A Thread for those interested in PPSL enclosures - Page 48 - diyAudio
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Old 25th February 2013, 06:17 PM   #471
kees52 is offline kees52  Netherlands
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Old 28th February 2013, 07:38 AM   #472
Juhazi is offline Juhazi  Finland
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About impulse response of a slot arrangement in Hornresponse

I have mede simulations of my subwoofer project A bench style cabinet subwoofer 2x15 closed in Hornresp and now I think that I have learned to set parameters right. I checked the Impulse response simulation and was shocked!

The plenum seems to generete "ringing" a lot. I show a graph of 800cm2 opening area/40cm deep slot simulation and standard closed box.
- Can we hear this? is it relevant at 20-100Hz (plenum resonance 180Hz)
- What is the effect of two elements in slot push-pull arrangement
- Does the profile of the slot make difference

The attached simulations use RSS390HF but the driver has no effect to this
Attached Images
File Type: png ppsl470 RSS390HF system.png (49.4 KB, 413 views)
File Type: png ppsl470 RSS390HF impulse.png (64.7 KB, 395 views)
File Type: png pp470 RSS390HF system.png (49.5 KB, 387 views)
File Type: png pp470 RSS390HF impulse.png (54.0 KB, 383 views)
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Old 28th February 2013, 08:10 AM   #473
djk is offline djk
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Pray tell, how do you get Hornresp to model the highly irregular space between the front of the one cone and the magnet of the other?

Measurements on the 1988 prototype showed a strong cavity resonance when the drivers faced each other, and that it went away when the drivers were mounted push-pull. There was an out-of-band organ-pipe resonance up around 800hz or so IIRC.
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Old 7th May 2013, 11:29 PM   #474
grecon is offline grecon  United States
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Default FAITAL PRO W18N8-1000

I'd like to give these dual 18's a try using DJK's PPSL design. Its my first time designing a box using WINISD and I'm having trouble with the small box and long port.
I'm trying for 4.5 cu ft with 40hz tuning but I don't know how small I can make the box and still allow the speakers to "breathe".
At 4.5 cu ft I used two ports 5.50" x 10.875" x 38.2" to keep the port velocity down to 17m/s with full power.

This box is too big and I'm not sure where I can scale it down. The inside end of the port is getting too close to the speaker baffles with this arrangement.
The drawing is not to scale but the panel sizes are what I've got so far.
I tried to bend the port around the back. And move the speakers to the opposite side from the port opening.
Any help would be appreciated.


Click the image to open in full size.
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Old 8th May 2013, 06:19 AM   #475
Zero D is offline Zero D  United Kingdom
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Hi, with a 4.5 cu ft box @ 40Hz it "appears" to me that you've only selected 1 driver in the Options, and/or havn't selected Iso-Barik ? When i tried it, this is what i get
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Old 8th May 2013, 03:26 PM   #476
tb46 is offline tb46  United States
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Hi Zero D,

The basic PPSL as shown in Post #474 is not isobaric. It's a bass-reflex w/ two drivers.

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Old 8th May 2013, 04:06 PM   #477
djk is offline djk
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Really small reflex cabinets with high x-max drivers have problems with the ports. I've seen some 21" drivers that sim well in 4 cu ft, but the porting looks like a problem.

Passive radiators are the usual fix for hi-fi speakers, but present problems for PA. The total volume they need to displace can be on the order of 2x~3x what the main woofer is capable of doing, and its cone will be so heavy it will need to be clamped during transport.

I am looking at a dual Beyma 12LX60 design that will require an 18" PR with an x-max on the order of 20mm~25mm (one way) to work properly. The net volume of the box only need be 2.5 cu ft, and it looks like it would be flat to 40hz.

I will probably end up putting them in a PP tapped horn instead. Although it will be much larger, it should go to 30hz with no EQ (102dB/2.83V/1M).
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Old 8th May 2013, 06:16 PM   #478
Zero D is offline Zero D  United Kingdom
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Quote:
Originally Posted by tb46

The basic PPSL as shown in Post #474 is not isobaric. It's a bass-reflex w/ two drivers.
Hi

Well, shiver me timbers As he's posted in a PPSL thread i presumed it was one ! It sure looks like it's meant to be. Otherwise what's the Open area leading up to F for ?

Plus he said this,

Quote:
I'd like to give these dual 18's a try using DJK's PPSL design
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Old 8th May 2013, 07:16 PM   #479
tinitus is offline tinitus  Europe
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I thought a PPSL was never meant to be isobaric...but that the slot load 'simulates' it ?
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Old 8th May 2013, 07:51 PM   #480
tb46 is offline tb46  United States
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Hi Zero D,

Post #478: "...what's the Open area leading up to F for?"

That's the slot for the two drivers, maybe my sketch from Post #5 will help? :-) Or, djk's picture in Post #10?

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