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In Reply to: Re: More like $220 posted by thoriated_tiger on November 4, 2005 at 16:17:52:
my subwoofer still works in large mode. small mode only affects the mains. actually, the panasonic has large and small for surrounds too on a seperate channel.if you're using a radioshack SPL meter, make sure to check out some websites that have EQ curve compensation. the unit isn't entirely flat. it's curve is about 7dB low at 20Hz i believe and rolls off at the treble too. the midrange is pretty flat though.
the 4dB "bump" you're speaking of may acually be a 3dB rolloff unless you're compensating for the response. i don't have the URLs for the sites, there's at least 3 different curves i've seen withing about 1-2dB of each other (i was going to average them), but they're easy to find. i just copied and pasted the curves. hey... why don't i just do that here?
Set the meter for "C" weighted, Slow. For best results, set the meter on a tripod to keep reflections at a minimum. Get a Test CD that has 1/3 octave warble tones like Stereophile Test CD #3. Start with the 1 kHz tone and set the meter at 80 dB and set the 1 kHz tone to show 0 dB on the meter. I would suggest setting the meter at you listening position to see what the response is there. Start the test tones and with the chart I am suppling below, mark the level beside the frequency on the chart. You can do the corrections after you finish. Stand as far from the meter as you can when doing this so reflections off of your body does not influence the reading. Also try not to have anything else to near the meter. This will give you a close approximation of what the frequency response is of your speakers at your listening postion. Below is the correction chart. Everything is added.
(unknown which model this chart is calibrated for. see below for another chart)
20 Hz. _________________20HZ 6.2DB...................+7.5db..........+6.85db (avg.)
25 ____________________25HZ=4.4DB..................+5db.............+4.7db (avg.)
31.5 ___________________31.5HZ=3DB.................+3db.............+3db (avg.) =
40 ____________________40HZ =2DB....................+2.5db..........+2.125db (avg.)
50 ____________________50 =1.3DB......................+1.5db..........+1.4db (avg.)
63 ____________________ 63HZ =.8DB..................+1.5db..........+1.15db (avg.)
80 ____________________ 80 HZ =.5DB.................+1.5db..........+1db (avg.)
100 ___________________100HZ =.3DB.................+2db.............+1.15db (avg.)
125 ___________________125HZ =.2DB.................+.5db............+.35db (avg.)
160 ___________________160 =.1DB......................-.5db.............-.2db (avg.)
200 _Start______________ Flat.................................-.5db.............-.25db (avg.)
250 ___________________ Flat
315 ___________________ Flat
400 ___________________ Flat
500 ___________________ Flat
630 ___________________ Flat
800 ___________________ Flat
1kH___________________ Flat
1.25___________________ Flat
1.6 ____________________1600HZ = .1DB
2 ______________________2000HZ =.2DB
2.5 _Start_______________ 2500HZ =.3DB
3.15____________________3150HZ =.5DB
4 ______________________4KHZ =.8DB
5 ______________________5KHZ =1.3DB
6.3 _____________________6.3KHZ =2DB
8 ______________________8KHZ =3DB
10 _____________________10KHZ =4.4DB
12.5____________________12.5KHZ =6.2DB
16 _____________________16KHZ =8.5DB
20 _____________________20KHZ =11.2DBClayton- are these corrections needed to make Radio Shack meter readings accurate? Do I add 6.2DB at 20 HZ and 11.2 DB at 20KHZ?
Yes, these make it pretty darn accurate. A lot of people have had their meter calibrated and this was the average correction. All corrections are added as you say. (AUDIO ASYLUM)
More compensation numbers from a subwoofer site for the ANALOGUE model.
At 10Hz add 20dBs to the meter's readings and at ...
12Hz add 16.5dB
16Hz add 11.5dB
20Hz add 7.5dB
25Hz add 5dB
31.5Hz add 3dB
40Hz add 2.5dB
50Hz add 1.5dB
63Hz add 1.5dB
80Hz add 1.5dB
100Hz add 2dB
125Hz add .5dBanother set of analogue meter compensation numbers:
Correction Values for Radio Shack SPL Meter.
10hz........+20db
12.5hz.....+16.5db
16hz........+11.5db
20hz........+7.5db
25hz........+5db
31.5hz.....+3db
40hz........+2.5db
50hz........+1.5db
63hz........+1.5db
80hz........+1.5db
100hz......+2db
125hz......+.5db
160hz......-.5db
200hz......-.5db
250hz......+.5db
315hz......-.5db
400hz......0db
500hz......-.5db
630hz......0db
800hz......0db
1k...........0db
1.25k......0db
1.6k........-.5db
2k...........-1.5db
2.5k........-1.5db
3.15k......-1.5db
4k...........-2db
5k...........-2db
6.3k........-2db
8k...........-2db
10k.........-1db
12.5k......+.5db
16k.........0db
20k.........+1db
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Follow Ups
- Re: large mode and radioshack SPL meter correction - budget minded 11:36:35 11/05/05 (0)
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