Thread: need help on best MC amp/speaker specs for SACD

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Post by Windsurfer March 7, 2007 (31 of 34)
seriousfun said:

Pentatone is treating these releases properly.

4.0, or Quad, mixes should be distributed as 4.0. An SA-CD or DVD-A (or BD or HD-DVD) can carry this quite well with no loss (or a DTS CD with loss).

There is no need to create a Center Channel from a 4.0 mix, but if appropriate material is recorded, the Center Channel shouldn't be ignored if the intentded delivery medium is 5.1-capable. There is never never never a need to use the LFE channel in any music mix.

From a playback standpoint, again, a subwoofer is not necessary for every system. If any of the main speakers do not go down to the full-range of the source, they can be properly extended with the addition of one or more properly-integrated subwoofers.

In your case, five identical small electrostatics and properly integrated subwoofer might or might not play better than your current system, whether your source is Mono or 5.1.

I wasn't refering to the RQR series but to the new DSD recordings in 5 channels. I don't quite understand your point about never a need to use the LFE channel in any music mix. It provides the opportunity (since bass below a certain frequency is supposedly omnidirectional), to route all the bass to the subwoofer and permit the use of smaller speakers thus facilitating the "wife acceptance" factor of multi-channel systems.

For my part, I suppose I could benefit by putting the Mirage "subwoofer" that is part of the omni-sat system between my rear speakers extending their range, and I would feel better about a subwoofer with a crossover that took the very low frequencies away from my planar magnetics, reducing fears of blowing the bass panels on loud bass drum and organ passages.

Post by seriousfun March 8, 2007 (32 of 34)
Windsurfer said:

I wasn't refering to the RQR series but to the new DSD recordings in 5 channels. I don't quite understand your point about never a need to use the LFE channel in any music mix. It provides the opportunity (since bass below a certain frequency is supposedly omnidirectional), to route all the bass to the subwoofer and permit the use of smaller speakers thus facilitating the "wife acceptance" factor of multi-channel systems.

A 5.1 system includes five full-range channels. Full-range, both in frequency and dynamic range.

The LFE channel was developed as Low Frequency Effects, or Low Frequency Extension, or the Boom Channel, for cinema - even the largest movie theater systems start rolling off in an auditorium below 30 Hz (rapidly, since they are typically horn-loaded systems), and with the addition of multitrack sound to widescreen movies in the '50s one of the channels was used for loud low-frequency sounds to improve the quality of those sounds and add dynamic range to the main channels. DVD-V carried-on this channel for two reasons: movies were already mixed in 5.1 using the LFE channel, and small speakers with an added subwoofer were already a popular home-theater speaker configuration. When a film mixer uses the LFE channel, it is for unique loud and low content.

Music is a different story. Even the lowest pipe organ tones and transients, and the cannons in the 1812 Overture, can be acommodated by any one of the main channels on a CD, SA-CD, or DVD-A. The fact that we have five of these means that there is dynamic range for music available far exceeding our ability to withstand the potential SPL of all five channels running.

(Please understand that I'm not lecturing you, but I am hoping that many are reading this and will grasp this fundamental concept)

What you are describing above is not an LFE channel, but Bass Managment. Bass Management is simply speaker management, a way of integrating a subwoofer with main speakers, and should be treated like any other external crossover (it shouldn't be the weak link in any system, for example, but in most cases its benefits far outweigh the disadvantage of it being more active circuitry for your signals to pass-through). There is much mis-understanding of this concept.

Using the LFE channel to deliver bass content is fraught with disadvantages, and has zero practical or sonic advantage.

If the bass content delivered in the LFE channel is unique to that channel, upmixing to two-channel, and many bass management circuits, will simply discard this information! Unique bass content delivered with the LFE channel will severly limit the dynamic range of the main speakers the sound is being added to - hardly ideal, since these are often the most important and should have the most dynamic range available.

If the bass content delivered in the LFE channel is a duplicate of some or all of the bass content in one or more speakers, all bets are off. This pretty much guarantees that no home system will be able to reproduce this as it was on the monitor system used in mixdown. Remember that no movie mix (at any rate it's rare) has duplicate content in the LFE channel and one or more main channel, so music mixers who use the LFE channel are re-inventing the wheel in a particularly self-destructing manner. If, for example, the main recorded channels are summed to the LFE channel (as many 5.1 orchestral recordings are unfortunately mixed) in most systems much of the spaciality and hall reverberation will be lost due to phase anomolies, and bass instruments will be reproduced inconsistently from one system to the next. If certain instruments, like kick drum and bass guitar (even the 'cello on the recent Beatles' Love Eleanor Rigby 5.1 mix) are in both the LFE and one or more of the main channels, the listener will be fatigued by comb filtering above the crossover point, phase issues, and inconsistent delivery. Many surround music mixers mistakenly mix content to the LFE channel, thinking the consumer will get more for their money if all the lights light-up, or that it's some kind of hedge against inconsistent home systems (quite the opposite), or that it's some sort of directional channel; all of these approaches are far, far from the truth, and IMO are one of the reasons why surround music hasn't become more popular.

The proper way to mix music for 5.1, whether rock or classical, SA-CD or DVD-A, is to mix bass content, surprise, the way we've done it for half a century - record the low end properly, and mix and master it properly through the available full-range channels, only this time we have five channels to handle this, not just one or two, and therin lies a wonderful advantage over 2-channel music delivery, even if the other three channels are not used for spatial information.

The proper way to play these five full-range channels is on a speaker system with five full-range channels. There are, again, two ways to get here - five true full-range speakers, and a sixth limited-range speaker (subwoofer) for the LFE channel, or five limited-range speakers with a properly integrated subwoofer.

Richard Elen has convincingly and eloquently described this http://ambisonic.net/bassmgt1.html, as has speaker manufacturer Genelec in Resolution Magazine www.resolutionmag.com/pdfs/SWEETS~1/genelecdsp.pdf.

Post by Windsurfer March 8, 2007 (33 of 34)
Thank you for your informative reply.

I did try the link you provided for the ambisonic page, but I got an error 404 message. Was the link incorrect or did they take the page down?

Post by seriousfun March 8, 2007 (34 of 34)
Windsurfer said:

Thank you for your informative reply.

I did try the link you provided for the ambisonic page, but I got an error 404 message. Was the link incorrect or did they take the page down?

go to www.ambisonic.net, click on articles on the left, and choose "All Bass is Covered"

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