Q&A # 264 - November 13, 2001

Staff

Q I have an Onkyo 787 THX select 6.1 receiver. Power 100W at 8 ohm. I am planning to buy Paradigm speakers. CC-70, Monitor 5 or 7, ADP 170, and Subwoofer PS-1200.

On the Paradigm homepage is written the following: Suitable Amplifier Power Range and Maximum Input Power. For example, for the ADP-170 it says: S. Amp Range: 10-100W and Max in Power 80W. But then for CC-70 it says: S. Amp Range: 15-80W and Max in Power 60W. Then for Monitor 5 it says: S. Amp Range: 15-175W and Max in Power 120W. What can I conclude about that? Does it mean that the Monitor 5 speakers are the only ones that completely will meet the power of my receiver? What kind of speakers are more suitable than the ones that exceed the power of the receiver or the ones that are slightly below recommended? For instance If I buy the CC-70 and turn up the volume to about 60-70 dB, will I ruin the speaker on what? Another thing, as mentioned I have the 6.1 receiver, but I plan to make it 7.1 by connecting two back surround speakers (ADP-170) to only one speaker plug on the receiver (not parallel). Do you think this is OK, or should I just use one back surround and throw the other one from the pair (they only sell speakers in pairs) to the cellar?

A I know how you feel in the confusion of speaker ratings. There are lots of variables, such as the impedance, sensitivity, minimum power, maximum power, etc. I don't think you are going to have any problems with the receiver and any of the speakers you mentioned. Since they are 8 Ohms nominal, and probably similar in sensitivity, the receiver will drive them fine. If you don't watch movies at really high loudness, no adjustments will be necessary. If you like to turn things up, you might try setting the bass management for the center channel so that you send the low frequencies (the receiver probably has a low-pass of around 80 Hz) for the center channel to the subwoofer. That will give your center channel speaker a little more breathing room.

Q Very nice to see the ICBM get deserved recognition. Great info in the article, too, by John K. In it, has asked a couple of rhetorical questions, but I may be able to shed some light.

"The L/R Recombine toggle switch has both On and Off (Duh). Factory default for this switch is Off. I'm not sure I like the labeling, but it's their product, so they can name it as they will. More importantly is its function; L/R Recombine is used as a method of augmenting the output of nearly full range mains with output from the subwoofer. When on, the crossover is engaged at the selected frequency with the appropriate low-pass output sent to the subwoofer. The left and right speakers themselves still receive the full range signal."

Recombine does more than allow the main L/R speakers to remain full range while its bass can also go to the sub. Recombine means that the signals from any of the filtered channels also is redirected to the main L/R speakers. It allows the L/R to be the main bass reproducer, and still allows the sub to supplement wherever the L/R finally give out. It's something quite important in certain user's systems. (You can ask Peter T why I happen to know this, if you like....)

On another topic, John wrote: "Let's start off with the basics. Taking a 5.0 track on DVD-A and derive a 0.1 track. Emerson, Lake and Palmer's Brain Salad Surgery has two tracks that are recorded as 5.0, "Benny the Bouncer" and "Still You Turn Me On". Why these two tracks were 5.0 with the rest of the disc being 5.1, I do not know."

While Paul Klingberg was mixing the project, I was chatting with him about use of the LFE channel in music recordings, and how it can be more of a detriment than an asset when it comes to maintaining phase coherency across the spectrum (there's a paper on this at our website). He decided to try a few tracks mixed as 5.0, and has found it quite agreeable. The only problem is that misguided marketing efforts have driven the demand for that point-one track even for contact that has no business using it. Too bad.

And on a related note (and somewhat of another soapbox), I just wanted to suggest a bit of caution in terminology. John innocently wrote: "They shoot, they score! A 5.0 track now has a derived 0.1 track." And "Once again, the Cinepro's visual indicator didn't let me down, and showed the presence of a derived 0.1 track from the stereo output."

Bass management in a home decoder is just that, bass management. Or call it a crossover system. In any case, it is the derivation of a subwoofer feed, not a 0.1 track. We think it is necessary to make the distinction because consumers often think the only signal that needs to go to their sub is the 0.1 track (the LFE track has been called the subwoofer track, which it is not), when in fact the output of the bass crossover system is the bass from every channel that cannot otherwise be reproduced by the respective main speaker.

I know y'all knew that, but just mentioning it in the name of accuracy.

Best regards,
Roger Dressler
Dolby Laboratories

A Thanks for the info Roger.

Q I have a Harman/Kardon AVR35 receiver. When I use anything other than the "Surround Off" mode (Pro Logic, Stereo 3, Hall 1, Hall 2, Hall 3) I get crackling even at low volumes from my right channel. I've done a basic check of connections but can't seem to find anything that isn't connected well. Any ideas?

A I would suggest trying the stereo analog output of your CD player vs. the digital output into your receiver. Also try an input that has nothing plugged into it. If it happens with all  types of inputs, then the problem is in the receiver, and you should take it in for repair. If it happens only with the stereo analog input, try reversing the cables. If that changes it to the left channel in your speakers, then it is the player or one of the cables. If it happens only with the digital cable, it may be the decoder in the receiver.

Q My turntable is a Pro-Ject 6.9, and the phono stage a Densen DP-01 mounted in a Densen Beat 200 preamp. My power amp is a Parasound HCA 1500A, speakers are Infinity Renaissance 90, and cables are Synergistic Research. Price on my current cartridge is around $350. I have been recommended Grado Reference Platinum (MM), Benz Micro Silver (Ho MC), Sumico Blue Point Special (Ho MC) and Clear Audio Aurum-Beta S MKII (MM). What should I look for in the specs? The Beta S got a tremendous review in a printed magazine in April -00, and Robert Reina said maybe the best under 1000$. Here in Norway it's cheaper than in the US. But the specs are not near the others in terms of frequency response and channel separation. 20 Hz-20kHz and 28 dB, while the others are 15 Hz-50kHz and 35-40 dB. My music is mostly rock from, from heavy to jazz. Little classic. Any suggestion?

A Since you don't have the opportunity to listen before you buy, I would suggest the Sumico Blue Point Special. It has high output and is moving coil. I have always heard great things in various magazines about it, and it is a very good value at only a few hundred dollars. It is the cartridge I would buy for myself.

Q I love your DVD Benchmarks, as they are a fantastic service to the audio and video public!

I recently purchased the Panasonic RP-56 DVD player, which had a good review here and looked decent in the store at a fantastic price. When I measured the Pixel Croping with Avia, it showed > 20 on all four sides. I have asked Panasonics Tech Support and they are phone answering support types. I tried my old Pioneer and it was better, so I know the projector is capable of showing more?

Is this normal to differ this much from unit to unit ? Your tests show much better numbers.

I am viewing on a Sanyo PLV-60 using progressive.

A The TV (rear projector or direct view) will also crop pixels, so that is probably where your difficulty is. Even a front projector will crop pixels if not set up properly.

Q I'm about to buy an almost 2 year old receiver, the Sony STR DE825. Please read these reviews: http://www.excelsis.com/vote/av/receivers/SonyST5/. It seems like half the people have the problem with that Protector message, and all of them after 2 years !! I was even thinking Y2K bug or something. Are you aware of issue like that ? I'm really looking forward to your reply.

A It is clear from the comments on that message board that this particular player has design problems. The protection message means something is shorting out. So many complaints about this means you should forget purchasing it, used or new.

Q I don't want "real" home theater sound at the moment, but I want to get better sound from DVDs than my TV can deliver. My plan is to build my own power amps and speakers. I will use the DVD's S-Video signal and its analog stereo audio signal. My question is, can I derive the center channel and surround signals from the stereo audio that will do the job that digital processing does? If it is a matter of combining the channels (L + R) for center channel and subtracting them (L -R) for surround, no problem. If digital processing is required, are the processing chips (Dolby or whatever) available to the DIY'er?

A The center channel is encoded in the stereo analog signal as the information that is identical and in phase in both channels. The rear surround is the identical information that is out of phase in both channels. For digital decoding, DACs are available from companies like Burr-Brown for a few dollars.

Q I have a Yamaha DSP-A1 , B&W LCR6 S2 speakers for main and center channel, and a pair of Yamaha NS-E105 6 ohms surround speakers. I want to add another 2 pairs at the rear a total of 6 surround speakers. If I connect them in series the impedance is going to be 18 ohms. Is that ok with my amp, and what would the impedance be if I connect them in parallel and how would that  affect the amplifier? What will be the best way to connect them all? I was thinking I could connect each channel with 2 speakers in series and connect the third in parallel with the other 2 speakers, but I can't figure out the impedance that the amplifier would see.

A If you connect them all in parallel, the impedance would be 2 Ohms, and your receiver would not like that at all. All three in series gives you 18 Ohms as you said. Your receiver would be fine with this, and although the impedance is high, the combined volume might be OK since it involves three speakers. Connecting two in parallel gives you 3 Ohms, and combining them with a third in series, gives you 9 Ohms, which is just about perfect. You could try them in the various ways, but stay away from all three in parallel.

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