Thanks for the kind words.
Qts is kind if large so cabinet will be big if you want to go low. What are your goals in terms of bass extension and max cabinet size, etc.
I would be happy with just 40 Hz. Love the idea of an easy XPS sub.
Cabinet size I would like to keep similar to your build, but I'm open to many ideas. It will be used for low-level listening in my office to mate up with my W4-930 converted Minimus 7s on my desk. Sub would go under the desk near my feet.
Rather than bin these old drivers, I thought maybe there could be a sub in their future. These QTS numbers are too large for the build in this thread and probably too small for open baffle... Maybe a TH or TL made of XPS? I will get some real dimensions of limitations for the space under my desk on Friday.
For under desk sub duties you do not need a lot of SPL and a slot loaded sealed sub may work too - high Qts is good there to reach deeper. Let me think about it and get you a design. I think I understand the size constraint now that it is under the desk. 40 Hz should be doable.
Oh man this sounds fantastic to pair with some of the small, full range designs! Its kind of hard to picture to enclosure design. Its essentially the same as the original tang band, right? I don't know very much about bandpass designs at all! This is definitely the next thing I build though.
You're the best man!
You're the best man!
Yes, similar to the design shown in post 1. I will leave it up to you to do some of your own homework to design the box dimensions given the volume constraint for the back chambers, the slot vents (which are kind of long), and the slot dimensions. Roughly if you need a 18.5 liter chamber, and it is 10 in tall x 9 in deep, it will have to be about 12.5 in long. You need two of these one on each side. Now you need a 0.75 in wide x 10 in tall x 22 in long slot vent. To get that length in a chamber with a 12.5 in x 9.0 in walls you will have to wrap it around the inside of that chamber over almost 3 walls. Note that the volume of the chamber required does not include the volume taken up by the vent and wall that make that vent. If you use 0.188 in thick foam core to define the internal channel walls, you can keep the volume smaller. The two slot vents then lead to the back of the 4.75 in wide x 10 in tall x 10 in deep slot which forms the output port. The trick is to make all your panels (except the top and bottom lids) 10 inches high (they need to match each other rather than be exact at 10). Once you have all your 10 in wide boards, cut to length as you glue. Use hot melt to tack and caulking to seal all internal seams. Don't forget to add bracing to large panels to reduce the flex and "breathing" mode.
Good luck! This thing should actually be quite the bass monster if you have an amp capable of giving it 250 watts. I do worry that it will burst itself apart if you pump 120 dB out of it - but that may actually be kind of cool to witness
You won't lose much other than some XPS and glue... Oh, and I did test mine as a sub with a full range top (a DCR - http://www.diyaudio.com/forums/full-range/252627-viva-la-vifa-curvy-cabinet-dcr-tc9fd.html) (driven by a small class D Breeze Audio TPA3116D2 2.1 amp - http://www.aliexpress.com/item/NEW-TPA3116-50W-50W-100W-2-1-HIFI-digital-power-amplifier-HIFI-beyond-TPA3123-TDA2030-LM1875/1719548803.html?af=ppc&isdl=y&src=Google&albch=Google&albcp=Search_Search-ALL-PLA&albkw=None_US-Shopping-Search-Product-AliExpress_none_none&albag=home_none_Search-ALL-PLA_1013999999870&albmt=broad&albst=search-text&albom=OTHERS_None_20130807_Aliexpress&creative=31447451305&ptsid=1013999999870&gclid=Cj0KEQjwxZieBRDegZuj9rzLt_ABEiQASqRd-rKIRbCGGeIuwh0EQxgi0pfGtHKJD8HNIIyQNTiZmLQaAjZR8P8HAQ) and it sounded fantastic. Perfect as an under desk sub except that if I were to use it at my office they would throw me out on the street!
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MCM 55-2421 T/S
Hi xrk971,
I like your result for the MCM 55-2421 PPSL in Post #40. That would be quite the test for the foam board method. Did you use the MCM T/S parameters or measured T/S? Littlemike (and others) measured these. I'll attach littlemike's values:
sreten posted these as measured by Zaph:
Fs = 30.95
Qms = 12.2863
Qes = 0.2365
Qts = 0.2320
Vas = 23.88
SPL = 86.59
Le = 2.42
B = 13.15
Xmax= 8mm (16mm P-P)
Regards,
Hi xrk971,
I like your result for the MCM 55-2421 PPSL in Post #40. That would be quite the test for the foam board method. Did you use the MCM T/S parameters or measured T/S? Littlemike (and others) measured these. I'll attach littlemike's values:
sreten posted these as measured by Zaph:
Fs = 30.95
Qms = 12.2863
Qes = 0.2365
Qts = 0.2320
Vas = 23.88
SPL = 86.59
Le = 2.42
B = 13.15
Xmax= 8mm (16mm P-P)
Regards,
Attachments
With Xaph's measured T/S params, I get a similar result, now with HPF set at 27.25Hz and xmax occurring at 47 volts to produce this result.
Attachments
Here is a link to my project. 2x 15" closed in 470 liter box, PPSL, measurements
http://www.diyaudio.com/forums/subw...inet-subwoofer-2x15-closed-8.html#post3463101
http://www.diyaudio.com/forums/subw...inet-subwoofer-2x15-closed-8.html#post3463101
I like the idea of this so much I might bypass the foam idea and just build the enclosure. Ive been on quite the other woodworking kick lately so it should be another fun project! I think I would use 1 x 10 hardwood boards and MDF for the big pieces just because I have some on hand. Finished sizes of those boards are actually more like 9.5" so how does that change the dimensions of the ports? Do they need to be a touch longer on either side?
Adjust box to keep volume and probably shorten the vents since CSA is now less. Maybe 21 in long instead of 22 inches. Slot vent with drivers at 4.75 in wide and 9.5 in tall x 10 in long still. Good idea to use precut shelving material. Let us know how it goes.
The only problem with making it out of wood is that you will have have a sub that is now "light as wood". Doesn't have the same ring as light as air
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Alright I'm starting to draw this out (physically on a piece of MDF because I have no CAD software) and it seems pretty big actually. Are all of the measurements you've given for just one side of the enclosure?
So if you were looking at the front of the enclosure with the slot port, you'd have a 10" (or whatever) side, a 4.75'' port and then 10" on the other side?
Also, I have to subtract the volume of the ports from the total volume of each side, right?
My first attempt didn't work >.< If the interior of the enclosure is 9.5" there isn't enough room on the baffle to fit the driver! DOH!
So if you were looking at the front of the enclosure with the slot port, you'd have a 10" (or whatever) side, a 4.75'' port and then 10" on the other side?
Also, I have to subtract the volume of the ports from the total volume of each side, right?
My first attempt didn't work >.< If the interior of the enclosure is 9.5" there isn't enough room on the baffle to fit the driver! DOH!
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It will be about 3ft wide x 1 ft deep x 11 in high. You cannot use 9.5 in wide boards for top and bottom. You might have an easier time cutting XPS foam. It's not the most compact sub but is slender and like a foot bench. Not sure why you say 9.5 in doesn't have enough room for driver ? Cutout is 7.5 in or so right?
Well the way I drew it up it would be super close. 9.5 internally, -.75 for the port width and another .75 for the wood. The screws to mount the drivers would have had to go down the length of the slot. Its a shame how big it is. I don't really have the space >.< would the same time thing work if you used one driver and just got rid of a whole section?
Design for Single MCM55-2421 driver in SL bandpass
I redid the sim using 9.5 in wide boards and a single driver. The design is still same volume of 18.5 liters for the rear chamber, 0.75 in deep x 9.5 in tall x 23 in long vents, 4.75 in wide x 9.5 in tall x 10 in long slot vent where driver is mounted in a push-only config. The max drive voltage to hit xmax is now 25 volts (which is easy to do in most sub amps) and gets you 115 dB in corner loaded config under your desk with 31 Hz (-3dB) bass extension. Not too shabby for some leftover wood boards and a $30 driver.
Go build it and let us know how it shakes your desk apart!
I redid the sim using 9.5 in wide boards and a single driver. The design is still same volume of 18.5 liters for the rear chamber, 0.75 in deep x 9.5 in tall x 23 in long vents, 4.75 in wide x 9.5 in tall x 10 in long slot vent where driver is mounted in a push-only config. The max drive voltage to hit xmax is now 25 volts (which is easy to do in most sub amps) and gets you 115 dB in corner loaded config under your desk with 31 Hz (-3dB) bass extension. Not too shabby for some leftover wood boards and a $30 driver.
Go build it and let us know how it shakes your desk apart!
