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Discussion Starter #21
What about, instead of using a port, I put this in there? That could probably cut down on the size of the enclosure and boost the low end some. Suggestions? Remember, I'm still a newbie at this.
 

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What about, instead of using a port, I put this in there? That could probably cut down on the size of the enclosure and boost the low end some. Suggestions? Remember, I'm still a newbie at this.
That 12" Dayton PR has an xmax of 10mm. I've always heard you want the volume the PR moves to be 150% - 200% what the driver moves so you'd need at least two. After that, it basically acts like a ported enclosure which means if you were hitting overexcursion in a 8 cubic foot ported box, you will also hit overexcursion in an 8 cubic foot PR box.

But, yes, with a smaller box this should work and be interesting.

EDIT - BTW, please note that PR's can not be downward firing.
 

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Discussion Starter #23
So If I got two of those, get the enclosure size down to day, 5 c.u. ft, How well should/would it perform do you reckon?
 

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So If I got two of those, get the enclosure size down to day, 4 c.u. ft, How well should/would it perform do you reckon?
Off the cuff I'd say once tuned it would sound okay. I will plug the numbers into Unibox when I get home to verify. One thing you will want to verify is whether it is best for you to have a $25 active driver with $45 in pasive radiators or just find a $70ish driver you like.

For example, for $86 you can get a Dayton 15" Quatro which would work well with a 300 watt BASH amp and a ported 6 cubic foot enclosure.

Please note that while PR's will allow you to construct a smaller box because you aren't dealing with the volume of the ports, they do not dig any deeper then ported designs. Actually, all things being equal they are usually 1 Hz or so less deep digging.
 

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Discussion Starter #26
Well I already have the $25 driver, so I guess I'll have to work with what I have. And I always like to try new things and experiment. So, PR's do that job.

18*18*45 box, with the two PR's on the sides of the ED sub.



** Wait, you said 'tune' the PR's? How does that work?
 

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Well I already have the $25 driver, so I guess I'll have to work with what I have. And I always like to try new things and experiment. So, PR's do that job.

18*18*45 box, with the two PR's on the sides of the ED sub.



** Wait, you said 'tune' the PR's? How does that work?
Instead of using a column of air as a "spring", a PR uses a column of air's equivalent mass. Each PR will have a bolt that you can remove and add washers until it is the proper weight. It is actually very easy. For tuning you just install the PR's backwards so you can easily get to the washer bolts. When you get them set right, just flip the PR's around and re-install.

PR's are neat and I'm always tempted to use them. Every time I do I end up doing cost calculations and wussing out and just using a design with a larger port.
 

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Discussion Starter #28
Ooh. I'd definatey need some help with that. >_> Also, would I have to buy more washers?
 

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Discussion Starter #30 (Edited)
Thanks, that link helped a lot.

* Hmm, I was doing it wrong, and when I plugged in the right numbers, I get something crazy like 23 lb's on each PR. What am I doing wrong?
 

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See my edit, I keep on getting some insanely large numbers.
I don't know. To be honest, I always just use Unibox and let the computer crunch the numbers. Without seeing your work the only thing I can suggest is that you double check that all your units match up (esp. for the density of air).
 

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Discussion Starter #34 (Edited)
Well, I did it for just one PR (instead of two) and came up with 1307 grams, which is like 2.88 lbs. That has to be way too much, I mean, they sample driver they used was like 280 grams, which is less than a pound.

Can it support ~ 3 lbs on the bolt? < Dumb question. I know it can, but it still seems like a lot.
 

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Well, I did it for just one PR (instead of two) and came up with 1307 grams, which is like 2.88 lbs. That has to be way too much, I mean, they sample driver they used was like 280 grams, which is less than a pound.

Can it support ~ 3 lbs on the bolt?
Well, according to the spec sheet the stock mass is 200 grams and the maximum moving mass is 500 grams (total, I assume). So, if the tune you are trying for requires 1307 grams then you may need three PR's, buy a 15" Dayton DVC PR or a TC-Sounds PR or change the tune of the sub.

But first let me double check my math - I'll get back to you in a few hours (since I have to wait to go home first).

BTW, what tune were you using?
 

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Discussion Starter #36
22Hz. >_> I really want it, but I may just stick iwth a port if I'm going to have to get multiple PR's.
 

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Okay, here is a first stab at this. First off, I made the input power 200 watts as that is the most RMS power the driver's voice coil can take (don't max out your amp). I used 170 liters (6 cubic feet) as the size of the enclosure. Here is a plot of the EHQS-12 driver with two of the cheaper Dayton 12" PR's. One has no additional mass (which results in a 30 Hz F3), the other has 300 grams extra weight on each PR (the most it can take). That one is tuned too low and results in an F3 of 43 Hz.

As a note (not included), the low mass one barely exceeds driver excursion on the active driver at 25 Hz, but the PR exceeds it at 30 Hz. The high mass one had all kinds of excursion problems starting at 50 Hz.
 

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Here is what I mean. Some of these excursion problems go away by using a smaller box and/or adding a third PR. I haven't yet gotten the driver to not overexcurse below 25Hz no matter what I do (for PR or ported).

I'd almost be tempted to experiment with a sealed box with an aperiodic vent.
 

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