bandpass for mm120

[journey]

i noticed on the polkaudio.com site, in the toolbox they have a bandpass box for the polkmomo mentioned. I was just curious though, since the low side is tuned to 55hz, and the high side tuned to 57hz, isn't it going to sound fairly bad? I'm just thinking that below 55hz the cone is going to move too much(at least it works that way in ported boxes, bandpass work differently in that respect?.

Oh well, the real reason i asked is because i'm looking to build a box for my mm120, i have it in a q-logic .88cu. ft. box, but i didn't know when i bought it that it was particle board. Figured i should replace it with something made of MDF, and if i build something custom i can make it fit better in my back area too.

I'm actualy interested in building a ported enclosure, according to the EBC numbers, the momo is equally suited to ported or sealed designs, so does anyone have some suggestions for enclosure size, port diamiter, and port length for the mm120's ?

thanks
journey

[Kim]

Journey,
Almost every car enclosure is tuned between 50 to 60 Hertz. This is why the sealed box volumes are so small. The car's interior will react with the sub and enclosure by increasing the lower bass frequencies from such a small enclosure. This is called "Transfer Function". You can think of this as "interior passive equalization". This starts around at 60 Hertz and can increase the level of the lower bass frequencies by as much as 12 dB from 60 Hertz on down to 20 Hertz. Now if you were to listen to the sub in your house, you probably would not care for it due to the box being tuned at 60 Hertz. There will be very little lower bass information below this frequency.

Regarding MOMO woofers... we do not recommend using these woofers in a vented enclosure due to their high cone displacement at lower bass frequencies and their high mass cones. You need the vacuum
of the sealed chamber to act as a cone excursion regulator. Plus you won't risk damaging the suspension of the woofer.

Happy Box Building!!
Kim

[maddux4cyoung]

But you give plans for ported enclosures (bandpass) on the website specifically for mm100's (which I have), and then state that they are not designed for this type of box...

[goingganzo]

band pass is a sealed encloser the sub hits into the box i have a old mtx band pass plexi box in my old car waiting to sell

[JustinGoodie]

bandpass is different than ported....

in a ported box, you've basically got a sealed box with a port in it...

a bandpass box is essentially a sealed box with a ported box on the "front" side of the woofer...

notice the little figure i made in paint to help illustrate what i'm talking about... sorry about the crudeness of the graphic but it shows what i mean.