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B&C 21DS115 23hz 800L TH build

22K views 105 replies 19 participants last post by  jpmst3 
#1 · (Edited)
22hz 792L TH build B&C 21DS115

I had for a couple of years wanted to rehab the downstairs living room into a dedicated HT room and office. I wanted pretty big sound, yet needed to balance my lack of a working shop space, limited wood-working skills, and some other factors (like budget, dratted money thing!). Also, given the time constraints I face trying to finish up the Physical Therapy program at ISU, I was leery of a complicated build, or multiple small builds.
I had previously owned a B&C 21SW115 and had it in a QB3 alignment. In spite of being poorly aspirated (I'd not yet learned about the poor performance of very low aspect, undersized slot ports), it being a pretty formidable driver & I loved the thing. I had always wanted to try it in a horn, and alas that never happened. SO, few years later and I get the itch.

There is no way to build a large horn and then move it downstairs. I went so far as to build a full-size cardboard mockup of a lilwrecker, and it would not fit around the corner at the top of the stairs. Well, it's going to be a dedicated man-cave down there, so why not build it in place, size not an issue (up to a point).

B&C came out with the DS model of the 115, and I'd played around with modeling it. What would it do in a suitable horn? Inspired by the simplicity of a single fold 15" TH I'd run on to here at AVS, I played around with fattening the cross sections up and the initial results looked promising. I bounced the idea off of lilmike, and he took it from there with simplicity and performance the goals. Loud, low ... not small, noooooo, that it is not, and I'll have to saw it up if/when I leave here. I have no problem with that.

Acceptable to me :)
It models around 98dB on a watt, ho-hums at a kilowatt, and has an F3 of ~20hz. Not world class, but no lightweight either.

....but here are a few build pic's.
 

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#3 ·
Thank you! You know, it seems pretty obvious now that you mention it, that would be an excellent idea. Still accessible, easy enough, and you're right, that's the least supported section on the structure, probably. :)

Did some more listening, and really, really liking what I'm hearing. I haven't bumped any clip lights yet, and to say the output is prodigious would not be an overstatement ... sheesh! Can't wait to do some measurements (be just at the horn mouth and my MLP, but better than nothing), and I'm pretty new to measurement so we'll develop that in the days to come.

Here are the inputs and some curves.
 

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#6 · (Edited)
Heh, yeah, finally, and worth the wait. A big shout-out to Lilmike, wouldn't have happened without him. LTD02 put together a possibility -- a couple in fact -- and they look very interesting, in fact output up in the 40-80 hz range that models as just brutal, but the tapped horn had the 20-40 hz covered really nicely & I'm not lacking in playback range above that... nooooo, not at all by my humble standards. Ultimately the dead simple single fold, three sheets of plywood and all, gave the TH the nod. In time, maybe I'll get a handle on something like half of Ricci's Skhorn, in some good wood, that wouldn't have to be relegated to the mancave. 260L maybe? Be interesting. Lilmike is doing some work on those 6th order BP/OD's too, and I imagine others have as well but I haven't run into them yet ... really new to me.

BUT, I haven't even figured out where this thing taps out yet. I just listened to J.S. Bach's Toccata and Fugue in D minor, some great organ, and shook things up! Listening to the Bach, the EP4000 fan didn't even switch to high mode. It did during some Dave Weckl, but for like 30 seconds. Really tactile experience, too. My mains ran out of steam (B&C 10"'s with DNA-360's, active biamped generously driven), but the sub just shrugged; "That's all you wanted me for? Sure, now back to my nap" kind of thing.

Chrap, you're a little nuts, a Skhorn AND a pair of TH-50 clones? Gawd ... love it! :laugh: You're going to have to invest in tons and tons of Kevlar to keep your house together!!
 
#7 ·
House, no. This will be going in my detached shed which is about 5m x 6m x 2.7m. So its a HUGE space I need to fill with bass.:D It will be very slow going of coarse because everything got delayed. SO for my TH50 clones they will be way down the road this year. Skhorn wont be started until about middle of March. AND of coarse I have to buy some more amps. So I will have to get by with my single MicroWrecker for now.
 
#8 ·
This thing is just plain NUTS! Watched about half of "Deep Water Horizon" at -15dB is all, and it just rocked this bunker of an old house -- double brick, lath & plaster walls, and upstairs it was truly shaken up. It was giving me the beginnings of "hair tricks," and flapping my shirt sleeves and trouser legs. AND at less than half volume! I do not know what will happen when I really uncork it, but ... damaging the house is not just a hah hah, what would that be like kind of theoretical question any more.

Attaching the first impedance sweeps. Lilmike said he had some doubts about the DATS' ability to adequately power a big, heavy coil and driver; "The attenuated peaks may be a limitation of the DATS, it is a wee-tiny little amp, and that is a big-assed cone and motor, not to mention a huge horn that it is strapped to. Could also be panel resonances, but I doubt that at such low levels ... Sometimes a weak lower peak like this means weak output, but in this case, I'd question the DATS first."

Sure doesn't sound wimpy on the low end. Rather, the whole atmosphere just resonates, tactile as heck.

I will address the bracing issue tomorrow, because I did leave a large unsupported area behind the driver, and haven't gotten around to bracing the mouth. That will be rectified. I put a fair amount of effort into bracing this thing, makes no sense to leave a critical section like that flapping around.

I've never experienced anything like this monster, not even close!! Easy build, pretty economical driver, it could tear the place apart around me, I'm guessing. YAY! Still can't wait to get some frequency response sweeps done, waiting on a mic.
 

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#10 ·
I haven't, but will get the room response measured in the near future. Really interested in seeing those. Pic's? Not of the finished product. I'ts some decent looking wood, and I'm going to patch the screw holes and give it a good light sanding, then slather on the ol' Watco stain, just pretty it up a bit, and I'll post some pictures.

Can't get over how dumbfounded the experience of that soundtrack left me. And a correction: I finished up at -12dB on the receiver. I've taken music playback into the +4dB range, left me reeling, but the bass was nothing like the movie track; frappin' loud, though! Tapped out my mains, not even close on the sub. And clarity? Got it in spades. Then I listened to some of the Titanic soundtrack ... I don't suppose with a movie that cost $200,000,000 to produce, that they chintzed on the production of the soundtrack! Beautiful recording. Listened at very moderate levels, and the whole system ... wow, subtle, sensitive, powerful ... I tried to describe it to my sister and the closest I could come was to say that the system is an 800 pound gorilla that can do origami. I don't know if that conveys what I'm trying to say.
 
#12 ·
It's end-firing, and I've got it horizontal. Nominally, it is 25 1/2" x 24" x 96"... 792 liters, I think. Three sheets of 3/4" plywood, split right down the middle, and after shortening one up for the baffle & end, I ripped the rest into 8" strips I cut up and used for bracing.

That 152 that's gathering dust in your shed is virtually identical modeled in this cabinet, if you ever get thinking in that direction, of course we'll want to wait and see what the sweeps on this look like :)
 
#15 ·
I did do some additional bracing and redid the impedance sweep. A little change, but to my unpracticed eye nothing really significant. That being said, I'll post the capture. I hadn't realized (didn't read the instructions adequately, my bad) that I could save all of the sweeps to DATS memory and then do a comparison on one screen. Ah well, still learning this new and fantastic hobby! :^)
 

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#21 ·
Update: Got a measurement mic, and have my laptop (actually an old netbook) rehabbed and running, and will get a wireless issue resolved tonight if all goes well. Then I can update REW, and get to studying up on what I need to do to run the sweeps. Again, completely new to me, so I've a fair bit of learning to do. I hardly know where to start, but I gather there is an REW thread somewhere, I think right here on AVS, so that should be required reading.

But if anyone had the equivalent of a "Quick Start" to get a basic frequency response sweep, bring it on. I'm in the middle of a crazy semester in school, and don't have as much time as I'd like to devote to the project, nor what it deserves. I really want to validate the design. Others far more capable than myself are in the process of doing extensive testing on the 21DS driver, I'm interested in how this horn performs, empirically. This horn is kind of a one off. Easy and relatively economical for anyone that didn't object to the size, I suspect it may turn out to be worth duplicating. Lilmike's a hand at design, for sure, and the subjective impressions I have listening to it ... :cool:
 
#22 ·
I looked at using their 15CL in my bass guitar rig. Great value for money I think.

I have had 2.1 for a LONG time now and the biggest upgrade I made was a center channel. I had some extra speakers and decided to hear it on a movie as a center. What a difference. So while 5.1 would be a huge difference just make sure you have a great center channel. I like phantom and all but will definitely be building a nice center next for indoors. Outdoors I will have to wait a while because that will require some expensive parts.
 
#23 · (Edited)
Yes, I certainly miss having a Center; that is a big priority for me, but I sort of hesitate to put a mismatched enclosure in with a really sweet sounding system. I'd like L/C/R matching, or at least very close to match timbre, that difficult-to-describe quality of different speakers. Tonight I've been toying with the idea of an interim solution: I already have a perfectly serviceable JBL 15" 2035H (not a premium model, long step down from the 2226H. ... but I don't have one of those, I have a 2035; bird in hand and all that rot). For a center channel, I would need to limit its vertical dimension to ~17". I have 12-14" of depth and 38" of width to play with. Sooooo, I'd need to come up with a compression driver, a waveguide, and an amp (already have an electronic crossover that would work). Using the same CD/waveguide as my L/R would make sense, at least on the surface. It would be a pretty beefy center in my listening area. When I get school behind me, I may start seriously planning matching L/C/R, until then I may have to cobble things together.
 
#26 · (Edited)
You know, it just occurred to me, I still have an unused DE250, so all I need is a waveguide and a crossover, if I decided to use my QSC USA400 to bi-amp that and the JBL 2035. The JBL is 98dB on a watt, so probably en effortless 120 RMS plus headroom well in excess of the rated 1.9dB, on one channel, the other channel driving the DE250 ... I even have a modest electronic crossover. Heck, I might as well go for it. So lumber and a waveguide. Hmmmm, I'd be tempted to go with a horn with a little more dispersion than the SEOS-12, maybe the B&C ME15. $23.75 on Amazon.

Yeah, money is an item for me too. Some forum members, bless their socks & hats off, have what must be a ... comfortable margin. I do not. Mine is definitely a poor man's system.

Attached is the horn I have -- "Sue" -- loaded with respectively the 2sw152 and the DS. It's just modeling of course, but still ... that's both drivers driven to the first Xvar excursion limit above tune (turned out to be 22.2hz), 152 in gray. I don't feel as if I've made a second rate choice at all. Also attached is the JBL I've got modeled, 120 watts RMS.
 

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#27 ·
The model of the horns look pretty equal. Your JBL seems to be in large cabinet for the port tuning.

So when it comes to building your own speaker just make sure you take the time to measure and adjust from there. There is quite a bit of work that needs to be done to optimise parts to have a good speaker design. You can always place a Hpass and Low pass on said drivers and see how it sounds but it might sound 10% of what it could. So just remember to take your time and slowly building your next speaker.

But ya I have four tens and two 10" mids needing to be used. So that will be part of my 3way. Will be a slow process but at this rate I think I might just go with 2way active.

Anyways I still dont see any finished pictures of this monster yet.
 
#28 · (Edited)
The model of the horns look pretty equal. Your JBL seems to be in large cabinet for the port tuning.

Anyways I still don't see any finished pictures of this monster yet.
Yeah, JBL is modeled in an 84L bass reflex, and I'm also modeling it in some smaller cab's with a bit higher tuning. It doesn't look as promising in the smaller cab's, really. I've got a fair bit of room under the credenza. I'm planning on building this with very generous porting, good damping, and yeah, I think I'll amp the heck out of it. I'm partial to the old QSC's, I've used several with very good results. The JBL used to serve as my midbass, running a bridged USA850 on it, in something like a 3 ft^3 cab, and even though with a miserly porting, it rocked! Cheap, dead reliable, what's not to like for a guy with a budget? And there's no hurry about it. Right now phantom is okay. But I think a beefy, well amped center would be a welcome addition.

Watched "Martian" tonight, and I may not have infra, but 20-80 hz is covered in spades. I set my receiver (Denon 3808CI) at -9dB and whew! -- a "moving" experience! Sub again just shrugged it off. I'll replay some of the more content-rich scenes and try some higher volumes. Pictures of Sue? Here's one. Oh, and my temporary speaker stands? Fine aesthetic, no? ;^)
I've got the speakers sitting on some bubble wrap to isolate them from the buckets, and the buckets are stuffed with a pillow each. In a week or two the fronts are going up on the wall. This project is still in its infancy. Be the trots to actually finish it, then what would I do? Heh heh ...
I love this horn!
EDIT: Added a comparison of this horn to the Othorn loaded with the SW152, both cab's at 1 watt into nominal impedance. Of course it's an apples and oranges comparison, given the huge difference in size, but ... this horn's sensitivity with that kind of extension is pretty noteworthy. It doesn't take a huge, expensive amp to drive it to crazy levels.
 

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#30 · (Edited)
Just for the sake of comparison, and again noting high modeled sensitivity yet with a -3 dB point ~21hz extension, here's what a watt will get you in my horn vs. the G-horn. Sue is no G-horn, but again pointing out economy of the design, this horn gets quite a lot of mileage out of modest input.

So as not to get carried away, I acknowledge this is comparing modeled behavior, and the G-horn is a proven design; mine is not. But, the comparison amounts to a fairly complex, $$$ design (using the TC 5400, which I gather is no longer available) with terrific performance when driven with a big, pricey amp (compared to anything I have), contrasted with a simple, relatively inexpensive build with darn good performance when driven with a Berry EP4000. An iNUKE 1000 would be sufficient to cause a ruckus

I will get my wireless issue sorted out tomorrow hopefully, so I can get the latest version of REW, and break out the UMIK-1. First goal is just some sweeps at the horn mouth to get an idea what the raw curve looks like. I'd like to get sweeps done at successive higher inputs, when I can figure that out. I seem to recall that the SubMaximus build thread had some good direction on how to get started with this ...

Size is going to be an issue with any center I build, or more properly the dimensions; 17h x 38w x 14d space available.
 

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#33 · (Edited)
Agreed, very similar. I think that for a single cabinet intended for dual role high level music playback/HT, it is a really pleasing compromise.

This horn turns out a slightly lower tune than modeled, but not by much; designed tune = 23.6hz, actual = 22.2hz

Comparison with Alpine SWS15D4 loaded Microwrecker ... same basic form, just a tad louder :cool:
 

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#34 ·
Got it measured!

I traded some mails with Lilmike and got lined out on REW and my PC, and got some preliminary sweeps done. He plans to massage the data, do some overlays, and get them back to me. I'll post everything as I get it. For now, it's better than my speculation. Nails 20Hz solidly before tapering off. Useable up to 150 with some good signal processing, according to Mike.

His first reaction to seeing the screenshot I sent him to confirm we were in business:
Lilmike:"Holy crap! That turned out better than I'd expected. I approve ... no wonder you like it."
Me: :laugh:

I also shot some video of cone motion during an energetic scene from Killer Elite; first onset of the explosion bumped the clip lights on the EP4000 pretty solidly, but that is it. Whew ... first time I've found those on a movie track. BUT, I can't load an MP4 format here. Is there another format I can save it in, convert it somehow?
 

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#35 · (Edited)
Here's a couple plots comparing the model to the measured results. This is not a 100% perfect comparison, as this sub is too big to be taken outside and measured groundplane, so it was measured nearfield. Though not a perfect setting, it is adequate to assess the results of the effort.



Not at all a bad result. The tune looks like it is little lower than predicted, which is also inline with the impedance measurements.



Nice work. Thanks for making the effort to collect some measurements of the result.
 

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#36 ·
Lilmike, the thanks are mine for all the help and encouragement. This has been a fun, fun project and my enjoyment of the system is just beginning. I don't have a moment's regret choosing this driver and pursuing this build. Both have a lot to commend them. Everything is a compromise and this is no different, but it is a very good one between extension and output, fitting a comfortable range that does the music/HT double duty well, for my uses at least.

It may be a while before I have any serious desire for more of either. SQ is excellent. What's not to love?:cool:
 
#37 ·
Here are a few more of the REW windows, with a little effort made to scale them. I'd be happy to get any impressions and interpretations anyone has to share. Lilmike has weighed in that the impulse, group delay, and distortion values are not at all bad:

"Waterfall is well-behaved in-band, no real stored energy except the 21 Hz fundamental and at the peak at 82 Hz. The peak is damped out by 400 ms, so not too bad. Otherwise quite good ...Group delay? Not bad, 70 ms at 21 Hz, 40 at 82 Hz, otherwise under 10. No complaints there."




For a simple build, it seems like a good return on both the $$$ and the low, low effort/complexity build. I did the build with no help, and not so much as a clamp or even a real sawhorse. To make up for the lack of clamping (the best I could anyways) I used a ton of PL 8X and a full box (1 lb) of #7, 2" Spax screws, in addition to a box of regular #6 drywall screws. I have pushed the enclosure pretty hard on some movie tracks (finally found the clip lights on the car bomb scene in "Killer Elite", but just bumped them solidly once), and it is holding together just fine. Egad, that was an EXPERIENCE and no mistake.

COST:

  • B&C 21DS115-8: $513.50, shipped
  • Lumber: Three (3) sheets 3/4" 4' x 8' Purebond birch plywood $149.54
  • Pl 8X, Kregs, Spax screws, 1 1/2" Drywall screws: $36.35
  • Behringer EP4000: $329.99, shipped (I already had mine)
  • $1,029.38
That is not all that bad for that level of performance, really. I consider it a very reasonable outlay. It offers good sensitivity and extension, and will handle enough juice to liven things up nicely. No mistake, I love it :) It is my initiation into a large horn-loaded enclosure, and it is the best sounding bass I've yet experienced in a home system. Period.
 

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#38 ·
How/where was that measurement made? Outside (quasi-anechoic?) or at listening position? If at listening position is there any room treatment?
 
#39 ·
donktard, the measurements were made with the horn mouth as close to the center of the media room as possible to get it as far away from reflective surfaces as possible. The UMIK was positioned on the floor, business end of the mic even with the horn mouth. The UMC22 soundcard was plugged directly into the EP4000 amp, so no (intentional) alteration of the signal at all.

I'd love to be able to take it outside and get some anechoic measurements, but a little history on the horn: I wanted a single large horn, and the simplest possible build. I wanted the Loud and Low elements of a system (the best compromise that could be reached at least), so the Iron Law meant "not Small." There is no way to move a large cabinet into/out of the basement due to dimensional restrictions on the old house ... just wouldn't fit. SO, it needed to be built in place, and thus one reason for the desire for a very simple/low-complexity build ... if/when I leave this place, it will simply have to be cut up and scrapped, so why do a fairly elaborate build like the G-horn, Lilwrecker or Submaximus? The time constraints of my school program (last semester toward a degree in Physical Therapy) were also a factor.

So I built it in place.

I am planning some measurements from my MLP this weekend, if I can. I'm interested to see what the room is doing to my signal.

No, it's not the sexiest system on this or any other forum and I could give a squat less. It is a very successful solution to my needs. And minus the cost of the amp and a few odds & ends like terminals and wire, the cost is ~$700. Given the sensitivity on the system, a person could go with a used good quality middlin' sized pro amp and get a ton of output. Attached is a screenshot of the system with 900 watts RMS that a used QSC 900 like I have sitting around, $129 delivered, would model in this system at 1340 watts peak (as per the rated 1.9dB headroom) This is a lot of performance for that price, if a person didn't have an issue with the size (and I don't, within reason).

Here is also a HR prediction of the system sensitivity compared to the well-proven Othorn. That kind of sensitivity approaching 20hz is pretty darn good. Othorn in gray, both systems at 1 watt into rated impedance.
 

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#44 ·
Deleted that weird link ... I was afraid to click on it lest I wind up in the NSA database and wind up with black heicopters paying me a 3 a.m. visit, ninjas fast-roping onto my roof ;-)

I'll try this again. I have a lot more work measuring at my MLP and around the room, as I'm interested in seeing what this horn will do with a little room gain (if there is any). This is three sweeps, two from my MLP and got some major floor - ceiling cancellation, and another position across the room at a comparable distance from the horn mouth.
 

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#47 · (Edited)
I tried many simulations, and to me it seems it only gives 3db more in part of the usable passband, if ever, while doesn´t gain ANYTHING typically under 50Hz in the same (small) box size. Only when it gets larger to a point, where the box volume of the bassreflex is rather "not suited" by conventional look of designing ported box, then tapped horn smights the BR box badly across the range, and even some more :)
 
#48 ·
here is a 420 liter tapped horn that is too small (ignore the stuff above 50hz as the horn isn't in anyway optimized) and a 420 liter ported, same minimum driver excursion. ds115 driver.


tapped horn picks up about 2.5db in the region just above tuning. this seems to always be the case.


of course, the bigger, the better.


 

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#49 ·
Yes. You picked wrong case again. 21DS115 is rather not supposed to work in the 420l box natively. It's really happy in 180-200l box. Now if you try to simulate that volume tapped horn, you get to my point. And part of it is, that I can get that box in the car myself. Pick and place, just like that. You propably cannot offer us Tapped horn solution like that, In that exact volume, which would overpower bassreflex box over most of its passband, and certainly not around br box tuning. Also I like to mention power density - yes, tapped horn is best in utilizing the driver, but you still can squeeze more SPL from the volume by other solutions. The Tapped horn is not really the most space effective thing. It is only most efficient per driver. Not a bad thing, but obviously not solution for every situation. If I could get more SPL at 25-35Hz from TH at my box volume, I would jump on the other solution. But there is none to date.
 
#51 ·
remember that the 420 liters includes the volume of the port itself, so that must be subtracted for an apples to apples comparison. in order to keep port velocity low, a large port and/or large cab is required, or there can be compression. 200 liters is a little on the small side for this driver from that angle, so right away the 200 liter cab increases to 280 liters with the port volume included and that is for a cab that i would consider of borderline design.


whether a big ported cab is "not suited" to your design taste is purely your design taste. i was just trying to show a comparison of a ported cab vs. a tapped horn cab within what would be considered getting the most out of the driver in the ported cab. in this case that is a cab that is about 330-360 liters with another 50-60 liters for port volume, hence the 420 liter cab.


i don't disagree that ported offer greater power density, but density alone doesn't equal output. so if you stuff more drivers into the same space, you get more output, but then you also need more amps, power, etc.


if you have limited money and space, then perhaps choosing a driver that could work in a tapped horn that fits in your space is something to investigate.
 
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