Separate Enclosure for Midrange

Njoy-Music

Njoy-Music

Old Time Rock & Roll
While reading the thread on a lucky Ak member finding a good set of KLH 5's, it was mentioned they have separate enclosure for the midrange. That got me to wondering as other speaker companies seem to make much of this and how it keeps the bass from in a sense muddying up the bass and vice versa. Also the tweeter of course but here I'm more concerned about the mids.

I have a pair of RSb's and as much as I like them, the mids are not the best. And yes when you press the bass driver it moves the mids as well so I'm getting a good seal all around. However in that thread it was mentioned if it does that it means the mid is acting as a passive radiator for the bass and creating all sorts of distortion in the mid driver. Now it's got me to thinking maybe I should figure out a way to isolate the midrange within the enclosure to clean it up. By using an EMIT that's already pretty much sealed away from the rest of the drivers, I doubt that's an issue.

But now it's got me wondering about that midrange. And if it would be a good idea, how do I go about finding out what would work best? I can't find much info on it so far and I thought maybe a few of the experts on here might be able to give me some thoughts, be willing to discuss options or point me in a direction to look.

I'd love to read up on something to get the why as well. Even though I've been around stereo for 40 some years, I never really got that technical with it and now I'm feeling that lack.

Any help would be greatly appreciated! Thanks!
 
Register to hide this ad
It's funny that there can be a system out there with a midrange loaded with the same enclosure as the LF unit.

Each cone speaker needs a load to work with an tune it. The load is in the form of an enclosure and it may be a sealed one, one with a vent or a more complex design.

Typically midrange speakers are loaded with a sealed enclosure that is mounted inside the main enclosure, behind the midrange.

Each speaker has it's own optimum load (aka enclosure size) and typically, the larger the driver, the larger the enclosure. Hence, the midrange needs a moderately small volume, in the range of 3-10lt.

In order to accurately calculate the optimum enclosure volume, you need to have the Thiele-Small parameters for the driver and then either use the equations or a program like WinISD to enter the parameters, chose the cutoff frequency and have the program calculate the volume for you.

For sealed enclosures, the sensitivity to an incorrect enclosure volume is the smallest of all systems. Therefore, even if you aim for a 5lt enclosure without knowing anything about the driver, it won't be too wrong.

Now, as to modifying a complete system, considering it was designed without a sub-enclosure for the midrange, it a bit tougher. The isolation of the midrange will affect the tonal balance in ways you can't predict.

Now, since I'm guessing you are refering to Infinity speakers, I'm shocked that the midrange is left there in the same enclosure as the woofer. I'd try to check (remove the driver) if there's a sub-enclosure behind it. It's more likely that there's a leak in the construction than there's nothing there. Even a small leak would cause the behavior you describe.
 
PS. And with tweeters, as almost all of them are sealed from the back (they mainly are dome drivers and the few milliliters of airspace behind the dome are all they need) there's no such thing as a loading enclosure for a tweeter.
 
The load is in the form of an enclosure and it may be a sealed one, one with a vent or a more complex design.
Click to expand...
Respectfully, and mostly for the sake of semantics, the "load" is ALWAYS an air mass.
 
Thanks for the info. I've had the speakers apart to refoam the woofers when I got them as the foam had rotted away. I also had to reseal ALL the drivers because all the gaskets were in rough shape. And no there is no sub enclosure just for the mids. It's a 5" poly midrange. I think I'm gonna have to see about making some kind of enclosure for it and test it. Nothing too permanent for now but something that will me at least do a good test of it. And since it's not a large speaker, a 5lt test box would fill half the speaker so that's out. I guess I'll have to read up on this, educate myself as best I can and go from there.

Thanks all for the info!
 
Just a suggestion, but maybe look for a piece of plastic drain pipe that is large enough to fit over the midrange, then cover the back of it with anything solid, even 1/4 inch plywood. Caulk it up so it's air tight. Even if not perfect, it will be an improvement.

I've always been a bit leery of Infinity. Back around 1970 when McIntosh introduced their first speaker, the ML-1, they went around the country doing demonstrations. Gordon Gow mentioned that they had discovered that insulation used in some Infinity speakers was highly flammable and when they reported that back to Infinity, Infinity was not interested in hearing about it. I have no reason to believe that this was not a true story and if it is, I would not support such a company.
 
Last edited:
Thank You for that little bit of info fred_soop. My original idea and was to do just such an piece of pipe. It's simple and easy to adjust to fit, will caulk up fine and be removable it does seem to do the trick and I want to do something more permanent. And those pieces of pipe have also been used for some simple DIY speaker applications already, a little tweaking and it might be something to stick with. I'll be doing some exploring and looking at all sorts of places for ideas but there's some good food for thought here. Thank You for that!

And the fact that Mac and Infinity were at odds with each other is a well known but not so documented mutual sneer fest.
 
Maybe some one removed the enclosures ?

Or put open back midranges in your speakers
 
Did anyone ever come up with the proper midrange enclosure volume? I am building a set of cabinets from scratch for the RSb’s and don’t have an original cabinet to measure. When looking at images, there does appear to be a separate round enclosure for the mids attached to the front baffle.
 
You must log in or register to reply here.
Back
Top Bottom