Q&A # 186 - June 30, 2000

Staff

Q I just read Q&A 185, and I think you misinterpreted the first question dealing with using car speakers in a home setting. I've been into car audio for 15 years, so I feel somewhat qualified to add my $0.02. I've used home speakers in the car and car speakers in the home, and either scenario can sound ok if done correctly. It sounds like that reader was thinking of building a sub for home theater using "mobile' subwoofers. As long as s/he built the enclosure according to the speaker parameters, it'd work fine. For use with home amps, the subs could be wired in series (or an 8 ohm version could be used). One of the benefits of car subs is that they're usually designed for small enclosures, so making a dual 15" sub enclosure almost might be practical (almost ;-). On the down side, car speakers are heavier duty, so the audiophile performance might suffer, and they require quite a bit of power (>300W). You were absolutely correct with your advice on amps. Back in high school, my nutty friends and I wasted many dollars on flea market amps that put out "1000W". As we got older and wiser, we started reading the fine print (which some flea market amps don't even have). 1000W @ 14.4 VDC, bridged into 2 ohms, 1 kHz, <10% THD. 10% THD!! Great. And we were wondering how they could sell a 1000W amp for $150. By the way, these shady amps had shady brand names to match, such as "Demon", made to look just like the "Denon" logo; "Deltasonic", with a logo suspiciously similar to "Alphasonik"; and "Hitronics", complete with amps named after various Greek/Roman deities. If that reader was thinking of using the car amp for home theater, s/he should forget about it. I've seen first hand this type of system and it just plain sucks. The cost and hassle of getting 12VDC at 50+ amps from your home AC is already reason to abort the mission. You could get a 100Wx5 receiver for less than the price of a decent car amp.

A You are right. I did misinterpret the question. When I look at the question now, I don't know how that happened. A combination of being a geezer and having too many questions to answer I guess. Anyway, thanks for the input. Consumers can buy inexpensive drivers ($20) that are made for the home rather than the car, but as to amplifiers, your comment about the ones for cars being very expensive compared to home amplifiers is absolutely correct. You pay quite a bit extra for the compact design in the car. It is a much better idea just to get a home audio amplifier for use in driving the subwoofer. One possibility might be the amplifier I used with the ButtKicker, reviewed a few months ago. It is the Carvin DCM2000 (2000 watts rms into 4 Ohms bridged), that sells for $620 direct from Carvin. I know 2000 watts sounds like a lot, but low frequencies eat it up fast. I was clipping that amplifier when driving the ButtKicker (4 Ohm load) with < 20 Hz signals.

Q I am using a subwoofer that doesn't have a phase switch. Is it really necessary and how can "phase shift" affect the bass response of subwoofer? Another question is about my amplifier. Do I need to buy a new kind amplifier, with the emergence of these high- resolution, high-bit and high- bandwith formats (SACD, DVD-Audio,etc.)? Lastly, could a 120w rated speaker be damaged by a 500w monoblock amp?

A Phase switches are a useful feature but are not absolutely necessary. Because your subwoofer has to be in a different location than the other speakers that it serves, the timing for the arrival of the sound from the sub is different than from the other speakers. This changes the phase relationships of the low frequencies from the subwoofer with respect to the mids and highs from the main speakers. So, you can adjust the sub phase with that switch. However, because the subwoofer uses a crossover - maybe even two crossovers if you include the one that is before the subwoofer output jack on your receiver - you can adjust the phase of only one frequency. The frequencies above and below that adjusted frequency will still have phase shift. Fortunately, phase shift in the really low frequencies that subwoofers handle is not very noticeable.

You don't need a new amplifier to handle SACD or DVD-Audio, but you will need a new player that has the proper DACs (Digital-to-Analog Converters). Your existing amplifier will only see the analog signal coming out of the player after it has been converted. As far as the amplifier is concerned, the signal is the same as it has always been. As long as your receiver has a set of 5.1 analog input jacks, you won't even need a new one (receiver), because the first DVD-Audio players will have 5.1 analog outputs.

Your 120 watt speaker will love your 500 watt amplifier. When you are listening to some dynamic music at normal levels, and a peak comes along, your amplifier will deliver a clean signal rather than a clipped one. Speakers hate clipping. If you turn it up so that you were using 150 watts continuously, yes, it would probably blow the drivers, but it would also be painful to listen at that level, so I doubt you would do that. As I have mentioned many times before, but it is worthwhile repeating again and again, the danger is not in having too much power, but rather, in not having enough.

Q I really need your help here. I have purchased the Martin Logan ReQuest with which I am very happy. I am driving them with a pair of Bryston 7B monoblocks. Recently, I converted my front end to tube electronics. I have purchased Sonic Frontiers Transport 3/Processor 3/ and Preamp Line 3. I am now a believer in tube electronics to the point that I want to use tube amps. This brings me to my question. What would you recommend for tube amps that would match well with the ReQuest? My room is 16 x 12 x 9 ft. I like to listen to Jazz music reasonably loud or at more realistic level. I was thinking of the Sonic Frontiers Power 3 mono blocks rated at 220 W continuous at 8,4, and 2 ohms. However, a guy recommended that I continue using the Brystons 7Bs for the lows and use a tube stereo amp for the highs. My problem here is I can't try amps at home (I live in a country where they are not available locally).

A The Sonic Frontiers should work fine, but you should try connecting them using the 4 Ohm tap first, then try the other taps to see which works best. Using the Bryston to drive the lows will also be a good option, since tubes sometimes have a problem driving very low frequencies. However, Sonic Frontiers is a high performance product, so the bass might be just fine using the tube amp to drive the entire speaker. Also, electrostatic speakers require lots of power, so bi-amping could give you a big improvement, especially since the Brystons might otherwise sit in the closet. The only tube amp you might want to be cautious about, with electrostatic speakers, is an OTL (Output TransformerLess) design. Their output declines with decreasing impedance, and electrostatics can go down to near 1 Ohm at certain frequencies.

Q I am in the process of adding on to my home theatre experience with the addition of DSS, only because of a lack of cable to where I am moving. My problem is that if I run the S-Video from the DSS box to the TV, I will have to disconnect it from the back of the TV when I turn the DVD player on. Just yesterday I upgraded my 25" Zenith to a 32" Toshiba with additional input/antenna selections. Yet, as with every TV I've seen, there is still only one S-Video input. Is there any way around having to physically switch the cables behind the television every time I want to watch a movie? I've seen the signal S-Video switch boxes at stores like Best Buy. Is that a plausible option?

A Yes, S-Video switchers are commonly available now, and that is the way to do it, unless you have several S-Video inputs on your receiver along with the S-Video output. There will be a small amount of signal quality loss when going through the switcher, but it is unavoidable. Likely, you may very well not even notice it.

Q I am considering the Paradigm Studio 100s over the Studio 60s since I would like a true 3-way speaker for music, matched with the Reference Studio C, ADPs, and Servo-15. One set-up, I am considering the Rotel RSP-985/RB-991/RB-993. When I tested the 100s for music only with the Rotel RA-985 pre-amp/RB-991 amp, the bass was very rich and full, however, the soundstage seemed a bit compressed to me. I am considering the Yamaha RX-V1 and Marantz SR-18, but am wondering whether they would be able to drive the bottom end of the Studio 100s sufficiently while opening up the soundstage. Would you have any advice or comments on my options?

A You should be able to use the amplifiers in the RX-V1 along with the Rotel power amplifiers to bi-amp the Paradigms, with the Rotel power amp driving the bass (from the RX-V1 pre-outs to the Rotel inputs), and the RX-V1 driving the mids and highs (through the RX-V1 speaker binding post outputs). The soundstage with home theater and 5.1 sound is heavily affected by room layout and speaker placement, so you should experiment with that too. Lastly, the soundstage may be more affected by the preamp than the power amp, so you should check out the soundstage of the RX-V1 by itself and paired with the Rotel power amp, compared to the Rotel preamp paired with the Rotel power amp. In other words, you have lots of variables, and you should check them all out.

Q A recent Q&A answer was "A third option is to add a subwoofer dedicated to the center channel and place it behind the TV, crossed over at 50 Hz, to go with the large center channel speaker. Anything you can do to beef up the center performance will make your system more enjoyable."  I have a PSB sub already in my 5.1 system, set up with an NAD 770 and a PSB center speaker.  How does one add a sub dedicated to the center channel?

A To do that, you need a receiver or processor that has pre-outs for all channels. Then, you just take the center channel pre-out and connect it to the line-level in on the dedicated center channel subwoofer. Because the big receivers now have very nice amps in them, we are going to test them in bi-amped mode by using the built-in amp to drive the mid/tweeter and outboard amp to drive the woofers, by using a combination of the pre-outs and the speaker outs at the same time. If you were to use the center pre-out to drive an outboard amp for the center channel speaker and the dedicated center sub, you would need a Y connector to split the signal coming from the pre-out. 

Q I have all the works for a surround sound system but don't know where to start to get it 'configured'. I've read about using those decibel meters but don't know how to use them. I have the top of the line Sony ES receiver and don't know where the settings for the different levels should be. Could you give me a guideline (numbers) on what they are supposed to be?

A All high performance receivers these days have a test tone mode to do what you need very simply. When in that mode, the receiver goes from channel to channel, usually starting with the front left, and sends a white noise signal to each speaker in turn. It will take you only a few minutes to adjust each channel loudness so that the volume sounds the same from each one while you are sitting in the listening position. You won't really need an SPL meter, but if you want one, get it at Radio Shack. They sell two types, one having analog meter readout, and the other having a digital readout. I bought the digital one. Sitting in the listening position, listen or measure the white noise signal as it passes from speaker to speaker and adjust the volume for each channel to the same loudness. A setting of 80 dB would be fine to use as a reference point.

Q I am in the market for a home theater amplifier (5 or 6 ch), and was considering either a Sunfire Cinema Grand Signature or a Cinepro 3k6(II) . . . both of which you have reviewed. Because you do extensive listening and tests, I was wondering if you would recommend one amp over the other. Please keep in mind that I do a great deal of music listening. If you could help me out with my decision, I would greatly appreciate it.
A These two amplifiers are so close in performance and sound quality, I think you would be happy with either one. If you get a surround sound processor with the EX channel in the rear center, but it does not have built-in amplifiers, i.e., a processor rather than a receiver, then probably the 3k6 would be best since it has 6 channels. If it is a receiver that has pre-outs and amplifiers, then either one would work great for your system because you could use the receiver's amplifier for the EX channel.

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