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The ultimate enclosure for the box 18-500 8a
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Old Croc
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    Posted: 09 November 2015 at 8:07pm
Greetings!

There are several plans for the box 18-500 8a driver https://images.static-thomann.de/pics/atg/atgdata/document/manual/193265_bda_185008a_uk_screen.pdf

Some plans can be found here http://www.lautsprecherforum.eu/viewtopic.php?t=4561

At the moment I have 2 of these http://www.jobst-audio.de/archiv/97-jb-sub118

Since Im quite broke at the moment but I might be interested to maybe build something it would be cool to get "the ultimate" design for the drivers I have.

I like the sound of the reflex and the fact that I dont need a separate kick bin with them.

Would this cheap driver work well in bandpass or PPSL or a scoop maybe?

Would be interesting to get some thoughts and ideas since I already have the drivers...

Thanks!
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Old Croc
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Points: 4007 		Post Options Post Options   Thanks (0) Thanks(0)   Quote bass*en*mass Quote  Post ReplyReply Direct Link To This Post Posted: 09 November 2015 at 9:52pm
they do work in supers, to a certain extent obviously but not bad considering the price..
get in touch with miles on here to get more detailed info ;)
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PPSL is pretty much "just" a reflex box so they should work just as well as in normal reflex.
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"PPSL is pretty much "just" a reflex box so they should work just as well as in normal reflex."
 
Basically true, except for the distortion reduction action, and the plenum adds a tiny bit of boost (around 3dB or so) from 100hz or so up into the 'kick' region (160hz~180hz with 15's).
djk
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Joined: 26 December 2013
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Points: 2435 		Post Options Post Options   Thanks (0) Thanks(0)   Quote app Quote  Post ReplyReply Direct Link To This Post Posted: 10 November 2015 at 1:54am
Any good links on how to sim a ppsl enclosure in winisd?

The ppsl seems interesting at the moment. I need to read some more about ppsl...


Edited by app - 10 November 2015 at 1:55am
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You model it just like double 18" reflex box. If you want to estimate the effect of slot in upper bass range, you need to model it in Hornresp. Personally I wouldn't worry too much about it, tho this would be nice little project to learn Hornresp on if you haven't touched it yet...

_djk_ have you ever experiented with any other loadings with push & pull pair of drivers?


edit: of course while simulating normally you'd substract displacement of drivers from the enclosure. With push & pull pair the reversed driver will pretty much compensate normally mounted driver, so one thing less to think about. 18" driver with cone, magnet and basket will displace 10-11 litres.


Edited by pfly - 10 November 2015 at 2:32am
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"_djk_ have you ever experiented with any other loadings with push & pull pair of drivers?"
 
I've done some 4th order designs, but 6th order is the best.
 
A 2 cu ft 2nd order sealed box with an F3 of 30hz can only be 0.18% efficient (84.55dB).
A 2 cu ft 4th order vented box with an F3 of 30hz can only be 0.36% efficient (87.56dB).
A 2 cu ft 6th order vented box with an F3 of 30hz can only be 0.90% efficient (91.54dB). 
 
 
A 40hz 2' cube 4th order dual 12 PPSL, one 4x8 sheet, 100dB. Ports above and below the woofer plenum. The drivers are about half the price of an 18 with similar output.
 
djk
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Originally posted by app app wrote:


The ppsl seems interesting at the moment. I need to read some more about ppsl...


I've been doing that as well recently Tongue

I've done some simulating with different drivers of all kinds of sizes and price points......


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So is the biggest benefits of ppsl getting low and high and have little distortion?

Am I right that ppsl arent that efficient,or is it totally depending on the enclosure type?
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Ive also been checking this http://hornplans.free.fr/mtl-46.pdf
Its quite efficient but dont go that low in singles/pair.
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Joined: 26 December 2013
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Originally posted by bob4 bob4 wrote:

Originally posted by app app wrote:


The ppsl seems interesting at the moment. I need to read some more about ppsl...


I've been doing that as well recently Tongue

I've done some simulating with different drivers of all kinds of sizes and price points......




I wouldnt mind if you simmed a ppsl for the box 18-500 8a LOL
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Points: 1924 		Post Options Post Options   Thanks (0) Thanks(0)   Quote bob4 Quote  Post ReplyReply Direct Link To This Post Posted: 10 November 2015 at 2:05pm

Originally posted by app app wrote:


I wouldnt mind if you simmed a ppsl for the box 18-500 8a LOL

I actually have already Smile

I'm quite busy now and don't have the time to discuss details, but I would like to do so soon.

My simulations suggest you should be able to cram two 18-500s in a PPSL box only slightly larger than your current JB118, and get a similar response. Of course you will get + 6dB since it will take twice the power, and hopefully have the little kick boost from the slot loading in the plenum. It will of course need a little EQ, but you could get the -3dB point at 34 Hz, and 125 SPL within xmax with 400 W input.

I'd be interested to get into hornresp too...... Evil Smile




Edited by bob4 - 10 November 2015 at 2:06pm
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