# thoughts for a inwall speaker



## bigdawg56 (Nov 1, 2008)

ok this is what im thinking of trying a zalph audio Bargain Aluminum MTM design but in a cabinet 14.5 x 55 x 3.5 i know because of the box shape it may sound different so any help or idea would be appreciated. this will be mounted between the stud and covered with drywall.


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## JCD (Apr 20, 2006)

A few things:

I don't think 3.5" is going to be deep enough -- I can't imagine that would be enough space for the back of the speaker or the backwave from the driver
You have different volumes. It looks like he's got about twice the volume of what you're shooting for
His crossover has a baffle step built in to it which is dependent on the actual width of the baffle. If this is going to be built in to a wall, you would have a HUGE baffle compared to the 9" I see on the design

If you're going to go with in-walls, I'm not sure what drivers would be available or work well.


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## bigdawg56 (Nov 1, 2008)

by my calculations it should be a little over 1 cubic ft and that is what zalph was using in his closed design. the mounting depth of the woofer is 3inches witch by my design would leave about 3/4in from the back of the magnet to the back of the enclosure, i dont know if this would be enough but i thought it might be worth a try. im not sure what do about the baffle step built into the cross over. i guess im wonder could it be modified to compensate for the wider baffle?


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## JCD (Apr 20, 2006)

bigdawg56 said:


> by my calculations it should be a little over 1 cubic ft and that is what zalph was using in his closed design.


Duh! Totally missed the closed design. 
Internal dimensions are 7.5x20.5x11.75 = 1807 cu in, or ~1 cu ft
Your dimensions are 14.5 x 55 x 3.5 = 2791 cu in, or ~1.6 cu ft




> the mounting depth of the woofer is 3inches witch by my design would leave about 3/4in from the back of the magnet to the back of the enclosure, i dont know if this would be enough but i thought it might be worth a try.


That has been a question I don't think I've ever gotten a satisfactory answer for. However, I don't think 3/4" would be enough for a typical driver. I'd consider e-mailing them to see how much clearance you'd need -- [email protected].





> im not sure what do about the baffle step built into the cross over. i guess im wonder could it be modified to compensate for the wider baffle?


It can definitely be modified, but crossover design is tricky. He mentions increasing L2 and R6 to get _more_ BSC, so using less may be a good start.. This one will just take some experimenting.

Good luck and I look forward to your future build.


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## bigdawg56 (Nov 1, 2008)

thank you for your input if you do email them please post it and i screwed up i should have stated the the demensions i gave were external not internal sorry


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## DrWho (Sep 27, 2006)

3/4" is more then enough if it's not using a vented pole piece. When you've got a vent, you should be at least one vent diameter away.


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## bigdawg56 (Nov 1, 2008)

any recommendations on decrease L2 and R6 to eliminate the bsc


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## drf (Oct 22, 2006)

Given the complexity/uniqueness?? of your project I would suggest removing the BSC altogether and recalculating the other components to allow for the difference in design. After building the unit and actually installing in your wall you'll have a better idea how much BSC is needed, if any. Some dimensions of your wall/room might also help us better understand the circumstances.


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## bigdawg56 (Nov 1, 2008)

its 18' X 35' would you think that L2 and R6 are only used for bsc and if you dont mind first attempt at a crossover what would i need to recalculate after removing the bsc?


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## drf (Oct 22, 2006)

O.K, I made the last post before i had a look at the crossover on zaphs site. That BSC is part of a standard crossover allignment. (I thought the BSC was independant of the xover) If you reduce L2 you will change the crossover point of the woofers (not highly recomended). R6 is primarily there to antenuate the tweeter so it doesn't overpower the woofers. Given that it such a simple crossover I would build it as shown and then do some fr measurements before adjusting or modifying anything.


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## bigdawg56 (Nov 1, 2008)

Thanks for your input i will be starting the build soon and then im sure ill be reposting with more questions.


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