AVS Forum banner
Status
Not open for further replies.
1 - 7 of 7 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter · #1 ·
When I try to measure the SPL on my subwoofer, the needle keeps moving +/- 2dB (4 db difference, sounds like rolling thunder). I can get the mains, center, and surrounds steady. I have the Radio Shack analog meter set to C/slow. I've used Avia and my receiver's test tones and they produce the same results. Is there something wrong with my sub? Placement perhaps?


Here's my setup:

Mains: Energy C-1's

Center: Energy C-C1

Surround: Energy Take 2.2

Sub: Energy S8.2

Receiver: Dennon 2803

Room: 14' x 14' with one side completely open to the dining room & kitchen


Thanks.
 

·
Registered
Joined
·
383 Posts
Nothing is wrong with your sub or placement. The needle bouncing like that is normal and is the result of the sub's low freq test tones. That's simply how the meter reacts to such low freqs. Just do the best you can to get the needle about where you want it and you should be fine.


--Steve
 

·
Registered
Joined
·
391 Posts
This is a normal phenomenon. You can virtually eliminate this phenomenon by utilizing warble test tones rather than the standard sine wave tones. I did an extensive yahoo search and finally was able to make my own warble test tone cd with frequencies from 20Hz - 1000Hz utilizing a program called CoolEdit.


Kevin
 

·
Registered
Joined
·
391 Posts
Try this out!

http://www.gti.net/wallin/audio/coolwarb/coolwarb.html


I actually saved each warble tone frequency as a unique track. I then burned each track to a CD. I set each warble tone to last for 10 seconds. I can either wait for the 10 seconds to elapse, or hit the next track button when I am ready. I liked this control better than having each tone separated by a brief quiet time. It also allows me to know the track number of each tone frequency if I need to go back to one or more.


Kevin
 

·
Registered
Joined
·
1,077 Posts
Actually there are a couple of issues going on here;


IIRC, AVIA's test tone for bass frequencies is known to utilize the bass management of the prepro (i.e no sub-only output test signal) and the signal alternates it's output, which likely causes the SPL meter swing. The Video Essentials (VE) test DVD doesn't have this problem and has a sub-only test signal of bass frequency pink noise.


Another factor that affects the SPL meter reading is caused by room modes. Room modes are bass frequency reflections --due to room dimensions (LxWxH)-- that cause SPL meter spikes. Warble tones will help reduce this.
 
1 - 7 of 7 Posts
Status
Not open for further replies.
Top