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[Christian Effendy]

That's cabin gain, boys. Well, and with very large amount of power and excursion too.
A single 'normal' 12" sub driver that's only have around 90dB SPL in free space, can have 20Hz SPL at 100dB in car with proper enclosure and placement.
When the room is very small and the pressure is very high, you can have an incredible SPL numbers.
Try this with an SPL meter:
Crank your pro 2x18 sub in free field, then do the same thing in your house. Notice the added SPL in bass region?
Want more? Play it in a small, concrete basement.

[Mike Butler (media)]

Christian Effendy wrote on Fri, 26 January 2007 08:27

That's cabin gain, boys. Well, and with very large amount of power and excursion too. A single 'normal' 12" sub driver that's only have around 90dB SPL in free space, can have 20Hz SPL at 100dB in car with proper enclosure and placement. When the room is very small and the pressure is very high, you can have an incredible SPL numbers. Try this with an SPL meter: Crank your pro 2x18 sub in free field, then do the same thing in your house. Notice the added SPL in bass region? Want more? Play it in a small, concrete basement.

..or how about your back seat.

[Mark Sadhra]

Mark "Bass Pig" Weiss wrote on Sat, 09 December 2006 00:12

What always gets me about the car sub folks is their de facto procedure of inflating SPL figures. 179dB from 4 18" drivers? C'mon, get real.

Their is nothing wrong with those numbers, but you have to understand that the vehicles they use are purposely built,reinforced with cement and re bar and the subs are fed 10s of  thousands of watts for a few seconds just long enough to get a reading.  

Take a look at the current world records 176.6db's with one sub.
http://www.termpro.com/asp/worldrecords2.asp
The meter used for measurements: http://www.termpro.com/storefront/index.asp?Page=1
also check out the forums on www.termpro.com for more info.    

[Mark "Bass Pig" Weiss]

There's a video reposted on YouTube, from Realm of Excursion, claiming to be shaking the windows on some storefront.

Here's the video link:
http://www.youtube.com/watch?v=9wAxPwh5bF0


However, it looks suspicious for the following reasons:

Look at the guy leaving the store. Now most of us have seen windows shake like that when the door slams. The timing of the window shake, just a couple seconds before the guy passes by is awfully suspect.

If it were really that possible to produce enough infrasound to shake the windows from 20' away like that, then the guy would be doubling over and vomiting on himself, or perhaps would avoid walking in that direction altogether. At the very least, he'd be putting his hands over his ears in a hurry as that soundblast occurs. He didn't react at all, which is suspicious. I think the audio was dubbed in later, or the whole video was shot at a time when they KNEW a customer would be leaving the store.

OTOH, if 4 RE 18" drivers COULD do that, then i reckon 4 Bassmaxx ZR18s would have broken all the store windows.

[Mark Sadhra]

Mark "Bass Pig" Weiss wrote on Mon, 29 January 2007 23:50

There's a video reposted on YouTube, from Realm of Excursion, OTOH, if 4 RE 18" drivers COULD do that, then i reckon 4 Bassmaxx ZR18s would have broken all the store windows.

I know automotive windshields break @ 160 plus db's.
http://www.youtube.com/watch?v=lxScxOaAuzY

check out some hair tricks.
http://www.youtube.com/watch?v=lxScxOaAuzY

[Mike {AB} Butler]

Mark,
Mark understands deep bass reproduction probably better than you and I put together (read down to posts below).
Now to my point:
Sure, there have been windows blown out of cars. Remember that the cubic air volume of a car is very small.. compared to that of a store. Unless they set up the speakers right at the store windows, the chances of that much movement diminish rapidly, as sound decreases in energy level over distance. You cannot get the same energy at 50' as you get at 4'.. without an exponential jump in accoustical output.
Point is, the two events compared here (interior of a car and the interior of a store) are NOT one and the same.
Regards,

[Mark Sadhra]

Mike {AB} Butler wrote on Tue, 30 January 2007 08:04

Mark, Mark understands deep bass reproduction probably better than you and I put together (read down to posts below). Now to my point: Sure, there have been windows blown out of cars. Remember that the cubic air volume of a car is very small.. compared to that of a store. Unless they set up the speakers right at the store windows, the chances of that much movement diminish rapidly, as sound decreases in energy level over distance. You cannot get the same energy at 50' as you get at 4'.. without an exponential jump in accoustical output. Point is, the two events compared here (interior of a car and the interior of a store) are NOT one and the same. Regards,

I understand but claiming that if the RE's can shake windows, Bassmaxx subs would shatter the windows is wrong.  SPL has way more to do with the install than equipment used. I bet it's around 90% install 10% equipment.  

[Mike {AB} Butler]

Mark Sadhra wrote on Tue, 30 January 2007 15:40

I understand but claiming that if the RE's can shake windows, Bassmaxx subs would shatter the windows is wrong.  SPL has way more to do with the install than equipment used. I bet it's around 90% install 10% equipment.

What does that have to do with your previous statement? Nothing, as far as I read:

(Quote:)
Mark "Bass Pig" Weiss wrote on Mon, 29 January 2007 23:50

There's a video reposted on YouTube, from Realm of Excursion,

OTOH, if 4 RE 18" drivers COULD do that, then i reckon 4 Bassmaxx ZR18s would have broken all the store windows.

Your response:
I know automotive windshields break @ 160 plus db's.
http://www.youtube.com/watch?v=lxScxOaAuzY

check out some hair tricks.
http://www.youtube.com/watch?v=lxScxOaAuzY
(end Quote)

What I understood from Mark Weiss's comments is that the whole concept originally put forth by the automotive poster in response to a PA thread is absurd. I would tend to agree. And your barging into this thread with what I consider to be [unrelated to the rest of the thread] "defense" of the automotive sound industry so far has produced little to do with real physics, science, or even practical application to the very real issues in live audio. The problems in achieving high SPL in a car are far fewer than trying to do so at 120' in a venue. Sure, SOME expert setup figures into the equation for any kind of setup.. but power is still power - a system is either innately big enough.. or it is not. THAT's all Mark Weiss is alluding to - in a very polite manner.
Please, take the automotive stuff out of this discussion, and return to the basics of drivers that produce the best performance for cost..
Thanks,

[Mark "Bass Pig" Weiss]

Gentlemen:

My intent was to question the accuracy of the video clip (I suspect that the author took advantage of the off-camera door slamming shut, which typically, with those aluminum-framed storefronts, causes all the glass to set off in a subsonic oscillation.

For something 20+' away from the building to achieve that, it would require massive output below 10Hz, so massive, in fact, that anyone walking in the viscinity of the sound source (that non-chalant man, for instance) would be instantly in pain, or at the very least, badly startled in the same way as if a car bomb had gone off just 10' from him. Since the man had clearly just exited the store, and appeared undisturbed by these sounds, I conclude that the cause of the window shake would likely NOT have been from the auto sound system.

Equipment is equipment, a system is a system. Auto systems are rediculously inefficient with tiny sealed boxes. A large, vented box with a Hemholtz resonator tuned to 10Hz might be believeable, but not sealed boxes with drivers that are clipping badly.

YouTube is full of smoke and mirrors tricks. When I'm bored on my coffee break, I frequently load YouTube and search "subwoofer" to see the latest laughs. I've seen every one of these videos. If these people only knew how silly most of them look.

[Mark Sadhra]

Mark "Bass Pig" Weiss wrote on Tue, 30 January 2007 20:48

Gentlemen: \ Auto systems are rediculously inefficient with tiny sealed boxes. A large, vented box with a Hemholtz resonator tuned to 10Hz might be believeable, but not sealed boxes with drivers that are clipping badly.

Why does it require massive output at 10hz? most SPL systems are tuned around 50hz.Spl systems don't use small sealed boxes they use very large ported boxes tuned high. Take a look at the link below. Thats a install log of a system similar to the one in the viseo. Same subs 4000 watts more power.
http://fresnoracing.ipbhost.com/index.php?showtopic=30159