Heil AMT resurrection

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With ESS beginning to produce Heil AMTs again and Parts Express selling them I decided to resurrect an old pair of speakers I built years ago to be the basis of an article I plan to write for "AudioXpress". They have original Heil AMTs for the top, Eton 7" Hexacones for the mid and currently HSU 12" woofers.

The Heils and Etons are excellent if you use them properly. Both are great within a certain range but get very nasty if you get too far out of their prime bandwidths. Using an electronic crossover with LR 48 dB/octave slopes fills the bill.

The HSUs are good drivers, but PE has a new 12" driver that looks very interesting. It is called the Ultimax DVC and has some very interesting specs. the Xmax is 19 mm which is very good for a reasonably priced 12". The two voice coils are 2 ohms each so you can get 1, 2, or 4 ohm impedances. They have lots of other design goodies which can be found on the PE website. I have a pair on order and hope to get them soon.

Electronics I'm using for test include a Sony DVP-NS500V SACD player, an NAD 1300 pre-amp (this is the discrete old version that is quite good), a Behringer DEQ2496 digital equalizer, a Behringer DCX2496 digital crossover, a modified QSC USA1300 amp for the lows, a modified Hafler DH500 amp for the mids and a Parasound HCA 800II for the top.

I have started voicing the system using the HSUs and after a lot of work the results are very promising. The sound stage is exceptionally deep, the transient response is excellent, and the detail is great while not being etched. The bass is good but limited in performance compared to the mids and highs. Crossover points are 200 Hz and 1 KHz. The 1KHZ is no problem for the AMT with the 48dB/octave crossover slope. I'll continue the voicing when the new woofers arrive. Photos are enclosed.

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The woofers arrived today from Parts Express. Here are some photos of them and the HSU woorers they will replace.

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UM12-22 cone with Nomex honeycomb and fiber glass

Tinsel leads as part of the spider to reduce chance of breakage at high excursions

Side view showing heavy duty terminals. Note "Tall-boy" surround

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Woofer photos 2

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Bottom view

Top cone intermediate fastening to voice coil

Under spider vents

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HSU photos

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HSU top view

Side view showing flocked paper cone

Terminals and free floating tinsel leads

[KLH007]

Tom, What a cool project. The new PE woofers look killer. I look forward to getting a chance to hear them after you have voiced the new woofers into the system.
Regards,
Kemper

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The voicing is going faster than expected. This should be finished in a short time. Here is what it looks like now.

Complete speaker showing drivers

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Complete speaker with grille