A Thread for those interested in PPSL enclosures - Page 27 - diyAudio
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Old 17th April 2012, 11:07 PM   #261
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DJK
Post #139 are thoes tops similar to these http://www.youtube.com/watch?feature...v=48qUpmBjQsQ?
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Old 18th April 2012, 06:53 PM   #262
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Not at all.

The tops in the video are a joke, the 'horn' does nothing at higher frequencies.

You must use proper drivers suited for a horn, and build a properly designed horn.

Hornresp (by David McBean) has made it possible for a non-technical person to test a driver and horn design without making any sawdust, wasting any time, or money.

Any cabinet with any driver will make sound (noise), but designing something that sounds good (works properly) takes skill, not luck.

The skill of David McBean makes it so you don't need to be skilled, but to get lucky you still need some basic knowledge.

Click the image to open in full size.
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Old 18th April 2012, 07:13 PM   #263
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The captions say it all, scale it up or down as needed.

An impedance variation of 2:1 (fig. 5.10C) will have a ripple of 3dB.

As the horn mouth and length approach infinity the output becomes smoother, but output at the Fc of the horn drops to zero (you can have too big of a mouth).

Increasing the throat size makes the horn shorter, but also raises the Fc.

Hornresp knows all this, but you knowing this will save you time in using Hornresp.

On selecting drivers, the higher the mass corner, the higher the response will go before needing EQ. For a bass horn pick the lowest efficiency driver that has a mass corner close to where you intend to cross it at.

Mass corner = 2(Fs/Qes).

These are simplifications, but they should help you get started.

Click the image to open in full size.

(suggested use for old large-throat short horns)
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Last edited by djk; 18th April 2012 at 07:17 PM.
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Old 21st April 2012, 10:10 PM   #264
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any thoughts on what 12" beyma or B&C drivers would be suitable for PPSL loading aiming for results not inferior to these of dayton 12" posted here....?

(no dayton available here where i live)....
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Old 21st April 2012, 10:39 PM   #265
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Driver Properties
Name: 12BR70
Type: Standard one-way driver
Company: Beyma
No. of Drivers = 2
Mounting = Standard
Wiring = Parallel
Fs = 35 Hz
Qms = 1.89
Vas = 135 liters
Cms = 0.38 mm/N
Mms = 54.38 g
Rms = 6.328 kg/s
Xmax = 6 mm
Xmech = 9 mm
P-Dia = 252.3 mm
Sd = 500 sq.cm
P-Vd = 0.3 liters
Qes = 0.44
Re = 5.6 ohms
Le = 1 mH
Z = 8 ohms
BL = 12.34 Tm
Pe = 125 watts
Qts = 0.357
no = 1.268 %
1-W SPL = 93.18 dB
2.83-V SPL = 94.73 dB
-----------------------------------------
Box Properties
Name:
Type: Vented Box w/ Active HP Filter
Shape: Prism, square (optimum)
Vb = 4.98 cu.ft
Fb = 29.42 Hz
QL = 6.178
F3 = 31.95 Hz
Fill = minimal
No. of Vents = 1
Vent shape = other
Vent ends = one flush
Av = 31.22 sq.in
Lv = 14 in
-----------------------------------------
Active 12 dB/oct. HP Filter
Fx = 31.48 Hz
Qx = 1.93
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Old 23rd April 2012, 07:31 AM   #266
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Default Question regarding the djk PPSL design using the Martin Sound 1844 drivers

Hi djk,

I seriously consider using your PPSL design for the Martin Sound #1844 drivers (please see attached file) for home use (not PA).

1. Is it correctly understood that the total internal volume for each box (Fb = 31Hz) for two drivers is 8 cf? (I just want to make sure about the size before I start drawing)

2. It says "minimal fill" in the simulation. Would 1" of foam/fill on all internal surfaces be ok, or what will you recommend?

3. Are the two drivers in each box wired with the same polarity or one of them reversed?

Thanks a lot!

Best regards
Peter
Attached Images
File Type: gif DJK PPSL design with Martin Sound 1844 drivers.gif (159.2 KB, 465 views)
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Old 23rd April 2012, 07:53 AM   #267
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I'm not djk, but can help a bit.

1. Yes. Make sure to accommodate for extra space needed for the plenum and port.
2. He doesn't use fill on his sub cabs
3. One driver is wired in reverse

Just some simple answers. Maybe djk will report w/more info if needed.

Cheers,
Justin
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Old 23rd April 2012, 08:01 AM   #268
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1) Yes, the net-net volume is 8 cu ft. The boxes are 36W x 24H x 30D (3/4" ply) and take about 1-1/2 sheets per box (IIRC).

2) I don't actually use any fill for PA, minimal to prevent reflections getting out of the port should be fine. Use your judgment here.

3) The driver you can see the magnet on is wired with reverse polarity.

Depending on your room gain you may be able to lower the Q of the filter. In one home I was able to lower the Q to 1 (no boost) and the response was still flat to 30hz. Use your judgment here too, especially if playing records (you need the filter).

Bigger boxes can go even lower:

Box Properties
Name:
Type: Vented Box w/ Active HP Filter
Shape: Prism, square (optimum)
Vb = 10 cu.ft
Fb = 25 Hz
QL = 5.962
F3 = 24.39 Hz
Fill = minimal
No. of Vents = 2
Vent shape = other
Vent ends = two flush
Av = 23.98 sq.in
Lv = 13.87 in
-----------------------------------------
Active 12 dB/oct. HP Filter
Fx = 25 Hz
Qx = 2
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Old 23rd April 2012, 08:16 AM   #269
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Hi djk and Justin,

Thank you so much to both of you! I think I will go for the bigger 10 cf version. I will make the drawings and get back for a sanity check before having the cabs build

Thanks once again!

Best regards
Peter



Quote:
Originally Posted by djk View Post
1) Yes, the net-net volume is 8 cu ft. The boxes are 36W x 24H x 30D (3/4" ply) and take about 1-1/2 sheets per box (IIRC).

2) I don't actually use any fill for PA, minimal to prevent reflections getting out of the port should be fine. Use your judgment here.

3) The driver you can see the magnet on is wired with reverse polarity.

Depending on your room gain you may be able to lower the Q of the filter. In one home I was able to lower the Q to 1 (no boost) and the response was still flat to 30hz. Use your judgment here too, especially if playing records (you need the filter).

Bigger boxes can go even lower:

Box Properties
Name:
Type: Vented Box w/ Active HP Filter
Shape: Prism, square (optimum)
Vb = 10 cu.ft
Fb = 25 Hz
QL = 5.962
F3 = 24.39 Hz
Fill = minimal
No. of Vents = 2
Vent shape = other
Vent ends = two flush
Av = 23.98 sq.in
Lv = 13.87 in
-----------------------------------------
Active 12 dB/oct. HP Filter
Fx = 25 Hz
Qx = 2
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Old 24th April 2012, 09:28 PM   #270
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Has anyone worked on a corner PPSL woofer design? Perhaps similar in size to the Klipschorn, which has published measurements for comparison.
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