Q&A # 183 - June 15, 2000

Staff

Q My video room is 2.5 meters x 3 meters. I've just upgraded to a Yamaha DSP-A1, and my main speakers are B&W CDM1 SEs. Now I want to buy a pair of rear speakers. What kind of rear speaker should I buy? Dipolar, bipolor or direct? Is it necessary to buy a center speaker for this room size? My TV screen is 1.2 meters wide.

A I would suggest another pair of CDM1 SEs for the rear speakers. Yes, a center channel speaker is important, regardless of the room size. Get one of the B&W centers.

Q Do you folks recommend all-in-one speakers (speakers with a sub, midrange, and a tweeter all combined into one box) or separate speakers? The all-in-ones would be cheaper overall, but one would think that vibrations from the speaker would affect the sound quality.

A For small home theaters, or where your spouse does not like the idea of a separate black box for a subwoofer, speakers that have the subwoofer built-in, like the AR-1s that we reviewed recently, can be a good choice. The all-in-ones have lots of internal bracing to keep it from vibrating too much. But, when you have the space, I prefer to have the subwoofer separate, mainly because it gives me the option to choose a particular type of subwoofer, such as servo-feedback or push-pull, or whatever.

Q I want to add an external D/A converter to my DVD & LD front end. I was using the D/A converter of my receiver up until now, and it is not very good.  In any case, this analogue signal from the front end to the receiver has A/D conversion for DD & DTS processing, and later reconverted (D/A) for the power amplifiers. If I use an external D/A converter after the front end, my signal will still go through the receiver's D/A - A/D conversion process. Please tell me what to do, in order to reap the benefits of better D/A conversion.

A The A/D is only used for Sound Field processing, such as "Stadium", "Jazz Club", etc. If you want to avoid this, you can use a nice DAC connected to the digital output of your DVD player, then use the "direct" feature on the receiver so that it does not use any A/D - D/A. If your receiver does not have this feature, then just don't select any sound fields when listening to two-channel stereo. You should choose a modest priced DAC for your purpose - say, around $500. There are lots of them out there.

Q I am rebuilding my HT system (~$1200). So far, what I have decided on are the Onkyo 575x (to include S-Video Switching), the JBL S-38s up front, S-Center, and the rears are in question (The best I have heard in my area - kind of hesitant about buying speakers without hearing them first - fairly limited selection here). I keep getting conflicting information on the rears. Should I get the same as the front? If so, they are bookshelf speakers, should they also be 2-3 feet above my listening level? That could be kind of awkward and appear bulky with my room setup. Any suggestions you may have for me will be very helpful.

A Yes, get the same for the rears as for the front. But, you dont' need to put them above the listening position. They can sit on end tables or speaker stands to the right and left of the couch where you sit for listening. Digital surround has changed the need for putting the rear speakers on walls several feet above your ears. However, the new EX channel will probably have to be on the walls and above. Otherwise, they would end up right behind your head.

Q I own a middle of the line 5.1 system: A Sony STRDE925 digital receiver with Cambridge Soundworks Tower II fronts. I am fairly happy with the way everything sounds, but the receiver's EQ seems to be set very conservatively (for example, the bass crossover was set at 120 Hz). I want to get the most out of my speakers using the EQ. Cambridge Soundworks hasn't published the specs on the speakers (all I can find is a review of the speakers with some measurements, see http://www.cambridgesoundworks.com/reviews/twr2rew.html), but I can't make sense of the measurements they made. The EQ has 3 frequency adjustments for the fronts: Front bass (100 Hz to 1.0 kHz in 21 steps), Front midrange (500 Hz to 5.0 kHz in 21 steps), Front treble (1.0 kHz to 10 kHz in 21 steps), and each range (bass, midrange, and treble) has a dB +/- adjustment. I fiddled around with the EQ and managed to get a much clearer treble, but it seemed to be at the expense of the bass and midrange. Is this just part and parcel of using the EQ, or did my settings have a "hole" in them? Can you give me some general hints as to using an EQ? Should I bother with the EQ, and if so, what sorts of measurements should I make (I have a Radio Shack SPL meter) in order to evaluate the effects of the EQ? Should I use a test CD?

A Sometimes if you use EQ too heavily, it will sound as if someone has thrown a blanket over the speakers. Secondly, EQ induces phase shift, so it can end up sounding not quite "right". This is because harmonics of instruments are not in the proper time position with respect to the fundamental frequencies. However, I would suggest not using the 120 Hz high-pass of the receiver. That throws too much sound that can be localized as to direction, into the subwoofer. Try running your mains and center full range, and use the subwoofer's low-pass adjustment. If you have to EQ, just use one adjustment, such as the treble control, or the midrange, but not both, so that you don't add so much phase shift. Run all the other controls at the flat setting.

Q I own a Technics receiver with Dolby Pro Logic, and I'd like to purchase a DVD player in the near future. I want digital sound when I watch DVDs, and once I have a subwoofer, I'll have a speaker for each of the 5.1 channels, and would like to take full advantage of them. What I'd like to know is whether or not I'll need to upgrade my receiver, or will I get full 5.1 channel digital sound if I purchase a DVD player with a built-in Dolby Digital decoder?

A A DVD player with 5.1 analog outputs will only be useful if your receiver has a set of 5.1 analog inputs. Secondly, you will still need to have DTS decoding in your receiver, since DVD players with 5.1 analog outputs only send DD through those outputs, not DTS. The DTS has to be taken from the DVD player as a digital bitstream, through the digital output jack, to the receiver where it is decoded. Third, using the 5.1 analog outputs from the DVD player will eliminate the possibility of using sound fields in most receivers. My guess is that you will need to get a new receiver, with DD and DTS decoding, but that does not mean you should go out of your way to avoid getting a DVD player with 5.1 analog outputs. The best DVD players have those outputs along with other great features, such as component video. You would just not be using the 5.1 analog outputs.

Q I have a Sunfire Cinema Grand Signature amp. Sunfire recommends using both types of outputs, current and voltage, for best results. I have a pair of high end cables, so can I use the high end cable on 1 output and 12 gauge speaker cable on the other? If so, which output should I use the better cable? Or should I just use 1 output and not mix speaker cables?

A I don't see any problem with using the two cables, but I would suggest using the high-performance cable to drive the tweeter, since high frequency loss is a particular problem with low quality cables.

Q I have a similar question and largely similarly system to your reader in Q&A #170 in which you suggested getting a Class A Triode, Single Ended tube preamplifier, in particular the AE-3 preamplifier. Can I do a similar upgrade if my surround amplifier is a Sony STR-DE925? Or is the quality of the power amp section in my Sony not worth the preamp only upgrade? In any event can you suggest an improvement for my system without completely replacing the Sony 925?

A Something as wonderful as a single ended triode preamplifier will help any audio system, including one with a mass market power amplifier. I am sure you will notice a remarkable improvement. Later on, you can add a nice power amplifier to go with it.

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