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Received a suggestion on another board to take Inlow Sound's 130 Hz midbass horn lower by using 2 8PE21 drivers. I would ideally like to get down to 90 Hz, but 100 Hz would also be ok. The midrange compression driver I am currently planning to use above it is TAD 4001 crossed over ~ 500-600 Hz. But also looking into GOTO lower midrange compression drivers.The upside is we're planning to have a large dedicated listening room built into our next house, so the depth of the horn is not really an issue. Vertical real estate is a bit more pressing since I don't want the speaker to be a towering giant.
Any thoughts, ruminations, "don't do it!" or other advice? How do you guys think the pattern of such a midbass horn would be working that high into the midrange?
Edits: 03/11/16Follow Ups:
A pair of 12's in a compact horn with good mid response, use-able from 90hz to beyond 800hz or so. Very low distortion due to the initial conical expansion.
Edits: 03/15/16 03/15/16
Do you find any sound quality difference in using one driver in a horn versus two?
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Big speakers and little amps blew my mind!
The second (large) driver allows the horn to be much shorter for the 90hz cut-off.A single 8 would be fine if size were not an issue.
I first built a double 12 horn in 1981, it sounded incredible (compared to the usual A7/4560 type designs we were dragging around).
The funeral for the 4560's (and EV TL5050's).
Edits: 03/15/16
Would the cut list linked below work with the B&C 12pe32? I'm not sure how to read & figure out hornresp to make a cabinet with the data you have graciously provided above.
Cheers
Frank M
Dennis,
Have you ever tried to drive a mid-bass horn with a ppsl driver orientation verses the dual front firing method ?
The upper limit is the depth of the plenum.
I have a new idea which will eliminate this issue, but I have not tested it. It involves a bifurcated horn throat (like a LaScala) with only a single smooth 90° bend per half(not un-like the old WE horns).
Come to think of it, didn't you already do a LaScala type device loaded with ppsl ?
Yes, with quad SEAS 8's.
It sounds quite good, much better than the standard 15 in the vented LaScala cabinet. The bull-nosed horn was next, it has the same basic size as the Belle. I tried the Silver Flute 8's, but the SEAS work better.
With the SEAS raw room and EQ'd response, about 6dB of boost to make it to 27~28hz or so. The plenum depth dictates a 400hz HF crossover (BMS co-ax).
The dual 12 PPSL is for use with a sub, and to see how much bandwidth I can get.
OK, so the plenum depth null isn't solved by horn loading. 30-400hz is still an excellent range, as is 100-900.
With the dual 12" bulk size at 16 cubic foot at least two 15s could be added below 100hz, maybe even low eff high power high xmax subs.
"With the dual 12" bulk size at 16 cubic foot"
It's much smaller than that, IIRC only about half that bulk.
You did ask.
It's possible that using the Inlow 100hz horn would do a better job at going to 100hz that the doubled 130hz horn. It goes up to 500hz well. If you want down to 90hz, then he has an 80hz horn, but it only goes up to 400hz, and throws you out of whack with your mid horn. Nothing wrong with a sub from 100hz on down. You could make it a horn sub if you wanted to go all the way. Bill Fitzmaurice comes to mind.
If you crossover at 500hz you have a lot more choices with horns and drivers than 400hz. Also, 400hz pretty much guarantees a three way plus sub. Still it has it's charms.
Think twice about GOTO. I'm sure they're great, but their mouths are only three quarters on an inch. For a mid or mid-bass driver that's archaic. It guarantees a long hyperbolic (which is exactly what GOTO horns are) profile which is going to be high distortion, and that's not going to sound very good. Sometimes the Japanese worship a little too devoutly at the alter of WE. John's suggestion of using the Le'Cleach profile would be making the best of that bad situation.
Have at it!
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Big speakers and little amps blew my mind!
Yes, that is a very good point about the GOTO drivers small exit. There are a couple of people that have used them with more modern horn profiles with throat adapters. For my intended use I would only be using them from about 500-600 Hz on up, no super expensive 4" exit midbass compression drivers for me :) I will probably only look to GOTO after trying others out (or skip them altogether). I do have a bit more leeway since I am doing this multi amped and via DSP.
The reason I was looking into a scaled up 135 Hz horn is an 8" driver has lower moving mass plus should work better into the midrange over the larger drivers.
hottattoo I just re-read your comment about Cessaro, aren't they using tractrix horns for midrange on up?
hvbias,
Cessaro uses a spherical horn profile. My friend is the USA importer for Cessaro and I help him set up at audio shows. Do a search of the Rocky Mountain Audiofest from 2 or 3 yrs ago for some pictures. The mid range horn is about (my guess) 24" diameter and about 18" deep but weighs approx 175 lbs !!! and over 1000 lbs per channel. Some kind of special resin concrete--a bitch to lift up and install needless to say.
The 135hz horn? Lower on his web page, he takes four drivers per side, adds some size and gets it down to 105. Likely with corner placement, as his sims usually are.
He has a sim for a version down to 80, but from his description I think he EQs it?
hvbias,
If you are going through the trouble of building / have made a mid bass horn then build a proper horn for your desired low end frequency. The larger the horn the better, you should be able to scale up john's 135hz horn but you will have to run the numbers to see if it gets to your goal.
The TAD 4001 is an excellent driver--but do NOT put it in a round tractrix horn (from personal experience) as it will sound bright and forward sounding --it needs a TAD designed (or copy)axial horn to sound best. I much preferred the sound of the JBL 2441 with beryllium diaphragms installed in a round tractrix horn. Cessaro uses the 4001 but in a large, heavy, super solid spherical horn and it sounded excellent.
Goto makes some very impressive and expensive drivers but they are mostly used in 5 way systems where the individual drivers are used in fairly narrow frequency ranges--and you MUST use them with the proper Goto horns for the best sound (according to mfg). I have heard a Goto horn set up at the Capial Audiofest several years ago and found them to be very detailed, dynamic but slightly bright. Another potential problem is you will have to send these drivers back to Japan if you have any driver issues. Just my opinion and 2 cents.
Comparison between TAD TD4001 and JBL 2441 BE in 290 Hz (16") Sierra Brook tractrix horn in 500-3k range was not favorable to 2441BE . It (2441BE )sounded like half of the driver , shy, anemic slightly lifeless. It was however much more pleasant , spacious and even if used "full range" Maybe magnet on my 2441 is weak ? Tad sounded , rugged, energetic hate that word but it fits the character -"punchy" , just alive. It sucked used full range. After half an hour I had the desire to take the axe and chop it off the horn.
I'm not sure if I will end up using the TAD long term. When I heard them in large JMLC horn they were first order crossed at 700 hz and sounded fantastic. I've never heard any compression driver sound good down to 500 Hz while still having some "meat" to the sound. It's looking like 400-500 Hz that I may need to hand over to the compression driver if I want to keep good fidelity with a ~ 90 hz midbass horn.
JBL 2490 looks like a good candidate, but that titanium diaphragm (though it may not be an issue in the lower ranges I want to use it at). I asked Radian if they would make me a one off Be, they must have thought who is this joker :D JBL CMCD-61 is looking like another attractive option.
Wojciech,
My Tad 4001 experience on a 13" (Dr. Bruce) salad bowl tractrix horn is similar to yours, very detailed, lively, but OMG, my ears were about to bleed !!! I tried twice to listen to this combo but gave up. I traded the tads a friend who bought a pair of proper Tad wood horns and it now sounds excellent.
The JBL 2441 with Truextent Be diaphragms and re magnetized motor were much better then the Tads on the salad bowl horns. They were clean, clear, nice tone, excellent imaging, nice high frequency extension BUT you had to get the EXACT placement / distance to ear from the horns perfect or you lost the image pronto !!! The head in a vice comes to mind.
I now use a field coil converted JBL 2441 with Be diaphragms on a 25.5" ( 200hz. ?) heavy mahogany Sierra Brooks tractrix horn---my search for a great mid range driver /horn combo is OVER !!! I now have a sweet, clean, clear mid rang with excellent tone from 450hz to 8k. I use a Lambda lp-531fm variable power supply (0-20volt) set to 14 volts and kick back. I have heard lots of drivers including the Cogent field coil drivers (excellent) and want for nothing. There may be better more exotic drivers (GOTO,ALE etc.)out there but I will never know !!!
Wondering who did the field coil conversion and exactly
what is the difference in sound.Also, did you compare the
Be to the Radian diaphragm ? Thanks for any info.
I have no experience with the JBL field coil conversion, but if you haven't seen Joe Roberts' post on field coils I found it interesting. Link attached below.
Thank you for your post. I will send 2441 to good folks at GPA to get them recharged.I was little disappointed that truesound BE diaphragm with mylar suspension compares so miserably to stiff TAD's roll off surround in low midrange performance when crossed at 500hz 6db.
Just a quick comment - almost all your observations on things sounding bright is just an indication that the systems did not have the correct EQ applied in the course of designing the system. I should know - the Goto system you heard was likely the one I designed. I would do the EQ a bit differently if I had it to do over again.
On the Goto drivers on their horns issue, their LF horns are fine but the high frequency ones could be improved by switching to Le Cleac'h horns or something else with a round over at the mouth. Just be aware that none of their drivers have anything close to flat response on their horns and will require tons of crossover work to get them to integrate well. The 1st order crossovers they suggest do not work - they give system response with a bump of ~15dB between 200Hz and 5kHz relative to the bass and highs. But if you can make their drivers work in your design, they can sound amazing.
To the original poster, if you put drivers with more volume displacement on a horn and EQ it up below the horn's cutoff, you'll get output there but it's just a sealed box at that point. As others have said you'd be better off building a bigger horn if you have the space. For your midrange horn, if you want a 500Hz crossover, you'll probably want at least a 250Hz horn. Stored energy increases as you get close to the horn horn's cutoff. For example, in my system I have a 3" JBL driver on a 385Hz horn that I crossover at 800Hz due to stored energy increasing below there (among other reasons). It's usually tough to build a big enough midbass horn to continue following this rule, but in the mids and highs it is possible to do so.
Thanks for the advice John, wish I could have heard the setup you helped build at Capital Audio Fest.
Thanks for the advice hottattoo. I've read TAD are nasty in Tractrix as well, haven't completely decided where I am going to go with it. I won't have a problem selling them if they don't work out. Community M200a are another cheap driver that interests me.As for GOTO I plan to try out older models second hand (I have some friends in Japan that can help out) before springing for their current high end Be. I'm also doing this with digital/DSP correction so I have a bit more headroom in playing with overall system response.
Edits: 03/11/16
build 2 stack them
hvbias,
I would look into a used pair of EV Dh1a compression drivers. You can find them pretty cheap on ebay and diaphragms are available. They are an excellent sounding mid range driver.
I'm no experienced horn builder, please excuse the dumb question- wouldn't the biggest difference be in efficiency with a slight increase in low end extension since the horn length stays the same and a second 8" driver doesn't add that much surface area?
I was under the impression to hit 90-100 Hz even with two drivers the horn length would have to be scaled up quite a bit as well?
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