QTS value way off when measured

creutz · 5th September 2011, 02:18 AM

Hi guys,

I built a set of speaker boxes for 5" Vifa C13WG-19-08 drivers a while ago. I based my vented boxes on the manufacturer specs. Qts on these woofers were suppose to be 0.39. Well recently I purchased the WT3 woofer tester from parts Express to see how accurate these specs are. Well unless I'm doing something wrong they are way off. I have 4 drivers and all of them measured qts around 0.60. Any chance I'm doing something wrong whne I measure or is this a normal deviation?

Since I already built vented boxes for these drivers witha volume of 0.42 cubic feet I'm unsure how to propoerly work around this problem. Can I successfully install drivers with such a high qts value in a vented system, or am I better of finding new drivers?

Thankful for help

Conrad Hoffman · 5th September 2011, 02:34 AM

It seems like something's wrong, or the drivers are still new and stiff. Manufacturers numbers are usually way better than that, but they should be measuring them after some break-in. You should too! What's the published Fs value and what did you measure?

a.wayne · 5th September 2011, 02:45 AM

Advertised qts is always lower than measured .......

creutz · 5th September 2011, 02:53 AM

Advertized fs is 55 Hz, and I've been measuring around 77 Hz on all 4 drivers.

norman bates · 5th September 2011, 03:20 AM

The fs seems about right, but it may drop as the driver breaks in (suspension softens through use), or it may not.

The qts, it may be that high. The audio nirvana has a qts listed at .25 but measures out at .4 and .41

Norman

"This one goes to 11."

Michael Bean · 03:25 AM

Are the drivers well broken in? If not, it can affect the results and can cause deviation from specs quite a bit in some cases. Also it might be caused by different measurment methods, and/or measurement accuracy. Sometimes manufacturers rate thier products rather optimistically. It's a good sign that all are consistant with each other.
Mike

creutz · 5th September 2011, 03:31 AM

Thanks for the help guys,...

The drivers are not broken in. They have actually been laying around for a couple of years and I just recently got them out to measure them. I have tried several times to measure them with very similar results. I just wasn't sure if I was doing something wrong using the WT3 woofer tester or if the specs could really be that much off from what the manufacturer states...

And from what I understand, if these results are true, these drivers are no longer good to be used in a vented system.

Michael Bean · 5th September 2011, 03:58 AM

Get them well broken in and test again, the results will probably be better.

Mike

creutz · 5th September 2011, 04:53 AM

What would be the best way to break-in the speakers?

a.wayne · 5th September 2011, 05:18 AM

25 hz sine wave at 50 % xmax for about 24 hrs ....

5th September 2011, 02:18 AM	#1
creutz diyAudio Member Join Date: Sep 2011	QTS value way off when measured Hi guys, I built a set of speaker boxes for 5" Vifa C13WG-19-08 drivers a while ago. I based my vented boxes on the manufacturer specs. Qts on these woofers were suppose to be 0.39. Well recently I purchased the WT3 woofer tester from parts Express to see how accurate these specs are. Well unless I'm doing something wrong they are way off. I have 4 drivers and all of them measured qts around 0.60. Any chance I'm doing something wrong whne I measure or is this a normal deviation? Since I already built vented boxes for these drivers witha volume of 0.42 cubic feet I'm unsure how to propoerly work around this problem. Can I successfully install drivers with such a high qts value in a vented system, or am I better of finding new drivers? Thankful for help

5th September 2011, 02:34 AM	#2
Conrad Hoffman diyAudio Member Join Date: Mar 2007 Location: Canandaigua, NY USA	It seems like something's wrong, or the drivers are still new and stiff. Manufacturers numbers are usually way better than that, but they should be measuring them after some break-in. You should too! What's the published Fs value and what did you measure? __________________ I used to be an audiophool like you but then I took an arrow to the knee.

5th September 2011, 03:21 AM	#6
Michael Bean diyAudio Member Join Date: Sep 2004 Location: Minneapolis, Minnesota, USA	Are the drivers well broken in? If not, it can affect the results and can cause deviation from specs quite a bit in some cases. Also it might be caused by different measurment methods, and/or measurement accuracy. Sometimes manufacturers rate thier products rather optimistically. It's a good sign that all are consistant with each other. Mike Last edited by Michael Bean; 5th September 2011 at 03:25 AM.

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5th September 2011, 02:45 AM	#3
a.wayne diyAudio Member Join Date: May 2008 Location: Front Row Center	Advertised qts is always lower than measured .......

5th September 2011, 02:53 AM	#4
creutz diyAudio Member Join Date: Sep 2011	Advertized fs is 55 Hz, and I've been measuring around 77 Hz on all 4 drivers.

5th September 2011, 03:20 AM	#5
norman bates diyAudio Member Join Date: Nov 2003 Location: iowa	The fs seems about right, but it may drop as the driver breaks in (suspension softens through use), or it may not. The qts, it may be that high. The audio nirvana has a qts listed at .25 but measures out at .4 and .41 Norman "This one goes to 11."

5th September 2011, 03:31 AM	#7
creutz diyAudio Member Join Date: Sep 2011	Thanks for the help guys,... The drivers are not broken in. They have actually been laying around for a couple of years and I just recently got them out to measure them. I have tried several times to measure them with very similar results. I just wasn't sure if I was doing something wrong using the WT3 woofer tester or if the specs could really be that much off from what the manufacturer states... And from what I understand, if these results are true, these drivers are no longer good to be used in a vented system.

5th September 2011, 03:58 AM	#8
Michael Bean diyAudio Member Join Date: Sep 2004 Location: Minneapolis, Minnesota, USA	Get them well broken in and test again, the results will probably be better. Mike

5th September 2011, 04:53 AM	#9
creutz diyAudio Member Join Date: Sep 2011	What would be the best way to break-in the speakers?

5th September 2011, 05:18 AM	#10
a.wayne diyAudio Member Join Date: May 2008 Location: Front Row Center	25 hz sine wave at 50 % xmax for about 24 hrs ....

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