Power draw by frequency: what am I missing?

JerryLove

JerryLove

Audioholic Samurai
May be so, but again, I linked that article only because it happens to contain the frequency contents of music of different genre, that should allow us to see what sort of load we can reasonably expect the subwoofer to take from the main speakers with high pass crossover set to 80 Hz and above.
I don't appear to be reading the charts the way you are. My understanding is that the value on the chart is the deviation from average. So, if the line is "40db", then the peak is Average+40db. Nowhere do I see what the average is. I therefore don't know if the peak is 40db absolute, or 140db.

No the area I refer to is below 200 Hz. The article does not specify the exact range other than stating the frequency axis scale is in kHz. If you look at the graphs, you can see Fig.1 shows 0 to 10 kHz, it looks like log scale, and the you can clearly see it shows contents well below 200 Hz.
Yes. I can see that. And in every case (except perhaps Pop2),the line is already on a downward slope as it passed "0.2" (200 Hz)

It actually did mention say something above the range below 200 Hz:

"Speech is only locally surpassed by chamber music in the lowest two frequency bands ([110 Hz to 140 Hz]; [140 Hz to 177 Hz]) and by orchestra and opera in the lowest band."

"lowest band" has to refer to below 110 Hz, I would assume, reasonably.
I don't agree with that assumption. I would read lowest band as "110Hz to 140Hz" as that's the lower of the "lowest two frequency bands".

Regardless: can we agree that there's nothing we would describe as a "massive increase in SPL" occurring below 80Hz in any of those graphs?
 
highfigh

highfigh

Audioholic Slumlord
I can see where this might be true for 2-way or small 3-way speakers, but it is unlikely to be true for larger 3-way or 4-way towers.
I think Mark's comment about the power demand on AVRs using a sub may be in the user cranking it louder because "I didn't hear any distortion, so I kept going louder".
 
Steve81

Steve81

Audioholics Five-0
I like to get as much headroom as I can afford but that's just me being crazy. I have never said anything about removing 40 and 80 Hz would give 6 dB to work with, no idea why you bring that up. I thought we were generally in agreement on the topics discussed. I also agree with irv and Verdinut, the only remarks I disagree with was TLSG's mainly because I thought it seemed like a blanket statement and I might have misunderstood him too.
To toss my pennies into the discussion...I cross my speakers over to a sub up at 120Hz. In spite of that, and knowing that much of the time the subs are taking *some* of the load off, I prefer not to use that to fudge how much power I'm likely to need from my speaker's amplification. Why? Because unless I'm willing to sit and verify it to the contrary (I'm not), there's always the possibility that I can run into sustained peaks which have little energy at or below 120Hz.
 
P

PENG

Audioholic Slumlord
Regardless: can we agree that there's nothing we would describe as a "massive increase in SPL" occurring below 80Hz in any of those graphs?
That's the kind of general/blanket statement I could agree to, so yes..
 
P

PENG

Audioholic Slumlord
To toss my pennies into the discussion...I cross my speakers over to a sub up at 120Hz. In spite of that, and knowing that much of the time the subs are taking *some* of the load off, I prefer not to use that to fudge how much power I'm likely to need from my speaker's amplification. Why? Because unless I'm willing to sit and verify it to the contrary (I'm not), there's always the possibility that I can run into sustained peaks which have little energy at or below 120Hz.
I agree to that too. I can agree to you and Jerry while disagreeing with someone else on a specific related point at the same time.
 
mtrycrafts

mtrycrafts

Audioholic Slumlord
One could also measure the sub's sensitivity, perhaps at a couple of frequencies, then for sure know what it would take to reach 105 dB or even up to 115 dB peak reference level. Maybe the sub in TLS guys setup is very sensitive and doesn't need all that power for the cannon shots as mine does. :)
Perhaps sub sensitivity is nowhere near what full range speakers are as a whole.

And, an afterthought, does a room come into the picture for subs power needs to energize a space?
 
P

PENG

Audioholic Slumlord
One could also measure the sub's sensitivity, perhaps at a couple of frequencies, then for sure know what it would take to reach 105 dB or even up to 115 dB peak reference level. Maybe the sub in TLS guys setup is very sensitive and doesn't need all that power for the cannon shots as mine does. :)
Perhaps sub sensitivity is nowhere near what full range speakers are as a whole.

And, an afterthought, does a room come into the picture for subs power needs to energize a space?
I highly doubt TLSGuy would use a sub with his main transmission line speakers of his own design and are supposedly truly full range.
 
Matthew J Poes

Matthew J Poes

Senior Audioholic
Staff member
One could also measure the sub's sensitivity, perhaps at a couple of frequencies, then for sure know what it would take to reach 105 dB or even up to 115 dB peak reference level. Maybe the sub in TLS guys setup is very sensitive and doesn't need all that power for the cannon shots as mine does. :)
Perhaps sub sensitivity is nowhere near what full range speakers are as a whole.

And, an afterthought, does a room come into the picture for subs power needs to energize a space?
I’m general subwoofers are less sensitive. Their sensitivity is more dominated by the enclosure design than the driver. Where as a driver may be very sensitive, say 95dB at 1khz, when loaded into a small sealed box and restricted to sub frequencies, it might only be 75dB over day 50hz to 100hz. To make drivers that have a very low Fs and produce deep bass in small enclosures with affordable magnets, many sub drivers have a high moving mass and lowish BL, which leads to relatively low sensitivity in that same bandwidth.

My biggest subwoofer is a pro 18” driver with a fairly powerful magnet and high moving mass for a pro driver (but low by sub standards). It produces around 97dB at 500hz with 2.83v/1M, but that’s reduced by about 10dB once you look over the actual operating bandwidth. I haven’t actually tested it since it was so heavy, but I did some inside testing and it seemed close enough to assume the simulations were right.
 
Steve81

Steve81

Audioholics Five-0
My biggest subwoofer is a pro 18” driver with a fairly powerful magnet and high moving mass for a pro driver (but low by sub standards). It produces around 97dB at 500hz with 2.83v/1M, but that’s reduced by about 10dB once you look over the actual operating bandwidth. I haven’t actually tested it since it was so heavy, but I did some inside testing and it seemed close enough to assume the simulations were right.
FWIW, Josh over at data-bass has measured several off-the-shelf 18" drivers in his sealed 4.2CF test enclosure. One "average" example is the Dayton UM18-22, which puts up 88-90dB w/ 2V @ 1m from 50Hz-100Hz. Of course, there's this big horn loaded SOB that pushes 100dB w/ 2V @ 1m over the same range :D
 
mtrycrafts

mtrycrafts

Audioholic Slumlord
I highly doubt TLSGuy would use a sub with his main transmission line speakers of his own design and are supposedly truly full range.
Perhaps the low driver in his speakers then? He stated that his low end doesn't take much power at all, I think.
 
Matthew J Poes

Matthew J Poes

Senior Audioholic
Staff member
FWIW, Josh over at data-bass has measured several off-the-shelf 18" drivers in his sealed 4.2CF test enclosure. One "average" example is the Dayton UM18-22, which puts up 88-90dB w/ 2V @ 1m from 50Hz-100Hz. Of course, there's this big horn loaded SOB that pushes 100dB w/ 2V @ 1m over the same range :D
Yeah my own test showed that the pro driver i used and the Dayton reference 18 in the same box had about the same in-room sensitivity between 40hz and 65hz. The Pro driver is getting a bit more sensitive after that point and is pretty good by 100hz, closer to its 97dB. Without eq it has a very tilted response. Fully eqed a 2.83 volt signal in room was just about 87-88dB from 30hz to 100hz.
 
P

PENG

Audioholic Slumlord
Perhaps the low driver in his speakers then? He stated that his low end doesn't take much power at all, I think.
Interesting point, I guess it is possible. Knowing him (electronically), I would think that he might have taken some measurements before he make those statements.
 
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