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Graph explanation please

post #1 of 10
Thread Starter 
Why when L+R + sub combined am i getting higher spl's in the Lowest frequencies ??

I did not change any Vol settings when taking all 3 measurements ??

Measured with REW and EMC800 mic

Edited by randyc1 - 1/24/13 at 11:10pm
post #2 of 10
Why would you expect otherwise? Think about it.
post #3 of 10
Thread Starter 
Quote:
Originally Posted by lovinthehd View Post

Why would you expect otherwise? Think about it.
Quote:
Originally Posted by lovinthehd View Post

Why would you expect otherwise? Think about it.

How about the fact that the mains have no where near the capability of playing 20 to 40 hz ,... where is the extra spl coming from ??
post #4 of 10
Quote:
Originally Posted by randyc1 View Post

Quote:
Originally Posted by lovinthehd View Post

Why would you expect otherwise? Think about it.
Quote:
Originally Posted by lovinthehd View Post

Why would you expect otherwise? Think about it.

How about the fact that the mains have no where near the capability of playing 20 to 40 hz ,... where is the extra spl coming from ??

Depends. What mains? You don't mean low pass vs crossover? You don't say much about the specifics of your setup or room let alone how you're measuring it.... so far I don't see any reason not to get higher spl when you run all speakers together (although the sub plus mains does mirror the sub alone pretty evenly so maybe with more information that might become more apparent why).
post #5 of 10
Thread Starter 
Quote:
Originally Posted by lovinthehd View Post

Depends. What mains? You don't mean low pass vs crossover? You don't say much about the specifics of your setup or room let alone how you're measuring it.... so far I don't see any reason not to get higher spl when you run all speakers together (although the sub plus mains does mirror the sub alone pretty evenly so maybe with more information that might become more apparent why).



The mains are very small Kef speakers, measured with REW and EMC8000 mic
post #6 of 10
I suspect it has something to do with the way the signals are routed through your system-and when the receiver sees the same signal applied to both it routes it to the sub also.

The only way to be sure whether it is the system or speakers themselves is to bypass ALL of the processing and go directly into the amp-and then measure.

If you can't go directly into the amp (NOT the receiver inputs unless they have a amp in jack) would be to unplug all the speaker wires and hook them up one at a time. That way if a signal is being routed somewhere else you won't hear it.
post #7 of 10
Quote:
Originally Posted by randyc1 View Post

Why when L+R + sub combined am i getting higher spl's in the Lowest frequencies ??

I did not change any Vol settings when taking all 3 measurements ??

Measured with REW and EMC800 mic

I presume that you are obtaining the response curves you see because you adjusted your system in such a way that those curves are a logical consequence of your adjustments.

I would then rephrase your question to be: "Why have I adjusted my system with a response curve that is gently tipped up at the bottom."

There are several answers to that question.

(1) It is what you prefer, and so be it!
(2) There is some asymmetry between what you measure and what you hear
(3) The actual degree of tip-up is within the natural imprecision of your preferences and your measurements.

What I see doesn't surprise or concern me at all. I bet it sounds pretty good!

I see people around here who seem filled with angst when they find out that their systems aren't 20-20 KHz +/- 1 dB. I think that their expectations are far in excess of what can be delivered consistently with the current SOTA. Trust me, nobody is listening to recordings that were, as mixed and mastered made with that kind of precision. They don't exist and they probably can't exist!
post #8 of 10
Quote:
Originally Posted by lovinthehd View Post

Quote:
Originally Posted by randyc1 View Post

Quote:
Originally Posted by lovinthehd View Post

Why would you expect otherwise? Think about it.
Quote:
Originally Posted by lovinthehd View Post

Why would you expect otherwise? Think about it.

How about the fact that the mains have no where near the capability of playing 20 to 40 hz ,... where is the extra spl coming from ??

Depends. What mains? You don't mean low pass vs crossover? You don't say much about the specifics of your setup or room let alone how you're measuring it.... so far I don't see any reason not to get higher spl when you run all speakers together (although the sub plus mains does mirror the sub alone pretty evenly so maybe with more information that might become more apparent why).

Actually, randy is right. There are few if any mains that are actually capable of robust response in the 20-40 Hz range. I've been posting reliable evidence to that effect for several months. I presume that either my posts are completely over your head or that they have zero credibility with you and I'm wasting my time repeating this information right now.

Just to re-iterate the more robust L&R speakers that I see people using around here have 3 each 7 inch woofers. If those woofers were SOTA units (I suspect that most are only about 1/3 as good as I am modeling them to be) they would have the following power response for low distortion:

Freq,Hz Max SPL, DB

10 79
20 91
30 98
40 103
50 107
60 110
70 113
80 115
90 117
100 119
110 120
120 122
130 123
140 125
150 126
160 127
170 128

From practical experience I know that due to the insensitivity of the ear, it takes a lot of SPL below 50 Hz to grab people by the sensitive parts and really give them the bass experience that they are hoping for.

A SOTA high end system probably needs to generate a clean 110-120 dB @ 20-30 Hz with low distortion to be really sufficient.

A robust home theater system needs to come within 10 dB of that (100-110 dB) in the 20-30 Hz range.

A pleasing system that is not all that impressive but nice enough to listen to needs to be able to generate a clean 100+ dB in the 30-50 Hz range and above.

Since virtually every tower speaker on the market today except for perhaps some really well-built speakers that are probably in the 4 or 5 figure range fail or barely match any of the criteria I mention in the previous paragraph, virtually every home system needs a subwoofer. Furthermore, a subwoofer that costs under $1,000 can be matched up with L & R speakers costing less than $500 each and deliver equal or better over-all bass then those high end nearly 5-figure floor-standers. The other benefit of subwoofers is that they allow you to optimize the generation of bass separately from the generation of the rest of the audible range. IOW you put your main speakers where they work best and you put the subwoofer(s) where they work best and it always turns out that the twain never exactly meet.
post #9 of 10
Its true that even if a speaker is flat down to 40Hz it doesn't mean it will generate enough distortion free output to be adequate. My L/C/R speakers measure flat down to about 40Hz in room but cannot produce much sound at that frequency for me to say they are adequate at low frequencies. A good sub can easily produce all the sound needed up to above 80Hz.
post #10 of 10
Thread Starter 
Ok guys thanks anyways,... John the author of REW explained on another forum the reason for the higher low freq spl's .
It's because i was only using the Left AUX input when Measuring SUB ,... When measuring ALLl together , sub recieved an additional signal from Right AUX input which adds 6db of LFE signal to Sub !!
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