According to this online piston excursion calculator, a 12in woofer (I chose around 510cm² or 10in diameter for radiating area) in a sealed enclosure would require 195mm of XMAX at 20hz to produce 117dB at 1m 😱
So yeah, they probably meant 120dB for frequencies above 100hz or thereabouts. That's often the case in speaker's specification sheets. And even that is probably optimistic for a single 12in woofer.
So yeah, they probably meant 120dB for frequencies above 100hz or thereabouts. That's often the case in speaker's specification sheets. And even that is probably optimistic for a single 12in woofer.
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Bingo.
Those specs say the speaker will put out 120dB at some frequency, and its frequency response is -3dB at 20Hz.
The PA world is just as bad for this, to a point where I wrote an article: Spec Wars: Looking Inside Loudspeaker SPL Specifications - ProSoundWeb
Chris
Those specs say the speaker will put out 120dB at some frequency, and its frequency response is -3dB at 20Hz.
The PA world is just as bad for this, to a point where I wrote an article: Spec Wars: Looking Inside Loudspeaker SPL Specifications - ProSoundWeb
Chris
I recall that the same spec mumbo jumbo was used by Velodyne in their literature back in the day (e.g. 1980s I think, when their first models became popular). This is nothing new.
So sorry, but your produce cannot defy physics...
So sorry, but your produce cannot defy physics...
I second that. Very good article Chris.
I find it surprising that professional buyers/users of these PA systems could be mislead by such copious amount of BS from the manufacturers. I would get it in the unprofessional/audiophile market. But the installation of large PA systems requires a level of expertise which would, supposedly, negates the possibility of said users believing these preposterous numbers.
I find it surprising that professional buyers/users of these PA systems could be mislead by such copious amount of BS from the manufacturers. I would get it in the unprofessional/audiophile market. But the installation of large PA systems requires a level of expertise which would, supposedly, negates the possibility of said users believing these preposterous numbers.
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Of course. But we are not really talking about the sub by itself anymore then, which is the goal of the specification sheet.
So is it a maximum or continuous output spec?
Choose!!!
I don't see anything wrong with the crossover specs. Variable lowpass from 40-140jz or an LFE bypass for use with a surround sound recieved.
Choose!!!
I don't see anything wrong with the crossover specs. Variable lowpass from 40-140jz or an LFE bypass for use with a surround sound recieved.
It is written on the spec sheet : Maximum Continuous SPL = 120dB SPL. They visibly don't mean peak.
Btw, I was thinking about KaffiMann's comment about corner loading the sub. Even with 18dB of gain, the driver would still require around 24mm of excursion (one way) at 20hz to produce 117dB SPL
As far as the crossover is concerned, nothing seems out of the ordinary indeed, contrary to the supposed maximum SPL.
This sub will put out a 120dB continuous sine tone.
All it needs is a frequency where it's 92dB@1w, and to run the amplifer up to clipping.
Given it's a 12" driver in a tiny sealed box, I'd suggest that it's either right at the top of the LF operating range (say, 120Hz) or it's some cone breakup mode out towards 1kHz.
120Hz at 120dB would require 10.6mm peak-to-peak cone travel, which is probably well within the limits.
I mentioned this in my article linked in a previous post, but it bears repeating: we don't know what frequency the maximum SPL is measured at.
Another example would be this: I have a 15" PA subwoofer. It's 97dB@1w at 100Hz, 94dB@1w at 40Hz, and there's a narrow peak at 1.2kHz where it hits 103dB@1w. The long-term thermal power handling is 1KW, and the short-term thermal power handling is 2KW.
We'll say that the recommended amplifier will produce 2KW into that cabinet.
What's my maximum SPL?
The loudest sound that box can make is 136dB. Will it do that at low frequencies? Not a chance. It'll still make an SPL meter read that number, though, so that's what gets put on the brochure.
Chris
All it needs is a frequency where it's 92dB@1w, and to run the amplifer up to clipping.
Given it's a 12" driver in a tiny sealed box, I'd suggest that it's either right at the top of the LF operating range (say, 120Hz) or it's some cone breakup mode out towards 1kHz.
120Hz at 120dB would require 10.6mm peak-to-peak cone travel, which is probably well within the limits.
I mentioned this in my article linked in a previous post, but it bears repeating: we don't know what frequency the maximum SPL is measured at.
Another example would be this: I have a 15" PA subwoofer. It's 97dB@1w at 100Hz, 94dB@1w at 40Hz, and there's a narrow peak at 1.2kHz where it hits 103dB@1w. The long-term thermal power handling is 1KW, and the short-term thermal power handling is 2KW.
We'll say that the recommended amplifier will produce 2KW into that cabinet.
What's my maximum SPL?
The loudest sound that box can make is 136dB. Will it do that at low frequencies? Not a chance. It'll still make an SPL meter read that number, though, so that's what gets put on the brochure.
Chris
@Chris661
I totally agree with all of that, as I agree with your article. I was specifically talking about 20hz since it was the OP point of concern 🙂
I totally agree with all of that, as I agree with your article. I was specifically talking about 20hz since it was the OP point of concern 🙂
Disclaimer: amateur here.
Whilst I too question their ability to chuck out 117 dB of continuous 20 Hz...
Their studio installs are something I'd rather love to hear, and more than that, I would rather like to get my hands on a 700wrms subwoofer plate amp that size.
I suspect when implemented in their higher level™ acclaimed™ professionally installed ™Phantom™Focus System™ (PFS™).™, you get at least 4 of them perfectly placed by some very clever people™.
Whilst I too question their ability to chuck out 117 dB of continuous 20 Hz...
Their studio installs are something I'd rather love to hear, and more than that, I would rather like to get my hands on a 700wrms subwoofer plate amp that size.
I suspect when implemented in their higher level™ acclaimed™ professionally installed ™Phantom™Focus System™ (PFS™).™, you get at least 4 of them perfectly placed by some very clever people™.
6000W plate amps are available:
SP1-6000-HT
DSP_PowerPack Modules | RAM Audio
Calculated excursion required for 3*18" drivers 117dB@20Hz is 20.1mm (Piston Excursion calculator)
might just be able to hit 117dB with 3x BMS 18N862:
http://www.bmsspeakers.com/fileadmin/bms-data/product_data_2012/bms_18n862_t_data_2012-02.pdf
A bit of a waste though considering the same drivers in ported boxes could do so much more.
SP1-6000-HT
DSP_PowerPack Modules | RAM Audio
Calculated excursion required for 3*18" drivers 117dB@20Hz is 20.1mm (Piston Excursion calculator)
might just be able to hit 117dB with 3x BMS 18N862:
http://www.bmsspeakers.com/fileadmin/bms-data/product_data_2012/bms_18n862_t_data_2012-02.pdf
A bit of a waste though considering the same drivers in ported boxes could do so much more.
It even worse as given max spl. is often calculated instead of measured; power compression (short and long term), port losses and more are not taken into account.
Maybe they mean the loudness of the hit to the ground when you throw it in a ravine..... just like most cars do over 200 mph. 🙄
Most woofers are excursion (xmax) limited not power limited.
The woofer in the example probably runs out of xmax at 1kw so 94dB/w at 1000W = 124dB - about 3dB power compression = 121dB practical maximum output when hard (not dynamic) voltage limited and EQ-ed.
I'd discount the RAM Audio unit for my (and many home use?) needs as it looks to have a fan... Unless it's a completely silent one, That'd be me out.
But the SP1-6000? Yep - fair's fair. Ya got me on that one, that right there is a motherfudging beast of a plate amp. (LPF/Crossover only down to 60hz? Come on... But yep, it'd still kick my backside back into my listening chair no problem)
Touché 🙂
It is written on the spec sheet : Maximum Continuous SPL = 120dB SPL. They visibly don't mean peak.
Btw, I was thinking about KaffiMann's comment about corner loading the sub. Even with 18dB of gain, the driver would still require around 24mm of excursion (one way) at 20hz to produce 117dB SPL
As far as the crossover is concerned, nothing seems out of the ordinary indeed, contrary to the supposed maximum SPL.
I never said it would make that much sound at 20hz, not going to happen.
Just that when the measurement conditions are not specified, could be done a lot of different ways.
I agree with that, no problem.
I used your remark about corner loading to show that, even within these optimal conditions, it is still very unlikely to reach 117dB at 20hz, which is the starting point of this thread.
It is obvious for a lot a us, but, sadly, the widespread gullibility of the audiophile world still never ceases to amaze
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Easiest person to fool is yourself. Don't have to be an audiophile to make a poor decision.
What I meant was: could be corner loaded at 120hz, and rounded up to nearest whole.
We don't know for sure.
What I meant was: could be corner loaded at 120hz, and rounded up to nearest whole.
We don't know for sure.
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