[DonS]

Hey everybody!
I'll soon soon be able to begin building my permanent dedicated listening room. I've done a bit of reading and I'm very interested to know if anybody has ever listened to music in a golden trapezoid room. Please post with your comments if you have. Good or bad, I'd like to know what you have to say as I'm somewhat considering building one of these rooms.

[FullRangeMan]

Cardas site had an useful analysis some time ago.
Its a very desirable room format IMO.

[JLM]

I believe Cardas called the shape "Golden Trapagon" (something like 10ft x 16ft in the front, 12.72ft x 20ft in the back, and 26ft deep).  Don't know if any research has been done on this shape, but looks good.  I built a "Golden Rectangle" 18 years ago (8ft x 13ft x 21ft) that I use for audio listening in the front and an office in the back.  It's equipped with ten 2ft x 4ft GIK 244 panels (six full rangers at front/side/rear first reflection points and four bass traps stalling the front corners) and three tall bookcases to act as casual/adjustable diffusers on the side walls.  And the room is well/practically insulated.

The "Golden Trapagon" would be difficult to build, suggest building it inside a larger rectangle.  Recommend reading Floyd Toole's "Sound Reproduction" (both editions) to learn how sound (bass in particular) behaves in-room.  Toole worked for the Canadian Research Council for decades before retiring out of Harmon International (JBL/Revel).  He was a well respected/leading acoustician. 

Bigger is better, up to many practical limits.  Rectangles are well researched/understood but admittedly not the best shape. 

[planet10]

...a golden trapezoid room...

Is that a rectanglular box with golden ratios?

It has been broadly shown that the only thing special about this is that it uses irrational numbers. Many room shapes (rectangles) using other irrational numbers.

But the biggest single thing that any really good room will have is a sloped/vaulted ceiling.

dave

[WGH]

...I'd like to know what you have to say as I'm somewhat considering building one of these rooms.

I'd say you have a lot of reading and math to do before building a non-standard room. Floyd Toole has done the math but it's still not plug-and-play.

Loudspeakers and Rooms - Working Together
by Floyd E. Toole, Ph.D.

"Some have argued that there are advantages to using non-rectangular rooms. The thinking behind
this is that, by reflecting sounds in directions other that directly back towards a parallel surface, the
development of standing waves will be inhibited, and diffusion will be increased. The reality is that sloping
the room boundaries has a substantial effect on the modal structure, but the modes do not disappear. In fact,
the magnitudes of the variations in sound pressure throughout the room remain much the same, but the
frequencies of the various modes are changed in an unsystematic manner, and the nodal lines are
repositioned in a manner that is not always obvious [3,4]. Simple predictions of the kind just discussed are
no longer possible, and one must resort to finite-element analysis or models in order to predict what might
happen in practice. This is a serious disadvantage in some situations, as will be seen, for example, in
Section 2.2..."

The article above plus more room and loudspeaker articles by Floyd E. Toole, Ph.D. are available for free in the Acoustics Circle
https://www.audiocircle.com/index.php?topic=58304.0

[WGH]

I designed and built high-end custom entry doors for 40 years. Usually my customers trusted my judgement and gave me carte blanche (within reason) to design and build an entry that would compliment their house, church or commercial building.

The one thing I learned is that I had to start with the most un-glamorous, boring part of the job first which was "what is hardware?" Once I knew the physical hardware specifications and dimensions, then I could design the door. Not everything will fit perfectly if you wait until after the door is built.

The same goes for a music room. Base traps? Diffusers? What type: Flat or Adjustable PolyFlex? Ceiling: Smooth or Cloud Diffuser? All this ugly stuff can be hidden if the room is designed around them otherwise you will end up with all sorts of stuff randomly stuck on the walls.

I don't have a dedicated listening room so will have to differ to others with more knowledge, A/V Room Service looks like a good place to start
https://avroomservice.com/


I made the mesquite veneered entry doors for the Casas Barrier Chapel in Tucson, AZ. The interior is an excellent example incorporating non-parallel walls with ceiling clouds for sound diffusion. Notice the tall bases of the light sconces are also curved sound diffusers.

[planet10]

The same goes for a music room. Base traps? Diffusers?

If the room and the system are well designed no need for band-aids like bass traps.

dave

[FullRangeMan]

Is that a rectanglular box with golden ratios?

Its not the usual equilateral rectangle with all sides having the same dimensions.
Its pictured below, the room front side are smaller, Cardas approach to rooms are all Golden Ratio based, what is good and avoid resonances modes:

The normal rectangular room is below as seen on the Cardas site:

Other images from the Cardas site for speaker placement:

[howburger]

I believe Cardas called the shape "Golden Trapagon" (something like 10ft x 16ft in the front, 12.72ft x 20ft in the back, and 26ft deep).  Don't know if any research has been done on this shape, but looks good.  I built a "Golden Rectangle" 18 years ago (8ft x 13ft x 21ft) that I use for audio listening in the front and an office in the back.  It's equipped with ten 2ft x 4ft GIK 244 panels (six full rangers at front/side/rear first reflection points and four bass traps stalling the front corners) and three tall bookcases to act as casual/adjustable diffusers on the side walls.  And the room is well/practically insulated.

The "Golden Trapagon" would be difficult to build, suggest building it inside a larger rectangle.  Recommend reading Floyd Toole's "Sound Reproduction" (both editions) to learn how sound (bass in particular) behaves in-room.  Toole worked for the Canadian Research Council for decades before retiring out of Harmon International (JBL/Revel).  He was a well respected/leading acoustician. 

Bigger is better, up to many practical limits.  Rectangles are well researched/understood but admittedly not the best shape.

My room is very similar to yours (8x12x20). I purchased absorption treatments from ATS Acoustics(2’x4’x2”). They have a calculator on their site to determine the number of panels to achieve a reasonably ideal RT60 time of .5 seconds. This number turned out to be 10-11 panels, right there with yours. I used the mirror method to determine where to put each panel, compromised slightly for aesthetic purposes(WAF). There is a 8’x2’x1’ bass trap built into the front edge of the ceiling with a flush covering of black felt. Walls were all double dry walled with about 12 cases of Green Glue. I don’t remember what the decibel reduction was but I think after 15 years, the green glue may be short circuiting a little bit. The room sounds good to me, with all the typical audiophile descriptions. The never ending learning process now has me rethinking the absorption/diffusion situation. I think there may be a lot to be gained by proper placement of the combination of the two. I use dipole speakers and I have not read anything that conveys any consensus of a proper alternative to the traditional live end/dead end theory.

Harold

[JLM]

To be honest the GIK panels haven't done much in my room, but have worked wonders elsewhere.  The room EQ built into the Buchardt A500SE hub helps more than Dirac did. 

I'd avoid simple room ratios, like 2:3 (8ft and 12ft).  The original "Golden Rectangle" was the "Greek Rectangle" to reduce echo in their stone temples and to be aesthetically pleasing.  Since I don't listen at high volumes I didn't bother with double drywall or staggered studs.  And frankly I didn't trust my contractor enough to follow details that they didn't understand.

[planet10]

Thanks Fullrangeman.



A trapezoid is a 2D shape with 4 sides. A Golden trapezoid is also a 2D shape.

What this shape is called i do not know. Not a trapezoidal prism (ceiling and floor parallel)

dave

[howburger]

To be honest the GIK panels haven't done much in my room, but have worked wonders elsewhere.  The room EQ built into the Buchardt A500SE hub helps more than Dirac did. 

I'd avoid simple room ratios, like 2:3 (8ft and 12ft).  The original "Golden Rectangle" was the "Greek Rectangle" to reduce echo in their stone temples and to be aesthetically pleasing.  Since I don't listen at high volumes I didn't bother with double drywall or staggered studs.  And frankly I didn't trust my contractor enough to follow details that they didn't understand.

Yeah, my room was an existing downstairs 2nd master bedroom. I did the sound isolation to benefit the sound in the room, not to keep it from leaking out of the room. All of the efforts that went into taming and isolating the room were done at the same time so I can’t say what helped the most. I can tell you that the most noticeable difference was when, in 2017, I purchased all new source equipment and amplification; Sonic Transporter Ethernet server, Microrendu Ethernet player(Roon) with a linear power supply with lots of capacitance, Schiit Yggdrasil dac and 2 monoblock Hypex Ncore NC400 class d amps. Between the low noise floor of the room and the very low noise floor of the new equipment, I could listen at lower volume with the same satisfaction that previously took much more volume. It is amazing what a quiet room does. Haven’t emailed Danny yet but I will be contacting him to arrange an audition at his place in September to listen to his NX-Oticas and NX-Tremes.

[DonS]

Thanks for all of the great replies everyone. I appreciate all of the added input. It'll help me make a sound decision on how to proceed.