
cheers

graham
 

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Discussion Starter #5
Ive been getting stressed out with REW today and that was just trying to get the levels sorted out.
I have put up some graphs on my diy thread, perhaps you would be so kind and have a look at them and give me your opinion. I dont have a phase on the sub as it is a diy sub.

cheers
graham
 

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Graham,

As you adjust the distance of the subwoofer in your receiver, this is what you are doing is adjusting the phase. You want the subwoofer to reach your ears and play the note with the same phase as the speakers at the x-over point. You can do this manually with a subwoofer phase control or with the distance parameter on your receiver.

It's essentially the same function.

I'm not sure where your DIY thread is, sorry.
 

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According to Chris at Audyssey, this is an anomaly. I occationally get the same thing when I have the mic on a tripod. What seems to happen is that the audio is picked up through the floor and tripod instead of through the air. The floor is denser, so the sound travels faster, and the distance is off.

Chris said to just adjust manually to the physical distance, and confirm with REW if you can.

I also have had this with subs with no lowpass filters. The high frequency content is so far out of phase that you confuse Audyssey a little.

And regarding using the 'Phase' knob on your sub, I'd much rather use the distance setting in your processor. that is fully linear and work the same for all frequencies. The 'Phase' knob usually work over a frequency band and can mess up even more.
 

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Discussion Starter #9
Hi there,


Thanks for your reply, my sub doesn't have a phase knob as it is connected straight to the behringer 4000. How will I know what the phase is set to with adjusting the distances. Is a shorter distance phase 0 and a longer distance a phase 180. How will I know that I have got the distance set correct?

I will run some more REW tests tonight.

cheers

Graham
 

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If you run the subs direct, there is really no delay unless the amp is 'digital' and introduce any. In that case a good starting point is the physical distance between subs and microphone. Then add delay/distance in the receiver until the crossover area is as good as it gets.
 

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Trial and error.

Do a sweep with the initial distance (physical, measured distance).

Then add a foot, re-measure and see if it got better or worse. Repeat until you narrow it down.
Usually you end up with a foot or two longer than the physical distance, at least I do.
 

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Discussion Starter #13
Can I presume this will alter the graph REW produces. Will adjusting the distance reduce some of my peaks etc.. Audyssey has flattened it out a bit but it still needs some work.

cheers
graham
 

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Don't worry if the Audyssey response isn't flat for a single position. The overall response will be much better that unequalized.

Changing the distance setting will alter the REW curve, as it changes the interaction between mains and subs.
 

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Discussion Starter #15
I am always having nightmares trying to get the levels correct in REW. I have a turtle ARM soundcard and even on max input volume and -15db on the onkyo it still says the levels are only on -30db. Is there an easy way to set up levels that works.

I tried following the online help but I am still not having success. Does it matter if the levels are too low and I also found that when I go to do the speakers after the sub I have to change the levels again. What am I doing wrong.

cheers

graham
 

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Discussion Starter #17
Cheers, Would the fan noise on the behringer EP4000 amp make a difference to the cal set up.

It is located between the centre speaker and the sub on the TV cabinet.

cheers

Graham
 

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Many subwoofers have the phase reversed. If the calculated distance is way off. The first thing I would do is change the phase.
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Discussion Starter #20
As I don't have a phase it has been mentioned that all I need to do is reverse the wires I have going into my speaker plate on my sub to reverse the phase. Is this correct?

cheers
Graham
 
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