Midrange Enclosure Volume

[lotuss79]

Could anyone tell me the disadvantages of using a significantly larger enclosure for a midrange driver then is technically ideal for that driver?
Thinking about mounting a midrange almost flush with a tweeter and without a space to divide the two drivers i would be looking at a volume of more then twice what is called for.
Any explanation of why or if the ideal mid enclosure volume should be adhered to would be greatly appreciated.
Thanks

 

[LaMa]

If you intend to high pass the mid driver much higher in frequency than the box tuning, it does not influence the results too much. The new internal dimensions will lead to better/worse damping of the back wave in the enclosure (depending on the design choices). And you are wasting some internal volume .

If on the other hand the acoustic roll of the original box volume starts close to the xo frequency than you have to adapt the XO to account for the roll of.

 

[tinitus]

A midrange chamber is mostly closed, so it wont matter much

If you had planned on having the mid roll off by itself it would matter

But with a highpass crossover, the smoother and more extended(shallow?) rolloff of a bigger box ought to be in your favour

 

[lotuss79]

Thanks for the replies.
I should have been more specific about the setup in the original post.
It will be a 3way design in a sealed box enclosure. The 5" mid will be paired with a 12" woofer and crossed at 300Hz. (and 2400Hz on the high end).
The mid driver chassis is not enclosed in the back, its fully open, if that is what you were referring to tinitus.
In that scenario, could i leave the mid in a rather large sealed enclosure with the tweeter or would i need to chamber the midrange by itself in an enclosure of roughly .08 cu.ft. as is specified for.
Thanks again,

 

[tinitus]

In that scenario, could i leave the mid in a rather large sealed enclosure with the tweeter or would i need to chamber the midrange by itself in an enclosure of roughly .08 cu.ft. as is specified for.
Thanks again,

I dont understand why you say it will need to be big

You should be able to make it very small
Just make it as flat/shallow as the magnet permits

But it will be a good thing to make some space/air around the driver, so it can breathe freely
A less thick mounting baffle helps too
Best you can do is to mount the mid in sheet of aluminium plate, 5-6mm will do, and easy to cut with a jigsaw, but use proper protection, especially fore your eyes

Time fore more information/specs/pictures of that mid

 

[lotuss79]

I say it would be big because i have the depth for the cabinet already at 10"
I guess what im asking is whether the recommended enclosure volume is as important for midrange drivers as it is for bass drivers.

 

[tinitus]

I say it would be big because i have the depth for the cabinet already at 10"

You keep talking in riddles

Do you have box already built, or have you just chosen the depth of a box you are going to build
If not built yet, its no problem to make a smaller mid box inside of it
If the box is readily built, its no problem either to cut out a piece and make the small mid chamber

 

[Pano]

I see what you are asking - your volume is set by your cabinet design. So you have more volume that you need for the mid.

Unfortunately I don't know if "too big" a chamber is bad.
Probably not, as open back speakers do OK. But a box is another matter.

Someone here will know, for sure.

 

[Moondog55]

If you have the T/S parameters for the mid driver just plug the numbers into a box program and look at the results, aim for a Qtc of between 0.8 and 0.55, anything bigger than critically damped ( Qtc 0.55 ) is probably too big and smaller than 0.8 to small.

Crossing at 300 it is possible that the mid drivers is working partly in its piston range, if the box is too big, then excursion limits may be exceeded at high power, probably not a problem if you are using steep slopes but could well be if you are using first order XO.

Sorry if the explanation is a little hazy but that is my understanding of the matter.