The MTS-01 speakers have a sensitivity of 86.5 dB with a 2.83V input @ 1M in full space.
"Nominal impedance" can be interpreted in different ways, so we prefer to provide the actual Z-curve upon request (we've already provided it to captainkirk28). The MTS-01 nominal impedance will typically be interpreted as ~4 ohms by most loudspeaker designers. With that said, the electrical phase response is quite benign, and the speakers can be driven easily by any amp rated for 4-6 ohm loads. In fact, we've driven them with most popular brands of consumer AVR (which are typically rated for 6 ohms or higher) without difficulty.
We can provide all the specs and measurement data on our M-series speakers; just email us at Sales or Tech Support. Deciding what to display on the website is a balancing act falling somewhere between sufficient and TMI, but we can/will provide all the data to anyone who asks.
The original crossover design was not sufficiently protective of the tweeter. While I can count the total number of tweeter failures in the field on two hands (with thousands of units in the field), captainkirk28 was indeed responsible for the majority of them. Regardless, we decided to re-work the XO networks in the M-series speakers to be more protective of the tweeter. We also improved the acoustic phase response, frequency response, bass extension, and voicing in the process.
The reworked tweeter high pass is a Linkwitz-Riley 24 dB/octave at 1.85 kHz, and the tweeter response is over -20 dB @ 1 kHz relative to the average response level in the 2-5 kHz region. This is easily sufficiently protective of the tweeter in all applications unless the amplifier is being driven into clipping (which no tweeter will survive for long). cpatainkirk28 has the dubious distinction of being our only customer to blow a ScanSpeak D3004 tweeter with the new crossovers installed. That is exactly one (1) tweeter failure with the new XOs with thousands of D3004 AirCirc tweets in the field.
We suspected he was overdriving his Pioneer AVR, given his preference for up-converting 2 channel source material to 5/7 channels. This type of playback condition is very demanding on the AVR amp stage, and that - combined with the relatively low sensitivity and impedance of the M-series speakers - was a recipe for problems. We therefore encouraged captainkirk28 to purchase an external amp capable of driving 4 ohm loads and his choice of the Emotiva XPA-3 is a good one.
His XPA-3 went up in smoke within 15 minutes of being connected. The infant mortality rate of modern solid-state amps is low - but it does happen; he wouldn't be the first owner to watch a new amp go up in smoke. Nearly all modern amps have relays and/or fuses to protect against a dead-short or an otherwise dangerous load. Self destruction is not an acceptable means of informing the owner the connected load is unsafe. His amp was defective out of the box; I'm confident our speakers did not blow his amp.
If his M-series speakers were truly presenting such a load, his Pioneer AVR (which by all accounts has a far less robust amp stage than the Emotiva) would have long ago immediately gone into protect mode and refused to operate, and that simply hasn't been the case - he's been driving the speakers with his Pioneer AVR for months.
I've asked captainkirk28 to connect other speakers (he has some B&W and Pioneer units available) to his replacement Emotiva when it arrives - just to isolate the M-series speakers as a variable. If the amp survives a day or two without blowing up, he can connect our speakers without worry.
The only absolutes in life are death and taxes, and anything is possible, no matter how remote the odds. So in the extremely unlikely event his M-series speakers do fry the Emotiva after it has been broken in with other speakers, I've pledged to return them to the factory for inspection/measurement and refund his full purchase without question.
Ed Mullen
Product Development and Customer Service
SV Sound