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Discussion Starter #1
Recently got a SoundBlaster sound card so I could start using RoomEQ to measure this sonosub of mine:



Long story short, here is the NATURAL FR at the seat, no EQ needed! :laugh:


Quick stats:
7' tall, 28" wide tube, 36" wide baseplate
700+ liters raw, 651 effective liters
8" diameter port, tuned to 13.5hz
Ascendant Audio Avalanche 18 driver
Carvin hd1800 amp

It goes very low, very loud, and plays VERY clean. Two, possibly three more on the way at a cost of about $750 each. If you have the space, it's the mother of all bang for the buck's :T
 

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SteveCallas said:
Recently got a SoundBlaster sound card so I could start using RoomEQ to measure this sonosub of mine...here is the NATURAL FR at the seat, no EQ needed! :laugh:
:T

Steve:

I've seen your sub and many of your posts elsewhere (btw, looks great) although this is the first time I've seen measurements, I think. Awful **** good FR with no eq and more evidence that DIY is the best way to avoid the subwars! Mind sharing what your feeding your souncard from?

RS meter? ECM 8000 (calibrated or no?) w/ mic preamp? or something else?
 

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Discussion Starter #5
Digital RS spl meter - what I have found, as have a few others as well, is that if you are using a newer model digital RS meter and using the line out from it as opposed to the meter readout, correction should already be applied and it is a pretty accurate device. This becomes more evident with close mic measurements. This is not the case with the analog version or either version's display, only the digital unit's line out.
 

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SteveCallas said:
Digital RS spl meter - what I have found, as have a few others as well, is that if you are using a newer model digital RS meter and using the line out from it as opposed to the meter readout, correction should already be applied and it is a pretty accurate device. This becomes more evident with close mic measurements. This is not the case with the analog version or either version's display, only the digital unit's line out.
Hey Steve... can you tell me what you base this on?

I've got two of the "newer" digital meters on the way for testing but I'm still curious how you found this out or if you've tested any of these.

Thanks!
 

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Discussion Starter #7
Aside from the difference in readout on RoomEQ from what the meter displays (some of which is probably the C weighting compensation), a close mic measurement of a subwoofer will look exactly like it should - flat. If the digital meter's line out fell victim to the dropoff in response like its display does or like the analog version does, then the measured response of a close mic FR wouldn't be flat, it would have large peaks and valleys.
 

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>>>Digital RS spl meter - what I have found, as have a few others as well, is that if you are using a newer model digital RS meter and using the line out from it as opposed to the meter readout, correction should already be applied and it is a pretty accurate device. This becomes more evident with close mic measurements. This is not the case with the analog version or either version's display, only the digital unit's line out.<<<


Hi Steve,

Great to see you here!

This is the first I've heard of this. Very interesting. So if someone had both meters(digital and analog) then the line out from the digital meter should be 7-8dB higher at say 20hz...right? (if someone was looking for an easy way to confrim this)

Tom V.
SVS
 

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Discussion Starter #9
Yeah, should be. Another way would be to compare the line out of the digital to a calibrated mic. I used the close mic response as a calibrated mic test, and it held up. Let me know if you find something different.
 

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SteveCallas said:
Aside from the difference in readout on RoomEQ from what the meter displays (some of which is probably the C weighting compensation), a close mic measurement of a subwoofer will look exactly like it should - flat. If the digital meter's line out fell victim to the dropoff in response like its display does or like the analog version does, then the measured response of a close mic FR wouldn't be flat, it would have large peaks and valleys.
When you say a close mic measurement should be flat, this only applies to ported subs correct? I would assume a sealed design has a natural 6db/octave rolloff without room interaction.
 

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Hi Steve,

I can't find my digital meter..:)

Doing a lot of "upgrades" around the home right now and everything is even more unkempt than usual.

I won't forget to check this when I can though.

Tom V.
SVS
 

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>>>When you say a close mic measurement should be flat, this only applies to ported subs correct? I would assume a sealed design has a natural 6db/octave rolloff without room interaction.<<<

sealed has a 12dB/octave rolloff ported has 24dB(12 from port, 12 from driver---they sum). The FR of either will be dependent on many variables..:)

Tom V.
SVS
 

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oops Brain fart, definitely meant 12db.:laugh: It doesn't make sense that a close mic FR test would be flat for a sealed sub however, I just wanted clarification of how his statement can be applied or if my logic is off.
 

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Discussion Starter #14
I didn't mean completely flat from 1hz-100hz, I meant a flat line until you get to the differentiating aspects of the design - for ported, a sharp drop and then small resurgence after the tuning point, and for sealed, a shallow dropoff below a given point. I guess a better way to describe it would have been expected linearity? If the meter was giving incorrect output, you wouldn't see the close mic FR as it is expected to look, you would see something spiky or a dropoff beginning well too early.
 

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You know the nice part about cylindrical subs is the small footprint. Just blends right in to the corner.:laugh: That is a beast, nice work!
 

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Has anyone verified whether the line out of the digital RS meter is corrected or not?
 

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Discussion Starter #19
Based on the close mic FR measurements I have seen others take as well, the digital line out does seem to be pretty accurate. The best way to test your own meter is to do just that - a close mic FR measurement of your sub. If it comes out smooth and matches the expected FR, all would point to it being accurate.
 

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We tested two of the newer digital meters against my calibrated mic, and similar to the analogs.... they needed correction values as well. The test results are in a thread somewhere in the BFD | REW Forum. We have provided correction values for all the meters on the Downloads page.
 
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