Issue with flipping it is making a 2nd gasket and rewiring the drivers to test it. It would be a 3 hour adventure to test it... We'll see if I get ambitious.
HEY ALL ! I simmed and sketched this box the other day and i figured that this would be a good place to post it ....
A friend and I bought some MCM drivers that (SURPRISE!) have specs that are far different than what is published on MCM's website .... I know I know , MCM is known for their parameter inaccuracies, I wish they would set their OEM straight and at least force them to use a better grade of ferrite, a little more motor strength would have been nice on these.......
Compared to published figures our measurements showed a high QTS/QES , lower BL factor, higher FS , and lower VAS ..... I can post the measured T/S parameters if anyone is curious .... They were measured with Dayton's DATS.........
Designing a compact and efficient quarter wave box for these drivers is possible and required some additional driver offset in the path ... The version i am attaching to this message is a single fold but i suspect a double fold would also work well and would produce a more cubelike cabinet ..
This box works for the MCM 55-2992, the MCM 55-2981, and also the Dayton PA310 and the Dayton PA255-8 ..... There are others that im sure would work, i have only tried a few drivers in this sim so far ...
The above drivers are limited by XMAX but nevertheless the output is respectable for such small cabinets and the bandwidth is pretty decent.
The graph i am posting is with the 55-2992 (measured parameters) drivers in four of these cabinets .... Just under 130db isn't too bad for 300 liters total and some woofers that we got on discount from MCM 😀 Note: It is just an approximated response, it is not entirely possible to sim this in HR with precision, simming it in Akabak would be more appropriate ...
HAPPY HOLIDAYS TO ALL OF YOU DIYaudio DENIZENS!
Matthew in Arizona
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I just wanted to update you - work has been astonishingly busy - 70 to 80 hours a week since early October while we divested a business unit.
I just rec'd my Makita track saw ans will start building the enclosure shown in post 552 after the holidays are over.
Finally.
I just rec'd my Makita track saw ans will start building the enclosure shown in post 552 after the holidays are over.
Finally.
Matthew,
Nice design. Reminds me a bit of Tb46's reformatting of my PP SL Bandpass in asymmetric layout that lawbiding just built. He used 55-2421's.
Nice design. Reminds me a bit of Tb46's reformatting of my PP SL Bandpass in asymmetric layout that lawbiding just built. He used 55-2421's.
Hi Matthew Morgan J,
Would be great if you could list the measured T/S parameters for the 55-2992.
My experience w/ MCM's T/S parameters have not been good either, but, despite their best efforts, I was able to save the drivers by mounting them isobarically, and then stuffing them into a sono tube BP4 which is still one of my favorite home subwoofers (you just never know). It's dicouraging that they don't even get the data for their more expensive units correct. Interestingly the 55-2421 8" has been measured by a number of people, and is not too far off (except that MCM lists the 55-2421's Xmax as peak-to-peak, oh well). I still would go w/ measured T/S, e.g.: Zaph's are listed in a few places.
I like xrk971's box, he arranges the drivers in a PPSL plenum, and then piped the duct through this plenum (slot). That should work well for your drivers/design too.
Regards,
P.S.: "Happy Hollidays to You too!"
Would be great if you could list the measured T/S parameters for the 55-2992.
My experience w/ MCM's T/S parameters have not been good either, but, despite their best efforts, I was able to save the drivers by mounting them isobarically, and then stuffing them into a sono tube BP4 which is still one of my favorite home subwoofers (you just never know). It's dicouraging that they don't even get the data for their more expensive units correct. Interestingly the 55-2421 8" has been measured by a number of people, and is not too far off (except that MCM lists the 55-2421's Xmax as peak-to-peak, oh well). I still would go w/ measured T/S, e.g.: Zaph's are listed in a few places.
I like xrk971's box, he arranges the drivers in a PPSL plenum, and then piped the duct through this plenum (slot). That should work well for your drivers/design too.
Regards,
P.S.: "Happy Hollidays to You too!"
Thank you Sir ! and Yeah? That one in the pic looks to be series tuned cabinet, am i right? I see what looks like a vent at the back of the plenum .... Neat!
Have a sketch for that one?
Tb46 ,
Absolutely i will post them! no problem at all , they are just screenshots from DATS.... Yes, those MCM woofs can be decent if you have some way of measuring parameters so you can design something to suit, i just feel bad for the folks who build boxes based upon MCM's published specs and aren't getting the desired results, kinda crummy on MCM's part.. It would be nice to see them update their published figures on a regular basis so that they reflect their current stock ..
Heck yes, I like the look of that, series tuned "tapped" designs are a great way to go, i am a big fan of such things 😉..... I am curious about his internal configuration ...
Ok , Tb46 here are those DATS screenshots for the 55-2992
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Tb46 ,
We took one of the 2992 drivers over to a nearby subwoofer build house (quite literally a house 😛) (this is a very talented guy that we know who builds custom competition car audio subs) .... Our friend put the MCM woofer onto his frigidaire sized magnetizer machine, and ZAPPED IT!!
Our attempt to increase the magnet's charge only made a small improvement ...
Here is the screenshot after additional magnetizing:
We took one of the 2992 drivers over to a nearby subwoofer build house (quite literally a house 😛) (this is a very talented guy that we know who builds custom competition car audio subs) .... Our friend put the MCM woofer onto his frigidaire sized magnetizer machine, and ZAPPED IT!!
Our attempt to increase the magnet's charge only made a small improvement ...
Here is the screenshot after additional magnetizing:
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Hi,
Thanks for the data. Love the Frigidaire story, you wouldn't have any pictures of the process?
Regards,
Thanks for the data. Love the Frigidaire story, you wouldn't have any pictures of the process?
Regards,
Tb ,
The machine just slams the magnet with an obscenely strong magnetic field for a fraction of a second to align the atoms in the material ...
Here is a video showing how is done ... Our friend's magnetizer is not as fancy as this one, lacks the digital readout, and the coil is on top of the machine instead of what is shown here: https://www.youtube.com/watch?v=-VMJN_hoVbk
This experiment indicates that MCM's manufacturer has a sufficiently strong magnetizer but likely skimped on the grade of ferrite used .... It is possible that they also may have used an abnormally large gap but i didn't tear any of the woofers apart to measure the gap width , perhaps if we burn one of these out we will do that.... Currently the drivers are over at my friend Pete's house, he whipped up a large ML-TL for them out of OSB on the cheap .... It actually sounds damn good! Nice smooth deep bass, should work well for his bass guitar or any number of other applications ..
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Hmm, IME remagnetizing various types of magnet materials for slot car motors they needed to be demagnetized first to get the max charge, otherwise there's little change.
GM
GM
Hi,
Recharging assembled magnet structures is at least as much art (technique) as science, especially when one does not know the magnet material.
Regards,
Recharging assembled magnet structures is at least as much art (technique) as science, especially when one does not know the magnet material.
Regards,
Ahh ok ,
He works with the better grades of ferrite all day every day, so i was just trusting him to do it the best possible way ....
I don't believe i saw him demagnetize it first (maybe i should ask him about that), i was standing nearby watching him when he did it and from what i can tell he just turned on the beastly machine, placed the driver's magnet into his coil and then hit the button ... It didn't cost me anything, so i cannot complain really... We were just trying it as an experiment ....
He works with the better grades of ferrite all day every day, so i was just trusting him to do it the best possible way ....
I don't believe i saw him demagnetize it first (maybe i should ask him about that), i was standing nearby watching him when he did it and from what i can tell he just turned on the beastly machine, placed the driver's magnet into his coil and then hit the button ... It didn't cost me anything, so i cannot complain really... We were just trying it as an experiment ....
True, as we found out the hard/expensive back in the '60s with AlNiCo and in the '80s with samarium cobalt. Ferrite OTOH with a given 'brick' batch was never a problem with consistency regardless of the machine used.
GM
I'm thinking of doing the same so I'd love to hear the results!! The Dayton PA385S-8 Looks awesome in this cab. Super Flat response with a rise ready for the LPF of your choosing. The below trace compares it to the PAL12, another TH I was considering. The difference? the PAL12 is at Xmax in this trace (Gray) with 40V and the 15" ML-TP is at 75V (past Xmax at 12.8mm). 75V is chosen based on Art Welter's recommendation for heavy sine content (What I play) If taken to a full 1000W RMS you have a 125.4 dB at 40Hz, if stopped at 10mm Xmax, you're at 121.8 at the same spot.
15 ML-TP vs PAL12 by natepalsa, on Flickr
Heres a pic for everyone interested; I can post another picture with dims if desired as well. (sorry for the skew)
15MLTP by natepalsa, on Flickr
I Like an 8Ohm cab for the potential to snag a Nu6000-4 one day and run 2 of these subs on the bridged channel and stereo Otop12's on the other!
