Well, I've definitely decided to move on from yet another attempt to build a speaker to suit my particular design goals. Toe failed attempts and many many hours. But I don't feel badly at all, because I've been learning a lot, very much thanks to members of this forum, so thanks to all who've contributed and helped me learn a little more about this dark art. My respect grows with every step and everything I read.
So, my next go will be with the Faital Pro 15POR400, a time tested winner. I've looked around, and this driver seems to be the perfect fit. With any luck I won't have to stomp on it too much with the crossover and hope to end up in the mid 90s for sensitivity (rated at 100db). I plan to pair it with the Faital HF140, a 1.4" CD with excellent FR especially high treble, which will be great to start with as I expect the FR to suffer a bit above 15k from the horn. I'm looking at what's available for tractrix horns, and can either go with the stock Faitals, which are a bit modified but inexpensive, or my real heart throb, the GPoint Audio Tractrix 350. My only question right now is whether to go with the 8ohm or 16ohm CD for use with my tube amps. Pics of the horns below, first is the Faital, second the GPoint.
So, my next go will be with the Faital Pro 15POR400, a time tested winner. I've looked around, and this driver seems to be the perfect fit. With any luck I won't have to stomp on it too much with the crossover and hope to end up in the mid 90s for sensitivity (rated at 100db). I plan to pair it with the Faital HF140, a 1.4" CD with excellent FR especially high treble, which will be great to start with as I expect the FR to suffer a bit above 15k from the horn. I'm looking at what's available for tractrix horns, and can either go with the stock Faitals, which are a bit modified but inexpensive, or my real heart throb, the GPoint Audio Tractrix 350. My only question right now is whether to go with the 8ohm or 16ohm CD for use with my tube amps. Pics of the horns below, first is the Faital, second the GPoint.
Don’t give up the coax just because of some odd looking graphs. Build them both and make a simple crossover with a small dip around the crossover point using perhaps first order 500hz on the LF and 2nd order 4000hz and start play around with variable L-pad and your favorite music. It will measure/simulate strange and maybe not present the best vocals but try and listen and tweak by ear. Invert phase on HF and try again. I’m sure you will be surprised. Flat response is over rated, the goal must be to tame the mid a little.
Giving up already?
Just based on few measurements and sims?
First, coaxes dont have flat response. But many speakers sounds much better than their response looks on paper. Nice looking response is not the ultimate measure of quality.
Second, if you want a better looking response at least try to design more advanced crossover.
I traced FRD/ZMA files from beyma datasheet and made this crossover. Second order electrical, third order
acoustical. Fairly simple and straightforward with standard component values.
Notch filter for HF is to smooth up the 2-4kHz bump. Its important that total resistance in notch circuit
(resistor + DC resistance of inductor) is as close to 3,5ohms.
Dc resistance of 3,3mH inductor no more than 0,5 ohms. 1,5mH inductor no more than 1ohm.
If you take 95dB as reference, final response is within +/-3dB, except for small dip at 5,5kHz and rise above 15Khz. if you want, you can smooth up the rise with 2,7uF cap across tweeters terminal. The effect is shown in dotted line.
Those beymas are really nice drivers. Unfortunately, days when I could afford to play with something like that are gone. So, please show some more diy spirit and try this before you give up.
Just based on few measurements and sims?
First, coaxes dont have flat response. But many speakers sounds much better than their response looks on paper. Nice looking response is not the ultimate measure of quality.
Second, if you want a better looking response at least try to design more advanced crossover.
I traced FRD/ZMA files from beyma datasheet and made this crossover. Second order electrical, third order
acoustical. Fairly simple and straightforward with standard component values.
Notch filter for HF is to smooth up the 2-4kHz bump. Its important that total resistance in notch circuit
(resistor + DC resistance of inductor) is as close to 3,5ohms.
Dc resistance of 3,3mH inductor no more than 0,5 ohms. 1,5mH inductor no more than 1ohm.
If you take 95dB as reference, final response is within +/-3dB, except for small dip at 5,5kHz and rise above 15Khz. if you want, you can smooth up the rise with 2,7uF cap across tweeters terminal. The effect is shown in dotted line.
Those beymas are really nice drivers. Unfortunately, days when I could afford to play with something like that are gone. So, please show some more diy spirit and try this before you give up.
Wow thanks for all the input guys, and Especially you Davor for taking the time to model the crossover.
I will have another go at the crossover this weekend (killer work week), but I have to say first of all that my measurements aren't as friendly as Beyma's, although from 500Hz down the tuning on mine is fantastic.
I did get spooked, not just from my frustration at making a nice looking graph, but after an accumulation of some concerns other members have voiced about some of the drawbacks of coax design, especially with a 15" cone.
Another thing I'll mention is that Al at US Speaker is a champ and is willing to take the Beymas back minus an open box fee which is very good of him. So it's not like I'm stuck with these drivers and need to make something out of them just because I own them. I still have my 10" Radian coaxes from my first failed attempt that I'm thinking about for a future build if my buddy doesn't buy them. I can't afford to have extra stuff around either!
But the horn-on-box is so classic, and my buddy Cam found Martin Seddon's site after reading one of the threads here, and I have to say I'm really smitten and his horns are beautiful. The esthetics of a La Cléache horn crowning a well made enclosure are hard to resist, and my lady is very excited too, so.......but beyond esthetics, I think I can achieve a better sounding speaker with less issues using the Faital PR400 and a top horn. This arrangement also has the advantage of swapping out CDs over time, and with an external crossover changing a few parts isn't the end of the world.
My takeaway is that coaxes are very challenging but can be very rewarding if you get it dialed in, and horns on boxes are challenging in other ways but maybe don't have some of the built in disadvantages of coax drivers.
The last thing, and it's very important to me, is I will probably achieve noticeably higher sensitivity with the Faital (100db) and Martin's horn, as well as much better directivity. Davor's crossover is probably about as good as it's going to get as far as parts go, but with the Beyma I'm starting at 96db and will probably end up in the low 90's if I'm lucky. I think there's a good chance I can grab and extra 3-5db with the separates, which is critical for a 45 SET amp at 2wpc. So it's a lot of little things and a couple not-so-little tilting the scales here.
I will have another go at the crossover this weekend (killer work week), but I have to say first of all that my measurements aren't as friendly as Beyma's, although from 500Hz down the tuning on mine is fantastic.
I did get spooked, not just from my frustration at making a nice looking graph, but after an accumulation of some concerns other members have voiced about some of the drawbacks of coax design, especially with a 15" cone.
Another thing I'll mention is that Al at US Speaker is a champ and is willing to take the Beymas back minus an open box fee which is very good of him. So it's not like I'm stuck with these drivers and need to make something out of them just because I own them. I still have my 10" Radian coaxes from my first failed attempt that I'm thinking about for a future build if my buddy doesn't buy them. I can't afford to have extra stuff around either!
But the horn-on-box is so classic, and my buddy Cam found Martin Seddon's site after reading one of the threads here, and I have to say I'm really smitten and his horns are beautiful. The esthetics of a La Cléache horn crowning a well made enclosure are hard to resist, and my lady is very excited too, so.......but beyond esthetics, I think I can achieve a better sounding speaker with less issues using the Faital PR400 and a top horn. This arrangement also has the advantage of swapping out CDs over time, and with an external crossover changing a few parts isn't the end of the world.
My takeaway is that coaxes are very challenging but can be very rewarding if you get it dialed in, and horns on boxes are challenging in other ways but maybe don't have some of the built in disadvantages of coax drivers.
The last thing, and it's very important to me, is I will probably achieve noticeably higher sensitivity with the Faital (100db) and Martin's horn, as well as much better directivity. Davor's crossover is probably about as good as it's going to get as far as parts go, but with the Beyma I'm starting at 96db and will probably end up in the low 90's if I'm lucky. I think there's a good chance I can grab and extra 3-5db with the separates, which is critical for a 45 SET amp at 2wpc. So it's a lot of little things and a couple not-so-little tilting the scales here.
I believe what you're saying GM, and I'm spoiled by my RAAL 70/20s. One of the things LaCleache profile is supposed to do a bit better is offer a slightly wider pattern. I don't know if this is true or not, but I sit in the sweet spot anyway so it's not as much of a concern.
I understand your points to move on to something different, especially since you can get a refund.
Beyma measurements are more friendly beacuse they are made in controlled infinite baffle conditions. With driver in a box, you have colorations from edge difraction, internal reflections/resonances etc. But it will be the same thing with any driver.
Crossover I made is a first step, next step is to optimize it with actual measurements. I'll be glad if you give it a shot.
In any way, wish you luck with your project.
Beyma measurements are more friendly beacuse they are made in controlled infinite baffle conditions. With driver in a box, you have colorations from edge difraction, internal reflections/resonances etc. But it will be the same thing with any driver.
Crossover I made is a first step, next step is to optimize it with actual measurements. I'll be glad if you give it a shot.
In any way, wish you luck with your project.
And in lies the problem with coax’s………once you’ve experienced pure, unadulterated HF response from the likes of a RAAL or a Beryllium dome CD or even dome tweeter, it’s hard to go back.
Now I’ve always been in the Geddes camp on CDs…….it’s more about the horn shape and the diaphragm material than anything else. Beryllium pushes that breakup mode so high out of the passband while aluminum and titanium keep it lingering too close for comfort. Polyimide and similar synthetics give the budget conscious customer similar benefits……the B&C became a fan favorite for the smooth response and laid back timbre. But if you want just that much more…..that little sparkle and air?…….there’s simply no substitute for beryllium diaphragms.
I’ll add this…..your bottleneck is going to be again the crossover point……this time it will be the 1” exit throat…….there’s going to be some bunching of the divergent off axis energy that gets amplified by the horn regardless of the shape you choose If you cross at 1khz or below. Power handling will also be limited. You can cross higher say 1.3khz……but that’s going to require some ingenuity on your part in the design…….you’ll need to extend the directivity of the 15pr400 lower and that means a DIY cardioid effort to get that abrupt change smoothed out and pushed lower. Geddes contended it wasn’t an issue for his designs……and for his ears in a large listening space, it probably wasn’t since he cross fired his speakers to mitigate the issue and side wall reflections weren’t really an issue in large spaces. My contention after listening to a pair of Dutch and Dutch in a friends studio in Nashville….well……let’s just say there’s really nothing like consistent directivity down to 500hz………the experience to put it mildly is enlightening.
So pick your poisons…..you’ve made some great choices on drivers……the rest is what you’re willing to compromise…..and nearly everything I’ve mentioned above are seasoned to taste improvements…..problem is once you’ve tasted the forbidden fruit……….
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For what it's worth, some simple measurements on my coax without bass support. Blue is on axis, yellow 30' off axis with mic a bit further away. Roughly 2db lower. The driver is not counter sunk and the box have sharp edges. Not pretty!
But look what happens 4m away at listening position (With bass support) This is how it "feels" like it sounds at listening position.
But look what happens 4m away at listening position (With bass support) This is how it "feels" like it sounds at listening position.
Yes don’t give up without listening to the build. Try various toe in. I don’t see why a 15”+horn will be any easier.
Eminence have a nice stock crossover that seems to work well with most large coaxes I have tried, worth a try. It’s called pxb2:2k5cx. It cuts quite low and high and as such avoid the whole midrange problem, the sound balance is warm and a bit dark much like large Tannoys.
Why not give it a try? Make sure you include a variable LPAD for playing around. Much fun at this house at least.
Eminence have a nice stock crossover that seems to work well with most large coaxes I have tried, worth a try. It’s called pxb2:2k5cx. It cuts quite low and high and as such avoid the whole midrange problem, the sound balance is warm and a bit dark much like large Tannoys.
Why not give it a try? Make sure you include a variable LPAD for playing around. Much fun at this house at least.
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Hmm, the yellow trace disappeared...
Well, good luck with the Faital build!
I'd try more different things first on your existing drivers. First thing buy a 2 channel 31 band analog graphic equalizer to tune your response in seconds instead of building a lot of hard crossovers that you are going to throw away. Use one channel for woofer, other channel for tweeter. https://www.ebay.com/itm/335122539952?hash=item4e06dc25b0:g:YK4AAOSw5jFlOpAC&amdata=enc:AQAIAAAA4PEVXww16e9U96qFTQIb6gJL6dOjstmAGkHVXgJuf8QnTgJ79vzJU7c5gBS1zrIcrvlXCF6BW9Ig9Mjtx2lEViQglIstig+CzHm+fs6wfAv1EEpqu74yaKe8g+W4tGerSfiZfZIlG52LoLbKYrl2qn3e56RTRmhgtpfUtN0aPIgib04L/dMRsDZsK4g7W8lMUB5nlo8xd96SkY0PtwsqI7eUTLUqjFp8LNh/pTUSBeAyubXnS9DpvXo80pNxlpQYnrBESncRuP3aJxVLBw9MaAGCW+FzQlN+tYhPBe4yP4T0|tkp:Bk9SR-bK9JX7Yg
Decide if you need good off axis response. People with small rooms listening close to the speaker (monitor) don't need wide dispersion. No off axis response, your tweeter may be able to shine through the little hole in your woofer. If not, you can lay a tweeter on top of your woofer. I intend to lay a horn & CD on top of my woofer cab, to avoid lifting 72 lb onto six foot tall stands that project sound over my furniture. Takes a little height booster for the CD to even up with the horn outlet, and some foam to prevent buzzing from plastic on wood. Or boost the CD higher than the horn outlet to project highs down at ears, as Peavey PA speakers do (SP2-2004) with a lopsided horn.
The passive crossover built after your curve is successful, can be mounted inside the woofer cab and connect through terminals to your tweeter.
I agree with mayhem13 that 2 db freq-response deviation is not important. However, kinks in the FR cause harmonic and IM distortion. Do the math. 10 or 15 db kinks, I would work to eliminate those. 4 db, depends on the sound. My test, listen to easy to distort tracks like grand piano, tinkly bells, cymbals. I have been unhappy with distortion on every speaker I ever heard on piano until I bought the SP2-XT and replacement SP2(2004). Altec VOT in 1966 may have been great but I only heard them on Lord Jim, Sound of Music, and My Fair Lady. No grand piano in any of those.
Decide if you need good off axis response. People with small rooms listening close to the speaker (monitor) don't need wide dispersion. No off axis response, your tweeter may be able to shine through the little hole in your woofer. If not, you can lay a tweeter on top of your woofer. I intend to lay a horn & CD on top of my woofer cab, to avoid lifting 72 lb onto six foot tall stands that project sound over my furniture. Takes a little height booster for the CD to even up with the horn outlet, and some foam to prevent buzzing from plastic on wood. Or boost the CD higher than the horn outlet to project highs down at ears, as Peavey PA speakers do (SP2-2004) with a lopsided horn.
The passive crossover built after your curve is successful, can be mounted inside the woofer cab and connect through terminals to your tweeter.
I agree with mayhem13 that 2 db freq-response deviation is not important. However, kinks in the FR cause harmonic and IM distortion. Do the math. 10 or 15 db kinks, I would work to eliminate those. 4 db, depends on the sound. My test, listen to easy to distort tracks like grand piano, tinkly bells, cymbals. I have been unhappy with distortion on every speaker I ever heard on piano until I bought the SP2-XT and replacement SP2(2004). Altec VOT in 1966 may have been great but I only heard them on Lord Jim, Sound of Music, and My Fair Lady. No grand piano in any of those.
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Problem for the OP is through personal experience, he’s going to benchmark this against a RAAL……not an apples to orange comparison but the ear/brain mechanism doesn’t care about yours,mine or the OP’s feelings! Lol
Yeah, I was 18 when I went from using paper cone tweeters to just an Altec 802 alum. diaphragm compression driver mounted to a 3/4" thick marine grade plywood panel with a hand done 3/4" round over (no router or other fancy power tools available to me back then) and not till a few years later did I try just using a thick open cell sponge 'gasket'/faceplate did I find my lifelong tweeter of choice except for going to even more lightweight diaphragms as they became available, though of course at the 'expense' of having to use higher XO points as all we're doing is shifting the entire BW higher for a given gain BW efficiency.
Re ribbons, other 'lightweights'; I can understand their allure, but being raised in cinema/PA sound, they all sound a bit too 'diaphanous' for me, though the women much prefer them for HIFI/home apps to my 'disco', 'party', etc., (their wording) horn based system with Magnepan being the historical favorite.
Re ribbons, other 'lightweights'; I can understand their allure, but being raised in cinema/PA sound, they all sound a bit too 'diaphanous' for me, though the women much prefer them for HIFI/home apps to my 'disco', 'party', etc., (their wording) horn based system with Magnepan being the historical favorite.
And my toes curl when I see ultra lightweight diaphragm ribbons mounted on the same baffle as a heaving mass of cone woofers…..what a waste of technology!…..isolate the damn thing for the love of (insert prioritized deity here). I’ve run many a passband sweeps on ribbons to see the horrendous effect on the response when a 7” woofer is pulsing an 80hz test tone…..folks need to do their homework.
The equalizer is a great idea! I had only been thinking in terms of active DSP stuff which I really don't want to get into right now, never even thought of using an analogue EQ. I'm with you and Mayhem all the way in what you've both been saying, and I'm pretty sure I could rein in those Beymas to get something pretty good. But it's not a guarantee. If I had the space, time and money, I'd keep them and noodle around over the winter and spring until I hit the sweet spot.
But there's still one big thing about them that I won't be able to change - sensitivity. If I do end up using notch filters and lord knows what else by the time I'm done, like I've said before, I'll be lucky to hit 92db, and maybe even a bit lower.
While I was at work my bud Cam threw the FR graphs for the Faital drivers into WinPCD (no port merging) and just messing around a bit with 2nd order BW, he came up with a very reasonable looking model, much easier to deal with than the Beymas. And the PR400 models beautifully at 145L/42Hz, two 4" ports. F3 42Hz. I think I can bring this in at 96db, huge advantage for my 45 SET. If I don't end up with much mechanical loss or having to pile a bunch of parts on it, this pairing will definitely play that little amp not just barely, but properly. The Beyma would make music, but I think it would be anemic.
I'd still love to do the Beyma project because I think it could result in a very nice speaker. But If I can get most of my money back out of them, I kinda have to do it. I'm not really quitting, I'm stupidly stubborn, really. But there are too many reasons to make this change. I'm a novice, everything is "if I only knew then what I know now".
I love those RAALs, they float music into the room in such a way........the way they deliver jazz cymbals and brushes is narcotic. But I've heard plenty of horn systems, most recently on a visit to another audiophile's place in Connecticut, 2 hours from here. Holy smokes did he have horns, huge JBL bins with GIANT red butt cheek horns, and it was incredible. No matter where I went in the untreated room, the music was there, axis or no axis. Things like imaging and all that hifi stuff just became secondary when I was listening to an Eva Cassidy tune he had on and I could see the mic and her face, it was so large scale and realistic. I've heard LaScalas, VOTTs, and others over the years, and they all have that same immediacy and realism. That's all I'm after. None of it is live music, I'm fortunate to see plenty of that. Honestly the experience is usually great, but the sound is ironically a hot mess. The only exception is the Vanguard, where I've been a few times. If you sit in the right spot it can get magical.
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I use Tannoys with a woofer and it cleaned up the mid range no end.
Tannoy themselves did exactly that with the best speakers they produced like the FSM, Buckingham Monitor, Dreadnought and DMT215.
I was always under the impression that tannoys with extra bass was 2,5-ways not 3-ways? Ie no high pass on the coax bass? They share cabinets so I don’t get how that would improve anything.