Speaker upgrade for classical music

Hi ssm,

I’d like to comment about one of the characteristics you mentioned:

"What I want: speakers... that really reproduce the expansiveness of the symphony hall or church."

In home audio there is a competition between the acoustic signature of the venue (which is on the recording) and the acoustic signature of the playback room. In most home audio systems, the "small room signature" of the playback room dominates.

Imo we can look to what works well in the concert hall for inspiration. Quoting acoustician David Griesinger:

"Envelopment is the holy grail of concert hall design. When reproducing sound in small spaces [home listening rooms], envelopment is often absent."

"Envelopment is perceived when the ear and brain can detect TWO separate streams: A foreground stream of direct sound, and a background stream of reverberation. Both streams must be present if sound is perceived as enveloping."

Implied by the TWO STREAMS paradigm is a time gap in between the direct sound and the strong onset of reflections. This is desirable in the concert hall AND in home audio, though the timescales are less in home audio because the reflection path lengths are shorter. How long of a time gap is adequate? Griesinger again:

"Transients are not corrupted by reflections if the room is large enough - and 10ms of reflections free time is enough."

We can get the 10 milliseconds of reflections-free time (in the horizontal plane at least) in a room the size of yours by using speakers which are directional enough to avoid putting much energy into the same-side-wall early reflections. But we also need to have a significant amount of energy in the subsequent background stream of reverberation. There are several possible ways of accomplishing this, one of which is to use a multichannel system.

Recall that there is a "competition" between the venue cues on the recording and the small-room signature of the playback room. It is the EARLIEST reflections which are the most responsible for small-room signature (though decay time can also play a role). By minimizing the energy in the early reflections, and having plenty of spectrally-correct energy in late-arriving reflections, and using diffusion instead of absorption (kudos for your use of diffusion!), we can use these later-arriving reflections to effectively present the venue cues on the recording. And when the venue cues on the recording dominate over the playback room’s inherent small-room signature, if it’s a good recording, we have envelopment.

So envelopment is elusive in home audio, but can be accomplished by applying the principles that work well in the concert hall, which usually calls for some creativity (unless the playback room is very large). Envelopment isn’t the ONLY thing that matters of course, but it can be borderline transcendental when it happens.

I can go into some specifics if you’d like. Doing so would involve describing things that I’m commercially involved with.

Best of luck with your quest!

Duke

Hiphiphan wrote: "Audiokinesis/Duke: I for one would love to read more about what you’re describing. I have two questions in particular:

1) You mentioned that envelopment can be achieved through a multi-channel system. Do you mean basically playing a normal, two-channel recording through two sets of speakers, one in front of you and one behind, with both sets playing the exact same thing? Or do you mean using special recordings that were intended to be used specifically with multi-channel systems (in which what the front set of speakers plays is not identical to the rear set)."

Duke replies: I mean the latter: Special multi-channel recordings with the reverberation (ambience cues) delivered through dedicated surround speakers. Not that this is necessarily the only way a multichannel system can deliver envelopment, but it’s what I had in mind.

Hiphiphan again: "2) The other way to achieve envelopment you describe is as follows: "By minimizing the energy in the early reflections, and having plenty of spectrally-correct energy in late-arriving reflections, and using diffusion instead of absorption..., we can use these later-arriving reflections to effectively present the venue cues on the recording. And when the venue cues on the recording dominate over the playback room’s inherent small-room signature,...we have envelopment." I’m confused by this. If we are deliberately emphasizing later-arriving reflections created by OUR OWN ROOM, how is this the same as "the venue cues on the recording dominate over the playback room’s...signature"? By definition, if we’re trying to make certain room reflections dominant, then we’re not making the reflections captured on the recording dominant."

Duke: EXCELLENT QUESTION!!

Basically I’m advocating chopping the radiation pattern of a normal speaker into two pieces, aiming one piece at the listening area, and aiming the other piece in a different direction such that it arrives after some time delay, because this works WITH rather than AGAINST the playback room and the ear/brain system.

The proper role of the in-room reflections is to effectively deliver the venue cues on the recording, whether they be real or engineered or both (this isn’t their ONLY role - more on that later). However they also inevitably contain “small room” cues inherent to the playback room. The ear/brain system will accept (or synthesize) whatever sense of acoustic space is most plausible, and USUALLY this is dominated by the playback room’s cues.

The ear gets its information about the size of a room from two main sources: The early reflections, and the decay characteristics. The approach I advocate disrupts the “small room signature” cues that the early in-room reflections would normally convey, and effectively presents the decay cues which are on the recording.

The time delay between the first arrival sound and the “center of gravity” of the reflections tells the ear/brain system about the room size. If we can push that center of gravity back in time, we can disrupt and weaken the playback room’s inherent small-room signature. The approach I advocate does this by a) minimizing early reflections and b) adding MORE reflections which arrive at least 10 milliseconds behind the direct sound.

Now as long as the playback room isn’t overdamped, this additional reverberant energy results in a lot of spectrally-correct reflections, which effectively present the venue cues (and in particular the decay cues) that are on the recording. And part of this "effective" presentation is that the venue cues come from all around. (Directly from the loudspeakers is the WORST possible direction for reflections to come from, which is why overdamped rooms don’t convey envelopment). With a good recording, the venue cues carried by the reflections dominate and we can close our eyes and enjoy the illusion of envelopment. It’s not a perfect illusion of course, but imo it’s a worthwhile improvement to a normal stereo image.

The OTHER role of the in-room reflections, assuming they are spectrally correct, is to enhance timbre, much like the reflections in a good recital hall. Since the path lengths are shorter than in a recital hall we run the risk of degraded clarity if the in-room reflections are too loud, so I give the rear-firing driver array a user-adjustable volume control.

I realize these ideas are unorthodox and somewhat counter-intuitive. In particular it is counter-intuitive to think that by ADDING reflections, we might actually perceive MORE of the recording venue and LESS of the playback room. After hearing an abbreviated version of my schpiel at an audio show, Andrew Quint of The Absolute Sound pulled out a thumb drive and said, “I’d like to challenge that”. Obviously he was skeptical too! We played the piece on his thumb drive and I asked him how we did. He said, “It passed. It’s not a gimmick; it works. I clearly heard the acoustic signature of the Concertgebouw.”

Quoting from Andrew’s version of that incident:

"The recording was a FLAC rip of the CD layer of an RCO Live SACD: Shostakovich—Symphony No. 15; Concertgebouw Orchestra/Bernard Haitink conductor. It’s a live recording from March of 2010 (Haitink made a much earlier recording of the same piece with the London Philharmonic; he was the first person to record all the Shostakovich symphonies.) For a couple of years, this has been my go-to symphonic recording when I have just a short time to get a sense of an unfamiliar system. It’s an excellent performance, something I can listen to repeatedly without going nuts, which is important at a show. In terms of audiophilia, it’s an extremely detailed yet atmospheric representation of an orchestra, with excellent dynamics and fully characterized instrumental colors (bells, solo turns by violin, flute, piccolo, string bass, trumpet, etc.) And—with the right audio gear—it successfully renders the essence of (IMO) one of the greatest 3 or 4 concert halls on earth, the Concertgebouw (thus the orchestra’s name) in Amsterdam. I’ve heard music there, and there’s truly a sense of sound being present in the air around you.

“The multichannel program on the RCO Live SACDs (there are dozens) get this last aspect right; so did the Bienville Suite, nearly to the same degree, despite the presence of only two channels. My concern when Duke told me about the rear-firing drivers was that this would impart some generic, Bose-like spaciousness to the recording, but that wasn’t the case—what I heard was the unique acoustic signature of the Concertgebouw."

What we do has evolved since Andrew wrote that in 2016.

Duke

Hiphiphan wrote: "After reading your second post, I realize you’re suggesting the use of additional drivers that are pointed at the wall in FRONT of the listener. This seems like it would be effective for enhancing the illusion of venue cues that came from the front of the venue. But it’s hard to imagine that this creates the feeling of "envelopment," since the reflections are coming from in front of the listener."

Duke responds: My speakers are designed to be used with a lot of toe-in, like about 45 degrees, such that their axes criss-cross in front of the listener. This correspondingly "toes out" the up-and-back firing drivers, so their energy reflects off front wall and/or side wall, and ceiling, before reaching the listening area. And that energy continues to reflect around the room so it arrives from multiple directions, assuming the room isn’t overdamped, though the strongest reflections are those from the front half of the room. You can see an example in the first photo at this link. The stands have an up-and-back firing coaxial driver:

https://parttimeaudiophile.com/2019/06/17/new-gear-from-audiokinesis-and-resonessence-labs-t-h-e-sho...

Hiphiphan: "Two other quick questions if you’ll indulge me:
1. What issues arise from simply using two sets of speakers (one in front, one behind), both playing the identical signal from a regular, two-channel recording, but with the rear set of speakers positioned further away?"

Duke: As long as the rear speakers aren’t too loud, that stands a good chance of being beneficial. If possible, position and/or orient the rear speakers so that their mids and highs arrive at the listening area at least ten milliseconds behind the output of the front speakers. Sound travels slightly more than one foot per millisecond.

Hiphiphan: "2. What about near-field listening? If the speakers are very close to the listening position, almost creating a headphone effect, it seems like might work to create something close to envelopment."

Duke: In my experience nearfield listening can give excellent clarity and imaging, but you still need the reflections delivered from all around to produce envelopment.

The worst possible direction for reflections to come from is the exact same direction as the first-arrival sound. In that situation, they tend to be interpreted by the ears as coloration. This has been established by controlled blind listening tests. So the worst direction for the ambience cues on the recording to arrive from is directly from the speakers.  In a nearfield setup the idea is to be close enough to the speakers that they are much louder than the in-room reflections, which does not promote envelopment.  When the ambience cues on the recording are delivered from many different directions by the in-room reflections, that’s when they have the best chance of conveying envelopment. In fact multichannel music done right uses the surround speakers to ensure the delivery of the recording’s ambience information from many different directions.

I have experimented with optimizing the arrival direction of the additional reflections, and with optimizing their arrival time.  I found (to my surprise) that the arrival time matters more.  

Duke

Hiphiphan wrote: "I have the Raidho D3.1 (I purchased them used; I’m not wealthy). Is the SuperStand, which contains the back-firing driver, compatible with a floor-standing speaker such as this?"

Duke replies: Very nice speakers!!

I have not tried adding extra rear-firing energy to a wide-pattern speaker like your Raidho’s. So at this point I’d have to say, I don’t know yet. I can think of arguments both ways, but such arguments pale into insignificance compared with the certainty of actually trying it. I hope to find out some day.

(The Sonus Faber Aida, their current top-of-the-line model, uses what looks like a rear-firing mini-monitor. The Sonus Faber loudspeaker [a previous top model introduced in 2009] also used a rear-firing mini-monitor. So it MIGHT work well with your Raidho, but I’m not sure... to a certain extent it depends on the "voicing" of the Raidho.)

Hiphiphan: "And how does The Swarm Subwoofer system fit in (or is it not compatible with the SuperStand)?"

Each SuperStand incorporates a passive subwoofer, in the top half of the "notch", so a pair of them are essentially one-half of a Swarm.

Duke