[Horizons]

I never stayed with my various OBs because I couldn't get the detail I wanted with compression drivers. However, I have been listening to Heil AMTs crossed over at 24 db/octave at 1 K and these are truly amazing dipole tweets.

So, I am thinking about an AMT based OB with either 2 15 Alphas crossed at 1K or two 12s. 12s might work better crossed that high. Any recs on a pair of 12s that give you that magic live OB sound and are clean to 1 kHz? I like and have used the Alphas but I already have two subs (ML sealed) and thinking that maybe there is something better to mate with the AMTs.

Or twin Betsy's??

TIA

[matevana]

If you are going to invest in a set of Heil AMT's and plan to cross that high, take a look at some of the LF Altec Lansing drivers reworked by Great Plains Audio. Your woofers will be reproducing some very critical fundamentals and you will want something that is very articulate to match the speed and clarity.  http://www.greatplainsaudio.com/woofers.html

As an alternative, you may want to contemplate a 3-way design, using a small midrange coupler between the LF and HF sections. The Hestia V is an example which uses the Dayton AMT and a mid-coupler, albeit crossed much higher.

 

[bladesmith]

If you are going to invest in a set of Heil AMT's and plan to cross that high, take a look at some of the LF Altec Lansing drivers reworked by Great Plains Audio. Your woofers will be reproducing some very critical fundamentals and you will want something that is very articulate to match the speed and clarity.  http://www.greatplainsaudio.com/woofers.html

As an alternative, you may want to contemplate a 3-way design, using a small midrange coupler between the LF and HF sections. The Hestia V is an example which uses the Dayton AMT and a mid-coupler, albeit crossed much higher.

Matevana,

where would you think the best place would be, to cross over the Heil AMT's ?

[steve f]

You are going to need a mid bass coupler of some sort. There is going to be too big of a frequency hole between the Heil and the Alpha. Just for grins, take a look at Ed Schilling's Horns. He uses a Fostex for the mid bass. The AMT is series wired to the mid. I know this combo works well. All you would have to do is figure out where to bring in the Alphas. A starting point anyway.

[Mmaxed]

Start reading here.

http://www.hawthorneaudio.us/forums/viewtopic.php?f=2&t=5002&start=15

[matevana]

Matevana,

where would you think the best place would be, to cross over the Heil AMT's ?

In all fairness I have only worked with the Dayton AMTPro (dipoles) which are licensed by Heil but have different properties. I preferred them crossed much higher, in the area of 6-7k with a more shallow slope (6-12dB per octave). I use a Seas MU10 (4' midrange) which couples the AMT to the LF driver. Crossing higher will typically yield more balanced waterfall plots, so it also depends what your overall design goals might be.  Hope this helps.   

[Horizons]

Thanks for the info. The Hawthorne thread is interesting with an Alpha 15 crossed to the AMT at 5K. I already own a pair of AMTs and a pair of Ed's horns. Its a great match but I miss the OB sound of my old Emerald Physics clones. Those had an OB pair of Alphas with a compression driver crossed at 1K. I have heard the Alpha's crossed at 1 K and never had a problem with them. My current AMT/horns use Ed's series xover and are roughly crossed around 1K too.  I'm very tempted to just try 2 15-inch Alphas on a simple OB and electronically crossed to the AMT around 1 K.  I don't think you get the magic of the AMT if crossed at 5KHz.

Very helpful responses.

[opnly bafld]

Wild Burro Audio Betsy 8" with bass help?

http://www.randallrash.com/New_Loudspeakers_part9.html

http://www.wildburroaudio.com/speakers.php

[bladesmith]

Wild Burro Audio Betsy 8" with bass help?

http://www.randallrash.com/New_Loudspeakers_part9.html

http://www.wildburroaudio.com/speakers.php

Like that set up...!

[sebrof]

If you are going to invest in a set of Heil AMT's and plan to cross that high, take a look at some of the LF Altec Lansing drivers reworked by Great Plains Audio. Your woofers will be reproducing some very critical fundamentals and you will want something that is very articulate to match the speed and clarity.  http://www.greatplainsaudio.com/woofers.html

That is exactly what I did. Altec 416s reworked by GPA.
I cross 1st order @ 1,000Hz 500Hz on the woofers, 3rd order @ 1,200Hz to the Heils.
Big cabinets ~10 cu/ft made of Baltic Birch plywood

Edit: Sorry, didn't realize this is the OB forum.

[bladesmith]

That is exactly what I did. Altec 416s reworked by GPA.
I cross 1st order @ 1,000Hz on the woofers, 3rd order @ 1,200Hz to the Heils.
Big cabinets ~10 cu/ft made of Baltic Birch plywood

Edit: Sorry, didn't realize this is the OB forum.

sebrof,

I have always wondered how your set up sounds. looks really interesting...!

[steve f]

Here is an application correction for using Heil AMT drivers. As Ed is banned, and I don't recall why, he contacted me via email.
 
Quote from Ed Schilling of the Horn Shoppe:

Hey Steve, I saw a post at AC by Horizons that is in error. Since I have been banned I can not correct it. The xover on the Horn/Heils is around ~4k not 1k. A 6 db slope @1K with a Heil will result in thermal runaway and melted diaphragms. At that freq. in order to have any semblance of power handling and low distortion at least 18db must be used. I could care less who believes this......but I hate to see my buddies melt a set of diaphragms due to misinformation. Now, if one listens to "little girls and guitars" at very low volumes it may be possible to avoid melt down BUT.....even then they can be damaged if played long enough at what most consider "normal volume".

I just would like to add that properly used, the Heil is an excellent driver. I have not found any of the newer AMT drivers to be in the same league

[bladesmith]

I've never tried these drivers/brand, but it almost looks like you could use one or two of these with a Heil AMT.

Crossover at 3.5k...not sure. But, the price is right.

http://www.mcmelectronics.com/product/MCM-AUDIO-SELECT-55-2981-/55-2981

[bladesmith]

You are going to need a mid bass coupler of some sort. There is going to be too big of a frequency hole between the Heil and the Alpha. Just for grins, take a look at Ed Schilling's Horns. He uses a Fostex for the mid bass. The AMT is series wired to the mid. I know this combo works well. All you would have to do is figure out where to bring in the Alphas. A starting point anyway.
[/quote

Where do I go to see Ed Shillings horns ?

[Horizons]

I appreciate Ed setting the record straight on his crossover frequency.

Just for fun, I tried Randy's approach on Hawthorne Audio with an OB with the Alpha and ATM with a 5 KHz, 6 db passive XO. I was stunned with how good this sounds, especially with the Alpha running that high. I was intending on going active around 1KHz/24 db but this passive first order approach sounds like live music.

My next question is whether or not to baffle mount the AMT or just stack on top like I am currently doing. That AMT is just an amazing driver.

[Squidspeak]

I, who has owned a pr. of the original ESS heil units for 30+ years and I'm still using them. I don't
buy Ed S. advise as to what they can handle as far as X-over points. I use them in a active/ triamp
system crossed at 1000hz/18db and have never melted them. Don't know where he is coming up
 with his numbers.

[sebrof]

I, who has owned a pr. of the original ESS heil units for 30+ years and I'm still using them. I don't
buy Ed S. advise as to what they can handle as far as X-over points. I use them in a active/ triamp
system crossed at 1000hz/18db and have never melted them. Don't know where he is coming up
 with his numbers.

The way I read Ed's information he is saying 1,000 Hz with 18db slope is fine, which is what you say you are using. So I think you and Ed agree, actually.

[bladesmith]

I believe the manufacturer, ESS, recommends a 1K crossover.

 (Heil AMT is licensed exclusively to ESS, not sure if it is made in house or not.)

I also believe they sell a set of two way speakers that they manufacturer, and they cross them at 1K. And I've not heard any issues from the owners of there manufactured speakers. 

[bladesmith]

I never stayed with my various OBs because I couldn't get the detail I wanted with compression drivers. However, I have been listening to Heil AMTs crossed over at 24 db/octave at 1 K and these are truly amazing dipole tweets.

So, I am thinking about an AMT based OB with either 2 15 Alphas crossed at 1K or two 12s. 12s might work better crossed that high. Any recs on a pair of 12s that give you that magic live OB sound and are clean to 1 kHz? I like and have used the Alphas but I already have two subs (ML sealed) and thinking that maybe there is something better to mate with the AMTs.

Or twin Betsy's??

TIA

I've researched this extensively.  Because it was something I wanted to try myself. The Alphas are perfect, qt's, OB, etc, etc,  but one thing I don't see right. Heil recommends an 8 ohm woofer in a two way set up. If you could get the same speaker (2, 15" Alphas) in 4 ohms, it would work great. In series. Or use just one 15" Alpha.

I wanted to do a WTW set up using the Heil AMT. But, can't find the right 12 or 15 inch, 4 ohm woofer that has the higher QT rating for an OB setup.

 

[Horizons]

For various reasons, I settled on the following for my latest OB experiment:

One Alpha 15A
One Dayton AMTPRO-4

Baffles are ~ 20" wide, 42 inches tall. They are tapered so they are ~12 inches wide at the top of the panel.
Currently using a simple coil/cap arrangement with the drivers rolling in/out around 4-5 KHz.

With this arrangement, I guess I just got lucky with the efficiency/xover points/slopes and the drivers match well with no need for padding down the AMT.

I can post pix if anyone is interested but so far, I am very impressed with how good these sound.  I am still using a sealed ML sub for < 50 Hz. Setting up a local listening panel soon to A/B these with Maggies, Logans, and a few other single driver setups. You really need to discount the pride factor when you build your own. But right now I would say that these are Maggie killers. All of the open and boxless sound of Maggies with much more bass, efficiency, depth, dynamics, and better and more extended highs.

I have also been trying to determine if the AMTPRO driver is as good as the great Heil AMT. I'm still not sure, but it is close.