Bandpass for MM124?

[LILDRAGON]

Hi what are the measurements needed for a bandpass box (MM124) Will this configuration work, its about 1 cu ft in the sealed section and 1.4 cu ft in the ported section (Dimensions 21 3/4" depth X 14 1/4" height X 14 1/4" width). The manufacturer is JDS? Never heard of them though. Please let me know what is good and not, also the music I listen to most is rap and trance. Thanks for any help.

[PoweredByDodge]

I've never been one for pre-fabbed boxes... they tend to not be made of 3/4 inch mdf, and they also tend to be stapled instead of screwed together -- no silicone on the joints and no vibration damping material between the joints. get what i'm saying?

Kim and the polkies have a design blueprint for an iso-push pull bandpass--- personal pref's aside --- fact is a box designed by the guys who work for the manufacturer will most asuredly "out-sound" and outperform a prefabbed generic one.

i'm sure kim wil reply w/ the iso plans -- if not -- look on other posts, he's posted it before.

... personally -- i'd ask u if you ever considered "ported" boxes... slot ports can sound really nice on a momo and give u better freq response than a BP -- if u dig ported -- like i said, ask the polk guys, i'm sure they can hook u up.

[RuSsMaN]

First of all DO NOT use a Momo in a PORTED enclosure. The end result will more than likely be a non-functioning driver.

A general rule of thumb for Polk auto subs is bandpass or sealed, 1cu ft total space. I'll have to check my resources, but I believe the ideal bandpass enclosure (per Polk) is .6cu ft BEHIND the driver, .4cu ft in FRONT. (I may have those reversed, but it should be printed in your Momo manual/insert).

Justin? Kim?

Cheers,
Rooster

[Kim]

LILDRAGON,
Here are the plans for a single MM124 bandpass enclosure with the volumes that you have given. Before installing them into this enclosure, make sure that the enclosure is constructed out of 3/4 inch MDF and seal all interior seams with a silicone caulking. Do not install this woofer into a particleboard based enclosure!!! You will blow it apart due to the intense pressure generated by this woofer at higher volume levels. The ports for chamber two will have a internal diameter of 4 inches and their length will need to be 10 inches in length.
Make sure to install some polyfill into both chambers to reduce resonance and turbulence. To get an idea on how the damping material should be applied just refer to the attached plans below.

Thanks,
Kim

[djphoenix]

I like the box design but I plan on 2 MM124 12", how would the box design differ for 2 12's instead of a single box design.

[Kim]

From a box construction point of view, not a whole lot.
I have attached the plans below for a dual MM124 woofer enclosure.
There will definitely be a lot more BASS!!!

Have fun!
Kim

[djphoenix]

ok the doc you attached on the one pic that shows the2 woofers, it looks like you have the woofers directly facing each other. is this correct or is this just a side veiw that doesn't show the woofers off set from each other. My first step is to get my 12's but when time comes I want to be able to take these plans to someone and say build it for me.

[TrappedUnder Ice]

Scary thought that a sub would be NON-functional in a ported/vented enclosure...that BP and sealed are only options... Very scary indeed!!!!:eek:

[Kim]

With this type of enclosure design we still are using the vacuum of the sealed chamber to help regulate the cone displacement
since both woofers are mounted face to face.

[PoweredByDodge]

Originally posted by TrappedUnder Ice
Scary thought that a sub would be NON-functional in a ported/vented enclosure...that BP and sealed are only options... Very scary indeed!!!!:eek:

Hmm... I think my dear thomas (talking like sherlock holmes to watson) that we've come upon a revelation... if sealed and BP are the only options for a woofer due to an extreme need for overregulation of cone displacement, then would this not indicate my dear thomas that the woofer had an inadequate suspension and possibly a voice coil not adequate for "supremem thump-age"...

Imma go smoke a pipe and put on some ridiculous scotland yard-esque hat... just call me "constable vinnie" --- har de har har.

[[ i'm anti-ports... but the fact that you can port an mtx 6000 but not a momo makes a guy wonder about the cosmos, the existance of god, and my take on the theories of the universe. ... no i'm not high. ]]

[Kim]

Just remember every driver has its mechanical limitations.
As for inadequate suspension, there is more to it than that.
Woofers that use a high mass cones such as our MOMO series require a sealed enclosure to help control excesive cone displacement at lower bass frequencies. This goes for any high mass cone designed sub out there. You also need the assitance of some very robust spiders also to keep everything together from being ripped apart when you are cranking the system at high volume levels. Most people don't use a subsonic filter.
This is where the vacuum of the sealed chamber comes into play. These woofers have much longer excursion than woofers designed for ported enclosures.
Woofers that are designed to be used in ported enclosures are lighter in mass and have a shorter excursion. They are using the enclosure design and tuning to make up for the output and excursion limitations. Bottom line... there is no free lunch.

[PoweredByDodge]

that has got to be one of the most well thought out (and correct) answers i've ever heard to such a question/ comment...

[TrappedUnder Ice]

So kim..your telling me that the momo has better excursion than a DD 9512?
just curious?