A Thread for those interested in PPSL enclosures

[djk]

A note about a high Q filter.

I just built four 35hz PPSL for PA. The 6th order Q=2 filter needed was done inside a DBX 234 crossover. The DBX comes with a 40hz filter with two 0.15µF caps with a 19.6K (R5, R15) and a 39.2K (R6, R16) resistor. Changing these to 7.5K and 121K respectively gives 35hz with a Q=2.

I could have done the same thing with the 50hz filter in the DBX 231 EQ, or the bass amp with its 30hz/50hz filter.

Another way to do it with a DSP crossover is to set the filter to 35hz, and then use 9dB of boost with a Q=2 35hz EQ. The filter is -3dB at 35hz, so the result is 6dB or total boost (not the 9dB you dialed in).

 

[weltersys]

A note about a high Q filter.

I just built four 35hz PPSL for PA. The 6th order Q=2 filter needed was done inside a DBX 234 crossover. The DBX comes with a 40hz filter with two 0.15µF caps with a 19.6K (R5, R15) and a 39.2K (R6, R16) resistor. Changing these to 7.5K and 121K respectively gives 35hz with a Q=2.

I could have done the same thing with the 50hz filter in the DBX 231 EQ, or the bass amp with its 30hz/50hz filter.

Another way to do it with a DSP crossover is to set the filter to 35hz, and then use 9dB of boost with a Q=2 35hz EQ. The filter is -3dB at 35hz, so the result is 6dB or total boost (not the 9dB you dialed in).

A while back I checked out the response of my DBX 223 crossover with the 40 Hz HP engaged.

The curve looks like what a 24 dB per octave slope should until about 10 Hz.

Though it would provide adequate protection for most musical sources, the rising response below 10 Hz could be a problem with dropped needles and some sound effects etc.

Did you happen to check the response of your DBX 234 before and after modification?

 

[djk]

The below 10hz problem is the bypass switch circuit for the filter, if you remove R24, 21 it behaves as it should.

 

[weltersys]

The below 10hz problem is the bypass switch circuit for the filter, if you remove R24, 21 it behaves as it should.

Interesting, why would DBX put in R24, 21 when it makes the below 10hz problem ?

 

[djk]

I don't know, it makes no sense to me. I can send you the schematic if you need it.

 

[pk]

Which woofer for hifi?

djk: May I ask which woofer you would prefer for a pair of PPSL bass bins:

1. Eminence Kappa LF-2, or

2. The Martin Sound Pro, order #1844 (see link) that I know you have used before?

The application is for hifi (not PA).

Thanks a lot!

Best regards
Peter

 

[djk]

For hi-fi?

Probably the #1844 tuned to around 27hz.

 

[pk]

For hi-fi?

Probably the #1844 tuned to around 27hz.

Hi djk,

Thanks a lot!

Best regards
Peter

 

[scameron78]

djk, the whole cabinet rotated 90 degrees as shown in your second pic vs. your first pic. I just need something that is taller than it is wide and rotating your entire cabinet design 90 degrees accomplishes this.

Not sure how the plans would change other than adding the brace in the port.

Thanks,
Jim

EAW has a cabinet similar to the ones in the second picture.

EAW: FR250z

18 sound has a design like this also
Eighteen Sound Kits

how do these designs differ in sound compared to having the drivers mounted in a slot?

also 18 sound shows a dual 18 bandpass
Eighteen Sound Kits.

on a good note, i have some money saved for new drivers. just don't know whether to build a 4 taped horn cabinets or 2 PPSL cabinets.

 

[jea]

I’m ready to make some more sawdust!
Thanks to Les Hudson comments about “this is the best sounding subwoofer that I’ve ever heard” I will be making a ppsl subwoofer. And thanks to DJK, I will be making it per the cut sheet on post 115. The only difference is I want the port on the bottom as per the pic on post 10. Don’t know if the Eminence Kappa Pro-15lf-2 15” is the “best” or not but it should be good enough for my future surround sound. Being a newby, I am not sure what a Q=2 filter at 35hz is or what people say tuned to around 27hz means.

I have about five sheets of 5*5 baltic birch that I was going to use for a Klipsch clone but the ppsl looks far simpler to build and may even sound better.
So if anyone has any tips, comments feel free. And DJK, if you have the time I would appreciate it if you could upload a cut sheet so my sub will look like Les’s sub wuth the port on the bottom. If not I am certain I will muddle thru the build.

Regards,

jea

 

[CRESCENDO]

Another way to do it with a DSP crossover is to set the filter to 35hz, and then use 9dB of boost with a Q=2 35hz EQ. The filter is -3dB at 35hz, so the result is 6dB or total boost (not the 9dB you dialed in).

I was just about to ask if a DSP would act the same by doing the above. Glad to hear it. "The filter is -3dB at 35hz" - I'm assuming you're referring to the Linkwitz-Riley type of filer.

And since we're boosting at the high-pass cut-off, we don't need 3x the power (6dB of EQ), right? We're just making up for the filter..? If so, I'm buying birch next week!

Do you use fill in your sub boxes? Is it at all difficult to mount/remove drivers from the plenum?

I'm trying to think of smart enclosure and plenum dimensions to box this PPSL enclosure with the two 3015LF drivers I still have in the box. Do any mistakes jump out at you? Any help = much appreciation!

 

[remountier]

Sorry for my English....Try this script in Akabak...you need change driver TS-parametres
Def_Const |Hornresp Input Parameter Values
{
|Length, area and volume values converted to metres, square metres and cubic metres:
Vrc = 181.26e-3; |Rear chamber volume (litres)
Lrc = 58.00e-2; |Rear chamber average length (cm)
Ap = 480.00e-4; |Rear chamber port cross-sectional area (sq cm)
Lpt = 35.00e-2; |Rear chamber port tube length (cm)
MSd = 1111.50e-4; |Manifold Slot (sq cm)
ML = 44.20e-2; |Manifold Slot length (cm)
|Parameter Conversions:
Sd = 1600.00e-4; |Total diaphragm area for 2 parallel drivers (sq m)
dD = 2 * Sqrt(Ap / Pi); |Port tube diameter (m)
Lpt1 = Lpt + 0.306 * dD; |Port tube length plus unflanged inlet end correction (m)
Arc = Vrc / Lrc;
}
|===================================================================================
|Network node numbers for PPSL:
| 0-Voltage-1
| |
| +Driver+
| | |
|Radiator(1)-3-Port-4-Chamber-5 6-Slot-7-Radiator(2)
| | |
| +Driver+
|==================================================================================

Def_Driver 'Driver1'
Sd=800.00cm2 Bl=22.80Tm Cms=1.37E-04m/N Rms=2.20Ns/m
fs=37.9996Hz |Mmd = 115.03g Le=2.20mH
Re=6.10ohm ExpoLe=1

Def_Driver 'Driver2'
Sd=800.00cm2 Bl=22.80Tm Cms=1.37E-04m/N Rms=2.20Ns/m
fs=37.9996Hz |Mmd = 115.03g Le=2.20mH
Re=6.10ohm ExpoLe=1
System 'System'

Filter fo=45Hz vo=0 {b4=1; a4=1; a3=2.828427; a2=4; a1=2.828427; a0=1; }
Filter fo=130Hz vo=0 {b0=1; a4=1; a3=2.828427; a2=4; a1=2.828427; a0=1; }

Driver Def='Driver1' Node=0=1=5=6
Driver Def='Driver2' Node=0=1=5=6

Radiator 'Port outlet' Node=3 SD={Ap} Label=1
Duct 'Port' Node=3=4 SD={Ap} Len={Lpt} Visc=0
Duct 'Rear chamber' Node=4=5 SD={Arc} Len={Lrc} Visc=0
Duct 'Slot' Node=6=7 SD={MSd} Len={ML} Visc=0
Radiator 'Diaphragm' Node=7 SD={MSd} Label=2

 

[djk]

"Do any mistakes jump out at you?"

You didn't scroll up on the desiggn parameters, the filter details got cut off. I'll check your design when I get home, and get back with you tomorrow.

 

[djk]

"Try this script in Akabak"

I'll try that when I get home tonight. I will mention that I find no way to model the plenum with the very irregular driver shapes in it, thus the graphs produced are not accurate at the higher frequencies. GIGO.

 

[remountier]

Hi DJK! I really like your PPSL, here's a script ... he can be more accurately....

Def_Driver 'd1'|Mag-1580 x-max = 8.5mm
Sd=800.00cm2 Bl=22.80Tm Cms=1.37E-04m/N Rms=2.20Ns/m
fs=38Hz |Mmd = 115.03g Le=2.20mH
Re=6.10ohm ExpoLe=1
System 'PPSL'
Filter fo=45Hz vo=0 {b4=1; a4=1; a3=2.828427; a2=4; a1=2.828427; a0=1; }
Filter fo=160Hz vo=0 {b0=1; a4=1; a3=2.828427; a2=4; a1=2.828427; a0=1; }
Driver 'Drv1' Def='D1' Node=1=0=2=3
Driver 'Drv2' Def='D1' Node=1=0=2=3
Duct 'Du1' Node=22=2 WD=16cm HD=42cm Len=21cm
Duct 'Du2' Node=2=4 WD=16cm HD=42cm Len=21cm
Duct 'Du3' Node=3=6 dD=24cm Len=24cm
Radiator 'Rad1' Def='du2' Node=4
Radiator 'Rad2' Def='du3' Node=6

AcouCompliance 'Ca1' Node=3=0
Ca={Vb=0.220;roh=1.1871;c=343.3; Vb/(roh*sqr(c)) }

 

[CRESCENDO]

You didn't scroll up on the desiggn parameters, the filter details got cut off. I'll check your design when I get home, and get back with you tomorrow.

Wup, sorry about that.

 

[CRESCENDO]

Lv: 204.7mm
___________

Fx: 37Hz
Qx: 1.93

 

[djk]

"I was just about to ask if a DSP would act the same by doing the above. Glad to hear it. "The filter is -3dB at 35hz" - I'm assuming you're referring to the Linkwitz-Riley type of filer."

The DSP filter should be a Butterworth, -3dB type, and add to that the 9dB of boost, so the result will be 6dB of boost.

"And since we're boosting at the high-pass cut-off, we don't need 3x the power (6dB of EQ), right? We're just making up for the filter..? "

We need a Q=2 filter at Fb, a Q=2 filter has 6dB of boost.

"Do you use fill in your sub boxes??

Absolu8tely not.

"Is it at all difficult to mount/remove drivers from the plenum?"

Not really. Just go slow and think it through. Smaller drivers end up with a smaller plenum, those can be a squeeze.

"I'm trying to think of smart enclosure and plenum dimensions to box this PPSL enclosure with the two 3015LF drivers I still have in the box."

I only make the plenum the total height of the inverted driver, add the frame thickness of the other, plus about 1/4" to spare.

 

[CRESCENDO]

"a Q=2 filter has 6dB of boost."

Just a note: In my DSP (dbx 260), it looks like the Q and dB are independently adjustable. I see what you're saying tho, as far as the HPF + EQ go.

So, to run this cab properly, what should the amp be capable of @ 4 ohms? 3600W?

 

[chrapladm]

Scott L any more progress?

I just saw this thread a think I might need to build one of these now. And because all dimensions can be changed does that mean I can make my cabinet what ever width dimensions to fit a pair of 12's?

I am stuck with 22" width as my maximum width dimension.