Best Xover Point for AMT in 3way

[Thatch_Ear]

I have an Altec 416 and a few pair of the large dipole Heil AMTs from the 70s with original diaphragms. I just don't get the dynamics I want in the lower mid area no matter where I cross at. If I was only going to listen to one type of music at one volume things would be easy. In fact if I only listened by myself I wouldn't have much of a problem. AMTs seem to need a bit of loading that I can't always do and if I turn it off I am petty.
So especially at lower volumes I have no dynamics. To fix this I am going to try an open baffle with a pair of the 8" alnico drivers that I have in a pair of Ampex Suitcases. Supposedly made by JBL. Doesn't matter.
To keep from messing around too much I would like some advice on where to cross from the 8" to the AMTs. I have never built 3ways and don't know if there is any area I should avoid crossing in.

Thank You,
Thatch

 

[Keith Taylor]

Are you planning to implement the crossover function by passive or active means? Something to consider besides the XO frequency is the filter order. Fourth order filters are probably best realised by active means.

As for the frequency, 1kHz is an often mentioned figure for Heil AMT's. Some suggest that having crossovers in the "speech" band is not a good idea. This view is probably a bit simplistic; maybe more a case of avoiding group delay errors in the part of the spectrum that contains the vowel and other formants.

That said, Linkwitz's LX521 dipole design has a 1kHz second order XO in its latest version. Something that I have not heard any complaints about.

If you are interested in things the human auditory system has a low tolerance of there is some interesting reading on David Griesinger's web site. He opines that the Basilar membrane is a part of our hearing that is not easily fooled.

Keith

 

[Thatch_Ear]

1K or even 800 Hz are used for AMTs in 2 ways. That is exactly what I was doing with an active cross. I didn't care for the way the active cross sounded and sent it back. I didn't care for the way the drivers sounded either. The AMT is great for vocals or a stringed instrument, but often there was an extreme lack of dynamics in the lower ranges of the AMT. That is why I am going to put in the 8" OB. I need a bit of punch if the music is punchy. I just want a bit of guidance that is more than my thinking that I really need it from 1K to 5K. Reading is great and I will check David Griesinger out. Thank You.
A does and don't s of speaker crossover type of paper would be very helpful.

Thatch

 

[Thatch_Ear]

I know there isn't enough information here to give any kind of an exact answer and I am not looking for one. I know that I am crossing high at 1K for the 416, but that isn't written in stone. But I can't just throw crossover parts at this either.
I guess I am looking more for a list of Hz that are problems if you cross at that point. Maybe I should pop over to the full range forum and find out if anybody has used the Ampex 8" and if there are any peaks or valleys there that are already a good start to a slope.

Thatch

 

[rb132333]

I have a pair of the Heil AMTs in an active set up and I cross them around 2.3K. I am crossing to dbl 5" VWR126s. If I were you I would try somewhere around 1.7K or so where the 8" starts to beam.