I've been nursing this idea for a little while and decided to run it past you folks.
Put the Beta 12LTA on an open baffle and allow it to run full range. cross the Beta 12A-2 in at around baffle step. Some super tweeter could be used for the top end; take your pick. I'm expecting that this arrangement would still need EQ to get a decent balance, as well as extend the bass (neither is a particularly high-Q woofer). But I have two questions: since the combination of two 12" drivers will have more surface area than a single 15", will these drivers be capable of decent SPL levels, despite one of them being used full range? And with EQ, will they be capable of reaching 40hz without too much distortion?
Put the Beta 12LTA on an open baffle and allow it to run full range. cross the Beta 12A-2 in at around baffle step. Some super tweeter could be used for the top end; take your pick. I'm expecting that this arrangement would still need EQ to get a decent balance, as well as extend the bass (neither is a particularly high-Q woofer). But I have two questions: since the combination of two 12" drivers will have more surface area than a single 15", will these drivers be capable of decent SPL levels, despite one of them being used full range? And with EQ, will they be capable of reaching 40hz without too much distortion?
I'm running a pair of 12A-2's to meet a Beta8A at 240Hz in a 2x4' baffle. The 12's have current feedback in the amplifier to set the total Q to around .7. There is also 6dB oct baffle compensation on the 12's. The output below 47Hz with q=.7 is of course limited by driver resonant frequency but it really doesn't sound like it. There's good 40Hz available. I'm sure it depends a lot on baffle and room. I never did get outside yet to get good low frequency response measurements.
This is only a temporary arrangement for me as subs will eventually be added and the 12's will only go down to 70 or so. Distortion all depends on how loud you need it, although I must say, they do rock pretty good with just 25 watts. I started with the 12A2's going up to 400Hz and I didn't appreciate the sound at all.
This is only a temporary arrangement for me as subs will eventually be added and the 12's will only go down to 70 or so. Distortion all depends on how loud you need it, although I must say, they do rock pretty good with just 25 watts. I started with the 12A2's going up to 400Hz and I didn't appreciate the sound at all.
You were thinking of running them both full range, no crossover? Andrew's post indicates that while it might work, it won't sound great. That would be my take on it, too.
I think I said the 12A-2 would be crossed in at baffle step; I figured it should be rolled off with the help of an inductor at least. So in effect I'm proposing a 1.5 way.
OK, got it. Since we are here on the fullrange forum I was thinking no crossover. Sorry
Running the 12A-2 as a helper woofer should work OK once you figure out the inductor needed. It may be bigger than you suppose because there is such a rising response on OB.
I've only heard the 12LTA as a wide bandwidth OB midrange. It was very, very good at that job.
Running the 12A-2 as a helper woofer should work OK once you figure out the inductor needed. It may be bigger than you suppose because there is such a rising response on OB.
I've only heard the 12LTA as a wide bandwidth OB midrange. It was very, very good at that job.
found it. it was john busch's system you heard, right? what a monster! lots of good info in that thread.
Beta 12-lta question.
Beta 12-lta question.
There's no question the 12lta is a great wide range midrange on an open baffle in my mind... I am currently building a powered sub using a 12" driver in a sealed box. I hope it mates well. Getting the bass right is critical with any system.
Yes, that was the one. Good find! John's not afraid to use double 18s for bass. 😉
If I were trying this double beta setup, I'd run just the LTA on the baffle and measure how it drops off in the bass. That would give a good idea of how much the low end needs to be filled in. Since the 12A-2 is going to have a similar response that gives you a good idea of how big an inductor is needed to restrain the 12A-2 to the "fill in" range. Then start fine tuning coil and cap.
It may never be a perfect match, but having that extra driver down there to help the LTA will sure make it sound more balanced. Just my 2 cents.
If I were trying this double beta setup, I'd run just the LTA on the baffle and measure how it drops off in the bass. That would give a good idea of how much the low end needs to be filled in. Since the 12A-2 is going to have a similar response that gives you a good idea of how big an inductor is needed to restrain the 12A-2 to the "fill in" range. Then start fine tuning coil and cap.
It may never be a perfect match, but having that extra driver down there to help the LTA will sure make it sound more balanced. Just my 2 cents.
I also wonder how the open baffle hump might be used to help balance the response of the 12LTA when run full range. According to MJK's graphs baffle hump is around 3db, which if centered around 500hz could fill in the 12LTA's response quite a bit. The phase plug mod would smooth out the top end even more. After that, maybe the best idea is just to buy a sub plate amp and cross a pair of woofers in around 100hz. Thoughts?
For that matter, I have a pretty decent sealed sub in storage. While it's my impression that open baffle bass is at least half the reason to go open baffle in the first place, it might allow be to get started using 12LTAs right away...
For that matter, I have a pretty decent sealed sub in storage. While it's my impression that open baffle bass is at least half the reason to go open baffle in the first place, it might allow be to get started using 12LTAs right away...
Chaz, according to XLBaffle the Beta 12lta has solid output to about 150hz on a 2' x 2' open baffle. On a 4' tall by 2' wide ob it's got solid output to about 100hz. You will get a generous helping of that open baffle quality for sure. I do feel the 12lta is an exciting driver to listen to stock but removing the dustcap reduces the main coloration it has. Adding the phase plug (i will have to measure mine so you can duplicate it using a dowel from Home Depot or just purchase a pair from Planet 10 if you have extra $) smooths the response making it very listenable for extended sessions. One thing that makes this driver different for me is that regardless of music (rock, classical, jazz, folk, etc...) it always sounds good. This is not always the case for other drivers I have.
I have them on 2' x 2' baffles. Under H-frames they are amazing. Currently they are standing alone playing music (sounding good except for lack of bass) awaiting a typical sealed 12" powered sub. I will let you know how it all works out but i expect it to be very good. But i don't expect the sealed sub with one 12" driver to be as good as the H-frames comprising of two 15" drivers. In each case, i am powering them with the same subwoofer amp and dialing in the bass to taste.
Funny thing about XLBaffle is that you don't enter the Qts... but we use this spec to determine a drivers suitability on open baffle. Can someone explain why? Also, since we know we will be providing bass support this largely eliminates the need for drivers with Qts around 1 opening up a range of possibilities for us all to enjoy open baffle sound. Of course using high Qts drivers for producing low bass is useful when not adding EQ.
I have them on 2' x 2' baffles. Under H-frames they are amazing. Currently they are standing alone playing music (sounding good except for lack of bass) awaiting a typical sealed 12" powered sub. I will let you know how it all works out but i expect it to be very good. But i don't expect the sealed sub with one 12" driver to be as good as the H-frames comprising of two 15" drivers. In each case, i am powering them with the same subwoofer amp and dialing in the bass to taste.
Funny thing about XLBaffle is that you don't enter the Qts... but we use this spec to determine a drivers suitability on open baffle. Can someone explain why? Also, since we know we will be providing bass support this largely eliminates the need for drivers with Qts around 1 opening up a range of possibilities for us all to enjoy open baffle sound. Of course using high Qts drivers for producing low bass is useful when not adding EQ.
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A plate amp for the bass diver is a good idea. I've done it, it works. You may still need an inductor after it, you'll have to try it and hear.
Godzilla. I think that XLBaffle figures Qt from the Qe and Qm you supply.
Godzilla. I think that XLBaffle figures Qt from the Qe and Qm you supply.
Thanks for the feedback Zilla and Pano! Zilla, I think if I were to implement the 12LTA I would probably make a 2'x3' open baffle to keep the height relatively modest. Already I'm probably in dangerous territory WAF-wise, pondering 12" full range drivers! 🙂 I can just hide the sub behind one of the panels until I invest in an OB bass solution. And what about the Apexjr tweeters for a cheap tweeter solution?
"This tweeter measures very well and is by far the most dynamic non-horn-loaded tweeter that I have encountered thus far with whopping 96db@1m/2.83v senitivity coupled with excellent power handling and best used with a 3Khz crossover."
"This tweeter measures very well and is by far the most dynamic non-horn-loaded tweeter that I have encountered thus far with whopping 96db@1m/2.83v senitivity coupled with excellent power handling and best used with a 3Khz crossover."
Is that tweeter 4 or 8 ohm? Eff seems high. The 12lta is clearly more efficient than any of the fostex drivers I have rated in the mid 90s.
Pano, what's the inductor for?
Pano, what's the inductor for?
The inductor changes the 2nd order low pass (built into the plate amp) to 3rd order. Can be useful with lower Qts drivers on OB.
It's 4 ohms, but yes, it is unusually high. The ideal tweeter choice would obviously be the fostex FT17H; but at $15/pair, if that sensitivity is true then it seems like a good way to get something going on the cheap!
If the tweeter is 96db at 4ohm it's only 93db at 8ohm... i am not sure it will provide enough output partnered with the 12lta... But... have a look at these!
Peavey Super Tweeter Pair Aluminum Housing
I think they would do the trick.
I use these:
Eminence ASD1001 1" HF Titanium Horn Driver 1-3/8"-18 TPI
plus these:
Dayton H45E 4.5" x 4.5" Elliptical Waveguide 1" Threaded
Along with a 1uf cap... but you can use 1.5 if you prefer more treble or .68 if you prefer less.
For the price i'd give those Peavy's a shot. They're keeping with the pro sound motif and extend to 25k (so the spec says). But the efficiency is spot on. I'd say start with a 2uf cap on the Peavy's and work your way up or down in .5uf increments to find the perfect blend.
Just my two cents.
Peavey Super Tweeter Pair Aluminum Housing
I think they would do the trick.
I use these:
Eminence ASD1001 1" HF Titanium Horn Driver 1-3/8"-18 TPI
plus these:
Dayton H45E 4.5" x 4.5" Elliptical Waveguide 1" Threaded
Along with a 1uf cap... but you can use 1.5 if you prefer more treble or .68 if you prefer less.
For the price i'd give those Peavy's a shot. They're keeping with the pro sound motif and extend to 25k (so the spec says). But the efficiency is spot on. I'd say start with a 2uf cap on the Peavy's and work your way up or down in .5uf increments to find the perfect blend.
Just my two cents.
Phase plugs
Hey 'Zilla! You still using those phase plugs i sent you?
I think yours are 40mm dia and the second set I had made are a tad wider at 44mm dia. Mine are then 62.5mm long and about 38mm before the transition if that helps
I used some measurements posited by Dave Planet10
Not sure how much the length affects the sound but heres some measurments
http://www.diyaudio.com/forums/full-range/179161-beta-12lta-3cf-box-port-size-10.html#post2429767
Hey 'Zilla! You still using those phase plugs i sent you?
I think yours are 40mm dia and the second set I had made are a tad wider at 44mm dia. Mine are then 62.5mm long and about 38mm before the transition if that helps
I used some measurements posited by Dave Planet10
Not sure how much the length affects the sound but heres some measurments
http://www.diyaudio.com/forums/full-range/179161-beta-12lta-3cf-box-port-size-10.html#post2429767
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