Axiom Home Page Forums General Discussion Home Theater SVS sub calibration question

Hello
Recently got my new set of Axioms up and running
(sound great..as I expected) but anyway, I have to put my
SVS 25-31 sub along a wall farly close to primary seating.
When I try to calibrate 3-5 db hot using the Rat Shack analog
meter and AVIA the meter will stay at about +3 db over then
towards the end of the test tone the needle will jump about 2db hotter...This (I assume) probably has to do with my sub not being ideally placed..My question is ...Do I calibrate based on where the needle stays fairly constant (+3db) or where the needle jumps to (+5db)

Thanks all...

Hey BIGNORM I don't have the Avia test disc and I'm a bit confused...

Are these different test tones that are being played. ie: you get different readings with different tones?

If its different test tones then you would expect different readings at the different frequencies.

or

Is this white/pink noise being played and you get different readings during the course of it being played?

If its a full spectrum noise then its odd ( in my limited experience )you would get such variation. It really shouldn't fluctuate much at all; unless, this is the way the disc test tone is made. Hopefully someone with this disc can comment on a similar experience or not. Otherwise all I can suggest is make sure something extraneous isn't causing this, such as yourself moving infront of the metre or some thing moving in the room.


Sorry I can't be of more help, Jag

I calibrate based on where the needle stays most constant, but I have absolutely no idea what I'm talking about. I'd very much like to hear the right way to do it.

Ohhh hey, I just of something else.

What are you're settings on the SPL metre? They should be C-weighted and set to SLOW. If the response is set to FAST then the needle will bounce around alot more.

So far I have used the test tones from either my reciever or ones I've made using some software and burnt to CD. In all cases white/pink noise or individual test tones I really don't see any kind of fluctuation.

Another point, you're really only talking about +/- 2db decibles here from either reading. Given this is the sub you're calibrating against the rest of the system, and not say a left main against the right main, I don't think you'll notice much difference where you take your reading.

If none of these suggestions reduce the variation I'd simply choose your most constant reading ( + 3db) and be done with it. In reality you'll likely be adjusting the sub output on the back panel for difference sources anyways.

Cheers, Jag

Michael, nice work on that new avatar!

Sorry - I'm useless on topic.

In reply to:

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Do I calibrate based on where the needle stays fairly constant (+3db) or where the needle jumps to (+5db)

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if your SPL is set up right, you set based on the constant.

Thanks Tom, much appreciated!

Cheers, Mike

Ok
Thanks for all the responses....
based on the comments..I think I did it right...(calibrate based on where needle stays constant)...But after watching some movies (Godzilla , Van Helsing) It seemed to me the sub was calibrated too hot...So what I did was use the Rat Shack meter to get close, then I fined tuned the sub by playing and
re-playing some scenes from movies until I liked what I heard.
I like to watch movies really loud and after I tuned the sub with my ear I got the meter out and it reads pretty much flat
(85db)

Again thanks for the help!!!!!