Q&A # 253 - September 15, 2001

Staff

Q I'm wondering if ever you'll do a primer on AC line conditioners? What I would specifically look for is the importance of the following: balanced power, noise suppression, surge protection, voltage regulation, and AC sine wave integrity. The first three are obvious to me, but the last two, not so obvious.

A Yes, we will be including line conditioners in some of our Benchmark tests in the future. We need some test equipment that will have to be purchased to do it. All of the factors you list are important, but surge protection is the only one that does not have a direct effect on the sound. It just protects your equipment against damage when there is a big spike from whatever source, such as lightning.

Q I don't know if people write you enough in terms of the benefit they get from your web site. It's not just a web site though. You provide education and *sanity* in a field that is often without either.

"Give a man a fish, and he's fed for a day. Teach him how to fish, and he's fed for a lifetime."

I also really appreciate how you cruise Home Theater Forum, and speak up sometimes when you see a place where you can contribute.

I view Secrets as in the same category as (the old) Audio and Stereo Review. Listening tests in addition to, as much as possible, comprehensive measurements.  (Proper) measurements, in my opinion, are really lacking in most of today's home theater publications.

THANK YOU!!

A Yes, we get nice compliments like yours constantly, and it is rewarding to feel appreciated, because this is a lot of work. Thank you for your comments. We have many things planned for our expansion. Some will surprise everyone. Others will just be appropriate expansion of existing techniques into other areas, such as Benchmark tests for equipment in addition to DVD players.

Q I registered at the Weekly News page, but I haven't really gotten any e-mails or anything back. That's good, I guess (no spam!), but is there some benefit? I thought I would get e-mail notices of new equipment reviews, and stuff.

A We probably have the only such news letter registration web page in the world that is so under-utilized, but our policy is not to violate registrants' privacy with spam. It will be used for things like notification of special articles that have been published, news items about other A/V companies, and pre-release of clues for the contests like we mention on the registration page. There is even one A/V web-zine that puts you on their mailing list just when you visit their website, whether you ask to be on the list or not, by capturing your address. They run their magazine like a regular business, with flashy pages and complicated navigation, because the low quality of their articles will not build sufficient readership to get advertisers on board. We don't do that here. It is more a labor of love, but we have had many offers to take us to print, or join forces with major organizations that do run things as a regular business. We may take one of these offers up, as long as we are able to maintain editorial independence.

Q I think I saw that *someday* you hope to get a jitter measurement device, so that you could characterize that parameter vs. sound quality for linear PCM. (I would donate towards that!) And then whether jitter even matters for digital Dolby Digital and DTS signals. (I think that I understand that theory says it doesn't, but people still insist there's a benefit for DVDs.)

A Yes, that is one of the things we will be measuring in the future, once we get the appropriate equipment (it's expensive). There are lots of factors that affect the sound. Jitter is just one of them. Jitter means that the bits are not arriving at the right time, either early or late, from where they are supposed to be. This distorts the sound waveform. It can occur in several places, including the interface (cables) between transport and DAC. Any digital bitstream can be subject to jitter, including DD and DTS which are 20 bit - 48 kHz data. Having some RAM in between the transport and DAC allows the data to be collected, reclocked to the correct rate, and then fed to the DAC. As the frequency goes up (24/192), it will take a lot more RAM to do this properly.

Q What's really the difference between having a progressive or interlace DVD player having a 54MHz /10 bit video vs. a 54MHz/12-bit video? What am I missing between these two?

A The higher frequency (54 MHz) is for oversampling, just as in CD audio. It helps to push the video noise out of the region that is displayed. Having more bits reduces the noise in the first place. If you use a digital audio recorder on your PC to record a sound at 8 bits and then the same sound at 16 bits, you will hear the noise in the background at 8 bits very easily.

Q I have Paradigm's Studio Reference 100 V.2 , CC-Studio Center, and Export Monitor (rear surround) speakers as well as the Paradigm Reference Servo 15 Sub woofer. I drive all the speakers (except the powered sub) with a Bryston 9B THX 5 channel amp. I cannot seem to get a straight answer out of anyone regarding the crossover setting/speaker designation. I am using a Denon 3600 as a pre/pro but it only has the 80 Hz crossover when the speakers are set to "Small". If I run the Studio 100's full range ("Large"), will the LFE channel or lack of information in it cause the sub to shut down until it is needed and then miss part of the information because it could not "wake" up in time? Or could I crossover to the sub at 50 Hz using the X-30 active crossover that comes with the sub? How would I go about setting this up? Thanks.

A If you set the mains to "Large", this does not necessarily eliminate sound going to the subwoofer. It only is for saying whether you want the bass to go to the mains or to the sub. Deep bass will still go to the subwoofer unless you use the receiver's bass management to say that you don't have a subwoofer, in which case, the bass would be sent to the mains. The subwoofer output circuit in the receiver sums the bass signal in all channels. If you set your mains to "Small", everything below 80 Hz will be eliminated from the mains, but it won't necessarily change what you get from the subwoofer output jack. As to the subwoofer not "waking up in time", if you are referring to a subwoofer that has an automatic on/off, that might indeed happen. If it is always on, you don't have to worry about the circuit itself not reacting in time. It is essentially instantaneous. I prefer setting the speakers to "Large" and setting the sub's crossover at 50 Hz.

Q I use dipole speakers in the rear, and they work fine with home theater. However, when I listen to CDs, the sound is too diffuse in the rear. Cambridge Soundworks has the S300 speaker that lets you switch between dipole, bipole, and direct radiating. Could you test these speakers for us?

A We will look into this. Stereo (two-channel) CDs in various surround DSP modes will give you a diffuse sound from the rear though, because this type of sound is not discrete. Try listening to some DTS CDs, which do have discrete channels in the rear. You may find that discrete 5.1 will still be OK with your dipolar rear speakers.

Q I have some expensive speakers. Could I put a fuse in line with the speaker cable so that it will blow if the current gets too high?

A Yes, but keep in mind that this will add impedance to the circuit.

� Copyright 2001 Secrets of Home Theater & High Fidelity
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