Sub crossover freq for MMGs?

[Mike Anderson]

^ Thanks.

I should also add that my amp is a Musical Fidelity A3.2, with plenty of power. I already get a fair amount of bass when it's cranked up loud enough.

I'm not looking for knock-down-drag-out booming bass, just something to round out my sound a little -- something subtle, not terribly noticeable. I don't want it to sound like I'm using a subwoofer.

Also, this is in my living room, not a dedicated listening room. So placement is constrained; the wife just isn't going to put up with a 14" cube just sitting wherever it wants to live. Hopefully it won't be a problem; I have a space for it pretty much right in between and in line with the MMGs.

[JoeE SP9]

With planar speakers the lowest crossover frequency that works is the best. This is probably true for any speaker. I have my electrostatics crossed over at 80hz. I have tried lower but my panels don't like going that low at higher volumes.

[Mike Anderson]

OK, at this point I've set the crossover at 40hz; it sounds fairly transparent that way. However, no matter what I seem to do, I get a dip in level right around 65 hz. I think I must have a room problem. Not only that, but if I play a test tone at 65 hz using only the MMGs, one of my MMGs (the one closest to the corner of the room) rattles rather loudly. It only stops if I grab the frame of the speaker and hold it firmly.

Anyway, I made a series of test tones starting at 30 hz and increasing in 5hz steps up to 160 hz. I've got it set so that (to my ears anyway) it sounds as flat as possible, excepting for the dip at 65 hz; I'm not sure what to do about that.

I also made a sweeping/rising test tone starting at 30hz and increasing very slowly up to 22000hz. If I have any kind of volume coming out of the amp, it's a freaking disaster! There's huge peaks and valleys in the volume, stuff is rattling and rumbling all over the place; criminy, thank God my music doesn't sound that bad! Still, I sure wish I knew what to do to even it all out and to get rid of the rumbles and rattles.

I tested the MMGs by themselves, and they don't really start to drop off until about 60-55 hz. Shouldn't that tell me what the crossover frequency should be, if I could figure out the slope of the MMGs as compared to the subwoofer? How would I do this mathematically?

Thanks,
Mike

[JoeE SP9]

OK, at this point I've set the crossover at 40hz; it sounds fairly transparent that way. However, no matter what I seem to do, I get a dip in level right around 65 hz. I think I must have a room problem. Not only that, but if I play a test tone at 65 hz using only the MMGs, one of my MMGs (the one closest to the corner of the room) rattles rather loudly. It only stops if I grab the frame of the speaker and hold it firmly.

Anyway, I made a series of test tones starting at 30 hz and increasing in 5hz steps up to 160 hz. I've got it set so that (to my ears anyway) it sounds as flat as possible, excepting for the dip at 65 hz; I'm not sure what to do about that.

I also made a sweeping/rising test tone starting at 30hz and increasing very slowly up to 22000hz. If I have any kind of volume coming out of the amp, it's a freaking disaster! There's huge peaks and valleys in the volume, stuff is rattling and rumbling all over the place; criminy, thank God my music doesn't sound that bad! Still, I sure wish I knew what to do to even it all out and to get rid of the rumbles and rattles.

I tested the MMGs by themselves, and they don't really start to drop off until about 60-55 hz. Shouldn't that tell me what the crossover frequency should be, if I could figure out the slope of the MMGs as compared to the subwoofer? How would I do this mathematically?

Thanks,
Mike

Raise the crossover point. A good place to start is the -3db point for the Maggies. Use the -3db point you have measured. If you still have a serious dip at the crossover point raise it in 5hz increments until you have minimized the dip. If you go to high the bass will begin to sound muddy and you will degrade that clean Magnepan sound. Going too high will also give a serious hump at the crossover point. MMG's do not have a lot of surface for the bass. Consequently the roll off is in the area that smaller bookshelves usually have. In any case, I don't think you bought MMG's because of their prodigious bass. In any panel speaker, the larger the diaphragm the better and deeper the bass. The amount of bass produced by any panel is determined by panel size, room placement, room dimensions and furnishings. Use measurements to get the sound in the ball park. Use your ears to fine tune things. The rattle you hear is probably a result of the nearness of the corner. It may be exciting panel resonances. Larger Maggy's benefit from stands that stiffen the frame. There is no reason to believe that MMG's would not benefit from the same.