Q&A # 148 - November 17, 1999

Staff

Q I have a pair of Klipsch Heresey II speakers that I am thinking of using as the front speakers in a home theater system. Do you have any suggestions about what to use as a center speaker? I assume that one made by Klipsch would be a logical choice, but there seems to be an ever-changing series of models. Since none of the salespeople I have talked to have ever heard the Hereseys, I am taking their recommendations with a grain of salt. Do you have any suggestions (the KLF-C7 may be too large for the space)? I have a B&K Reference 20 and an AV5000, so power is not an issue. The Klipschs may not be a long term solution, but I would like to consider using them for the short term.

A Klipsch uses horns for at least one of the drivers, and that accounts, in part, for their high sensitivity. Even though you have plenty of power, it would be best to stick with horns so that the tonality matches with what you have. Klipsch has several center channel speakers, such as the RC-3 ($350), which will likely do the job.

Q I have just completed the installation of a five channel system. It consists primarily of Carver components. I've noticed a loud 60 Hz hum coming from the amplifier enclosure (Carver AV-405). It is a mechanical hum, not a ground loop through the speakers. Originally, I thought it was a defect in the amp. I pulled it and took it to the shop. The tech was unable to reproduce the hum. I then put a new Carver AV-705 in its place. That amp also produced an identical mechanical hum when wired into the original circuit. When I placed the 705 into another location, it worked just fine. The tech told me that he has seen instances where a poor electrical connection has produced such a mechanical hum. I'm at a loss to understand. Any idea what the problem (and fix) might be?

A Noisy AC lines are probably the culprit. If you have a solid state light control in the room, try turning it off and see if that helps. I have found that the amount of hum changes when the light control is adjusted to different settings. Other noise sources in your AC lines could also be causing it, but since you didn't get the hum when you put the amplifier in a different location (room), it is probably something that is connected to the same line in your home theater room. Try unplugging or turning off other things in the room, including any fluorescent lights, one at a time to see what is causing it.

Q I would like for you to evaluate my home system for me. I use it for 80% music and 20% HT. The TV is a Sony PVM2030 27" monitor, DVD is Sony S330, CD player Sony CDP-C77es, Tuner Sony St-550ES, Preamp Sony TA-E1000ESD, Center Amp Sony TA-N220, Front Amp Sony TA-N55ES, Rear & Second front amp Sony TA-N55ES, center speakers Tannoy Chevoit 12", front speakers Tannoy Arundel 15", rear speakers Vega Linear (which is a 15" Tannoy driver). I will be able to go to the 2000es preamp once my brother installs his 9000es preamp in his system. Since I use the system mostly for music, I just switch my one amp to rear channel pre-outs when needed. I like the sound that I get but just wanted a professional opinion on the matter.

A The only thing I can suggest is a good subwoofer. Even though you have large speakers, a subwoofer will do a better job at the lowest octave (20 Hz - 40 Hz).

Q I am considering a pair of Boston Acoustic VR970 speakers. I would like your comment on a comparison of these speakers to Mirage OM10, Klipsch, and Definitive speakers. Your advice would be greatly appreciated.

A Mirage and Definite Technology specialize in bipolar, with some models having powered subs built-into the enclosure. The Klipsch are horn speakers, which have a distinct sound of their own, much different than the others. The Boston Acoustic will be a third type of sound. It depends on what you will be using them for, and where they will be located. The bipolar speakers will do best somewhat out from the wall. Klipsch, being quite sensitive, are good for low powered receivers.

Q If I have my TV in the corner, where should I put the rear surround speakers?

A I would suggest trying them on the rear walls, placed a couple of feet from the junction with the front walls. If that does not work, then perhaps a foot or two to the side of your couch, pointed somewhere around the midway point between your couch and the TV. Those are just starting ideas. There are really no rules. Move them around and see what sounds best. That is part of the fun.

Q I own a Yamaha 2095 with NHT 1.5s up front, AC-1 in the center, Superones in the rear, and a Sunfire MKII subwoofer. I have a question about bass management and speaker settings. My system is used for both home theater and for music. What are the relatively advantages/disadvantages in setting speakers up as "large" or "small", and the bass routed through the subwoofer only or both the speakers and subwoofer? If the main speakers are set to "small" and the bass is set to "both" (speakers and subwoofer), what exactly is happening to the bass? Does freeing the main speakers from handling bass make them "better" when listening to music?

A The problem with current bass management technology is that the crossover is too high. I recently set up a friend's home theater with a Yamaha 2095 and bookshelf speakers. Even though the speakers are not very big, setting them to "Small" in the bass management menu resulted in their sounding too thin. So, I set them to "Large". For Pro Logic, the subwoofer was not getting much signal, so I set the subwoofer menu in the 2095 to deliver bass to both the main speakers and the subwoofer. This improved the bass out to the sub when using Pro Logic. So, I would suggest setting your main speakers to "Large", which will give you a fuller sound up front, and good bass to the sub when using Pro Logic. For DD and DTS, the bass out to the sub is not so much of a problem with bass management settings. Even your Superones in the rear will probably sound better being set to "Large". The only situation where I would set speakers to "Small" with mass market receivers is when using those really small modular speakers, which don't produce much sound below 100 Hz. Once the receiver manufacturers come up with digital bass management that has selectable crossover frequencies in the 40 Hz - 80 Hz regions, then the "Small" setting will be more useful, and more appropriate. At that point, routing all < 40 Hz signals to a good sub would substantially improve a receiver amplifier's performance. Everything below about 50 Hz is non-directional.

Q Hi, I am a Sixth-Former studying physics at Bristol Grammar School in the UK. I am currently doing a project on stereo AM radio, and I was wondering if you have any information about how the signal is coded with Amplitude Modulation, or if you would be able to point me in the direction of a technical article or something.

A Check out http://www.cpiradio.com/crlamrpt.htm. 

Q I have a three year old 60" Ultravision with no component inputs but has one S-Video input on the rear (and one on the front). I have a DD DSS and a DVD with DD/DTS. I have a Yamaha DD/DTS receiver with an S-Video input and S-Video Monitor output, as well as a VHS S-Video in and out. What are your recommendations on the video hookups? Also, do I need to bypass my crossover in my sub when listening/viewing in DD or DTS?

A Since you are fortunate enough to have two S-Video jacks, connect the S-Video output from the DSS receiver to one of the TV's S-Video inputs and the S-Video output from your DVD player to the other TV S-Video input. Bypassing the S-Video jacks and switches in your receiver will give you the best picture. No matter how good the jacks and switches are, there is always some signal loss. Bypassing the sub's crossover is OK for when using some DD and DTS with the LFE output, since the frequencies are controlled. However, depending on what is sent through the LFE, you could end up with too much bass in the regions that your main speakers reproduce. So, you just have to try the various scenarios out. Personally, I have always preferred using the crossover in the subwoofer, regardless of any crossover in front of it. I like to have control over the exact low-pass cutoff.

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