There r two methods to check thiel small parameters. One is weight method & other is standard box method. Which is better or relable to do? I want to set up my own thiel small parameter set up. Is the test room required to be made soundproof? Any other suggestion for the setup will be appreciated.
Mahendra palesha
Mahendra palesha
TS measurement
I prefer the mass loading ( weight) method as it is easier. You can use Blue-tack or similar material which is freely available in the local market. You can weigh out the sticky material. I use one with 20gms and another 30gms. For large woofers I use them both. The results are quite accurate. If you do not have any design software you can use an Excel spreadsheet for this. You can find these on the net. One packet of Blue-tack ( or equivalent) usually has about 50 gms of material.
Which ever weight you use, split up the material into half and apply on opposite sides of the cone. To make it stick you should press it on to the cone while holding the rear side of the cone with your other fingers. This way you avoid deforming ( and possibly destroying) the cone. When you remove the blue-tack , it will come away clean and not leave any oily marks. If you plan to use the Buue-tack often, better make sure that it is applied with clean ( no grease) hands and that there is no dust on the cones. That way the Blue-tack will last a long time.
Have fun.
I prefer the mass loading ( weight) method as it is easier. You can use Blue-tack or similar material which is freely available in the local market. You can weigh out the sticky material. I use one with 20gms and another 30gms. For large woofers I use them both. The results are quite accurate. If you do not have any design software you can use an Excel spreadsheet for this. You can find these on the net. One packet of Blue-tack ( or equivalent) usually has about 50 gms of material.
Which ever weight you use, split up the material into half and apply on opposite sides of the cone. To make it stick you should press it on to the cone while holding the rear side of the cone with your other fingers. This way you avoid deforming ( and possibly destroying) the cone. When you remove the blue-tack , it will come away clean and not leave any oily marks. If you plan to use the Buue-tack often, better make sure that it is applied with clean ( no grease) hands and that there is no dust on the cones. That way the Blue-tack will last a long time.
Have fun.
The problem with the mass loading method is that you can dirturb the driver compliance while applying the mass, so make sure that the program you use for calculating the parameters can compensate for this. To minimize the errors, apply the added mass first, measure, then remove the mass and remeasure. The compliance is disturbed less this way, as it is easier to remove the mass than to add it.
The best way is to use the reflex enclosure method, which requires just one impedance measurement and optimization, but this technique is not widely practiced.
Andrew
The best way is to use the reflex enclosure method, which requires just one impedance measurement and optimization, but this technique is not widely practiced.
Andrew
I always use a sealed box between 0.25 and 0.5 manufacturer Vas. I mount the driver from the outside and I add the volume of the driver hole and the volume of the cone. The box must be perfectly sealed (put adesive tape around the driver). A very small leak can affect a lot the calculated Vas especially if it is a small woofer. I never use a "sound proof" room since the software do not use a high power signal. I found the difference very very minor (error order).
Many people on this forum haved raved about Speaker Workshop for Thiele-Small testing. I haven't been able to get it set up successfully, but those who have love this program.
It's freeware, you have nothing to lose.
http://www.speakerworkshop.com/
Good luck!
It's freeware, you have nothing to lose.
http://www.speakerworkshop.com/
Good luck!
I use speakerworkshop. This is one of the most crappy interface that I know of but once you followed the tutorial and did a lot of trial and error you can actually do some useful work. The most important thing is correctly calibrate the system.
Use the tutorial on the web, not the help file (this one is incomplete and you have to interpret and guess a lot of commands).
Even if it has a lot of disadvantage, the software works and it is free Believe me, doing all this work by hand reduce the fun of designing speaker (I did it few times).
Use the tutorial on the web, not the help file (this one is incomplete and you have to interpret and guess a lot of commands).
Even if it has a lot of disadvantage, the software works and it is free
Believe me, doing all this work by hand reduce the fun of designing speaker (I did it few times).Eric, the compliance can be affected when attempting to attach the mass just by pulling and pushing on the cone as you attempt to get good adhesion to the cone. Maybe not so much if the drive unit has been well broken in first.
Additionally, depending on the cone strength, the mass can resonate on the cone and cause some errors in the fitting of the calculated impedance curve to the measured one. Finally, added mass can cause the suspension to sag and alter compliance and BL if the drive unit is measured facing upwards.
The added box method can work if the box is properly sealed, and the total volume known accurately. To this end, mounting the driver from the outside, facing in is the preferred way, as it is much easier to calculate the added volume of the cone to the overall box volume.
The vented box method is even better as you only need one measurement, not two!
Andrew
Additionally, depending on the cone strength, the mass can resonate on the cone and cause some errors in the fitting of the calculated impedance curve to the measured one. Finally, added mass can cause the suspension to sag and alter compliance and BL if the drive unit is measured facing upwards.
The added box method can work if the box is properly sealed, and the total volume known accurately. To this end, mounting the driver from the outside, facing in is the preferred way, as it is much easier to calculate the added volume of the cone to the overall box volume.
The vented box method is even better as you only need one measurement, not two!
Andrew
re: testing thiele small
hi i did see in a book how to test using a ported box,il have to go to my library to go find it tho !!!lol,,,
but im sure i did see it,and they found out the Fs,Q,and VAS i think...unless it was my imagination!!
and yeh i dont like the added mass one way of doing it,but i mite have to sometime.
nice forum! just joined today wohoo
hi i did see in a book how to test using a ported box,il have to go to my library to go find it tho !!!lol,,,
but im sure i did see it,and they found out the Fs,Q,and VAS i think...unless it was my imagination!!
and yeh i dont like the added mass one way of doing it,but i mite have to sometime.
nice forum! just joined today wohoo
normally i would use the mass method (like ashok i also use 20 and 30gm of blu tak but i attach it to the dust cap) after break in. to break in I apply a 50hz signal for 4-8 hrs. SS seems to need more, Focal less and Audax Aerogel even less other drivers might need more or less. The Focal W cones for example need more break in than the older Neoflex cones. any idea why? there also seems to be corelation betweeen Mms and break in time. has anyone else observed and / or documented this.
however since palesha is a local manufacturer and would need the box for each driver the sealed box method is better.
1. less chances to destroy the driver by tearing the cone
2. no need to break in the driver
i have used LMS for my purposes and found it accurate enough.
however since palesha is a local manufacturer and would need the box for each driver the sealed box method is better.
1. less chances to destroy the driver by tearing the cone
2. no need to break in the driver
i have used LMS for my purposes and found it accurate enough.
there is a change how significant depends from driver to driver.
for example the SS 8546 woofers (I measured 6) exhibited a change of about 40% (the Qts changed too), however the Audax HM170Z0 and Dynaudio 17W75 drivers hardly changed.
the Focal 8N515 (i measured 4) changed about 15% on the average.
please note that these are from memory. my friend who has LEAP/LMS has moved and I am no longer able to measure my drivers when i want.
I am friendly with another person who has LEAP/LMS but I have to collect my drivers and make time on a Sunday to use his shop as he is a manfacturer and uses his system on other days to work.
I did some measurements on some Vifa drivers and found that they did not change too much (about 15% like the Focals). Yet this change effected a change in box volume from 12 to 15 liters (if I was to keep system Qts to 0.6 for a sealed box).
for example the SS 8546 woofers (I measured 6) exhibited a change of about 40% (the Qts changed too), however the Audax HM170Z0 and Dynaudio 17W75 drivers hardly changed.
the Focal 8N515 (i measured 4) changed about 15% on the average.
please note that these are from memory. my friend who has LEAP/LMS has moved and I am no longer able to measure my drivers when i want.
I am friendly with another person who has LEAP/LMS but I have to collect my drivers and make time on a Sunday to use his shop as he is a manfacturer and uses his system on other days to work.
I did some measurements on some Vifa drivers and found that they did not change too much (about 15% like the Focals). Yet this change effected a change in box volume from 12 to 15 liters (if I was to keep system Qts to 0.6 for a sealed box).
makes me wonder.
did you check fs and qts?
if the basic t/s specs are so far off how do we rely on Bl, Mms, Cms, etc?
i find even the better guys (Audax, Focal, SS, Vifa etc.) to be off. 10% is a big variation, 40% is intolerable.
maybe we should send some of our 18 stone moderators to talk to the manufactuers
did you check fs and qts?
if the basic t/s specs are so far off how do we rely on Bl, Mms, Cms, etc?
i find even the better guys (Audax, Focal, SS, Vifa etc.) to be off. 10% is a big variation, 40% is intolerable.
maybe we should send some of our 18 stone moderators to talk to the manufactuers
I am using the Peerless 850102 for my Arro Clone.
Manufacturer spec:
Fs: 74.2
Qms: 2.41
Qes: 0.52
Qts: 0.43
Vas: 3.4
My measurements:
(after 100 hours of break in and a 5 trial for each driver).
Fs: 102
Qms: 3.42
Qes: 0.61
Qts: 0.52
Vas: 0.069
This give you an idea on how much the specs can differ.
Manufacturer spec:
Fs: 74.2
Qms: 2.41
Qes: 0.52
Qts: 0.43
Vas: 3.4
My measurements:
(after 100 hours of break in and a 5 trial for each driver).
Fs: 102
Qms: 3.42
Qes: 0.61
Qts: 0.52
Vas: 0.069
This give you an idea on how much the specs can differ.
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