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Chris A

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

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26 minutes ago, Randyh said:

Rudy , whatever happened tp this design ,  did  you give up on it and  trashed  it -

 

This is what I have sitting on my la scala for scale in the other thread. Going to build a set the same size but with the refinements shown above on his 7" version.

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2 hours ago, Randyh said:

Rudy , whatever happened tp this design ,  did  you give up on it and  trashed  it -

 

Not at all.  I decided that it was too large for me, but I used the same design for my current 7" wings.  I gave what you see in the pictures to @Thaddeus Smith so he could take it home and see if it fits his plans.  We can build a nicer version once he decides what he likes best. He has heard mine and seen the relative size of the 7" wings.

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@Rudy81 I am taking the free moments I have to draw up some bases for the wings on plywood to get an idea of the size difference between the 7” and the 12” assemblies. My instinct tells me to build the 12” but they are significantly larger than the 7”. I think the 12” will match the bass bin better, but I really want to keep the heil as close to flush with the bass bin as possible. This will over hang quite a bit as seen in the pic. Some overhang is ok, but this may be a little much. My question for you is how big of difference did you hear having the heil set back as opposed to being flush or close to flush with edge of your bass bin?

 

I know I need to just try it myself, but I would like to get your input before I make some saw dust!

98E74952-8C76-40FB-AEAE-05D9332614B4.jpeg

2E762F78-16E1-46F9-B276-D9DC399F8B25.jpeg

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1 hour ago, No.4 said:

@Rudy81 I am taking the free moments I have to draw up some bases for the wings on plywood to get an idea of the size difference between the 7” and the 12” assemblies. My instinct tells me to build the 12” but they are significantly larger than the 7”. I think the 12” will match the bass bin better, but I really want to keep the heil as close to flush with the bass bin as possible. This will over hang quite a bit as seen in the pic. Some overhang is ok, but this may be a little much. My question for you is how big of difference did you hear having the heil set back as opposed to being flush or close to flush with edge of your bass bin?

 

I know I need to just try it myself, but I would like to get your input before I make some saw dust!

98E74952-8C76-40FB-AEAE-05D9332614B4.jpeg

2E762F78-16E1-46F9-B276-D9DC399F8B25.jpeg

 

My experience is that the further back you move the drivers, the more you lose some of the 'airy' '3d soundstage' they provide in their raw form. 

 

The waveguides we are building and have built most assuredly help the diaphragm below 2kz.  Since I don't need to cross very low, I have even toyed with the idea of going back to the raw drivers alone since they just sound so awesome!  Even with the drivers about 6" back from the edge, with the 7" wings, they just lose just a little bit of the magic.  In this case, it is a worthwhile trade-off.  As in all things audio, it is always about trade-offs.

 

Honestly, for how easy it is to build a set of waveguides, it will be worth your time to build both.  Heck, you really don't even need to glue them.  Just a few brad nails to hold the shape should give you some practical prototypes.  I posted the graphs of each wing and the no-wing performance to help with the 'numbers' decision.  BUT, it is the sound that should have the last say.   

 

BTW, I originally hung my wings in the air as you are doing, but I just didn't like the look.....and that was with the 7" wings.

 

Edit: In looking at your pictures, I noticed your bass bins are close to the wall behind them.   Please let us know your experience with the dipole drivers close to the wall.  I am about 3.5' to 4' away from the wall behind them.  I am wondering if you will experience any issues being so close to a reflecting surface.....hopefully not. I know lot's of folks are also close to the wall and could use your review on the subject.

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@Chris A, I need a bit of advice on stack alignment relative to LP.  When using my Oris, I always toed them out a little due to high frequency beaming....which I have not found to be the case with the AMTs.  I just started playing around with aiming the center of the AMT at the LP.  Any downside to pointing the AMTs at the LP vs. toe out?

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Hi,

 

I have read through this thread with great interest! I already have a pair of driver using the AMT concept (Beyma TPL150H) and I like them a lot, but unfortunately the Beymas  cannot be used below app. 1,500 Hz, and stacked, original AMTs may be the way to go!

 

BUT I cannot help asking: If two stacked (and horn loaded) AMTs are excellent, then what about 4 stacked AMTs per side? Obviously, power handling/sensitivity and max SPL would be improved, but maybe more importantly: Would 4 stacked AMTs lower the crossover point - and if yes, then how far down?

 

I would really appreciate your thoughts on this (pros/cons? - besides being more expensive for sure!), and in case anyone buying 4 AMTs tried this, I would very much like to hear your experiences!

 

PS: I think Pete H already stated the question, but I do not think it received any answer (or I may have overlooked it)!

 

Thanks!

 

Best regards

Peter

 

 

 

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12 hours ago, Rudy81 said:

Any downside to pointing the AMTs at the LP vs. toe out?

I don't know of any constraints.  I've enumerated some thoughts that come to mind:

  1. Toe-in enables a subjective strongly broadened soundstage image with monopole loudspeakers--like your Oris horns and with virtually all other Klipsch loudspeakers. 
     
  2. Excess toe-in (crossing in front of the listening position) can be tried to see if it stabilizes the stereo image a bit more when the listener is slightly off-axis from the centerline between the loudspeakers. 
     
  3. Most people having toe-in issues (i.e., not being able to point the loudspeakers within 10-15 degrees of the main listening position) usually have reflective objects between the loudspeakers that create extra early reflections (which are undesirable)--including large racks with flat acoustically reflective sides, furniture, and loudspeakers, etc. between the stereo pair of loudspeakers.  (In your case, IIRC,  you have a clear area between and in front of the plane containing your left/right loudspeakers.)
     
  4. Dealing with the added rear wave reflections in-room from the dipole AMT-1 assembly are actually quite complex.  This is much more complex than the "requirements" that I've seen bantered about at places like diyAudio and other personal audio web sites. 
     
  5. The best approach in my experience with dipole radiators is to try some toe-in geometries and listen to music recordings having a strong soundstage effect.  I'd start with aiming directly at the center listening position and then increment the toe-in/toe-out in 10 degree increments. 
     
  6. Don't be surprised if you wind up with zero toe-in (no toe-in) and a head-in-a-vise effect with the dipoles if you're chasing the dipole effect.  My experience is that consistent and smoothly varying rear-wave reflections off the center of the front wall became the most important factor to consider--and not so much the side wall and front wall distances, although these are very important variables to control, too. 
     
  7. I found that chasing the zero toe-in dipole effect was like trying to create a headphone-like image in-room (i.e., depth of soundstage), while toed-in dipoles emphasize width of soundstage.  I never found a way to have both at the same time--it was one or the other.

Chris

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So mine will be just a foot or two away from rear surfaces, assymetrical side wall boundaries, with a TV in the middle of them, and a coffee table between the speakers and MLP. No big deal, right? :D

 

I'm building these speakers now while the group momentum is hot and with the foresight that I'll be building a new house with a dedicated room in the next 5-10 years.

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1 hour ago, Thaddeus Smith said:

So mine will be just a foot or two away from rear surfaces, assymetrical side wall boundaries, with a TV in the middle of them, and a coffee table between the speakers and MLP. No big deal, right?

Really, the issue is whether or not you're trying to use that dipole backwave like Rudy is, trying to get 99% out of it.  For my use, I place them on top of the Khorn clone bass bins, right in the middle of the top of the top hat:

 

AMT-1 on top of Khorn clone bass bin.jpg

 

I have no complaints.  If you're trying to get the same type of effect as a pair of Magnepans or MartinLogans, I can see where you'd want to move the AMT-1 assemblies away from the walls, but that's not possible if using Khorn bass bins (unless using large false corners).  This thread was started on the premise that many here would want to retrofit an AMT-1 assembly on top of their existing Heritage loudspeakers, and that's the way that I'm intending to use them.

 

I see no downside to this at all, in fact, it's a pretty big upside. 

 

Chris

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Excellent! Thanks for reiterating the purpose of the thread.. I think we're all attacking this from slightly different angles and listening goals.

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11 hours ago, Peter Krojgaard said:

If two stacked (and horn loaded) AMTs are excellent, then what about 4 stacked AMTs per side? Obviously, power handling/sensitivity and max SPL would be improved, but maybe more importantly: Would 4 stacked AMTs lower the crossover point - and if yes, then how far down?

It looks to me that the lowering of the crossover point for a stack of four AMT-1s would be fairly marginal beyond what a two-high stack can do, but there would probably be another 50-100 Hz lowering of the -3 dB low frequency raw response point.  The difference in low frequency cutoff point between a single AMT-1 and a stacked/winged (7") dual AMT-1 array is about a 130 Hz depression of the -3 db cutoff point (~585 Hz --> 450 Hz). 

 

Note that some EQ is required to flatten the natural tendency of the AMT-1's slightly rising response vs. frequency, so the relative depression of the -3 dB cutoff point is based on the low frequency response only, not the higher frequency response.  Moreover, it is important to note that the wings do help to depress the cutoff point a bit more than 50% of the difference from the single/non-winged configuration (indigo = winged, blue-green = no wings):

 

1180999562_StackedAMT-1svs.Stacked-WingedAMT-1s(7inwings)104dBonaxis.thumb.jpg.5375538b561a18b89e33f6bc8b26d334.jpg

 

Chris

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Update on my question about toe-in. Spent some time this afternoon listening for the changes in sound depending on toe-in.  My original setup has the AMT stack pointed to a spot which crosses my LP about 2 feet either side of my ears.  I originally had this with my Oris and preferred that orientation.  Today, I aimed the AMT stack at my ears and listened for a while, various test discs and music favorites.  My initial impression was that the image had narrowed somewhat, but the most noticeable change was the narrowing of the soundstage and a decrease in depth.  After a good while, I returned the stack to its original position and validated my initial impression.  With the AMTs aimed a couple of feet outside my ears, I get a much fuller and wider soundstage. The image is still very strong, but seems wider, allowing some lateral head movement without losing the nicely defined image.  Depth also returned to a much deeper soundstage.

 

Granted, this is all in my room....YMMV.  The hf quality did not seem to diminish at all when pointed outside my LP.  For now, the original setup is preferred.

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10 hours ago, Chris A said:

It looks to me that the lowering of the crossover point for a stack of four AMT-1s would be fairly marginal beyond what a two-high stack can do, but there would probably be another 50-100 Hz lowering of the -3 dB low frequency raw response point.  The difference in low frequency cutoff point between a single AMT-1 and a stacked/winged (7") dual AMT-1 array is about a 130 Hz depression of the -3 db cutoff point (~585 Hz --> 450 Hz). 

 

Note that some EQ is required to flatten the natural tendency of the AMT-1's slightly rising response vs. frequency, so the relative depression of the -3 dB cutoff point is based on the low frequency response only, not the higher frequency response.  Moreover, it is important to note that the wings do help to depress the cutoff point a bit more than 50% of the difference from the single/non-winged configuration (indigo = winged, blue-green = no wings):

 

1180999562_StackedAMT-1svs.Stacked-WingedAMT-1s(7inwings)104dBonaxis.thumb.jpg.5375538b561a18b89e33f6bc8b26d334.jpg

 

Chris

Hi Chris,

 

Thanks a lot for a detailed reply, I really appreciate it!

 

Best regards

Peter

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On 2/13/2020 at 6:16 PM, Rudy81 said:

Granted, this is all in my room....YMMV.  The hf quality did not seem to diminish at all when pointed outside my LP.  For now, the original setup is preferred.

 

This does not surprise me. The off-axis horizontal response of the AMTs was quite good. I took 0, 20, 40, 60 measurements and the AMT was performed perfectly well up to 20Khz+, 17Khz, 15Khz, and 13Khz, respectively. That.....to me....is solid. Based on that, I don't think its worth while to toe them in. 

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PS  - these 2db step graphs are killing me!. One has to really pay attention to the scale; otherwise its easy to dismiss the performance of the AMTs. 

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7 hours ago, dkalsi said:

PS  - these 2db step graphs are killing me!. One has to really pay attention to the scale; otherwise its easy to dismiss the performance of the AMTs. 

Yes, looks a little rough until you look closer.

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I took Toole's/Olive's recommendations to heart with regard to SPL flatness (i.e., ±1 dB is the target flatness...where possible).  When I save these plots from REW, my on-screen resolution is actually 1 dB/minor division vertically--and I keep it there all the time unless I can't see all the SPL response curve--like when I'm running a raw response measurements without PEQs to flatten response.  It makes a difference in the resulting sound. 

 

This is perhaps one of the things that can be demonstrated: the subjective effect of flattening from the nominal ±3 or 4 dB flatness that is commonly used to ±2 dB or even ±1 dB when it can be achieved.  That, combined with phase flattening though the crossover region, combine to produce the subjective "magic" that occurs with fully horn-loaded loudspeakers when SPL and phase response are flattened to this threshold level (i.e., much less than 360 total phase growth from 20 kHz down to the cutoff frequency of the bass bin, and group delay less than 1 ms from 500 Hz-20 kHz). 

 

REW screenshots rescale downward in resolution (i.e., not desirable) to typically two dB/division on screenshots if you use REW's screenshot function--the little camera icon at the top of the vertical scale on the top left of the plot window.  If you use "Snipping Tool" instead (the Windows application), you can capture exactly what you see on screen, but it's a bit harder to guess and therefore control the resulting size of the image files--which I like to keep as small as possible here while retaining enough resolution for readers to see the needed details in the plots.

 

Chris

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Yes--the AMT-1, either single or stacked/winged, etc. 

 

But note that the AMT-1 has about as narrow a vertical coverage angle as the Fostex supertweeters--about ±15 degrees (30 degrees included angle), which is why stacking the AMT-1s at least two-high is more effective in increasing the vertical coverage band in-room.  The AMT-1 easily covers 90 degrees horizontally, where I find that you need that degree of horizontal polar coverage in order to evenly illuminate the listener and acoustically reflective boundaries/objects in-room. 

 

Chris

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In my never ending quest to get the maximum performance out of my system, I recently found that there is more to be done besides EQ at the 3 foot distance.  I have been fighting a battle with a particular resonance which I could not tame by enhancing the internal bracing and open cell foam absorption of my bass bins.  Last week, in thinking about what Audyssey did in my system before I abandoned that process, I took a shot at running plots at the LP.  I found quite a different response, as one would expect, at the LP vs. the 3 foot point due to room interaction.  The major differences were related to the LF portion of the sweep, again, as one would expect.

 

I made some changes to the EQ based on the problems shown by the plot at the LF portion of the sweep.  I am now glad to report that the problem I had been fighting for months with resonance....is gone!  I wish I would have done this before spending quite a bit of money and time in open cell foam installation in the bass bins. The EQ required was not that great, but it made a huge difference in what I hear at the LP.

 

The performance of the AMT is so dang good, it needs no EQ at all in my room.  As we all know, room problems are mostly centered around LF unless you are listening to your speakers in a shower stall. 90% of my EQ is all in the range below 1kHz near which I have my crossover point.  I estimate I am currently crossing near 900Hz.

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