SPL meter acting weird

EQ guys are using on their cabs/systems. A good starting place if you don't have your own RTA.
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sine143
Posts: 3066
Joined: Sat Feb 06, 2010 3:27 pm
Location: Raleigh NC

Re: SPL meter acting weird

#31 Post by sine143 »

dont put the mic on such a pedastal :cop:. It may be good quality, it might be pretty flat, but I doubt its razor flat. unless it had a price tag of over 500 it is certainly not flat abouve 5khz, and likely has some LF anomalies as well.
Built:
2x Tuba 30s delta12lf loaded (gone)
4x Otop12 d2512 loaded
8x t48s (18, 18, 24, 24, 30, 30) 3015lf loaded
2x AT (1 mcm, 1 gto 804)
2x SLA Pro (dayton pa6, 6 goldwood piezo loaded)
1x bastard XF208

2x OT212 (delta pro 450a loaded, eminence psd)

Grant Bunter
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Joined: Mon Nov 28, 2011 11:12 am
Location: Ilfracombe Queensland Australia
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Re: SPL meter acting weird

#32 Post by Grant Bunter »

Here's an idea for you MC,

Play the same song/material, at the same volume/voltage, take your new meter out into the corridor with your room door open, and take a new measurement.

Since I've been here on the forum, plenty of people, running any sub at all, in a small room, have observed lack of the lowest of the lows they expect from their cab.
It's also often been said in response to these observations that these designs like a bit of space to perform to their best.

Door open, measuring in the corridor, will do exactly that, and may lead you to different results...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" KL3010LF , 2 x 28" 3012LF.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

MissileCrisis
Posts: 1128
Joined: Sat Dec 15, 2012 1:30 pm
Location: Walnut Creek, California

Re: SPL meter acting weird

#33 Post by MissileCrisis »

Main reason I say it's flat is because it is calibrated flat from Dayton (personal eq file) to within half a db. I will definitely try out what grant mentions. Also by design it doesn't roll off at 60 hz like c weighted spl meters do.
Built
2 x TLAH
1 Titan 39 (lab 12, 15 inch)
1 Tuba 60 (lab 12, 20 inch)
SLA Center
2 x Mini MLTP subwoofers
1 x 212 TH (custom)
2 x Mini-Karlsonators
Owned, but not built
2 x Jack 12 (2512, melded)

MissileCrisis
Posts: 1128
Joined: Sat Dec 15, 2012 1:30 pm
Location: Walnut Creek, California

Re: SPL meter acting weird

#34 Post by MissileCrisis »

I walked around a bit with a 25 Hz sine wave going at 2.9 volts. Here is what I got, my computer area was around 83 dB (7 feet from subwoofer) 2 feet next to it was 82 dB. Now I know it's not the subwoofers fault because...

The opposite side of the room next to my mirror (~10-12 feet) was 93 dB. Thus "1 w/1m" for the sub should be around 93+10+5 - 12 = 96 dB at 2.9 V accounting for corner loading, c-weighting, distance, while assuming spl meter accuracy. In other words, yes, it takes most of the room to even get to an area where the 25 Hz doesn't undergo massive room cancellation. the ~3 dB difference with the chart comes from cabin gain as explained by Bill somewhere. Once I take it outside I'll do proper 1w/1m measurements which will be this weekend assuming the paint dries quickly.
Built
2 x TLAH
1 Titan 39 (lab 12, 15 inch)
1 Tuba 60 (lab 12, 20 inch)
SLA Center
2 x Mini MLTP subwoofers
1 x 212 TH (custom)
2 x Mini-Karlsonators
Owned, but not built
2 x Jack 12 (2512, melded)

byacey
Posts: 948
Joined: Thu Jun 14, 2012 9:09 am
Location: Edmonton, Alberta, Canada

Re: SPL meter acting weird

#35 Post by byacey »

It's pretty hard to come up with a quality calibrated reference microphone for $100 or so. Here's a link to a company that's an authority in this field. I'm not suggesting anyone need go purchase one of these, but it will help anyone performing tests to be aware of the shortcomings of a bargain basement mic.

http://www.bksv.com/Products/transducer ... idges.aspx

http://www.bksv.com/doc/be1447.pdf
Built
T48s
WH8s
SX212

MissileCrisis
Posts: 1128
Joined: Sat Dec 15, 2012 1:30 pm
Location: Walnut Creek, California

Re: SPL meter acting weird

#36 Post by MissileCrisis »

byacey wrote:It's pretty hard to come up with a quality calibrated reference microphone for $100 or so. Here's a link to a company that's an authority in this field. I'm not suggesting anyone need go purchase one of these, but it will help anyone performing tests to be aware of the shortcomings of a bargain basement mic.

http://www.bksv.com/Products/transducer ... idges.aspx

http://www.bksv.com/doc/be1447.pdf
For my purposes, the +- 1 dB accuracy of the dayton xlr calibrated mic is more than sufficient. I'm not trying to publish my results, I just want to room correct and compare my (relative) spl curve to that of the official SPL forum page. Both of which it has handily done. I got it flat to 35 in one listening position and well it's a bad room so the low bass requires a different sitting position.

Thanks again all for enlightening me with all these other choices I didn't know I had.
Built
2 x TLAH
1 Titan 39 (lab 12, 15 inch)
1 Tuba 60 (lab 12, 20 inch)
SLA Center
2 x Mini MLTP subwoofers
1 x 212 TH (custom)
2 x Mini-Karlsonators
Owned, but not built
2 x Jack 12 (2512, melded)

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