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My SMT212 CP755TI / SN12B

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wafflesomd View Drop Down
Young Croc
Young Croc


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Post Options Post Options   Thanks (0) Thanks(0)   Quote wafflesomd Quote  Post ReplyReply Direct Link To This Post Posted: 06 November 2008 at 8:29am
Originally posted by LunchieTey LunchieTey wrote:

Originally posted by wafflesomd wafflesomd wrote:

Did you ever get around to measuring them and checking for peaks and dips.

I may just be ditching these cabinets and going for something else.  It seems like there will always some annoying resonances just based on the cabinets design.


It may just be your choice of speaker, you said you tried it with drivers that have a qts of 1.3 and the deltas(if you have them now) have a big response peak and also don't like small boxes! Maybe if you decide to bin them, open up the extra space behind the compression driver?Or put in the ports(hole sawWink) might lower the resonant frequency of the cab as you didn't port yours(high q alignment with the deltas will give you a big resonance at fb) Also try stuffing the rear chamber if you stay sealed.

I do plan on porting them.

I was talking to a friend of mine, and he stated that buy design, the cabinet will resonate at 400-500hrtz.  I guess I'm going to hold out until I get some proper drivers.  

I'd like to see some measurements with some Delta's, or other drivers.  I really can't stand resonance at all.  

I havn't purchased any new drivers yet.   Seems like the only driver that has been proven to work well is the p.audio sn12b.  That driver is far to expensive.  I can't find another driver with even close specs.  

It seems like the x12 might be a better solution for me.  I'm not looking to spend huge amounts of money on drivers.


Edited by wafflesomd - 06 November 2008 at 8:32am
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Old Croc
Old Croc


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tekasis Quote  Post ReplyReply Direct Link To This Post Posted: 06 November 2008 at 10:01am
Originally posted by wafflesomd wafflesomd wrote:

 I havn't purchased any new drivers yet.   Seems like the only driver that has been proven to work well is the p.audio sn12b.  That driver is far to expensive.  
 
I can't find another driver with even close specs.  

I'm not looking to spend huge amounts of money on drivers.
 
You tried looking at the Celestion Truvox series ?
 
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wafflesomd View Drop Down
Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wafflesomd Quote  Post ReplyReply Direct Link To This Post Posted: 06 November 2008 at 10:22am
I'm not sure how well those would work.  The specs are close the Emeinence beta and delta.
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Deadbeat View Drop Down
Old Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Deadbeat Quote  Post ReplyReply Direct Link To This Post Posted: 06 November 2008 at 8:37pm
wafflesomd - you also need to look at polars, FR graphs, etc to determine breakups and beaming and is essential in selecting xover point. This gives you a clearer picture.
'

I was talking to a friend of mine, and he stated that buy design, the cabinet will resonate at 400-500hrtz.  I guess I'm going to hold out until I get some proper drivers.  

I'd like to see some measurements with some Delta's, or other drivers.  I really can't stand resonance at all.  '

What was he talking about? Any reasoning you could enlighten us with?


Edited by Deadbeat - 06 November 2008 at 8:38pm
Away on extended leave.
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wafflesomd View Drop Down
Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wafflesomd Quote  Post ReplyReply Direct Link To This Post Posted: 06 November 2008 at 8:43pm
He based this on the fact that the bottom, and piece F are parrellel and don't expand.   I probably said that wrong.

Do emeinence have polar measurements?


Edited by wafflesomd - 06 November 2008 at 8:49pm
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Old Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Deadbeat Quote  Post ReplyReply Direct Link To This Post Posted: 06 November 2008 at 8:49pm
Haha. In that case all our speakers are flawed.

Anyway. Tell your friend that he is right in noticing standing waves in a cabinet caused by parallel sides.

The distance from Piece F to the bottom is 680mm. This is the wavelength of 500hz - he's done the math right. Unfortunately, the driver's chassis and cone are in the way of nary a standing wave Wink. Besides - any standing waves formed would be chased away if you stuffed and lined the boxes properly when finished.
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wafflesomd View Drop Down
Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wafflesomd Quote  Post ReplyReply Direct Link To This Post Posted: 06 November 2008 at 8:51pm
Neato.  

So how would I go about stuffing and lining these?
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Old Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Deadbeat Quote  Post ReplyReply Direct Link To This Post Posted: 06 November 2008 at 8:54pm
An average 12" begins to start being directive (beaming) at 1k2.
Most manufacturers will give you polar plots at several frequencies. I don't think eminence do.

If you wanted to be absolutely sure any standing waves were absorbed - I'd staple a thin layer of closed cell to the top and bottom of the chamber.



Edited by Deadbeat - 06 November 2008 at 8:55pm
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wafflesomd View Drop Down
Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wafflesomd Quote  Post ReplyReply Direct Link To This Post Posted: 06 November 2008 at 8:58pm
The rear chamber, the waveguided section, both?  
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Old Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Deadbeat Quote  Post ReplyReply Direct Link To This Post Posted: 06 November 2008 at 8:59pm
Just the rear chamber where your friend is mortally afraid of resonance. Top and bottom. Closed cell. Thin layer. Staples.
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wafflesomd View Drop Down
Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wafflesomd Quote  Post ReplyReply Direct Link To This Post Posted: 06 November 2008 at 9:04pm
Thanks for the help.

Now it just comes down to driver selection.

Using a 3 way design would be the most cost effective thing to do.  Most 2" are very, very expensive, and the horns are as well.  


Edited by wafflesomd - 06 November 2008 at 9:09pm
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Old Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Deadbeat Quote  Post ReplyReply Direct Link To This Post Posted: 06 November 2008 at 9:12pm
What's your budget for the whole lot?
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