Quad 8" sealed sub... - Page 2 - AVS Forum
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post #31 of 44 Old 08-29-2012, 08:39 PM
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"Even quadrupling the payload weight isn't going to significantly alter the acceleration of the rocket."

??? 2226h and 2226h with 400 grams mms. what are you talking about bfm?


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post #32 of 44 Old 08-29-2012, 08:45 PM
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Holy crap. Adding a pound to a cone's mass is a lot! smile.gif

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post #33 of 44 Old 08-29-2012, 08:57 PM
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the point was that adding mass can reduce the damping of a driver and make it sound subjectively slow. that resonance is going to ring significantly in the time domain.

edit: this is incorrect, see below.

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post #34 of 44 Old 08-30-2012, 05:47 AM
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Quote:
Originally Posted by LTD02 View Post

what are you talking about bfm?
What the poster was talking about, the acceleration and deceleration of the cone vis a vis Mms.

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post #35 of 44 Old 08-30-2012, 11:51 AM
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Quote:
Originally Posted by LTD02 View Post

the point was that adding mass can reduce the damping of a driver and make it sound subjectively slow. that resonance is going to ring significantly in the time domain.

And this is exhibited where in your post? I see nothing to do with the time domain or damping at all just the dramatic loss of top end sensitivity and parameter shifting that comes with quadrupling the moving mass of a driver? I've run through a lot of sealed subs, some of them low Q while others were VERY high q and very peaky. You would expect to see ringing due to this and the peaky response shape and I did too, but it is just not there in the measurements in any amount large enough to be concerned with. Typical room acoustics in the bass range make them miniscule in comparison. Issues with resonances and ringing or bad damping seems to be dominated by total system design WITH the driver not from the driver damping itself.

+1 to Bill's post. Think about some of the pressures, electrical power and restorative forces acting on controlling the positioning of the driver cones and inside of the driver motor and encountered in small sealed enclosures or inside of a horn throat. Have you ever encountered a woofer with a VERY loose suspension and then connected it to an amplifier and noted the effort it now takes to move the cone? Adding a hundred grams to the cone will change the driver behavior most assuredly but what I don't buy is that it will cause audible smearing in the time domain because now it it has become delayed to start and stop and rings because the amplifier and motor cannot control the cone any longer. This should be very easy to measure if that is the case. Lower MMS is good for plenty of reasons but this isn't one that I buy into.
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post #36 of 44 Old 08-30-2012, 12:05 PM
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Quote:
Originally Posted by LTD02 View Post

the point was that adding mass can reduce the damping of a driver and make it sound subjectively slow. that resonance is going to ring significantly in the time domain.
But that behavior is entirely captured in the resultant q. Cone mass doesn't independently influence perception beyond its impact on q, or frequency response, as they are all directly related. You can't "hear" a heavy cone independent of other factors such as motor strength, enclosure alignment, eq, amp power, etc.

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post #37 of 44 Old 09-02-2012, 11:41 AM
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"But that behavior is entirely captured in the resultant q."

we are talking about the same thing. i say "reduced damping", you say "higher q". same concept.

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post #38 of 44 Old 09-02-2012, 11:54 AM
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"You would expect to see ringing due to this and the peaky response shape and I did too, but it is just not there in the measurements in any amount large enough to be concerned with."

you are right. i can't hear a difference in the impulse response. thanks for the clarification. that is actually pretty amazing (at least to me).

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post #39 of 44 Old 09-02-2012, 05:46 PM
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Vandersteen used (3) 8" drivers in its 2W subwoofer, i really liked that little sub, two of them in any system we had in the showroom really shined.... Not sure what point i'm trying to make... too many Cream Ale's with dinner....
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post #40 of 44 Old 03-20-2013, 10:10 AM - Thread Starter
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Wow, I didnt mean to cause such a ruckus. Now my brain hurts.

I finally dug up the T/S parameters on these subs.

Fs: 14.2 Hz
Qes: .29
Qms: 1.67
Qts: .25
Re: 3.37 ohms
Vas: 81.7 liters
Sd: 233 cm2
Xmax: 6.85 mm

sens: 91 dB

Anyone want to crunch some numbers for me? Sealed or ported?
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post #41 of 44 Old 03-20-2013, 12:42 PM
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KBlair, I wouldn't take all of the discussion as any "fault" of yours. Some members get very "enthusiastic" when it comes to certain things. In the end, I enjoy the discussion, so long as it stays (mostly) polite and I always learn something. It's why I come here.
Like NicksHitachi said in an earlier post, you've already got the drivers and a vision for what you want to do with them. Go ahead and build it and hopefully enjoy it. Hell, I put together a ported sonosub using a 15 year old Cerwin Vega driver that came out of a home speaker last fall! I had the supplies, I had the driver, why not? Now, I won't go posting about how this or that is was but it was something to do and I enjoyed building it. It works just fine in my garage. smile.gif
Have fun!
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post #42 of 44 Old 03-20-2013, 04:17 PM
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Quote:
Originally Posted by dtsdig View Post

KBlair, I wouldn't take all of the discussion as any "fault" of yours. Some members get very "enthusiastic" when it comes to certain things. In the end, I enjoy the discussion, so long as it stays (mostly) polite and I always learn something. It's why I come here.
Like NicksHitachi said in an earlier post, you've already got the drivers and a vision for what you want to do with them. Go ahead and build it and hopefully enjoy it. Hell, I put together a ported sonosub using a 15 year old Cerwin Vega driver that came out of a home speaker last fall! I had the supplies, I had the driver, why not? Now, I won't go posting about how this or that is was but it was something to do and I enjoyed building it. It works just fine in my garage. smile.gif
Have fun!

I agree. I may have been originally told I was all wet, but really I didn't and don't care. We see so many different speaker designs on the market and frankly, they do all work. Some better or worse than others but the design is the pride and joy of the designer and/or builder. I understood a concept of multiple small drivers as being better than single large drivers. It made sense to me, and I took on a belief system. Others may call it myth, and that is just fine. That is their belief system. I respect that. I think if you have the drivers, build away. Actually I would like to build one some day. I have made plans for a riser in my theater room with multiple 8 inch drivers. So far I have not built it only due to the raised eyebrows from my wife.

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103 inch AT screen with 9.x playback. IB sub woofer system. Two manifolds with 2 15s and 2 12s. Line array with 2 15s. Running main channels with Minimus 7s. Have front wide and front hight and rear surrounds. Room is perfect size for smaller speakers like the Minimus speakers. Approx. 17x13x8. Tower speakers were taking up to much room.
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post #43 of 44 Old 03-20-2013, 07:51 PM
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with only 50 watts, the driver goes a little over xmax (which is probably fine with that driver) in a 0.5 cubic foot sealed enclosure.

a second driver, another 50 watts and another 0.5 cubic feet would give +6db
a third driver, another 50 watts and another 0.5 cubic feet would give +4db on top of that (+10db total)



sensitivity is closer to 81db 1w1m than 91.

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post #44 of 44 Old 03-21-2013, 01:59 PM - Thread Starter
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Thanks, I was playing in WinISD with these yesterday and got similar figures. Going with individual chambers at .45ft^3 for some added rigidity and to allow flexible wiring. Will be powered by a 300w amp I already have.

Since these are down firing I will mount to the baffles internally and flare the openings.

I might even build 4 separate cabs instead of one quad cab.

Also my comptroller signed off on a budget of $500 to finish mounting and cabling the tvs and relocate the wifi router. Im going to squeeze a set of tritrix out of that smile.gif
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