to port mid enclouser or not?

dallaire · 23rd December 2007, 09:59 PM

Was wondering, for my new three way center that has four inch mids and six and a half inch woofers, that I would like to cross at 300hz from six-four incher. I meassured a new sealed tube encluser that was mounted to the back side of finished dimension front baffle, it measured very nice in terms of flatness "plus or minus 1.5db" from 400-2.5k. I was thinking of porting the mid enclouser per "peerless" directions for loading if used in a small two way system "I assume", would this effect the performance of the mid in other ways that I may not be considering? I think it would help low end extention to reach my goal of 300hz cross point nice and flat, however I'm not sure that it would screw up performance at other frequencies. All crossovers are 24db per and all electronic. Any thoughts?
dallaire

jupiterjune · 24th December 2007, 01:45 AM

Dallaire-
What 4" mids are you using?

In general, I think the ports would be a no-no. I believe they would be out of phase acoustically at some point with the woofer, and you would get a suckout, or maybe just 'fuzzy' bass. But then, I never even thought to try it. Maybe someone has done it and it works -- I would be interested to hear.

JJ

69stingray · 24th December 2007, 02:21 AM

Model it in Unibox with the 300-Hz high-pass filter on the mid. You may get more power handling out of the port OR, if the port is tuned low enough, may have no effect at all. Be sure to look at the port resonances also.

On a small 4" driver, the port may not be a bad idea. 4" drivers have increasing distortion lower in the freq., so a port may make it easier to blend with a larger woofer that you don't want to play as high.

Some of the new Polk speakers have ported midranges, so it is not unheard of.

dallaire · 24th December 2007, 01:08 PM

Thanks guys, I will explore this with a test box, however the phase problem mentioned, is a good point. I can get rollin to match other frequencies at about 400hz or about 3db down at 300hz. The only reason I wanted to go with 300hz was to not cross in the vocal range, even though the more I read on the subject, it seems to extend much lower anyway! I got the original idea from "Rod Elliots" ESP Audio web site, stating cross if you can no higher than 300hz.
SPEAKERS:
PEERLESS 6.5 HDS NOMEX WOOFERS (2)
PEERLESS 4.0 HDS PPB MIDS (2)
SCAN SPEAK 9500 1 INCH DOME (1)

This is for center channel
dallaire

23rd December 2007, 09:59 PM	#1
dallaire diyAudio Member Join Date: Nov 2007	to port mid enclouser or not? Was wondering, for my new three way center that has four inch mids and six and a half inch woofers, that I would like to cross at 300hz from six-four incher. I meassured a new sealed tube encluser that was mounted to the back side of finished dimension front baffle, it measured very nice in terms of flatness "plus or minus 1.5db" from 400-2.5k. I was thinking of porting the mid enclouser per "peerless" directions for loading if used in a small two way system "I assume", would this effect the performance of the mid in other ways that I may not be considering? I think it would help low end extention to reach my goal of 300hz cross point nice and flat, however I'm not sure that it would screw up performance at other frequencies. All crossovers are 24db per and all electronic. Any thoughts? dallaire

24th December 2007, 02:21 AM	#3
69stingray diyAudio Member Join Date: Apr 2005 Location: NH	Model it in Unibox with the 300-Hz high-pass filter on the mid. You may get more power handling out of the port OR, if the port is tuned low enough, may have no effect at all. Be sure to look at the port resonances also. On a small 4" driver, the port may not be a bad idea. 4" drivers have increasing distortion lower in the freq., so a port may make it easier to blend with a larger woofer that you don't want to play as high. Some of the new Polk speakers have ported midranges, so it is not unheard of. __________________ Audio DIY Page FOLLOWMY529.COM - Subscribe and follow the performance of my daughter's 529 College Saving Account.

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24th December 2007, 01:45 AM	#2
jupiterjune diyAudio Member Join Date: Nov 2006	Dallaire- What 4" mids are you using? In general, I think the ports would be a no-no. I believe they would be out of phase acoustically at some point with the woofer, and you would get a suckout, or maybe just 'fuzzy' bass. But then, I never even thought to try it. Maybe someone has done it and it works -- I would be interested to hear. JJ

24th December 2007, 01:08 PM	#4
dallaire diyAudio Member Join Date: Nov 2007	Thanks guys, I will explore this with a test box, however the phase problem mentioned, is a good point. I can get rollin to match other frequencies at about 400hz or about 3db down at 300hz. The only reason I wanted to go with 300hz was to not cross in the vocal range, even though the more I read on the subject, it seems to extend much lower anyway! I got the original idea from "Rod Elliots" ESP Audio web site, stating cross if you can no higher than 300hz. SPEAKERS: PEERLESS 6.5 HDS NOMEX WOOFERS (2) PEERLESS 4.0 HDS PPB MIDS (2) SCAN SPEAK 9500 1 INCH DOME (1) This is for center channel dallaire

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