Two Way or Three Way Compression driver horn speaker

[milezone]

Hi I'm interested in building a two way or three way compression driver + woofer speaker. I've been planning to do this for some time and finally have the space and resources to do so. The build I have in mind is based on a TAD style Yuichi horn system. I don't want to go larger than an A480/A290 horn and prefer a suitable waveguide to a formal horn if possible. The less horn loading the better in my listening experiences. That said I am interested a lowering the crossover frequency of the compression driver as much as possible in the interest if achieving maximum midrange detail. Typically a larger horn enables a lower crossover frequency and increased sensitivity, which was a useful thing in the olden times when wattage was scarce.

I'm curious about peoples' experiences comparing various drivers first hand -- I'm all over the map with regards to which driver to use -- TAD 1.4"/2" would be ideal however the high price and scarcity are deterrents. The other considerations are older Altecs like the 802s or 209s if a three way which can be crossed to around 300hz. And also more contemporary brands like Faital, BMS (single and two way compression drivers), Radian, Beyma, and 18Sound. Faital is particularly interesting as they implement a "Ketone Polymer" diaphragm which as I understand it has breakup characteristics (around 9khz) closer to Beryllium than those of Aluminum or Titanium -- http://www.vueaudio.com/wp-content/uploads/2012/04/BerylliumChart_FIN.pdf.

Does anyone have experience with these drivers, new or old, or others? Which do you prefer and in what sort of implementation? Part of me would like to start with something older like an Altec driver as I find vintage pro audio gear to be excellent and see that people often tend to prefer these vintage designs to more contemporary -- high tech drivers for one reason or another. Any suggestions are much appreciated. Thanks.

 

[MakeMineVinyl]

[QUOTE="milezone, post: 540885, member: 7834" Part of me would like to start with something older like an Altec driver as I find vintage pro audio gear to be excellent and see that people often tend to prefer these vintage designs to more contemporary -- high tech drivers for one reason or another. [/QUOTE]

The old Altec drivers like the 802D are excellent, however I wouldn't think the effort in finding good-condition specimens and probably having to purchase new diaphragms would be worth the effort unless you simply enjoy restoration work like that.

 

[Wombat]

Buy new Altec drivers, parts, rebuilds and remags:

https://greatplainsaudio.com/

I have GPA(Altec) 802 diaphragms in my old 808 CDs, giving me 802 CDs. 808s are cheapish. Add a remag(needed on old 802s, anyhow) and GPA 802 diaphrams and you have superb CD drivers.

P.S. 1 inch compression drivers are usually better for home audio.

JBL 2404H 'baby butt cheek' horn tweeters are fairly easy to find. Make sure they have genuine JBL diaphragms.

This forum may be of interest. It is focused on practicality and is very supportive of newbies and DIY horn projects but not of time-wasters.

https://www.hostboard.com/forums/f700/altec-users-board.html

 

[milezone]

I appreciate the suggestions with regards to Altec drivers. Part of the benefit of a compression driver -- along with increased detail and reduced distortion in the midrange -- is a larger sound, compared to an anemic 4" full range driver at the other end of the spectrum for example. While it in no way serves it's intended purpose in home use, I think there is merit, in the case of a music addicted person like myself, in using a 2" throat driver even for home audio. I owned a pair of JBL 4425s long ago with baby butt cheek horns. I didn't like that speaker one bit -- in fact my least favorite speaker I've ever owned. I've heard a massive version of the same shape horn on a $50k speaker and again it sounded bad and very colored due to the nature of the horn and horn loading. I'm trying to avoid that effect whatever it was which I would describe as nasal congestion -- veiled versus some horn speakers like a TAD two way which is supposedly clear as day. I'm seeking clarity more than anything else when building with compression drivers. I don't care for horn flavor or coloration or anything like that. It was a pair of 12" Tannoy silvers which I heard earlier this year that piqued my interest. I'm about to buy a pair of Beyma 12" woofer/compression driver coaxes to experiment with however I figure I can maybe do better with a nicer compression driver, woofer combination, that can crossover 500ish hertz lower, and a simple waveguide/constant directivity style horn, and finally some home brew dsp. I've always had a fondness for panel speakers. A cheap pair of Stax headphones is still the most superior transducer in my listening experience. I'm attracted to the simplicity of a cone speaker compared to large panels. I'm curious whether better directivity, and the right horn compression driver combo can yield equal or better sound than a panel. The only other design of interest these days are compact omni speakers however that's more of a long term project/goal -- a stereo pair of home pods for example sounds outstanding at that price and form factor.

 

[Wombat]

I appreciate the suggestions with regards to Altec drivers. Part of the benefit of a compression driver -- along with increased detail and reduced distortion in the midrange -- is a larger sound, compared to an anemic 4" full range driver at the other end of the spectrum for example. While it in no way serves it's intended purpose in home use, I think there is merit, in the case of a music addicted person like myself, in using a 2" throat driver even for home audio. I owned a pair of JBL 4425s long ago with baby butt cheek horns. I didn't like that speaker one bit -- in fact my least favorite speaker I've ever owned. I've heard a massive version of the same shape horn on a $50k speaker and again it sounded bad and very colored due to the nature of the horn and horn loading. I'm trying to avoid that effect whatever it was which I would describe as nasal congestion -- veiled versus some horn speakers like a TAD two way which is supposedly clear as day. I'm seeking clarity more than anything else when building with compression drivers. I don't care for horn flavor or coloration or anything like that. It was a pair of 12" Tannoy silvers which I heard earlier this year that piqued my interest. I'm about to buy a pair of Beyma 12" woofer/compression driver coaxes to experiment with however I figure I can maybe do better with a nicer compression driver, woofer combination, that can crossover 500ish hertz lower, and a simple waveguide/constant directivity style horn, and finally some home brew dsp. I've always had a fondness for panel speakers. A cheap pair of Stax headphones is still the most superior transducer in my listening experience. I'm attracted to the simplicity of a cone speaker compared to large panels. I'm curious whether better directivity, and the right horn compression driver combo can yield equal or better sound than a panel. The only other design of interest these days are compact omni speakers however that's more of a long term project/goal -- a stereo pair of home pods for example sounds outstanding at that price and form factor.

I wish you well on a very long journey. Getting to listen to a wide range of speakers incorporating CD driven horns is next to impossible. LF horns become a size problem for most people. Room size is important.
Over a period of 30 years or so I studied articles and papers on the subject, heard systems and helped friends build their systems. I found the speakers to be exciting enough to lean in that direction. Pure preference.

Try some Altec Valencia or Stonehenge III as a starting point. You will have no trouble onselling them. If you don't like them then you may not like the other domestic offerings that are less than esoteric/astronomic in price.

http://akdatabase.org/AKview/albums/userpics/10007/Altec-Lansing Brochure.pdf

P.S. The 'baby butt cheek' horns are fine tweeters. Application and integration are what matters.

Note: One can buy and try a myriad of components in various configurations but without understanding the design considerations it will become an expensive and fruitless endeavour.

 

[beagleman]

I have heard horns I love, but after then going back to a normal mid or tweeter, start to prefer the cone or dome speaker.

But then I start reminiscing about the horn sound and go back.
Could this just be wanting what we do not have and then losing interest?

 

[MakeMineVinyl]

I have heard horns I love, but after then going back to a normal mid or tweeter, start to prefer the cone or dome speaker.

But then I start reminiscing about the horn sound and go back.
Could this just be wanting what we do not have and then losing interest?

Horns have an immediacy and 'jump factor' which cones/domes don't. Horns don't have to 'sound like horns' in the pejorative sense to accomplish this if done right.

 

[andreasmaaan]

Sounds like a nice project What are your intended dimensions, and frequency range for each horn/driver? And what are you hoping to achieve by using horns (e.g. controlled directivity, high SPLs, low distortion, etc.).

 

[milezone]

MMV, that I agree with. I despise the horn sound/honk/rattling resonance and the like to be frank. More often than not I find that hifi, public address and some pro audio horn implementations have this issue. Waveguides and properly implemented horn --> driver matching/coupling are a different story.

 

[milezone]

Sounds like a nice project What are your intended dimensions, and frequency range for each horn/driver? And what are you hoping to achieve by using horns (e.g. controlled directivity, high SPLs, low distortion, etc.).

I'm trying to go as compact as possible but don't have an initial dimension or enclosure in mind. For the sake of preliminary experimentation I'm going to use 3/4" ply attached to a cage nut 19" rack frame, probably ~24 inches in height, that way I can swap out baffles, ported/vs non ported panels, bracing, etc. very easily. I have plenty of space and also intend to experiment with open baffle implementations which I consider to be superior if there's enough distance between the rear wall and the speaker.

What I would like to achieve -- low distortion first and foremost, controlled directivity probably equal, and high spls not a priority but a nice bonus knowing that even at high volumes the speakers will remain composed -- unlike many panels, full range drivers, and many audiophile speaker implementations.

 

[andreasmaaan]

I'm trying to go as compact as possible but don't have an initial dimension or enclosure in mind. For the sake of preliminary experimentation I'm going to use 3/4" ply attached to a cage nut 19" rack frame, probably ~24 inches in height, that way I can swap out baffles, ported/vs non ported panels, bracing, etc. very easily. I have plenty of space and also intend to experiment with open baffle implementations which I consider to be superior if there's enough distance between the rear wall and the speaker.

What I would like to achieve -- low distortion first and foremost, controlled directivity probably equal, and high spls not a priority but a nice bonus knowing that it's even at high volumes the speakers will remain composed -- unlike many panels, full range drivers, and many audiophile speaker implementations.

That's helpful, thanks. What kind of directivity profile do you want to achieve?

 

[milezone]

I don't know too much about the variety of directivity patterns and their different benefits. I would say I care more about coherence in a +/- 30 degree range over wide and tall projection of sound at the expense of clarity. I'm of the belief that a figure eight dispersion pattern -- dipoles like the Linkwitz lx521, and panel speakers, have benefits over cardioid response basic box speakers. https://www.linkwitzlab.com/frontiers.htm -- hence my interest in open baffle designs. I think this is also the motivation behind the Kii 3, though achieved through active cancellation of a very different sort.

These are the plots for what I presume to be pretty ideal directivity -- Genelec S360A. If I can approach something like this I figure I'm doing well:

And here's one for the Dutch and Dutch 8C:

Some of the contemporary coaxial speakers I've been looking at seem to have excellent directivity specs inherently. In addition, Faital Pro drivers, especially those with ketone polymer diaphragms, seem to measure substantially better than competitor products.

 

[andreasmaaan]

I don't know too much about the variety of directivity patterns and their different benefits. I would say I care more about coherence in a +/- 30 degree range over wide and tall projection of sound at the expense of clarity. I'm of the belief that a figure eight dispersion pattern -- dipoles like the Linkwitz lx521, and panel speakers, have benefits over cardioid response basic box speakers. https://www.linkwitzlab.com/frontiers.htm -- hence my interest in open baffle designs.

The figure-of-eight directivity of a dipole speaker will obviously not be possible to achieve with a single horn. For an example of the kind of direciticity you might achieve with such a speaker, here is the 360° directivity plot of the Gainphile R16:

The woofer's output is dipolar, while obviously the HF horn's is not. This is what the speaker looks like btw:

I think this is also the motivation behind the Kii 3, though achieved through active cancellation of a very different sort.

The Kii has a rather different radiation pattern, with (more or less) no output to the rear, but roughly 120° frontal output. This could be achieved with a constant-directivity horn on the HF driver and a cardioid midwoofer (for example).

Some of the contemporary coaxial speakers I've been looking at seem to have excellent directivity specs inherently. In addition, Faital Pro drivers, especially those with ketone polymer diaphragms, seem to measure substantially better than competitor products.

Could you share some measurements of the Faital drivers you're referring to? In general, cone material is relatively unimportant when it comes to woofer performance, so I wouldn't get too hung up on it if I were you.

 

[milezone]

The Gainphile, Gedlee, etc. wave guide is similar in my observation to the Genelec s360 waveguide posted above -- minimal if any horn loading/mechanical compression in the horn throat. Seems like an interesting and simple design. I have no experience with those Seas drivers though people seem to like them. Yes that's obvious about the compression driver not being suited for dipole dispersion. Here's an interesting note about electrostatic directivity:

In the case of compression drivers it's my understanding that driver material makes all the difference -- with regards to reducing audible distortion. See this posted earlier: http://www.vueaudio.com/wp-content/uploads/2012/04/BerylliumChart_FIN.pdf.

Here are some plots of some randomly selected compression drivers -- The first two -- Faital Pro are Ketone Polymer, the rest are Titanium and one Radian's top of the line Beryllium:

HF108R

HF200

951BE

DE1085TN

DE610

DE750TN

In my limited understanding of things, my perception is that the drop off in frequency around 10khz is a result of driver material distortion starting around 2khz-5khz, excluding the Faital drivers, which in turn causes cancellation nodes (modes?) and reduction in frequency response, breakup/distortion and all sorts of other crap. I spoke with a guy who at the time was developing a carbon composite dome for compression drivers called Textreme at an AES show in California a year or so ago -- now available to purchase in some Eminence CDs. He was adamant that driver diaphragm material matters a lot. I am too. It seems the Italian Faital Pro, if honest in their representation of data, performs better even than the 'bleeding edge' Textreme domes found in those Eminence drivers. Unfortunately none of these companies provide information about testing conditions, horns, no horns, etc. A couple people in the industry whose options I trust very much also recommend these drivers over others.

 

[andreasmaaan]

Yes that's obvious about the compression driver not being suited for dipole dispersion. Here's an interesting note about electrostatic directivity:

View attachment 88065

In the case of compression drivers it's my understanding that driver material makes all the difference -- with regards to reducing audible distortion. See this posted earlier: http://www.vueaudio.com/wp-content/uploads/2012/04/BerylliumChart_FIN.pdf.

Here are some plots of some randomly selected compression drivers -- The first two -- Faital Pro are Ketone Polymer, the rest are Titanium and one Radian's top of the line Beryllium:

HF108R
View attachment 88066

HF200
View attachment 88067

951BE
View attachment 88068

DE1085TN
View attachment 88069

DE610
View attachment 88070

DE750TN
View attachment 88071

In my limited understanding of things, my perception is that the drop off in frequency around 10khz is a result of driver material distortion which in turn causes cancellation nodes and reduction in frequency response, breakup/distortion and all sorts of other crap. I spoke with a guy who at the time was developing a carbon composite dome for compression drivers called Textreme at an AES show in California a year or so ago -- now available to purchase in some Eminence CDs. He was adamant that driver material matters a lot. I am too. It seems the Italian Faital Pro, if honest in their representation of the data, performs better even than the 'bleeding edge' Textreme domes found in those Eminence drivers.

Not exactly... Those graphs are not comparing apples to apples, because all those drivers have different diaphragm surface areas, throat exits, and compression ratios.

Regarding the link you posted comparing those three metals, yes, beryllium is theoretically the best material for a compression driver of those three you've listed. However, when it comes to the real world, for a given application, a driver made of some other material may be better suited (not because it's made of X material, but because it is, for whatever reasons, a better driver for the application). All else equal though, a beryllium driver can be made to be larger than a titanium or aluminium driver for the same diaphragm break-up frequency. This means that either it can (at least theoretically) cover a wider bandwidth for a given size, or be made slightly larger to cover the same bandwidth (resulting in theoretically lower distortion at low frequencies). An interesting comparison of two otherwise similar drivers, one beryllium and one aluminium, can be found here. You'll find that the main difference is that the beryllium driver breaks up at a higher frequency. Otherwise the two drivers measure very similarly.

Now, you don't have to listen to me ofc But I've designed a number of horn speakers, and tested a lot of compression drivers, and as it turns out, the HF drivers I keep coming back to for the applications that tend to fit my needs happen not to be made of beryllium.

FWIW, this is my preferred compression driver for moderate level (<125dB) HF (1500Hz+) applications. It is titanium. It's first break-up mode is above the audio band. It's nonlinear distortion performance between 1500 and 20,000Hz is as good as any I've found.

Yes, I could use a larger-diaphragm beryllium driver and cross it over lower in frequency than this titanium driver. But I prefer a 1" exit for a HF driver; the larger-format compression drivers all tend to have exits between 1.4" and 2", which compromises directivity in the top couple of octaves and tends to lead to HOMs developing in the horn throat.

In other words, when throat exit is limited to 1", which IMHO it must be if high-fidelity high-frequency reproduction with controlled directivity is a goal, there has proven to be no advantage to using beryllium in my designs - aluminium and titanium (for example) are capable of pistonic motion right up to 20kHz given the range of diaphragm sizes that are sensible for a 1" exit (that is, diaphragms of 1.7" or smaller).

 

[milezone]

Not exactly... Those graphs are not comparing apples to apples, because all those drivers have different diaphragm surface areas, throat exits, and compression ratios.

I don't contend that. Interesting about the B&C driver that you like. If you happen to experiment with other drivers, perhaps the Faital Pro's which are at a similar price point, I would be curious to hear your experience.

At less than half the density of titanium, all else being equal, beryllium should be able to render twice the resolution of titanium -- as best perceived in the speed of transient response of an impulse and or the accurate rendition of decay.

How are you determining that the first break up mode is above the audio band? And are you measuring non-linear distortion and if so how?

Can you elaborate on why high fidelity and high frquency reproduction with controlled directivity is only achievable with a 1" throat exit? I can't imagine that perhaps the most sought after studio monitors in the world featuring 2" throat TAD 4001 drivers fall short in any way compared to your 1" implementation though I have no idea having heard neither.

 

[Sal1950]

Buy new Altec drivers, parts, rebuilds and remags:

https://www.hostboard.com/forums/f700/altec-users-board.html

Thanks for the links @Wombat ! What interesting places to poke around and read. Wish I was younger with room and finances to get involved in DIY builds.

 

[andreasmaaan]

I don't contend that. Interesting about the B&C driver that you like. If you happen to experiment with other drivers, perhaps the Faital Pro's which are at a similar price point, I would be curious to hear your experience.

Yes I considered testing those drivers. Unfortunately I did not have a great experience with the Faital distributor where I am, and did not pursue them further after finding adequate drivers through B&C.

Voice Coil did test that HF108R driver, however, and it looked to measure quite similarly to the DE502 I linked you to before (assuming my measurements are comparable with Voice Coil's, which is a big assumption, the DE502's nonlinear distortion is lower below 3kHz and higher above it), apart from the HF108R's little peak followed by steep drop-off just before 20kHz (which in any case may well have been due to poor integration with the horn on which it was measured).

Can you elaborate on why high fidelity and high frquency reproduction with controlled directivity is only achievable with a 1" throat exit? I can't imagine the perhaps the most sought after studio monitors in the world featuring 2" throat TAD 4001 drivers fall short in any compared to your 1" implementation though I have no idea having heard neither.

In terms of directivity, it's simply to do with the wavelength of high-frequency sounds. A wavelength of 1" corresponds to a frequency of 13.5kHz. Any 1" exit driver will tend to start beaming and/or behaving in a less controlled manner above that frequency. Increase the throat diameter and this behaviour begins lower in frequency. 1", however, is a reasonable compromise IMHO.

Regarding high-fidelity, similar considerations apply. The larger the exit, the lower in frequency HOMs will begin to develop. This is not necessarily fatal, however, and I've seen larger-exit CDs with relatively clean FR and time-domain behaviour in the high frequencies. But once again, IME I've found 1" to be a good compromise.

Which studio monitor are you referring to specifically? Could you post some measurements if they're available? I'd be interested to see how the driver/horn performs off-axis. Alternatively, if they're nearfield monitors, wide or even dispersion in the very high frequencies may be considered to be less important.

 

[milezone]

Ah right beaming. I presume that's less of an issue compared with flat panel drivers like electrostatic ones due to the convex/concave? shape of a compression driver diaphragm. Perhaps an over simplification.

The studio monitor, mains, not near field though presumably they are excellent for near field listening too, which I had in mind is the TAD TSM-1. Pictured here:

And a variant here:

And also these, a variant of a speaker which TAD custom built for Skywalker Sound featuring a dipole bass array for near field listening...

https://www.pioneerelectronics.com/...,+TSC-3215,+TSC-1118SW+Cinema+Speaker+Systems

Also here's a picture of the guy in the second picture's custom DSD recorder dated to 2014. Things have downsized a lot since then:

 

[andreasmaaan]

Ah right beaming. I presume that's less of an issue compared with flat panel drivers like electrostatic ones due to the convex shape of a compression driver diaphragm. Perhaps an over simplification.

The shape of the diaphragm is not so important, actually. The phase plug of a compression driver guides the the sound from the surface of the diaphragm to the exit into the horn throat (the blue thing in the pic below - which is a TAD btw). It is the action of the phase plug that is important, and the effectiveness of its functioning as it guides the sound from the diaphragm surface to the exit. But yes, it certainly tends to be less of an issue with CDs vs electrostats, which tend to be very large relative to the typical dimensions of a CD exit.

The studio monitor, mains, not near field though presumably they are excellent for near field listening to, which I had in mind is the TAD TSM-1. Pictured here:

I'm not able to find measurements, so it's hard to say for sure. The 4001 is an excellent, low-distortion, wide-bandwidth driver. I've never measured it though. Would be very unlikely that controlled directivity is maintained to a high frequency with that 2" throat, but ofc any design involves compromises and presumably the designers in this case considered it a worthwhile trade-off. My preferences in terms of trade-offs are certainly not the only way to do it.

Anyway, if I were you I would start by deciding what you want your speaker to do. That would include, most importantly:

• Size/weight
• Bandwidth
• Max. SPL
• Directivity characteristics
• Whether it will be passive or active

...and a couple of less central but also important considerations.

Then, when you've decided on your design goals, look for components that will allow you to achieve them. I think a classic mistake in DIY is beginning from a particular component or component type, and then working backwards to the actual speaker. Your components should serve your speaker - not the other way around.

Hope that's helpful