So-called back chambers necessary for mid-range drivers?

Suzuki

Suzuki

jl1dca
Hello, folks....
My speaker is originally made composition with Hi-Vi's 2 and 1/2-inch full-range and 7-inch woofer in a middle-sized box for JBL J216 in original use. Do I have to have built a chamber behind the Hi-Vi to shelter it from the sound from the woofer?:scratch2: I'll greatly appreciate your expertise and insights. Cross-over is 700hz.
Thank you in advance.

Taihei
 
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For sure. The pressure inside the cabinet rises and falls as the woofer moves, which will interfere with the midrange. At high volumes, it can even damage its suspension.
 
They are highly recommended since they protect your midrange from the pressure the woofer creates in a box and keeps the woofers sound waves from distorting your midrange motion.

That said I have seen lots of speakers, some use them most don't.
 
I would say yes. The back wave from the woofer will interfere with the smaller driver in a negative way.
 
Thank you for sharing your idea. Diaphragm's area isn't large and box capacitance is fairly large, so I thought the stress mid-range will receive can be ignored. Is the back chamber usually the case with 3way famous speaker systems?
 
Suzuki said:
Thank you for sharing your idea. Diaphragm's area isn't large and box capacitance is fairly large, so I thought the stress mid-range will receive can be ignored. Is the back chamber usually the case with 3way famous speaker systems?
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The air inside still vibrates with the back wave from the woofer, and the pressure changes aren't insignificant.

Every single half-decent 3 way speaker has a chamber to isolate the midrange (and tweeter if it's got an open back!).

Even cheapo rack system speakers have either a closed back midrange or a plastic cup over the back.
 
Bozak used a thin plastic black bowl. Screwed to the front, betwwen the driver and the basket is damping material.

bozakinside1.jpg
 
MunkeyQ said:
The air inside still vibrates with the back wave from the woofer, and the pressure changes aren't insignificant.

Every single half-decent 3 way speaker has a chamber to isolate the midrange (and tweeter if it's got an open back!).

Even cheapo rack system speakers have either a closed back midrange or a plastic cup over the back.
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I see. I would have to assemble a wooden cubic cup for chambers...:smoke:
Thank you, all of you.

Taihei
 
Suzuki said:
I see. I would have to assemble a wooden cubic cup for chambers...:smoke:
Thank you, all of you.

Taihei
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Plastic food bowls work well - pet ones are best as they tend to be thicker. Find one that's fairly deep with a wide rim, drill holes in it and screw it to the back of the baffle. Only needs to be a litre or so, but the volume isn't important as long as you're not running the midrange too low...below about 600hz and you should model it as a woofer and calculate the volume to avoid losing out on the low-end response.
 
MunkeyQ said:
Plastic food bowls work well - pet ones are best as they tend to be thicker. Find one that's fairly deep with a wide rim, drill holes in it and screw it to the back of the baffle. Only needs to be a litre or so, but the volume isn't important as long as you're not running the midrange too low...below about 600hz and you should model it as a woofer and calculate the volume to avoid losing out on the low-end response.
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Thanks....But the problem is buffle is fixed to the box, not being removable.
I think of fixing them with adhesive. :scratch2: Rear board of the box has four screws on it. Is it removal???
 
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I have a pair of B&W DM603s. They're vented. Twice. One vent for the woofer's chamber and another vent for the midrange/tweeter chamber (though, because of the tube-loaded tweeter, I don't know if it's affected by the mid-range's vibrations).
 
MunkeyQ said:
For sure. The pressure inside the cabinet rises and falls as the woofer moves, which will interfere with the midrange. At high volumes, it can even damage its suspension.
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Highly agreed. Acoustically isolating the midrange as as well will reduce modulation distortion caused by the woofer.
 
Hi,

In this case, with scant driver details I'd say yes it is needed.

As suggested by others all sorts of things can be pressed into
service as a back chamber, not the least something designed
to do the job in the first place, but not very common now.

M13IC.jpg


rgds, sreten.
 
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