Best enclosure type for high-diameter low-XMax Driver - diyAudio
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Old 14th June 2015, 08:15 AM   #1
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Default Best enclosure type for high-diameter low-XMax Driver

So I'm looking at one of these guys:

Amazon.com: PYLE-PRO PDW21250 - 21'' Performance Optimized High Power Subwoofer: Car Electronics

And at building my own enclosure for it. Planning on using as a subwoofer in the 35-80hz range. Sounds like it will handle 500-750W RMS pretty well. Looking to get a LOT of volume out of this thing, without too much of a hit to quality.

And YES, I know it's a low-quality driver. It will not be the same as spending $500-1000. And its RMS is probably exaggerated.

Anyways, it has a rated Xmax of 9mm, a high (almost certainly exaggerated) sensitivity of 107db, and it's 21" in diameter. I'm wondering what type of enclosure will work best for this driver, given its lower Xmax but higher diameter. Or if that would have no effect on what type of enclosure to use.

Two possible uses would be both outdoors in the open, and inside of a "smallish"(can hold around 100 people) garage/shed. which types would be ideal for each, and what would be a decent compromise? I'm definitely looking more for that mid-bass punch than low-bass rumble.

Currently I'm thinking of:
1)Standard sealed enclosure (probably something around 6'x4'x2', don't remember off the top of my head) would be alright indoors, placed in a corner.
2)Ported Enclosure, probably something tuned around 30hz, looking around 5-10 cubic feet. Better for outdoors, still good inside, loss of some quality and gain of some air noise.
3)Folded Horn, (probably a rear chamber for the back end of the driver) long enough for (1/4, if I remember correctly) of a 30hz wave to get the full benefit of the horn. Faced into a corner indoors should get more volume at lower frequencies, and should still be good when faced at a small crowd outdoors. Cons of being more directional, and some issues with harmonics and distortion at some points?
4)Rear-Loaded Horn, Similar to the folded horn, no chamber over the front of the driver (duh), similar to what is being called a "scoop" but probably with a longer length for the sound to travel. Don't know much about this vs a standard folded horn.
5)Tapped Horn Heard some interesting things about these. Possible issues with distortion, phase and harmonics? Thoughts/suggestions on this one?

Any other suggestion just let me know. Also correct any errors in my thoughts


In recap:
Indoor suggestions
Outdoor suggestions
Compromise suggestions
Any info I missed/mad mistakes with about any of the above enclosures.


Thanks guys!
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Old 14th June 2015, 11:41 AM   #2
sreten is offline sreten  United Kingdom
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file:///C:/Users/cex/Downloads/PDW21250.pdf

Hi,

According to the above any use above 200Hz doesn't look promising.
It looks more like a sub than a mid bass punch driver.

Classic sealed is 7 cuft. Classic vented 13cuft tuned to 28Hz.
5 cuft sealed and 10cuft vented tuned to 30Hz are workable.

rgds, sreten.
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Old 14th June 2015, 04:23 PM   #3
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Default My Bad

My bad. I had my ranges off. As I said before, this guy only needs to go up to roughly 80hz, as I've for the rest of the frequency range covered. I guess instead of mid-bass I'm looking fore more, kinda, punchy-ish bass drum kicks, beats, etc. So yes, XO'd under 80hz.
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Old 14th June 2015, 08:51 PM   #4
freddi is offline freddi  United States
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some of that kick is probably coming higher than 80 - fwiw you could try it in a Karlson - maybe as small as 12 cubic foot external bulk - scale K15 about 1.2 look at Gauss's K18 http://img72.imageshack.us/img72/825/gaussbracing.jpg

I don't know if that Pyle is midbass material
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Old 14th June 2015, 09:58 PM   #5
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Default sorry, I guess not midbass

I was mistakenly under the impression that "mid bass" was in the 40-80hz range. Ill have speakers with this setup that can comfortably get down to 80hz with plenty of volume, its the sub-80 that needs the volume here. Sorry for the mix-up.
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Old 14th June 2015, 10:46 PM   #6
freddi is offline freddi  United States
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what are the real parameters? - - here's a link where one measured with qts ~0.64 Pyle 21" driver: Surely this cannot be.


I have Madison X21 and IIRC their qts ~1 - you can see that a Pyle pym1298 (~Eminence Kappa12a) was about 10dB louder at 100 than the 21" on a narrow wingless baffle
Click the image to open in full size.

Last edited by freddi; 14th June 2015 at 10:52 PM.
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Old 14th June 2015, 11:57 PM   #7
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What are these "real parameters" that you want me to find? Please excuse my ignorance here.
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Old 15th June 2015, 05:08 AM   #8
djk is offline djk
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"What are these "real parameters" that you want me to find? Please excuse my ignorance here."

Ones that aren't BS (like the 107dB).
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Old 15th June 2015, 12:45 PM   #9
wg_ski is offline wg_ski  United States
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Quote:
Originally Posted by ProbablyABadIdea View Post
What are these "real parameters" ...
The real values of VAS, fs, and Qts. Yeah, they lie about these too - all the time. If you have those three, and reasonable estimates for Sd and Re, you can derive SPL 1M/1W. As well as determine how big the box needs to be.

Usually, the only thing "wrong" with these drivers is a relatively weak motor. You can get bass out of it if you make the box big enough - and it will be "a lot" comapred to what you're probably used to getting out of home stereo speakers. It will likely stuggle to hit 125dB at 40 Hz running full tilt, and that may take 15 cubic feet to do it. Professionals are used to getting 10dB more out of less space. That's what they get out fo their more expensive toys.
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Old 15th June 2015, 03:11 PM   #10
tb46 is offline tb46  United States
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Hi ProbablyABadIdea,

The T/S parameters for this driver have been all over the place over the years. From the same thread that freddi linked in Post #6: Pyle 21" driver: Surely this cannot be. - djk recommends a BP4 in Post #103, and that general box type looks like a good solution. BP1Fanatic took another stab at it in Post #108. I'll attach one more Hornresp simulation, to be used w/ a 35Hz 2nd order HP. But, you'll have to measure the T/S parameters:

Measuring Loudspeaker Driver Parameters

The Subwoofer DIY Page - Measurements

Regards,
Attached Files
File Type: txt 21250bp4.txt (993 Bytes, 2 views)
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