Q&A # 201 - October 19, 2000

Staff

Q Bravo on your review of the Apex A600D DVD player! Though I am not interested in that particular player, it is THE most useful review of any consumer electronics product I have ever seen. This is due in large part to your DVD Benchmark Project, which I feel is what makes your site unlike any other on the net (or print).

I must admit that I complained a few weeks ago that there were no reviews of actual products using the information you compiled in your DVD Benchmark installments. You'll forgive me for my impatience.

I look forward to future reviews of DVD players. Considering that I am now looking to buy my second player, your reviews will be my primary source of information.

A Thanks for your support. More reviews from the Benchmark tests will be coming shortly.

Q What will I lose/gain or what issues might I have using the Sony 945 with 5.1 speaker outputs since the Bose AM-7 runs
the front 3 channels to the sub before the main speakers? I also have a set of CSW "Surround 5.1" Multipole speakers for the rear. Do I lose anything not using the LFE output? Is this a decent setup?, I have not yet bought the Sony 945, but it seems reasonable for the price.

A The only thing you really need to be careful of is having the bass management in the receiver, regardless of the brand and model, set to "Large" for the front three speakers. This is because the Bose needs the full bandwidth in order to separate out the bass to send it to the Bose subwoofer and the rest to the front three speakers.

Q What is your review/recommendation on the Onkyo DR-90 Receiver with a DVD Player?

A This particular unit is a combination receiver and built-in DVD player. Personally, I do not like integrated packages like this, because it prevents you from making upgrades to the player or receiver, such as DVD-A, SACD, etc. If you want to upgrade, you have to replace both the receiver and the player, rather than just one or the other.

As to selecting a DVD player to go with a particular receiver, for receivers in general, if it is a two-channel stereo receiver rather than a surround sound receiver (only a few are like this nowadays), then any DVD player will work, but you will have to use the two-channel analog outputs from the DVD player. If it is a surround sound receiver but has no DD or DTS DACs built-in, and no 5.1 analog inputs, then you still must use the two-channel analog outputs from the DVD player. It it has no DD or DTS DACs, but has a set of 5.1 analog inputs, then get a DVD player that has DD and DTS DACs built-in, which means it will have a set of 5.1 analog output jacks. If the receiver has DD and DTS DACs, then all you need is a DVD player with DD and DTS digital outputs. Remember, we are distinguishing between just the DD and DTS decoding from DD and DTS DACs. Decoding just converts it to a bitstream, while the DACs convert the bitstream to analog audio.

Q If I have a powered sub connected to my main speaker terminals (with main speakers also connected) on my receiver and turn the sub off, will my receiver still try to drive the sub and if so will this damage the receiver? When I listen to music, I turn the sub off. I don't notice any sound degradation, so it seems okay, but who knows what might happen in the future?

A The subwoofer has its own power amplifier. When you turn it off, the output from your receiver is simply connected to an input that is not active. It won't hurt your receiver. If you don't notice a change with the subwoofer off, you probably have your receiver bass management set to "Large" and subwoofer "yes". You also probably have full range speakers. A subwoofer can add a great deal to music if it is a good subwoofer capable of going down to 20 Hz. You should try playing your music with the subwoofer on. Experiment with the crossover frequency and phase.

Q I am taking a look at upgrading my subwoofer in my home theater set-up. I currently am utilizing all B&W speakers - 604 S2 Mains, CC6 S2 Center, 601 S2 rear surrounds, and a B&W ASW 500 subwoofer. My goal is to upgrade to a sub that can reach down to about 20 Hz. I was anticipating on having to buy a sub with a 12" or larger driver and something with a good sized cabinet. But upon actually shopping, I was surprised at the size of the cabinets and drivers for newer subs that reach down to 20 Hz or so. Specifically, I was looking at the B&W ASW 2000 and was surprised by the B&W ASW 2500. I was also surprised by Velodyne's HGS 10 or 12 sub in terms of size and specs. My question is, how can such low frequencies be attained from a sub cabinet size that is roughly 12-14 inches cubed. What is the trade off between the new smaller sized subs and the older styled larger subs? What about Velodyne's seemingly amazing sub amp specs for such a small unit? And what is your opinion of B&W's subwoofers (specifically ASW 2000) compared to Velodyne's HGS series (which has gotten great press)?

P.S. - I am using Yamaha's RX-V1 receiver and was wondering if I should continue to employ my current B&W ASW 500 subwoofer (i.e., utilize two subs) with whatever new sub I purchase.

A Bob Carver at Sunfire is credited with the "deep bass from a small box" design, and it is one of the cleverest ideas in hi-fi to come along in a decade. Basically, all speakers can reproduce low frequencies, as long as they don't have a specific filter to keep them from doing so. But, in order for you to hear them, the speaker has to move a lot of air. To do this with a 10" driver in a small box takes two things. One is a driver capable of large excursions, at least one inch from front to back. Secondly, you need lots of amplifier power, i.e., hundreds of watts rms. Bob designed an amplifier that could deliver all that power, and without getting hot. It was also very efficient, and didn't need a transformer, so he could put it in a small enclosure. Then, he designed the driver for large excursion and that huge rubber surround that you can see not only on his design, but on all the ones that other manufacturers soon made to compete with it. So, once you have the driver and big amplifier, you fine tune the whole thing to get the loudest and deepest bass you can out of it. They are fantastic subwoofers, playing down to 20 Hz without any problem. The drawback is that they have to work very hard, sometimes moving across the floor. In Velodyne's case, they use basically the same driver from the 10" model all the way up to their 18" model, with the only difference being the size of the cone. The magnet structure is almost identical among all of them. The power amplifier is the same too. But, what you get from the 18" version is about 6 dB greater loudness, and a response down to 15 Hz. If you have the space, get the larger one, but if space and size of the box are a concern, these new small box - high output subwoofers are terrific. And, yes, use two subs if you can fit them in. The top Yamaha units have stereo subwoofer output jacks, and having stereo subs is quite an experience.

Q How can you use a separate preamplifier with a surround processor or receiver that does not have an analog bypass?

A You have two choices. One is to manually unplug the connections each time you want to switch between the preamplifier and processor. The second one is to get or build a switch box. You can find such boxes in places like Radio Shack. I would prefer to build one using very high quality RCA jacks, such as WBT (http://www.wbtusa.com) and switches, using the highest quality wire I could find (silver-plated copper with Teflon dielectric), and putting them all in a steel chassis.

Q My query regards the quality of the DAC in CD players and surround processors. My setup consists of a Rotel RCD-971 CD player connected to a Rotel RTC 965 processor via analog outputs. My question is, would I achieve better quality using the digital output from my CD player?

A The actual DAC chips in various products are very similar in quality, partly because they are not very expensive. It is the associate circuitry that makes a big difference. You need to test this yourself, by connecting a digital cable from your CD player to a digital input on your processor. Connect it to a different input set than the analog connections have. For example use the "VCR" input for the analog connections, and the "CD" input for your digital cable. Now, all you have to do is put on a good CD, and switch between VCR and CD on your processor. You should be able to hear any differences that exist between the DAC in your player and the DAC in your processor.

Q I have an old Yamaha DSP-A780 Pro Logic Amplifier, Energy Take 5, and an Energy ES-8 Subwoofer. My question is should I use the low pass or the high pass filter on my subwoofer and can you tell me what the difference is? The low pass out on the back of the amp says 200 Hz. What does this mean?

A There are two crossover points with powered subwoofers that you need to know about. One is the low-pass setting, which is usually variable from about 40 Hz - 120 Hz. You set that one to the frequency, below which, you want all frequencies to go to the subwoofer amplifier and driver. So, if you set it to 60 Hz, the subwoofer will deliver sound from 60 Hz down to its limits, say 25 Hz. The second crossover is for use with satellite speakers. In order to use this, you have to first send all frequencies throughout the audio spectrum to the subwoofer, i.e., 20 Hz to 20 kHz. You can do this by connecting left and right front pre-outs to the subwoofer using the line-level input RCA jacks on the subwoofer enclosure. You can also do this by connecting the speaker outputs from the left and right front channels to the speaker-level inputs on the subwoofer (they will either be spring clips or banana jacks). Then, you connect the high-pass outputs from the subwoofer - either line-level or speaker-level, depending on what you sent in - to power amplifiers for the front left and right channels, or the actual front left and right speakers. This second crossover frequency (the high-pass) is usually fixed, and is often around 90 Hz. Taking the output from here will send all frequencies from 90 Hz and up to your satellite speakers. In your case, I think you are referring to the low-pass out from the receiver, which means that it is a subwoofer output jack, and outputs all frequencies from 200 Hz on down.

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