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S_rangeBrew
01-18-2006, 11:46 AM
Do HTM-200s come close to THX specs?

I found this here (http://www.hometheaterhifi.com/volume_13_1/feature-article-thx-1-2006-part-3.html) :


The THX crossover consists of an 80 Hz, 4th order Linkwitz/Riley filter alignment, and it was not chosen lightly or without serious consideration. As the crossover frequency increases, it becomes harder to blend the subwoofer with a satellite, and the subwoofer becomes more difficult to audibly "hide". At the same time, as the crossover frequency increases, distortion from the satellite decreases, the total dynamic range increases, and loading the room for the flattest response becomes much easier. The logic of the 80 Hz crossover point is that it's high enough to ease demands on the speakers and amplifier, but low enough to make the whole setup work without a tremendous headache. The 4th order (24dB/octave roll-off, 6dB/octave/pole) Linkwitz/Riley alignment not only offers a steep slope, but one that immediately transitions to that slope, maximizing the benefits of that slope near the crossover point. The high-pass side minimizes excursion and power requirements, while the low-pass minimizes more localizable content at higher frequencies.

To correctly achieve this, THX satellite speakers are sealed systems with an 80 Hz –3 dB low frequency cutoff (preferably with a Qtc of 0.71). The electronic high-pass filter applied to them is an 80 Hz, 2nd order (12dB/octave) Butterworth alignment. The speaker and the filter sum to a 4th order Linkwitz/Riley roll-off which matches the electronic filter applied to the subwoofer, and an excellent crossover is achieved.

I thought this sounded a lot like a HTM-200, and was wondering if that was really the case?

GaryB
01-18-2006, 03:24 PM
The HTM-200 response is actually pretty close to THX specs. IIRC, from information Dave F. sent me last year, the -3dB point for these speakers typically falls between 80 & 85 Hz, with a Qtc ~0.9. The slightly underdamped Q gives them a little added "warmth" just above the LF roll-off, which is certainly not excessive, as anyone who has heard these speakers can attest.