If you can cross the ribbon over low enough the woofer's dispersion won't be very narrow.
A 6 inch cone become directional only above about 2300 Hz. There are ribbons that can cross over as low as 1,800 Hz (Selah Audio sells one, and they use it in their Anniversario speaker) I have some and have tested them and can confirm that if using a steep DSP crossover (48 dB per octave or better) they can perform quite well at 1800 Hz- low distortion up to ~100 dB SPL 1 meter. At 1800 Hz a 6.5 inch driver is not "beamy" at all.
AMT drivers like the Dayton AMTPRO-4 can be used down to 1200~1400 Hz with a steep crossover.
However none of the Fountek ribbons can cross this low, so typically you will run into woofer dispersion problems using a 6.5" woofer and a Fountek tweeter. However, if you are listening nearfield this is largely moot.
A 6 inch cone become directional only above about 2300 Hz. There are ribbons that can cross over as low as 1,800 Hz (Selah Audio sells one, and they use it in their Anniversario speaker) I have some and have tested them and can confirm that if using a steep DSP crossover (48 dB per octave or better) they can perform quite well at 1800 Hz- low distortion up to ~100 dB SPL 1 meter. At 1800 Hz a 6.5 inch driver is not "beamy" at all.
AMT drivers like the Dayton AMTPRO-4 can be used down to 1200~1400 Hz with a steep crossover.
However none of the Fountek ribbons can cross this low, so typically you will run into woofer dispersion problems using a 6.5" woofer and a Fountek tweeter. However, if you are listening nearfield this is largely moot.
a 6.5" starts beaming around 1600hz I think. Cone profile also has an effect too, the shallow the better. But each driver performs differently anyway
An x/o just above may be ok because the mid bass is rolling off already/some tweeter input
The Selah ribbon's looks very intriguing altho I's argue the x/o point is no better than the AST 2560 (1900 min. 3rd order recommended)
An x/o just above may be ok because the mid bass is rolling off already/some tweeter input
The Selah ribbon's looks very intriguing altho I's argue the x/o point is no better than the AST 2560 (1900 min. 3rd order recommended)
Last edited:
"Beaming" in a driver becomes an issue when the wavelength of the sound in air is less than the cone diameter. At room temperature and 1 atmosphere air pressure, the frequency of sound with a wavelength of 6.5 inches is 2.08 Khz. And the actual cone of a 6.5 inch driver is somewhat smaller than the overall 6.5 inch diameter, placing the frequency where beaming becomes significant even higher, to something like 2.1 ~2.2 kHz.
I agree. The narrowing of excursion is a gradual thing (stating the obvious, i know) it merely depends what threshold you place on what is "narrow" or "wide". For a device with 90* horizontal radiation, then narrowing to +/-45* would be less noticeable (i imagine). Even this, in comparison with a near 180* radiation angle, is quite a difference. I.e. Matching directivity at crossover is difficult, unless the ribbon goes low enough.
A tall order at 2-2.5k, where id guess there is still a directivity mismatch or a 2:1 ratio, if not more.
AMTs are different altogether, go lower perhaps, lower distortion too perhaps (at lower freqs at least), but have their own compromises, and aren't ribbons. The single largest virtue of ribbons, is the low mass, which domes and AMTs aren't going to better. Unfortunately the drawback is low frequency efficiency (low area, and mass). I haven't used AMT and i have no idea or their directivity vs frequency (other than baffled or dipolar). If the directivity gives a better match at xo, then use the AMT.
In my own experience, though small, i found running a 5" up to 3k unacceptable, despite being within +-2dB. Take from that what you will.
A tall order at 2-2.5k, where id guess there is still a directivity mismatch or a 2:1 ratio, if not more.
AMTs are different altogether, go lower perhaps, lower distortion too perhaps (at lower freqs at least), but have their own compromises, and aren't ribbons. The single largest virtue of ribbons, is the low mass, which domes and AMTs aren't going to better. Unfortunately the drawback is low frequency efficiency (low area, and mass). I haven't used AMT and i have no idea or their directivity vs frequency (other than baffled or dipolar). If the directivity gives a better match at xo, then use the AMT.
In my own experience, though small, i found running a 5" up to 3k unacceptable, despite being within +-2dB. Take from that what you will.
Yes, you're right. I just double checked with this Wavelength
2085 Hz by my calculation
I wd imagine other factors affect beaming i.e. cone profile. If you look at the frequency plots of most 6.5's the 15 or 30 degree plot will start to roll off well before 2khz
2085 Hz by my calculation
I wd imagine other factors affect beaming i.e. cone profile. If you look at the frequency plots of most 6.5's the 15 or 30 degree plot will start to roll off well before 2khz
My point, now i have found it, is that in common with some ribbons, AMTS are likely to show some degree of cavity resonance due to back chamber (as you found out already), and it is more than likely that this is why manufacturers specify these lower limits of xo freq, besides THD and power handling.
Bill, exactly. To match with a tweeter with wide directivity at xo, i would be looking at 45* polars and not relying on 15-30* polars.
Bill, exactly. To match with a tweeter with wide directivity at xo, i would be looking at 45* polars and not relying on 15-30* polars.
Last edited:
The Satori doesn't look too bad, at least up to 2.2khz, just 3dB down (60 degrees)
Great thing about AMT's is they usually have a v flat impedance, which helps x/o phase stuff
Interesting....I wonder then what issue the OP is hearing?
Could it be beaming at (up to) an octave higher, since hes using 8th order LP which should put issues out of audibility (less than) an octave higher than his xo point?
Or just nasty bottom end sound from the neo, when stretched too far and running too low? I know from my little experience that the neo3.5h sounds rough if you are too shallow with slopes, or allow too little attenuation at 2k. Ribbons with flat impedance, its both good and bad, for me at least, it makes some things harder, some things easier.
Could it be beaming at (up to) an octave higher, since hes using 8th order LP which should put issues out of audibility (less than) an octave higher than his xo point?
Or just nasty bottom end sound from the neo, when stretched too far and running too low? I know from my little experience that the neo3.5h sounds rough if you are too shallow with slopes, or allow too little attenuation at 2k. Ribbons with flat impedance, its both good and bad, for me at least, it makes some things harder, some things easier.
I'm wondering if there's a pistonic issue after the cone surround dip which causes some colouration/loss of definition. Maybe up to 2.2khz its not too bad (I hope)
Mixing 2nd(satori) and 3rd order(ribbon/amt) x/o's .. anyone tried this? I'm guessing you can manipulate the rolloff of the 2nd order by altering the cap size etc
Last edited:
Hmmm.
Whatever electrical slopes give the desired acoustic response and phase response.
In my own first foray into active filters, the LP is actually 5th order, and the HP is 4th order. To protect the tweeter from DC, and also align phase i added a series cap to the tweeter which was large enough as to not affect the acoustic response in any significant way. Doing this aligned phase almost perfectly, to what would be expected in a 4th order crossover.
Perhaps a similar approach would help IF combining 2nd and 3rd filters gives phase issues?
Eg 2nd order LP with the 3rd order giving BSC? Then you'd be left with 2 3rd order filters, and (i guess) quadrature phase offset between them. Almost a 1st order network....if that's desirable
Whatever electrical slopes give the desired acoustic response and phase response.
In my own first foray into active filters, the LP is actually 5th order, and the HP is 4th order. To protect the tweeter from DC, and also align phase i added a series cap to the tweeter which was large enough as to not affect the acoustic response in any significant way. Doing this aligned phase almost perfectly, to what would be expected in a 4th order crossover.
Perhaps a similar approach would help IF combining 2nd and 3rd filters gives phase issues?
Eg 2nd order LP with the 3rd order giving BSC? Then you'd be left with 2 3rd order filters, and (i guess) quadrature phase offset between them. Almost a 1st order network....if that's desirable
Last edited:
I'm using the Dayton AMTPRO-4 now and it is not bothered by the occasional lower frequency burp from the driving amp- as long as the burp isn't going to exceed the power rating of the driver- 50 watts.
With a "classic" pleated ribbon tweeter- YES you MUST protect them against bass and thumps and so on, else the ribbon will "unpleat" itself and then hang loosely there in the tweeter... useless thereafter (at least until you can replace the ribbon.)
Even some of the ribbons where the foil is bonded to a kapton substrate, you can open the ribbon- actually burn or melt a hole in it, or rip it at the point where it heated up from a burst of bass power. But ribbons of this type - such as the Fountek "Neo" series - are much more rugged than "classic" pleated ribbons. I think there are some sonic differences between the "Neo" style kapton/aluminum ribbons and the pure foil ribbons. The pleated foil ribbons sound a bit more detailed to me, rendering delicate aspects of the sound with more finesse...
The AMT sounds different again, more dynamic and "bodied" but with some of the delicacy of a ribbon. So far with my design here I am liking the AMT> for more info follow my thread on this 2-way biamp project http://www.diyaudio.com/forums/multi-way/264096-build-2-way-biamp-integrated-source.html
With a "classic" pleated ribbon tweeter- YES you MUST protect them against bass and thumps and so on, else the ribbon will "unpleat" itself and then hang loosely there in the tweeter... useless thereafter (at least until you can replace the ribbon.)
Even some of the ribbons where the foil is bonded to a kapton substrate, you can open the ribbon- actually burn or melt a hole in it, or rip it at the point where it heated up from a burst of bass power. But ribbons of this type - such as the Fountek "Neo" series - are much more rugged than "classic" pleated ribbons. I think there are some sonic differences between the "Neo" style kapton/aluminum ribbons and the pure foil ribbons. The pleated foil ribbons sound a bit more detailed to me, rendering delicate aspects of the sound with more finesse...
The AMT sounds different again, more dynamic and "bodied" but with some of the delicacy of a ribbon. So far with my design here I am liking the AMT> for more info follow my thread on this 2-way biamp project http://www.diyaudio.com/forums/multi-way/264096-build-2-way-biamp-integrated-source.html
What frequency and what slope did you cross these tweeters over at? Seems to me that used in a line array like this the Fountek CD 2.0's should allow decent output levels without objectionable distortion at considerably lower crossover points than would be acceptable with a single tweeter.
And, wow, these Fountek ribbons are QUITE efficient, a bunch of them like that - wow- you could probably drive them with your LINE PREAMP.... hahaha- or maybe directly off your CD player. (just kidding of course.) 9 tweeters would add about 25~27 dB to their 97 dB 1 watt 1 meter sensitivity... 120 dB+ at 1 watt 1 meter, wowie zowie.
If the midbass drivers are also somewhat efficient it seems to me like you could drive a pair of these from some low power amp, like a small Pass Zen amp, or Pass First Watt type current-source amp, a Jungson class A DIY amp, or some little 300b SET type thing. One of these days I'm going to have to build some kind of high-efficiency speaker to play with. I want to play around with some of the low-watt SET amps just to see what all the buzz about them is. I have an 845- based SET amp with about 20 watts a side and some good speakers that are about 93 db 1 watt 1 meter and it sounds good but I am not hearing the "glorious" sound that others rave about. So I thought I'd try (some day) a pair of high-efficiency array type speakers and maybe a Bottlehead SET of some kind. Just a thought.
Someone asked what size enclosure I am using for my Satori 6.5" build - I am using the Dayton 0.75 cu. ft. ready-made cabinet. I have calculated a port - 1.5 inch diameter 3.6 inch length. I have lined the interior with Black Hole 5. Due to the black hole 5 and the chamber for the AMT driver, I estimate I have about 0.65 cu ft of air, the - F3 point should be about 45 Hz or so. Overall Q should be around 0.6 I think. I also have a pair of #8 rubber stoppers I can plug the ports with to experiment with sealed boxes, although the enclosure size isn't ideal for a sealed design. (I had these speaker cabinets on hand and that's why I am working with them, rather than designing a cabinet and building it from scratch.)
Bass with the vent ports open goes quite low but transients & group delay are better with the ports plugged with the stoppers. I tend to prefer sealed boxes, but these ported enclosures are good, and I think using these drivers in a sealed box makes them a little OVER damped. I am still fooling around with listening vented with the ports open or plugged up, fiddling with EQ for each scenario. Right now I am leaning towards vented.
Bass with the vent ports open goes quite low but transients & group delay are better with the ports plugged with the stoppers. I tend to prefer sealed boxes, but these ported enclosures are good, and I think using these drivers in a sealed box makes them a little OVER damped. I am still fooling around with listening vented with the ports open or plugged up, fiddling with EQ for each scenario. Right now I am leaning towards vented.
Here's pictures of the finished project
Here's the speakers and the finished electronics chassis; the chassis contains the MiniDSP 2-way DSP crossover, switching amps for woofers and tweeters, power supplies, and stuff to connect a small Windows tablet via USB for control of the DSP and also to feed FLAC files from my server for playback. About 40 watts / channel available for the AMT tweeters, about 80 watts / channel available for the woofers. Since there are no crossover components in series with the drivers you gain a little efficiency and so far this power level seems OK.
I started with a 48 dB Linkwitz crossover at 1200 Hz, and changed that to 2000 Hz, at 1200 Hz there was like an audible transition from the Satori cone to the AMT. At 2 kHz it's more of a seamless thing. Hard to describe, you'd have to hear it. I am still fooling around with crossovers, EQ and so on, making measurements.... with the notebook PC and the DSP this thing is plenty fun to tweak around with.
The volume knob and off /on switch are the only controls. The rest is done with the tablet. The knob is made from a chunk of red tigers eye, a mineral with a beautiful chatoyance.
Sorry for the huge pictures, I don;t know how to control image size in this editor.
Here's the speakers and the finished electronics chassis; the chassis contains the MiniDSP 2-way DSP crossover, switching amps for woofers and tweeters, power supplies, and stuff to connect a small Windows tablet via USB for control of the DSP and also to feed FLAC files from my server for playback. About 40 watts / channel available for the AMT tweeters, about 80 watts / channel available for the woofers. Since there are no crossover components in series with the drivers you gain a little efficiency and so far this power level seems OK.
I started with a 48 dB Linkwitz crossover at 1200 Hz, and changed that to 2000 Hz, at 1200 Hz there was like an audible transition from the Satori cone to the AMT. At 2 kHz it's more of a seamless thing. Hard to describe, you'd have to hear it. I am still fooling around with crossovers, EQ and so on, making measurements.... with the notebook PC and the DSP this thing is plenty fun to tweak around with.
The volume knob and off /on switch are the only controls. The rest is done with the tablet. The knob is made from a chunk of red tigers eye, a mineral with a beautiful chatoyance.
Sorry for the huge pictures, I don;t know how to control image size in this editor.
An externally hosted image should be here but it was not working when we last tested it.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.