A Thread for those interested in PPSL enclosures

[Zero D]

Originally Posted by tinitus

I thought a PPSL was never meant to be isobaric...but that the slot load 'simulates' it ?

Yeah, silly me, reading etc too quickly But the simulate info is new to me, so Thanks for that

Originally Posted by tb46

That's the slot for the two drivers,

I got that much, which is why i sketched in approx where the 2 drivers go

Regards

 

[grecon]

This dual 18" cabinet is my attempt to combine an older idea from DJK in another thread, to his PPSL design in post #115 of this thread. Perhaps I'm not moving forward properly doing this. Anyway, this is what DJK had to say about the W18N8-1000.

"With two FAITAL PRO W18N8-1000 in a 6th order vented alignment you can have a 40hz F3, 104dB/2.83V/1M, in only 4.5 cu ft (net).

Driver Properties
Name: FAITAL PRO W18N8-1000
Type: Standard one-way driver
No. of Drivers = 2
Mounting = Standard
Wiring = Parallel
Fs = 35 Hz
Qms = 10.6
Vas = 211.8 liters
Cms = 0.116 mm/N
Mms = 178.9 g
Rms = 3.712 kg/s
Xmax = 9.5 mm
Xmech = 14.25 mm
P-Dia = 380.3 mm
Sd = 1136 sq.cm
P-Vd = 1.079 liters
Qes = 0.28
Re = 5.4 ohms
Le = 1.8 mH
Z = 8 ohms
BL = 27.55 Tm
Pe = 1000 watts
Qts = 0.273
no = 3.127 %
1-W SPL = 97.1 dB
2.83-V SPL = 98.81 dB
-----------------------------------------
Box Properties
Name:
Type: Vented Box w/ Active HP Filter
Shape: Prism, square
Vb = 4.5 cu.ft
Fb = 40 Hz
QL = 6.716
F3 = 40.65 Hz
Fill = minimal
No. of Vents = 0
Vent shape =
Vent ends =
-----------------------------------------
Active 12 dB/oct. HP Filter
Fx = 40 Hz
Qx = 2

The vent would have to be quite large for full power use, 107 sq in by 30 inches long, perhaps bent like this:

bentport.gif Photo by dkleitsch | Photobucket



With 2KW/4Ω one box should do 134dB at 50hz or so, without exceeding x-max. 3.3Ω minimum at 40hz, 4Ω at 50hz or above.




Edited by _djk_ - 10 July 2011 at 4:51pm
djk

 

[grecon]

Well the best I can get so far is to make it larger to 27"x32"x22.5" with two ports 4.25"x10.875"x20" and power with 1000w for a port velocity of 19.5m/s.

The new panel sizes are
A 27X32
B 22.5 X 30.5
C 22.5 X 27
D 22.5 X 21
E 22.5 X 7.5
F 22.5 X 9
G 22.5 X 20

http://i1312.photobucket.com/albums/t531/grecon144/FAITALPROW18N8-1000_zps36ad7fb0.png?t=1368154161

Please let me know if you see anything that won't work.

 

[tb46]

Hi grecon,

The 22.5" outside dimension should be about 24" as you are using 22.5" for the inside board heights.

Here it is in Hornresp (just as a simple BR) w/o the HP filter:

Regards,

 

[grecon]

http://i1312.photobucket.com/albums/t531/grecon144/FAITALPRODUAL18PNG_zpsbd485839.png?t=1368222711


Yes, thanks tb46 the outside dimensions should read 27" x 32" x 24". I'm wondering if I should slide the whole plenum away from the port and perhaps widen the plenum to allow the speakers rear vents to be less constricted.

 

[tb46]

Hi grecon,

I would not widen the plenum, on the contrary, I would reduce the opening.

This box will need quite a bit of additional bracing if you want to take advantage of the maximum power capability of these drivers. Added bracing means (obviously) lost volume. A slightly smaller port would not do any harm, and the port length could be reduced depending on the HP filter used.

Also, I for one would be way to clumsy to mount these great drivers securely through the front entry of the plenum.

I'll attach a quick sketch that addresses some of these concerns, others might not find this helpful, so YMMV.

Regards,

 

[grecon]

Hi tb46,

thanks for the great ideas. I'll look at your changes and see what I can learn from them.

thanks, Greg

 

[djk]

There is little point in making the plenum like that in the rear corners (unless you are trying to go above 250hz or so).

The removable panels for driver loading weaken the cabinet, I made my first pair that way.

 

[kees52]

A time ago I did make this for the visaton wsp 26S woofers of 10 inch.

I have never test it but wil do this in future to see how this sounds,
it was for the home, not PA.

I have a friend who does metal music in a band, can you tell me what is best
as bass box PPSL, or Tapped horn or normal horn. I hear good things about the PPSL. He did ask me if I want to build a Bass, I think a sub bas is not needed in a metal band, dut a kicker type of box, from 35 hz and higher.

DRawns are for the visatons two in one PPSL box High pass material wood 1.8 cm thick.

thanks.

kees

 

[chrapladm]

Whatever happened to the quad 8 PPSL design DJK?

Was hoping to see pics or more talk of that one. Still want to try a dual 8" sealed or 10" PPSL cabinet someday. Want to see what all the fuss is about.

 

[DrDyna]

I came across Nelson Pass' "slot loaded open baffle" project a few days ago and have been studying it with great interest. I'm wondering how much it differs from this type of enclosure, aside from the obvious open back.

http://www.firstwatt.com/pdf/art_slob.pdf

Using the design on firstwatt, I'm wondering if simply boxing off (sealed) the slot loaded arrangement he's using, as well as inverting half the drivers accomplishes the same type of thing. Any woofer that's designed to keep up with AMTs gets a golden star in my book.

 

[tinitus]

I guess a line array is different ... ?

with multiple woofers you might need a very big box, if thats what you suggest ... ?

 

[ßart West-VL.]

DrDyna,
Thanks for that link.
Nice reading!

 

[DrDyna]

I guess a line array is different ... ?

with multiple woofers you might need a very big box, if thats what you suggest ... ?

The reason I found it interesting was more the commentary and observations that they make that apply directly to the design element of "firing woofers into a slot chamber".

If that design was arrived at as something that would mate with the sonic characteristics of the big Heil AMT driver, I'm extremely interested. I came across this and one other PPSL thread and thought to myself.. "huh..this really isn't that much different.."

If I were to build the "AMT3" prototype, what I'd have is an open-backed SL (a "slob" as it's referred to by Pass)...reversing 3 of the woofers on one side would make an open backed "PPSL"...and then finally if the box were to be built closed, or vented, would be pretty much exactly the same as the PPSL drawings I've seen in this thread, just with 3x as many drivers.

So, I am understandably curious, I might have to build one of these things to see how it sounds. I can imagine with the right woofers, this could be downright awesome, if it's really indeed "a woofer version of the Heil AMT".

 

[GM]

If I were to build the "AMT3" prototype, what I'd have is an open-backed SL (a "slob" as it's referred to by Pass)...reversing 3 of the woofers on one side would make an open backed "PPSL"...and then finally if the box were to be built closed, or vented, would be pretty much exactly the same as the PPSL drawings I've seen in this thread, just with 3x as many drivers.

Correct, this was discussed way back when on one of the IB forums WRT manifold area/depth Vs driver width/net swept piston area [Vd], but they concluded it would add too much distortion to an IB's 'accurate' reproduction, so the R_O_T for them is to make the chamber big enough to keep compression negligible and not make it any deeper than necessary to mount the driver.

GM

 

[DrDyna]

...they concluded it would add too much distortion to an IB's 'accurate' reproduction..

Hm, interesting. I'll have to see if I can find that thread at some point to find out exactly what they mean by that.

 

[GM]

Good luck with finding the thread, I tried, but it was many years ago now and not even sure which forum it was on. I thought it was the 'Cult of the Infinitely Baffled', but it showed no posts for me even though I know I posted on it occasionally.

Regardless, they meant the same as I did when I was much more recently explaining on another forum why I preferred dual drivers on a large flat baffle to the really large truncated horns they had originally been in. Had I experienced this first, I would have understood and maybe agreed with the IB 'naysayers' up to a point depending on the XO point/slope and where the IB's throat was in room, i.e. the horn's upper BW sounded just that little bit 'pinched' that over time got on my nerves, yet didn't quite realize it until it wasn't there anymore.

For prosound apps it's moot of course, but in a high eff. app in a typical size room, pretty much any anomaly is highlighted, so for me any PPSL would have to have an XO point below its filter chamber BW same as with a tapped TL/TQWT/horn.

GM

 

[DrDyna]

so for me any PPSL would have to have an XO point below its filter chamber BW same as with a tapped TL/TQWT/horn.

GM

Do you think there's any merit to the idea of doing multiple sections with progressively smaller chambers that could be crossed over each time before the chamber resonances become a factor?

 

[GM]

???

GM

 

[tb46]

Hi GM,

I think DrDyna is talking about something like this (plus the Heil radiator on top):

Regards,