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How Loud Do You Need?
- Thread starter watchnerd
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Don, Don, Don,........don't apologize. Your input has been very helpful to me at least. I know I am asking alot, and don't worry a minute about saying so. You don't owe me any serious amount of trouble fixing my misunderstandings.
And Ray, Ray, Ray...........<<<<redacted>>>>.
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I hope everyone knew my missive about 144 db speaker was not serious. On the other hand, maybe the digital microphones will usher in new levels of performance.
https://www.sweetwater.com/store/detail/SolutionDM
Not a bad microphone I suppose. Price just needs to drop by 90%.
No worries, but Work and Life is colliding big-time lately so I just don't have time and energy to dig deep right now.
Fundamentally, do you not understand why the number is ~9N, or do not understand why the discrepancy between the SNR and the SFDR? The latter is easily shown with a picture, I think, but the former requires actually doing some ugly (to me) math. AFAIK there is not a simple closed-form solution for SFDR (though this is not something I've really dug into for years so maybe some bright young researcher discovered one; I just remember the results). The hand waving explanation for the latter is that you look at the difference between the quantization steps and a pure sine wave, generate an equation that describes the errors, solve it, and calculate the ratio between signal and error terms.
Bessel functions work well for these calculations and are pretty cool themselves, but are one of those things that are a step beyond what most working engineers (at least I) deal with daily, and those grad school courses from 30-odd years ago have not all stuck with me. Check them out: https://en.wikipedia.org/wiki/Bessel_function
This would be a good time for ol' what's-his-name to step up and 'splain it to us po' dumb engine-eers who don't "get" the underlying science.
OT: Price aside, somehow I have never been a big Neumann fan, though they produce some sweet vocals. Perhaps because I mostly recorded instrumental ensembles I always seemed to gravitate toward AKG C414 series mics. All I own now are much cheaper and I don't record much anymore (last gig was a few years ago recording a local youth orchestra and generating concert CDs). My most expensive mic now is actually my old Earthworks M30 measurement mic.
It is entirely up to you how loudly you like it, natch. 105 dB is the max set for THX systems (115 dB for subs) so I somewhat arbitrarily picked that. I imagine my system is distorting heavily by that point so hopefully I never get close to really listening that loudly. Since distortion products fall off rapidly with level (exponentially for bipolar transistors, factorially for tubes, square law plus higher-order terms for FETs, and speakers have different distortion mechanisms but again tend to fall off rapidly as volume drops), having some headroom means much less distortion where I actually listen. Having 6 dB of headroom leads to 12 - 18 dB less distortion if you run the math.
I am not a speaker guy, but it makes sense to me that your choice of drivers is driven partly by output, and a driver with lower mass and less excursion may offer better sound at lower levels with greater efficiency than a larger, longer-throw driver. Too many variable for me to expect that would be more than a general guesstimate, especially on my part.
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No worries, but Work and Life is colliding big-time lately so I just don't have time and energy to dig deep right now.
Fundamentally, do you not understand why the number is ~9N, or do not understand why the discrepancy between the SNR and the SFDR? The latter is easily shown with a picture, I think, but the former requires actually doing some ugly (to me) math. AFAIK there is not a simple closed-form solution for SFDR (though this is not something I've really dug into for years so maybe some bright young researcher discovered one; I just remember the results). The hand waving explanation for the latter is that you look at the difference between the quantization steps and a pure sine wave, generate an equation that describes the errors, solve it, and calculate the ratio between signal and error terms.
Bessel functions work well for these calculations and are pretty cool themselves, but are one of those things that are a step beyond what most working engineers (at least I) deal with daily, and those grad school courses from 30-odd years ago have not all stuck with me. Check them out: https://en.wikipedia.org/wiki/Bessel_function
This would be a good time for ol' what's-his-name to step up and 'splain it to us po' dumb engine-eers who don't "get" the underlying science.
OT: Price aside, somehow I have never been a big Neumann fan, though they produce some sweet vocals. Perhaps because I mostly recorded instrumental ensembles I always seemed to gravitate toward AKG C414 series mics. All I own now are much cheaper and I don't record much anymore (last gig was a few years ago recording a local youth orchestra and generating concert CDs). My most expensive mic now is actually my old Earthworks M30 measurement mic.
I understand the discrepancy between snr and sfdr. It isn't clear why the number is 9n. The hand waving explanation makes sense to me though it still didn't jump out why 9n rather than another number.
Unfortunately the only way I know to get to the real number is to do the math... Integrating Bessel functions without a closed-form solution; I don't think there's any easy way around it. You can read the paper I linked as a guide.
Not quite sure why you think your system should distort. If of a reasonable standard there should be no audible issues - yes, I know most systems start sounding sad when pushed, for reasons I've mentioned too many times
- but there is no inherent limitation which prevents them producing high impact, high intensity transients, for example.Don Hills
Addicted to Fun and Learning
Back in the 80s, at an audio show in the UK, Court Acoustics demonstrated their range of PA speakers by generating 140 dB SPL with a recording of a field howitzer being fired. And a demo by KEF of their flagship speakers, where a recorded drum kit was reproduced at "lifelike" levels, with a meter showing the peak levels required (over 800 watts).
The JBL LSR 308:
Test Condition:
Both speakers playing.
Log sweeps at 5dB intervals, then, "stack" the sweeps by adding (mathematically) 5,10,15,20,25dB (and so on) to the lower amplitude sweeps.
Result: At 98dB level (at listening position), the woofer starts to give out, as signified by the violet sweep that falls behind the stacked adjusted values of the other sweeps. Beginnings of a drop at the highest frequencies is also noted.
Test Condition:
Both speakers playing.
Log sweeps at 5dB intervals, then, "stack" the sweeps by adding (mathematically) 5,10,15,20,25dB (and so on) to the lower amplitude sweeps.
Result: At 98dB level (at listening position), the woofer starts to give out, as signified by the violet sweep that falls behind the stacked adjusted values of the other sweeps. Beginnings of a drop at the highest frequencies is also noted.
Sounds about right. I got the sales chappy with the Bryston and Dynaudio duo to push the volume of a drum workout to the point of intense transient impact, lifelike IOW; beyond volumes I've done - the amps were capable of 1000W into 8 ohms. and, probably more relevant, 0.007% distortion, 20Hz to 20KHz at 900 Watts into 4 ohms. This sounded as clean as the specs imply, showing that the speakers weren't a bottleneck.
I'd be suspicious of the power supply running out of puff with graphs like this - first thing I would do is check what the voltage rails were doing when the higher bass SPLs were being called - I suspect they would be a bit of a mess.
...say to myself "Here's a limit for these speakers" and incorporate that finding into my expectations.
Yup... Have you done distortion sweeps over power as well (apologies if you have and I missed them, busy day/week/etc.)
Looking at the distortion on these sweeps, nothing stands out particularly. As SPL rises from low levels distortion decreases (the SNR increases), then the bass distortion goes up with the higher increments of power. I take sweep distortion measurements with a grain of salt, though.
Single tone test got fugly...
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That math might be a step above me now days. Like you been quite awhile since I was in any schooling. I will read the paper and see what I can learn from it.
@Blumlein 88 -- no worries. If I ever get some spare time I can wade through it again, but it's going to be a while (back to working weekends plus we have some sick out-of-state parents so have had some unexpected trips lately). I had to work pretty hard at advanced math in college; the actual on-the-job math is usually just algebra with the occasional calculus equations to deal with. Years ago I was awestruck by a PhD friend who solved a fairly simple-looking yet gnarly differential equation; he laughed and said he used Maple.
@RayDunzl -- Thanks for that. Also, I want to say how much I appreciate all your data and the HUGE effort you've spent (and continue to expend) taking and presenting it. I do not say it nearly enough, if ever, but I really like having you around!
@RayDunzl -- Thanks for that. Also, I want to say how much I appreciate all your data and the HUGE effort you've spent (and continue to expend) taking and presenting it. I do not say it nearly enough, if ever, but I really like having you around!
A limit for the speakers? For, say 95dB at the listening position, what does that translate to as the level measured centred in front of a single speaker working only, 1 metre away?
Lets see:
Since 2 speakers are working, subtract about 6dB for one...
So, 95dB becomes 89dB at the listening position.
10 feet is 3 meters, add 6dB (actually probably less in-room) for 95dB at 1.5m, or 101dB at .75m
Eyeball that to 100dB at 1m, as an "Am I overloading this thing?" guestimate. Which should be answerable with "No, they are spec'd for 112dB".
I'll measure it later after TV time. this Trump/Travel Ban/District Court thing is interesting right now.
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