I'm trying to make a single center channel speaker for home theater, stacking two of the original-type large tall Heil drivers that were used in the ESS speakers.
This has to fit underneath a large flat-panel TV, as I'm too lazy to deal with a projector and acoustically transparent screen; and I need the brightness of an OLED panel.
Then I intend to absorb most of the back wave, as they are bipolar. Like...maybe a futon on the front wall below the TV.
I have two drivers but don't know much about them, haven't listened to the type in decades but loved them back then. I'm hoping they radiate from most of their vertical size so that stacking them doesn't cause interference problems; I am hoping they sound like one and not like two stacked. The rest of my system is all planar dynamics (Newform and Magneplanar) can get pretty loud, so I hope two for the one channel will keep up. I can't fit my big planar dynamics under the TV and control the radiation pattern, so I like the idea of an AMT as a "folded" equivalent, and hope they sound similar (with appropriate processing). I have no idea how low they will go with two of them stacked; don't know how this design translates into a resonant frequency, but two might couple to the air better for making a larger waveform. I was even considering only running the top one full-range and letting the one below only kick in for the midrange. And of course I need some lowere mid-bass to complement them. I hope that two stacked goes low enough for male voice without crossover, which is pretty crucial for HT.
This will all be via active crossover.
And...if I really love them I might go in a similar AMT direction for ceiling Atmos later.
ANY AND ALL ADVICE, OPINION, RECOMMENDATIONS, EXPERIENCES, etc. much appreciated.
This has to fit underneath a large flat-panel TV, as I'm too lazy to deal with a projector and acoustically transparent screen; and I need the brightness of an OLED panel.
Then I intend to absorb most of the back wave, as they are bipolar. Like...maybe a futon on the front wall below the TV.
I have two drivers but don't know much about them, haven't listened to the type in decades but loved them back then. I'm hoping they radiate from most of their vertical size so that stacking them doesn't cause interference problems; I am hoping they sound like one and not like two stacked. The rest of my system is all planar dynamics (Newform and Magneplanar) can get pretty loud, so I hope two for the one channel will keep up. I can't fit my big planar dynamics under the TV and control the radiation pattern, so I like the idea of an AMT as a "folded" equivalent, and hope they sound similar (with appropriate processing). I have no idea how low they will go with two of them stacked; don't know how this design translates into a resonant frequency, but two might couple to the air better for making a larger waveform. I was even considering only running the top one full-range and letting the one below only kick in for the midrange. And of course I need some lowere mid-bass to complement them. I hope that two stacked goes low enough for male voice without crossover, which is pretty crucial for HT.
This will all be via active crossover.
And...if I really love them I might go in a similar AMT direction for ceiling Atmos later.
ANY AND ALL ADVICE, OPINION, RECOMMENDATIONS, EXPERIENCES, etc. much appreciated.
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I am afraid that what you are proposing is a bad idea. The stacking of a pair of Heil AMT's is going to narrow even further the poor vertical directivity.
Driving the Heil's with energy below around 1KHz will produce distortion, whether singly or as a pair.
I own a pair of the Heil tweeters and have a fondness for AMT's in general. Unfortunately acoustic principles say: that to maintain constant SPL the motion/excursion has to increase 4 times for each octave we go down in frequency. The pleat motion hits a brick wall when they start to collide with one another.
Sorry to be the bearer of bad news!
Keith
Driving the Heil's with energy below around 1KHz will produce distortion, whether singly or as a pair.
I own a pair of the Heil tweeters and have a fondness for AMT's in general. Unfortunately acoustic principles say: that to maintain constant SPL the motion/excursion has to increase 4 times for each octave we go down in frequency. The pleat motion hits a brick wall when they start to collide with one another.
Sorry to be the bearer of bad news!
Keith
I think this needs some real-world testing experiments. It all depends on the frequencies and levels, and would be trivially easy to just try stacking the two I have. The taller line could have interference that would narrow high frequency vertical pattern, even higher frequencies could create a taller cylindrical wavefront with marginally more height. I'm not really expecting them to go very low, but "people" say they don't really like being crossed as low as ESS sometimes did. They crossed some as low as 750hz. I have no expectation of going an octave below that of course! The results may show that I need to stack 4 to make much improvement. Of course for lows this does not alter any "Fs" just reduces excursion. My narrow Newform claim they can go lower too, but again that depends on level too. Other experimenters have shown the Heil ESS AMT can go low more reliably with some sort of extensions on the front "V" to elongate the cancellation path around the sides and also have some compression horn effect. I don't really want to go very low, but male voice can be critical for center channel. I'm not really seeking vertical coverage, or I would just lay a Maggie on its side under the screen.
On a more fundamental level I'm trying to get my "stereo" critical listening mind to address the unique problems of a center channel requirement, and get it to match my tall planar dynamics. A big line source behind an acoustically transparent screen could accomplish what I need, but I'm in love with the brightness, colors, and convenience of an OLED flat panel TV.
On a more fundamental level I'm trying to get my "stereo" critical listening mind to address the unique problems of a center channel requirement, and get it to match my tall planar dynamics. A big line source behind an acoustically transparent screen could accomplish what I need, but I'm in love with the brightness, colors, and convenience of an OLED flat panel TV.
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I haven't even attempted the first step, I haven't listened to them at all! I'm still thinking there's got to be a way to make a nice center-channel with them. I just can't get my mind to think about a center channel speaker UNDER a flat panel TV after all these years thinking "stereo". I am less than thrilled with the typical line of drivers laying down horizontally, which has horrible interference problems in the critical horizontal and horrible problems with floor and ceiling reflections.
Hmm, if they really beam vertically I could splay a bit vertically, but it's not something I like to do, can provide coverage but sound like an old sectoral horn. They LOOK like a line source, and line sources benefit from being made longer, "to infinity and beyond" LOL. I need to listen and find out what I got myself involved with. Makes me want to place the TV screen higher...something an audiophile more concerned about sound than the video might try LOL. One above the screen and another below? That's REALLY looking for interference. Maybe both in front of a large woofer (bit of delay on the AMT)? I have to think about a center-channel. I don't want to get involved with too freaking much processing...and I hate what most people use. I'd rather just stick a B&W bookshelf speaker under the TV if I get desperate...I have only one and never found a good use for it. Maybe that's at the psychological heart of my wanting to stack the AMTs, just because I already have two LOL.
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