Q Do I need cables that are THX certified?

A THX certification on cables is rare, so you would be very limited in selection. There are plenty of superb cables out there that are not THX certified, and which you might very well like the sound of, more than the few that are certified. THX certification for cables ensures that for a certain length, they are a specific gauge.

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Q I currently own a Boston Acoustics-Micro System 9500 for Home Theater, using a Yamaha RX-V620 Receiver. The BA's Sub is powered at 300 watts with a 12" down firing cone. However, there is no adjustable crossover setting with this sub (which is identical to the BA PV800--that does have an adjustable x-over). My understanding is that the sub already has an internal x-over that has been factory set, adjusted according to the specs of its speakers. With this factory limitation, it leads me to my point: How do I adjust the sub level using my SPL meter?

A The low-pass is set to 150 Hz due to the small size of the satellites. Because everything over 50 Hz is localizable, I would suggest putting your sub near the center channel speaker, since voices come from the center. Simply adjust the volume until it sounds "right" (no boominess).

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Q For receivers with video switching, how many MHz are enough to pass a high definition video signal? For example, the Onkyo TX-SR600 is listed as having "HDTV Capable (60 MHz) Component Video Switching". On the other hand, Denon lists its new AVR-1803 as having "Component Video Inputs (27 MHz), compatible with progressive DVD, DTV". To make it even more confusing, Denon's high-end AVR-5803 (out of my price range) is featured with "Component  Video Inputs, compatible with wideband (480p, 720p, 1080i) response for progressive DVD, DTV (100 MHz)." At this point, I'm really confused as to how much bandwidth is necessary to pass progressive DVD and HDTV signals. Can you shed any insight?

A The video response is usually listed at - 3 dB, so I would be looking for a specified response to 150 MHz or higher. It really needs to be flat to 100 MHz. The switching circuitry also must be 75 Ohms all the way through, must not delay one color channel over another, and must not inject noise.

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Q After auditioning lots of speakers, I have finally firmed up on the M&K LCR-750 THX package. Then, to my dismay, I found out that the nominal impedance is 4 Ohms. I have seen that most of the AV Receivers have their specified impedance between 6 Ohms and 8 Ohms. Under these circumstances, I would like to know if I can connect these 4 Ohm loads to AV Receivers like Denon AV 3802, HK etc?

A You can connect them, but if the receiver has a switch to select 4 or 8 Ohms, select 4 Ohms. If it does not have the selector switch, just be careful with the volume control. If the receiver starts to get hot, turn it down.

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Q Do balanced inputs always improve the signal to noise ratio, even if the amplifier does not have balanced circuits,  due to the effect on the noise in the cables?

A No, they are not always the best solution. As you will see in our recent reviews, sometimes the RCA unbalanced connection is the best way to go, when it is on an unbalanced circuit. But this all depends on what else is in the system. If I had a fully balance preamp, I would use the balanced input on the unbalanced amplifier. Or, if I were using very, very long cables, I would use the balanced input.

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Q  I noticed my DVD player has an option to compress the audio for listening to at low volumes. I have two questions about this. 1. Will this degrade the quality at all, and what exactly does this do for you? 2. My surround sound receiver also has the same thing, so if I where to use it, should I use it on my DVD player or receiver, or can I put it on on both? Also the receiver has three settings, low, medium, and high. Which is the best to use?

A They do the same thing on the player and receiver, and what it does is reduce the dynamic range, so that voices can be heard easily, but explosions are not very loud. This lets you watch movies at night and not disturb other people who might be asleep. Implement the compression mode on the receiver, rather than on the player. Keep in mind that the compression option in the player is only for the analog output. With the receiver, it is only with the digital input. Experiment with the three levels of compression to see which level you like the most. One might bring the low volume up, the second might bring the high volume down, and the third might do both. You should read Brian Florian's article on Dialog Normalization too.

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Q  Have you ever thought about measuring the actual efficiency of the speakers you review? A fully calibrated chain, from mic to mic preamp to sound card, can be had for a few hundred dollars, and could take frequency response measurements, too (good FR measurements require some practice, however). You have gained a great reputation for
your hard-core-numbers reviews of DVD players. It would be nice to see this carry over into your speaker reviews, especially since your reviews are rarely matched in quality by other publications.

A As you have seen from recent reviews, we do measure some parameters on speakers, including frequency response and distortion. At some point, we will expand to include impedance measurements and efficiency. Impedance is straightforward, but efficiency will be tricky because the room has a definite effect, and every room is different. We don't have an anechoic chamber, and although MLS techniques are fine for frequency response (MLS eliminates the effect of the room response), the techniques for efficiency testing are different.

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Q My main speakers (Paradigm Monitor 9s) respond down to 33 Hz. Does that mean I don't need a subwoofer?

A The response at 33 Hz is likely to be at least 3 dB down from the rest of the response, possibly more, depending on your room and placement. Therefore, it would still be advisable to get a good subwoofer, perhaps a 15" or 18" that will respond all the way down to 20 Hz. You might end up setting the low-pass on the subwoofer to 40 Hz.

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