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.
You might try stuffing the back corners with some Dow Corning 703, a resin-coated fiberglass product. It can be carved to fit with an electric knife, or an ordinary steak knife as well.

The secret to the upper frequency bandwidth is reducing the plenum volume, and the front-to-back dimensions as much as practical. I've never tried to use them above 250hz or so, although Les Hudson has made variants that he was able to use up to 400hz.

Are you using the Q=2 HP filter at Fb? That makes it flatter on the low end. Without the filter they tend to sound clean but a bit lean.

Driver Properties
Name: 2226H
Type: Standard one-way driver
Company: JBL Professional Division
No. of Drivers = 2
Mounting = Standard, Push-pull
Wiring = Parallel
Fs = 40 Hz
Qms = 5
Vas = 175.6 liters
Cms = 0.158 mm/N
Mms = 98 g
Rms = 5.029 kg/s
Xmax = 7.62 mm
Xmech = 20 mm
P-Dia = 335.3 mm
Sd = 883.9 sq.cm
P-Vd = 0.689 liters
Qes = 0.33
Re = 5 ohms
Le = 1.75 mH
Z = 8 ohms
BL = 19.2 Tm
Pe = 600 watts
Qts = 0.31
no = 3.3 %
1-W SPL = 97 dB
2.83-V SPL = 99.37 dB
-----------------------------------------
Box Properties
Name:
Type: Vented Box w/ Active HP Filter
Shape: Prism, square (optimum)
Vb = 6 cu.ft
Fb = 37 Hz
QL = 6.197
F3 = 36.59 Hz
Fill = minimal
No. of Vents = 2
Vent shape = rectangle
Vent ends = one flush
Hv = 10.88 in
Wv = 2.5 in
Lv = 13.71 in
-----------------------------------------
Active 12 dB/oct. HP Filter
Fx = 37 Hz
Qx = 2

BBv6.0 shows a 1.1dB rise around 180hz and a smooth roll-off to a shelf of -0.94dB below 80hz. On the upper end it shows a smooth roll-off above 180hz to 320hz, and a 6dB/oct roll-off beyond from the voice-coil inductance.

I have not been able to model what I measure in a real cabinet on the upper end due to the very irregular space created by the plenum and the back of one driver and the front of the other.
 
Interesting- hornrep seems to show a pretty accurate simulation of what I've actually got vs. bbox pro-I wonder why. I presume you mean fill in the corners of the plenum. I made a half hearted attempt at that too, but just took some wood and cut off about 75% of the two back corners, didn't seem to do much but it's worth trying again and doing it right. Thanks for taking the time to sim this.
 
DJK, I am using the filter, but did not have it on when I measured for the photo. Initially I thought I was getting a better result just using a bandpass eq vs. the hp, but can test some more. I find my DEQ/Behringer mike to be inconsistent when measuring the very low end. I need to learn to use REW to get a proper view of the output and to eq.
The idea of going to the 500hz horn crossover was just a temp measure anyway till I make space for the midbass front loaded horns (Erik Forker) that I made last year. That horn has a very smooth response from 105hz to 500hz and should sound better handiing those frequencies. So the intent is to end up limiting the PPSL to 40-105hz. I use a HSU original 10" sub for the last two octaves.
For some reason, I never seem to get the same reponse plots in bbpro that you do, mine showed a pretty flat run out to almost 500hz, so I must be doing something wrong in modeling.
Build used home depot 3/4" plywood, stained and water based poly finish with several sandings after each of maybe 4 coats of poly. I routered most of the edges curved, and will eventually turn the boxes vertical to leave space for the FLH's. It looks good enuf unless you examine too closely, and matches the hardwood floor in the room as does the FLH.
I would probably be better off with a sub that can go from 25hz to 100hz vs using both the HSU and the PPSL for the same purpose, but I had the drivers on hand so figured I'd see how it sounded. I also felt that most sub drivers are too slow to mate well with horns, so thought this might be a better solution. I could try to corner load them and apply some eq, I might not need the HSU's at all. Again, Dennis, thanks for your patience and sharing of knowledge.
 
AkAbak PPSL

Hi OscarS,

I exported the Hornresp simulation from Post #320 using: File - Export - AkAbak Script... , and that seems to work just fine. You can then modify the script to suit your design.

I'll attach the AkAbak script file, I had to change the file extension to upload it, to use change it back to "aks".

Regards,
 

Attachments

  • 2226ppsl.txt
    2.9 KB · Views: 117
Hi OscarS,

I exported the Hornresp simulation from Post #320 using: File - Export - AkAbak Script... , and that seems to work just fine. You can then modify the script to suit your design.

I'll attach the AkAbak script file, I had to change the file extension to upload it, to use change it back to "aks".

Regards,

Thanks for the file. Question: So the plenum chamber is modeled as a straight waveguide then, huh? Why is S1=1 cm² in the script, but it is 880 cm² in the HR input screen?
 
Hi OscarS,

Post #327: "So the plenum chamber is modeled as a straight waveguide then, huh?"

Yes. By definition in the OD horn the center of the drivers is located at S2, the throat at S1, you cannot change that; but, you can change S2 to the actual area after you subtract the area loss due to the drivers, and you can add S4 and S5 if you want to e.g.: taper the the plenum (chamber/duct/horn/waveguide) from reduced S2 to area without driver influence to mouth. So there is some room for improvement of the model.

Post #327: "Why is S1=1 cm² in the script, but it is 880 cm² in the HR input screen?"

Because some dummy fiddled with the value prior to exporting the simulation. For starters I'd go with the larger value. :)

Hope the example gets you started anyway.

Regards,
 
Last edited:
Member
Joined 2008
Paid Member
Angled (or tappered)

I'm also wondering, like LineSource, if an angled slot does have any major effects...?

Also, what is the optimum size for the slot (if there is any such thing)?

-tg

Opening is 1:2 of woofer's SD. These were made strictly for mid-bass. The dynamic impact is incredible! In the first picture you can see how the plenum is angled back. If I ever do another build, it will be that of a classic, shared volume, 6th order for SUB-woofer use only. I've come to the conclusion the ppsl is best utilized in the low bass only. The system in the picture uses them to 250 Hz, but my ears tell me 180 Hz and lower for best sonic quality. OR, it may just be inherint limitations of the drivers I used: Eminence 4012HO.
 

Attachments

  • total camera download 227.jpg
    total camera download 227.jpg
    102.7 KB · Views: 799
  • total camera download 254.jpg
    total camera download 254.jpg
    114.5 KB · Views: 801
Hi There

If I want to make a ppsl for this speakers, how to begin designing them and with what software this is possible.

visatons 10 inch polypropulene


Technical Data:
Rated power 110 Watt
Maximum power 140 Watt
Nominal impedance Z 8 Ohm
Frequency response fc - 7000 Hz
Mean sound pressure level 91 dB (1 W/1 m)
Excursion limit 22 mm
Resonance frequency fs 19 Hz
Magnetic induction 1 Tesla
Magnetic flux 1250 µ Weber
Height of front pole-plate 8 mm
Voice coil diameter 5 cm
Height of winding 1,45 cm
Cutout diameter 23,3 cm
Net weight 2,5 kg
D.C. resistance Rdc 5,7 Ohm
Mechanical Q factor Qms 3,19
Electrical Q factor Qes 0,38
Total Q factor Qts 0,34
Equivalent volume Vas 230 l
Effective piston area Sd 330 cm2
Dynamically moved mass Mms 42 g
Force factor Bxl 8,7 T · m
Inductance of the voice coil L 1,2 mH


thanks
 
Hi there

Thanks, I now hornresp and have done tapped horns with it, I have to play with it again.

I have now the visatons in a acoustic resistance box where she doe very well there job, but as every audio freak we want to test everything ;-).

Designing amps is mare my thing but she need speakers and this is a little a start for me, ready made are very expensive sometimes, and with diy I can save a lot of mony.

The visatons did also very well in a H frame, I had very deep bas, I did really like it but it has to be located in the middle of the room for best bass, and bass was there only when present in music, that is like it has to be, so clean, normal boxes have sometime bas what is not in the music, (booming), that is what I don,t want. But we discuss here the PPSL.

Oke, PS plenum? (slot) my english is not that good, is this the space between the two speakers, opening, maybe a picture will help, I see these have efficienty like horns? because you are use horn for mid and high.

I go read google for more about it, it looks also like a OB dipole woofer woho has not so high efficienty.

Dipole Woofer

And here discussing about to use hornresp.

http://www.diyaudio.com/forums/subwoofers/119854-hornresp-147.html

thanks again
 
Last edited:
Hi there
Oke, PS plenum? (slot) my english is not that good, is this the space between the two speakers, opening, maybe a picture will help, I see these have efficienty like horns? because you are use horn for mid and high.
A plenum, or slot, is the space between the two speakers.
The plenum does not increase efficiency like a large horn would, but does subjectively increase "punch" and "tightness", and allows for a smaller frontal area than if the speakers were front loaded, and is easier to build than a stepped baffle for push pull as is used with speakers requiring a higher crossover point.
 

Attachments

  • Plenum.png
    Plenum.png
    77.8 KB · Views: 754
Member
Joined 2008
Paid Member
ppsl mid-bass prototypes

Scott: have you tried them with a plenum which is as small physically as possible and no taper as shown in your first picture? Are your sections of sono tube sealed or are they vented? Thanks. Best regards Moray James.

Hi Moray,

The plenum is indeed as small as physically possible. The magnet actually sits slightly inside the cone of the adjacent woofer. The taper goes from front to back, not side to side. It was also built to mimic the beginning of a horn throat. The horns I built for these were prototypes, too small, and not a sturdy enough construction, which is why I removed them. The sono-tubes are sealed, and of differing volumes to compensate for the fact one woofer is inverted. An interesting observation I discovered along the way is, while a single drivers' Fs is 46, when they are loaded in the slot, the fs dropped to 40 Hz. One can throw Thiel/Small calcs out the window in this type of build: the system Fc lies at 57 and the apparent low frequency limit is 36 Hz. Just imagine what a ppsl sub-woofer application can do !
 

Attachments

  • hybrid ppsl prototypes 003.jpg
    hybrid ppsl prototypes 003.jpg
    136.6 KB · Views: 721
A plenum, or slot, is the space between the two speakers.
The plenum does not increase efficiency like a large horn would, but does subjectively increase "punch" and "tightness", and allows for a smaller frontal area than if the speakers were front loaded, and is easier to build than a stepped baffle for push pull as is used with speakers requiring a higher crossover point.

Ahh I was right I see, oke now it get more clear, I have to play with the hornresp software, nice that this is a dipole source box, it sounds good and has high efficientie? SPL.

I try to find soms documantation on google.

Thanks for sharing with me.

kees
 
Design for your speakers as you would any bass reflex cabinet, reduce the volume taken up by the plenum (slot) from the cabinet volume when calculating box size.

Has I design the reflex cabinet with two speakers doubling vas and Sd because I see here two speakers also.

By the way, little offtopic but do someone now what tweeter this is? it sounds better then the magnat metal domes.


thanks
 

Attachments

  • DSCN0294.JPG
    DSCN0294.JPG
    818.1 KB · Views: 668
Last edited:
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.