Q&A # 229 - May 6, 2001

Staff

Q I have read a lot of answers in your web site regarding bi-amping, but I still have some reservations. I have a Denon Dolby Digital receiver (85 watts x 5) along with a Rotel RMB-1095 amplifier (200 watts x 5). I am using the Denon as a preamp/processor. In the past, you have recommended to other readers that they bi-amp their speakers using their receivers' built-in amp to power the tweeter/midrange speaker drivers, and the outboard amplifier to power the woofers. However, the Rotel amp does not have level adjustments. The gain of an outboard amp, such as the Rotel, can be quite different than the gain of another amp, such as the one built into the Denon. Therefore, how can I be assured that the relative loudness of the two different amps are the same when bi-amping? Would I need to purchase some sort of level control to put between the pre-outs of the receiver and the input of the outboard amplifier? If so, what sort of device would I get? Given that I can get or make such a device, how would the relative levels/gains between the receiver's built-in amp and the outboard amp be balanced? Would a test-CD along with Radio Shack's sound level meter be used to balance the gains?

One last question: I am considering upgrading to a separate preamp in the future. However, it seems that the latest and greatest features, such as THX Surround EX, DTS 6.1 discrete, component switching, etc., are much more likely to be in receivers than in preamps.  Yes, the very very high priced preamps tend to have the latest features, but lower priced preamps (such as in the $1000 to $2500 range) tend not to have the latest and greatest features yet. On the other hand, even lower priced receivers (such as the Denon 3801 receiver) have the latest features. Why are the latest features harder to find in lower priced preamps than in lower priced receivers?

A The recommendation to use the receiver's built-in amps along with an outboard amplifier for bi-amping is mainly for those consumers whose outboard amplifier is not very large. In the case of the RMB-1095, it is so powerful, you are unlikely to need to bi-amp. Just use the pre-outs of your receiver to the 1095 and don't use the receiver's amplifiers. For using both amplifiers, the sensitivity of the outboard amplifier does indeed need to be considered. Using a test CD with sine waves at various frequencies, along with a Radio Shack SPL meter, will aid you in the balancing task. It may very well turn out that no external volume control is needed. But, if you do need one, a simple potentiometer of around 10 kOhms will probably suffice for testing. I would get an inexpensive one, then put it in line with the pre-out to outboard power amplifier, balance the sound, then measure the DC resistance at the setting on the potentiometer where the sound is balanced. Then, I would purchase a good quality fixed 1% tolerance resistor of that value and solder it in line with the cable from the pre-out to the power amp channel input.

Mass market receivers sell a lot more product than preamp/processors, so that is where the manufacturers put their first effort. However, new processor designs are taking into account the ever-changing format picture, and have input jacks for loading new software as it becomes available. Even some new receivers have these jacks, and that is one feature I would suggest looking for if you buy a high priced receiver or processor.

Q I currently own a Yamaha DSP-A-2070, Bose 901 speakers (main), Jamo 100 center speaker (center), Bose AM5 speakers (using as surround speakers), and a Wega Sony 36" TV. I am in the market for a DVD player. I would prefer a 5 disc (maybe the Sony DVP-C670D?) player, but would consider other options. I would like DTS and DD decoding. Within the range of $750, do you have any suggestions on how to complete my Home theater setup?

A Although single-disc players are more prevalent, there are a number of multi-disc players. Since you already have a Yamaha receiver, the Yamaha DVD-C996 might be a good choice. There are also the Denon DVM-3700, Panasonic DVD-CV51, Marantz VC-8100, and Toshiba SD-4205.

Q I have a four year old 35" Sony Trinitron KV-35V36 with S-Video inputs. I am currently using the first generation Panasonic A100 DVD player with S-Video connection to my TV. I think the picture is fantastic. My question is, is it worthwhile to invest $800 for a progressive scan DVD player for the setup that I have? Will my picture quality be about the same or will it improve dramatically? Do I need a progressive scan TV to see an improved picture?

A We get this question a lot, and it is worth re-iterating. In order to use the progressive scan output from a DVD player that has that capability, you need a TV with component video inputs and progressive scan capability. Some DVD players with component video outputs don't have progressive scan. They just have interlaced component video. More and more players coming out lately have both component video and progressive scan, even one that is just over $200. There is a huge difference with progressive scan, and it appears to work best when the player outputs the component video in progressive, rather than sending interlaced component video to the TV and letting the TV convert it to progressive. The point is that you won't have to spend $800 to get a component video-progressive scan DVD player, but wait until we have tested the newest crop of players in our Benchmark before getting one of them.

Q I have a Kenwood KR-V8030 Pro Logic receiver. I am not ready to buy a new digital receiver yet, but I would like to purchase a new set of speakers. I am looking at a theatre set with a powered subwoofer.  There is no subwoofer connection on my receiver. Do powered subwoofers have a crossover built in that filters out the low frequencies and high frequencies? Would I be able to hook up the satellite speakers through the subwoofer?

A Just about every subwoofer out there has two types of inputs. One is the line-level which is for use with the subwoofer output jacks on receivers. It is a preamplifier output. The second type is a speaker-level input, and is connected to the speaker outputs of your receiver. There are usually a left and right input so that you can connect the left and right channel speaker outputs. Then, there are line-level and speaker-level outputs on the subwoofer, so that you can connect your satellite speakers. If you use the line-level out from the subwoofer, you need to send it to another power amplifier before going to the speaker. The speaker-level outputs from the subwoofer can go directly to your satellite speakers. These outputs are filtered, usually so that everything above, say, 90 Hz, goes to your satellite speakers. The low pass frequency on the subwoofer is adjustable, but the high pass out to your satellites is not. So, if you use the high pass out to your satellites, you should set the low pass at about the same frequency as the high pass. Check your subwoofer instruction manual to see what the high pass frequency is.

Q I have read time and again that movie mixers set up the audio track with an array of speakers in the rear in mind, and I wish to recreate this. I was planning on two 8 ohm speakers in parallel and in series with another pair of 8 ohm speakers in parallel, for each rear channel. The math works out for an 8 ohm load, but I was wondering if the sound quality would degrade or the volume would drop because of the voltage divider.

A The volume from each speaker might be less than if you just used one speaker, but the total volume will probably be similar, with the same voltage and current. It sounds like you will have eight speakers across the back. Let us know how it turns out.

Q I have been searching fruitlessly for any information about S-VHS VCRs. I would like to buy one, but I have absolutely no idea what the differences are between any of them. I would be using it as my movie watching and tape recording machine, as well as transferring video from my computer to tape. I use a Canon Mini-DV camcorder, so a quality picture is important..

A There are several nice S-VHS VCRs out there, but it is yesterday's technology. Especially since you are using Mini-DV, I would suggest transferring all your DV to computer, editing it with a non-linear video editing software such as Adobe Premiere or ULead Photo Impact Media Studio Pro. Then, using a good video card, output it as S-Video or component video to your TV. We will cover this technology shortly as part of our PC-Home Theater series (John Kotches is our PC- Home Theater Editor). Video tape is not the best way to go. Hard drive recording is the newest way to do this.

Q My Philips DVD725 player does not have a built in DTS/DD decoder, but has a digital out (coax or optical) for DTS/DD/PCM. Meanwhile, my receiver does not have DTS/DD decoder either, but it has a 5.1 input. So, I am looking for a separate DTS/DD decoder that I can attach to the system, hopefully a not too expensive one but can fulfill the gap for DTS/DD listening enjoyment. I found the only product that is available in the market is the Panasonic DTS/DD decoder SH-AC500D. Are there any new similar products in the market? What do you suggest for my situation? Buy a new DVD player with built in DTS/DD decoders?

A Just about every receiver released in the last year or so has DD and DTS decoding built-in, so outboard decoders have all but disappeared from the market. There are several options. (1) Get the Panasonic decoder; (2) Go onto one of the home theater newsgroups and post a WTB (Wanted to Buy) message about your needs for an outboard decoder (someone might have a used one for sale); (3) Buy a new receiver; and (4) Buy a new DVD player with 5.1 analog out. The used outboard decoder route would be the least expensive.

Q I have a Sony ES-333 receiver that functions in either 4 or 8 Ohms. My system setup (All Cerwin Vega), consists of two floor-standing speakers for fronts, one center channel, and two bookshelf speakers for the rears. The floor-standing speakers are 4 Ohms speakers. The remaining three speakers are 8 Ohms speakers. I currently have the receiver set to 4 Ohms. Should I be  concerned that the fronts are not matched to 8 Ohms like the rest? Is there a risk of damage to the speakers, receiver, etc? Just wondering if it would be worth the investment to purchase new floor-standing speakers that are 8 Ohms.

A What I would do is set the receiver to 8 Ohms, then adjust your center and rear channels to about 6 dB higher (using the speaker menu in your receiver) than the mains. This should compensate for any loudness differences. With any receiver, though, whether you are using 8 Ohm or 4 Ohm speakers, use the volume control judiciously. Mass market receivers are just not made to blow out the windows with loudness. They will clip hard at high volume, regardless of the speakers.

� Copyright 2001 Secrets of Home Theater & High Fidelity
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