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Chris A

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

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3 hours ago, rplace said:

That is some good looking graphs for quick and dirty.

 

I know...crazy!  Literally 10 or so minutes to get those results.  Having learned Chris' technique for timing, its ridiculously easy. I used to spend hours tweaking phase and working on guessing the correct timing delay. The REW EQ function makes EQ'ing easy as well. 

 

In the coming days I will continue working on tweaking to obtain the best results I can in the current configuration.

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8 minutes ago, Rudy81 said:

Literally 10 or so minutes to get those results.

 

9 minutes ago, Rudy81 said:

I used to spend hours tweaking phase and working on guessing the correct timing delay.

 

I fear the latter was necessary to achieve the former. I'm hoping to leapfrog a bit through my time at your place and during Chris' session in April.

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16 minutes ago, Thaddeus Smith said:

 

 

I fear the latter was necessary to achieve the former. I'm hoping to leapfrog a bit through my time at your place and during Chris' session in April.

 

Just read 'Sensei's' thread:

 

And, this one.

 

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52 minutes ago, Rudy81 said:

 

Just read 'Sensei's' thread:

 

And, this one.

 

 

I've read through big chunks of those, but I'm a tactile learner. I'll need all of the components in front of me to work with and active feedback from more experienced folks to work through what the plots are telling me, what to change in response, etc. There's a lot of content in those (and related) threads which just means absolutely nothing to me while reading theoretically.

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3 minutes ago, Thaddeus Smith said:

 

I've read through big chunks of those, but I'm a tactile learner. I'll need all of the components in front of me to work with and active feedback from more experienced folks to work through what the plots are telling me, what to change in response, etc. There's a lot of content in those (and related) threads which just means absolutely nothing to me while reading theoretically.

 

Oh, you want the easy way! Nice! 😄

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Black putty installed on sides.  If anyone wants to try the same material, I obtained 'Black Plastilina Modeling Clay' from Hobby Lobby. Easy to mold and supposedly never hardens.

 

 

Putty.jpg

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1 hour ago, dkalsi said:

Did the putty help?


Sent from my iPhone using Tapatalk

No clue if it will help or not.  It was part of my plan to make the transition from the AMT to the waveguide as smooth as possible since we are dealing with high frequencies and short wavelengths.  I figured it can't hurt and @Chris A recommended I fill those spaces in.

 

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From my K-402- MEH efforts, putting slots and ports on the horn walls is something that you do with care in order to not affect both on-axis and off-axis SPL response.  The frequencies that will be affected are those that are exactly 1/4 wavelength (as measured along the central axis of the horn), so you can calculate where the discontinuities in SPL and phase response will be.  The depth of the horn at those indentations is 2 1/4 inches (approximately) so the formula is:

 

(13584 inches/second)/2.25 inches * (1/4 wavelength) = 1509 Hz

 

This is right at the point where there is a local rise in group delay for the stacked/winged AMT-1 assembly from Rudy's measurements.  If you wish to keep the group delay growth down in this frequency band, filling in the discontinuities in the wing side walls is a good first task to undertake to mitigate the group delay rise.  The second task (as I mentioned above) is to either provide rear side wings or something like a foam plug to provide acoustic support to the AMT diaphragm at the point where the plastic housing side walls terminate and the radiation pattern from the rear side of the AMT-1 is free to expand suddenly without horn support. 

 

Chris

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1 hour ago, Chris A said:

 

This is right at the point where there is a local rise in group delay for the stacked/winged AMT-1 assembly from Rudy's measurements.  If you wish to keep the group delay growth down in this frequency band, filling in the discontinuities in the wing side walls is a good first task to undertake to mitigate the group delay rise.  The second task (as I mentioned above) is to either provide rear side wings or something like a foam plug to provide acoustic support to the AMT diaphragm at the point where the plastic housing side walls terminate and the radiation pattern from the rear side of the AMT-1 is free to expand suddenly without horn support. 

 

Chris

 

Well, I'm committed now.  Getting ready to pack up the center Oris 250 and the Oris 150 are spoken for.  Onward at this point.

 

Been listening all morning.  So far still love the sound, so this is just the beginning of this project.  These drivers, to my ears, are just awesome.  Frankly, they are showing the limitations of my bass bins.  I'm going to have to take another shot at OB low end.  Yikes, more projects. 

 

In the mean time, I will start working in my spare time on a prototype with rear wings and any improvements I can make to the current build.  Although, as I built the waveguide setup, it is really easy to put together and take apart if you need.  Very solid, no vibrations at high volume.....so far seems like it was worth the effort. I am looking forward to the results of anyone testing a longer waveguide.  I'm not opposed to making it larger.  The only problem with longer wings is that there is definitely a better, more open sound when the drivers don't have any solid surface immediately under the waveguides. 

 

 

 

 

AMTtheater.jpg

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15 minutes ago, Rudy81 said:

Frankly, they are showing the limitations of my bass bins.

 

tumblr_m7zui8MtGM1rbjw6do1_250.gif%23val

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5 minutes ago, Thaddeus Smith said:

 

tumblr_m7zui8MtGM1rbjw6do1_250.gif%23val

Michael, you're cracking me up!

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17 hours ago, Rudy81 said:

The only problem with longer wings is that there is definitely a better, more open sound when the drivers don't have any solid surface immediately under the waveguides.

Just so I'm clear about what you're saying, if they were suspended with only the side wings and nothing on the bottom, they sound better?  There's a way to do that if that's what you're saying and if that's the case, I would try and come up with something when mine arrive.  If suspended would be better, do you have any indication of how much space between the bottom of the driver and any hard surface would you think is optimal?  

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Best thing to do is to try this yourself.  When you get the drivers, place them at the edge of whatever surface you are using to support the drivers.  Listen for a while, paying particular attention to the soundstage size and breadth.  After you get a good feel for that sound, simply slide the driver back from the edge 8" or 10" and listen again.  In my case, I felt that the soundstage was not as large and sounded a bit more constrained.  Could just be me. We all seem to hear different things when evaluating.  Frankly, I would prefer to keep the drivers back from an aesthetic perspective. But, I'm after the sound and not necessarily how pretty it looks.

 

I would be hesitant to vertically move the drivers too far above the bass cabinet in a suspended type of arrangement.  My guess would be that the more you move the drivers away from the bass producer, the more you lose coherence at the crossover area.  But heck, I'm just playing around with all this, and you guys should too.  I'm no expert on any of this.  With the compact size of the drivers, moving them around is too easy not to try variations and options.

 

I am looking forward to what you guys 'hear' when you get the drivers.  BTW, there is about a 2 or 3 hour break in period.  I never believed the whole break-in thing until I was able to see it in a Group Delay measurement with these drivers.  Doesn't take long.  Yesterday I broke in a new set for my center channel. Just played music through them for a couple of hours in the morning.  When I ran the GD test, they were just like the others I have. 

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8 minutes ago, Rudy81 said:

My guess would be that the more you move the drivers away from the bass producer, the more you lose coherence at the crossover area. 

 

Correct! You certainly don't want the center (of the AMT) to center (of the mid-bass/bass driver) distance to exceed the wavelength at the crossover frequency. Doing so will likely result in severe lobbing/cancellation. 

 

As an example, if you are crossing at 800hz, you don't want the center to center distance between the AMT and the mid-bass driver to exceed 43 cm, or approximately 17" (wavelength of 800hz). 

 

Once I get my AMTs, I plan of putting them directly on top of a 12" driver and will plan on crossing the drivers somewhere between 1200 - 1600 hz. 

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I'm curious what @Chris A and @Rudy81 among others think about a "gap" between the stacked drivers? I'm very much drawn to Pure Audio Project's concept for their OB speakers and the ability to modularly configure for WTW or WWT or even multiple 10" or 15" LF drivers.  Below is a picture of single ATM between two 15" LF drivers. They sell ready made brackets for adding the ATM to the baffle. What if I were to build a baffle with the correct height wings, left and right only, directly off the face of the baffle? Looks like an inch or more all around the brackets.

 

Obviously my design would have a larger/taller middle baffle.

 

As long as the wing cover both ATMs fully stacked height would a gap between them when stacked be an issue?

 

I find this comment about their brackets interesting. Any thoughts?

 

Quote

The mounting plate allows phase adjustment by simply moving the Heil AMT driver along the Z axis

 

http://www.pureaudioproject.com/product/heil-ess-amt-mounting-plate/

 

Trio15-HeilAMT-Cat-Open-Baffle-Speakers-

 

Heil-ESS-AMT-Mounting-Plate-for-Open-Baf

 

29BA6835-01E9-484D-BE34-D6B3D52A9049-687

 

Quintet15-Horn1-Open-Baffle-Speakers-wit

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Rich,

I suspect a gap between drivers would reduce the lower frequency loading we are trying to achieve.  I also am looking at a similar setup as the Pure Audio Project, but a DIY version  IF I decide to try and go OB again. For now, I continue to work on my bass bins....which I only built last year.

 

Could you fashion a DIY panel for the Pure Audio Project speaker as follows?  Make a taller panel with a hole large enough to fit the stacked drivers AND the wings.  The whole thing can be easily supported with some 45 degree metal brackets in the back.  Basically, copy what I made and slide it into the hole, attached and supported from behind.  If you are using an active crossover, which is the only reasonable way to do this, you can change the timing and EQ using the crossover. I don't see why that wouldn't work. 

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I am for sure going to DIY a set. If I like the sound with the current materials I have on hand my thoughts were to only buy the 15" woofers and perhaps the white baffles. My frames will need to be higher to accommodate the double stack ATM

 

8 minutes ago, Rudy81 said:

Could you fashion a DIY panel for the Pure Audio Project speaker as follows.  Make a taller panel with a hole large enough to fit the stacked drivers AND the wings.  The whole thing can be easily supported with some 45 degree metal brackets in the back

 

My initial thought was a lot like  yours, more or less copy your design and create a hole big enough for it to slide into form the back. Not having the ATMs in hand I was not sure how the secure them. Those brackets just seemed like I could focus all my efforts on the rest of the project. I really like the idea of having multiple baffles to experiment with different full range drivers. I'll update as I go along.

 

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1 minute ago, rplace said:

I am for sure going to DIY a set. If I like the sound with the current materials I have on hand my thoughts were to only buy the 15" woofers and perhaps the white baffles. My frames will need to be higher to accommodate the double stack ATM

 

 

My initial thought was a lot like  yours, more or less copy your design and create a hole big enough for it to slide into form the back. Not having the ATMs in hand I was not sure how the secure them. Those brackets just seemed like I could focus all my efforts on the rest of the project. I really like the idea of having multiple baffles to experiment with different full range drivers. I'll update as I go along.

 

 

When complete, my waveguide is one 'solid' piece.  The drivers are attached to the base and the top with the threaded rods that go through the drivers, top to bottom.  I could flip my entire unit upside down and the whole thing would stay together.  Your idea is easier than you think, you just need to support the back of the base from behind the baffle.  Only half the driver and the waveguides would be in front of the baffle. 

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11 minutes ago, Rudy81 said:

Your idea is easier than you think

 

Sounds like it given you understand what I am thinking of doing.

 

12 minutes ago, Rudy81 said:

Only half the driver and the waveguides would be in front of the baffle. 

 

And I can envision a way to give it a bit of fore and aft movement within the baffle

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