Pros and Cons of Sealed Listening Rooms

[Blackmorec]

A sound wave of any frequency is alternating pressure and rarification so bass doesn’t pressurise a room, it energises a room, the energy being in the form of soundwaves. The key to any room is to be able to ‘convert‘ those sound waves to another form so they don’t hang around too long and interact too strongly with the fresh sound waves that the speakers are injecting into the room continuously.
Natural sounds decay at a certain rate. If the room’s decay is too fast it will sound a bit dry and anechoic whereas too slow may sound unbalanced, boomy, lumpy and lose PR&T, with a lot of detail obscured.

 

[Blackmorec]

we aren't reproducing concert halls in our home, gents.

Friend of mine set up a home theatre system with a pair of Avantgarde Trios, 3 Unos and 7 subwoofers! We watched a Tina Turner Concert....with a last mighty drum beat the concert ended and my very first thought was about the crowd and getting out.

 

[kach22i]

When that thick double glass door shut you could feel the music everywhere , it was like the whole room was filled with energy .

I have experienced the exact same thing at a stereo store many years ago.

It was like an On/Off switch.

This reminds of a quote I've been reading lately.

http://www.linkwitzlab.com/index.htm

What you hear is not the air pressure variation in itself
but what has drawn your attention in the streams of
superimposed air pressure variations at your eardrums

An acoustic event has dimensions of Time, Tone, Loudness and Space
Have they been recorded and rendered sensibly?

 

[Alrainbow]

I think most all have sealed but not for better sound but isolation. It’s not just if I’m playing loud it’s o need a quite room. I think sonically a sealed room is better too it allows for the speakers to compress the room. Like on-a needle drop does.

 

[Al M.]

Well, again because "pressurized" is nonsense, I can explain this easily. Al's speakers have a simple first order crossover. They can produce bass articulately but they don't have a proper BSC crossover to balance them out for the room. So in order to mate well with the tweeter you end up with a bit of baffle step loss. When Al keeps the room closed it helps add a bit more gain to the woofer's octaves.

Except that I am not just talking about monitor bass, but also bass of larger speakers and subwoofers. In addition, throw in midrange and treble.

And you are right, 'pressurized' is probably not the right word, especially when it comes to the entire frequency range. 'Energized' may be a better term.

 

[Folsom]

Except that I am not just talking about monitor bass, but also bass of larger speakers and subwoofers. In addition, throw in midrange and treble.

And you are right, 'pressurized' is probably not the right word, especially when it comes to the entire frequency range. 'Energized' may be a better term.

Energized sounds fine to me. I just don't like the myths around speakers, that say sound pressure level from one speaker is more than another at the same frequency and same sound pressure level - to claim pressurization from the same thing is just as silly.

 

[Ron Resnick]

I built a dedicated listening room in 2015 using Acoustic Frontiers to design the room acoustics. The following is a summary of what was done. My audio system sounds amazing in this room, especially compared to the open FR where I used to listen.

The media room acoustic "foundation" consists of an isolated wall system comprised of 130 Kinetics IsoMax clips attached to 1-1/2" furring strips nailed to CBS blocks on all four walls. 440 linear feet of 25mm hat channel is supported by the isolation clips. R-11 open faced fiberglass (3-1/2" thickness) fills the empty areas between the CBS walls and drywall. Soundboard XP damped drywall is attached to the hat channel. Acoustic sealant seals the areas between the top, bottom, corner areas of the damped drywall.

The ceiling utilizes Soundboard XP attached to the ceiling joists. The media room attic has R-38 fiberglass insulation. A knee-wall with attached R30 fiberglass insulation separates the media room attic and the original structure interior attic area.

Acoustic Frontiers incorporated my existing Rives Audio ceiling "clouds" and using room dimensions and frequency measurements specified the interior room acoustic products and locations. The acoustic design creates a flatter frequency response; lowers the room reverberation time; and provides bass trapping. Clarity, soundstaging, and imaging are all improved while keeping the room as live as possible.

. . .

Very interesting, Len! Thank you for giving us the details!

What are the dimensions of your room?

How far are your speakers into the room away from the front wall?

How far is your listening position away from the rear wall?

 

[213Cobra]

I have never heard a live performance in a sealed acoustic space, except for being present in a recording studio, and even then... I've been in the primary and secondary symphony halls in a few dozen major cities, including Boston's venerable Symphony Hall (where I had a share of season tickets for 10 years) and none of them were anything close to being "sealed." Nor did they sound sealed. They were all big, leaky, breathing venues, chock full of ornamentation and people. Acoustically they leaked like sieves, and that's how it should be.

I've lived in open plan houses all of my life, excepting time spent in dorm rooms in college. Sealed and built rooms generally sound unnatural to me, compared to the basic traits of live music performance. Further, I've never heard a "perfect" room nor acoustic space. They are all anomalies. I agree, "pressurized" is a misnomer for what speakers do to a room. "Energize" is perhaps better. A sealed room energizes differently from one that is open to adjacent spaces. But since most music is not heard in sealed spaces, reproduction in sealed spaces can sound unnecessarily synthetic. I have other reasons also for not isolating hifi from the main living environment, but even if I were a hermit, I'd rather not listen in a sealed room. Let the house have its living effects. Optimize through placements and other not-insanely-obsessive tuning effects, and have at your music collection.

If you are listening to anything recorded in a studio with multi-tracking, high-count-multi-mic'ing, and not all the musicians present for simultaneous performance, you are not listening to an event. It's a synthetic result of an artistic process that bears no resemblance to live music. It's what we have to do. Listen to roughly pre-1962 recordings and almost everything not symphonic after 1968 and the difference in immediacy, camaraderie, and volubility are quite often stark. Hard to find after 8, 16 and 32 tracks became go-to.

Music recording techniques have persistently attempted to transcend the sealed room, from Capitol Records' reverb chambers 30 feet below street level, to digital reverb. If you listen to a classical recording captured in a performance hall, it will have a signature, but it won't be the signature of a sealed room. Do you need a sealed room to hear the signature of one what wasn't sealed? That's really the question posed. My answer is not only no, but that trying for a sealed room is likely counterproductive.

Currently, I have two listening spaces. The primary one is ~21'x14x8.5'. Speakers are on the broad wall. Facing the speakers, the right wall is bounded. The left wall is 50% unbounded. The wall behind the speakers is 70% bounded. The wall behind the listener is entirely bounded. The secondary listening space is 22'x11.5'; the ceiling is canted 12' to 8'. The speakers in that area are on the short wall. Facing the speakers, the right wall is bounded. The left wall is 70% bounded. The wall behind the speakers is bounded. The rear wall is 70% bounded. In both cases lots of acoustic energy escaping the immediate listening space. Since both rooms have normal life functions outside of hifi, the systems have to reside within some practical placement limits. And I wouldn't have it any other way.

Phil

 

[spiritofmusic]

Phil, my experience is the opposite. In retrospect I could never get my Zus to sound full or warm in my old 1000 sq ft/13,000 cub ft space. About 70% glass on front wall, one Zu side bounded, the other unbounded. Rear wall opening at mezzanine level to open bedroom, half open at grnd level to kitchen, 30x27 expanse concrete ceiling.

Combination of opening and other nooks/crannies and only one spkr w side reinforcenent, and the twin satans of extensive glass and concrete, left my sound impossible to dial in.

Now with a dedicated sealed space, the sound has phenomenally improved, and is totally predictable in how I improve or inhibit it w subsequent changes.

The other reason for a dedicated space. My choice of music, and exploring cats/cables/tubes toxic combination Lol.

 

[213Cobra]

My guess, Marc, is that your space isn't really sealed, but it's bounded. In any case, with a 30' x 27' space you needed much more power, or you needed to refer back to the 1970s Double Advent System and deploy a Double Definition system, with appropriate amplification.

13,000 cubic feet simply requires more power than you used at that time. You needed something like a pair of Ampzillas or McIntosh MC601 or MC611. Your "sealed" room doesn't sound better because it's bounded on six "sides" -- it sounds better because you now have an acoustic space in which your choice of amplification and speaker can perform at a level relative to the room allowing you to have tuned the system.

Phil

 

[andromedaaudio]

Phil , who is actually living there
If spirit of music says is sealed ,, thats it

 

[213Cobra]

Phil , who is actually living there
If spirit of music says is sealed ,, thats it

It depends on what the meaning of "sealed" is. I've seen photographs. Bounded, I certainly believe. Sealed....I am skeptical. -Phil

 

[spiritofmusic]

Phil, most likely you're right. I'll have to Google "Double Advent System", sounds intriguing.

Yes, I had a multi level curse of a nearly square space, 30x27, lots of v hard reflective surfaces and minimal soft furnishings, and lack of power (going from 25W 845 to 80W 211 did not decisively improve energising that space).

Interestingly, my new space is the same floor area (18x48 as opposed to 27x30), but only half the volume. So, I'm still gonna call it for my space having the advantages of less reflective surfaces (zero glass or concrete, 70% of flr carpeted), and fully symmetrical layout re Zus to side walls, only one lobby space (20' behind listening space).

Whether my bilateral symmetrical descending eaves helps or not on paper, in practice they also seem to be a boon.

Ron made a good point when he visited some 2.5 yrs ago. My synergy of 80W 211s and 300W Class D subs in this room is an almost perfect match for this kind of room to be fully practical w triodes fully energising it. He would never have said that w the same amps and spkrs in my old room, ostensibly the same flr area but twice the volume.

 

[213Cobra]

Phil, most likely you're right. I'll have to Google "Double Advent System", sounds intriguing.

Yes, I had a multi level curse of a nearly square space, 30x27, lots of v hard reflective surfaces and minimal soft furnishings, and lack of power (going from 25W 845 to 80W 211 did not decisively improve energising that space).

Interestingly, my new space is the same floor area (18x48 as opposed to 27x30), but only half the volume. So, I'm still gonna call it for my space having the advantages of less reflective surfaces (zero glass or concrete, 70% of flr carpeted), and fully symmetrical layout re Zus to side walls, only one lobby space (20' behind listening space).

Whether my bilateral symmetrical descending eaves helps or not on paper, in practice they also seem to be a boon.

Ron made a good point when he visited some 2.5 yrs ago. My synergy of 80W 211s and 300W Class D subs in this room is an almost perfect match for this kind of room to be fully practical w triodes fully energising it. He would never have said that w the same amps and spkrs in my old room, ostensibly the same flr area but twice the volume.

Volume trumps square footage.

Circa 1974, when the Advent Loudspeaker was the 2nd most popular speaker in the world by unit sales (Dynaco's A25 was #1), it was recognized back in the birthing days of "high end" as a speaker that could be the basis of a highly credible system if you got creative. Getting creative meant giving it more scale and, depending on amplifier, more effective efficiency. The Double Advent System entailed setting up four Large Advent Loudspeakers stacked vertically in a tall, woofer-tweeter-tweeter-woofer configuration or laid down on the long side and stacked for a tweeter-out/tweeter-in config each side. The Advent was an 8 ohms speaker, so if you wired in parallel you could take advantage of SS amps doubling power into 4 ohms, and if you wired in series you could go tubes with Julius Futterman OTL amps that doubled power into 16 ohms. Sweet! And for a given SPL, each driver was operating at a lower distortion. Some people bought the speakers with something like an SAE 2500 for Pink Floyd, and a pair of Futterman monos or an Audio Research D76A for nuance.

For a speaker that started rolling off about 13kHz and had fairly prodigious real bass in that time without a sub, it was very effective, if a little bulky. I was in the business then and sold many systems in this config and ran it myself for a short time.

Absolute Sound ran a review of this configuration, with Harry's enthusiastic endorsement so Double Advent System became a label of sorts.

Phil

 

[spiritofmusic]

Sure Phil, well the new room is literally half the volume of the old. If I had installed the system as you would have in our chapel, in our shared living space, I'd be contending with 2x the volume of my old space (that was already too much for 80W triodes on Zus) and 4x the volume of my new dedicated room.

 

[213Cobra]

Sure Phil, well the new room is literally half the volume of the old. If I had installed the system as you would have, in our shared living space, I'd be contending with 2x the volume of my old space and 4x the volume of my new dedicated room.

Everything is a compromise. I noted that "sealed" rooms sound less natural to me. Under your circumstances I might have decided to take that penalty in order to retain ability to drive speakers with a cluster of preferred amplifiers. Or maybe not. One doesn't know until one is confronted with solving the problem and making the best of the situation. -Phil

 

[spiritofmusic]

Sure Phil. Maybe in my old space I'd have toyed w the 170W Nat Magmas triodes. Maybe I'd have gone for something like Musical Fidelity Titan SS monoblocks. Maybe Ampzilla might have homed into view.

Most likely I'd have gone to horns to enable me to stick w tubes in a 10,000 cub ft space. Certainly my experience w AG Duos around that time was wholly positive. I certainly would have kept my eye out for any new interesting horns alternatives. I would also have seriously considered Apogees, but the power demands in this space would likely have put me off.

I am confident of one thing...now I have 20/20 hindsight w my A/B experience of that room and this. And that is, I never would have got an acceptable result in that room w anything less than the best horns, the best triodes, and a stackful of room treatments/rearranged layout (ie book shelves added to create a side wall for unbounded spkr, heavy drapes, large rugs, serious bass trapping). Only then could I find the right energisation/saturation AND less room interaction.

 

[LenWhite]

Very interesting, Len! Thank you for giving us the details!

What are the dimensions of your room?

How far are your speakers into the room away from the front wall?

How far is your listening position away from the rear wall?

The listening<->speaker is setup in a near field position:
D3s are 59" front wall<->speaker front;
115" center<->center;
3.5" toe-in;
105" speaker<->listening position;
56" rear absorber<->listening position.

Note: updated measurements of current room positions.

 

[sbnx]

Hello everyone.

Nice of Ron to post an interesting topic of discussion. I have had both an open and closed room. My prior house had a big open floorplan that opened to the 2nd story. I had Wilson Maxx 2's in there with no acoustic treatment and the bass was great (no modes etc). However, the positioning flexibility was always a compromise due to domestic considerations and thus getting soundstage depth never happened and the noise floor was quite high with things like the refrigerator, AC, dogs barking etc. After visiting a fellow audiophiles dedicated/treated room I knew that I needed one. So, I built a house and had a dedicated room acoustically designed. I have been in there since 2016. As it is dedicated I have complete flexibility with listener position, speaker placement and room treatments. The noise floor is very low (<30dB) and I am able to get incredible dynamics, soundstage and presence.

The left to right symmetry thing Mike mentioned in a previous post is important and hard to achieve in most living spaces as they are almost always asymmetric. I also think that the more space you can get from the wall behind the speakers then the better. This is also hard to do in a non-dedicated room. But, I recently have this some thought when I was setting up a demo system for LSAF in my living room. I was struggling to get good sound and had an epiphany moment. I will put this in the next post in case someone got bored with reading the above stuff and just wants to cut to the chase.

 

[sbnx]

So it is funny how we get locked into thinking a certain way. You know you always walk into a room and the stereo is setup on the far wall with the listening seat somewhere near the door. Well my epiphany moment was to turn this upside down. I took a bunch of my "spare" gear and setup a system in my living room. But instead of setting it up against the wall (by this I mean with 3+ feet between the speaker and the wall) like I did before I set it up with the seat out into the room several feet from the wall and the speakers with their backs to the opening to the room. See pic. The idea is that I got left to right symmetry and the speakers have a mile of space behind them.

Now admittedly this is not exactly going to please most non-audiophile partners. However, the results were fantastic. That old speaker form the 90's and a pair of subwoofers were amazing. Just something to think about.