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Chris A

Double Stack ESS AMT-1 with Wings--Possible Kit for Heritage

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2 hours ago, Thaddeus Smith said:

Seeing how fragile the leads can be, just want to be sure I don't blast them with power. Although, Rudy is using his EP4000's so maybe it's a non issue.

 

The leads are no more fragile than any winding in a speaker.  They are fragile only is so far as you don't pull directly on the wire leading to the diaphragm since there is nothing to stop you from ripping the wire off its solder joint.  The putty is only there to keep the diaphragm in place.  For example, you leave the leads connected to your barrier strip and pull up aggressively on the AMT to pull it out of its slot.....you rip the wire right off the solder joint INSIDE the diaphragm.  I can post pictures if you wish! And no, you can't solder it back on!

 

😱😱😱😭😭😭

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My progress getting my stacked wing assemblies cut and put together has been slow due to a new puppy. However, I was able to get a die made this weekend to cut the bases of my assemblies with the router. I really want to try the AMTs right up at the front of the bass bins so I need to have the front of the base open. The wings will extend out in front of the bass bin pretty far, but I have some ideas to keep the cantilevered weight stable. I will try to get some bases cut for the 7” and 12” wings and place them on the LaScala bins to give everyone an idea of their relative sizes.

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48A64E57-C33B-4F5C-9ED5-0C3D31814649.jpeg

5F290EA5-553E-476D-834F-C628EFA25250.jpeg

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1 minute ago, Randyh said:

I wish , I can understand your design , to make more bass , you need a bigger dog-house and a wider mouth , plus the woofer must be turned 180 degrees  -  as is ,what I see is a deeper-wider-mouth -

 

This is for the AMT high frequency drivers, not the bass bin.

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I have now installed one of my latest creations.  7" Symmetrical Wing structure for the double stack AMT. I will post pictures shortly, but here are the plots.  First some notes on the build:

-  7.25" Symmetrical, front and back, wings.

- No dowel rods on this build, much simpler to build and install drivers.

- Full wrap around on sides of wings.

- Instead of putty, I used black electrical tape to make a continuous, smooth seam where the AMT meets the wing.

 

@Chris A, I will send you the REW file in case you wish to expand on my results. Mic was placed 3 feet from Stack, level with the middle of the stack. Calibrated mic and REW. No EQ, No timing delay at all, no crossover in use.  Sweeps run from 400hz on up to protect the drivers somewhat.

 

 

SPL 7 inch wings.jpg

Taped Wings SPL.jpg

Taped Wings GD.jpg

Wing Phase Comparisson.jpg

 

 

Front Only Wings Spectrogram.jpg

Taped Wings Spectrogram.jpg

Edited by Rudy81
Correct Spectrogram Scale

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I just realized I inadvertently changed the scale of the Spectrogram between screenshots, so I will upload a change shortly to make them match. This is the final product without the top 'bow tie'.

 

 

Symmetrical Wings.jpg

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The tape I used at the seam is not as visible as the picture would suggest.  It basically disappears from a few feet away.  The bow tie top is just held on with double sided tape, giving it a more complete look yet allowing easy removal of the drivers.

 

BowTieandTape.jpg

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Sorry if my assumptions are wrong while looking at these measurements as I'm so green in these areas that I don't know what I don't know. LOL

 

I don't see much of anything to talk about between just the front wings and the front and back, am I completely missing something?

 

BTW, they look slick and look better with the rear wings.

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To see the difference in the various configurations, you'll probably have to run polar plots (i.e., measurements every 10 degrees off-axis).  In general the difference between front-only wings and symmetric wings is in the group delay values below 1 kHz (when only looking at on-axis measurements).  Additionally, the difference between 7" wings and 12" wings will be below 600-800 Hz. 

 

Even though these measurements look very similar to each other, the differences that I identified above are a big deal when trying to cross AMT-1s below 600-800 Hz, and when you run loud (above 100 dB on axis at 1 m for the AMT-1 assembly).  The long/symmetric wings will support the ribbon to lower frequencies and higher SPL and with lower group delay.  Additionally, the longer symmetric wings will produce better off-axis measurements (polars) than the shorter (7") front-only wings.

 

Chris

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7 minutes ago, Chris A said:

a big deal when trying to cross AMT-1s below 600-800 Hz, and when you run loud (above 100 dB on axis at 1 m for the AMT-1 assembly).  The long/symmetric wings will support the ribbon to lower frequencies and higher SPL and with lower group delay.  Additionally, the longer symmetric wings will produce better off-axis measurements (polars) than the shorter (7") front-only wings.

Thanks Chris.  I am reading and trying to absorb a bunch of this but that's the answer I needed based on trying to cross at those lower frequencies.  

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2 minutes ago, Pete H said:

Thanks Chris.  I am reading and trying to absorb a bunch of this but that's the answer I needed based on trying to cross at those lower frequencies.  

 

I think we're all cramming as many threads as possible into our heads and trying to digest in time for April's sessions.

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2 hours ago, Pete H said:

Sorry if my assumptions are wrong while looking at these measurements as I'm so green in these areas that I don't know what I don't know. LOL

 

I don't see much of anything to talk about between just the front wings and the front and back, am I completely missing something?

 

BTW, they look slick and look better with the rear wings.

 

I think we are so far along in our discovery that we are now dealing with the very small changes and improvements.  In my case, the symmetric wings were done to maximize the performance of the 7" front only wings.  I also decided on the 7" vs. the longer wings for various reasons.  Mainly, I don't need to cross at 500hz.  I can cross up to 1.2khz if needed.  So, for me, I couldn't justify the much larger wings for an improvement I didn't need. The size, weight and aesthetics of the larger wings didn't justify going that route for my needs. As a matter of fact, I just moved my xover point closer to 900hz just to see how it sounds.  I will live with that for a week or so and see how that sounds.

 

I bet that Chris could tell you a lot about small changes between the front only and symmetrical wing setups.  After quite a bit of time and energy working on this project, we are closing in on what can be done with just a double stack simple waveguide setup.  Now, if anyone can build a true horn for the stack, I suspect that would open up another area of  improvement.....how much, who knows.  So yes, the changes are minor, but that is simply a result of how far along we are in our discovery of what can be done. I sure hope someone can improve on what we have done! Then, we can all benefit.

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OK, so I just got home after spending a couple of hours in Rudy's music room. It was really cool to see all the new stuff since I'd last been there to pick up DBB's. Everything is impeccably crafted and sorted in the room. The sound of these drivers were superb - very articulate and a deep 3-dimensional soundstage. It was like the clarity of the Klipsch top end, but ever so slightly less edgy. I'm struggling to describe without esoteric buzzwords, but am really looking forward to putting something similar together in my room. My current room might as well be an octagonal dumpster in comparison to his well treated space, but I'm hopeful about the possibilities.

 

Chris - I certainly won't have the luxury of pulling mine out into the room such as Rudy, so I'll want to pick your brain further about what needs to happen behind the drivers when they're within 1-2ft of rear vertical surfaces.

 

All in all though, I'm absolutely confident this was the right thing to morph my system into and glad I was able to get out to Rudy's for a listen of something that's near complete.

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I know it's been mentioned a couple of times, but how would a waveguide achieve a better (or worse) response.  I guess I'm asking what would a waveguide improve?  I found an old beyma waveguide for an amt like product and some diy ones, like the one below.    Would it improve off axis listening? Or help with the crossover?  Just wondering how much effort it's worth over a "straight wing" design.

speakers 031.jpg

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56 minutes ago, tom1066 said:

but how would a waveguide achieve a better (or worse) response.  I guess I'm asking what would a waveguide improve?  I found an old beyma waveguide for an amt like product and some diy ones, like the one below.    Would it improve off axis listening? Or help with the crossover?  Just wondering how much effort it's worth over a "straight wing" design.

Well, it's a bit of a mixed story.  Note that some folks really like the dipole nature of the ESS AMT-1 driver, and that's the main reason why they prefer them (Rudy is probably one of those individuals, based on his comments to me). 

 

A conventional horn-loaded AMT, like the one in the Hawthorn Audio Rainier shown below, has a dipole loading, but the back is not horn loaded.  Contrast that with the symmetric wings that Rudy and others have put together and shown in this thread, and I think that you have your first "fork in the road":

 

Raniers-Augies-mid-high-driver-closeup-back.thumb.jpg.8785607091aa0fa2288aafb9c353e7cc.jpg

 

Additionally, the real impetus for going down this path (of this thread) is to use the AMT in a two-way loudspeaker design.  You really don't want to use a separate tweeter (...ever...), so the horn-loaded AMTs used in the Rainier have a reported low frequency cutoff of 450 Hz.  That's what caused the development of the wings in this thread, and then the symmetric wings--in order to lower the effective cutoff frequency and control the polars to a lower frequency (i.e., the AMT has lower moving mass than horn-loaded metal diaphragms and cone drivers, therefore have better self-damping properties).  This means that it's desirable to use the AMT diaphragm at lower midrange frequencies if its output is good (i.e., free from distortion). 

 

Chris

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2 hours ago, Chris A said:

 

 

A conventional horn-loaded AMT, like the one in the Hawthorn Audio Rainier shown below, has a dipole loading, but the back is not horn loaded.  Contrast that with the symmetric wings that Rudy and others have put together and shown in this thread, and I think that you have your first "fork in the road":ng mass than horn-loaded metal diaphragms and cone drivers, therefore have better self-damping properties).  This means that it's desirable to use the AMT diaphragm at lower midrange frequencies if its output is good (i.e., free from distortion). 

 

Chris

 

Thanks, I am going to go through this a couple of times to see how much I understand.

On some random search, I ran across one that had a waveguide on both sides.  Not sure what that would improve.

 

I have enjoyed following along and have been trying to stop myself from ordering another pair.  A previous AMT thread on this site led me to buying one pair last year and I've enjoyed them on top of my Cornwalls from time to time.

 

 

 

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7 hours ago, tom1066 said:

On some random search, I ran across one that had a waveguide on both sides.  Not sure what that would improve.

A double-sided horn loads the ribbon symmetrically from the front and rear sides in order to enable a lower cutoff frequency, as opposed to the Rainier AMT, which only loads the ribbon on the horn side--the rear side of the ribbon is vented to the room without horn loading.  The reason for this lower cutoff frequency is because the ribbon is supported symmetrically in a higher (oscillating) pressure environment acoustically.

 

Chris

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