2-Way Speaker Project AMT and Watkins Woofer
I want to rebuild/reverse engineer an AMT 1C 2-way system, but wanted to add something different to improve the low end performance of the speaker. I was wondering if you have any ideas/experience employing a Watkins woofer into a non-Infinity system.
The plan to date: purchase AMTs from ESS and 12" Watkins Drivers from William Watkins. Design the high pass for the AMT, the low passes for each coil of the Watkins drivers, and the servo to control the pair. I haven't purchased anything yet, just wasting paper and pencil lead. Any advice, warnings, "been there done that" feedback is welcome
I have a pair of Infinity Epsilons.
I can tell you that the Watkins woofer system has some of the best bass that I've heard.
Simply phenomenal! Very fast and deep.
Infinity's implementation of the servo controller is a bit tricky, but seems to work well. They used an accelerometer on the cone like Velodyne.
Project definitely worth doing!
After doing a bit of reading I have a couple questions regarding Watkins woofers. First, the SPL of Infinity systems is around 85dB. Does the tuned circuit used to extend the lower bandwidth of the woofer cause this low effeciency?
Second, low-pass crossover frequencies for Infinity speaker systems are at around 100Hz (IRSV 60-110Hz, Epsilon 160Hz, Gamma 100Hz, and Sigma 160Hz). These frequencies are quite low and may be too low to pair with an AMT. What is the bandwidth of the Watkins driver? Can a 12" Watkins driver be crossed over at 2500Hz?
I’ve been trying to find Thiele\Small characteristics for the Watkins Woofer. The chief source I’ve found is a German Infinity page loaded with Infinity speaker specs and crossover diagrams. Looking over how the Watkins Woofer was used I believe the 12 inch driver alone with an AMT may be a less than ideal 2-way combination. Infinity typically limited their use of the Watkins Woofer to between 160 and 200 HZ. I recently purchased a pair of Watkins Woofers so when I can I’ll do some testing to try and identify the speaker’s bandwidth and also build a list of Thiele Small characteristics. Since I want to build a system that employs both the Watkins Woofer and ESS’s Air Motion Transformer, I’m changing the design to a 3-way system
Even though I wanted to improve the ESS 1C, the characteristics of the drivers I’ve chosen are forcing a three way design. Here are the low and high pass points so far: the current low-pass design for the Watkins Woofer to 200 Hz, the high pass for the AMT will be at 2000Hz. Now I need a mid-bass speaker to close the gap between the two drivers. ScanSpeak has a 4” midrange (Illuminator)that is flat at both of these points, so I’m considering this driver as the midrange for my now three-way system.
The next stage is the crossover design. I’ve looked at a few crossover design tools and have been playing with the results. My current concern is not the band pass stage for the midrange, but the low pass combined with the tuned circuit used on the 4 ohm voice coil of the Watkins. Another concern is using a Zobel to stabilize of impedance of the Watkins. Since the tuned circuits for the two voice coils turn the coils on and off around resonance what would be the impact of add the Zobel to the 4 ohm voice coil?
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