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Emmett Scully
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Building a listening room

Hello,

I want to have a go at making and selling boutique speakers, so I'm going to build a listening room. I wanted to ask the knowledgable people here for advice.

The goal is to have a room which will allow for the clearest evaluation of speakers. To this end I want the walls to be reflective, but for there not to be any issues with the sound which would mask the sound quality.

The internal dimensions in feet are 14x22.5x36.5
The walls and floor will be concrete.
I'm thinking the roof could just be galvanised sheets.

My question is; how can I get a good in room frequency response, i.e. not too rolled off at the top end.

This needs to be cost effective and non-resonant.

Maybe Plywood over the concrete would even the response, and then the right paint over that might improve matters further.

Any thoughts?

Tim Link
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Emmett Scully wrote:
Emmett Scully wrote:

Hello,

I want to have a go at making and selling boutique speakers, so I'm going to build a listening room. I wanted to ask the knowledgable people here for advice.

The goal is to have a room which will allow for the clearest evaluation of speakers. To this end I want the walls to be reflective, but for there not to be any issues with the sound which would mask the sound quality.

The internal dimensions in feet are 14x22.5x36.5
The walls and floor will be concrete.
I'm thinking the roof could just be galvanised sheets.

My question is; how can I get a good in room frequency response, i.e. not too rolled off at the top end.

This needs to be cost effective and non-resonant.

Maybe Plywood over the concrete would even the response, and then the right paint over that might improve matters further.

Any thoughts?

I plugged your room into an online RT60 calculator: http://www.csgnetwork.com/acousticreverbdelaycalc.html

By choosing unpainted concrete for the walls, carpet on pad for the floor and an acoustic tile suspended ceiling it gives a reasonably even 0.3 second RT60 for the range between 125Hz and 4000Hz. You could lengthen that if desired by not covering the entire floor with carpet. RT60 will get longer as you go below 125Hz so some bass traps in the corners could lower that and keep the room sounding properly bright and clear. If you paint the concrete it becomes more reverberant because you seal the pores. It can't be undone once it's painted. You could instead add painted plywood panels as needed to add reverberation. Ideally those could be curved to make polycylindrical diffusers for first reflection points.

geoffkait
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Whatever you decide to do, it

Whatever you decide to do, it will pay to think about it a great deal as it could be irreversible should you find out later what did was either wrong or you discovered later there’s a better way to do it. If you had know before you could have supported the entire house on springs or roller bearings before it was built.

No matter how much you have in the end you would have had even more if you had started out with more. Law of maximization

Kal Rubinson
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[quote]The goal is to have a
Quote:

The goal is to have a room which will allow for the clearest evaluation of speakers. To this end I want the walls to be reflective, but for there not to be any issues with the sound which would mask the sound quality.

The internal dimensions in feet are 14x22.5x36.5
The walls and floor will be concrete.
I'm thinking the roof could just be galvanised sheets.

I do not know what you mean by "mask the sound quality."
1. Do you mean that the room should have no influence on the sound quality? If so, you want an anechoic chamber.
2. Do you mean one that will accentuate differences among speakers? That seems to be your target but, if so, what you will hear in this room will be nothing like what the speakers will sound like in a purchaser's home and, therefore, it will be a misrepresentation of the product.
3. Why are you not targeting an optimised acoustic environment to minimize (not eliminate) reflections and modal influences?

Tim Link
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Concrete walls in the showroom

A concrete room will have a different sound than most people will experience in their wood framed, drywall houses. It would be good I think to put 2x4 framing up against the concrete, with insulation between the 2x4s and drywall over that, to make it sound more like a typical home environment. That room is pretty big, so maybe even 2x6 framing as it will only cost you about a foot in room width and depth. Bass absorption would be good because you're still going to have that concrete wall behind the framing so the room is going to contain bass for a longer time than a typical home. You can achieve bass absorption with the drywall by using the ASC IsoWall system. Disclaimer - I work for ASC!

geoffkait
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How to map the room for acoustic anomalies

The road to audio nirvana is paced with cobblestones and it can often be a very bumpy ride. Before setting on on the room treatment journey it’s best to have a very good idea what you’re dealing with first, where and what type of acoustic problems a given room has. In order to do this you have to have out the room in terms of sound pressure peaks. These peaks are produced by a number of things, not only the room dimensions, while music is playing and cannot be determined in a Willy Nilly fashion since these peaks won’t show up while music is playing. These peaks are akin to having powerful speakers pointing at you from all around the room interfering with the pure signal of your real speakers.

So, what you need to map the room for SPL peaks is a CD or LP a that has test tones on it and select one to play on REPEAT while you map out the room in 3 dimensions using a SPL meter and while the volume is set to some average value so you can find peaks that are 6 dB or higher than the average SPL in the room. You should be able to find a great many peaks in the room 6 dB or higher. For a given speaker set up this is the place to start treating the room. As you refine the room acoustics you probably want to re p-locate the speakers to more optimum locations using the speaker set-up track on a test CD.

Sound Pressure Peaks on the room can be treated using a number of devices, including but not limited to, Corner Tunes by Room Tune, Echo Tunes, Skyline diffusers, Tube Traps, Acoustic Lens, or homemade Helmholtz resonator(s), crystals (for room floor in corners, walls, tube traps and glass windows,, tiny bowl acoustic resonators, constrained layer dots for walls.

manunkind
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Corner Tunes by Room Tune,
geoffkait wrote:

Corner Tunes by Room Tune, Echo Tunes, Skyline diffusers, Tube Traps, Acoustic Lens, or homemade Helmholtz resonator(s), crystals (for room floor in corners, walls, tube traps and glass windows,, tiny bowl acoustic resonators, constrained layer dots for walls.

You forgot to mention that one has to be wearing a tinfoil hat while using the crystals etc. Playing Aleister Crowley backwards can also help.

geoffkait
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Hey, whatever turns you on.

Hey, whatever turns you on.

Scott Strother
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The Listening Room

This topic is very interesting. In loudspeaker placement,
I have plans to incredibly maximize not just frequecncy balance, but soundstaging (ESPECIALLY)! Wall seating, with ottomans, and almost NO freestanding furniture save for a coffee, console table, and curio cabinet. All the equipment will be located entirely in another room. I'm primarily an analog, FM listener and I still make extensive use of cassettes, as well as MDs on occasion, and in the process of converting all of my analog to it. Good Luck

geoffkait
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When placing speakers the

When placing speakers the only reliable and accurate method is using the speaker placement track on the XLO Test CD or similar. The more diffuse your system sounds out-of-phase the more focused and correct the sound will be when playing in phase. As you work on your room acoustics over time you need to recalibrate the system using the speaker location track since things change, the better your room acoustics become the more easily you can hear the sound coming at you from all around the room on the out of phase track. In the beginning you will most likely have difficulty hearing what is described on the track since your room is in relative disarray, acoustically speaking.

Other methods provide only local maximum results for speaker placement. Move a little listen a little without benefit of the XLO speaker placement track is like trying to solve x simultaneous equations in x + n unknowns.

As Bob Dylan sez at the end of his albums, good luck to everybody.

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