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Old 27th June 2007, 01:55 PM   #1
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Default How loud can you go?

I've just done a quick SPL test for my system in the new room, and I'm curious to see what others measure vs what they simulate. In my medium sized room I get 96 dB about 2.7m away with music. Amp is a chip amp with about 70w into OB mains (vifa P17 and D25 dome tweeter) with a Rythmik sealed 12" sub. I could possibly get higher but I don't want to since it would really be pushing the limits. Speakers are about 88 db efficient.

1w > 88 db @ 1m > 80 db @ listening position
10w > 90 db
20w > 93
40w > 96
70w > 98

When I turn off the sub, I get 2 db less. Hence the mains are putting out 94 db peaks. EQ is 8 db @ 100 Hz for dipole roll off, but it seems to be costing me less in SPL. Perhaps I should make an allowance for room reflections also, but what I'm getting is about what I expect.

Measurement is with a DIY electret mic that is very flat and is calibrated for sensitivity. Unweighted measurements.

What do you guys measure for your systems?
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Old 27th June 2007, 04:45 PM   #2
owdi is offline owdi  United States
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What frequency are you measuring? I've measured 120db at 40hz in some parts of my room, and I can get over 100db at 500hz and up at my listening position (2m from speakers).

My typical listening volume is around 70db though.

Dan
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Old 27th June 2007, 05:15 PM   #3
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My budget array does well.

>126dB[c] midbass
~122dB[c] midrange
~115dB[c] treble

From 12 feet away.

http://www.youtube.com/watch?v=t3z-qXOOjQE

Distortion heard is the camcorder microphone getting
punished and distorting due to high SPL.

In reality, the sound is very clean and I listen to it
at those levels when cranking my DVD concerts. /sweet

In the video, there is no subwoofer, center or surround speaker
playing, just two towers.



This is pretty good for a budget design. It exceeded my
SPL expectations.

I can do more if I double up my amps and do the ferrofluid
mod to the midwoofers.
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Old 27th June 2007, 05:44 PM   #4
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When using SPL detection equipment like your Radio Shack meter, there should also be a source "test" signal, not just the output from a DVD or CD ... unless said DVD / CD is / has a "test track". (The Radio Shack device is quite good, as far as it goes ... I have one myself, but ...)

One of the best ways to get good comparisons between speaker and sound re-enforcement systems is with a "pink noise source", either a test track or noise generator, that has equally weighted of sound pressure levels across the full human ear's receptive response spectrum (~35 Htz to ~16K+ Htz) ... and the measurements should be made at levels that do not "force" distortion through your amps or speakers. (Audio engineers often refer to "line level" signal strength as a base line for signal voltage levels into an amplifier that should produce undistorted output. This "line level" is often used to "calibrate" VU meters to a "zero" point = neither adding to or subtracting from a 0 db reference.)

Observing momentary bursts of sound pressure levels that make your Radio Shack meter report SPL above +100 db or a "+ 10" on its VU meter (when set to the 120 db range) or even more is not really a good comparison with the full spectrum ...

== A test reference, sound source we can all agree on:
If you have an FM radio tuner in your system, set it to a channel that no local station is using ... you should have a lot of noise (hisssssss ... etc.) that is a far representation of the "pink noise" reference source ... Actually this is called "white noise" and comes from the "pop corn" hiss that your FM tuner detects internally in the absence of a station signal ... This is a prefectly acceptable sound reference source as just about any engineer will tell you. ( http://en.wikipedia.org/wiki/Pink_noise and http://en.wikipedia.org/wiki/White_noise )
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Old 27th June 2007, 08:03 PM   #5
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I can hit over 120dB using a noise test. lol
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Old 28th June 2007, 02:16 AM   #6
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Dan, I'm measuring with music at my listening position so not any particular frequency. What kind of setup do you have?

Thylantyr, what speakers and amp are you using? That is some serious output!

FastEddy, I'm not really looking for a competition of technically correct comparison. I'm just curious to see what others measure at their listening position with music. Of course, you could cheat by choosing certain music that has high SPL peaks in a narrow band where the speakers can put out more, but I do this test in a way that indicates what my system can do at any frequency. 95 db at the listening position for 20 Hz and up.
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Old 28th June 2007, 02:59 AM   #7
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Just cranked up the system after adding extra filtration / regulation to the pre-amp, plugging in a new turntable ...Player is OppoDigital.com '981 - Pre-amp is Bottlehead ForePlay tube type / driving DIY stereo 150 watt MOSFET amps / output is to Magnepan MMG planar speakers (sub woofer not operating = don't need it for this) ... Source: Van Morrison "Live at Montroux, 1980" DVD Video (24bit - 48k - 5.1 sound track) ... using that Radio Shack gadget above = my comfortable listening level is 'tween 70 and 88 db. ... Max prior to noticable distortion is about 95 db to 98 db. (I do have old rocker ears = bad hearing at some freqs., but I can still detect distortion.)

Now, listening to Beatles "Rubber Soul" (this particular LP has never been played before and sound is brand new). Confortable listening is still around 70 to 80 db ...

If anyone wants the Beatles complete collection, never played LPs, I'll let 'em go for a couple of grand ...
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Old 28th June 2007, 04:12 AM   #8
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I am hoping that one day someone will come over with some good test equipment to find out what the big system will do. I would like to measure the SPL outside at 10 meters not 1 as 1 is unrealistic to try and measure. Anyone in Vancouver?
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