The NHT Classic Four Surround Sound Speaker System Manufacturer's Comment

Manufacturer's comment

On behalf of everyone here at NHT, we appreciate Michael's review. Classic is turning into one of our biggest successes to date, thanks in no small part to the attention paid by journalists who recognize the system's extraordinary detail and imaging.

Regarding comments made about low-end output, NHT recommends a couple different options if users want to extend bass output or extension.

If listeners want more bass output or control, do what Michael did, bi-amplify the towers with the X2 crossover and two A1 power amplifiers. This will give them more control of the bass as well as more output capability by increasing the amplifier power available to drive the 10" subwoofers over that of what a typical receiver can supply.

However, if even more bass extension is desired, it is necessary to use a subwoofer with bass response below 20Hz and very high output capability. This subwoofer should be low-passed around 40-50Hz, with the Four high-passed around the same frequency. This will probably require an active crossover with phase adjustment such as the X2, since the adjustments found in most surround processors will not be adequate to properly integrate the Four with the subwoofer. Ideally, end-users should use an acoustic measurement device too, provided they know how to use it properly.

We don't recommend using the Classic Fours with an external subwoofer covering the same frequency range. At some frequencies, the output from the external subwoofer(s) will add to that of the Fours and at some frequencies it will cancel the output from the Fours. The results will be worse than having no external subwoofer at all.

Concerning the lateral dispersion of the Classic Three C center channel speaker, any speaker that has drivers covering the same frequency range, arrayed horizontally will have comb filtering (notches) in the frequency response of the horizontal dispersion. Typical woofer-tweeter-woofer center channel speakers have the crossover set to approximately 3kHz, in turn causing the large notch in the off axis response to be centered at 3kHz. This is the worst possible frequency to have this notch. It is the frequency that the ear has its highest sensitivity to because that is where the transients of consonants are located. It is the most important frequency range with regards to speech intelligibility. For this reason, we chose to put the crossover between the 6.5" woofers and the 2" at 800Hz. This allows the Three C to have very good horizontal dispersion above 1kHz, where it is most important for dialogue intelligibility. The Three C also includes a third foot on the back of the cabinet to aim it downwards to help pinpoint the image as necessary.

Once again, we are thrilled to be featured on Stay tuned for our next big announcement next month.


Jack Hidley

Director of Engineering