^ Sure, the "F" has a dual 15" small horn added on.
I assume that the Coaxial portion is still sealed.
That's a mighty large / heavy box. I don't see it being useful for a mobile setup, where you'd be carrying subwoofer anyway. It's a clever design for a full-range install, though, for sure.
As you yourself mentioned earlier, for mobile use, a design like this makes more sense with a smaller coax.
And heck, why dual 15's? Dual 12's + a 10" coaxial, with full directionality, would be heavenly.
Still a bit ungainly for mounting on speaker poles, though. (just.)
I assume that the Coaxial portion is still sealed.
That's a mighty large / heavy box. I don't see it being useful for a mobile setup, where you'd be carrying subwoofer anyway. It's a clever design for a full-range install, though, for sure.
As you yourself mentioned earlier, for mobile use, a design like this makes more sense with a smaller coax.
And heck, why dual 15's? Dual 12's + a 10" coaxial, with full directionality, would be heavenly.
Still a bit ungainly for mounting on speaker poles, though. (just.)
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Yes, the ultimate plan is to have it in a ca 200 Hz waveguide - like the smaller SM80 or the top part of the SM80F. If I can get a similar performance as my EV SH1502R from this coax, I would be very happy. These are also ported and can be used stand alone, but I have them now from 140 Hz up above my monster bass horns.
I wonder how to make such a waveguide. An adapter ring could be 3D printed in two or three parts to make the transition as smooth as possible and then a circular horn out of foam board. Or a 3D printed round to square horn adapters would be also possible for a simple square conical horn. Or square horn with foam inserts in the corners to transfer the round to square...or MDF and CNC - or laminate on a negative form...I am not skilled enough to do any of this but the 3D printing part...
I wonder how to make such a waveguide. An adapter ring could be 3D printed in two or three parts to make the transition as smooth as possible and then a circular horn out of foam board. Or a 3D printed round to square horn adapters would be also possible for a simple square conical horn. Or square horn with foam inserts in the corners to transfer the round to square...or MDF and CNC - or laminate on a negative form...I am not skilled enough to do any of this but the 3D printing part...
I played a bit in Hornresp. I added a shallow horn 125 mm deep and 568 diameter in two steps a la Keeley (80 deg for the first 2/3 and then 120 deg) on the 12XA30 woofer. The dark line is ported, the grey line is sealed back chamber. I think if this was made right, the result would be very fine
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So today I had a quick listen to the Beymas in small BR boxes (ca 35x35x40 cm) with my big horn subwoofers. They are very detailed, the transients really snap. Maybe slightly harsh on axis, but maybe that is just accurate to the recordings, it was just in some songs. I need to try my SET amps with them.
Did not turn them up too loud but they sound very "easy". I wonder if they would sound even better in a SM80 type box. For the money, these are just great. I will try to make some measurements - the crossover is supposed to be tuned in an anechoic chamber by a loudspeaker guru with lots of measurements and tuning. The sound is great, so I would believe that.
Did not turn them up too loud but they sound very "easy". I wonder if they would sound even better in a SM80 type box. For the money, these are just great. I will try to make some measurements - the crossover is supposed to be tuned in an anechoic chamber by a loudspeaker guru with lots of measurements and tuning. The sound is great, so I would believe that.
^ Jeez, you even got yokes for that price! Sweet.
I would think those boxes are a bit small, but I guess with dedicated subs it can work.
If you can find the time, I'd love to see the frequency response of them, in those cabinets, because if/when I build mine I will want to go as small as I can get away with. (Also with dedicated subs.)
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re the harshness:
1: Make sure the HF diaphrams are OK. I know from personal experience that they can start to get edgy before they actually burn up. If I owned those, I would definitely get the Be diaphrams, despite the cost, and save the current ones for emergency spares.
2: They are 80 degrees. You might be used to 60's? Make sure you don't "toe them in" much, if at all. that will create a HF hot-spot in the center.
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re that crossover: If you ever manage to reverse-engineer it, PLEASE post the circuit here !
And congrats. What a nice grab.
I would think those boxes are a bit small, but I guess with dedicated subs it can work.
If you can find the time, I'd love to see the frequency response of them, in those cabinets, because if/when I build mine I will want to go as small as I can get away with. (Also with dedicated subs.)
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re the harshness:
1: Make sure the HF diaphrams are OK. I know from personal experience that they can start to get edgy before they actually burn up. If I owned those, I would definitely get the Be diaphrams, despite the cost, and save the current ones for emergency spares.
2: They are 80 degrees. You might be used to 60's? Make sure you don't "toe them in" much, if at all. that will create a HF hot-spot in the center.
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re that crossover: If you ever manage to reverse-engineer it, PLEASE post the circuit here !
And congrats. What a nice grab.
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A small update. The dimensions are 40x40x33 cm external. I made some measurements and the harshness was an on axis peak at around 10 kHz, it can be seen in the datasheet as well. There is a sharp dip above 1 kHz, maybe that is due to measurement setup or the metal grill - it moves in frequency with the microphone position, I need to measure somewhere else to confirm. Nearfield measurement shows that they play down to 80 Hz. I will post the measurements tomorrow, they need to be processed a bit.
Ok, I could not just go to sleep without sharing I think that the 1kHz dip is baffle diffraction. I ran a simulation in the diffraction and boundary simulator Excel sheet and the dip is there and moves with distance. The measurements say more about the room than the speaker, but I think these are pretty good.
I am not sure what to think about the impulse response, it seems to me that it could be improved with active crossover. There is a phase wrap at around 3.5 kHz, but that seems too high for the crossover point, there is an impedance peak at 3 kHz. I will need to do some polar measurements and also take it apart to see what the crossover is like. It does not look heavily optimized any more?
I think that the 1kHz dip is baffle diffraction. I ran a simulation in the diffraction and boundary simulator Excel sheet and the dip is there and moves with distance. The measurements say more about the room than the speaker, but I think these are pretty good.I am not sure what to think about the impulse response, it seems to me that it could be improved with active crossover. There is a phase wrap at around 3.5 kHz, but that seems too high for the crossover point, there is an impedance peak at 3 kHz. I will need to do some polar measurements and also take it apart to see what the crossover is like. It does not look heavily optimized any more?
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I do not remember, but I think only smoothed unless gate is mentioned in the description. I think I tried to make them look nice with the gate, but it did not help much. These were just a few quick sweeps. I will pay more attention to room placement next time. Yesterday I read a great article on speaker measurements by Mr. D'Appolito and the next measurement session will make more sense.
A very interesting link found (in German): Beyma 12xa30nd Koax Modifikationen, Lautsprecher - HIFI-FORUM
So now I think I know where the nasty dips come from. The speaker baffle is buried some 5 - 7 centimeters from the grill and therefore there is a resonance chamber. This will need to be fixed if the box is to be reused. I think I will add a baffle closer to the front and it will most probably end up as sealed. It will also alow for some kind of front horn attachment that I plan to try out.
Grills and baffles always seem problematic for sound quality. I fitted grills to my tops but had problems with them vibrating. As a solution I have magnetically attached grills that I only install for transport. This has worked quite well so far but I'm not dealing with rowdy crowds.
As a fix for your problem you could try installing grill foam in the cavity as it may lower the Q of the resonance.
From my experience of local venues grills are quite uncommon on DIY speakers used for installed PA. Usually the drivers are just in deep horns with big phase plugs or for subs inside the speaker cab. Protection is provided by locating them out of arms reach.
True. There is no need for grills on mine - except maybe for transport in future, but that can be solved by covers - I use that for my guitar cabinet and head. With hard and padded fronts. The foam that was behind the grill just fell apart when I took it out, so I tend to avoid foam completely. I will try to measure if 3D printed horn like insert would work - if not, then I just move the baffle. Unfortunately, then the balance will be gone and I will have to move the consoles too - or just fit standard pole nests at the new center of gravity.
It seems it is too deep for that. Some kind of "magic sponge" damping would be much easier. And the custom, highly tuned and optimized crossovers are...wait for it...stock Beyma crossovers FD-2XA. Which makes this even a better deal on my part The speakers look like what they were supposed to be...I did not take them out yet.
The speakers look like what they were supposed to be...I did not take them out yet.Attachments
So some further measurements confirmed that the source of the dips is the "front chamber" - and also maybe the cube box itself. I tried to line the sides with a bit of polyfil and it reduced the dips a bit and smoothed the FR in general, also the spectrogram looks cleaner. New boxes are definitely a must.
The FR plot shows measurement with the microphone at the dust cap inside the "front chamber."
The funny thing is, even as they are, I really like the sound, it seems to be clear, clean and very dynamic, I would say that there is very little harmonic distortion - louder is just louder, it does not become unpleasant with volume. In the link above, driver tuning is described. I do not think I will ever go that far. I have tested them so far in (loud) home listening environment, things may be different on PA levels.
Edit: The crossover to the bass horns is somewhere around 130 Hz, this is measurement including the Thomann t.rack DSP mini 4x4 used as high pass, no other processing.
The FR plot shows measurement with the microphone at the dust cap inside the "front chamber."
The funny thing is, even as they are, I really like the sound, it seems to be clear, clean and very dynamic, I would say that there is very little harmonic distortion - louder is just louder, it does not become unpleasant with volume. In the link above, driver tuning is described. I do not think I will ever go that far. I have tested them so far in (loud) home listening environment, things may be different on PA levels.
Edit: The crossover to the bass horns is somewhere around 130 Hz, this is measurement including the Thomann t.rack DSP mini 4x4 used as high pass, no other processing.
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