# Heil Tweeters (AMT) or similar in car?



## less (Nov 30, 2006)

I'm looking for input on Heil or other AMT style tweeters - general commentary or car related if possible. I'm one of those who has to try everything, and I've got a wild hair about trying some of these out. 

I've read and heard a lot of great things about their sound, but haven't listend to them myself. They're certainly bulky and large too - enough so that it'll take some creative installation. Also, I wonder if there is anything peculiar to their operation that would make them suffer in heat or cold car climates.

I've managed to make a lot of things work that don't seem ideal for car installation - but I don't want to mess around only to find out that their operating temp range or humidity tolerance would be an issue. Plus, I'm curious how our members might describe the qualities of their output.

Thanks
Jim aka Less


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## thehatedguy (May 4, 2007)

The ones I have are TINY.


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## ErinH (Feb 14, 2007)

How do they measure, Jason?

I was going to buy some M&D's from a friend but saw Zaph's measurements looked really, really bad.


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## thehatedguy (May 4, 2007)

Jeff Bagby measured the size up from mine and said they measured really well. I posted a link to the big AC AST tests somewhere on here...at work or I would link it again. And the big boy Beyma's measure really well and are supposed to be the king dookie...but for $450 each they should be.

Retail on the RT20021s is like $48 each at Meniscus...might see if they could get you a set to test out.

I went to those after having the 1" Scan Illuminator domes and can't see myself ever wanting to get another set of Scans.


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## hc_TK (Jan 18, 2006)

Have you tried the BG Neo3 tweeters?
These have got some great tests by zaph and are also used in the B80 and B50 Burmester loudspeakers! :O


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## thehatedguy (May 4, 2007)

Long time a go I used them. Just wouldn't physically fit where I wanted to put them this time.

They are excellent tweeters though.


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## Se7en (Mar 28, 2007)

Burmester claims they're using an AMT in the Porsche Panamera. Although it's not entirely clear to me where their being utilized or configured. The one thing that I did read was that the AMTs in the Porsche were the only drivers being powered by class A/B amplification, all other drivers were being powered by class D.

Porsche Technology Glossary


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## Se7en (Mar 28, 2007)

Also, Mark and Daniels is utilizing AMTs in a number of different sizes and configurations, including an up-firing "omni" free standing unit.

Mark And Daniel Of America - Omni-Harmonizer


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## ErinH (Feb 14, 2007)

Se7en said:


> Also, Mark and Daniels is utilizing AMTs in a number of different sizes and configurations, including an up-firing "omni" free standing unit.
> 
> Mark And Daniel Of America - Omni-Harmonizer


That's who I was referring to above. I've heard a lot of their speakers and have been impressed. But they're pretty edgy in sound. When you see measurements it all makes sense.


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## Se7en (Mar 28, 2007)

bikinpunk said:


> That's who I was referring to above. I've heard a lot of their speakers and have been impressed. But they're pretty edgy in sound. When you see measurements it all makes sense.


10-4. I think that I missed tyour MD reference on my first read through. Honestly, I think I was more impressed by their tiny mid bass drivers (I heard the Ruby's) than I was the tweeter too. With that said, it's one of their smallest applications and I would expect one of the larger drive units to perform better over a broader range. 

On an aside, did you get my PM by chance?


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## less (Nov 30, 2006)

Thanks for the info - I found the Airborne AMTs for $78 each on Meniscus... am I reading it right that you're using these and prefer them to the Scan domes. That gets my attention and I may want to give them a go... what the heck! Coincidentally, I just sold my Scan domes =) and just wanted to try something new. 

Is there another model that isn't being sold by Meniscus but made by the name company? I've seen the parts express options, and some by a company called FAL or something (too many $$$), as well as the Beymas... the Airborne are something new, but I got the impression that there is another model available too? I also see used Heils for a fair bit on ebay, and there are replacement ribbons still being made, so there are a few options. I don't know how well they hold up over the years, though. It's cool to see a 20+ year old speaker that still is in demand and performs at the higher end of things.

I tried the BGs but I can't say I really gave them a fair go... they arrived when I'd just received my new Air Circs and I was mentally skewed toward the Scans at the time... had my baffle already built for them. 

I almost read that wrong - tiny does not = tinny! What slopes and points are you using for the RT20021s? I'll probably mate them to my 12ms, but if I cross down near 1000, I might consider going back to a two way front stage coupled to some Utopia 7s or something. On second though, I promised myself no more big projects with this haha... 

Appreciate all the input guys - are there any general words that might describe their character - as compared to more traditional domes? I know - I know, but if something comes to mind that might clarify what to expect, I'd be even more appreciative.

Jim aka Less


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## Se7en (Mar 28, 2007)

For $78 you can't go wrong. I'm not sure how low you'd be able to cross them over. Much like ribbons and planars, size matters. You might start as high as 3-3.5k as a safety.

The only AMTs I've heard were on the M&D speakers and some Adam monitors we have here at work. To describe a sound, I would say crisp, transparent, open, airy, shimmery (in the upper most reaches), extended. 

Cymbals shimmer and vocals can sound focused-razor sharp.

On the cheapest ribbons I've heard, they can sound edgy, bright and "splashy" if that's a reasonable descriptor.

I'm looking forward to hearing your impressions.




less said:


> Thanks for the info - I found the Airborne AMTs for $78 each on Meniscus... am I reading it right that you're using these and prefer them to the Scan domes. That gets my attention and I may want to give them a go... what the heck! Coincidentally, I just sold my Scan domes =) and just wanted to try something new.
> 
> Is there another model that isn't being sold by Meniscus but made by the name company? I've seen the parts express options, and some by a company called FAL or something (too many $$$), as well as the Beymas... the Airborne are something new, but I got the impression that there is another model available too? I also see used Heils for a fair bit on ebay, and there are replacement ribbons still being made, so there are a few options. I don't know how well they hold up over the years, though. It's cool to see a 20+ year old speaker that still is in demand and performs at the higher end of things.
> 
> ...


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## thehatedguy (May 4, 2007)

The ones I have aren't on the Meniscus site, but they stock them. The little RT20021s are about $45 each.

While the radiating pattern might be small, keep in mind the diaphragm is pleated so it has much more surface area to grab the air vs radiating area.

From what I can tell, the OEM company (Hygeia Electrical ºñ¼Íµç×ÓÓÐÏÞ¹«Ë¾ ) puts other people's names on a lot of their product...ELAC, ADAM (as far as I can tell), Martin Logan, etc. Airborne is Solen's house brand


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## Ultimateherts (Nov 13, 2006)

Actually solen carries some under Airborne and looks like they all just differ in size!!!

*The 25cm2 $46.35:*

http://solen.ca/pdf/airborne/rt20021.pdf

*50cm2 $78.43:*

http://solen.ca/pdf/airborne/rt4001.pdf

*95cm2 $106.95:*

http://solen.ca/pdf/airborne/rt5002.pdf


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## thehatedguy (May 4, 2007)

Hygeia Electric= Airborne AST tweeters.

I have the 20021. Take the faceplate off and it becomes the 2002.

Meniscus has all of these, just only the 4001 listed on the site.


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## less (Nov 30, 2006)

Sweet... appreciate the info on these. Pretty much just what I was looking for... and AMT that might even fit my current pods. I don't really have a need to change back to two way, so a small size won't be an issue in running 4-5k+ at 12-48db/oct. 

If the radiating pattern is the same as what I've seen on other AMTs, its about 30 degrees by 120 degrees. That makes it the matter of aligning so the sweet spot spreads across the appropriate space in the car pretty important. Actually, it may be advantageous to not have wide dispersion on all angles, with all the reflective angles in a car.


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## thehatedguy (May 4, 2007)

I chose the small one because it was symmetrical and I figured it would have pretty wide dispersion. I have the little ones crossed at about 5k LR 12 and they have handled all of the volume I have given them so far.


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## less (Nov 30, 2006)

Funny, I've not considered these drivers in years and only a browse through ebays used tweeters reminded me that they were very well received and interesting... but it looks like a lot of big names in the industry have rediscovered these in recent years (Brumester, Dali, Martin Logan and many more). I'm not sure how patents work - but maybe they've found a way to make variations on the design without having to pay Heil his due. 

Anyhow, check these out... they look like another variation, although at a far higher price point. It looks like a dipole design though, and that's probably not ideal for a car system (although my crazy curiousity makes me really want to hear a dipole system in a car before I make that claim!) Anyhow, if anyone knows for sure that these are in fact AMT like and not another ribbon variation, please share what you know.










Aurum cantus


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## less (Nov 30, 2006)

On dispersion, the AMTs claim around 40 degree vertical and 120 horizontal (when aligned with the pleats running up and down). Since the air is squeezed out of aligned "slats" - vertical dispersion is an inherent design limitation that seems difficult to conquer with a flat ribbon design. It'd be really interesting to see a design with a rounded diaphragm though if possible.

Still, in the car we're listening from a fairly fixed location and it seems like wide dispersion might actually be a disadvantage. I'm not an acoustic engineer, but I'm under the impression that reflected sounds arriving at the ear at different times negatively impacts the ear/brain's ability to identify an instrument's location on the sound stage. It seems like it'd take away clarity and muddy up sounds as well. If anyone can clarify or correct me on this, please do, but it seems like covering 1/9th of the vertical range and 1/3 of the horizontal would allow you to easily align these drivers to adequately cover the prime listening areas of a car, yet eliminate a great deal of reflected sound that we may really want to avoid. 

I'm having trouble reconciling this against my impressions of other speaker systems I've heard and respect that use dipole designs though - like my buddy's 7'x4' electrostats which sounded great and even the Bose 901s I tried for a while. You may not like Bose, but if you've ever heard a set of well set up 901s, you'll know that there really is something unusually satisfying about their sound, although its different from most other system's sounds. 

Anyhow, its clear now that I'll be trying some AMT based drivers in the near future and I'm kind of excited. I'm pretty sure I'll end up having to redesign my pods since the smallest of these are too large... so the question now is - which ones? It seems like the diaphragm are the only moving parts, so even old ones should perform well if the diaphragms not too old. I guess I just wonder if new materials have improved any of the newer designs. 

Jim


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## fish (Jun 30, 2007)

Those AC 2560's are going to be used in Mitchyz250's vehicle in the next couple months from what he says. I believe he said he'll remove the faceplates from them to cut dramatically cut down on size.

At $200 a pop, I'm waiting to here back from his results before I take the plunge.


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## less (Nov 30, 2006)

fish said:


> Those AC 2560's are going to be used in Mitchyz250's vehicle in the next couple months from what he says. I believe he said he'll remove the faceplates from them to cut dramatically cut down on size.
> 
> At $200 a pop, I'm waiting to here back from his results before I take the plunge.


The only bad thing about the AC drivers is that they're dipolar (produce sound out both sides), at least according to one user. This can be cured by building a chamber for them - and I think most manufacturers just put a case over the back of their units anyway. Just a thought. 

There's very little info about most of these drivers out there (aside from the Airborne) and the FR charts look identical for all models on those. Still, I think their sonic characteristics make them appealing based on all I've heard.


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## thehatedguy (May 4, 2007)

I have posted a link to some tests of the big AC AST somewhere on the site...if you can't find it, I will repost it when I get off of work today.

Yeah, the AMTs are dipoles...if you want them to be. The chambers don't have to be large, just a hole in some wood with a back on it.


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## less (Nov 30, 2006)

I'd really like some way to compare the newer products with the old Heil drivers. It looks like aside from the "Great Heil," they made two or three other models that were smaller, weighed less, and non-dipole (or pre-cased). I also wonder how long the diaphragms hold up and if the character of their sound changes substantially (audibly) over time. 

I'll search for the info - although I don't see the AC as a top choice for me at the moment - I don't recall even seeing published dimensions for the thing, but I could be wrong. You never know though. Thanks for all the info.

Jim


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## fish (Jun 30, 2007)

thehatedguy said:


> I have posted a link to some tests of the big AC AST somewhere on the site...if you can't find it, I will repost it when I get off of work today.



I think you posted them in this thread...

http://www.diymobileaudio.com/forum...ced/118690-calling-all-jbl-2118h-experts.html


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## thehatedguy (May 4, 2007)

Some real measurements I lifted from the PE site of the little Airborne RT20021 that I use courtesy of Jeff Bagby.


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## less (Nov 30, 2006)

Well what do you know, Burmester uses a HiVi tweeter? Might want to look into this one too:










Hi-Vi RT2C-A Isodynamic Tweeter, 176 mm rnd, 93dB: Madisound Speaker Store

If I read this right, its nearly 6" around and less than an inch deep, and has yet another variation to the AMT - AST name: Isodynamic... I'm going to guess that all the newer models are using Neo magnets, which helps them achieve the thinner profile. This one has some published info too and the fr looks fairly good. It could be another product of Hyglea (sp?) but interesting none-the-less. Priced less than the Scan domes, and recommended xover over 3k. Another similar version is also available at just $40 ea. (Edit) In looking further, MAdisound has 4 total models available from HiVi and Eton, Mundorf and others all have models as well, although their priced fairly outrageously high. Parts Express has the smaller ones in stock, but for $39/driver more! I'd have gone for the lil Airbornes but they won't fit my baffle either, so I thought I'd go for something with a little more radiating area. I wonder how much difference there is between the variations in terms of actual sound quality.


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## masswork (Feb 23, 2009)

I'm using HiVi RT1.3WE.










Mounted in A pillar.

Here's 1/3 octave measurement in my car. 
High passed at 5K 24dB Linkwitz Riley. No EQ yet.










For the price, it's really hard to beat.


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## thehatedguy (May 4, 2007)

Isodynamic is the same as a planar.


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## less (Nov 30, 2006)

Yep - just discovered that... boo! Its a standard ribbon tweeter and I'm really more interested in trying something AMT based. Thanks for all the input guys - decided I'm going to try out the Airborne 4001 from Meniscus... they'll actually be delivered tomorrow since I'm in MI, so I'm anxious to see how they sound. 

If I get crazy later, I may try the AC 2560s, but this is a good way to test the water at a pretty fair price.

Jim aka Less


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## EricP72 (Mar 23, 2008)

Jim where are you going to be installing these at in your car? I'm curious about these and look forward to your opinions on these.


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## fish (Jun 30, 2007)

less said:


> Yep - just discovered that... boo! Its a standard ribbon tweeter and I'm really more interested in trying something AMT based. Thanks for all the input guys - decided I'm going to try out the Airborne 4001 from Meniscus... they'll actually be delivered tomorrow since I'm in MI, so I'm anxious to see how they sound.
> 
> If I get crazy later, I may try the AC 2560s, but this is a good way to test the water at a pretty fair price.
> 
> Jim aka Less



Less,

Please keep us posted on your thoughts on the Airbornes.


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## Ultimateherts (Nov 13, 2006)

Another tweeter kind that should be mentioned here is ELECTROSTATIC.

Tweeter - Wikipedia, the free encyclopedia

I plan on buying a pair of these:

eBay - New & used electronics, cars, apparel, collectibles, sporting goods & more at low prices


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## subwoofery (Nov 9, 2008)

Does anyone know the dispersion patern for the RT20021 or the RT4001? 

Been searching on the net but couldn't find it. I'd like to know if the horizontal axis spreads wider than the vertical one... Planning to use it for my center channel. 

Thanks, 
Kelvin 

PS: found this thread Are you ready to try an Air Motion Transformer Tweeter? - Techtalk Speaker Building, Audio, Video, and Electronics Customer Discussion Forum From Parts-Express.com (if it hasn't been posted yet)


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## thehatedguy (May 4, 2007)

The 20021 should be pretty similar to a small dome. The 4001 AFAIK should be narrower on the long side than the short side.

But then again I read where they act as a point source and have similar horizontal and vertical patterns...but I can't wrap my head around that yet.


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## Ultimateherts (Nov 13, 2006)

O.k. so I just bit the bullet and bought a pair of electrostatics!!! They are Monacor RBT-95SQ electrostatic tweeters. They should sound easy on the ears like ribbons I'm guessing and can be use from 8K on up...

Here is the PDF:

Europe Audio


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## thehatedguy (May 4, 2007)

Those aren't electrostats....those are planars.


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## Ultimateherts (Nov 13, 2006)

thehatedguy said:


> Those aren't electrostats....those are planars.


Hmmm. well you would be the one to know that... Ahh well I got some planars then.

Here's another article I found:

electrostatic and magnetostatic speakers


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## Ultimateherts (Nov 13, 2006)

How about this diy ribbons:

Do It Yourself - Ribbon Speakers - Project: La Folia magnetostatic by Mogens Gallardo


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## subwoofery (Nov 9, 2008)

thehatedguy said:


> The 20021 should be pretty similar to a small dome. The 4001 AFAIK should be narrower on the long side than the short side.
> 
> But then again I read where they act as a point source and have similar horizontal and vertical patterns...but I can't wrap my head around that yet.


Thanks, asking coz I want to find something that has similar dispersion pattern as say a Beyma CP21/F (140°x40°) - for use as a center channel so narrow dispersion up and down but wide... 

Kelvin


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## cvjoint (Mar 10, 2006)

Hmm didn't know the tinny AMTs where at Meniscus as well. Might have to order myself a pair. I want to match them with the Neo10s I'll be testing soon. I can't fit the Scan 3/4" illuminators and the Neo10s in pillars at the same time. 

I have serious doubts about the Airborne's having lower HD than the Scan Speak Illuminators. The Scans are super robust, 120w continuous rating as well. 

Are the 20021 sealed back? How about the depth?

I've been eyeing these as well:









The RT4101's. A pair of these could sound nice next to a line array of mids. I don't have anything against planars. The BGs are fantastic drivers.


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## Ultimateherts (Nov 13, 2006)

cvjoint said:


> Hmm didn't know the tinny AMTs where at Meniscus as well. Might have to order myself a pair. I want to match them with the Neo10s I'll be testing soon. I can't fit the Scan 3/4" illuminators and the Neo10s in pillars at the same time.
> 
> I have serious doubts about the Airborne's having lower HD than the Scan Speak Illuminators. The Scans are super robust, 120w continuous rating as well.
> 
> ...


I saw those too... I guess there are still a lot things to try in a car!

Does anyone know off hand on average how much air space is in an a-pillar?


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## thehatedguy (May 4, 2007)

RT20021s are sealed back.

With the terminals they are 3/4" deep. The tweeter itself is 3/8" deep.

I've attached the FR and distortion measurements somewhere else I think...but I attached them here again.


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## thehatedguy (May 4, 2007)

I didn't have this information back when I first got my RT20021s...and set the xo at 5k, and I think I will be bumping it up to 6k.

I am getting a ringing which could either be the little AMTs trying to play too low or I have the Neo-8Ss crossed too low.

The 4001 is a much more robust tweeter and is good to 2k.


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## cvjoint (Mar 10, 2006)

thehatedguy said:


> RT20021s are sealed back.
> 
> With the terminals they are 3/4" deep. The tweeter itself is 3/8" deep.
> 
> I've attached the FR and distortion measurements somewhere else I think...but I attached them here again.


That is super tinny. I might just buy them. On the other hand if they are sealed that drop in output below 5khz cannot be avoided. I guess a 5khz HP will do.


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## thehatedguy (May 4, 2007)

Yeah I was a bit sad when I saw that FR measurement...

I haven't forgotten that PM George...


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## cvjoint (Mar 10, 2006)

thehatedguy said:


> Yeah I was a bit sad when I saw that FR measurement...
> 
> I haven't forgotten that PM George...


Well it doesn't look anything like the whitesheet. It's supposed to go down flat for a while. 

No worries, I gots patience. 


To answer a previous question a pillar is probably good for 1 liter on average. Mine are 2L but my pillars are unusually wide and I built them out. Some guys like J.W. have massive boxes in the pillar while others just build a baffle and drop the speakers in. Results will vary. With mids in pillars I'm usually first concerned about absorbing the rear wave and therefore depth before overall volume. With low FS mids lots of small pods are possible.


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## fish (Jun 30, 2007)

Ultimateherts said:


> Does anyone know off hand on average how much air space is in an a-pillar?



Are you talking about the airspace between the plastic panel & metal pillar? If so, I measured at around 1.5-1.75 liters (IIRC) inside the plastic panel. That total was without cutting out the plastic grid patterned support ridges. So I'd guess about 2 liters after that. 

I did this back when I wanted to (still do) put those new Neo 8s planars in my Civic pillars. It just seems almost impossible to get those big suckers to aim up away from the dash and/or my lower torso.


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## Ultimateherts (Nov 13, 2006)

fish said:


> Are you talking about the airspace between the plastic panel & metal pillar? If so, I measured at around 1.5-1.75 liters (IIRC) inside the plastic panel. That total was without cutting out the plastic grid patterned support ridges. So I'd guess about 2 liters after that.
> 
> I did this back when I wanted to (still do) put those new Neo 8s planars in my Civic pillars. It just seems almost impossible to get those big suckers to aim up away from the dash and/or my lower torso.


Cool I was thinking it was near that...


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## Patrick Bateman (Sep 11, 2006)

less said:


> Sweet... appreciate the info on these. Pretty much just what I was looking for... and AMT that might even fit my current pods. I don't really have a need to change back to two way, so a small size won't be an issue in running 4-5k+ at 12-48db/oct.
> 
> If the radiating pattern is the same as what I've seen on other AMTs, its about 30 degrees by 120 degrees. That makes it the matter of aligning so the sweet spot spreads across the appropriate space in the car pretty important. Actually, it may be advantageous to not have wide dispersion on all angles, with all the reflective angles in a car.


You can build a waveguide for a ribbon in literally an hour.
My table saw died, and I managed to make a waveguide in under an hour with *hand tools*.

It's super super easy.

Rectangular ribbons have a funky wavefront, due to one dimension being larger than the other. The large size of the radiator increases power handling, but at the expense of the wavefront shape.

The combination of a symmetrical (ie square) ribbon, plus a waveguide, gives you the increased power handling plus a wavefront that's a good match for your midrange.

It's your basic "win win"










If you have a Guitar Center nearby, go listen to Behringer's waveguide-loaded ribbons.


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## Patrick Bateman (Sep 11, 2006)

Ultimateherts said:


> How about this diy ribbons:
> 
> Do It Yourself - Ribbon Speakers - Project: La Folia magnetostatic by Mogens Gallardo


Back in the 90s a good riboon like the Ravens would set you back $500

Nowadays you can get something comparable for $100

It's just a repeat of what happened with TVs. I paid $300 for my 25" TV in 1995, and now I can get a 42" flat screen for not much more.

The globalization of manufacturing has really removed a lot of the incentives to build your own drivers, unless you absolutely need some incredibly strange set of parameters that just isn't available commercially.

Bohlender Graebner was actually one of the first to jump on the bandwagon. IIRC, their ribbons used to sell for about $500-$1000, until they came out with the NEO3, which was their first product that was made offshore.


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## rugdnit (Dec 24, 2007)

cvjoint said:


> Hmm didn't know the tinny AMTs where at Meniscus as well. Might have to order myself a pair. I want to match them with the Neo10s I'll be testing soon. I can't fit the Scan 3/4" illuminators and the Neo10s in pillars at the same time.
> 
> I have serious doubts about the Airborne's having lower HD than the Scan Speak Illuminators. The Scans are super robust, 120w continuous rating as well.
> 
> ...


Those neo10's look promising. I have been looking at fitment since I have large a-pillars. I am looking forward to your review of these.


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## cvjoint (Mar 10, 2006)

rugdnit said:


> Those neo10's look promising. I have been looking at fitment since I have large a-pillars. I am looking forward to your review of these.


Yeah, the nice part about BGs is that you get the benefits of planar technology, crisp and smooth sound without any of the frailties advanced technology usually comes with. Can't wait to get my hands on a pair.

Until then you should check out the Hobby HiFi 1/2008 edition. It's on BGs site under pro20d reviews. Short story is that it's a very clean single mid solution. At 90db it's mostly under .1% thd, and under 1% from 50hz! up. It's a nutty driver.

BG says there is less phase distortion in this type of driver because the radiating surface is flat and driven uniformly. In nearfield this might be a worthy addition.


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## less (Nov 30, 2006)

Sorry its been so long with no updates, but I'm mid build in a new set of enclosures for my scan 12ms and the RT4001s. From just a brief listen I was convinced that I'm interested enough in these to try and build something to truly integrate these into my system. I'm working on a set of MDF pods, roughly 1.5 liters plus Scan AP vents & stuffing to approximate a 2 liter total volume. Making mock-ups which resulted in a fairly good fit space for oval enclosures roughly 11" x 6" x 3.5" - and its taking more time than I'd hoped. At least I'll finally hear my scans in a box that was really made for them...

The confusion between planar, ribbon, electrostatic and Heil drivers is pretty understandable - heck, the pleated look of one planar diaphragm had me talking about a planar driver like it was a AMT or AST driver, Still though, ribbons have been around for years, but only recently have we seen any improvements from heil's 1960s technology. Hopefully we can stay focused on this technology here, although explanations of differences and benefits comparisons between the formats are certainly useful too. 

AMT - Heil - AST drivers are currently made by: Hygea Electric (sp?) and possibly others, and are distributed by: Airborne (Solen's house brand), Beyma, Mundorf, Aurum Cantus and FAL, that I know of. Prices range from $48 each to over $1000 each. These drivers actually work by squeezing air between layers of a single pleated diaphragm and are naturally bi-polar, although the backs are often covered. This technique tends to generate a wide but not tall sound field, since the sound eminates between the pleats, so the sound waves are generated primarily along the horizontal axis. The benefits seem to be: improved improved transients, minimized phase issues, minimized distortion related to overshoot (where the traditional drivers suspension fails to prevent over excursion and its opposite due to inertia), as well as a fairly flat impedence curve across its range. It's weaknesses seem to be in getting this design to reproduce a wide range of frequencies with the same output levels. At least this is my understanding. They have an open and exceptionally relaxed sound that is quite natural - to my ears.

Its great to see companies toying with this unique reproduction technique and applying new materials and improved design techniques to yield what appear to be far better results than the original heils in some cases. Their benefits may outweigh their disadvantaves in the car environment where we often use processors to tweek FR issues and where wide dispersion on all axis' may actually be of detriment due to multiple hard reflective surfaces... well at least, that's why I decided to give them a try.

I'll post more when I get the enclosures complete and get retuned, but it might be a while. In the meantime, thanks for all the input and discussion... 

Jim


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## Se7en (Mar 28, 2007)

Great post! Thanks for the update!


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## thehatedguy (May 4, 2007)

I had a feeling that Hygeia made those other speakers. Unfortunately the big Hygeia/Airborne only goes down to 3k...whereas the big Beyma and AC can make it down to 1k.


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## cvjoint (Mar 10, 2006)

Jim,

Those are certainly some of the benefits of new technology manufacturers have been pushing. My question is, where is the proof? Unless we are talking about a large BG planar, most advanced technology are tweeter competitors. We should be comparing them to domes. 

A high quality 3/4" dome does a fine job with transients, HD, FR etc. I can't think of a test where the domes can't keep up. Browsing through Zaph's CSD tests it seems small domes have a decay better than or equal to the planar, ribons etc. The one AMT he tested did really poorly. In Linkwitz's tests the neo3 cringed under power and also took a very long time to decay. That's something you can see in the Hobby HiFi mag review as well.

How do you know the special sound is not distortion, or dispersion control?


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## thehatedguy (May 4, 2007)

The 4001 had excellent dispersion in both directions and has pretty good distortion measurements.


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## cvjoint (Mar 10, 2006)

thehatedguy said:


> The 4001 had excellent dispersion in both directions and has pretty good distortion measurements.


Is the dispersion as good and uniform as a 3/4 dome? can you cross it at 2.5khz like some top end domes? There is also the issue of output, the Illuminator for example is rated at 120w with a 6 db crest factor for hours and hours with a 3khz HP. All we know is that it can match a dome in nonlinear distortion at low output and with a high crossover point. It's a great achievement for an AMT, but not in general. It is merely catching up. 

The RAAls for example have been praised. Their THD sheets are at 85db or something if I remember. Almost any dome can match that performance.


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## thehatedguy (May 4, 2007)

I've posted somewhere on here the data for the 4001 (or I thought I had).

Link:

Are you ready to try an Air Motion Transformer Tweeter? - Techtalk Speaker Building, Audio, Video, and Electronics Customer Discussion Forum From Parts-Express.com


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## ErinH (Feb 14, 2007)

The RAAL has a very interesting response. Makes me wonder if it was designed around sound power. 

I agree with George, though, the HD testing levels is not stressful at best.


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## thehatedguy (May 4, 2007)

I've only seen a few tests of the RAALs...aside from the price, the depth keeps me from looking at them further.

I have heard they are pretty special sounding speakers...and this is from a semi-local guy who has a pair in a home setup.


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## cvjoint (Mar 10, 2006)

OK, let's put the AMT and Vifa NE19VTS head to head:

Beaming, db down at 20khz 30 degrees off axis:
AMT: 8db Vertical 10db Horizontal
Vifa: 5db in both directions

So not only does the Vifa maintain a symmetric dispersion pattern it beams up to 50% less. 

HD @ 2khz, 2nd-5th harmonic db down:
AMT:
-40
-55
-65
-65
Vifa
-40
-50
-70
-70

So it is about equal. But look what happens at 1.25khz. Clearly the AMT hits the brakes. 

So the AMT only keeps up with HD 2khz and above, which is pretty good for most applications. But what happens when the knob goes past 90db? Which one will keep their cool better? The Vifa is rated at 4 times more power. 

This AMT is also bigger with or without faceplate and costs 3x more than the Vifa. It's not clear that the decay would be better either, the link you posted says the diaphragm is equal to 1" tweeter

I'd say the dome wins this one. The AMT barely ties in one small power test but fails everywhere else imo.


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## thehatedguy (May 4, 2007)

It says the folded diaphram is roughly equal to a 1" dome. It has MUCH more surface area than a 1" dome.

The decay on the AMTs are much better than any dome I have seen...or nearly any dome.


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## cvjoint (Mar 10, 2006)

thehatedguy said:


> It says the folded diaphram is roughly equal to a 1" dome. It has MUCH more surface area than a 1" dome.
> 
> The decay on the AMTs are much better than any dome I have seen...or nearly any dome.


AMT:








3/4" dome:









New tech speakers have a diaphragm that is secured at two ends or more. As it gets excited the energy that is stored needs to be dissipated. It may go towards the clamping point but that is rigid and it will get rerouted back into the diaphragm where it will get dissipated over a long time period as the diaphragm settles. In a dome or cone some of the energy can be damped by the surround and spider. My theory is that they decay slower, and it's backed up by the larger diaphragm and the CSDs above.


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## thehatedguy (May 4, 2007)

That's a pretty junky AMT to compare it to too.


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## thehatedguy (May 4, 2007)

Hobby HiFi in Germany has tested a couple of the Aurum Cantus/Harwood Acoustics AMTs...and they are MUCH MUCH better than that M&D turd.


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## ErinH (Feb 14, 2007)

thehatedguy said:


> That's a pretty junky AMT to compare it to too.


That thing measures like crap. Probably the single worst FR I've ever seen. So glad I saw the measurements before I bought it.


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## cvjoint (Mar 10, 2006)

thehatedguy said:


> Hobby HiFi in Germany has tested a couple of the Aurum Cantus/Harwood Acoustics AMTs...and they are MUCH MUCH better than that M&D turd.


The CSDs are computed differently. There is only a 20db change on the axis in Hobby HiFi. Everything looks better in that mag. The Neo3 is almost identical to the AMT and it tests close to a 1" dome. So yes it tests better than the AMT I posted but not necessarily better than a 3/4" dome. It's also 20db down at 20khz.


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## cvjoint (Mar 10, 2006)

Hobby HiFi 01/2011 has the Scan Speak 3/4" as well as the Vifa 3/4" and many other popular tweeters. 

Comparing these results with the AMT the domes look marginally better. It seem that at .4ms the output has been reduced more, as well as at .5. 

The AM25 does look pretty good overall. It's a good alternative to domes for someone that doesn't mind unusual dispersion and has the room for them.


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## less (Nov 30, 2006)

Ahhh, we've broken out the charts and graphs! I got fooled into thinking that ever diminishing THD figures were the key to great sound in the 70s (along with most of the generation who bought amps based on the little published information available) and when I finally heard a cd with varying levels of thd included for audible comparisons I realized just what a joke that was. Since then, I don't get quite so excited about the stats, and frankly (just like those who own tube amps and love their sound), I'd be happy with a tweeter that I liked the sound of - even if it WERE distortion =)

I've still had nowhere near enough listening time with these to talk in details about them, but I can say that I've owned a LOT of great domes and some not-so-great ones too: Air Circs, Hiquphons, Illuminators, several ADS models, Focal, Rainbow (SEAS), Zapcos (pretty nice up high), etc. While I understand the desire to quanitfy and make statements more meaningful than just subjective observations, all I can say is that these have a distinctive sound compared to the domes that I like. Where you measure distortion and want info about higher output levels, I can say that I was surprised at the resolution and lack of compression at higher output levels with these tweeters. They sounded very relaxed and articulate when pushed (far different than most domes) - although I only had them crossed at 12db/5khz. Still, that's a good place to cross if using a broadband mid. 

The 4001s are rated to cross at 2khz also and I suspect you could go lower if you went to 48db slopes, but that remains to be seen. The original Heils were sometimes crossed at 800 but more often 1200, but to achieve that they used a great deal of space.

I really don't want to overstate anything here, because I've really not listened long enough, but I've been working on new enclosures for the past 2ish weeks ever since buying them and that short listening time... so I obviously thought they were worth an extended listen. The fact that several high end vendors think they're good enough to sell for $250- $1000 and that they're being included in some extremely expensive and respected lines also confirms that others must like something about the concept. What's nice is that this type of tweeter has seen far less attempts to refine and perfect tha either domes or ribbons, so it'll be interesting to see if even more bugs can be worked outof them. Incidentally, the Heil version were often crossed at 800hz but seemed to work better up around 1200 in most installations... granted they were huge, but who knows what might be possible with further developments. 

Hoping to mount my new enclosure by next week (but toying with making the front baffle removable which will add some time to the works), but then it'll be back to the drawing board for tuning... so it'll be a while before I really have a feel. Still, it's nice to be energized about the system again. 

Less


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## less (Nov 30, 2006)

Here are some test results from the Harwood model AM30... nicely efficient and pretty flat to boot... costly though at 386 euros. The appearance of the baffle covering the driver membrane is remarkably similar to the Airborne models too.


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## thehatedguy (May 4, 2007)

The Harwoods are the same as the Aurum Cantus...which are made by you know.

The thing about the AMTs versus a dome is you have SO much more radiating area. Which is going to have lower distortion a 15 or an 8 playing the same music at the same level? Same with a tweeter playing treble.


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## thehatedguy (May 4, 2007)

The Harwoods are the same as the Aurum Cantus...which are made by you know.

The thing about the AMTs versus a dome is you have SO much more radiating area. Which is going to have lower distortion a 15 or an 8 playing the same music at the same level? Same with a tweeter playing treble.


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## cvjoint (Mar 10, 2006)

Less, you may be asking one measurement to do too much. Imo, to really ditch the objective way you first have to break sound into all it's components, frequency, output, time arrival, duration. Then you must have a test for each of the components in all dimensions. None of the tests independently will do the trick. The approach is correct, but the execution often lacks or it's incomplete. 

I think I would be a much bigger fan of the AMTs in HT where there is room to overcome the size of these things and their odd dispersion by lining them up to the ceiling. In the mobile environment space is precious. Standard tech drivers like domes and cones give a lot per square inch and that's going to be tough to beat.


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## less (Nov 30, 2006)

Apparently, they've made major improvements in dispression recently, and my assumption that AMT designs would all have a wide but not tall dispersion patter was simply wrong! Take a look at the charts below showing pretty nice dispersion over both axis' 

As for size, the RT4001 is only 3.4" around and 1" deep, which barely qualifies it as a "large format" tweeter. If size is an issue (especially if you're considering the 10"x5" Neo10 mid), you could always use the RT20021, which is just plain tiny and still plays to 3k. 

Anyone really interested in the RT4001 should really take a minute to read through the article thehatedguy linked - it has both plots and commentary worth checking out. I've imported some of it below, along with the PDF and a link to buy the driver for just $75ish. 

*Article Link*

*Buy it from Meniscus - Airborne RT4001 * - *PDF from manufacturer*

*Image:*









*Vertical dispersion*









*Horizontal dispersion*









Good point on the measurements - I would like one chart that could tell me how the driver sounds, but that isn't realistic. Todays driver data is far more useful and valid than those that gave me my bias. The problem is that our hobby is based around an experience that is extremely hard to describe and compare in any meaningful way except by using charts and graphs, and yet measurements mostly capture individual aspects of a drivers performance - in a single environment - at a fixed point in time. Sadly though, car drivers operate in a dynamic world, full of variables. 

I only emphasize listening to as many drivers as possible as the primary method of evaluation because there are so many things measurements can't tell you. I've owned great testing drivers that couldn't resolve certain instruments clearly, and many others that simply lost composure at higher output levels, leaving me exceptionally disappointed! I've had other drivers that had a nature to their sound that I vastly preferred to similarly measuring competitors... and who know's why?! Also, like some people like brocholli and others hate it, we all have our own preferences in sound. These facts make it terribly difficult to predict from statistics just which option will best satisfy our needs. 

Anyhow, that probably explains why I've learned to trust my ears and why I've used nearly 40 drivers in my current installation. It may not be practical, but a person can go to a couple competitions and hear most of the more accepted high end gear long enough to get a feel for their capabilities. 

In the end what really matters is how well we like what we hear when we turn on our systems and how much fun we had getting there. 

Less


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## less (Nov 30, 2006)

I really should have read the prior posts lol. 

On dispersion, I'm really not convinced that wide dispersion is always beneficial in the car. Reading various posts here and seeing discussions on: 1. wave guides, 2. single tweeter installations, 3. people troubled by reflections off windshields & other glass, makes me wonder. From what I read, reflections can result in: loss of ability to create an ideal stage height and width, unfocused image and potential ear fatigue. And yet we know from listening to decent headphones that minimal reflections don't preclude great sound. 

So as long as we can design enclosures that allow drivers to operate within a more limited dispersion pattern, we may actually benefit from drivers with more limited dispersion. We don't move around a lot while driving, and most of us do our critical listening alone, so its easy to define where we need the sweetspot to be. Wide dispersion was probably something sought after in the home environment where we'd wander throughout the room, and conventional wisdom that it was a favorable effect may be carried over to our in car philosphies... without much thought. But, I'm just tossing around ideas... I'd love to hear someone truly qualified or experienced share some more informed info on this topic. 

CV, for what its worth, I found my scan illums also measured around 10db once installed in my car and measured from my listening position... and they're supposed to have great dispersion. (At my age, I doubt I'd hear the difference though lol).


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## Patrick Bateman (Sep 11, 2006)

less said:


> I really should have read the prior posts lol.
> 
> On dispersion, I'm really not convinced that wide dispersion is always beneficial in the car. Reading various posts here and seeing discussions on: 1. wave guides, 2. single tweeter installations, 3. people troubled by reflections off windshields & other glass, makes me wonder. From what I read, reflections can result in: loss of ability to create an ideal stage height and width, unfocused image and potential ear fatigue. And yet we know from listening to decent headphones that minimal reflections don't preclude great sound.
> 
> ...


Keep an eye on my new HLCD thread

The beamwidth on these horns will be quite narrow

basically I'll keep the 'width' of the stage narrow via the horn, and then I'll 'add' the width back in with ambiophonic processing

This has worked nicely at my home - my speakers are literally touching each other, they're THAT close

Without the processing on the soundstage is no wider than the speakers, but you turn on the ambio and it's nearly 180 degrees

One of these days I need to try a quad ambio

I don't want to turn this into a thread on ambio, but it definitely requires speakers that are much more directional than what you'd use for a conventional stereo triangle. A side benefit is that the center image is rock solid, which is nice since 90% of the music out there is mostly mono


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## thehatedguy (May 4, 2007)

"Patrick" you not accepting new members to your forum?


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## Patrick Bateman (Sep 11, 2006)

thehatedguy said:


> "Patrick" you not accepting new members to your forum?


Oh, let me check -

90% of the member requests come from spam bots that want to post their dreck, so it's easy to miss legitimate requests


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## subwoofery (Nov 9, 2008)

Patrick Bateman said:


> Oh, let me check -
> 
> 90% of the member requests come from spam bots that want to post their dreck, so it's easy to miss legitimate requests


Don't accept this guy... He's _hated_ everywhere else  lol 

Kelvin


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## thehatedguy (May 4, 2007)

Well, it's under my real name...people everywhere don't hate that name...lol. Or do they?


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## less (Nov 30, 2006)

Well, apparently a company called Elac builds their own versions of the Heil driver too - and its the version used in both the Burmester and their own really interesting designs. Check out the creative design of their "coax" incorporating a AMT tweeter positioned in the middle about half way down this page... many great shots of the driver in various states of assembly. 

Given the awards they've won abroad and their unique designs, I'd enjoy hearing a set of these - just because! The 360 degree tweeter at the top of the page is also interesting.


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## thehatedguy (May 4, 2007)

I was wondering when someone would use that crystal cone...saw the patent info in Voice Coil last year or the year before. Looks very cool.

Been thinking about coax mounting an AMT too...but you would need a speaker with a 3" voice coil. Maybe take a dust cap off of a Morel, Dyn, or a Hi-Vi clone and put a RT4001 down in the cone/voice coil apex.

Or you could look up the JBL Control 60 series, buy the big waveguide for the 6s and put one in the center where the softdome tweeter goes. Going to check prices on those waveguides this afternoon.

Damn...I might need to look into that some more.


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## thehatedguy (May 4, 2007)

Oh, FWIW the omni tweeter you mention is a Hygeia made speaker...it's on their webpage under aluminum ribbon tweeter.

ºñ¼Íµç×ÓÓÐÏÞ¹«Ë¾

Well if Hygeia doesn't make it...they do make one...lol.


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## cvjoint (Mar 10, 2006)

I like the 360 ribbon, it makes sense. Unlike say the coax, which imo is very questionable. If you care about dispersion and diffraction you are much better off with a small dome in there. Not to mention you would double the output and lower distortion significantly by allowing for a larger cone on the woofer.


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## less (Nov 30, 2006)

Lol - I didn't say it was the soundest design theory, just that it was interesting. I bet they image very nicely, especially if you could mount them in a small spherical enclosure. I like seeing companies that have the guts to try new things... like Magico's nano-tube drivers, oddball cabinets, etc.. With all the advancements elsewhere in life, music lovers haven't seen that much improvement in the old dome designs since around the time ADS came out with their magnificent tweeters in the mid 1970s!

Golden Ears (from the people who brought us Def Tech and other respected brands) Innovations Design and Engineering Award in the High-Performance Audio category for its Triton™ Two tower speaker. Although its possible these are like reviews are at times and more likely to go to the best advertiser. Still, they're trendy at the top for the time being and I wish I had stock in Hygeia... I think its a winner. 

I wonder what technology we'll see in speakers (if we don't have neural implants or the likes) 20 years from now. At the rate I'm going, I may not finish my cabinets until then though lol. I got them half way done, then decided I'd toy with the idea of trying to make the cabinets as close to spherical as I could, inside to reduce standing waves and outside to deal with diffraction... a few days of tinkering told me that I should have thought of that before I'd gone as far as I have. Might tinker with new cabinets this spring (removable baffle versions this time) to try that, for now I'm settling for hand rounding (they're oval already). Today I decided to put lead in the baffles and to brace them too - even though they're only holding scan 12m's and the Airborne 4001. I'm also toying with making a back cap for the tweeters to better contain any stray rear radiation from the metal covering. Since they're essentially covered dipoles, I wonder if there's benefit to tinkering (larger) alternate rear backs for them. Anything else I might try to make these as nice as possible?

Off topic a bit, but I'm enjoying this speaker building/research so much I'm half tempted to create a little MW - T - MW for my little Denon HT in a box system.... they crossover high enough I might be able to go with BG neo10/3 sort of thing - or maybe try a set of Zaphs little 5" aluminum cone midwoofers. The Audessy (sp?) circuitry in this system would get my prize for best audio invention of the decade... so nice to hear everything even at low listening levles! They came with an ok little set of hideaway speakers, but now I'm wondering just how nice they might sound with good drivers... after all, they have DOME tweeters :toilet: :wacko:  (J/K!!!!). 

Jason (right?), can you get the Hygeia Diaphragm page to open?


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## thehatedguy (May 4, 2007)

http://vtcproaudio.com/images/products/lg_ff1_nogrille.jpg

I swear I've seen those drivers somewhere before...lol.


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## thehatedguy (May 4, 2007)

Yeah I can get it to open...ºñ¼Íµç×ÓÓÐÏÞ¹«Ë¾


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## cvjoint (Mar 10, 2006)

You might want a WMTMW design instead. I've been thinking about the ideal approach for home theater. I would honestly just do a 360 degree line array from floor to ceiling. The budget would decide how good the speakers used can be. Anywhere from closouts and junk yard speakers to Scans. HT fans throw so much money on drivers that are just marginally better and sometimes not even that. It's much easier to get increased performance with more drivers. In a car space is prohibited, and quality matters more.


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## less (Nov 30, 2006)

Hoping to listen to these by early next week! Then its on to tuning (boo! I hate tuning but its a necessary evil). Had a couple snafus... should've never gone with an oak panel in the back for the terminals. Next time, I'll do a couple things different, but these aren't looking too bad.

An array setup would be interesting indeed, but even though I bought a HT system - its only a 2.1 and I really bought it for music. It already sounds pretty amazing, considering I paid $400 and its an all-in-one solution product. I'm more interested in something using drivers that intrigue me, and just that odd kind of person who'd never get excited enough to build a line array unless I was using drivers that were really good. I'd rather make a nicer two way or just save until I could get something more to my taste.

Thanks for the input.
Jim


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## less (Nov 30, 2006)

Figured I'd share the nearly finished pic's. Doesn't it figure that the day I'm about to complete these, my good buddy offers me a pair of the Bowers and Wilkins tweeters from a set of 802s - which mount in a small pod on a stalk and seem perfect to attach to a small car-based cabinet! I was thinking about building a set of cabinets almost identical to these for a set of neo10s, so now I'll have something to pair with them... 

They aren't completely installed yet, but I am already pleased with the change in the midrange qualities. The dispersion on the tweeters doesn't seem to be an issue either with decent high end throughout the cabin. I'll know more once I get them dialed in a bit. I've been wanting to hear the 12ms in the perfect cabinet, so getting these tweeters gave me the excuse to start this project =) The only thing I'd have liked to have done is to round literally every side of the cabinet, but I didn't think to do this until I had the ovals already cut and decided not to start over from scratch... 

Design features:


Rounded cabinet - inside and out to help minimize defraction and standing wave issues
Leaded 3/4 baffle which weigh over 2lbs each to minimize cabinet vibration/noise
Recessed drivers (which sucks to do without a router jig!) for various reported benefits
Chamfered midrange mount to allow adequate airflow and minimize resistance
Damped and AP ported to simulate ideal cabinet volume with minimal actual space usage

*Completed front* - grills held by neo magnets and posts







*Nearly complete rear* - I tried to paint flat black, but contact cement from carpeted area wouldn't allow a smooth finish - so I"ll be carpetting the rest too









*Thumbs of some of the steps along the way*








-







-







-  

More when I've had the chance to dial them in a little. There's something really nice about these, but there was also something really nice about the Scan Air Circs too - birds of different feathers though and different prices too!


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## mitchyz250f (May 14, 2005)

Keep us updated on the progress.


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## less (Nov 30, 2006)

I hate tuning! There, I said it =) I've been toying with this stuff since I was 9 and even wanted to be an audio engineer "when I grew up", but I'm glad I didn't go that route because its just frustrating to me. It'd be awfully nice to have a friend around here that had the knack that I could learn from too... Getting in the ballpark is always easy enough, but getting it just right seems awfully ellusive. 

Just for giggles, I may just throw my little home system in the car to see what it sounds like. I could save a fortune by buying another one identical to it and installing it - and it'd take up less space. All I'd need is a good power converter and my Pure I20 source...

Anyhow, it'll probably be tuned in a month or two =)


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## Patrick Bateman (Sep 11, 2006)

Do you have a woofer tester, or some method of measuring impedance?

If so, could you post an impedance plot of the woofer?

The reason that I ask is because that variovent might not work the way you'd expect it to work, due to it's size.

Basically a variovent is supposed to reduce the magnitude of the woofer's impedance peak in a sealed box. But usually the variovent's size is a fraction of the woofers. Due to that, it may be radiating more output than you want.

Basically turning the box into a lossy dipole.

there's some good info on how to tune these things here:

Variovent placement... - diyAudio


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## The Baron Groog (Mar 15, 2010)

thehatedguy said:


> I was wondering when someone would use that crystal cone...saw the patent info in Voice Coil last year or the year before. Looks very cool.


Lanzar had it on their old HR comps, albeit with a conventional dustcap: Lanzar - HR6.1 - Heritage 6.5'' Two-Way Custom Component Speaker System

Pioneer and Kenwood have used similar 3D cone shapes with their "blade" comps (Old blue coned TS-E range) and Kenwood with their "tornado" cones on subs.

The ELAC X-JET does look like an interesting driver-great dispersion patern.

Not quite the Heil tweeter, but have you seen what HK are putting in the new BMW X1? A 1 x 80 mm x 200 mm EDPL midrange tweeter for the centre channel, hover over the driver description to see an image, interesting shapped wave guide on the top of it: http://www.bmw.harmankardon.com/en/vehicles/model01/technical.aspx#detail


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## thehatedguy (May 4, 2007)

That old Lanzar set isn't the same thing...it's just a poly cone with some crystal looking molding.


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## ErinH (Feb 14, 2007)

Patrick Bateman said:


> Do you have a woofer tester, or some method of measuring impedance?
> 
> If so, could you post an impedance plot of the woofer?
> 
> ...



Agreed. When you add a variovent type resistor membrane you should always tune it and at least run a couple impedance sweeps to see if its doing what it should be (taming the high Q resonance). Tossing one in there just because is like throwing darts blindfolded. 




Sent from my iPhone. Pardon the grammar.


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## The Baron Groog (Mar 15, 2010)

thehatedguy said:


> That old Lanzar set isn't the same thing...it's just a poly cone with some crystal looking molding.


Have you got a link to the patent?


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## less (Nov 30, 2006)

Patrick, thanks for your useful information and the link. 

Here are a few points:


Scanspeak says the aperiodic vent I'm using adds UP TO 20% to cabinet volume. Yes, its probably designed more for drivers that move more air, but that isn't for sure and just in case, I built compensation for that into my design.
Standard acoustical stuffing in sufficient quantity/density can result in simulating an additional 20% to cabinet volume
Scan 12m's work well in a 2 liter cabinet - but that size won't easily fit in my kick panel area. 
I want to use my Scan 12m drivers between roughly 250 and 2-3khz and have had troubles with them when crossed below 300hz in past enclosures (including a variation of a design that won several national competitions). Their impedence hump is almost completely gone at 250hz.


My enclosures were built at just under 1.5 liters which is as large as I could make them to fit the space well (without resorting to fiberglass and its associated problems... not the ideal enclosure material by a long shot imho). I then added an amount of acoustical stuffing approximated to add roughly 5% to the volume that the drivers would "see." That allows the Scanspeak Flow Resistor to be off in it's calculated effect to be off as much as 50% (up to 30% increased volume) before I'd go over the goal of 2 liters. 

Hardly "throwing darts in the dark," I've allowed for two assumptions: 1. Scanspeaks stated performance (and they're known to meet or exceed stated measurements in independent testing) and 2. a 50% margin for error due to the POSSIBILITY that the product would work differently with the driver I'm using. If I find issues when I measure it - I'll tinker with my processor, or just stuff the box more and seal it and call it close enough. In the worst case scenario, I'll go back up to my old xover point of 350... no big woop!

Erin, seriously, you should ask yourself what you had to contribute with that post. Your point wasn't new and the post contained no useful information whatsoever. I used to appreciate your input, but lately I've grown tired or your negativity and condescending attitude in many threads I've started. I've asked before and I'll ask again that you please try to either contribute in a positive manner, ask a honest question or simply refrain from pushing the "reply" button. With 12,000+ posts, surely thats hard for you... but would you give it a shot?


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## Complacent_One (Jul 2, 2009)

Maybe I should do some subjective tests...my neighbor has some 14 or 16 sets of ESS Speakers..AMT-1s, 3s, CE1s...not sure of the total count, but craziness, nonetheless. Lots of AMTs to choose from...may be quite fun...


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## ErinH (Feb 14, 2007)

less said:


> Erin, seriously, you should ask yourself what you had to contribute with that post. Your point wasn't new and the post contained no useful information whatsoever. I used to appreciate your input, but lately I've grown tired or your negativity and condescending attitude in many threads I've started. I've asked before and I'll ask again that you please try to either contribute in a positive manner, ask a honest question or simply refrain from pushing the "reply" button. With 12,000+ posts, surely thats hard for you... but would you give it a shot?


There's hardly any post here with new information. Let's be real.

I'm sorry you don't like my brief posts. Sometimes a few sentences is all I'm able to provide but it does the job to get the point across. I don't always have time to sit and write a diatribe and explain my posts. But, FWIW, the part about "throwing darts" wasn't intended to be aimed at you (no pun intended, lol). I know your history and I assumed you did due diligence. It was a statement for those who see your build and think "oh, cool, that'll solve my problems". As seen in your last post, it appears you weren't aware of that and I can understand why you might be so defensive toward my reply. But, again, it wasn't aimed at you because I figured you knew it already; it was aimed at the onlookers.
Fact is, AP membranes should be tuned to provide the necessary damping to lower the Q. Since, after all, an ap enclosure is made to counter the high Q resonance a small enclosure brings to the table (at a loss of sensitivity, mind you). So, again, the statement was a general one; a word of caution that you can't just toss it in there. Well... you can... but you've not done due diligence.

As patrick mentioned and as I supplemented, a way to measure impedance at or around Q is needed in order to get the most out of the enclosure. This can be done via a woofer tester, a jjg and aRTA (I've provided a link to this jig and aRTA's tutorial numerous times on this site) or even the old school test tones + DMM method (which SUCKS).
I've posted my thoughts on the various methods in a fair amount of threads regarding AP enclosures and would be happy to chat with you on the phone regarding my trials and tribulations. One tradeoff I've found is that while you may lower Q, you might also introduce 2nd and 3rd order resonances. These are measurable and are part of the balancing act. 


speaking of condescending...



Less said:


> With 12,000+ posts, surely thats hard for you... but would you give it a shot?


Most of those posts are comprised (at least, within the last couple years) of data and analysis. Data I bust my ass to provide to the community. I know you've said you don't really pay much attention but it's not something to scoff at. I'm sorry you misinterpret my large post count as a means of post whoring. I think if you look back in my previous week's postings, you'll find no less than 6 different driver tests consisting of Dyn, Audio Technology, CSS, Scanspeak and Massive. That's what I spend most of my time doing here... not just posting to post. 


Offers on the table to chat on the phone if you'd like. The internet isn't the easiest place to come across as intended but I try to make my posts clear and to the point when possible and it sometimes happens that the intent is misinterpreted via type.

- Erin


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## cvjoint (Mar 10, 2006)

While we're on it, how low of a Qtc can you achieve with an AP membrane? Is it 0 now Erin?


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## ErinH (Feb 14, 2007)

Keep talkin....




Sent from my iPhone. Pardon the grammar.


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## less (Nov 30, 2006)

Gah.... not going to do it. Just leaving it sit, but there's a whole lot of rationalizing going on here and not so much truth. Oh well, they sound good =) So who cares.


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## less (Nov 30, 2006)

Thought you might be interested in this... not because it really says anything other than that I spend a couple hours fiddling with my system today. The best part was that I used my ipod as the source though my Pure I20 converter and after cruising and listing for a hour today I discovered that...

(wait for it)


I had it's EQ set on Reduce Treble during the entire process!

I'll be REALLY happy when my other Ipod is up and running again so I can keep my audio book one completely separate!:laugh:


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## Patrick Bateman (Sep 11, 2006)

While reading the Danley paraline patent, I accidentally figured out the maths for the Sausalito Audio Works lens.

The SAW lens appears to be a real "no brainer" for ribbons in the car. If I understand it right, it can take a wave and bend it 90 degrees. And not only can it do this, it actually makes the wave *more* coherent, not less.

You guys see where I'm going with this...

You can put ribbons up on the dash, facing UP, then bend the wave 90 degrees.

The lens takes the wave and focuses it into a 'disc' of sound, so that you don't get as many reflections off of the floor and the ceiling.

I'll concede that the SAW lens is better suited for compression drivers; but making one for a ribbon is just incredibly easy. This is because the ribbon doesn't radiate to the top and the bottom like a dome does.










Here's an idea of what I mean. The thread is called "sunshine"


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## less (Nov 30, 2006)

Hey Patrick,

I think your link didn't come through. Unless it wasn't a link and was a thread title in the hlcd category?

If I see this right, and I may not, the SAW lens is the curved blue line and the driver is the cylinder shaped object apparently facing up? The result is 20 degrees of coverage in the vertical plane and a far wider coverage horizontally? In effect it even further limits the already restricted output dimension of the ribbon driver but allows you to aim the resulting wave directly into the main listening area... so you don't have as much reflected sound to mess with the image and stage. I've been curious about how something like this would sound, but there's a fairly large group of people that seem to think that there is something valuable in having ever wider dispersion from high end drivers. 

In the home environment, we've seen successful approachs that vary from designs using reflected sound to their advantage like: dipole electrostats and Bose 901s (yeah, I like their sound) amd others with more minimized reflected output like point source approaches by Gallo (etc.) and even the sub/sat approach to an extent. But the car is an environment that isn't nearly as friendly to reflections... so it seems like restricting directivity could be advantageous - but I've yet to hear an example of that approach in action.


I'd be a little concerned about how to get the design turned into reality without custom milling machines and cad software to yield consistant and reliable curves, and also about what sort of material one should make a lens from - but I suppose things like that are in the thread. Interesting though! I did see a variation on a theme you mentioned earlier in action though recently. The newer Jaguars (IIRC) use a bass driver in the trunks which fed an extended steel tube the vents into the passenger cabin near the midbass.... can't remember who's design it was though.

Thanks for the info...


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## Patrick Bateman (Sep 11, 2006)

less said:


> I'd be a little concerned about how to get the design turned into reality without custom milling machines and cad software to yield consistant and reliable curves, and also about what sort of material one should make a lens from - but I suppose things like that are in the thread. Interesting though! I did see a variation on a theme you mentioned earlier in action though recently. The newer Jaguars (IIRC) use a bass driver in the trunks which fed an extended steel tube the vents into the passenger cabin near the midbass.... can't remember who's design it was though.
> 
> Thanks for the info...


Actually that's the reason that planars are such a good candidate. A dome tweeter radiates in every direction - on a flat baffle it radiates a full 180 degrees, and on a sphere it radiates nearly 360 degrees.

But planars are different - due to the fact that the diaphragm is flat, you can create one of these SAW reflectors in about five minutes. They're two-dimensional. Just get out a pen and paper, calculate the angles, and *voila*

It's really car-friendly, because you can basically throw them up on the dash, add a waveguide, and you're off to the races.









The lens would look like this, but vary the depth. For instance, with a NEO 8 the depth would be about eight inches. (hence the name "neo 8")

Now if you juggle the angles, you'll start to notice that the windshield itself forms a nice reflector IF you get the distance to the apex right.

Basically you have to juggle the following:

The distance from the center of the diaphragm to the reflector
The distance from the diaphragm to the apex
The angle of the planar
The angle of the reflector
the converage angle









It's pretty darn similar to the mirror in a telescope, but in reverse

The main differences are the following:


In a telescope, the energy is focused to a point that's miniscule. Once you start drawing this out on paper, you'll start to notice that smaller is better when it comes to lenses and reflectors. Keep in mind you can easily address this by subdividing your ribbon into sections. (IE, stick a grating in front of it like the Danley Genesis horns have.)
The wavelength of sound varies quite a bit; if you want to cover two octaves we're talking about a ratio of four to one from the bottom to the top. That makes it very tricky to get a wide bandwidth out of the device. The solution to this is to simply use multiple lenses for multiple frequencies, like B&O did


*Anyways, I hope I didn't make this frighteningly complex. You could likely get good results from your windshield by simply drawing it out on paper, and then figuring out the location on the dash that will give you the best coverage with your ribbons. You'll likely find that adjusting the distance from the apex and the angle of the ribbon will yield an improvement. Don't bother doing this by ear; it's plain ol' geometry and you can do it on paper easily.*


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## danno14 (Sep 1, 2009)

Hmmmm..... I was thinking about getting some of the Neo10's but no real application. Maybe the dash of my motorhome! (Shi!t.... to many projects already)

A slick thing would be to "solve" this for the Neo's and be able to have them machined accordingly. Don't know how many would want/be willing to have something that sized on their dash though.....
Tagging along.


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## Patrick Bateman (Sep 11, 2006)

danno14 said:


> Hmmmm..... I was thinking about getting some of the Neo10's but no real application. Maybe the dash of my motorhome! (Shi!t.... to many projects already)
> 
> A slick thing would be to "solve" this for the Neo's and be able to have them machined accordingly. Don't know how many would want/be willing to have something that sized on their dash though.....
> Tagging along.


If you start drawing the wavefronts, you'll notice that 'solving' it is tricky. Because basically you want the sound to be in-phase when it arrives at your ears. But that's (nearly) impossible, because the wavelengths are so short at high frequency.

For instance, if you want 20khz to be in-phase, then *the distance from the edge of the Neo 10 to the center of the Neo 10 needs to be within 0.425cm (0.17")*

Which is *nearly* impossible.

There *are* solutions, but they get a little complex


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## Patrick Bateman (Sep 11, 2006)

Patrick Bateman said:


> While reading the Danley paraline patent, I accidentally figured out the maths for the Sausalito Audio Works lens.
> 
> The SAW lens appears to be a real "no brainer" for ribbons in the car. If I understand it right, it can take a wave and bend it 90 degrees. And not only can it do this, it actually makes the wave *more* coherent, not less.
> 
> ...



















If I'm not mistaken, the same technology used by the SAW lens was used to 'resurrect' Tupac at Coachella last week:

details here:

~ Sunshine ~ - Page 3 - diyAudio


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## mitchyz250f (May 14, 2005)

Patrick,

I am looking for a high efficiency tweeter and would love to do this with AST tweeters so that I could get some directionality (is that a word?) over the tweeters response to control reflections and increase sensitivity. I get the princible, but my concern is that Gedlee said that the drawing was over simplified and didn't the inventor say that there were other concerns that he couldn't discuss at the moment because of patent issues? 

Not to doubt what you are saying or the contribution you have made to this forum and MY own car audio installation, but unless this can be simplified a little more and the fabrication/design methods described, I can't use it. I have access to a 3D printer and could print right off of a CAD design if I knew what to do.


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## Patrick Bateman (Sep 11, 2006)

mitchyz250f said:


> Patrick,
> 
> I am looking for a high efficiency tweeter and would love to do this with AST tweeters so that I could get some directionality (is that a word?) over the tweeters response to control reflections and increase sensitivity. I get the princible, but my concern is that Gedlee said that the drawing was over simplified and didn't the inventor say that there were other concerns that he couldn't discuss at the moment because of patent issues?
> 
> Not to doubt what you are saying or the contribution you have made to this forum and MY own car audio installation, but unless this can be simplified a little more and the fabrication/design methods described, I can't use it. I have access to a 3D printer and could print right off of a CAD design if I knew what to do.


Here's one way of looking at it that might inspire you to experiment a bit:










Here's the polar response of a NEO8, which has a diaphragm that measures about 5cm by 12cm.

As you can see, *it's horrible.*

These planar and ribbon drivers have relatively HUGE diaphragms for a high frequency driver. For instance, the NEO3 has about ten times the surface area of a conventional tweeter.

And big diaphragms start beaming at a lower frequency than small diaphragms.

So that's what leads to this crazy polar response.



Having said that, I'd argue that one reason to experiment with reflectors and waveguides for planars is because they really don't have to be very big at all. For instance, when Zaph loaded a 1" tweeter in a waveguide it had to be relatively large, about 15cm, because he was trying to control directivity at LOW frequency.

We've got the total opposite problem. The polar response of these rippons is just dandy at low frequency, *but at high frequency it sucks.*

You can hear this very easily with a big ribbon or a planar. Listen to one on axis, then turn it 30 degrees. The top octave will disappear entirely. They're VERY directional.












Here's some food for thought, if you want to mess around with these a bit.

This is a NEO8PDR where I've done two things. First, I turned it on it's side, since that's the easiest way to mount it in a car. When you do that, the top octave just disappears. (see the graph above.)

The second thing I've done is place a reflector that's 5cm above the diaphragm. The idea is that all frequencies from about 6800hz and up will get reflected at a 90 degree angle, so that you can listen to it off axis and still hear the highs.

And then the last thing I did was use *two* reflectors, each pointed in seperate directions, so that the beamwidt is a bit wider.

Just some food for thought - and hardly a complex project. If you have a craft store nearby you can build something like this for about a dollar, and I assembled it in less than ten minutes.

As for Geddes, he is totally brilliant. BUT he's also 110% certain that his solutions are the best solution, and he's not afraid to tell you so. This doesn't mean that his opinions are invalid, but when it comes to his evaluations of a competing product, I always recognize that he has a bias because he's developed loudspeakers which are similar.

It's like asking a Ford engineer what he thinks of Chevys.

(Geddes used to do engineering for them BTW)


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## subwoofery (Nov 9, 2008)

Patrick Bateman said:


>


Looks like a good way to do a center channel... 

Wondering how well this would work with 2 x planars (each under its own reflector) and a ambiophonic system... 

Kelvin


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## mitchyz250f (May 14, 2005)

A few more of the million of questions in my head. 
1-We are always talking about matching directivity, but really don't want tweeters reflecting off everything. I do I reconcile these two things?
2-Those plastic 1/4 dome in the pics are a total guess/estimate of the needed shape correct? We really have no idea of the dispersion unless we calculate of the shape needed. And I have no Idea how to do that even with CAD.


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## Patrick Bateman (Sep 11, 2006)

mitchyz250f said:


> A few more of the million of questions in my head.
> 1-We are always talking about matching directivity, but really don't want tweeters reflecting off everything. I do I reconcile these two things?
> 2-Those plastic 1/4 dome in the pics are a total guess/estimate of the needed shape correct? We really have no idea of the dispersion unless we calculate of the shape needed. And I have no Idea how to do that even with CAD.


The size of the domes wasn't a guess.
When it comes to wavelengths, I go crazy with my calculator 

The Sausalito Audio Works patent and the Paraline patent do not state what the dimensions of the reflector should be.

But we can hypothesize, based on a few things:


A loudspeaker goes omnipolar at a certain frequency, regardless of whether it's a dome, a planar, or a cone
The frequency that it goes omni is basically equivalent to the diameter
A duct will control directivity above a frequency that's equivalent to it's diameter. (Note that the equation for the directivity of a duct and the directivity of a loudspeaker is the exact same equation.

Once you realize those threee things, you'll likely want to size your reflector so that it's reflecting the loudspeakers radiation *above* a point where the loudspeaker is going omni.

Does that make sense?

There's no good reason to use a large reflector, because it will simply reflect energy that's already radiated to the side anyways. For instance, if you're putting a reflector in front of a 2.5cm tweeter, it's pointless to reflect 4khz because the tweeter is already omnipolar at that frequency anyways. (34000cm / 2.5cm = 13600hz)

So...









With the Neo8, I plugged in the same variables. The Neo8 diaphragm is about 5cm in diameter, so it's going to be omni at 6800hz and down. To control directivity *above* 6800hz, we need a duct that's 5cm.

*So that's why the hemispheres are 5cm tall.*















It just occurred to me that you can skip all the calculations and simply use a reflector that's the same size as the diaphragm, since the equation is the same for both 


Also, I believe that effectiveness of the reflector would diminish above *and* below the frequency that it's tuned. But that's just a hypothesis. *So if you found that the driver sounded a bit dull, you might reduce the size of the reflector.* Note that this would reduce it's effectiveness at the lower frequencies though.


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## mitchyz250f (May 14, 2005)

Patrick, How do you deal with power response when the tweeters purposely a very limited dispersion.


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## ErinH (Feb 14, 2007)

mitchyz250f said:


> Patrick, How do you deal with power response when the tweeters purposely a very limited dispersion.


Flip them on their side. 


Sent from my iPhone. Pardon the grammar.


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## mitchyz250f (May 14, 2005)

Bikinpunk- I don't understand your answer. Maybe my question was poorly worded. If we are going for a limited dispersion tweeter 'setup' to reduce reflections and increase sensitivity, the power response will be poorly match to my mids. I have read over and over again, that matching power response is critical to the listening experience. But here we are doing it on purpose. The same thing happens will all horns I guess, so how is this reconciled?


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## Patrick Bateman (Sep 11, 2006)

Stumbled across this today. It's a prosound system that uses AMT tweeters. It's from a company called Void Acoustics. Their gear is installed at a club in San Francisco.


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## Patrick Bateman (Sep 11, 2006)

Unfortunately, the founder of BG died.
Now that BG is no more, are AMTs the best option for ribbon tweeters under $100?


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## Niick (Jun 3, 2015)

So here are some measurements I took just yesterday of this tweeter- the only pic of the tweeter I have is the one in the next post, it's a friend of mines, he left it with me for testing,


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## Niick (Jun 3, 2015)

Here is the tweeter

An impedance sweep of the tweeter reveals an extremely linear load, just like a resistor


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## Niick (Jun 3, 2015)

Patrick, too bad you're not still in Oregon, I'd love to check out some of you're work on lenses and waveguides live and in person, and maybe do some measurements too. Your work in this area, I think is really cool. It's good to see people thinking outside the box.


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## thehatedguy (May 4, 2007)

But he hadn't even been with BG for like a decade before his death.

BG is around, just out of the DIY market right now.



Patrick Bateman said:


> Unfortunately, the founder of BG died.
> Now that BG is no more, are AMTs the best option for ribbon tweeters under $100?


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## cvjoint (Mar 10, 2006)

Patrick Bateman said:


> Stumbled across this today. It's a prosound system that uses AMT tweeters. It's from a company called Void Acoustics. Their gear is installed at a club in San Francisco.


Which club? I'll go check them out. There are some gnarly sound systems here in SF.



Patrick Bateman said:


> Unfortunately, the founder of BG died.
> Now that BG is no more, are AMTs the best option for ribbon tweeters under $100?


I've used both many many times. AMTs do not have the bandwidth that the BG's have. I'd say the application is a bit different. BGs can cover upper midrange, AMTs cannot. 2khz and up AMT is a better choice. Under 2 khz BG planars are better.

BG is really just a well executed planar design. Aurum Cantus AMTs are top notch but expensive. Cheaper AMTs are sometimes garbage. BG vs. AMT will come down to how well the AMT is built, who builds it. Under 100 bucks you are likely to find many garbage AMTs.


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