AVS Forum banner
Status
Not open for further replies.
21 - 40 of 82 Posts

·
Registered
Joined
·
2,243 Posts
What are your thoughts on using a soft baffle wall. A few of us have been discussing the benefit of just have the front wall filled with insulation and the speakers flush with the face of the insulation. So no hard MDF wall - just the insulation (covered with AT material of course). My thoughts are that the absorption by the insulation would have the same effect as the reduction of reflections with a hard baffle, but the open faced insulation will provide much better bass / lower frequency trapping/absorption. It is much simpler, easier and cheaper than building a proper baffle wall.
We have done some internet searching and can't find any research or even any other in-depth discussions on this.
Thanks for your time and effort in helping out AVS Forum :)
 

·
Registered
Joined
·
4,030 Posts
@Peter Aylett I have a question about testing subwoofers. As far as I know of the 3rd party data-bass.com is where it shows full measurements in complete detail. I'm starting to see companies only providing basic measurements and not full shown measurements for consumers. What are your thoughts of testing methods beyond CEA and if compression and distortion will be included in that?
 

·
Registered
Joined
·
2 Posts
View attachment 3198911

Hello AVS!

Welcome to the Ask Me Anything with Peter Aylett!

An integrator of over 30 years and now a partner at HTE Acoustic Interior Design, Peter currently chairs the CTA/CEDIA R10 Standards Committee as well as one of its workgroups currently re-writing best practice for entertainment space/cinema/theatre audio design.

If you have any questions concerning industry standards for designing and setting up home theaters, or want the perspective of an experienced engineer then Peter is your guy to ask for robust answers that are highly detailed and product-agnostic.

This thread is now open, and will run until Friday, Nov. 26th! We can't guarantee that every question will be answered, but even if not, you'll still be seeing some interesting responses.

Looking forward to seeing your questions!

Welcome Peter!

All the best,
Dan
Hello Dan,

I'm planning to get a subwoofer for my Home theater system. My room is 284 Sq. ft/2,272 Cubic ft., and it will be open on one side. I'm really interested in SVS- PB 2000, but it's price point is higher. My budget is around $500, so can you recommend any other subwoofer with similar specs in that price range ? Thanks!
 

·
Premium Member
Joined
·
16 Posts
Hello Peter,

My home theater is 16'Wx24'L with two rows of 3 seats each. I have a wall on the left side and I installed heavy blackout curtains on the right side (no wall and two pillars). I've installed three 6"ng (2'x4') bass absorbers on the ceiling and alternate bass absorbers (6' - 2'x4') and diffusers (2D) on the left wall. I have a 6' (2'x4') bass absorber on the rear wall between Back Left and Back Right speakers and a diffuser (3D - 2'x4') on the outside of these speakers. On the front wall, I have a 6' (2'x4') base absorber behind the center channel. I'm planning to install corner bass absorbers sometime in the future.

Is there anything else I can do to improve sound quality in my room? Are curtains good enough or should I build a wall on the right side for better sound?
Also, when I build the riser platform (12'x6'x12"), should add holes of various sizes on the front (facing frontwall) and backside (facing backwall)?

Appreciate your advice. Thank you!

P.S. I haven't really measured the room at the moment as I want to do it once I install the riser platform with second row seating. But it sounds really good at the moment for what I've done. I have RMC-1L as a preamp and Parasound A51 and PS Audio M700 as power amps, SVS Ultras, and PB-16 subwoofer.
 

·
Registered
Joined
·
49 Posts
RP22 - Recommended Practice for Multichannel Audio Room Design
I see the concept of levels as a goal that you've specifically identified. Are there other overarching goals that are driving the development of RP22 and RP23 that you can share with us?

Level one is the baseline for what we feel reproduces a basic level of artistic intent.
Can we actually understand the artist's intent in a way that allows us to measure equipment against? Perhaps it's just me but the concept of an artist's intent seems too subjective for anyone else but the artist to ever truly understand. I feel I'm being too philosophical about this and would like to know if there's some science behind it.

As an example, we are likely removing Watts as a recommendation for both amplifier and speaker specifications, and replacing it with short and long term voltage capacity (At 2,4,6 & 8 Ohms for amps, and with an impedance curve for speakers).
That seems like quite the undertaking to get the industry as a whole to make those changes. How might such changes be facilitated or am I overthinking it?
 

·
Registered
Joined
·
14,018 Posts
Can we actually understand the artist's intent in a way that allows us to measure equipment against?
In this context, this means the artist created the material in a calibrated reference mastering studio. Chasing a similar standard Ed reference playback system lets the viewer see and hear what the artist saw and heard….what they INTEND audiences to see and hear….the “artist’s intent”.

That seems like quite the undertaking to get the industry as a whole to make those changes. How might such changes be facilitated or am I overthinking it?
I would love to hear more about this too but basically when selling into the custom installer marketplace, manufacturers will either share this data or be at a disadvantage. Another member of the working group has described it like the nutritional label on food. Failure to provide it will be a barrier to sales channels and markets.
 

·
Registered
Joined
·
240 Posts
… or want the perspective of an experienced engineer then Peter is your guy to ask for robust answers that are highly detailed and product-agnostic.
Here I go:
We have a living room, and I am intending on putting the 65” TV in front of the window in a table with a TV lift.
(Currently it is on the hearth above the fireplace)

The 2.0 is not in the room yet.
The sound is finally somewhat usable out of the LG OLED 65” with a lot of futzing around with various settings.
However I did order a used AVR preprocessor, which has arrived, but has not yet been set up.
I am intending on have the front left and front right go into the 2.1 system and using a fixed (marked) volume setting so that the AVR room correction can work. Then those two channels will go through the 2.0 side.

I picked up some wall mount surround speakers for the RR and LR, as well as a Center channel… which are from the same manufacturer as the 2.1 speakers.

I am intending on powering the LF and RF with the tube amp, and the center and surrounds with Class-D.

There is a sub with the 2.1, and i have another couple of 12 subs which I will make boxes for either as sealed or maybe 4th or 6th order bandpass.

I have access under the house, and a bunch of Neutrik XLR connectors and wiring, and chassis mounts to put into the floor in order to run signal wires closer to the speakers (under the floor).
Should I even consider 5.2.2 or 5.2.4 with the 11 foot high ceilings? And if so which?
What general wisdom should be paying attention to?

The Haus-Boss does not want it to become a home theatre room, so it will have to remain somewhat stealthy and tasteful.

We normal stream NetFlix from the TV or from a NUC as the source. The AVR-Processor will require the NUC (I think) to separate the audio(? And delay the video), but maybe the OLED outputs the ARC for the AVR-Processor to do its thing.

Kindergartener sketch (speaker location I am considering are marked in red, and the sketch is a bit lopsided… sofa and door are a bit further to the right hand side.):
Handwriting Rectangle Slope Font Parallel
 

·
Registered
Joined
·
30 Posts
1.
If you live in an area with a stable electric grid and very low danger of lightning strikes, how much should you worry about power? Just get whole-house surge suppression and call it day? Or should one look into isolation transformers, power conditioning, balanced power, additional surge suppression at the rack, etc?
If you live in an area with a stable electric grid and very low danger of lightning strikes, how much should you worry about power? Just get whole-house surge suppression and call it day? Or should one look into isolation transformers, power conditioning, balanced power, additional surge suppression at the rack, etc?
The only actual input into your system is power. I know many top private cinema designers who will ALWAYS use an isolation transformer on every project. The results will depend on -
1. How clean the power is coming into your home
2. What devices you may have plugged in creating noise and harmonics. Some switched-mode power supplies are very bad at this.
3. The sensitivity of the components you use to power issues

I would always use an AV-specific (as opposed to stuff made for the I.T. world) power conditioner/surge protector on racks of stuff purely for protection. I've never seen or heard a quality difference, but the peace of mind in terms of protecting expensive equipment is worth it. I HAVE, however, heard the sonic benefits of using AV specific isolation transformers on systems. Whatever you do, ensure that the product does not raise the impedance of the line and thus prevent power amplifier power supplies from drawing dynamic power.
 

·
Registered
Joined
·
1,173 Posts

I was pleasantly surprised by this video featuring Peter on HTE's philosophy to find such a strong parallel with my life's work working in technical and architectural acoustics development of form facilitates function in a team leadership capacity with top Italian architects Gian Enrico Fabro, Michele Bonan and my personal favorite Massimo Iosa Ghini, Italian Craftsmen are among the best in Europe although the Turks you will find have honed these fine crafts for much longer, but also in carte blanche collaborations with Zaha Hadid and Jacques Grange out of which the Inspiration for the prototype Dolby Cinema concept was sparked.

Peter and I also have similar life experiences when he mentions that one defective piece of equipment (in my case a stereo minijack which's cable was stapled by the drywall people in a remote never used 95 sq ft. reading Loft accessible only by a long narrow spiral staircase ) in a secondary zone can take down a job with a brilliantly performing cinema. That clicked, as it is the very same reason I stopped doing multiroom in 1999. Although I admit now being tempted to delve into distributed Atmos music.

Motivated by what I hear to be Peter's intent in his committees and what the Raison D Etre at HTE is I will share my findings and observations but also my objecting reservations, much of of which will sound conflicting and iconoclastic to many of the generally accepted (ie. THX 80 hz cutoff) in the hope that some of it sticks with his new committees that hopefully will espouse broader views moving forward.

I will thus post my mini manifesto of what constitutes a great immersive space and I look forward to his impressions.
 

·
Registered
Joined
·
30 Posts
How do I know if a speaker has SBIR issues, particularly my LCR front stage?

I was thinking of making 6” thick safe n sound acoustic panels and put them right behind each tower since there will be a small gap I can’t remove and even though this would push them out more, it should absorb reflections right?
SBIR (Speaker Boundary Interference Response) happens with EVERY speaker that is not soffit/flush-mounted. It occurs when the audio reflection off a surface returns to the speaker 180º out of phase thus creating cancellation at that frequency. As an example, the wavelength of 94Hz (around the frequency that gives a kick-drum its weight) is 12'. So, if your speaker is 3' from a back wall, the reflection at 94Hz will be 180º out of phase and thus result in a (partial) cancellation.

Get yourself an inexpensive USB Mic, and a free piece of audio measurement software and see for yourself if you are suffering from it, and if so, at what frequency.
Check the specs on whatever absorbing product or material to see what its absorption coefficient is at the frequency that you have an SBIR issue. 6" of conventional foam/fibreglass will have little effect at bass frequencies, but will totally absorb upper midrange/treble. Be VERY careful about using too much as you'll end up with a dead but still boomy room.

It sounds like your speakers are close to the wall, so any SBIR will be higher in frequency so 6" (if you have a problem) Will do the trick but again, take care not to reduce the RdT (Reflection decay time) at upper midrange/treble too much.
 

·
Registered
Joined
·
30 Posts
Why cant i change my tvs screen aspect ratio when watching 4K ??
For example if im watching something thats 2.35 2K i can switch it to 16x9 to fill the screen.
Yea yea i like it that way sometimes. :)
But if im watching something thats 2.35 4K i cant switch it to 16x9.
Tried on amazon 4K fire stick & 4K bluray....no dice.
You should always watch content in its native aspect ratio. if you stretch 2.35 to fit 1.78. you'll end up with everything distorted vertically. If you crop the picture to only show the middle part of the picture, you'll miss out on much of the beautiful work of the cinematographer.
 

·
Registered
Joined
·
30 Posts
A follow up question here:

In more and more newer designs, I see much less use of the typical bass traps (either OC703 triangles in the corner or various pressure based absorbers in high-pressure zones). Instead, the bass is optimized by placing seats and multiple subs accordingly and seat-to-seat variation and modes are close to being eliminated. (<80-100hz only though)

What is your treatment design principles when it comes to managing the bass in a home theater?
Yikes! This is a 3 hour seminar to discuss, not something I can describe here. The fundamentals, however, are -

1. RdT (Usually stated as an RT60 time) should be linear through the frequency range. Big bits of foam in corners may have limited effect on bass, but still absorb midrange and treble.
2. It's REALLY difficult to model a room for bass. The model depends on inputting the construction of the room in terms of a surface's impedance to bass. Good luck with that in a home, though with a REALLY expensive build it can be done. So, it's very difficult to predict the high pressure zones to use a pressure absorber, and the room's modal response to predict where seats should go.
3. We build rooms using a system that effectively turns every wall into a big broadband bass trap. The more depth we are given, up to around 15", the lower in frequency it's effective to. The construction is done in a way that does NOT over absorb mid and high frequencies so we end up with very linear RdT.
4. Multiple subs (locate in specific positions) - Usually 2 or 4 identical ones, works really well to mitigate modal issues. Lots of bass absorption combined with multiple subs delivers the best results and most flexible seating locations.
 

·
Registered
Joined
·
30 Posts
Every speaker in a room unless the walls are far away has SBIR....

I am curious where Peter prioritizes dealing with SBIR versus room modes, decay time, etc. and whether he subscribes to the approach of using in wall speakers (baffle wall design) as a way to remove SBIR from that direction?
If possible, I would always advocate baffle wall or flush mounting every speaker including subs. This eliminates SBIR, and also increases the efficiency at bass frequencies. Room modes and decay time/impulse response go hand in hand. The energy in the room must be dissipated somehow. If there is little to absorb bass energy, no amount of clever DSP will deliver good bass.
 

·
Registered
Joined
·
1,201 Posts
If possible, I would always advocate baffle wall or flush mounting every speaker including subs. This eliminates SBIR, and also increases the efficiency at bass frequencies. Room modes and decay time/impulse response go hand in hand. The energy in the room must be dissipated somehow. If there is little to absorb bass energy, no amount of clever DSP will deliver good bass.
A question here for clarification please. Admittedly with no absorption there is no decay. And the increase of broadband damping a la Gedes or as perhaps you utilize is wonderful:
We build rooms using a system that effectively turns every wall into a big broadband bass trap. The more depth we are given, up to around 15", the lower in frequency it's effective to. The construction is done in a way that does NOT over absorb mid and high frequencies so we end up with very linear RdT.
We have seen that decreasing the amount of energy put into a system at a problematic pesky frequency can result in purportedly acceptable steady state response for bass frequencies. Further that ostensibly we respond favorably to steady state magnitude smoothness in the bass region, see Olive and Toole.

Does this mean that, for example, the Harman SFM and subsequent PEQ is just clever DSP and does not work ?

edit : added subsequent PEQ — duh :)
 

·
Registered
Joined
·
1,028 Posts
@Peter Aylett

1) Are corner bass traps a myth, are you better of using DSP and 4 subwoofers, 1 in each corner?
2) In contrast to the above, isn't it true that the less DSP, the better, the more physical acoustic treatment, the better?
3) Can diffusers be recessed into a wall, or does the whole wall need to be recessed for this to work, covered by cloth?
4) Would you rather place diffusion on rear side walls instead of the rear wall, with bipole surrounds on the rear wall, 5.1?
5) Any benefit having 2" absorption behind a non-AT fixed frame screen, mounting the screen flush or 1-2" from the wall?
6) How important is it to seal off an archway leading out to another room, can this be done with somewhat of a thick cloth?
7) Do you know any acoustically transparent carpets that could be used covering pits in front of the screen?

About question #1, Anthony Grimani advocates using bass traps in power corners, and ceiling/wall corners, is this a bad approach, is it a general rule of thumb within the industry to use these, if not, could you explain why, I think lots of members could use the correct information on this, appreciated.

Thanks!
 

·
Registered
Joined
·
96 Posts
The room where I listen to a lot of music has a door that leads into the furnace room. Although the door is weather-stripped, lower pitch (under 500hz) sounds come through the door. What material could I attach the to the back (furnace side) of the door to deaden the sound?
 

·
Registered
Joined
·
1 Posts
What should I clean my preamps jacks with if they’re dirty?

Also,

ifni have a preamp, and amp, a phono preamp, a equalizer, a sound processor and a passive isolating device and a receiver what would be the best way to plug them?
 

·
Registered
Joined
·
2,659 Posts
Hi @Peter Aylett

AVS Forum is, of course, full of members who worship at the altar of deep bass, done right. I count myself among them.

I am curious about the whole topic of infrasonic bass and seek your opinion on a couple of things:

1. If cost is no object, what's roughly the lowest frequency (in Hz) that's worth chasing after for home theater, in your opinion?

2. While there are lists that cover deep bass in movies, so we know where to find it, I am wondering how much content below 16 Hz is truly intentional? How about single-digit Hz content, already very rarefied, how much of that is intentional? And if it is intentional, under what conditions are frequencies like that being mixed and monitored? How does the viewer know they are honoring "artist's intent"?
Mark these are great questions that I’m sure many of us have wondered about as well and hope Peter gets a chance to offer his opinion.
 
  • Like
Reactions: Mark Henninger

·
Registered
Joined
·
15,154 Posts
WG1 is currently working on -
RP22 - Recommended Practice for Multichannel Audio Room Design (Though this title will likely change). This will be the definitive recommended practice on the design of the room and system for private cinema/theatre/screening room/media room design. We hope to finish by February next year.
RP1 - Performance Facts. A recommended practice for manufacturers to give us engineers the objective facts we need to make informed specification decisions. As an example, we are likely removing Watts as a recommendation for both amplifier and speaker specifications, and replacing it with short and long term voltage capacity (At 2,4,6 & 8 Ohms for amps, and with an impedance curve for speakers).
RP??? - When RP22 is done, we'll move onto a recommended practice for the measurement and verification of audio systems.
WG3 is currently working on -
RP23 - Recommended Practice for Video System Design. Both projection and flat panel.
Will these "recommended practices" documents be made available to the general public once finalized?

My belief is that these works, when complete and looked at as a whole, will shift the conversation away from 'what brand or product do you recommend', and towards performing engineering design to ensure consistency of performance BEFORE then specifying the correct product to meet the engineering need.
I hope you succeed as the consumer is bombarded with subjective product reviews online and offline, pushing them in the opposite direction – unfortunately successfully so.
 

·
Registered
Joined
·
30 Posts
We read a lot about the benefits of dual subwoofer vs one subwoofer in home cinema. Most modern AV receivers and audio processors have two sub outputs, for using dual subwoofer.

But I have seen a lot of guys that are using more than two, 3, 4, 5 even 6 subwoofers and not in large rooms but in regular size rooms. Moreover, they also buy the largest and most powerfull subwoofers they can afford.

My question is, when it comes to number and size of subwoofer, when do we stop? Is it too many and too big something that is not only unnecesary but it is actualy detrimental?
There are multiple strategies for delivering great bass in rooms. This is another one of those questions where the answer could be a one week long course. When we say 'great' bass, we want -
  1. Great seat to seat consistency. Every seat has a similar (Identical is a futile exercise) experience.
  2. Deep - Can reproduce everything on the content material, intentional or not.
  3. SPL - To maintain the same SPL when you halve the frequency requires four times the amount of air to be moved. This is a combination of cone/piston size and excursion. Keep this in mind - If our LCR speakers can deliver a constant 105dB at the reference position, you need to add +10dB for the LFE channel, if you are using the subs for bass management then add another 5dB, and if in your calibration you want a +10dB contour as subwoofer frequencies then add another 10dB. That equals 130dB.
  4. Low distortion. Included in this is thermal compression (as more power gets put through a voice coil, it heats up. As it heats up its resistance increases)
  5. Good impulse response. Often called haow 'fast' a sub is. This is a combination of sub design, and room acoustics.
In any speaker design for bass, you are balancing efficiency vs max SPL vs frequency extension. For instance, a sealed subwoofer will go lower than a ported one, but will not generally be as efficient.

So, to answer the question. Multiple subs (This is a great reference on the subject - https://www.harman.com/documents/multsubs_0.pdf ) are used for -

  1. If positioned correctly, multiple subs can be used to effectively cancel out some room modes thus giving better seat to seat consistency.
  2. Multiple subs working together deliver more SPL. If each sub isn't working as 'hard', then they are likely (depending on the design of the sub) to be able to deliverlower frequencies at a similar SPL.
  3. Some people believe that it's best to bass manage speakers to subs located close to the speaker being bass managed.

It is said that smaller subs are 'faster' than larger ones. This is not inherantly true, but unfortunately there are some inexpensive large subs that perform poorly. It's MUCH harder and more expensive to make a large sub than a small one.

When adding more subs, ask yourself why you are doing this. Usually, I design rooms with a minimum of two, and preferably four identical subs. These reproduce LFE and are used for bass management. For higher end projects, I'll add an infra-sub or two.

Yes, adding more subs ust for the sake of it CAN be detrimental. In every case, though the modal response of a room is extremely difficult to predict, it is possible to predict SPL capacity and LF extension.
 
21 - 40 of 82 Posts
Status
Not open for further replies.
Top