looking for the cheapest driver that can be crossed at 650 hz. found these two:
https://www.rcf.it/en/products/product-detail/ndt895
and
https://faitalpro.com/en/products/HF_Drivers/product_details/index.php?id=502020173
they're about the same price but of course being slightly larger ( 3" vs 2.5" ) the RCF is slightly more expensive
their impedance curves look about the same which means they can both go equally low in frequency since they also both have polymer surrounds - but the Faital has the dome out of the same polymer whereas RCF has Titanium dome and claims to be ribbed ( couldn't find pictures of the diaphragm to confirm )
ribs seem to be a novelty for RCF but also this driver has exceptionally smooth response for titanium dome ( much smoother than older RCF ) so i guess they did engineer some strategic ribs into the dome to control breakup ... this is apparently a newer driver and they probably had some computers to help with this ...
i would only use these as upper midrange to cross to a ribbon supertweeter so i don't really care about their HF response but rather i wonder which of them will last longer ? i would like them to last about 30 years of home use.
will the plastic dome of Faital sag overtime ? compression driver tolerances are tight - if the center of the 2.5" dome sags by even 1 millimeter that may be too much. it needs to hold its shape EXACTLY for 30 years.
why does RCF go through all the trouble of a ribbed titanium dome with plastic suspension when they can just make the whole thing out of one piece of plastic like Faital does ? is it for longevity ?
actually it seems RCF now has plastic domes but they have suspension from a different plastic ! ! ! while Faital's titanium domes are all titanium including the suspension. does that mean Faital is a cheaper brand than RCF ?
and as for the ribs on titanium dome - could they introduce some kind of stress points that weaken the material ? how hard would you have to push the driver for this to matter - or can it even matter at all ?
which driver would you get ? i think Faital is $305 from PE and RCF is like $320 from Beach Audio
i can see Faital looks a bit more efficient in HF but this may be due to a different horn being used - a more "beamy" horn will raise on-axis HF response ... and besides, as i said i would cross it over to a ribbon supertweeter
https://www.rcf.it/en/products/product-detail/ndt895
and
https://faitalpro.com/en/products/HF_Drivers/product_details/index.php?id=502020173
they're about the same price but of course being slightly larger ( 3" vs 2.5" ) the RCF is slightly more expensive
their impedance curves look about the same which means they can both go equally low in frequency since they also both have polymer surrounds - but the Faital has the dome out of the same polymer whereas RCF has Titanium dome and claims to be ribbed ( couldn't find pictures of the diaphragm to confirm )
ribs seem to be a novelty for RCF but also this driver has exceptionally smooth response for titanium dome ( much smoother than older RCF ) so i guess they did engineer some strategic ribs into the dome to control breakup ... this is apparently a newer driver and they probably had some computers to help with this ...
i would only use these as upper midrange to cross to a ribbon supertweeter so i don't really care about their HF response but rather i wonder which of them will last longer ? i would like them to last about 30 years of home use.
will the plastic dome of Faital sag overtime ? compression driver tolerances are tight - if the center of the 2.5" dome sags by even 1 millimeter that may be too much. it needs to hold its shape EXACTLY for 30 years.
why does RCF go through all the trouble of a ribbed titanium dome with plastic suspension when they can just make the whole thing out of one piece of plastic like Faital does ? is it for longevity ?
actually it seems RCF now has plastic domes but they have suspension from a different plastic ! ! ! while Faital's titanium domes are all titanium including the suspension. does that mean Faital is a cheaper brand than RCF ?
and as for the ribs on titanium dome - could they introduce some kind of stress points that weaken the material ? how hard would you have to push the driver for this to matter - or can it even matter at all ?
which driver would you get ? i think Faital is $305 from PE and RCF is like $320 from Beach Audio
i can see Faital looks a bit more efficient in HF but this may be due to a different horn being used - a more "beamy" horn will raise on-axis HF response ... and besides, as i said i would cross it over to a ribbon supertweeter
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here are measurements of related drivers.
https://audioxpress.com/article/tes...ession-driver-coupled-with-lth142-60-o50-horn
you can see the Faital maintains flat on-axis response by beaming HF as i predicted ...
and here is an older and larger ( 4" ) RCF:
https://audioxpress.com/article/Test-Bench-RCF-ND950-Neodymium-Compression-Driver-and-HF950-Horn
but using the same concept of Titanium diaphragm and polymer surround
the RCF rolls off more on-axis but maintains more HF off-axis because of the more constant directivity type horn versus Tractrix on Faital
according to Google's AI the speed of sound in Titanium is 6 KM / sec but only 2.5 KM / sec in ketone polymer ... though i suspect that is wrong because it also says 2.5 KM / sec for polypropylene and i would expect ketone polymer to have higher speed of sound than polypropylene ...
even so, this would only apply directly if the titanium dome wasn't ribbed. the ribs will make the dome much more flexible lowering the frequency of resonances but also lowering their amplitude if designed properly ...
https://audioxpress.com/article/tes...ession-driver-coupled-with-lth142-60-o50-horn
you can see the Faital maintains flat on-axis response by beaming HF as i predicted ...
and here is an older and larger ( 4" ) RCF:
https://audioxpress.com/article/Test-Bench-RCF-ND950-Neodymium-Compression-Driver-and-HF950-Horn
but using the same concept of Titanium diaphragm and polymer surround
the RCF rolls off more on-axis but maintains more HF off-axis because of the more constant directivity type horn versus Tractrix on Faital
according to Google's AI the speed of sound in Titanium is 6 KM / sec but only 2.5 KM / sec in ketone polymer ... though i suspect that is wrong because it also says 2.5 KM / sec for polypropylene and i would expect ketone polymer to have higher speed of sound than polypropylene ...
even so, this would only apply directly if the titanium dome wasn't ribbed. the ribs will make the dome much more flexible lowering the frequency of resonances but also lowering their amplitude if designed properly ...
The Faital will sound better overall and has a more behaved impedance curve. PEEK diaphragm will sound more pleasant than titanium with such a large diaphragm, considering it will be operating in breakup mode in the audible range around 8 - 10 kHz. The titanium driver will sound zingy and edgy, quickly becoming fatiguing. PEEK is a much more forgiving material for HF reproduction when its covering the top octave.
Embossing a Ti diaphragm has some slight advantages if done strategically, but it won't cure the upper breakup intensity (amplitude level of peaks). Embossing can help partially mitigate radial modes, but those are also coupled to various cavity resonances and phase plug idiosyncrasies.
Embossing a Ti diaphragm has some slight advantages if done strategically, but it won't cure the upper breakup intensity (amplitude level of peaks). Embossing can help partially mitigate radial modes, but those are also coupled to various cavity resonances and phase plug idiosyncrasies.
OK but what if i cross it over to a Ribbon supertweeter at 5 khz ?
Aurum Cantus Ribbon is 100 db efficient all the way through 20 khz whereas Compression drivers are 110 db efficient but only up to about 3 khz unless you're using a beamy horn.
I am guessing at 20 khz the ribbon may actually be more efficient when considering it has wider directivity so it fills the room with HF and not just projects it in one direction.
my preference would be to cross closer to about 9 khz but i don't think the Titanium dome can go that high.
the plastic dome can go high but i am worrying about the longevity of the plastic - hence the question.
if i understand correctly the reason titanium is popular with compression drivers is because it is resilient.
Thats right at the start of breakup for a 3" Ti diaphragm, so you'll need steep filtering to avoid exciting those modes (even partially). PEEK is very well behaved around breakup but does have a tendency to decay slower (pronounced CSD trailing) around the main radial modes. What does make a bigger difference in SQ is the lower impedance peak around 1 - 2k of the Faital driver.
Most HF drivers have a diaphragm to phase plug distance of under 0.5mm.
Plastic will deform at lower temperatures and dissipate less heat than metal.
The cheapest compression drivers with the most displacement are phenolic/linen diaphragm public address drivers.
not sure what drivers you mean. link ?
by cheapest i kind of meant smallest.
i started going down the list of Faital and RCF drivers from smallest to largest until i found ones that could go low enough and that happened at 2.5" VC for Faital and 3" VC for RCF
sadly BMS HF drivers only go down to 1 khz unless you go Co-Axial, but the BMS mid is for another design ...
i also know RCF actually uses 650 hz or so crossover point from 4" compression driver to 15" woofer in their 2-way designs so at least with RCF i know this XO isn't just a pipe dream but actual reality ( though driver in question is only 3" but of similar construction )
although i read reviews for the Faital on PE and both reviewers are running them down to 650 hz as well ( for home use )
I run the HF108 (non R) down to 900 hz on an Eminence 12" coax and it handles it very well, even at pretty high playback levels. This is with a 44mm diaphragm. I shimmed the clearance a little on the loose side to get a little more headroom.
Hi, here another driver with similar impedance plot, titanium surround and dome https://www.eighteensound.it/en/products/hf-driver/1-4/8/ND3T
I remember seeing a yt video where some industry pro said ketone dome breakup at high spl sounds like crackling as tip of the dome decouples. If I remember correct video remark was that ketone is good for lower SPL application. I think same video had more stuff on diaphragms and issues and basically got impression that all titanium is best for high SPL. It might have been one Bennet Prescott videos but have no time to look for it... it might have been some 18sound video as well, I binge watched these last autumn can't remember which video it was, sorry 🙂 https://youtube.com/@bennettprescott?si=xavW5VeNHKpumKT6
I built speakers for a friend with the ND3T crossed currently at 800-20k and they sound great. I don't have other similar drivers to compare, nor did I use them full tilt yet, so take it with grain of salt. Target for the system is ~120db to be able to have outdoors parties. Few more months of spring to wait until I can setup the system outside to see if it does it.
I remember seeing a yt video where some industry pro said ketone dome breakup at high spl sounds like crackling as tip of the dome decouples. If I remember correct video remark was that ketone is good for lower SPL application. I think same video had more stuff on diaphragms and issues and basically got impression that all titanium is best for high SPL. It might have been one Bennet Prescott videos but have no time to look for it... it might have been some 18sound video as well, I binge watched these last autumn can't remember which video it was, sorry 🙂 https://youtube.com/@bennettprescott?si=xavW5VeNHKpumKT6
I built speakers for a friend with the ND3T crossed currently at 800-20k and they sound great. I don't have other similar drivers to compare, nor did I use them full tilt yet, so take it with grain of salt. Target for the system is ~120db to be able to have outdoors parties. Few more months of spring to wait until I can setup the system outside to see if it does it.
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this particular thread is for a line array upper midrange using planar waveguide adapters and it would take 50% more of 1" exit drivers than 1.5" exit drivers for the same height of array thus making HF108 array the same price as HF146 but with less midrange extension ...
of course an array of 108 would have better top end than array of 146 but if crossing to ribbon that is mostly irrelevant
as for point sources the current thinking is
BMS4599 on BMS 2236 Horn from 800 hz to 2.5 khz
JBL D2 on JBL Waveguide from 2.5 khz to 8 khz
4 X Beyma CP12/N from 8 khz and up ( aimed 15 degree up, 15 down, 25 left and 25 right respectively )
the idea is with point source to use narrow frequency bands with highest performance drivers optimized for maximum performance in those bands
for line array the idea is to use the smallest drivers that can reach low in frequency because with line arrays it's all about keeping center to center distances a low multiple of wavelength so it isn't about high performance drivers at that point but small, cost effective drivers that can work in low frequencies
650 hz was somewhat arbitrary number - it was simply the lowest i could go without going to dedicated midrange drivers which are both very expensive and perhaps don't go high enough for optimal XO to ribbon
with a 650 hz XO you can flank the array with 5" midbass drivers on both sides and still have good horizontal dispersion ... with higher XO you would perhaps want to go to 4" drivers and the choices there are miserable compared to choices with 5" drivers ... in fact i don't know of even one prosound 4" driver with a cast aluminum basket, and some brands only offer 4" as fullrange, no 4" midbass or midrange. in fact only B&C seems to offer a 4" prosound midbass and it's a bit weird and i would rather not use it. stepping up to 5" suddenly you can have anything you want !
I only mentioned the HF108 as a comparison to a smaller driver with a 44 mm VC which can go down to 900 hz. I also mentioned shimming the diaphragm (easy on Faital drivers) to get a little more low end capability from it with minimal penalty in terms of sensitivity and HD.
that is actually pretty interesting. you mean to increase the diaphragm to phase plug distance from say 0.5 mm to 1 mm ? you would lose HF extension but we don't care about that. it would be an interesting mod though i personally wouldn't want to mess with a well designed driver.
yeah i understand a 44 mm driver can go to 900 hz but actually 650 vs 900 is a big difference.
@Dissident Sound Yes, increasing clearance would gain excursion capability with minimal loss up top and really no significant SPL or HD penalty. 0.5mm extra clearance would probably cost you 1.5 dB loss. Can be easily accomplished by adding 0.020" thick layer of kapton foil tape to the diaphragm flange. Can easily be reversed if you don't like it.
I agree, you'll need at least 2.5" diameter diaphragm to comfortably go down to 600 hz with decent SPL capability.
I agree, you'll need at least 2.5" diameter diaphragm to comfortably go down to 600 hz with decent SPL capability.
low frequency SPL capability is not a concern with arrays - it is the high frequency that is the concern - due to how there is coupling at low frequencies but cancellation at high frequencies
i would run any compression driver in an array to the lowest frequency it's rated to play at without any consideration for output capability unless the array is for PA use which it is not
from what i read in PA the arrays run with about 15 db of HF EQ boost to make sure the audience gets flat FR and if something like a crash cymbal hits there are limiters to prevent the drivers from incinerating and it sounds horrible because the entire bandwidth of 1 khz - 20 khz is cut to limit power that is mostly caused by stuff above 10 khz that is getting boosted by 10+ db ...
of course multi-band limiters exist that can suppress those HF peaks without affecting midrange but at that point why not just send that VHF to the ribbons and put the limiter on the ribbons ...
plus replacement ribbons for Aurum Cantus are $10 a piece or you can make your own from regular aluminum foil.
the power response ( space averaged frequency response ) of compression drivers begins to drop at around 3 khz from "mass break point" and horn beaming while ribbons are ideally used above 3 khz which makes or a rather natural pairing IMO ...
for PA use the ribbon is too fragile and ain't nobody got time fo dat ... but for home use replacing blown ribbons can add charm to the hobby ...
my original idea was to use Radian Planars for upper midrange but when i realized the diaphragm is non replaceable that left a sour taste in my mouth because those drivers use a LOT of neodymium which would be going in the trash anytime you melted one of those $1 diaphragms.
speaking of which ... Faital is out of their mind charging $150 for a replacement 2.5" diaphragm made out of a single piece of plastic.
RCF charges less for a 4" titanium one.
i couldn't find replacement diaphragms for NDT895 but i assume it's because that's a new driver.
you know if Faital diaphragm was $50 instead of $150 i would say who cares whether it is as reliable as Titanium or not but if they charge more for it than what Titanium ones cost then it has to be held to the same standard of durability.
speaking of which ... Faital is out of their mind charging $150 for a replacement 2.5" diaphragm made out of a single piece of plastic.
RCF charges less for a 4" titanium one.
i couldn't find replacement diaphragms for NDT895 but i assume it's because that's a new driver.
you know if Faital diaphragm was $50 instead of $150 i would say who cares whether it is as reliable as Titanium or not but if they charge more for it than what Titanium ones cost then it has to be held to the same standard of durability.
Sure, PA line array use is a totally different animal. The 12 - 15 dB rise down low (depending on length) isn't a common issue with typical hifi speakers. Making the line keep up with the poor HF sensitive of individual drivers is a problem and it's very audible when pushed hard.
Faital prices are ridiculous for repair parts. In all sincerety, their prices as a whole are too high for what you get. Some of the drivers are very good though ie. Hf108 .which has almost no competition. It's my favorite 1" for coax use.
You should look at PRV drivers. They're quite amazing for the cost but built as good as most brands. I use the D3220PH with the hybrid Ti/Mylar surround diaphragm. Its a very smooth 2" exit driver with excellent detail, considering the $120 (driverb with Ti/My diaphragm together) cost. You may be happy with the phenolic diaphragm that comes stock with the D3220PH. The build quality is superb for such a cheap driver. It can be used down to 400 hz with the appropriate horn and xover.
Faital prices are ridiculous for repair parts. In all sincerety, their prices as a whole are too high for what you get. Some of the drivers are very good though ie. Hf108 .which has almost no competition. It's my favorite 1" for coax use.
You should look at PRV drivers. They're quite amazing for the cost but built as good as most brands. I use the D3220PH with the hybrid Ti/Mylar surround diaphragm. Its a very smooth 2" exit driver with excellent detail, considering the $120 (driverb with Ti/My diaphragm together) cost. You may be happy with the phenolic diaphragm that comes stock with the D3220PH. The build quality is superb for such a cheap driver. It can be used down to 400 hz with the appropriate horn and xover.
i found a better solution:
https://www.rcf.it/en/products/product-detail/nd650
by better i mean it's 2.5" versus 3" but still has the same construction of titanium dome with soft surround and low FS
somehow missed this driver on 1st round of search because it said "pure titanium" so i assumed it meant titanium surround, which i do not want ...
however it is in fact titanium dome with plastic surround and it's just $60 for replacement diaphragm:
https://en.toutlehautparleur.com/m33-diaphragm-for-rcf-nd650-cd650-8-ohm.html
i also like how there seems to be some funky engineering going on if you look closely at the diaphragm pics at link above.
it seems titanium doesn't touch the VC, but rather is glued to some thick clear plastic with a visible gap between titanium and the VC that light shines through:
this would have the effect of damping the edge of the titanium dome making it less resonant ... while still maintaining the dimensional stability and power handling of titanium ... brilliant if you ask me ... assuming it is what it looks like ... i mean it could simply be how they glue surround to the dome
you don't need the entire surface of material to have high damping - you only need to introduce damping in certain parts of the diaphragm to control the modes. perhaps damping only the edge of diaphragm won't control some of the higher resonance modes but it's better than nothing and in a fairly straightforward solution. anyway this is just speculation - can't tell for sure from those pics.
i remember reading some JBL paper where the gist was that the sound of a titanium dome is all in the surround ... which is probably why most don't like to experiment with surround too much because it changes the sound so much ... but here something creative is going on and it seems to be working based on frequency response chart:
https://www.rcf.it/en/products/prod...tlet_ProductDownloadsPortlet_profileId=251508
actually now that i think of it that clear plastic could be the former. bent edge formers are all the rage these days because they make for a better bond to the diaphragm and in this case they could also engineer some damping into it by allowing just the right amount of flex.
well i don't know what it is. but it looks cool. i like it.
it lists frequency range as starting form 700 hz and that's where i would cross it.
https://www.rcf.it/en/products/product-detail/nd650
by better i mean it's 2.5" versus 3" but still has the same construction of titanium dome with soft surround and low FS
somehow missed this driver on 1st round of search because it said "pure titanium" so i assumed it meant titanium surround, which i do not want ...
however it is in fact titanium dome with plastic surround and it's just $60 for replacement diaphragm:
https://en.toutlehautparleur.com/m33-diaphragm-for-rcf-nd650-cd650-8-ohm.html
i also like how there seems to be some funky engineering going on if you look closely at the diaphragm pics at link above.
it seems titanium doesn't touch the VC, but rather is glued to some thick clear plastic with a visible gap between titanium and the VC that light shines through:
this would have the effect of damping the edge of the titanium dome making it less resonant ... while still maintaining the dimensional stability and power handling of titanium ... brilliant if you ask me ... assuming it is what it looks like ... i mean it could simply be how they glue surround to the dome
you don't need the entire surface of material to have high damping - you only need to introduce damping in certain parts of the diaphragm to control the modes. perhaps damping only the edge of diaphragm won't control some of the higher resonance modes but it's better than nothing and in a fairly straightforward solution. anyway this is just speculation - can't tell for sure from those pics.
i remember reading some JBL paper where the gist was that the sound of a titanium dome is all in the surround ... which is probably why most don't like to experiment with surround too much because it changes the sound so much ... but here something creative is going on and it seems to be working based on frequency response chart:
https://www.rcf.it/en/products/prod...tlet_ProductDownloadsPortlet_profileId=251508
actually now that i think of it that clear plastic could be the former. bent edge formers are all the rage these days because they make for a better bond to the diaphragm and in this case they could also engineer some damping into it by allowing just the right amount of flex.
well i don't know what it is. but it looks cool. i like it.
it lists frequency range as starting form 700 hz and that's where i would cross it.
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