A Thread for those interested in PPSL enclosures

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Forgive me if this question has been answered before. I have tried to read the entire thread but may have missed it. How high in frequency can you run a PPSL? Is it only useful as a subwoofer, or can it be used as a woofer below a midrange? Also, does the size of the baffle opening matter? Does it need to be "tuned" for different woofers?
 
Forgive me if this question has been answered before. I have tried to read the entire thread but may have missed it.
1)How high in frequency can you run a PPSL?
2)Is it only useful as a subwoofer, or can it be used as a woofer below a midrange?
3)Also, does the size of the baffle opening matter?
4)Does it need to be "tuned" for different woofers?
1)Depending on the size of the plenum (slot) 300 Hz would be near the upper limit for 15" drivers.
2) Depends on the drivers, and what you consider "midrange".
3) Yes. A few examples of simulated frequency response can be seen in posts #779 and #796 using 18" and 15" drivers. In all cases, there will be an increase in upper bass caused by the plenum, followed by a drop in response, a deep cancellation that won't respond well to EQ, limiting the upper response.
4)Optimum Fb (box tuning) is driver dependent, optimum plenum size is generally as small as possible for the drivers chosen. The upper "horn gain" of the plenum must be weighed against the reduction of cabinet volume it uses, which reduces the LF output.

The example below is an actual outdoor measurement of a 2x15" PPSL, the upper response peaks between 160-200Hz, followed by a 23dB dip at 400 Hz, and rough response above.

Art
 

Attachments

  • 2x15" PPSL "Shoehorn".png
    2x15" PPSL "Shoehorn".png
    95.9 KB · Views: 661
Last edited:
  • Like
Reactions: 1 user
Frequency range

Time to bring this topic back to life. I just built a prototype of the PPSL. Initial results are positive, but I am only getting a very limited frequency response. I need to get in the neighborhood of 350-400hz in order to use this with a set of Oris horns. I selected the Dayton 380-4 15" drivers. Box is tuned to 25hz. 8.7cu. ft. ported box.



Any help would be appreciated.
 

Attachments

  • PPSL Original.jpg
    PPSL Original.jpg
    96.4 KB · Views: 496
Time to bring this topic back to life. I just built a prototype of the PPSL. Initial results are positive, but I am only getting a very limited frequency response. I need to get in the neighborhood of 350-400hz in order to use this with a set of Oris horns. I selected the Dayton 380-4 15" drivers. Box is tuned to 25hz. 8.7cu. ft. ported box.



Any help would be appreciated.

Hi Rudy, very nice looking response curve !

How far apart are your drivers, or rather what size is the plenum?
In post #196, djk says spacing needs to be within 1/4WL of second harmonic of highest desired freq
 
Member
Joined 2008
Paid Member
Time to bring this topic back to life. I just built a prototype of the PPSL. Initial results are positive, but I am only getting a very limited frequency response. I need to get in the neighborhood of 350-400hz in order to use this with a set of Oris horns. I selected the Dayton 380-4 15" drivers. Box is tuned to 25hz. 8.7cu. ft. ported box.



Any help would be appreciated.

380-4 ? I built a ppsl using the Dayton PA-380's (8 of them), but to be quite honest, i did not check the upper end response, because I am out of them at 60Hz. My slot width is 6 inches.
 

Attachments

  • right side new bass up close.jpg
    right side new bass up close.jpg
    247.8 KB · Views: 474
The Dayton DCS 380-4 sees like it might work based just on the first few sweeps I ran.



The plenum is currently 8" wide, which just allows for the driver installation through the slot.



Currently, I have the plenum depth at 18.75" and I think I will reduce any excess space on the plenum depth tomorrow. I'll run a new sweep and see what effect it has on the response.



If I could just get usable response near 350hz I'd be very happy.
 
I have two 2x15" ppsl subwoofers but cannot see any other advantages, in practice, than smaller size of front baffle compared to standard 2x15" installations. Not the best sounding 2x15 sub either and some driver flapping occurs at high power levels, caused by uneven cone load (requires stiff cones).
One of these can be seen here:
YouTube
 
Member
Joined 2008
Paid Member
The Dayton DCS 380-4 sees like it might work based just on the first few sweeps I ran.
The plenum is currently 8" wide, which just allows for the driver installation through the slot.
Currently, I have the plenum depth at 18.75" and I think I will reduce any excess space on the plenum depth tomorrow. I'll run a new sweep and see what effect it has on the response.
If I could just get usable response near 350hz I'd be very happy.

Hi Rudy,
Please see the ppsl that I built for mid-bass use. It is +/- 2db from 70Hz up to 500Hz. Above 500Hz, it really falls off the cliff and is down 10db @ 570Hz. The plenum width is 5 inches; the height is 18. This yields 90 sq inches of exit, for 156 inches of cone area (2x12's). If you look carefully, you will see that the plenum slopes at an angle towards the back. The physicality if it is such that the depth of said plenum is 22 inches, but where the angled walls meet, the height is only 5 inches. This is the solution that I reached for myself, after screwing up two previous attempts.
For your DCS-380's, in order to get the plenum as small as possible, you might have to assemble the plenum FIRST, and then install into the box, leaving the front panels to be installed last. You want to the 2 drivers to nestle as close as possible, leaving only enough clearance for the cone excursion so that it does not bump the magnet of the opposite coupled driver.
An alternative to the triangular fashion that I did mine, would be to simply block the corners with 45 degree slat boards. In one of my previous builds, I filled in the void created by the 45, with sand and glue.
There was some discussion as to the compression ratio of the slot vs. the SD of the cones. For mid-bass, mine is 90 divided by 156= 0.576, or inversely, it would be 1.733 ......Looking thru the past posts by djk, I seem to recall the target as 2:1 for subwoofer/woofer applications. Hope this helps !

p.s. don't forget to allow for the T/s changes that will occur in your situation due to 1) *assuming* your 2x4ohms drivers are wired in series, 2) the additional mass load of the coupled drivers should cause the Fs to drop, and the Qts to rise.
 
Minimized slot size as much as I could while still being able to load drivers through the slot. Clearly it does make upper frequency improvements. Will need to keep working on this.
 

Attachments

  • Minimized Slot.jpg
    Minimized Slot.jpg
    75.9 KB · Views: 580
  • Slot size compare.jpg
    Slot size compare.jpg
    87.6 KB · Views: 582
  • PPSL_WT3.jpg
    PPSL_WT3.jpg
    321.9 KB · Views: 512
Time to bring this topic back to life. I just built a prototype of the PPSL. Initial results are positive, but I am only getting a very limited frequency response. I need to get in the neighborhood of 350-400hz in order to use this with a set of Oris horns. I selected the Dayton 380-4 15" drivers. Box is tuned to 25hz. 8.7cu. ft. ported box.



Any help would be appreciated.

Hey, Rudy. Could you tell me how heavy each cabinet ended up being?
(And what drivers you used?

Thanks.
 
Minimized slot size as much as I could while still being able to load drivers through the slot. Clearly it does make upper frequency improvements. Will need to keep working on this.

I think that the PPSL is a subwoofer design. It definitely wasn't designed to handle midrange duty. That you're getting up to 200 Hz from it is actually excellent. Trying to cross it over higher is likely to be as successful as trying to cross another subwoofer system over that high. It might end up sounding pretty bad anyway.
 
Perhaps I need to re-evaluate my selection then. Ideally 20hz to 350hz or so would do the trick. Subwoofers, I don't need. I'm trying to get rid of two RSW-15 subs that handle 20hz-100hz duty. I also have 4 big Marty 18" subs for my LFE channel.


I do know that Les Hudson, djk, and Scott L were able get a bit higher than the 200hz. Several folks use the PPSL as the low end to a large front loaded horn, like an Oris.
 
Prototype Summary

Summary:
In case anyone stumbles on this thread in the future....
I continued my experiments by creating a wooden ring that I could slide under one driver so as to get the drivers as close as possible and leaving enough room for Xmax displacement. Sweeps on that configuration yielded absolutely no improvement in the upper frequency range. I also tried various slot opening sizes. Clearly, this PPSL design is not usable much above 200hz with the Dayton DCS380-4. The driver is advertised as 20hz-500hz.

Since I had so much success with my Full Size Marty builds, I though I would convert my test box into a single driver, vented, box. Roughly 10 cu. ft. with the vent I had made should give me a 20hz tuning and plenty of range betwen 20hz and 400hz. The glue wasn't even dry when I ran the attached sweep and this leads me to try a more conventional approach for this project. I'm calling this box a Mid Marty since it approximates the volume of the Mid sized Marty.

I will let the glue dry today and will hook it up to my system to listen to actual music using the new prototype from 20hz-350hz or so. I realize this is a very inexpensive driver and may not fill the 'quality' standard, but it will give me an idea of what can be done. I am considering using the Dayton RSS390HF-4, which more than twice the price, but should be a more capable driver for this purpose.
 

Attachments

  • Mid Marty DCS380-4 v PPSL.jpg
    Mid Marty DCS380-4 v PPSL.jpg
    101.4 KB · Views: 461
  • Mid_Marty_DCS380_4.png
    Mid_Marty_DCS380_4.png
    256.1 KB · Views: 445
Member
Joined 2008
Paid Member
Whats the best/easiest way to model a PPSL? i have two RSS390HF i want to try this :)

That driver has an EBP of 48, so it would like to see a sealed enclosure. You can model it the same way as a conventional system, but you might experience some shift in the driver's parameters, once mounted in the plenum, due to the added load. 10-12% decrease in Fs, and a corresponding rise in Qts.

With your two 15's, it will be a very large box, even with a sealed enclosure, as you have to account for the plenum volume in the overall design. You can easily ended up with a volume approaching/or/exceeding 12 cubic feet.

Even though I use mine in a mid-bass application, I strongly recommend this design (ppsl) for bass duty, aka sub-woofer duty, only. i.e. 100hz, or lower.

Having stated all the above, you will never experience the THWACK of a drum kit, as you will with a ppsl, on any other bass system, short of huge horns.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.