I was wondering if someone could help me design the following PPSL enclosure. I have a few rough calculations below but would really appreciate if someone could help fine tune the design.
PPSL Enclosure
(2) Sigma Pro 18-2 (large 120oz magnet version)
http://www.eminence.com/pdf/Sigma_Pro_18A_2.pdf
Potential Box Tuning is Driver FS = 28hz
Volume Calculation is based on the following formula:
4 times (QTS-squared) times VAS or
4 x (0.29x0.29) x 441.2 = 148.4 liters
that is 5.25cuft per driver so the box will be 10.5cuft.
The front slot is going to 9"x19" (171 square inches) or a close 2:1 ratio with the SD of the double sigma 18s. This dimension allows access to install drivers from the front.
12db High Pass filter at FS = 28hz with a Q=2
I have attached a preliminary box design showing the rough WxLxH. There is not a slot port shown as I am not sure how to calculate that. Can you help calculate the vent size and depth? and let me know if I am on the correct path.
Thanks,
PPSL Enclosure
(2) Sigma Pro 18-2 (large 120oz magnet version)
http://www.eminence.com/pdf/Sigma_Pro_18A_2.pdf
Potential Box Tuning is Driver FS = 28hz
Volume Calculation is based on the following formula:
4 times (QTS-squared) times VAS or
4 x (0.29x0.29) x 441.2 = 148.4 liters
that is 5.25cuft per driver so the box will be 10.5cuft.
The front slot is going to 9"x19" (171 square inches) or a close 2:1 ratio with the SD of the double sigma 18s. This dimension allows access to install drivers from the front.
12db High Pass filter at FS = 28hz with a Q=2
I have attached a preliminary box design showing the rough WxLxH. There is not a slot port shown as I am not sure how to calculate that. Can you help calculate the vent size and depth? and let me know if I am on the correct path.
Thanks,
:/
I dont know about the viability of your design.
I'm in no way an expert on simming slot loaded bass reflex boxes (this is my first one)
for an ideal tuning at fs (flat to fs) , you would want box size equals VAS (so around 900 liters for 2 drivers).
Heres what my rough sim of your box looks like, 300 liters tuned to 28hz, slot loaded.
runs out of xmax at 35v, f3 (before filter) of around 37hz. starts rolling off at 43ish. peaks out at about 123db max output.
I dont know about the viability of your design.
I'm in no way an expert on simming slot loaded bass reflex boxes (this is my first one)
for an ideal tuning at fs (flat to fs) , you would want box size equals VAS (so around 900 liters for 2 drivers).
Heres what my rough sim of your box looks like, 300 liters tuned to 28hz, slot loaded.
runs out of xmax at 35v, f3 (before filter) of around 37hz. starts rolling off at 43ish. peaks out at about 123db max output.
Attachments
IMO if the driver won't take full power down to FS then you either have the wrong driver for the design or the wrong design for the driver, change one or the other until they match. 123db max from a pair of 18's is pathetic.
I understand these are not the best drivers for PA High volume use. The intended use is low distortion hifi to match up with a high efficiency horn system. The xmas is 6mm but the xlim is 18mm, not saying it is a good thing to go into that range because of the increase distortion and lower sensitivity.
Bagend has successfully design their InfraSUB around this driver or one based off it boosting the bass 12db an octave below the system resonance - similar to my idea expect a PPSL instead of sealed enclosure.
Bag End S18E-D
Bagend has successfully design their InfraSUB around this driver or one based off it boosting the bass 12db an octave below the system resonance - similar to my idea expect a PPSL instead of sealed enclosure.
Bag End S18E-D
the thing is that vented and sealed enclosures work in very different ways. a sealed enclosure would allow better excursion control above fs (which is where you run into issues in a vented enclosure tuned to 28hz), and better excursion control below box tuning as well, which allows them to boost down low. remember, every db of boost down low equates to a db lost in overall powerhandling.
If you have plenty of power available, and don't listen real loud, nothing wrong with the Bag End approach. That said, if you are planning to push the drivers past Xmax, the PPSL won't do much for distortion reduction, and does not reduce odd order distortion.
Bag End uses a frequency dependent limiter to keep LF from exceeding Xmax at high drive levels, referred to as “concealment”, which hides the fact that the system produces far less LF than drivers with more Xmax potential in ported or horn loaded enclosures.
“The ELF concealment performs dynamic control of reducing the low frequency extension. It will allow the system to play with the upper bass notes unaffected while protecting the system from overload caused by playing the lower notes louder than the amplifier and/or loudspeaker can reproduce safely and
undistorted.”
“While the INFRASUB-18 will reproduce 8 Hz, it is not audible nor does it have enough acoustical power for you to feel it. The measurements are taken at close range with sensitive instruments. To achieve a flat response, as shown in figure 1, full amplifier power (400 watts) is used at the lowest frequencies and very little (<1 Watt) in the upper frequency range.”
Anyway, I'm happy with the output of my home stereo using a sealed slot loaded 2x12" with no more Xmax than the Sigma pro 18-2A, not everybody needs bass response you can feel.
Art
Your driver, 96db each.
Tuning to 28hz (6th order), max excursion around 40hz.
6mm should be good for over 200watts each driver.
So 102db (pair) + 400w (26db), that'll make plenty of noise all the way down.
I had dual 18's (4.3mm xmax) 6th ordered to 27hz.
140wrms (each) to skip past xmax.
They went plenty plenty loud in a basement.
I only needed 1 box (I had 2) to keep up with 101db cerwin vega dx-9's (3 way with 15") crossed at 100hz.
400watts will not be 6db louder than 100watts but may be 3db (voice coil heats up losing magnet strength)
If you want sheer output for PA, a 6th order tuned to 35hz eminence kappa pro 15lf can take over 600watts (each) before skipping past xmax.
Look up djk and his ppsl.
4 boxes of double 15's, hole-e-cow loud.
For PA, I wouldn't bother to tune below 35hz.
And for home, 27hz was fine for me.
He even has a cut list.
I was contemplating the stereo integrity 18's (22mm xmax) for a ppsl but sealed and boosted for a flat to 20hz design. Sealed unboosted F3 is around 31hz I believe in 10ft3 (for 2 drivers). Easy to make. MemX has a thread of 2 boxes just made. I think they (in a house) would be fantastic even without the boost, maybe 20hz subsonic protection...............
http://www.diyaudio.com/forums/subwoofers/242665-looking-build-2x18-enclosure-ppsl-4.html
Bag end uses a 4.5" voice coil (high power) driver in a tiny box that naturally sealed (smaller than .707 qtc) rolls at 80hz, so they need the 12db/octave bass boost. But the 24db of boost to get down to 20hz, you lose output. And the driver is working very hard = distortion. Nowhere near a velodyne or a push pull for the clean bass. Way down deep had a comparison of snell, bag end, velodyne. Bag end (21") didn't do very well for output down low and distortion for its 4.2k price. 110db for 30hz then rolling. Way Down Deep II Bag End S21E | Sound & Vision
Now 128db (125db@27hz before room gain) for your double 18's isn't enough?
Norman
Tuning to 28hz (6th order), max excursion around 40hz.
6mm should be good for over 200watts each driver.
So 102db (pair) + 400w (26db), that'll make plenty of noise all the way down.
I had dual 18's (4.3mm xmax) 6th ordered to 27hz.
140wrms (each) to skip past xmax.
They went plenty plenty loud in a basement.
I only needed 1 box (I had 2) to keep up with 101db cerwin vega dx-9's (3 way with 15") crossed at 100hz.
400watts will not be 6db louder than 100watts but may be 3db (voice coil heats up losing magnet strength)
If you want sheer output for PA, a 6th order tuned to 35hz eminence kappa pro 15lf can take over 600watts (each) before skipping past xmax.
Look up djk and his ppsl.
4 boxes of double 15's, hole-e-cow loud.
For PA, I wouldn't bother to tune below 35hz.
And for home, 27hz was fine for me.
He even has a cut list.
I was contemplating the stereo integrity 18's (22mm xmax) for a ppsl but sealed and boosted for a flat to 20hz design. Sealed unboosted F3 is around 31hz I believe in 10ft3 (for 2 drivers). Easy to make. MemX has a thread of 2 boxes just made. I think they (in a house) would be fantastic even without the boost, maybe 20hz subsonic protection...............
http://www.diyaudio.com/forums/subwoofers/242665-looking-build-2x18-enclosure-ppsl-4.html
Bag end uses a 4.5" voice coil (high power) driver in a tiny box that naturally sealed (smaller than .707 qtc) rolls at 80hz, so they need the 12db/octave bass boost. But the 24db of boost to get down to 20hz, you lose output. And the driver is working very hard = distortion. Nowhere near a velodyne or a push pull for the clean bass. Way down deep had a comparison of snell, bag end, velodyne. Bag end (21") didn't do very well for output down low and distortion for its 4.2k price. 110db for 30hz then rolling. Way Down Deep II Bag End S21E | Sound & Vision
Now 128db (125db@27hz before room gain) for your double 18's isn't enough?
Norman
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I used to run 4- Eminence 18 in vented boxes 6 and 8.2 cubic feet tuned around 28 - did ok in a 28x19x8 room- sometimes - these days I might prefer a tapped-twqt with 12". PPSL should help matters within xmax.
re:SI - if you could find good caps then you might extend the sealed boxes LF.
re:SI - if you could find good caps then you might extend the sealed boxes LF.
An externally hosted image should be here but it was not working when we last tested it.
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Helloooo!
Pah, I am building them to try to give me as much as possible below 20Hz!
😀Hopefully, if my calculations are correct, with possible room gain of 10-12dB/Octave I should be able to achieve almost 125dB in-room all the way down to system roll-off (the CV5000 is -3dB @ 5Hz, according to the spec)...
I might be wrong, of course 😕 but I am hopeful that I will be well into single-digit Hz Reference-level playback for movies 🙂
It would be great if you could/would build with the same driver, Norman, I'd be interested to see what your thoughts on them were! They should be available later this year, it seems, and for <$200 a driver, they do seem a bit of a bargain.
Sim of Slot Loaded P-P Band Pass Sub (SLPPBPS)
Using 300 liters for the chamber and dual 3.0 in deep x 19.0 in high x 20.0 in long channel vents leading to the single 19 in tall x 9 in wide x 19 in deep front-firing slot port, I get the following results. To get a flat response and maximize bass extension, I set the -12 dB/oct high pass filter at 25 Hz. You run out of xmax at around 28 volts. This gives a max SPL (into half space) of 117.5 dB at 40 Hz and -3dB point is 29 Hz.
Freq response at xmax with 28 volts drive:
Cone excursion at 28 volts:
Impedance:
With 120 Hz -24dB/oct low pass filter applied:
Using 300 liters for the chamber and dual 3.0 in deep x 19.0 in high x 20.0 in long channel vents leading to the single 19 in tall x 9 in wide x 19 in deep front-firing slot port, I get the following results. To get a flat response and maximize bass extension, I set the -12 dB/oct high pass filter at 25 Hz. You run out of xmax at around 28 volts. This gives a max SPL (into half space) of 117.5 dB at 40 Hz and -3dB point is 29 Hz.
Freq response at xmax with 28 volts drive:
Cone excursion at 28 volts:
Impedance:
With 120 Hz -24dB/oct low pass filter applied:
Attachments
Thanks for the replies... Quick question on the above design.
Would increasing the chamber size to 400 or even 500 liters help with extending the bottom end closer to 20Hz with 12db HP and 24db LP?
This design can sacrifice output for extension
And is this image the box layout described above?
Would increasing the chamber size to 400 or even 500 liters help with extending the bottom end closer to 20Hz with 12db HP and 24db LP?
This design can sacrifice output for extension
And is this image the box layout described above?
Attachments
the real issue is that the sigma 18 runs out of xmax ABOVE The displacement minima (aka, above 28 hz, around 38hz) with little power in. It would be beneficial (IF YOU GO PORTED) to both slightly increase box size, and tune a little higher (moveing excursion minima up to around 35hz would likely help.
a 12 db hp is not going going to cut it.
a 12 db hp is not going going to cut it.
Just came across this design on another post... POST #6
What do you think?
http://www.diyaudio.com/forums/subwoofers/255959-sim-slbp_pp-maybe-more.html#post3919938
What do you think?
http://www.diyaudio.com/forums/subwoofers/255959-sim-slbp_pp-maybe-more.html#post3919938
Guiness,
Yes, the picture is close - I removed the front horn expansion on yours as you did not seem to have or want that. The design on the other thread was done for CLS and is essentially the same but with tweaked dimensions to match what you specified. I think both are fine but like the extension if the one I did for CLS better. If you can sacrifice SPL then that one is better. You should build it. 😀
Btw, go with a -24dB/oct HPF to achieve better bass extension as it lets you cut the excursion deeper down.
Yes, the picture is close - I removed the front horn expansion on yours as you did not seem to have or want that. The design on the other thread was done for CLS and is essentially the same but with tweaked dimensions to match what you specified. I think both are fine but like the extension if the one I did for CLS better. If you can sacrifice SPL then that one is better. You should build it. 😀
Btw, go with a -24dB/oct HPF to achieve better bass extension as it lets you cut the excursion deeper down.
Sounds good... I will draw it up in Autocad this weekend and run the final design by you for comment.
maybe some day I'll get the st integrity subs.
I have a 4 x 12" ppsl ready in a couple of weeks using the dayton 12" 8mm st305 series2 (Fs 30hz, qts around .35).
The brilliance of 6th order is you get 6db of boost at tuning (the driver won't move much, it would have been 9db down at tuning before boost), and the filter acts as a subsonic filter below that.
Yup. Those are the choices. Very very low but less volume, or way more volume but tune higher.
Norman
I have a 4 x 12" ppsl ready in a couple of weeks using the dayton 12" 8mm st305 series2 (Fs 30hz, qts around .35).
The brilliance of 6th order is you get 6db of boost at tuning (the driver won't move much, it would have been 9db down at tuning before boost), and the filter acts as a subsonic filter below that.
Yup. Those are the choices. Very very low but less volume, or way more volume but tune higher.
Norman
Two each Sigma 18A-2
13 cu ft net
4 ports 10.875 x 2 x 19", 10M/sec
28hz Fb, Fs, F3, Faux
Faux=28hz Q=2
600W does not exceed x-max
103dB/2.83V/1M at 50hz (4Ω load), 125dB at 50hz with a 600W/4Ω amplifier, 120dB at 28hz (before room gain).
About 24" H x 48" W x 30" D, 2" ports on each side (brace down the center).
13 cu ft net
4 ports 10.875 x 2 x 19", 10M/sec
28hz Fb, Fs, F3, Faux
Faux=28hz Q=2
600W does not exceed x-max
103dB/2.83V/1M at 50hz (4Ω load), 125dB at 50hz with a 600W/4Ω amplifier, 120dB at 28hz (before room gain).
About 24" H x 48" W x 30" D, 2" ports on each side (brace down the center).
Thanks DJK
I spent sometime this morning laying out DJK's design in Autocad, calculating the NET volume after driver displac., bracing, port volume, etc. Pretty much 13cuft on the nose. The attached PDF is what I am planning on building (bracing not shown).
I spent sometime this morning laying out DJK's design in Autocad, calculating the NET volume after driver displac., bracing, port volume, etc. Pretty much 13cuft on the nose. The attached PDF is what I am planning on building (bracing not shown).
In the numbers of sim, (pathetic) 6mm Xmax and limited extension are not giving you bragging right, but in the real world and domestic use, it's enough to shake the house and bother the neighbors.
Actually, the driver is somewhat lazy in low level listening. I always feel it's getting better (properly stretching its legs) in louder situations, while that SPL would bother me myself if playing time is longer than 1hr or so. (yes, it's enjoying when the mood is right, but eventually making me tired and guilty...)
Because of that, I wish I bought 15" instead of 18". (Oh, the reason I bought it is because it's cheap and decent enough. So there must be better choice nowadays.)
Actually, the driver is somewhat lazy in low level listening. I always feel it's getting better (properly stretching its legs) in louder situations, while that SPL would bother me myself if playing time is longer than 1hr or so. (yes, it's enjoying when the mood is right, but eventually making me tired and guilty...)
Because of that, I wish I bought 15" instead of 18". (Oh, the reason I bought it is because it's cheap and decent enough. So there must be better choice nowadays.)
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