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Backwards directed , rear-firing tweeter, Snell Type E / III?

eddantes

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Andrew Welker of Axiom is another designer that's produced a number of dipole designs while he was with API (Mirage) and now with Axiom

The legendary Mirage M1

2ba519b697327c5a0f87318edb777cda.jpg


A current Axiom Model Omni LFR1100

1642180579581.png
 

cavedriver

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Just boosting this thread with my minority opinion of these speakers. I still have an original pair of E/IIIs that I bought new around 1991. For my unprofessional ears these speakers have stood the test of time although I mainly use them for general TV watching these days. They are relatively accurate, relatively flat, have few objectional flaws, play with speed and liveliness without any harshness, and have a great depth of soundstage. The Vifa tweeters and Scanspeak woofers were (and still are) high quality components that Snell accurately matched. They are easy to drive with low power amps, play fairly loud without distortion, and have respectable bass extension. Where they are weak is a bit too much warmth in the low bass, some distortion (muddiness) in the low bass, poor directionality and imaging, are sensitive to wall placement behind them, should really be up on "shorty" stands as mentioned above, and they are a tad soft in the highs compared to some modern speakers that are very precise and detailed.

But you also have to put them in historic context. In the 90's I listened to all the common stuff that was in audio stores at the time - Polk, Infinity, Paradigm, B&W, Boston Acoustics, and who knows what else that I've forgotten. Frankly, nothing else could touch these for the money. Granted I could have got some used electrostatics or JBLs or maybe Klipsch but they were rare and I didn't know to look for them. If I more than doubled the spend I thought the nicer Paradigm's were better, or the 800-series B&W's of the day, but those were major spends. Also, because of the efficiency I could drive them with a plucky little Onkyo 80 Wpc receiver instead of some 200 wpc NAD's or Adcom's. As a side note they have beautiful matching walnut veneers you rarely see today (although are basically just large boxes). Today they of course are easily bested by speakers under 2k and perhaps under 1k depending on your criteria, but when you find them in good condition on the used market at under $500 they are once again a bargain. Unfortunately sometimes people refoamed them after the woofer spider has been damaged or use inappropriate foam and the performance is degraded. Virtually every original example has had all it's foam rot off the woofer. Mine have newish OEM woofers direct from Atomic with matched crossover components (a coil and a capacitor, iirc).
 
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cavedriver

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Also, specifically regarding the rear tweeter, no, I don't think it's a dipole, it's an omni. The above linked Stereophile review even discusses how it is crossed in with the front tweeter on a rising output curve starting at around 6kHz to reduce directionality of the main tweeters and add "depth" (my emphasis). I will say that I don't mind the effect although I know it's an effect and my brain has observed it, accepted it, and learned to like the pieces where it helps and ignore the loss of resolution it creates in others. My pair is set about 8 feet apart and 10 feet from the listener. They are barely canted in at all as canting them in really narrows the soundstage. I have them about a foot from the rear wall which is pretty close to ideal for these (maybe a tad close, I think I've seen where 15-18" was recommended). Where the effect helps is depth of soundstage in things like large symphony pieces and atmospheric stuff. The track that clinched them for me originally was Another Brick in the Wall, pt. 1/Happiest Days of Our Lives, with Gilmour's rambling interjecting guitar and the helicopter flying across. They also play Voodoo Child really well. I have not listened to enough other omni speakers to judge if I always like the effect or if the others do it better/worse than the Snell's. By the E/IV version they had added a "defeat" switch that could turn the rear tweeter off, presumably due to criticism by customers or reviewers, but they had also ruined the speaker by then by replacing the silk Vifa tweeter with an aluminum one and going with a taller and narrower box that was in vogue by then. They definitely do not sound like dipoles from the era such as Definitive Technologies, which sound like complete mush to me.
 

HeadDoc12

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Von Schweikert Audio do this in their most expensive speakers. A tweeter (or two!) on the back of the speaker for soundstage or something, plus two different tweeters in the front. They are highly adjustable speakers, as well, so you can adjust the output of each front-firing tweeter, and the rear tweeter "array," all separately. NO IDEA how they sound or measure.
 

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Thanks Duke, that was interesting! Fun with a different view of it.With your speakers, it is a fixed setting with a passive crossover filter or you have the option to regulate it, similar like Snell Type E / III? Do you have a picture of your speakers? It would be exciting to see.:)

Sorry I forgot to come back and do this!

Here are pictures of the front and back of one of my speakers:

7-594.jpg
13-604.jpg



Level and "tilt" controls for the rear-firing horn are in the large rectangular cup in the upper-left quadrant of the rear of the cabinet.
 
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cavedriver

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Level and "tilt" controls for the rear-firing horn are in the large rectangular cup in the upper-left quadrant of the rear of the cabinet.
Pretty cool! Would be fascinating to listen to these. I assume the other three cups are direct access to power the front tweeter, woofer, and rear tweeter? Assuming there is a crossover inside what type is it? Are all four ports for the woofer chamber? The cabinet is asymmetric for the rear tweeter- was this the right speaker of the pair?
 

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Had Snell EII I think , then they got thinner and longer and not so wide and they actually got worse ? Hard to remember.
Had a lot of fun with them easy to drive .

But the design of EII is extremely dated by today’s standard at best experimental, wonder what peter snell could have done with today’s knowledge and research ?

No one should design two way speakers with an 8” crossed over to a soft dome tweeter :) no waveguide and a wide cabinet with protruding edges ?

But by all means if find a pair in a second hand store , have fun .

Btw I remember when Audio Note was beginning to make knockoffs of the original snell designs , they where not much more expensive . But it quickly spiralled out of control AN speaker may look like an EII but everything is changed and ridiculously expensive. Knowing that AN is some kind of anti hifi ( the products seem to get worse and more expensive over time ) I would not bet on them being any better.
 

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Pretty cool! Would be fascinating to listen to these. I assume the other three cups are direct access to power the front tweeter, woofer, and rear tweeter?

Thanks!

One of the bottom input terminal cups is for the main drivers, and the other is for the rear-firing horn. The upside-down input terminal cup up high on the back of the cabinet is for an external resistor which acts as a "tilt" control for the front-firing horn; that is, it has more effect at 10 kHz than it does down at 2 kHz.

Assuming there is a crossover inside what type is it?

It's a passive crossover at about 1.4 kHz. The initial acoustic slopes are fairly gradual, and then they accelerate to being fairly steep.

Are all four ports for the woofer chamber?

Yes. The ports are each pluggable, enabling some passive response-shaping of the low end for different room acoustic situations. All four ports open would be for when the speakers are getting minimal boundary reinforcement, like if they are in a large room and well away from the corners.

The cabinet is asymmetric for the rear tweeter- was this the right speaker of the pair?

The cabinets are mirror-imaged with respect to the round holes on one side of the rear horn's "notch" (and also with respect to the cups above the notch). Whether the round holes are on the "inside" or "outside" for a stereo pair depends on the set-up specifics. I normally use a lot of toe-in, such that the speaker axes criss-cross in front of the central "sweet spot", in which case I'd normally put the round holes facing the "inside". In that case, the speaker shown would actually be the left speaker.
 
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cavedriver

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No one should design two way speakers with an 8” crossed over to a soft dome tweeter :) no waveguide and a wide cabinet with protruding edges ?

Btw I remember when Audio Note was beginning to make knockoffs of the original snell designs , they where not much more expensive . But it quickly spiralled out of control AN speaker may look like an EII but everything is changed and ridiculously expensive. Knowing that AN is some kind of anti hifi ( the products seem to get worse and more expensive over time ) I would not bet on them being any better.
I haven't heard the AN's but I intend to, but be aware that this style of speaker has been making a comeback in the form of the Devore's, and recently news to me, an Austrian company called Tenner and Friedl, in addition to the Zu's and AN's. Somewhere I read a sound theory assessment that suggested the large flat face of the box with centrally located tweeter had a purpose and could actually sound better for some reason. Supposedly this person argued that the narrower cabinets were not to reduce diffraction but rather to take up less space in people's living rooms. Note that there are a number speakers with huge soundstages like Klipschorns that have enormous front faces (granted - horns). I'm not saying I know what I'm talking about but I would prefer to see someone show data and analysis on the differences rather than simply conclude, "everyone is building narrower speakers today, they must be better". I wish I could find that article...
 

Duke

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Somewhere I read a sound theory assessment that suggested the large flat face of the box with centrally located tweeter had a purpose and could actually sound better for some reason. Supposedly this person argued that the narrower cabinets were not to reduce diffraction but rather to take up less space in people's living rooms.

At the risk of oversimplifying -

All else being equal, a narrow baffle tends to result in a bit better imaging because the edge diffraction is not delayed in time as much as the edge diffraction with a wider baffle, and that earlier-arriving diffraction is less disruptive of localization cues.

Wider baffles tend to have better performance in the lower midrange because the baffle width itself helps to prevent the sound waves from "wrapping around" the enclosure as we go down in frequency. The longer the sound waves are relative to the baffle width the more they "fold back" and "wrap around" the enclosure, reducing the direct-to-reflected sound ratio and the SPL at the listening position at these longer wavelength. This effect is called the "baffle step" and it can arguably be compensated for in the crossover by attenuating the SPL at frequencies above the baffle step region.

(In a fully bipolar speaker like the Mirage M2, diagram in post #24 above, the rear-firing woofer's wrap-around pretty much fills in for the front-firing-woofer's wrap-around, so the baffle step issue is essentially avoided.)

Supposedly this person argued that the narrower cabinets were not to reduce diffraction but rather to take up less space in people's living rooms.

I agree that this is the most likely reason for the market trend towards narrower cabinets. A wide cabinet with large-radius round-overs, or large bevels, would arguably be a better-sounding solution (assuming we're talking about speakers with conventional direct-radiator drivers).
 
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DanielT

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Just boosting this thread with my minority opinion of these speakers. I still have an original pair of E/IIIs that I bought new around 1991. For my unprofessional ears these speakers have stood the test of time although I mainly use them for general TV watching these days. They are relatively accurate, relatively flat, have few objectional flaws, play with speed and liveliness without any harshness, and have a great depth of soundstage. The Vifa tweeters and Scanspeak woofers were (and still are) high quality components that Snell accurately matched. They are easy to drive with low power amps, play fairly loud without distortion, and have respectable bass extension. Where they are weak is a bit too much warmth in the low bass, some distortion (muddiness) in the low bass, poor directionality and imaging, are sensitive to wall placement behind them, should really be up on "shorty" stands as mentioned above, and they are a tad soft in the highs compared to some modern speakers that are very precise and detailed.

But you also have to put them in historic context. In the 90's I listened to all the common stuff that was in audio stores at the time - Polk, Infinity, Paradigm, B&W, Boston Acoustics, and who knows what else that I've forgotten. Frankly, nothing else could touch these for the money. Granted I could have got some used electrostatics or JBLs or maybe Klipsch but they were rare and I didn't know to look for them. If I more than doubled the spend I thought the nicer Paradigm's were better, or the 800-series B&W's of the day, but those were major spends. Also, because of the efficiency I could drive them with a plucky little Onkyo 80 Wpc receiver instead of some 200 wpc NAD's or Adcom's. As a side note they have beautiful matching walnut veneers you rarely see today (although are basically just large boxes). Today they of course are easily bested by speakers under 2k and perhaps under 1k depending on your criteria, but when you find them in good condition on the used market at under $500 they are once again a bargain. Unfortunately sometimes people refoamed them after the woofer spider has been damaged or use inappropriate foam and the performance is degraded. Virtually every original example has had all it's foam rot off the woofer. Mine have newish OEM woofers direct from Atomic with matched crossover components (a coil and a capacitor, iirc).
Are you sure what type of speaker element it is? Not that it might in itself play a major role, if you are happy and play with them, that is enough, in itself. But the bass element has foam edges. Sooner or later they have to be replaced. There are refoam kits. Try to find as close to the original as possible. Duke (in this thread) can certainly tell you about it (in case it becomes relevant). :)

Here's a refoam kit:

This kit will fit the Snell Type E III & Type E IV speakers that use the Vifa M21WN-07 4ohm woofer and the Snell Type E II speakers that use the Seas H334 CA21FE / B-SN and H170 4 ohm woofer.


A little expensive, I think. I bought a refoam kit for my JPW P1 speakers a while ago. They have bass woofer/ element VIFA M21WG-09. I gave $ 210 for that.
By the way, the JPW P1 are not mine any longer. My mother and father got them and now play with them on a daily basis.:)
Sorry I forgot to come back and do this!

Here are pictures of the front and back of one of my speakers:

View attachment 208020View attachment 208021


Level and "tilt" controls for the rear-firing horn are in the large rectangular cup in the upper-left quadrant of the rear of the cabinet.
Thanks Duke, fun with pictures! They clearly look interesting. When you designed them,did you do so based on a generic idea or are they tailored to be placed in your listening room? With the possibility of placement, type of walls, reflex sound waves, reverb and so on that you have in your listening room?:)
 

cavedriver

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Are you sure what type of speaker element it is? Not that it might in itself play a major role, if you are happy and play with them, that is enough, in itself. But the bass element has foam edges. Sooner or later they have to be replaced. There are refoam kits. Try to find as close to the original as possible. Duke (in this thread) can certainly tell you about it (in case it becomes relevant). :)

Here's a refoam kit:

This kit will fit the Snell Type E III & Type E IV speakers that use the Vifa M21WN-07 4ohm woofer and the Snell Type E II speakers that use the Seas H334 CA21FE / B-SN and H170 4 ohm woofer.
I didn't speak clearly. The original foam on mine rotted a while ago. Rather than replace the foam I actually bought completely new woofers from Atomic Hifi and installed them with the matching replacement crossover components that they sent me. This was just after Snell was finally completely shut down. Atomic is run by an ex-Snell engineer and was the official warranty and parts vendor when Snell shut down. Mine sound great. I also have a complete replacement set of front and rear tweeters that I bought "just in case" a couple years ago (also component matched from Atomic). Maybe I'll install them at some point, haha.
 
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DanielT

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Had Snell EII I think , then they got thinner and longer and not so wide and they actually got worse ? Hard to remember.
Had a lot of fun with them easy to drive .

But the design of EII is extremely dated by today’s standard at best experimental, wonder what peter snell could have done with today’s knowledge and research ?

No one should design two way speakers with an 8” crossed over to a soft dome tweeter :) no waveguide and a wide cabinet with protruding edges ?

But by all means if find a pair in a second hand store , have fun .

Btw I remember when Audio Note was beginning to make knockoffs of the original snell designs , they where not much more expensive . But it quickly spiralled out of control AN speaker may look like an EII but everything is changed and ridiculously expensive. Knowing that AN is some kind of anti hifi ( the products seem to get worse and more expensive over time ) I would not bet on them being any better.
Wavegudie, or horn itself is not a requirement. It may not be necessary if the baffle is wide enough. In addition, waveguide is a matter of exactly that, creating a guide of sound, a directivity. Then whether you like it or not is more a matter of taste.:)

However, to get a sensible crossover between an eight-inch bass element and a small soft dome tweeter in a good way. Well, let's say it's a challenge. There I agree with you.

By the way, what's wrong with a wide baffle? On the contrary, it's good. Facilitates that Duke is in on regardning problems / challenges with baffle step compensation. Here is an example of a speaker with a wide baffle. That model was, perhaps still is?, popular:

Heco Direkt Dreiklang:

9-7105-white-1.jpg

Edit:

Sufficiently wide baffle in relation to crossoverpoint, how the sound radiates at different frequencies, then (PERHAPS?)no waveguide is needed. The only question is how wide / large baffle that is needed?Plus round (how big / round?) Baffle edges, so that sound does not bounce but "slips around". That's something that Duke most certainly can tell more about and is thinking about regarding speaker design.

In addition, you can choose the type of dispersion you want, see::)

 
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cavedriver

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That model was, perhaps still is?, popular:

Heco Direkt Dreiklang:

View attachment 208124
Darn the specs on that Heco, looks like I speaker I would really like, could be great with a tube amp with sensitivity at 98dB, but also capable of being driven with 350W RMS. Unfortunately according to their website they seem to have discontinued the entire Direkt series. Rats. Probably very, very rare used in the US.
 

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Thanks Duke, fun with pictures! They clearly look interesting. When you designed them,did you do so based on a generic idea or are they tailored to be placed in your listening room? With the possibility of placement, type of walls, reflex sound waves, reverb and so on that you have in your listening room?:)

The design is intended to work in a wide variety of rooms, and over a wide range of speaker-to-wall distances.

The conceptual starting point was this: What would good speaker/room interaction look like? Arguably it would include a good first-arrival sound; then a time gap with relatively little reflected energy; then when the reflections do start to arrive they are spectrally correct, are neither too strong nor too weak, and decay neither too fast nor too slow.

Normally this sort of speaker/room interaction is implemented primarily by room design and/or extensive room treatment. I am attempting to arrive at approximately the same end result via loudspeaker design alone, without room treatments being required.

I can go into more detail if you'd like.
 
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DanielT

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The design is intended to work in a wide variety of rooms, and over a wide range of speaker-to-wall distances.

The conceptual starting point was this: What would good speaker/room interaction look like? Arguably it would include a good first-arrival sound; then a time gap with relatively little reflected energy; then when the reflections do start to arrive they are spectrally correct, are neither too strong nor too weak, and decay neither too fast nor too slow.

Normally this sort of speaker/room interaction is implemented primarily by room design and/or extensive room treatment. I am attempting to arrive at approximately the same end result via loudspeaker design alone, without room treatments being required.

I can go into more detail if you'd like.
Interesting! Thank you for the explanation.:)

I can go into more detail if you'd like...Yep, feel free to do that. Also interesting!:)
Darn the specs on that Heco, looks like I speaker I would really like, could be great with a tube amp with sensitivity at 98dB, but also capable of being driven with 350W RMS. Unfortunately according to their website they seem to have discontinued the entire Direkt series. Rats. Probably very, very rare used in the US.
One thought, they paired with the tube amplifier. There are more than you who have thought of that. :)
Here's another model in that series, with a tube amplifier:


Duke there you have a commercial opportunity (which you may have already thought of?). Construct speakers with high sensitivity, which have even impedance (no major dips in Ohm) that fits tube amplifiers.:D
 

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Wavegudie, or horn itself is not a requirement. It may not be necessary if the baffle is wide enough. In addition, waveguide is a matter of exactly that, creating a guide of sound, a directivity. Then whether you like it or not is more a matter of taste.:)

However, to get a sensible crossover between an eight-inch bass element and a small soft dome tweeter in a good way. Well, let's say it's a challenge. There I agree with you.

By the way, what's wrong with a wide baffle? On the contrary, it's good. Facilitates that Duke is in on regardning problems / challenges with baffle step compensation. Here is an example of a speaker with a wide baffle. That model was, perhaps still is?, popular:

Heco Direkt Dreiklang:

View attachment 208124
Edit:

Sufficiently wide baffle in relation to crossoverpoint, how the sound radiates at different frequencies, then (PERHAPS?)no waveguide is needed. The only question is how wide / large baffle that is needed?Plus round (how big / round?) Baffle edges, so that sound does not bounce but "slips around". That's something that Duke most certainly can tell more about and is thinking about regarding speaker design.

In addition, you can choose the type of dispersion you want, see::)

Yes but the heco in the picture is a three way. This may not be a problem with wisely chosen driver sizes and xover points .

It’s mostly the 8” directly to a normal tweeter that can be a challenge 3 ways or or two ways with a horn can manage naturally, if the drivers an xover points is choosen correctly

And I do like the idea of wide baffles , not a problem.

It’s just that in the “old days” there where quite a lot of speakers usually two ways with kind of abrupt directivity change at the xover point and a large midbass did not help .

This is probably the reason for the myth that one can not have xover point to low into the midrange between mid/midbass and tweeter, the old solution before one considered constant or smooth directivity , was to move the xover point higher up and make the compromise there where our hearing is less sensitive.
 

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Sorry I forgot to come back and do this!

Here are pictures of the front and back of one of my speakers:

View attachment 208020View attachment 208021


Level and "tilt" controls for the rear-firing horn are in the large rectangular cup in the upper-left quadrant of the rear of the cabinet.
It looks like you put everything back there, INCLUDING the kitchen sink, at least that's what it reminds me of. Fortunately, it's hidden in the back although there's a mini sink in front. Please take this in the spirit it's offered, tongue in cheek.;)
 
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