Z Measurements on Modified Woofer (De-cap and Phase Plug)

CLS · 18th July 2009, 04:13 AM

Driver: Eminence Sigma Pro 18 (old version)

Original (free air):

(I don't remember if this was the real 'original', or had been coated with PVA glue...

)

With dust cap being cut (free air):

With phase plug:

I'm curious about the hickup centered at about 160Hz. Why does a phase plug add this? (at so low)

It's smoother higher up, though.

CLS · 18th July 2009, 04:35 AM

Original driver on baffle (90cm W x 120cm H and lifted from floor by 6cm ):

De-cap'ed driver on the same baffle as above:

Driver with phase plug on another baffle (55cm W x 65cmH on floor):

Sorry for not using the same baffle (I dumped the old one already!).

It seems the baffle loads the driver with some more aire and slightly drop the fs. Also, it added some more irregularities across the midbass (comparing with the free air responses).

And it looks like the de-cap'ed one is overall the smoothest. The phase plug, sigh ~ ....

CLS · 18th July 2009, 04:42 AM

I tried to keep those numbers readable.

And here is 2 drivers (with phase plugs) on baffle, horrible:

T-bass circuit tames those peaks somewhat:

And of course it drops the overall impedance.

This is what it looks:

MisterTwister · 20th July 2009, 04:26 AM

I think your phase plug is touching voice coil former.

CLS · 20th July 2009, 04:50 AM

LOL, No!

It looks very close, but no. They are playing very well without any rubbing noise.

Normally the cone moves so little. And there'd be no physical contacts even by pushing the cone (by hand) and make it move as far as possible.

Would it be the softened suround and spider? I applied some silicon oil on them, thus less damping, maybe....

No, wait, that's well before the phase plug. If that'd be the case, then that peak should also be seen in the previous stages. Hmmm.....

MisterTwister · 20th July 2009, 04:07 PM

are your phase plugs made out of non magnetic metal?

CLS · 21st July 2009, 01:31 AM

Billet aluminum.

MisterTwister · 21st July 2009, 02:58 AM

the last cause I could think of is reflection from back wall.

CLS · 21st July 2009, 03:56 AM

But it's also there on the free air measurement!

Maybe it was not 'free air' enough? I put it on my knee and facing upward. The only relfection source was the top surface of my thigh. Would it be? No....

I don't have any other convenient method for this 9kg woofer

Right now the ones on the center sub are playing OK, but they are LP xover'ed at 40Hz. I can't see any peak or dip on the FR around here, and they sound very good.

The main baffles are not running yet. I plan to run them up to about 200Hz, so this 'issue' may appear on them. We'll see.

18th July 2009, 04:13 AM	#1
CLS diyAudio Member Join Date: Jun 2005 Location: Taiwan	Z Measurements on Modified Woofer (De-cap and Phase Plug) Driver: Eminence Sigma Pro 18 (old version) Original (free air): (I don't remember if this was the real 'original', or had been coated with PVA glue... ) With dust cap being cut (free air): With phase plug: I'm curious about the hickup centered at about 160Hz. Why does a phase plug add this? (at so low) It's smoother higher up, though.

18th July 2009, 04:35 AM	#2
CLS diyAudio Member Join Date: Jun 2005 Location: Taiwan	On baffle Original driver on baffle (90cm W x 120cm H and lifted from floor by 6cm ): De-cap'ed driver on the same baffle as above: Driver with phase plug on another baffle (55cm W x 65cmH on floor): Sorry for not using the same baffle (I dumped the old one already!). It seems the baffle loads the driver with some more aire and slightly drop the fs. Also, it added some more irregularities across the midbass (comparing with the free air responses). And it looks like the de-cap'ed one is overall the smoothest. The phase plug, sigh ~ ....

18th July 2009, 04:42 AM	#3
CLS diyAudio Member Join Date: Jun 2005 Location: Taiwan	Oh, sorry for the big pics.... I tried to keep those numbers readable. And here is 2 drivers (with phase plugs) on baffle, horrible: T-bass circuit tames those peaks somewhat: And of course it drops the overall impedance. This is what it looks:

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Phase Plug, how does it works?	Antonio	Multi-Way	5	17th June 2009 12:05 PM
Modified Windows Media Player Plug-in	pweaudiotech	Everything Else	0	8th April 2008 06:34 PM
Phase Plug Dims ?	valveitude	Full Range	0	16th November 2006 03:10 PM
Anywhere to buy off-the shelf phase plug?	bcherry	Full Range	6	19th October 2005 07:22 AM


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

20th July 2009, 04:26 AM	#4
MisterTwister diyAudio Member Join Date: Feb 2006 Location: usa Blog Entries: 1	I think your phase plug is touching voice coil former.

20th July 2009, 04:50 AM	#5
CLS diyAudio Member Join Date: Jun 2005 Location: Taiwan	LOL, No! It looks very close, but no. They are playing very well without any rubbing noise. Normally the cone moves so little. And there'd be no physical contacts even by pushing the cone (by hand) and make it move as far as possible. Would it be the softened suround and spider? I applied some silicon oil on them, thus less damping, maybe.... No, wait, that's well before the phase plug. If that'd be the case, then that peak should also be seen in the previous stages. Hmmm.....

20th July 2009, 04:07 PM	#6
MisterTwister diyAudio Member Join Date: Feb 2006 Location: usa Blog Entries: 1	are your phase plugs made out of non magnetic metal?

21st July 2009, 01:31 AM	#7
CLS diyAudio Member Join Date: Jun 2005 Location: Taiwan	Billet aluminum.

21st July 2009, 02:58 AM	#8
MisterTwister diyAudio Member Join Date: Feb 2006 Location: usa Blog Entries: 1	the last cause I could think of is reflection from back wall.

21st July 2009, 03:56 AM	#9
CLS diyAudio Member Join Date: Jun 2005 Location: Taiwan	But it's also there on the free air measurement! Maybe it was not 'free air' enough? I put it on my knee and facing upward. The only relfection source was the top surface of my thigh. Would it be? No.... I don't have any other convenient method for this 9kg woofer Right now the ones on the center sub are playing OK, but they are LP xover'ed at 40Hz. I can't see any peak or dip on the FR around here, and they sound very good. The main baffles are not running yet. I plan to run them up to about 200Hz, so this 'issue' may appear on them. We'll see.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read