Even though it's a bit more money, I'm leaning towards the 15" afterall. From my reading, that "crack in the chest" impact may be more in the 60-100hz range, and not as low as I thought. If it's not 130db at 35hz it's not the end of the world. And since it's a 20x25 room I may have enough room gain that that's not an issue anyways.
Thanks for all the help and discussion. I may start a new thread for the build or put it in here if it's more applicable. Thx guys
Thanks for all the help and discussion. I may start a new thread for the build or put it in here if it's more applicable. Thx guys
Not sure how to interpret the formulas I have, i.e. don’t know how the various constants were arrived at, though I’m thinking it’s constant.
There are different ones for the front [Mmf] and rear [Mmr] on a baffle Vs the one for free air [Mair], then the air mass load change [Mch] = [Mmf+Mmr]-Mair and Mms-Mch = Mmd.
Calculating the 12D2’s Mms from the HR specs to find Mmd, I get a slightly higher 157.6 g Vs HR’s 157.48 g, though no clue why I’m off unless the constants were derived using a different SoS, p0 specs.
GM
You're welcome!
According to an old Klark-Technik chart, chest 'thump' is in the ~20-35 Hz BW and 'boom'/'punch' is in the ~100-180 Hz BW and large venue prosound apps historically have been ~flat from 60-300 Hz, -24 dB/~40 Hz, so for large room, outdoor apps the 20-300 Hz BW needs to be up to +6 dB referenced to the mains.
GM
Room gain [as opposed to local boundary gain] doesn’t begin till below the room’s 1st axial mode or ~565 ft-sec/25 ft = ~22.6 Hz, rising at up to 12 dB/octave depending on the room’s construction; so in many cases there won’t be much, if any, useful gain in a room this large unless the audio system is designed for low B pipe organ symphonies, movie LFE soundtracks.
GM
Update………… djk reminded me here that some audio descriptions have either changed over time or being misused, so………….
According to an old Klark-Technik chart, chest 'thump' is in the ~20-35 Hz BW and 'boom'/'punch' is in the ~100-180 Hz BW, with ‘whack’ in the ~800-1600 Hz BW, so make sure you have plenty of 'clean'/'fast' dynamic headroom in this mids BW to EQ however much kick drum 'punch' you want.
GM
well the entire room is 20x25, but there is an isolation room that takes up about 1/4-1/3 of the room. With vaulted ceilings however, you're right there may not be tonnes of room gain.
So I've been amazed at all the info on tapped horns and am trying to put something together for a friend of mine who is doing a live music/recording/home theater room.
Requirements:
Room size is 20' x 25'
Mains cover down to about 55, but for the levels we want, we'll probably cross around 75 or so.
It will be used 80% for live recording/rehearsal and mix review. the other 20% will be messing around with a home theatre.
The main objective is to have a serious amount of impact and "feel it in your chest" type bass (similar to what you might get at a night club venue). I figured somewhere in the 130db range would be nice.
The Alpine SWS-15D2 looks very appealing based on what I've seen what with the Xmax and Klippel and general good build quality. I remember having one back in the day. One thing no one has mentioned is that I believe them to have very stiff cones. Should help with the compression loading. I know "very stiff" isn't exactly scientific, but rigidity wise I'm sure it's loads better than things like the Dayton Reference, Pro audio PA cones, and poly cones and such.
Anyways, this is a design I've come up with so far. Any thoughts or analysis would be great. I may have missed a few things.
That's with 500 watts I believe.
First off, I gotta commend you Canadians. You sure love bass!
Some thoughts about the Alpines:
1) I've built a few tapped horns with the Alpines. As I type this I'm sitting on a dual SWR-824 tapped horn that's loosely based on the Insubnia. (It's basically two Insubnias mirrored in a single cabinet.)
2) All of the Alpine Type R woofers have similar specs. So you can 'dial in' the F3 by choice of driver. For instance the 8" has an FS of about 40hz, so it's well suited to a 28hz tapped horn. (FS * 0.707) One problem I saw with the twelves and the fifteens is that the low frequency cutoff gets TOO low. For instannce, if I used the fifteen, I end up with an F3 below 20hz. (I personally prefer an F3 between 30 and 40hz because there isn't much music content below 30hz. YMMV.)
3) I really like the effect of push-pull. I was cranking some Excision in anticipation of tonights show in Los Angeles. My dual 8" tapped horn is so clean, I wasn't 100% sure that it was turned on! Basically I have three subwoofers, and the TH was so much lower in distortion than my other two subs, I was a bit worried that it wasn't even running. My other two subs use fairly ordinary eights, one is a KEF, the other is an MCM 55-2421. So I stuck my hand in the box to see if I could feel the cones moving, and promptly got electrocuted by the plate amp. OUCH
TLDR: You might consider running two twelves push-pull, or even dual tens. The reduction in 2nd harmonic is noticeable.
Dig around on this forum and you'll see a few threads that I started about Alpines in a tapped horn. The one that would be particularly useful is the one where I compared it to the MTX 9515 that's used by Danley in the Matterhorn and a few of his commercial subs.
There's gotta be a thread dedicated to that subject, but here's some things that can help with effect, IMHO:
1) I think a big part of that effect is getting the distortion low enough so that you can crank the subs up really loud. For instance, if you're using a cheap MCM driver and you play 60hz, the harmonics at 120 and 180hz may be very loud. Due to those harmonics, you may be inclined to reduce the volume on the sub. And you can't *filter* those harmonics electronically. So you reduce the volume on the sub because the disortion is muddying up the octave from 100-200hz, and then you miss that 'impact' at 60hz. I noticed this with my dual Alpine TH; the only limit to the volume is how much my neighbors will tolerate. No muddiness from 100-200hz.
2) Another part is measuring the room and EQing it. As noted above, the octave *above* sixty hertz can affect the sound of the fundamental. IE, if you have a room mode at 150hz, you may turn down the sub to reduce that mode. The best solution is to EQ it out, move the sub, get more subs, etc.
3) One thing that I'm exploring is whether front loaded horns have more 'impact' than THs and BLHs. I've read this on forums, so I'm building a FLH with a TC Sounds eight to find out. The Alpine 15" would make a great candidate for a big FLH. In fact, it's probably better suited for a FLH than a TH, unless you need ultra low LFE (which you might, depends on application.)
FLH
Hi there P: In the late 1950's Radio Electronics ran an article about a short straight horn for 15-inch driver. The horn section was square while the four sides were curved and constructed from Portland Cement plaster (over steel mesh...that was a normal material used for house interior walls, prior to the wide spread use of dry wall). I do not recall the Fs of the driver used. I would imagine that a mid low (Fs about 25hz) driver like Alpine R or JBL GTO would work in such an enclosure. ...regards Michael
Hi there P: In the late 1950's Radio Electronics ran an article about a short straight horn for 15-inch driver. The horn section was square while the four sides were curved and constructed from Portland Cement plaster (over steel mesh...that was a normal material used for house interior walls, prior to the wide spread use of dry wall). I do not recall the Fs of the driver used. I would imagine that a mid low (Fs about 25hz) driver like Alpine R or JBL GTO would work in such an enclosure. ...regards Michael
Hi there! I am watching this thread with interest. Like Mtnickel, I am new to the idea of building a TH. My goals are a bit different; I don't really even have a "need", hardly even watch home movies but want to try my luck at building a huge monster that will dip well into the teens. Why do it then? For the same reason a dog licks his balls*.
Based largely on advice from here and another audio site, I plan to (ab-)use the similar to Mtnickel's choice (did you stay with it?) the Alpine SWS-15D4 (in my case). Especially since a pair of them can be had for around $230 on Ebay. Of course I'm taking a chance they are counterfeit, or returns, or b-stock or maybe the prior model. But I'll take the risk. Thanks to Patrick Bateman especially for his many posts on TH and Alpine drivers. I will try the "push-pull" since it sounds like a valid idea and only slightly complicates the build. I still haven't finalized a plan but will take my time and this time, will ask for the blessings of the elders before buying wood 🙄
to minimize the odds that I will be
If for some twisted reason of your own, I invite you to look at my own posts here, if for a negative example if no other reason!
*"Because he can."
Based largely on advice from here and another audio site, I plan to (ab-)use the similar to Mtnickel's choice (did you stay with it?) the Alpine SWS-15D4 (in my case). Especially since a pair of them can be had for around $230 on Ebay. Of course I'm taking a chance they are counterfeit, or returns, or b-stock or maybe the prior model. But I'll take the risk. Thanks to Patrick Bateman especially for his many posts on TH and Alpine drivers. I will try the "push-pull" since it sounds like a valid idea and only slightly complicates the build. I still haven't finalized a plan but will take my time and this time, will ask for the blessings of the elders before buying wood 🙄
to minimize the odds that I will be
If for some twisted reason of your own, I invite you to look at my own posts here, if for a negative example if no other reason!
*"Because he can."
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