John Sayers' Recording Studio Design Forum Archive

Cool!

For anyone following the thread and not having a clue what is going on with the above cryptic conversation: Frank ran into an issue cutting the Sorbothane for isolating his speakers, as the calculator provided by the Sorbothane company is not correct: it gives you the wrong answers. When Frank cut it to the correct size, it did not compress correctly. Several of my customers have reported this to me recently, so now I would suggest that nobody should bother even trying with their faulty calculator.

So I gave Frank some tips on how to proceed anyway, ignoring what the calculator says and doing it with math instead.

- Stuart -

Can you share the formulas you're using to get correct results?

Personally, I have just thought to use 1 1/2" thick chunks where possible and make sure to get 20% deflection through trial and error.

Greg

Hi Stuart,

Make sure to read my whole string of emails to avoid confusion. I was spitting them out as I ping ponged through my trials!

To the rest of the crowd: Sorry for not being more informative guys. As soon as I get the soffit work done, I'll be back to normal levels of content!

It's all a little confusing, but I think I understood... I sent you an e-mail, to double check....

- Stuart -

And I was starting to feel like I had a handle on things

Can you share the formulas you're using to get correct results

Hey Greg. Sorry I missed your post: The actual equations are on their website. You can download the engineering design guide in PDF, and they are on the first few pages, with examples and graphs on the rest of the pages. Not too complicated... just long, boring, lots of calculations...

But I'm working on a simple way to still use the calculator, by adjusting with a "correction factor". Right now it seems that you need to adjust your area to be only 92% of what it really is, and put that number in the calc. Or stated another way, divide the number that the calc gives you, by 0.92 to get the REAL area you need. So if it says you need 20 cm2, then make that (20 / 0.92) = 21.75 cm2.

Still working to confirm that this correction factor is true for all cases... Sorbothane is non-linear, so it might not work out that simple...

Also, this only applies to their V2 calc: the V1 is also wrong, but in a different way.... Right now I have them both open with the exact same data in each, v1 says the deflection is 23.75% and the frequency is 16.8 Hz, V2 says the deflection is 19.3% and the frequency is 12.9 Hz So there's MAJOR differences here! Don't trust the calculators. I'll be talking to them probably tomorrow, to see what they say. Frank already made contact.

Personally, I have just thought to use 1 1/2" thick chunks where possible and make sure to get 20% deflection through trial and error.

That's one way to do it, but you need a very accurate method for measuring, and it takes a while to do that! And you need to account for the fact that a lot of the vibration in a speaker is in the front-to-back direction, not so much up-and-down.... Plus you have to account for the fact that speakers are not weight balanced: the center of gravity is not over the center of the bottom panel with most speakers, so it will tilt one way or the other if you don't compensate.... And for pads that don't have weight on them, only pressure, or a combination of weight and pressure, you can force them to have 20% deflection WITHOUT having the correct pressure... and you can also force them to have the correct pressure WITHOUT having the correct deflection! - in both cases the frequency will be wrong, and it won't isolate properly... (Don't ask... too complex to explain here, and I'd be giving away too much proprietary stuff anyway...)

- Stuart -

Back to you sir!

Ping----pong! Check your email. Time to get out your pet octopus, and start assembling that sucker!

- Stuart -

I have a bit of a problem. lets see what we can do about it....email sent.

Ready for the next Phase! Email sent!

We have a winner!

Update! Frank has assembled his speaker enclosure boxes with the speakers inside them, and they worked out great! We had to adjust some of the mounting process, because of the error in the Sorbothane calculator (as mentioned a few posts back), but with the correction factor that we figured out, it all came together nicely.

Photos of the assembly process, and the final outcome:
Note that some things are hidden in those photos on purpose, as there's some parts of how I do this that I'm not prepared to reveal in public yet. Maybe one day. Those folks who take the time and think it through carefully might be able to figure it out for themselves. One reason I don't want to reveal it, is because it is complex to get right: Frank can testify to that! What you don't see here is the ten pages of instructions that I wrote for him, on how to put it all together, and you also can't see the headaches he went through to make it happen. You really can't see it in the photos, but that's precision carpentry and assembly, right there. It is all accurate to 1/64"...

But happen it did, and the effort will be well worthwhile!

Nice work, Frank!

Next up: mount them in the soffits, and put baffles on them...

- Stuart -

more headaches! messages sent...

Hmmmm... thinking about what to do about that.

For those following the thread, Frank discovered some symmetry and plumb issues with his soffit framing. I'm trying to figure out if it is serious, and if so, what to do about it...

- Stuart -

On another note.....I'm looking at the desk and wondering if I can make it bigger? I would follow the outline of the room of course. I could conceivably add more surface area for mix gear and what not.

For everyone out there.....This is the desk in question. I will be building it from scratch. I want to push out in the directions shown.