Stuart's Insanity Studio: Design phase

[AVare]

OK: the angular quest continues!
So they say that tilt angle can be up to 20 degrees for this speaker, the EBU says 10, André says 7, and I still can't find any reference to research as to WHY these angles exist!
But this tilt angle thing has me intrigued....

Still searching.... somebody must know the reason for limiting speaker tilt angles!!!!

Unfortunately I am intrigued also. We have our quest!

Andre

[Soundman2020]

Yup, we sure do have a quest! I'm googling everything I can think of, but coming up with very, very little. Most of my searches lead me right back here, or to the Genelec web site, or to the EBU document.

But I just found another tantalizing twist to add to the mix, from the SAE web site, which I understand John Sayer wrote:

http://www.saecollege.de/reference_mate ... eakers.htm

John has a diagram there, showing how to do it, and the speaker angle on that diagram is roughly 12 degrees! (I loaded the pic into SkecthUp and measure the angle...)


7, 10, 12, 20.... Take your pick!

(But nobody says why, or what terrible consequences will occur if you angle it too much.)

[AVare]

(But nobody says why, or what terrible consequences will occur if you angle it too much.)

I identified that. Changing frequency response of the ear.

I am glad you found 12 and 20. I still can not find the 7! I think the problem is that the pinnae varies so much from person to person that any guideline/spec is broad in its appropriateness to individuals. Al I have found are general "it varies with height."

Andre

[Lou]

Hey Stuart - Congratulations to you my friend. That is the fastest graduation to Senior Member Status I've ever seen, just over thirteen weeks!

Seriously though, whilst I'm clearly not in Andre's league, I would suggest that the critical issue here, is to ensure that the front of your monitors (and soffits of course) are exactly perpendicular to your ears in the mix position/sweet spot. If you recall, Studiopeople took very accurate measurements of me ergonomically, to guarantee my soffit angle is just that. For what it's worth, said angle is of course governed by monitor height (which in turn is somewhat dictated by the height of the gear in front) and my height when sat in the 'sweet spot' It turned out to be 12 degrees and the room sounds awesome!

Hope this helps and the best of good luck with your project.

Regards,

Lou.

[Soundman2020]

Hey Lou, thanks for the kind words!

"Senior member", huh? WOW! I'm humbled! How did that happen? I guess you get it automatically at 300 posts or something? ´Cause I'm sure as eggs not acoustically qualified for such a dignified title!

In those same 13 weeks I think I've gone from absolute studio acoustics ignoramus to thinking that maybe I can actually do this right, due to all the incredible, invaluable help I'm getting from you guys and from this forum. In that same period I've also gone from "MAM? what's MAM?" to being concerned about the exact angle of my soffits, and whether or not I should cast them in concrete. It's been a bumpy ride, and I'm sure there are plenty more bumps to come (especially after looking over your thread), but you have to admit that life ain't gonna be boring if you decide to start building a studio!!!

Anyway, on the angle thing: thank you very much for your input, your angle, and the comment on why yours ended up at the angle they did. So at least we know that it is possible to go to 12 degrees without the world coming to an end, and it can still sound great, but I sure wish I knew WHY! What André says about the pinnae makes perfect sense, and I found some research by the BBC where they basically discovered that some people are very good at determining the source of sound in the vertical plane to within a few degrees, while other people were hopeless, but beyond that just doesn't seem to be much research on-line about this at all. I don't like doing things for which there is no solid theoretical research with long scary equations, graphs with lots of squiggly lines, tables with strange symbols, and things like that.

My room is going to be so tiny and therefore incredible bad acoustically, that I want to make sure I do everything I possibly can to minimize the "badness", but based on sound research and reasoning (no pun intended).

So, my plan right now is to make the soffits adjustable. I don't have the details worked out 100%, but my idea is to "hinge" them across the lower edge somehow, at about 1m above the floor (probably by supporting the lower edge of the panel in some kind of rubber-lined trough), then poke a couple of threaded bars through the concrete, close to the top edge, with a nut welded on the outer end of each bar (the end facing the studio) and the other end running through a nut fixed into the steel frame behind the panel.

That way, by rotating those nuts on the studio side (with large washers behind them, of course), I'll be tightening or loosening the threaded bar, and thus adjusting the angle of the soffit. Then I can test everything empirically at several different angles, to see what effect the angle has, before I decide on exactly where I am going to fix it permanently. If I design it so that I can adjust the angle from 7 degrees to 20 degrees, then I have all my bases covered!

(This will also give me a bit of "fudge factor" if I screw up in my measurements and calculations of ear height, speaker height, etc. According to my long, on-going relationship with Murphy, "fudge factor" is definitely a good thing...)

Any comments from anyone on whether this "adjustable concrete soffit" idea will work? Good idea? Bad idea?


- Stuart -

[jlemon]

Any comments from anyone on whether this "adjustable concrete soffit" idea will work? Good idea? Bad idea?

Great idea, if you can design and implement it in such a way that the adjustable parts don't resonate... And it has to be strong enough to adjust a concrete (50kg maybe?) box... Great idea...

PS: You haven't answered my question concerning FRP and slat resonators...

[Soundman2020]

Rough idea for "Stuart's Original Patented Adjustable Concrete Soffit Panel":

Sketchup file here:

http://www.digistar.cl/images/Adjustabl ... t-S01.html

And pics, first a general overview, then a close up of the proposed mechanism. Just a rough outline still. Gotta work on the details....


- Stuart -

[Soundman2020]

(But nobody says why, or what terrible consequences will occur if you angle it too much.)

I identified that. Changing frequency response of the ear.

Yup, I know you said it, and it makes perfect sense. What I'm trying to find out now is how bad it will be at each angle, and if it is a "one size fits all" thing that affects all humans the same, or if it might differ drastically from person to person, as suggested by that BBC report I mentioned. What I'm really trying to establish is how much difference is there, and what am I sacrificing, if I go from 7 degrees to 9 degrees, for example, or 12 degrees, or 20 degrees, or whatever. Is it linear progression? Will it mean that my mixes will not translate well as they will be overly bright, and can I compensate with EQ? etc. That's what I'd like to find answers for, and just like you I'm coming up blank on that quest!

I am glad you found 12 and 20. I still can not find the 7! I think the problem is that the pinnae varies so much from person to person that any guideline/spec is broad in its appropriateness to individuals. Al I have found are general "it varies with height."

That's what it looks like: it varies from person to person, and with height, and level, and frequency. If you are interested, the BBC report that mentions this vaguely is "Research Report Number B-085", dated (get this!) "1965/18"!!! More than 40 years ago. Real up-to-date stuff! (But still very valid, despite the age). The title of the report is "Recent work on the effects of reflectors in concert halls and music studios".


- Stuart -

[Soundman2020]

More views of possible "SOPAC" soffit design...

[AVare]

Thanks for the lead on the BBC report. Section 3 was of interest, but not what we looking for right now.

I can't comment on your moving panel design. It seems to be addressing a problem that does not exist. Speakers are designed to give best response on axis. The angle to achieve that is known from the design. Adjustments are not necesary.


Do some research! Set up your speakers outside and move them up and down. Good luck.

Andre

[Soundman2020]

What I though was interesting about that report was that many people are not able to determine source position on the vertical plane, while other people are able to do so fairly accurately. I know it's not really what we are talking about here, but I'll bet it is related somehow. I'll bet that your comment on how sound impinging on the pinnae from different angles causes frequency response to change depends on the shape of the pinnae of different people. Yeah, I know it doesn't have much to do (directly) with figuring out soffit angles, but I'm wondering if that might be WHY there is a limit to the angle: I wonder if it is related to the best-case scenario of people who have good sense of directionality vertically? For example, if the very best "direction finding" ears don't get confused by a seven degree angle, then for sure the rest of us wont get confused either. And maybe a ten or twelve degree angle still does not affect them too badly, while a 30 degree angle does? I guess they are just more sensitive to those frequency change clues than the rest of the population.

I'm just speculating, of course, purely out of curiosity, trying to understand why different people propose different limits.

And regarding my adjustable soffit design: Yeah, I agree that its best to get it right in the design stage, but I figure that this method will actually give me a chance to try things out, and will also make it easier to mount the soffits in the first place, ad has the additional advantage that I can take the panels off again easily, without having to destroy my wall in the process, if I ever need to get access behind the soffits / speakers for whatever reason. Don't forget that in my room, there is a rain water gutter that runs along that edge of the roof, more or less directly above the soffits, and even though I plan to seal that extremely well, I'll bet Murphy will figure out how to surprise me in the future, with a well-placed leak...

So there are several reasons why I'm seriously considering the adjustable soffit. The last reason is simply construction accuracy: I can make up for slight imperfections in construction, just by twisting a bolt. Building those frames with compound angles is going to be complicated anyway, but this gives me an easy way to build them and stil be accurate.

And in the worst case, if the adjustment mechanism turns out to be a bad idea, I'll just remove it and fix the panels in place permanently, without it. So it can't hurt and might turn out to be useful.

- Stuart -

[AVare]

I agree with your speculation. BTW the BBC document are a gold mine of information. If someones wnat so to know abut the Coles ribbon mic design, there is an engineering report from the fifties (still current production equipment!) on its design. Just one example.

I had forgotten about the rain gutter. It makes more sense now.

Andre

[Lou]

Stuart - Buddy, I'm so (up to a point) out of my depth here, Andre's got you covered. Whilst I absolutely love the ingenious nature of your idea, you're (IMHO) trying to reinvent the wheel here somewhat. Your hunger for specific knowledge backed up with laboratory tests, and, certified data to prove it, is nothing short of commendable.....................(There's music in here somewhere as well I seem to remember! Was it Dbmaj or Bbm? Dominant or sub mediant? Medium 16 shuffle or straight 8ths?)

Now get this, my friend - go sit in your den and occupy your favourite chair. Next, ask your partner to prepare your favourite CD, then go grab a beer and sit back in said comfy chair. Then place a blindfold over your face and ask your partner to support your hi-fi speakers on as many books (or similar) as are needed so that the tweeters 'line of sight' exactly matches the vertical position of your ears. Finally, sip favourite beverage (with blindfold on) and at any given point ask partner to place a glossy magazine under the back edge of the speakers (monitors) to tilt them forward. Said person cannot walk in front of monitoring to help you out!

This must be done whilst the music is playing preferably loud enough 'to get into' and, as smoothly/soundlessly as possible............................................Can you tell when the monitors got moved by 10 degrees?

Hope this helps, dude

Kindest regards, and very many thanks for the kind words concerning my build. - All the the best to you and yours.

Lou.

(PS - The controlled environment of your new studio will bear no relation over this test, since, your monitors will then be in that controlled environment).

[WayneD]

I was going to suggest something not so involved but Lou beat me to it. So did Avare. Trying something without all the expense and labor seems to make the most sense. I can see why you'd want to try the adjustable wall. There is just easier ways to "skin a cat" so to speak.
Thanks for all the links Stuart. You've been a big help. Many thanks for sharing your quest for knowledge.

W

[Lou]

........................................Nice one Wayne.

Thanks btw.

Regards,

Lou.