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Old 22nd February 2013, 10:45 PM   #81
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Dave I still have you beat by a driver...

You have the better room and mains though.
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Old 24th February 2013, 06:54 AM   #82
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Quote:
Originally Posted by weltersys View Post
Dave,

By max excursion, did you mean Xmax, or Xmech ?
Where was the mic placed in relation to the speakers, and at what distance?

Art
Crap, when you ask those kind of questions , I have no idea what you are talking about. I was talking about Xmax, measured distrotion was still very low. In the other thread I mentioned this, but I am placing the mike at the MLP.

Quote:
Originally Posted by SpeakerFrank View Post
Dave.let me add another question to the one before from Art. What kind of drivers you do talk about and how much do you use of that 18" drivers? Maybe also the kind of installationis also interesting!
RE audio XXX 18" drivers. I have them in an infinite baffle setup.

Quote:
Originally Posted by Josh Ricci View Post
Dave I still have you beat by a driver...

You have the better room and mains though.
LOL, did you just dare me? Maybe I should add those 4 LMS ultra 18" to the equation?
Crap, I think I caught your disease.
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Old 27th February 2013, 08:00 PM   #83
wingman is offline wingman  Denmark
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Quote:
Originally Posted by JapanDave View Post



LOL, did you just dare me? Maybe I should add those 4 LMS ultra 18" to the equation?
Crap, I think I caught your disease.
Pics please, or video @ 5hz
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bass is music
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Old 27th February 2013, 08:17 PM   #84
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vacuphile,
A typical horn is only 1/4 wavelength but even that is huge and impractical inside anything smaller than a stadium. I myself have never seen an 18" speaker that was rated at 5hz or even close to that. So what is going on here, are they in a closed box with augmented low frequency electrical eq to force them this low?

JapanDave,
The Xmax is the normal maximum excursion rating of a speaker at 10% distortion, and Xmech would be the ultimate mechanical limitation of the device before self destruction, such as having the voicecoil completely leaving the gap or physically being limited by the surround or spider before things start to tear or reach their physical limit such as a surround that only can stretch so far. Another problem with many 18" speakers is the voicecoil will hit the back plate and then they are toast. Without adding mass to the cone or electrically extending the low frequency output I don't see how you are doing what you say you are?
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Old 27th February 2013, 09:03 PM   #85
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Kindhornman,

I was stating it in circumpherence, you might be talking about diameter, so in that case we are in full agreement when it comes to a square mouthed horn.
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Old 27th February 2013, 10:35 PM   #86
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Something like this is simple actually. In a normal domestic sized space frequencies below 20hz are huge relative to the boundaries and get heavily reinforced same as in a car cabin or a closet just less strongly. You use a sealed system or IB arrangement due to the shallow 12dB octave roll off and predictable excursion profile vs frequency. Then you select electronics which do not have dc blocking filters until as low as possible (3-8Hz is not uncommon). From there it is a matter of LT or shelf boosting the low end shape to where you want it and scaling the system (power/driver displacement capability)to a size capable of producing the output levels required. The electronics roll off determines the bottom limit at that point.

Once you have 25-50L of driver displacement and the power to use it, you can accomplish quite a bit and with over 100L of potential displacement (>3.5 cubic feet) headroom becomes a complete non issue.

Dave and I have somewhat similar HT bass systems using the same drivers and similar power but his is IB and mine is a sealed alignment, so I can assure you this type of thing is possible. Home theater guys have been doing this for years.

Last edited by Josh Ricci; 27th February 2013 at 10:40 PM.
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Old 27th February 2013, 11:42 PM   #87
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Josh,
I follow you here you are in effect using the room loading to extend the bottom end. But you must be limiting the excursion at the same time, and what are you doing to tune out the fs of the device. I remember the papers from years ago on using electronics to use a speaker below its free air resonance in a seal box. but that was long ago and wasn't very well accepted at the time.
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Old 28th February 2013, 01:37 AM   #88
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The resonance of a system is largely irrelevant here. The system will still respond to inputs of frequencies below that point just not as strongly. Electronic manipulation of the signal input is used to reach the desired final response shape and behavior (extending the response very deep in frequency to the point that the electronics themselves roll off due to DC blocking filters). In this case shelf or Linkwitz transform boosting of frequencies on the low end in combination with the gain from the acoustic space the system is in are used to accomplish this. To be clear this does not modify the amount of maximum headroom available from the system which is set by the subwoofer alignment, amplifier power and room acoustics. This is why multiple long stroke large diameter drivers and loads of power are typically used.

You would not try this with any system other than sealed or IB as excursion gets wildly out of control, distortion skyrockets and output drops off a cliff below the corner in any resonant assisted alignment plus they get HUGE attempting to push the corner down below 15-20Hz range. Also this would be pointless and or dangerous to your equipments health to attempt to run a setup like this with just a couple of 12" drivers for example which would typically be maybe 3 to 5 liters of displacement.

Last edited by Josh Ricci; 28th February 2013 at 01:45 AM.
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Old 28th February 2013, 02:14 AM   #89
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Josh,
I follow you here. we are really doing what was done long ago. Long excursion designs with massive amounts of power to drive the devices with electronic shelving below the resonant frequency of the drivers in a sealed box. I follow that completely. At one time this was a patented process and so it wasn't adopted by the industry as it was not allowed. A diy device is not going to fall into the category of an infringing consumer manufacturer. I read about this in an early AES paper many years ago and I think it was included in the speaker compendium going back to Webster and up to what was current when the volume was put out.
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Old 28th February 2013, 03:55 AM   #90
BHTX is offline BHTX  United States
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I haven't read this entire thread, and won't bother to, but here's the easiest way I've found to accomplish experiencing this:

Some vehicles resonate wildly with one of the windows down while cruising the highway. A friend's Dodge Nitro is one of the worst I've noted. It's shaped like a rectangular box, I'm sure there are plenty of other vehicles that will do similar. I'm usually in the backseat and let down the window while it's going down the highway, and the 5-10 Hz resonance will cause substantial ear pain in a matter of seconds. Anyone else in the car abruptly demands and begs for me to stop and let the window up.. I just enjoy it for a moment, usually while watching the headliner flap to the frequency, and then give in and proceed to let the window back up when the pain becomes too irritating. Enjoy.
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