I'm getting ready to make a new subwoofer and reading about the ppsl decided to give it a go.
I could get my hands on some 15" neo drivers really cheap a while a go so I'm going to be using those. They where meant as replacement drivers for the sp15 system from soundprojects. specs: http://www.soundprojects.com/f/11702417977970 or http://www.soundprojects.com/f/13244791575400
I kindly asked the soundprojects guys and a reseller for the TS parameters but (as expected) didn't get an answer so I'll be measuring them myself. I have tried to do this with a multimeter for my previous build but wasn't really satisfied with how it went and I have some doubts about the accuracy of the multimeter at different frequencies.
http://www.diyaudio.com/forums/subwoofers/233438-dual-opposed-shiva-sub-inuke1000dsp.html
I read about the woofer tester and others but it isn't very clear to me which is the one to get and where to get it in Europe.
I have the following design in mind:
It allows me to build the plenum first and measure the drivers as 1 unit inside the plenum. The plenum will go in the middle of the box. The drivers are 15cm tall, plenum is 18cm wide about 46cm high and deep. The sub will be about 0.5 by 0.5 by X meters. The total width, vented or sealed is to be determined after measuring TS. I assume the connecting space between the two sides behind the plenum is sufficient to allow for small differences in volume without causing problems.
So, anyone recognize the driver?
Which measuring tool do I get?
Is the space behind the plenum sufficient to connect the two halves without causing problems?
I could get my hands on some 15" neo drivers really cheap a while a go so I'm going to be using those. They where meant as replacement drivers for the sp15 system from soundprojects. specs: http://www.soundprojects.com/f/11702417977970 or http://www.soundprojects.com/f/13244791575400
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.
I kindly asked the soundprojects guys and a reseller for the TS parameters but (as expected) didn't get an answer so I'll be measuring them myself. I have tried to do this with a multimeter for my previous build but wasn't really satisfied with how it went and I have some doubts about the accuracy of the multimeter at different frequencies.
http://www.diyaudio.com/forums/subwoofers/233438-dual-opposed-shiva-sub-inuke1000dsp.html
I read about the woofer tester and others but it isn't very clear to me which is the one to get and where to get it in Europe.
I have the following design in mind:
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.
It allows me to build the plenum first and measure the drivers as 1 unit inside the plenum. The plenum will go in the middle of the box. The drivers are 15cm tall, plenum is 18cm wide about 46cm high and deep. The sub will be about 0.5 by 0.5 by X meters. The total width, vented or sealed is to be determined after measuring TS. I assume the connecting space between the two sides behind the plenum is sufficient to allow for small differences in volume without causing problems.
So, anyone recognize the driver?
Which measuring tool do I get?
Is the space behind the plenum sufficient to connect the two halves without causing problems?
Last edited:
You can measure TS with REW and a 100ohm resistor and some cables and alligator clips. You will need a DMM which you have and a gram scale and some mass to measure Vas. Works well if you have a stereo line in sound card.
Or spend $100 plus shipping from US for the excellent DATS tool from Dayton Audio via Parts Express. Very accurate and super easy to use.
Or spend $100 plus shipping from US for the excellent DATS tool from Dayton Audio via Parts Express. Very accurate and super easy to use.
@ chris661: pics incoming
Measuring with REW sounds a lot like what i did with an audio card and pc sine generator manually, only a bit more automated and the calculations are done for you. I don't have difficulties doing the calculations, I'm doubting the multimeter measurement (I borrowed one before) for a big part of the range I only had 1 significant digit. If you go looking for a multimeter which specifies accuracy from 10-20000HZ and preferably has multiple significant digits in the measuring range, prices become very high very quickly and since I'll only be using it for speakers might as well buy an easier tool for that.
I'll take a look at the DATS
Measuring with REW sounds a lot like what i did with an audio card and pc sine generator manually, only a bit more automated and the calculations are done for you. I don't have difficulties doing the calculations, I'm doubting the multimeter measurement (I borrowed one before) for a big part of the range I only had 1 significant digit. If you go looking for a multimeter which specifies accuracy from 10-20000HZ and preferably has multiple significant digits in the measuring range, prices become very high very quickly and since I'll only be using it for speakers might as well buy an easier tool for that.
I'll take a look at the DATS
The multimeter is used to measure one value of Re. The rest is done by REW in the sound card.
The triangle sides are 19cm, surface area of 1 triangle is 180cm².
The depth of the triangle is 22cm so 1 triangle volume is ~4000cm³.
I could make the B side a bit wider then the A side to compensate for the decreased volume from the driver.
An externally hosted image should be here but it was not working when we last tested it.
I hooked up the drivers to an amp to loosen the suspension with some brown noise but one driver stops after 3 to 30 seconds depending on volume (faster at higher volume). I'm using a NAD 356bee (80wpc) so I'm not pushing the drivers far. I changed all the wiring from the amp to the drivers which makes no difference.
I think there might be a bad connection or short from the driver lead to the coil. Is there an easy way to fix this or is this something that is better left to professionals?
I think there might be a bad connection or short from the driver lead to the coil. Is there an easy way to fix this or is this something that is better left to professionals?
I made a measurement jig for measuring TS parameters with REW following the very noob friendly instructions on:
https://sites.google.com/site/amateuraudio/projects-1/arta-limp-and-or-room-eq-wizard-impedance-jig
I have to say it's easier then I expected, thanks a lot for the tip.
First measurement of the good driver without calibrating the impedance rig looks plausible:
TS Parameters file
Room EQ V5,00
Dated: 2-feb-2015 21:35:48
From measurement feb 2 21:34:52
Zmin 3,91 ohm
fmin 156 Hz
f3 481 Hz
Le(f3) 0,898 mH
Motional impedance parameters
RES 50,53 ohm
LCES 64,297 mH
CMES 582,2 uF
RAMS 50532,878 mohm
Blocked impedance parameters
RDC 3,40 ohm
dR 0,10 ohm
Re 3,50 ohm
Leb 160,8 uH
Le 1,902 mH
Rss 2239,8 ohm
Ke 0,1084 S-H
Thiele-Small parameters
fs 25,9 Hz
Qms 3,280
Qes 0,331
Qts 0,301
Fts 86,1
Mms 124,42 g
Cms 0,304 mm/N
Rms 6,172 kg/s
Vas 315,06 litres
Bl 14,619 Tm
Eta 1,61 %
Lp (1W/1m) 94,24 dB
Dd 33,00 cm
Sd 855,3 cm^2
Added mass 15,50 g
Secondary measurement: feb 2 21:34:10
Air temperature 20,0 C
Air pressure 1013,25 mB
Air density 1,2041 kg/m^3
Speed of sound 343,2 m/s
I'll have to very accurately measure the 100ohm resistor, do the calibration and let the driver loosen up a bit more for a real measurement.
https://sites.google.com/site/amateuraudio/projects-1/arta-limp-and-or-room-eq-wizard-impedance-jig
I have to say it's easier then I expected, thanks a lot for the tip.
First measurement of the good driver without calibrating the impedance rig looks plausible:
TS Parameters file
Room EQ V5,00
Dated: 2-feb-2015 21:35:48
From measurement feb 2 21:34:52
Zmin 3,91 ohm
fmin 156 Hz
f3 481 Hz
Le(f3) 0,898 mH
Motional impedance parameters
RES 50,53 ohm
LCES 64,297 mH
CMES 582,2 uF
RAMS 50532,878 mohm
Blocked impedance parameters
RDC 3,40 ohm
dR 0,10 ohm
Re 3,50 ohm
Leb 160,8 uH
Le 1,902 mH
Rss 2239,8 ohm
Ke 0,1084 S-H
Thiele-Small parameters
fs 25,9 Hz
Qms 3,280
Qes 0,331
Qts 0,301
Fts 86,1
Mms 124,42 g
Cms 0,304 mm/N
Rms 6,172 kg/s
Vas 315,06 litres
Bl 14,619 Tm
Eta 1,61 %
Lp (1W/1m) 94,24 dB
Dd 33,00 cm
Sd 855,3 cm^2
Added mass 15,50 g
Secondary measurement: feb 2 21:34:10
Air temperature 20,0 C
Air pressure 1013,25 mB
Air density 1,2041 kg/m^3
Speed of sound 343,2 m/s
I'll have to very accurately measure the 100ohm resistor, do the calibration and let the driver loosen up a bit more for a real measurement.
I assume you mean total Sd from 2 drivers (~1600cm²)? The area of the 2 triangles is 360cm², I would have to increase height or depth by at least 10cm to get close to half that.
In any case the volume of 1 side should be the same as the volume of the other side, I was thinking about making 1 side 2cm wider to compensate for the ~5 liter difference from inverting 1 driver.
I'm really not so good with electrical stuff, so I might be completely off but if there is a bad connection in the driver won't I blow up the multimeter because all current will flow through it instead of the driver?
"I assume you mean total Sd from 2 drivers "
No, one driver.
Only the difference between the two sides must flow through the triangles.
"In any case the volume of 1 side should be the same as the volume of the other side, I was thinking about making 1 side 2cm wider to compensate for the ~5 liter difference from inverting 1 driver. "
Making the two sides equal is the best, but the triangles will work when the difference in volumes is small.
"won't I blow up the multimeter because all current will flow through it instead of the driver?"
The meter will not be hurt if the driver blows.
No, one driver.
Only the difference between the two sides must flow through the triangles.
"In any case the volume of 1 side should be the same as the volume of the other side, I was thinking about making 1 side 2cm wider to compensate for the ~5 liter difference from inverting 1 driver. "
Making the two sides equal is the best, but the triangles will work when the difference in volumes is small.
"won't I blow up the multimeter because all current will flow through it instead of the driver?"
The meter will not be hurt if the driver blows.
Glad that worked out. What did you use for the added mass to measure Vas? Did you happen to have a gram scale? I use plastic modeling clay shaped like a big donut.
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