T60 Limit

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Bruce Weldy
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Re: T60 Limit

#16 Post by Bruce Weldy » Wed Aug 22, 2018 6:05 pm

Bill Fitzmaurice wrote:
Wed Aug 22, 2018 3:37 pm
SethRocksYou wrote:
Wed Aug 22, 2018 1:33 pm
I can hear 25hz just fine
If I had a dollar....
What you're hearing is harmonics of 25Hz. To know what you're capable of hearing you need a sine wave generator, a speaker with essentially no harmonic distortion, a Z weighted sound meter and an RTA to see what's present. It just so happens that I have all of those. I can play a 25Hz tone at 100Hz outdoors, with no audible harmonics, and not hear a thing. The meter tells me it's there, stuff within 50 feet vibrating like mad tells me it's there, my skin tingling and chest being pounded tell me it's there, but if not for that you wouldn't know there was any sound. Having below 30Hz capability is nice indoors for HT, where you literally feel the room pressurization, but where music is concerned it's a capability you don't need and can't use.
I can play a 25Hz tone at 100Hz outdoors,

I'm sure that's a typo and should be 100db.

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Re: T60 Limit

#17 Post by SethRocksYou » Wed Aug 22, 2018 7:40 pm

Bill Fitzmaurice wrote:
Wed Aug 22, 2018 3:37 pm
What you're hearing is harmonics of 25Hz...
Perhaps. You would know way more than me about that stuff. However, google indicates the audible frequency range down to 16Hz for some people. And really, it doesn't matter. I like what I hear, whether it be harmonics or not. And, fact is, I wouldn't hear whatever it is that I hear if my headphones/earbuds/subwoofers were high passed at 40hz. Whatever it is, it's big, fat, and lumpy... and I like it. :)

Enjoy the harmonics https://youtu.be/2UJwcRDYIH4 :D

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Re: T60 Limit

#18 Post by SethRocksYou » Wed Aug 22, 2018 7:41 pm

Bruce Weldy wrote:
Wed Aug 22, 2018 6:05 pm
I'm sure that's a typo and should be 100db.
Yeah, that's the only thing that makes sense. Question is, was it dBZ, dBC, or dBA?

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Re: T60 Limit

#19 Post by Bill Fitzmaurice » Wed Aug 22, 2018 9:07 pm

100dBZ. Google is incorrect. It may seem that some people can hear 16Hz, but it's harmonics, not fundamentals. Even very large mammals can't hear that low. One reason why is that 50 foot and longer wavelengths pass though our bodies easily enough that they appear on both sides of the eardrum with insufficient phase and pressure differential to excite it. Elephants do use ultra low frequencies to communicate over very long distances, but not with their hearing. They sense ground conducted sound waves with their feet.

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Re: T60 Limit

#20 Post by SethRocksYou » Wed Aug 22, 2018 10:27 pm

Well, ya got me thinking Bill. Again. LOL

A couple years ago I made a rig to EQ all the band members IEM's flat (Waste of time BTW). Pretty simple. Just a short piece of clear plastic hose/tubing shoved on the end of a Dayton Audio iMM-6 Calibrated Measurement Microphone and the ear bud placed in the open end. I made the length of hose my best guess, as close to what I thought an ear canal might be. Not scientific, but maybe it would at least be able to indicate what frequencies are being produced by my ear buds when fed sine waves. I'll see if I can find it in my pile of random audio stuff.

Wouldn't 100dBZ at 25hz be essentially only about 55dBA?

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Re: T60 Limit

#21 Post by CoronaOperator » Wed Aug 22, 2018 11:17 pm

We use dual T60's at our club because they only get moved to wax the dance floor. Hauling those beasts around for a mobile rig IMO is ridiculous even for EDM unless you have a warehouse, huge trailer, and lots of young helpers. 4 T45's will not only get you to 30hz, but have more sensitivity at 30hz than the T60's.

25 hz indoors is a lot of fun ... when it happens. Out of the 60 EDM shows we did at our club in the last year, I can count on 1 hand how many tracks the DJ's played that actually dropped that far (and on to 20hz) on a fundamental. Pretty neat experience having the entire club vibrate considering the walls are 18" thick brick but very rarely does anybody have tracks that can dig that deep. Also, I'm sure it was only me, the DJ's, and maybe some staff that went crazy over it. I doubt anyone else even cared, for most people these are social events. If you want that experience outdoors then set up within 100 yards of a train track, not even the pro's attempt 25 hz outdoors, it's just not going to get that visceral experience without a train going by, although a full gravel truck going down the right road (bumpy) can get close.

In the end if it isn't a permanent install and you want to rent out the system then logistics of storage, transportation, lifting it and room to set up the system outweigh that last 5hz. I am personally getting out of the night club business in 2 weeks (after 18 years), the T60's are staying put and I am building T45's to go mobile with. If you need lower for personal listening, then build a THT for home use.
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Re: T60 Limit

#22 Post by Bill Fitzmaurice » Thu Aug 23, 2018 7:02 am

SethRocksYou wrote:
Wed Aug 22, 2018 10:27 pm
maybe it would at least be able to indicate what frequencies are being produced by my ear buds when fed sine waves.
The problem there is that even if the signal is devoid of harmonics the speaker reproducing them will create them. The only speaker configuration that doesn't create its own high level harmonics is the folded horn. The driver still creates them, but the horn filters them out.
Wouldn't 100dBZ at 25hz be essentially only about 55dBA?
It would, and that's why dBA meters are useless for music. Even dBC meters are only accurate to about 40Hz.
If you want that experience outdoors then set up within 100 yards of a train track, not even the pro's attempt 25 hz outdoors
+1. I took RTAs at a major venue for three years, over 100 concerts. They all showed pretty significant content from 16 to 32Hz. The problem was they showed the exact same levels from 16-32Hz whether the band was playing or not. What the meter was reading was the VLF content created by the foot traffic of the crowd, the generators powering the food trucks, even highway traffic a half mile away. In a similar vein many newbies have taken RTAs of their subs in their homes, and gotten giddy when they saw how much they were reading below 30Hz. That was until they took an RTA with the system off and saw the same below 30Hz content, finally tracking it down to heating/cooling systems, refrigerators, and road traffic.

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Re: T60 Limit

#23 Post by ACUA » Thu Aug 23, 2018 1:34 pm

I built 4 t45s because I really wanted strong content below 45hz, in my vehicles I have always had big bass systems and really wanted that content down low, most pro gear does not go below 45hz and that was one exciting aspect of the bfm tuba cabinets to me. Now that I have been playing them for over a year now at all kinds of places, I realize that I’m about the only one involved who cares about sub bass,most venues can’t handle a ton of sub bass and only about 20% of the material I play hangs out in that 30-40hz range. If I could go back, I could build a 3” taller cab and had more bang for my buck. I should have built t48s.
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Re: T60 Limit

#24 Post by SethRocksYou » Thu Aug 23, 2018 2:37 pm

Bill Fitzmaurice wrote:
Thu Aug 23, 2018 7:02 am
SethRocksYou wrote:
Wed Aug 22, 2018 10:27 pm
maybe it would at least be able to indicate what frequencies are being produced by my ear buds when fed sine waves.
The problem there is that even if the signal is devoid of harmonics the speaker reproducing them will create them. The only speaker configuration that doesn't create its own high level harmonics is the folded horn. The driver still creates them, but the horn filters them out.
That's what I would hope it would show. Whatever the earbuds are producing. I think it would be interesting to see a visual representation of what your saying.
Bill Fitzmaurice wrote:
Thu Aug 23, 2018 7:02 am
Wouldn't 100dBZ at 25hz be essentially only about 55dBA?
It would, and that's why dBA meters are useless for music. Even dBC meters are only accurate to about 40Hz.
Just my uneducated thought... That doesn't seem very loud, given our ears lack of sensitivity at that frequency. I'd think it would absolutely be nearly impossible to hear at that volume. Not the case? Can't hear it at any volume? Only harmonics? I trust you Bill, but my eyes want to see proof. My mind doesn't want to believe it.

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Re: T60 Limit

#25 Post by Bill Fitzmaurice » Thu Aug 23, 2018 5:33 pm

Look at a dBA chart and a dBZ chart. The dBA figure is low not because it isn't loud, it's low because dBA doesn't measure lows. That's why dBA is never used to measure speakers.

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Re: T60 Limit

#26 Post by SethRocksYou » Thu Aug 23, 2018 8:44 pm

Bill Fitzmaurice wrote:
Thu Aug 23, 2018 5:33 pm
Look at a dBA chart and a dBZ chart. The dBA figure is low not because it isn't loud, it's low because dBA doesn't measure lows. That's why dBA is never used to measure speakers.
Guess I'll have to research that stuff again... I thought dBA was intentionally weighted to the natural response of the human ear, so that different frequencies at the same dBA "sound" the same volume. No?

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Re: T60 Limit

#27 Post by Bill Fitzmaurice » Thu Aug 23, 2018 8:58 pm

No. What it more or less reflects is how sensitive the ear is to damage at various frequencies, so its main use is in measuring industrial noise. If you need to adhere to OSHA noise exposure standards, which uses dBA, then you use a dBA meter. Otherwise it's rather useless.

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Re: T60 Limit

#28 Post by SethRocksYou » Fri Aug 24, 2018 1:13 am

A couple quotes from this link https://en.wikipedia.org/wiki/Weighting_filter which seems to speak to what both of us has stated. Not sure that it makes anything more clear though. LOL Interesting conversation point none-the-less.
In the measurement of loudness, for example, an A-weighting filter is commonly used to emphasize frequencies around 3–6 kHz where the human ear is most sensitive, while attenuating very high and very low frequencies to which the ear is insensitive. The aim is to ensure that measured loudness corresponds well with subjectively perceived loudness. A-weighting is only really valid for relatively quiet sounds and for pure tones as it is based on the 40-phon Fletcher–Munson equal-loudness contour
The A-weighting curve has been widely adopted for environmental noise measurement, and is standard in many sound level meters (see ITU-R 468 weighting for a further explanation).

A-weighting is also in common use for assessing potential hearing damage caused by loud noise, though this seems to be based on the widespread availability of sound level meters incorporating A-Weighting rather than on any good experimental evidence to suggest that such use is valid.
Human sensitivity to noise in the region of 6 kHz became particularly apparent in the late 1960s with the introduction of compact cassette recorders and Dolby-B noise reduction. A-weighted noise measurements were found to give misleading results because they did not give sufficient prominence to the 6 kHz region where the noise reduction was having greatest effect, and sometimes one piece of equipment would even measure worse than another and yet sound better, because of differing spectral content.

ITU-R 468 noise weighting was therefore developed to more accurately reflect the subjective loudness of all types of noise, as opposed to tones...

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Re: T60 Limit

#29 Post by Bill Fitzmaurice » Fri Aug 24, 2018 7:18 am

I took those concert RTAs, and was paid very well for doing so, when a major outdoor concert venue was on the verge of being shut down due to noise complaints. This was after they paid $25,000 to a company who supposedly cured the problem, by installing a computerized system in the FOH that would record levels there and illuminate a red warning light when FOH levels reached what they had calculated would impact the neighborhood. The light never went off, the recorded levels were always within limits, and the noise complaints increased, mainly because of high levels of bass. The venue asked me for my opinion on why they still had a problem, which took me all of five minutes to diagnose. The system, and the noise standard the 'professional' sound control outfit had come up with, was A weighted. The neighborhood was awash with bass because the standard didn't consider it, and the system didn't measure it. By no means were the neighbors unable to hear it.

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Re: T60 Limit

#30 Post by SethRocksYou » Fri Aug 24, 2018 10:29 am

That makes sense to me, 100%.

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