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Old 20th November 2012, 09:37 PM   #21
Juhazi is offline Juhazi  Finland
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And just before i go to bed - I'm not trying keep up with the Joneses. My neighbour has 4x15" is small closed cabs and some kWs of PA power, he is a reggae fan.

Thank you all for your interest and advice so far!
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Old 21st November 2012, 09:21 AM   #22
Juhazi is offline Juhazi  Finland
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Nelson Pass tells some hints to make a slot loaded system The Slot Loaded Open Baffle Project Article By Nelson Pass

The opening area is 1/3 of total membrane area
Cavity depth determines wave cancellation frequency

However I'm not sure about this. The Twin 15" sealed with Q=0,707 is ideal closed arrangement and easy to make, cheap drivers. Perhaps I make a slot arrangement first and if it doesn't work well, a more traditional setup. A sketch will come...
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Old 21st November 2012, 12:50 PM   #23
Juhazi is offline Juhazi  Finland
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A sketch I made, not precise but helps to get the idea.

I'll make two similar 220L closed boxes equipped with Dayton DCS380-4. The boxes are positioned so that elements are opposing each other an covered with a solid top board to make a bench and prevent vibration. The slot has only one open side to the room. The area of opening is 1/3 of total membrane area 2x819,4/3=546,2666..cm2. No legs for boxes.

Slot loading is an old idea an IB is a slot design too. There are many articles and projects in the www but I haven't found info about this kind of system

The slot loads bass some dB but how must and at which frequences?
Resonance and diffraction problems? (not at these Hz?)
The position of the slot in the room is fixed and not optimal
Other problems?

I'm not starting yet but it may be wise to make two cabinets. They can be connected to make slot loading sub or used as two separate subs later on.

Room modes must be handled with more subs and room treatment. Level, xo, phase and low-boost eq will be handled with a Hypex plate amp http://www.hypex.nl/docs/DS40_manual.pdf
Attached Images
File Type: png 2xDayton 15 slot sub.png (9.3 KB, 307 views)
File Type: png hypex ds2.png (46.6 KB, 302 views)
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Last edited by Juhazi; 21st November 2012 at 01:10 PM.
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Old 21st November 2012, 04:09 PM   #24
Juhazi is offline Juhazi  Finland
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3D skeches of my home theater room where the new sub is sitting below the window

SweetHome3D Sweet Home 3D - Draw floor plans and try furniture arrangements
Attached Images
File Type: png teatterikalust2.png (93.7 KB, 304 views)
File Type: png teatterikalust.png (53.5 KB, 290 views)
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Last edited by Juhazi; 21st November 2012 at 04:12 PM.
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Old 22nd November 2012, 11:14 AM   #25
Juhazi is offline Juhazi  Finland
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Some more precise calculations and simulations here:

Each box will have volume of 259L and golden ratio, 38x62x100 cm inside
Boxes can be ported to each other with a pipe to make pressure identical

Some WinISD and Unibox simulations, without slot gain, floor gain:
Q=0.62, F3=35Hz, max spl at F3 108dB (113W), nice group delay, phase and step response like all closed boxes
==> a precise and clean, musical sub for moderate levels? Or perhaps even more?
Attached Images
File Type: png isd spl 2x15 516l.png (31.4 KB, 279 views)
File Type: png unibox 518l 2x15 Dayton.png (84.9 KB, 54 views)
File Type: png unibox impedance step 2x15 516L.png (33.6 KB, 46 views)
File Type: png unibox spl excursion 2x15 518L.png (38.7 KB, 27 views)
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Old 22nd November 2012, 02:42 PM   #26
tb46 is offline tb46  United States
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Hi Juhazi,

I think you are on the correct path now.

You might find this discussion of an arrangement similar to the one you describe in Post #23 interesting: Hornresp (starting @ Post #2981).

I went to the Hornresp thread because I didn't believe my simulation of your Post #23 arrangement. My error (I knew there had to be one) was spotted by Bjorn (Kolbrek), but he and David McBean basically confirmed the frequency response (SPL graph) and the impulse response. I think you would be much better of with two front facing driver in sealed box arrangements. If you want to go with a slot-loaded arrangement I recommend you read through the PPSL thread that you have already posted in. Basically, you need to turn one of the drivers around, and fill in the back corners of the slot. That will reduce the cavity effect.

Regards,
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Old 22nd November 2012, 04:14 PM   #27
Juhazi is offline Juhazi  Finland
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Hi, tb46, thank you very much for trying Hornresp simulation!

drivers shall be set and wired real push pull and the plenum will have 3 walls and rounded back corners. I just can't draw that in GoogleSketch!

I'm afraid of frontside drivers getting damaged too easily, this beast will sit on floor. My first plan no1 was with downfiring drivers and some marketing people call that slot loading too! Downfire is safe but will membranes sag?

I downloded Hornresp but I have no idea which values/measurements to set there. PPSL definitely needs more testing and verifying of procedures. I can only do simple performance measurements indoors at home (uncalibrated REW). Below is the best REW measurements I got with current setup with 5.2 speakers playing (spl not calibrated, microphone moved between measurements)

I have the itch to start building! I guess I'll have the boards cut soon and start making cabs. I must be convinced about the setup before I cut holes for drivers.
Attached Images
File Type: jpg alak PLIIsmall+2sub kooste.jpg (115.8 KB, 48 views)
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Last edited by Juhazi; 22nd November 2012 at 04:38 PM.
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Old 22nd November 2012, 06:27 PM   #28
Juhazi is offline Juhazi  Finland
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Google Sketches of boxes, to get the idea of making the ppsl plenum

Left side with the plenum filling, chamber-connecting tube and driver magnet out.
Right side with the driver magnet in

Hey, if I some day have the money for two RSS390, I could make this to two vented boxes using the openings for pipe as throats of reflex tubes! Honestly, I am sure that the closed one satisfies my spl needs for some time.
Attached Images
File Type: png ppsl518 left.png (20.4 KB, 87 views)
File Type: png ppsl 518 right.png (17.5 KB, 77 views)
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Old 23rd November 2012, 02:49 AM   #29
tb46 is offline tb46  United States
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Hi Juhazi,

Post #27: "...downloded Hornresp but I have no idea which values/measurements to set..."

I'll attach what I think is an appropriate Hornresp simulation for your sealed PPSL arrangement. Assuming an iternal volume of 220L per side, you'll end up with internal box dimensions of about 40x40x137.5cm with the driver mounted on one 40x40cm end. There will be some strong resonances to contend with, most of which will hopefully be attenuated by the crossover. This will also require filling the box with some form of "stuffing".

Some of these boxes you'll just have to build, and try.

I'd stay with the sealed box for this one.

Regards,
Attached Images
File Type: jpg DCS380_sealed_PPSL_Input.jpg (38.7 KB, 66 views)
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Old 23rd November 2012, 06:57 AM   #30
Juhazi is offline Juhazi  Finland
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Thanks Oliver!

I'll make the cabinets using Golden ratio to minimize inside resonances/standing waves, and bigger 259L (h38xd62xw100 cm)

That gives me also some extra space behind the drivers for connecting tube and roundoff filling. Bigger box lowers the Q also which is good for transients and suggested by gurus of ppsl in the other thread.

I'll start learning Hornresp too. I'll take nearfied measurements of output with and without the plenum roundup when I install drivers. Obviously slot/plenum effects must be studied and experimented more.

Juha
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