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View Full Version : Heil with a JBL Woofer part 2 Back wave attenuation for best in room balance.



Robh3606
01-26-2020, 01:46 PM
Has anyone tried any attenuation of the back wave?? I was just listening to a live recording and was impressed with how well the venue ambiance came through. That said on non live recordings I also get a sense of space but it seems the focus is less clear compared to either the F 206's or my horn systems.

I have been playing the the idea of trying to turn down the back wave just using some fiberglass batting to see if I can dial them in better. The goal is to increase focus but not loose the sense of space. I don't want to do an enclosure because of the potential of reflections back through the diaphragm just like putting a woofer in a box.

Anyone else try this?? I am going to give it a shot too see what happens.

Rob:)

Robh3606
01-26-2020, 03:43 PM
This is worth playing with. At least in my room. I did a quick check to see what would happen using some 4" batting paper left on. It had a significant effect in room. Normally I couldn't hear a change in balance doing a sit down stand up test. I can now this did a great job of attenuation and effected the balance in the sweet spot. Better clarity more focus with little apparent loss of ambiance.

It is clearly absorbing a great deal of the upper octaves but seems to be frequency shading the back wave and attenuating it as expected.

With some experimentation I could reduce or increase the energy level but either increasing or reducing the thickness of the fiberglass behind the driver. Want to try and get some measurements to see exactly whats being shaded out and how much attenuation there is.

Rob:)

Mr. Widget
01-26-2020, 05:16 PM
Hi Rob, I rotated your photo...

Interesting idea. For some reason all of the better ESS systems and many of the AMT systems by others have left the AMT driver as a dipole. I wonder if a better solution would be to place some Sonex or heavy curtains directly behind the speakers on the near by wall.

You may want to try both to see which you prefer.

On a parallel topic, I was considering getting a second pair of ESS drivers and running them stacked since it would be so easy to do with a length of threaded rod. I think this would help with the vertical dispersion.


Widget

dkalsi
01-26-2020, 05:39 PM
On a parallel topic, I was considering getting a second pair of ESS drivers and running them stacked since it would be so easy to do with a length of threaded rod. I think this would help with the vertical dispersion.


Widget

Widget - see this crazy thread at Klipsch Forums - https://community.klipsch.com/index.php?/topic/188177-double-stack-ess-amt-1-with-wings-possible-kit-for-heritage/

jmpsmash
01-26-2020, 06:04 PM
Widget - see this crazy thread at Klipsch Forums - https://community.klipsch.com/index.php?/topic/188177-double-stack-ess-amt-1-with-wings-possible-kit-for-heritage/

Very cool. I did try to look at what can be done. A while ago someone managed to do a quad stack. 4 on each side but didn't provide any measurements.

This one looks good except it still only go down to 500Hz with a fairly large "horn". Not high enough, not low enough. I hope he provide some distortion measurements too as that's one of the goal of going for an array.

jmpsmash
01-26-2020, 06:12 PM
Back to the main topic.

When I first read it, I thought you meant putting stuff at the front wall. I have tried nothing (just normal drywall), 2" absorption panel, and some wooden pattern paneling that scatters the sound (it is not strictly a diffuser as it is not diffusing sound uniformly like a QRD, etc).

Dry wall: there are the most amount of ambience sound, creating a more live sound stage. I like that sound. However, instruments and voices are less focused mixing around all the backwave and front wave. My AMT is ~4ft from the wall. I have achieved better imaging with 6 ft from the wall but I have found that there are tons of low frequency issue with the speakers that far out.

Absorption panel: Best imaging, but the magic of the dipole is very much diminished. A/B comparison the sound is dry and liveness.

Scattering panel: Kinda in between, not the best of both worlds, neither the worse. but like 50% of each.

Now I am tempted with a proper diffusion panel like a QRD. Those are crazy expensive. I need a long weekend to DIY one.

toddalin
01-26-2020, 09:29 PM
I had experimented with putting stuff (e.g., open cell foam) behind trying for a smoother frequency response, but settled on the wedgies. I may have to try again and see what the RTA says.

There are some things/frequencies (cymbols) where you would swear that the Heils are located right next to your ears, like headphones. Very uncanny. When I happen upon on a selection that does this again (don't recall which do), I'll have to try the open cell foam behind to see what that does to it.

jmpsmash
01-26-2020, 10:11 PM
I had experimented with putting stuff (e.g., open cell foam) behind trying for a smoother frequency response, but settled on the wedgies. I may have to try again and see what the RTA says.

There are some things/frequencies (cymbols) where you would swear that the Heils are located right next to your ears, like headphones. Very uncanny. When I happen upon on a selection that does this again (don't recall which do), I'll have to try the open cell foam behind to see what that does to it.

Or a soprano singing at the top of her lung when her ran away lover came back to see her just moment before she dies.

OMG my ears need some rest after that.

What I noticed is that the Heil reall loads up the front wall so some sort of absorption to get rid of that high frequency energy is needed, otherwise it bounces back around and end up loading up the whole room.

I have 4ft tall absorption panels almost covering the whole space between the two speakers yet the sound appears to come immediately above it. :banghead:

Robh3606
01-27-2020, 09:20 AM
Hello Widget

Thanks for the picture fix. Running them in stacks! That’s interesting! Have you fired yours up yet?

If not I would wait and see. With mine in full dipole operation there was no change in sit down/stand-up as far as the tonal balance. There was more than enough energy from the front wall reflections, behind the driver, to essentially mask any vertical directivity issues. It wasn’t until I tried the fiberglass that there was a change where you could hear a balance change out of the sweet spot.

This is just my impressions in my room so grain of salt. The issue as I see it is I have a little too much of a “good” thing. I have a pair of L5’s in the next room and the difference is quite notable. Heil lots of space, uniform tonal balance, very open but much less focused and a bit grainy for lack of a better word.

The L5 have them beat as far as focus and clarity which is why I wanted to see what would happen messing with the back wave. That’s a lot of bandwidth bouncing off that front wall and just like multiple sources it seems to be taking away from what they are truly capable of depending of course on what your goals are.

I would like to keep openness and ambiance but increase focus, clarity and loose the graininess.

Treating the front wall, behind the drivers, would be the more common approach but it’s expensive and hit or miss. I can easily change the thickness of the absorber as well as the absorbing material for a fraction of the cost and essentially have the same benefits. I should be able to measure the amount of attenuation and FR of the backwave to get a handle on what’s changing vs what changes I hear in the room response.

I was listening last night and it was a step towards what I wanted. Have to see tonight if I still feel the same way and wasn’t “caught up in the magic of the moment”

Rob :)

toddalin
01-27-2020, 11:36 AM
and a bit grainy for lack of a better word.

Rob :)

I often hear this, but wonder..., is it the Heils, or are the Heils are just revealing what's really there? Attenuating them a bit helps tremendously at removing the grain, but also removes a bit of HF detail. At least I have mine crossed over to keep the vocal fundimentals in the midrange, and just loose some sparkle and detail on those recordings when I turn off the HF switch and/or attenuate the Heil a bit.

I prefer to run the L-pads "full bore" for best "coupling" and the crossovers allow for this, so long as the recording does. But many recordings require a bit of HF attenuation, and yes, I do get up and adjust the crossovers to the recording on a disk by disk basis as necessary.

jmpsmash
01-27-2020, 12:47 PM
I often hear this, but wonder..., is it the Heils, or are the Heils are just revealing what's really there? Attenuating them a bit helps tremendously at removing the grain, but also removes a bit of HF detail. At least I have mine crossed over to keep the vocal fundimentals in the midrange, and just loose some sparkle and detail on those recordings when I turn off the HF switch and/or attenuate the Heil a bit.

I prefer to run the L-pads "full bore" for best "coupling" and the crossovers allow for this, so long as the recording does. But many recordings require a bit of HF attenuation, and yes, I do get up and adjust the crossovers to the recording on a disk by disk basis as necessary.

I also would classify my Heil AMT as grainy. It is very apparent after swapping between the Heil and a Focal metal dome tweeter. Despite having even flatter frequency response the Focal is much smoother and has better clarity.

jmpsmash
01-28-2020, 10:44 AM
My Heil have frequency peaks at 5k and 10k. After smoothing those out, they are less shouty than before.

toddalin
01-28-2020, 11:02 AM
My Heil have frequency peaks at 5k and 10k. After smoothing those out, they are less shouty than before.

Hence the wedgies in which we control these "mechanically" and through crossover component selection rather than through add-on electronic filtering. ;)

Robh3606
01-28-2020, 05:13 PM
Having some fun with this. Using hobby store black felt folded in layers of 2 and 4. Just took a 12 X 12 cut it in half and folded it to get 2 layers, then folded it again for 4. Works like a charm easy as hell to adjust and leave plenty of output even with 4 layers to get the ambiance and take the edge off. I have to try and measure this on the weekend to see what the deal is.

Rob:)

Mr. Widget
01-28-2020, 07:12 PM
Hello Widget

Running them in stacks! That’s interesting! Have you fired yours up yet?I did just before I had my Project Widgets up and running. I paired the AMTs with a pair of of PHL 12" woofers in some old test boxes. I ran them bi-amped at 800Hz and was not thrilled with the sound overall. I don't think the AMTs were the weak link there.

I did have them out in the room and the back wave was allowed to do its own thing... when sitting the highs were pretty good, but when standing there was a significant roll off up top. That is what led me to think about extending them.


Widget

Robh3606
01-29-2020, 07:07 AM
Here take a look at this it will give you a handle on the effects of stacking a pair. They are very directional so the parallels should be close.

Rob :)

Mr. Widget
01-29-2020, 08:05 AM
Here take a look at this it will give you a handle on the effects of stacking a pair. They are very directional so the parallels should be close.
I donít think they behave the same way off axis as the horns do. It would be interesting to test.

I have heard line arrays made with non-ESS AMT tweeters. I was very impressed.


Widget

Robh3606
01-29-2020, 08:13 AM
I don’t think they behave the same way off axis as the horns do. It would be interesting to test.

I have heard line arrays made with non-ESS AMT tweeters. I was very impressed.

Nice! Have never had the pleasure. No not exactly but take a look at these polars. Might open up bellow 4 K but overall pretty directional. The vertical is tight. Just with the stacks expect some lobbing depending on distance. The PDF is just a reference you won't know unless you measure.

Rob :)

dkalsi
01-29-2020, 08:32 AM
Here is the measured vertical response of the Heil AMT1 (ignore the SPL magnitude - these measurements were taken 1M from the AMT at 90db volume).

Vertical response is good to 10K +/- 10 degrees, otherwise its collapses pretty quickly beyond 5.5Khz in the vertical plane.

badman
01-29-2020, 08:54 AM
Hence the wedgies in which we control these "mechanically" and through crossover component selection rather than through add-on electronic filtering. ;)

When you say mechanically do you mean the addition of compression and diffraction? The reduction in "throat" area may make for some increase in effective mass, and the triangle "wedgie" is a diffraction source beyond that, spreading into essentially two "mini horns" loading the "throat" rather than one diaphragm.

"Add On" filtering is a bit of a misnomer if you are looking at active systems. Heils are inherently well behaved and thus XOs largely behave as-textbook, including notches/shaping, but active allows a whole 'nother degree of control that is more benign than the passive XOs. For heils, you want a very steep highpass if you want to cross them low, active does "steep" much better than passive. The waveguides I gave you provide a significant lift down to most reasonable XO points, which means you can electrically cross higher and/or less steep while not increasing diaphragm displacement or power input.

RTA is great but if you can get some high resolution multi-axial data together, and distortion data, you'll be in a much better place to refine your design, 1/3 octave is what I'd initially used when working with Heils but higher resolution gives you much more insight. If you like what the wedgie's doing, you may try a semicircle profile appended to the outward side of it, to smooth diffraction from those hard edges near your high frequency device.

The lateral on them can be treated as a horn, but note on the flat sections of the waveguides I provided that a top panel can also be applied- it makes limited difference- the heil, being tall, is already relatively directional in the vertical.

toddalin
01-29-2020, 11:57 AM
When you say mechanically do you mean the addition of compression and diffraction? The reduction in "throat" area may make for some increase in effective mass, and the triangle "wedgie" is a diffraction source beyond that, spreading into essentially two "mini horns" loading the "throat" rather than one diaphragm.

"Add On" filtering is a bit of a misnomer if you are looking at active systems. Heils are inherently well behaved and thus XOs largely behave as-textbook, including notches/shaping, but active allows a whole 'nother degree of control that is more benign than the passive XOs. For heils, you want a very steep highpass if you want to cross them low, active does "steep" much better than passive. The waveguides I gave you provide a significant lift down to most reasonable XO points, which means you can electrically cross higher and/or less steep while not increasing diaphragm displacement or power input.

RTA is great but if you can get some high resolution multi-axial data together, and distortion data, you'll be in a much better place to refine your design, 1/3 octave is what I'd initially used when working with Heils but higher resolution gives you much more insight. If you like what the wedgie's doing, you may try a semicircle profile appended to the outward side of it, to smooth diffraction from those hard edges near your high frequency device.

The lateral on them can be treated as a horn, but note on the flat sections of the waveguides I provided that a top panel can also be applied- it makes limited difference- the heil, being tall, is already relatively directional in the vertical.

Good to hear from you Jeff.

Yes, "mechanical" provides both compression and diffraction. My plots show an increased output of the lower frequencies through loading and a decrease at the peaks from diffraction, just as my slant plates do for the 2402, though probably not to the same extent. I would bet that like the slant plates, lateral dispersion is increased, especially for theose frequencies that were peaky.

I do have two shapes of wedgies with one being a triangle, and the other "contoured" as you suggest. This was cut section at a time on the laser and the pieces stacked. The included plots are for the contoured version. The exact distance from the point to the diaphragm is critical and must be done with an RTA or similar to maximize its benefits. Too close and the highs are lost, and too far does not provide the desired effect.

Because I cross them over at ~4kHz, the wavelengths are much shorter and cause less cancellation.

Brass and acrylic, Phase 1:

http://www.audioheritage.org/photopost/data//500/medium/DSC_000312.JPG

http://www.audioheritage.org/photopost/data//500/medium/DSC_00065.JPG

Clear acrylic triangle, Phase 2:
http://www.audioheritage.org/photopost/data//500/medium/DSC_00048.JPG

http://www.audioheritage.org/photopost/data//500/medium/DSC_0006_2_.JPG
http://www.audioheritage.org/photopost/data//500/medium/DSC_0004_2_.JPG

Laser cut black acrylic stacked sections, Phase 3:

http://www.audioheritage.org/photopost/data//500/ScreenHunter_193_Feb_18_18_27.jpghttp://www.audioheritage.org/photopost/data//500/medium/DSC_00122.JPG

http://www.audioheritage.org/photopost/data//500/medium/DSC_00121.JPG

http://www.audioheritage.org/photopost/data//500/medium/DSC_00093.JPG


http://www.audioheritage.org/photopost/data//500/medium/DSC_00151.JPG

toddalin
01-29-2020, 12:05 PM
Here take a look at this it will give you a handle on the effects of stacking a pair. They are very directional so the parallels should be close.

Rob :)

There are four ways to stack these. They can be stacked vertically, horizontally/vertically, horizontally/horizontally (toed out as was done by Heil), or one can be turned 90 degrees. The difference? :dont-know:

Know that Heil ran their "professional model" (AMT 6) with several of the AMTs set 90 degrees from their home offerings and toed out in an arc.
https://i.pinimg.com/originals/3d/99/d8/3d99d854b5c139a78167f0ef13197873.jpg

https://img.usaudiomart.com/uploads/large/661007-vintage_ess_professional_amt_6_loudspeakers.jpg

jmpsmash
01-30-2020, 06:06 PM
Hence the wedgies in which we control these "mechanically" and through crossover component selection rather than through add-on electronic filtering. ;)

your wedgies piece looks great, but the understanding of how and why it works, is unfortunately a bit beyond my understanding of acoustics. :confused:

toddalin
02-03-2020, 06:46 PM
When I access my entertainment center to put in a disk/make an adjustment, I stand behind the left speaker, right infront of the back of the tweeter.

When I change my Yamaha RX-Z9 into "CD Direct" mode that turns off all of the digital circuits and panel lights (essentially puts the Oppo 95 CD player directly through the volume control circuit to the two main channel power amps), the "hash" level goes way down and this is easily notable to my ears. And this should be a very subtle change.

So I ask again, is the the AMT that is harsh, or is it just passing inherent harshness in the system along to the listener? :dont-know:

badman
02-10-2020, 06:38 AM
So I ask again, is the the AMT that is harsh, or is it just passing inherent harshness in the system along to the listener? :dont-know:

If the direct mode sounds vastly better you need a better solution than the yamaha. Heils are not at all inherently harsh once they've been smoothed out from a frequency response perspective.

toddalin
02-10-2020, 11:51 AM
If the direct mode sounds vastly better you need a better solution than the yamaha. Heils are not at all inherently harsh once they've been smoothed out from a frequency response perspective.

"Direct mode" is the solution to removing digital artifacts and noise through the receiver, but they still remain to some extent through other aspects of the system (conversion within the Oppo) and recording process, and the Heils let us hear them. Others who have complained of harshness may want to investigate other avenues to remove digital aspects/artifacts from their system and report back.

toddalin
02-10-2020, 06:58 PM
I've moved my speakers about and they are now closer to the back wall with one of the Heils now in front of a big mirror. The other one is sort of in front of a smaller picture.

I was listening to the Doobie Bros a bit ago and thought a track was too bright. When I adjusted the L-pad, I had my ear beside the Heil and its reflection from the mirror creating a glare was unmistakable. These are also probably the frequencies that sound like they are "right at your ear" as described previously.

I put the open cell foam behind them (but didn't replay the track) and will try some different foam types/placement.

toddalin
02-12-2020, 11:27 AM
Was listening to ELP Pictures at an Exhibition last night (original CD) and was hearing a distortion in the left channel that seemed to eminate from the Hammond, rather than the system. The Ethyl Mermans are very revealing. Maybe someone could listen for this and comment as to whether they also hear it?

Robh3606
02-12-2020, 01:25 PM
Hello Toddalin

Go checkout some tunes from The Nice. Pictures is quite long where Blues Variation?

Rob :)

toddalin
02-12-2020, 04:19 PM
Hello Toddalin

Go checkout some tunes from The Nice. Pictures is quite long where Blues Variation?

Rob :)

I believe so. I'll listen again in the near future and get a track#/time.

macsic
02-13-2020, 08:04 AM
Was listening to ELP Pictures at an Exhibition last night (original CD) and was hearing a distortion in the left channel that seemed to eminate from the Hammond, rather than the system. The Ethyl Mermans are very revealing. Maybe someone could listen for this and comment as to whether they also hear it?

I listened to ELP Pictures at an Exhibition to also hear what you were talking about distortion on the left channel on my nearfield monitor Genelec 1031A, reassuring?
Anyway good memory of a show I saw in the 70s :-)

toddalin
02-13-2020, 10:23 AM
I listened to ELP Pictures at an Exhibition to also hear what you were talking about distortion on the left channel on my nearfield monitor Genelec 1031A, reassuring?
Anyway good memory of a show I saw in the 70s :-)

So, were you able to hear the distortion?

macsic
02-14-2020, 08:15 AM
So, were you able to hear the distortion?
Hi,
I also come to the same conclusion as you, the distorted sound that I have also observed several times comes from Keith's Hammond in my opinion and not from your system because I too can hear it :) (exemple: on #6 Blues Variation and...)

toddalin
02-14-2020, 10:36 AM
Hi,
I also come to the same conclusion as you, the distorted sound that I have also observed several times comes from Keith's Hammond in my opinion and not from your system because I too can hear it :) (exemple: on #6 Blues Variation and...)


Vindication! Thanks.

Listen to Tarkus and you'll hear the "chiff" in the Hammond, almost continually, in the left channel.

The problem with "high resolution" speakers is that you also hear all of the flaws in the recording chain. I hears lots more stuff on the Merman's than on the the L300s. Also the Mermans do "reverb trails" properly, and the L300s pale in comparison in this area.