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How can I get rid of a 4khz-8khz room spike?

Using different speakers in various positions and measuring room response with a RS SPL meter, I get a consistant 10 db spike over the 4-8 khz range in my small 11x13 listening room. I have just installed a full complement of room tunes and now must decide on other acoustic treatments and/or tweaks to incorporate. I have yet to place anything other than a small loveseat and leather chair in the room, so the walls are barren. What would best attenuate this 4-8khz bump - wool tapestries, rigid fiberglass, diffusion panels, other???
nanotweeter
cincy_bob
270 posts
 
Nanotweeter, if you launch the link in Herman's post above, you will see a 2001 thread that was initiated by Sean and that includes a compensation chart of adjustments that need to be made at each 1/3 octave interval in order to adjust for the inaccuracies of the Shack meter. Those compensation adjustments are summarized below:

10Hz.....+20.5
12.5Hz...+16.5
16Hz.....+11.5
20Hz.....+7.5
25Hz.....+5
31.5Hz...+3
40Hz.....+2.5
50Hz.....+1.5
63Hz.....+1.5
80Hz.....+1.5
100Hz....+2
125Hz....+0.5
160Hz....-0.5
200Hz....-0.5
250Hz....+0.5
315Hz....-0.5
400Hz....0
500Hz....-0.5
630Hz....0
800Hz....0
1kHz.....0
1.25kHz..0
1.6kHz...-0.5
2kHz.....-1.5
2.5kHz...-1.5
3.15kHz..-1.5
4kHz.....-2
5kHz.....-2
6.3kHz...-2
8kHz.....-2
10kHz....-1
12.5kHz..+0.5
16kHz....0
20kHz....+1

Add the above numbers to your SPL meter readings in order to obtain the actual SPL level in your room at each 1/3 octave interval. Given the -2dB compensating adjustments required at your problematic treble frequencies, I think you will find that you still have a reduced but still very sizable 8dB or so frequency response spike throughout those frequency bands.
eldartford
4,262 posts
 
Nanotweeter...If you must use the RS meter, use it with the Rives Audio CD that has tracks which are corrected for the RS meter error.

My personal experience is that a spectrum analyser (such as the Behringer DEQ2496) is a thousand times better.
cdc
1,785 posts
 
I have a similar room - 13' x 15' and highly reflective. Nasty 8 dB peak in same area you have. At one point I had the room entirely covered with carpets and blankets and such and still the same peak. Didn't matter which speakers I used until.....
I have now solved the problem by changing speakers - and no acoustic treatment. I went to a single driver speaker which beams over 3kHz so no room reflections. Works GREAT in a small room such as yours. It's like listening to headphone but with great soundstaging.
Some good full range drivers:
Jordan JX92s (~$310/pr)
Adire WR-125 or FR-125 from www.creativesound.ca ($150/pr)
Tang-Band W4-1320 available July from www.partsexpress.com ($75/pr.)
Other brands: PHY, AER, and Fostex FR-120 or FR-200.
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