Guys, im in love with that SKRAM design. Very anxious to have a box you can change vent plugs, goes like stink from 20 to 120hz. But the size!! I was wondering: is it possible to build a 20% smaller version with 18 driver? Im not technical enough to figure that out in Hornresp. 296 liter from 370. or any other config possible?
Also: I read its easier to build than the OTHORN yet im not a woodworker at all. the hours are ranging between 25 thereabouts for experienced guys to way over 60 for guys with no tools and such. Is CNC a 100% necesity? I mean if I could do it myself then yes, but if i have to hire someone that will cost thousands but also after its finished, if I want to sell it, passive DIY subwoofers like therse are hard tos ell and probably for a whole lot les than the bult evrer costed. What do you think?
EDIT I found a DIYaudio user saying this 2 years ago:""
For bass go 21" ...... lots of high grade options, with strong motors.
B&C 21ds115 works very well in undersized reflex enclosures due to very strong motor (BL 40!!!!).
Check data-bass.com , it has a wealth of independently measured data, also check the forums. There are several diy designs available there, such as the" ckram "(single 21" 30hz tuned reflex that can be modified to 6th order bandpass with a front attachment plate)
And "Skram" single 21" bandpass
15" has ~150sqin Sd, 18" has ~220sqin, 21" has ~300sqin
To get deep, you need a decently sized enclosure, so why not go all out on the driver to achieve higher power density!
30 Hz is a must nowadays, if you want to distinguish yourself & keep up.
The "fancy" european drivers are available on the us market, b&c, lavoce, 18sound, bms, beyma, rcf......""
Apparently there are SKRAM deisgn for smaller drivers? Does anyone know where all those files from DATA BASS.COM went? Im very fascinated and interested.
Also: I read its easier to build than the OTHORN yet im not a woodworker at all. the hours are ranging between 25 thereabouts for experienced guys to way over 60 for guys with no tools and such. Is CNC a 100% necesity? I mean if I could do it myself then yes, but if i have to hire someone that will cost thousands but also after its finished, if I want to sell it, passive DIY subwoofers like therse are hard tos ell and probably for a whole lot les than the bult evrer costed. What do you think?
EDIT I found a DIYaudio user saying this 2 years ago:""
For bass go 21" ...... lots of high grade options, with strong motors.
B&C 21ds115 works very well in undersized reflex enclosures due to very strong motor (BL 40!!!!).
Check data-bass.com , it has a wealth of independently measured data, also check the forums. There are several diy designs available there, such as the" ckram "(single 21" 30hz tuned reflex that can be modified to 6th order bandpass with a front attachment plate)
And "Skram" single 21" bandpass
15" has ~150sqin Sd, 18" has ~220sqin, 21" has ~300sqin
To get deep, you need a decently sized enclosure, so why not go all out on the driver to achieve higher power density!
30 Hz is a must nowadays, if you want to distinguish yourself & keep up.
The "fancy" european drivers are available on the us market, b&c, lavoce, 18sound, bms, beyma, rcf......""
Apparently there are SKRAM deisgn for smaller drivers? Does anyone know where all those files from DATA BASS.COM went? Im very fascinated and interested.
Last edited:
Yes it is possible. Reducing cabinet volume does reduce the chamber to port volume ratio.
Do you want the additional upper response from the stubby horn?
No, you could do the dados with a router and clamped down guides or a table saw.
Or butt joint everything.
The B&C 21DS115-4 has a BL of 24.8Tm, the 21DS115-8 BL is 30.13Tm.
Their 18" have similar motor strength with less moving mass, and can be used in smaller enclosures.
And if you want to get deep, why not use a driver with a lower Fs.
https://data-bass.com/systems/5c48bfc611126b0004ca12eb
The BMS 18N862 in a 7.6 cubic foot (215L)gross has similar output per liter as the Skhorn, 24cubic feet (679L) cabinet, both with 25Hz Fb. Add 9.54dB for three cabinets- which would fit in the space of one Skhorn.
The 1x21" SKRAM has less slightly power density than the 2x21" Skhorn.
Two meter SPL add +6dB for one meter equivalent:
BMS 18N862 20Hz 108dB, 25Hz 114.5dB, 30Hz 118.8dB
18N862 x3 20Hz 117.54dB, 25Hz 124dB, 30Hz 128.34dB
Skhorn 2x21"B&C IPAL 20Hz 116.5dB, 25Hz 124dB, 30Hz 128.5dB
Building a bass reflex with blockable ports is much easier than a complicated cabinet like the SKRAM, and multiple cabinets allow a lot more placement flexibility, and the ability to do cardiod arrays.
Art
Thanks Art! I had a long look at your Keystones too but they are a bit too big for me.
And yes, the last few weeks I kind of settled on a ported design with BMS 18S450 (cheaper than the 862) but what draws me to that SKRAM is it seems to have 2 of the best worlds: great low extension and a good punch, a fantastic punch you dont find with ported. I also remember some folks here saying the BMS 862 has a very light cone. Good for ported (or sealed) but not for venturing in port or other designs.
Its funny I started a thread about a 15DS115 a few weeks ago as replacement for my Dayton ultimax 15"" sealed subs since those Daytons are heavy cones that kind of seem to lack a bit above 50hz. I changed my whole room, setup and everything and while it did improve, it still lacks. Yet the last week or so I see many posts about how those uber strong DS115 motors make it possible to experiment a lot with smaller volume cabinets. Data Bass has a lot of great stuff.
I have 2 subwoofers since it works out great for modulation and constantly measured how I can fit 2 SKRAM cabs in my smallish room but maybe I should start with just one cab. For output already way over anything ill ever need. That said I think maybe ill stick with its original deisgn, the 21"" driver setup. Thanks again for the help!
And yes, the last few weeks I kind of settled on a ported design with BMS 18S450 (cheaper than the 862) but what draws me to that SKRAM is it seems to have 2 of the best worlds: great low extension and a good punch, a fantastic punch you dont find with ported. I also remember some folks here saying the BMS 862 has a very light cone. Good for ported (or sealed) but not for venturing in port or other designs.
Its funny I started a thread about a 15DS115 a few weeks ago as replacement for my Dayton ultimax 15"" sealed subs since those Daytons are heavy cones that kind of seem to lack a bit above 50hz. I changed my whole room, setup and everything and while it did improve, it still lacks. Yet the last week or so I see many posts about how those uber strong DS115 motors make it possible to experiment a lot with smaller volume cabinets. Data Bass has a lot of great stuff.
I have 2 subwoofers since it works out great for modulation and constantly measured how I can fit 2 SKRAM cabs in my smallish room but maybe I should start with just one cab. For output already way over anything ill ever need. That said I think maybe ill stick with its original deisgn, the 21"" driver setup. Thanks again for the help!
Rediculous (huge) parallel pipe designs with 18ds115-4. It interesting how well it ‘behaves’ in a pipe 1/2 Sd ?
Maybe there’s a way to downscale this? And/or Get rid of the big series exit section that flattens it out so nicely
Maybe there’s a way to downscale this? And/or Get rid of the big series exit section that flattens it out so nicely
Attachments
Hi Art, I think you're mixing up the SW115 and DS115 motors. The DS has around 30% more motor strength, the 8 ohm is indeed BL=40.
Interestingly, and something I don't quite understand, is the 18" models have the same gap depth/flux density and have a 4mm longer coil than the 21" models, yet have a lower BL figure.
I'd say it was due to a larger gauge wire being used on the 21", but the power rating is the same leading me to think that would not be the case.
Anyway, food for thought, I found it a bit novel.
Hi Elmo, I think you'll find that making the chamber and vents smaller will work for lower performance 18" drivers just fine, and if you're not intending on using the cabs for PA apps I'd even recommend it. However Josh has obviously spent a lot of time optimising the design, and by forcing the same output into a smaller rear chamber/ports you're going to run into port compression and noise a lot sooner.
Having said all that, this can be a good thing from a thermal perspective, so it may be a case of trading absolute performance for long term performance.
Having said all that, this can be a good thing from a thermal perspective, so it may be a case of trading absolute performance for long term performance.
Yes, I did mix up the specs between the copper coil 21SW series and aluminum coil 21DS series.
That said, the 21SW115-8 motor has 1.15T flux density, the 21DS115-8 has 0.8T flux density, the SW motors have around 30% more motor strength, but the aluminum coil 21DS115-8 specs BL at 40.8 Txm, while the copper coil 21SW115-8 BL is "only" 30.13.
The 21DS115-8 coil is 36mm, 2mm longer than the 21SW115-8 34mm coil length.
40.8 to 39Txm is not much of a BL difference for a 10% longer coil, what I find more interesting is the 18DS 40mm coil Xvar is 14mm, while the 21DS 36mm coil Xvar 16.5mm.
The 21DS115-8 Re is 5.1 ohm, Le4.6mH, the 18DS115-8 Re is 5 ohm, Le3.85mH.
The longer coil must be wound a bit differently 😉.