Hello all,
I am sorely tempted to build a small PPSL for my living room / car.
I was thinking of 8" or 10" drivers to keep it super compact, hopefully with a room / car F3 somewhere around 30hz. (not winning any SPL contests I know!)
Had anyone got any good leads for drivers? Keen to keep the cost below £200 if possible! I have had a quick look at car drivers, but unsure which to trust to be honest. Happy to sim in WinISD.
Power will be a TAS5630 @ 50v (140@8r, 240@4r) in home, unsure about car..
Many thanks in advance,
I am sorely tempted to build a small PPSL for my living room / car.
I was thinking of 8" or 10" drivers to keep it super compact, hopefully with a room / car F3 somewhere around 30hz. (not winning any SPL contests I know!)
Had anyone got any good leads for drivers? Keen to keep the cost below £200 if possible! I have had a quick look at car drivers, but unsure which to trust to be honest. Happy to sim in WinISD.
Power will be a TAS5630 @ 50v (140@8r, 240@4r) in home, unsure about car..
Many thanks in advance,
car sub
Hi there zk: I have had good results from a RE Electronics 10-inch: 10D4, a 4-ohm dual voice coil driver. I have used it experimentally in numerous enclosures, boxes to a 9-foot Karlson tube with the back in OB. Purchased at Sonix Electronics in the USA for about $65. There are similar new models which would work in a ppsl box. Alpine and JBL (gto) are two other well regarded car sub brands who publish T/S parameters for their products. ...regards, Michael
Hi there zk: I have had good results from a RE Electronics 10-inch: 10D4, a 4-ohm dual voice coil driver. I have used it experimentally in numerous enclosures, boxes to a 9-foot Karlson tube with the back in OB. Purchased at Sonix Electronics in the USA for about $65. There are similar new models which would work in a ppsl box. Alpine and JBL (gto) are two other well regarded car sub brands who publish T/S parameters for their products. ...regards, Michael
Thanks Michael, I have done some more digging, and seems perhaps I was being too skeptical of car audio!
I have done some simulation and rough CAD on the Alpine SWR-8D2. It seems like an excellent driver, even if it's on the edge of budget (£180/pair). I seem to only be able to come up with extremely long port lengths that far exceed Alpines "suggested box" available here http://download.alpine.com.au/Products/Subwoofers/Type-RSubwoofers/SWR-8D4/SWR-8D2_8D4_EN.pdf
They reckon with a 0.55ft3 box you can get away with a 15.5" port tuned to 36-40hz.. When I run my sim in WinISD I end up with a 45" port for <20m/s velocities at this tuning, or a significantly higher tuning for the 15.5"! Can anyone advise on this discrepancy?
Otherwise, the sim looks great! This port is just a sod to fit into a box....
I have done some simulation and rough CAD on the Alpine SWR-8D2. It seems like an excellent driver, even if it's on the edge of budget (£180/pair). I seem to only be able to come up with extremely long port lengths that far exceed Alpines "suggested box" available here http://download.alpine.com.au/Products/Subwoofers/Type-RSubwoofers/SWR-8D4/SWR-8D2_8D4_EN.pdf
They reckon with a 0.55ft3 box you can get away with a 15.5" port tuned to 36-40hz.. When I run my sim in WinISD I end up with a 45" port for <20m/s velocities at this tuning, or a significantly higher tuning for the 15.5"! Can anyone advise on this discrepancy?
Otherwise, the sim looks great! This port is just a sod to fit into a box....
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Redo box calculation for 2 drivers in 1 box
Hi there zk: I ran your input data in the screen shots you provided and found the same 46.8-inch port by 4-inch diameter, however, your input data was missing the following parameters: Re and Vas. I went to Re Electronics we site to find Re=3,7 ohms and Vas=10.3Liters. Now since your drawing shows 2 drivers in the same box I re-did the calc's for Sd=2x201=402, series voice coils for both drivers Re=3.7x2=7.4, then electrically connect in parallel them to get back to Re=3.7. Now the calc's: box internal volume 1.22CF, port 4-inches diameter, port 21-inches long (you must add the volume of the ports, drivers displacement and bracing to the 1.22 CF to get the internal volume. Note that you can change the porting to a rectangular section along the walls using the same area and length. I did not address the front side slot dimensions. Others on this site have stated that it should be minimum depth consistent with the drivers diameters. Hope you will post your design, construction progress and listening experience. ...regards, Michael
Hi there zk: I ran your input data in the screen shots you provided and found the same 46.8-inch port by 4-inch diameter, however, your input data was missing the following parameters: Re and Vas. I went to Re Electronics we site to find Re=3,7 ohms and Vas=10.3Liters. Now since your drawing shows 2 drivers in the same box I re-did the calc's for Sd=2x201=402, series voice coils for both drivers Re=3.7x2=7.4, then electrically connect in parallel them to get back to Re=3.7. Now the calc's: box internal volume 1.22CF, port 4-inches diameter, port 21-inches long (you must add the volume of the ports, drivers displacement and bracing to the 1.22 CF to get the internal volume. Note that you can change the porting to a rectangular section along the walls using the same area and length. I did not address the front side slot dimensions. Others on this site have stated that it should be minimum depth consistent with the drivers diameters. Hope you will post your design, construction progress and listening experience. ...regards, Michael
Hi Michael,
Thank you very much for running the simulation and the detailed reply.
I am having much difficulty attaining your result with the 21 inch port. Could you possibly share your input values?
It seems though that I may well be able to shrink the port diameter down, I have found the excellent program "flare it" which shows how far you can restrict a circular duct so long as generous flares are maintained. I have access to 3D printing, so is an ideal combination!
And of course, I plan to update all the construction and plans on here
Thank you very much for running the simulation and the detailed reply.
I am having much difficulty attaining your result with the 21 inch port. Could you possibly share your input values?
It seems though that I may well be able to shrink the port diameter down, I have found the excellent program "flare it" which shows how far you can restrict a circular duct so long as generous flares are maintained. I have access to 3D printing, so is an ideal combination!
And of course, I plan to update all the construction and plans on here
REcalc LDC7 program
Hi there zk: I use a different program, however, the T/S parameters are the same. So Here goes: Fs=40hz, Xm=12mm, Z=4-ohms, Re=3.7*, Pe=350w, 2xSd= 402cm^2,2x Vas=20.6L, Vb=1.22cf (I tried several but settled on this volume for 2 drivers in one box to attain F3=32hz, Fb=34hz, Pd=350.8w, SPL=110.6db with a 4"dia. vent 21" long). Note flared vents are considered to be excellent, however I have not tried them. Wish I could draw using a computer like you and others do, old dog no new tricks here. ...regards, Michael, P.S. 1st post showed how I attained Re=3.7 for DVC voice coils in series parallel ...JMD
Hi there zk: I use a different program, however, the T/S parameters are the same. So Here goes: Fs=40hz, Xm=12mm, Z=4-ohms, Re=3.7*, Pe=350w, 2xSd= 402cm^2,2x Vas=20.6L, Vb=1.22cf (I tried several but settled on this volume for 2 drivers in one box to attain F3=32hz, Fb=34hz, Pd=350.8w, SPL=110.6db with a 4"dia. vent 21" long). Note flared vents are considered to be excellent, however I have not tried them. Wish I could draw using a computer like you and others do, old dog no new tricks here. ...regards, Michael, P.S. 1st post showed how I attained Re=3.7 for DVC voice coils in series parallel ...JMD
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Hi Michael,
Thanks very much for your input. I now have the simulations working as intended!
See below for almost finalised design. It seems to be as much performance as I can squeeze out of a <70L external volume (36L internal). The port has been a very interesting area, I have read several AES papers and used the Flareit program to create a very small and optimised port. Only downside is that it requires 3x 3D printed parts, but this is no problem for me.
Maybe I will throw through FEA or COMSOL, I am not sure how much time to spend before build and test!
Flareit image doesn't seem to be current.. Disregard
Thanks very much for your input. I now have the simulations working as intended!
See below for almost finalised design. It seems to be as much performance as I can squeeze out of a <70L external volume (36L internal). The port has been a very interesting area, I have read several AES papers and used the Flareit program to create a very small and optimised port. Only downside is that it requires 3x 3D printed parts, but this is no problem for me.
Maybe I will throw through FEA or COMSOL, I am not sure how much time to spend before build and test!
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Flareit image doesn't seem to be current.. Disregard
Okay! I will do simulation when I get the chance
In the meantime, I have read several pieces by J. Vanderkooy, (AES Convention 1997, 1998) which tackles the effect of port compression and turbulence through duct inlet geometry. For this reason I have applied a 7deg taper to the port ends in the hope of keeping the flow relatively attached on the exhaust stroke. This is then combined with a G2 curve to 90deg to keep the intake stroke clean. Without CFD showing the effect of the system esp. with the 90deg bend I can't be sure it'll be enough - but 3D printing does get expensive!
Hopefully this will reduce port compression and vortices away from the ragged edge of performance
In the meantime, I have read several pieces by J. Vanderkooy, (AES Convention 1997, 1998) which tackles the effect of port compression and turbulence through duct inlet geometry. For this reason I have applied a 7deg taper to the port ends in the hope of keeping the flow relatively attached on the exhaust stroke. This is then combined with a G2 curve to 90deg to keep the intake stroke clean. Without CFD showing the effect of the system esp. with the 90deg bend I can't be sure it'll be enough - but 3D printing does get expensive!
Hopefully this will reduce port compression and vortices away from the ragged edge of performance
An externally hosted image should be here but it was not working when we last tested it.
implementation
Hi there zk: Nice implementation in post #9, the "final"drawing, wherein you incorporated a slanted panel above the driver in the forward slot. Looks like this panel reduces the slot volume and better uses the box volume. However, post #12 seems shows the back of the slot to be vertical? Was this a construction simplification or a design consideration. At any rate, from drawing the project looks great. Hope you will keep the community posted on progress, listening experience and (measurements if possible). regards, Michael
Hi there zk: Nice implementation in post #9, the "final"drawing, wherein you incorporated a slanted panel above the driver in the forward slot. Looks like this panel reduces the slot volume and better uses the box volume. However, post #12 seems shows the back of the slot to be vertical? Was this a construction simplification or a design consideration. At any rate, from drawing the project looks great. Hope you will keep the community posted on progress, listening experience and (measurements if possible). regards, Michael
Small update
Small update! Have been super busy but managed to find this weekend (and sun!!)
Wood is going together, and have finished off the front flare. It is a glass fill nylon sanded then painted (after a fiasco with dyes ... Black turned out a pale blue). Finally then post polymerised - so should be fairly resilient to any abuse.
Was also slightly worried about the rear of the cone being restricted by the MDF, so have cut some small relief chamfers. Seems much better now!
Should be finalised this weekend, just assembly left
Small update! Have been super busy but managed to find this weekend (and sun!!)
Wood is going together, and have finished off the front flare. It is a glass fill nylon sanded then painted (after a fiasco with dyes ... Black turned out a pale blue). Finally then post polymerised - so should be fairly resilient to any abuse.
Was also slightly worried about the rear of the cone being restricted by the MDF, so have cut some small relief chamfers. Seems much better now!
Should be finalised this weekend, just assembly left
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Slowly getting there
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