John Sayers' Design Forum

John Sayers' Recording Studio Design Forum

A World of Experience
Click Here for Information on John's Services
It is currently Sun Nov 17, 2019 6:08 pm

All times are UTC + 10 hours




Post new topic Reply to topic  [ 343 posts ]  Go to page Previous  1 ... 16, 17, 18, 19, 20, 21, 22, 23  Next
Author Message
PostPosted: Mon Oct 07, 2013 3:07 am 
Offline
User avatar

Joined: Wed Jan 27, 2010 1:14 am
Posts: 246
Location: London (England)
Ok, I will follow your and Stuart's advice to remove the extra sorbothane around the box (NOT the one that is lying on the inside, between the box and the speaker !?).

Actually I already started and it was not a good start… both the MDF panels cracked !! :cen: :horse: :cen: !!!
I'm gonna take the rest of the day away from "that" place :evil: and come back with more calm tomorrow.

Just one last question if I may:
if the box needs to be essentially part of the whole structure (screwed, glued, kept as firm as possible…), then there is NO point in stopping both the first plywood layer and the finishing MDF layer a few mm away from the box either, right?
I might as well have them both touching the speaker box, as that too should contribute to the overall rigidity and it's nonetheless way easier to build… (I don't recall where I saw the advice around the forum about leaving that small gap there - I did followed it as it seemed a good idea at the time, but at this point I'm not sure anymore)

Right, I'm gonna have a few drinks :snack: :snack: , spend my time with my wife and two lovely daughters :love: , and let's hope for a better day tomorrow.
As I will start from scratch again I will make that mother even more rigid… actually if you have any other tip to improve resonance problems @ low frequencies…I'm all ears !!!!!


Grazie !


Simo

_________________
http://www.slipwaystudio.com/


Report this post
Top
 Profile  
 
PostPosted: Mon Oct 07, 2013 6:43 am 
Offline
Senior Member
User avatar

Joined: Thu Aug 21, 2008 10:17 am
Posts: 11984
Location: Santiago, Chile
One thing you could do first, Simo, is to do a REW test of the room, and see if there are any signs of resonance in unexpected places on the graphs. If REW can't see them, then you certainly won't be able to hear them! :)

The more I use REW, the more amazed I am by two aspects: 1) It's ability to drag out tiny details and show them clearly, and 2) It is free! I never have figured out how the best darn acoustic tool out there is zero cost, while it does so much more than other tools that I paid good money for! I'm relying on it more and more...

So do a quick test with REW, and post the MDAT file so we can take a look at it.


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.


Report this post
Top
 Profile  
 
PostPosted: Mon Oct 07, 2013 4:34 pm 
Offline
Senior Member
User avatar

Joined: Sat Mar 29, 2003 12:26 am
Posts: 2073
Location: Netherlands
Hai Simo,
I just browsed through your latest updates and I too am impressed with your craftsmanship. Cheers on that, mate!

Now, about your resonance problem. Dealing with low-end pulse frequencies, like a heavy kick, is a burden. Making anything "floating" is not that easy. Just putting rubber, foam or whatever "soft" material under an object doesn't make it float. You need to create a spring that is about 10% loaded to make it active. If the material is to hard it won't compress and just flanks. If it's to soft it'll compress too much and flank just the same.

To test your set-up. Take that piece of rubber you've put UNDER you speaker and place it on a flat surface.
Measure the height of the rubber (6mm right?) Now, place your speaker on top of the rubber. Again measure the height of the rubber, see if it compressed. Optimal is 10% so the height should now be about 6mm-10%=5,4mm. That way you know it is compress about 10% and therefore "loaded".

I'll bet the rubber isn't compressed at all, it's to rigid and your speaker-mass is just too low. There's your problem.

Now, finish that lemon and start crackin' !


Report this post
Top
 Profile  
 
PostPosted: Mon Oct 07, 2013 5:57 pm 
Offline
User avatar

Joined: Wed Jan 27, 2010 1:14 am
Posts: 246
Location: London (England)
Hi Stuart,

unfortunately the damage is done already, just because I'm an idiot and act impulsively as per usual…my italianism kicking in I guess :-)…dismantling the front MDF panels I broke them…both!! would you believe that??!! :evil: I was soooo cross ( to use polite term)!

Thus, since I'm at this stage I'll go ahead and take off the plywood layer too (which should be much easier to remove) and the insulation in order to expose the box.
Then I'll remove the sorbothane around the case, throw it as far as I can :mrgreen: and re-frame tight around it.
It does make sense to me what you're saying about building a three leafs structure the way I was doing it, so I'm gonna correct that before it's too late.
Then after I'll put back the new MDF panels I'll make an acoustic test to see where I'm at.


(p.s.) Thinking back to what I was asking above and answering my question by myself, I don't think it should a problem if the plywood layer is touching the box, as this is already screwed to the structure below (which the plywood is part of anyway), so there is no point at all to keep those separated….the only thing de-coupled from the overall soffit structure should just be the speaker, which has the sorbothane layer around it doing just that ---> Mass (speaker) + Spring (sorbothane) + Mass (rest of the soffit) - full stop!
…. so in theory, as long as nothing else is in contact with the speaker (bridging the two Masses) the de-coupling should be maintained




Ro - thanks a lot for your post !

"10% compression load" in order to work effectively… I've heard about this already…probably from you too before…it's just managed to find its way out from my little brain…argghhh :evil: !!!

Having gone so far with the build, there is no sense in ignoring this resonance problem pretending it doesn't exist just because it's frustrating having to re-do it…otherwise I know I'll regret later down the line, when to intervene would compromise the rest even more.


!! right, back to square one - wish me luck… and patience :-)

_________________
http://www.slipwaystudio.com/


Report this post
Top
 Profile  
 
PostPosted: Mon Oct 07, 2013 7:39 pm 
Offline
Site Admin
User avatar

Joined: Mon Jan 27, 2003 12:46 pm
Posts: 5418
Location: Australia
Oh Simo - All I suggested is you remove the sorbothane around the speaker and replace it with MDF - that wouldn't involve altering anything else.

_________________
John Sayers Productions

If this site helps you build your studio please use the Donate button.


Report this post
Top
 Profile  
 
PostPosted: Mon Oct 07, 2013 8:46 pm 
Offline
User avatar

Joined: Wed Jan 27, 2010 1:14 am
Posts: 246
Location: London (England)
I know I know John, don't worry :thu:

it's just that removing the rubber underneath the box would have been impossible as it was sandwiched between two layers of ply screwed together
Attachment:
IMG_2781.jpg
so I had no choice really
…actually, it turned out that even the sorbothane at the top and at the sides of the box was not easy to pull out…I kid you not, I even had to use the wrecking bar in two occasions as it got totally sticked to the box ! (that material IS quite sticky)

…and I'm already at this stage anyway
Attachment:
IMG_2929.jpg



me impulsive… remember? :mrgreen:


You do not have the required permissions to view the files attached to this post.

_________________
http://www.slipwaystudio.com/


Report this post
Top
 Profile  
 
PostPosted: Tue Oct 08, 2013 1:01 am 
Offline
Senior Member
User avatar

Joined: Thu Aug 21, 2008 10:17 am
Posts: 11984
Location: Santiago, Chile
Quote:
just because I'm an idiot and act impulsively as per usual…my italianism kicking in I guess


Hey there Mr. Impulsive Italian! Slow down a bit, and wait for answers to your posts! :) I sort of understand the "Italian" thing, though: not because I'm Italian, but because I live in Latin America, and the Italian blood runs strong in many people here too... :)

OK, so you don't run into the need for a wrecking bar again... How about if you put your front panels on temporarily at first, so that they can be removed easily a few times, just in case you need to make more changes, and only fix them in place permanently when you are satisfied that everything is working fine? For example, put just a few screws in each panel for the early tests, just enough to hold them tight, without any glue, finishing "plugs", decoration, or anything. Then you can take out the screws again if you need to get the panel off, without breaking it!

Same with the speaker boxes: Don't glue or nail anything, just use screws, so you can disassemble the box again if you need to.

You could even do some initial sine sweep tests without the baffles in place, just the speaker, to see if any vibrations is being transmitted to the frame.

Quote:
I have to admit I could definitely feel the kick drum while touching the baffle!
That might not be the resonance I was talking about, but rather just the front panel of the soffit vibrating naturally at some resonant frequency. How thick are your baffles (soffit front panels)? Also, is all of that framing very firmly braced? (I mean the framing that the front panel screws to.) Like John said, the soffit itself has to be very rigid, so nothing can vibrate naturally, so maybe running a couple more cross pieces behind your front panel would help with that, and also perhaps using thicker wood, or more dense wood for the front panel.

On the actual mounting of the speaker / box, there are two different approaches: I call them the "John Sayers" approach, and the "Barefoot" approach. There's a discussion on the forum somewhere that they had about this a while back, but I can't find it right now. John's approach is to hold the speaker and box extremely rigidly to the rest of the soffit, and keep everything very heavy, massive and rigid so it cannot vibrate. Barefoot's approach is to decouple the speaker and/or box from the front baffle, so it floats, allowing the speaker a little room to vibrate freely, but heavily damped with rubber, and not allowing it to contact the front baffle at all. But he still uses John's approach for the rest of the soffit: Rigid, solid, heavy. It looks like you were trying to do the Barefoot system, and that can work too, but only if the speaker/box really is floating. I've also see Barefoot do his system two different ways: one is to put the front baffle on one rigid frame with the speaker on a separate rigid frame, and the other is the way you are doing it, with a single rigid frame and rubber to decouple just the speaker. I haven't seen Barefoot on the forum in a long time, and I wish he were here to clarify his methods, as I might not be explaining it correctly, but that's what I've seen in his posts.

So, with what you have there in your room, at this point you can either go 100% with John's method (all rigid), or 100% with Barefoot's second method (the way you were doing it) but getting the rubber deflection right so the speaker really does "float". So that's the decision you should make first.

Now, as Ro mentioned, if you do use rubber in their to decouple the speaker, it has to be done correctly, to get the correct deflection so that the speaker really does "float", and that is generally in the range 10% to 20% deflection, depending on the type of rubber. I agree with Ro that your Sorbathane is probably not deflecting enough, since you have a very large surface area there but not all that much weight. So you might need to just use a few strips of Sorbathane cut to the correct width, rather than an entire large pad. Do the experiment that Ro outlined, to make sure you are getting at least 10% deflection in your rubber, and probably more like 15% to 20%. Check the specifications for the exact type of rubber you have (call the manufacturer for that), and keep within whatever range is correct. The specs should tell you what load you need to get optimum deflection (kg/m2), so if you weight your speaker assembly you can then figure out how many square cm of rubber you need, and cut it accordingly.

I'd guess that your 6mm rubber should probably be compressing down to about 5mm, in order to float correctly.

Quote:
it's just that removing the rubber underneath the box would have been impossible as it was sandwiched between two layers of ply screwed together
Ummmm.... if you screwed those together THROUGH THE SORBATHANE, then there is no decoupling at all! The screws are transmitting the vibration directly from plywood plate to the other, and the sorbathane is just sitting in the middle, as a spacer.... It wont float at all like that...

Quote:
!! right, back to square one - wish me luck… and patience
Patience more than luck! And put down that wrecking bar.... :)


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.


Report this post
Top
 Profile  
 
PostPosted: Tue Oct 08, 2013 3:49 am 
Offline
User avatar

Joined: Sun Nov 22, 2009 4:56 pm
Posts: 116
Location: Seattle, WA, USA
Hi Simo--

Sorry to hear about your frustration; I have definitely had too many of those moments myself!
Just to add my two cents' worth (or maybe less), here's a link that might illustrate what Stuart is talking about, where Nativeluv17 used only small squares of sorbothane, which presumably gave him the proper deflection.

viewtopic.php?f=2&t=11508&p=109443&hilit=durometer#p109443

In a conversation with tech support at sorbothane, this approach is what they suggested for my build, as well. They're quite helpful, and if you give them the weight and dimensions of your monitors, along with the thickness and durometer of the sorbothane you're using, they might give you a suggestion for the number of and dimensions of some smaller sorbothane pieces that might work better for you. You could then use REW to compare. Here's their web page:

http://www.sorbothane.com/blog/contact-sorbothane/

It might be worth a phone call across the pond....I hope today is a better day! :D


Report this post
Top
 Profile  
 
PostPosted: Tue Oct 08, 2013 6:04 am 
Offline
User avatar

Joined: Wed Jan 27, 2010 1:14 am
Posts: 246
Location: London (England)
Hi Stuart, I used screws throughout, no nails or glue…. the plywood came off with no problems, but the MDF, as it has a different consistency did not…also, I used quite big screws and perhaps that didn't help too…. lesson learnt :-)

I'm using a 18mm plywood and an 19mm veneered MDF (which is quite dense, definitely denser than the ply) on top of it, both screwed to the framing underneath.
The soffit was very rigid indeed, but this time around I'm making it even more rigid.

I guess in my confusion I was going with an hybrid approach….
(yes, I realised too that screwing the bottom of the speaker box with the plate below through the sorbothane was cancelling the decoupling I was trying to achieve! silly mistake !)

Your explanation looking at it in terms of Mass-Spring-Mass opened my eyes!
So this time, I excluded the extra layer of sorbothane outside the box but I am keeping the layer inside it, and I'm making the structure as solid as I can.
Attachment:
IMG_2934.jpg

Attachment:
IMG_2936.jpg



Hi Mark, thank you very much for your support and info !

I did ask for advice to the company I got the sorbothane from (www.lrcltd.co.uk), and after explaining what I needed it for, giving the measurements and weight and saying that I needed it to damp vibrations (I remember now that I did asked about the need of being compressed by 15-30%, following Brian (BriHar)'s kind advice (pag.8 on this thread), they got back to me saying that 5-6mm thickness should suffice for that purpose.

Thanks guys !!


You do not have the required permissions to view the files attached to this post.

_________________
http://www.slipwaystudio.com/


Report this post
Top
 Profile  
 
PostPosted: Tue Oct 08, 2013 10:51 am 
Offline
Senior Member
User avatar

Joined: Thu Aug 21, 2008 10:17 am
Posts: 11984
Location: Santiago, Chile
Quote:
they got back to me saying that 5-6mm thickness should suffice for that purpose.
OK, yes, but that is THICKNESS they are talking about: You also need to know how much AREA is right for the load you are putting on it.

Think of it like this: If it needs 1000 kg/m2 to get that 15% deflection with 6cm thickness, and your speaker weighs 1000 kg, then obviously you need one square meter of rubber, measuring 100cm by 100cm. But if you speaker weighs 100 kg, then you only need one tenth the size, which would be a piece measuring 10cm by 100 cm. And if your speaker weighs 10 kg, then you'd need a piece measuring one hundredth of a square meter, which is 10c, by 10cm. If you put your 10 kg speaker on one square meter of rubber, then it won't deflect 15%! It will only deflect one hundred times less, which is 0.15%!!! Nothing at all. So it won't float.

OK, I just invented all those numbers to make it easy to calculate: they are not real number at all! I just wanted to illustrate the math that you need to do. If you look at the thread that Bigsby linked you to, you'll see that Nativeluv used very tiny squares of rubber to decouple his speaker, not an entire sheet.

So its a function of thickness and area that you need to calculate. When you called the Sorbothane dealer, they told you what type to get (thickness), but they didn't tell you how much area of that you need.

I would call them again, tell them how heavy your speaker is, and ask them to tell you how much surface area you need to float that much weight, using the 6mm rubber they sold you. Then spread that amount of surface area around underneath your speaker. Then use the SAME area of rubber on each side of the speaker and make the surrounding box 10mm wider that the speaker, instead of 12mm wider (so you get the same deflection horizontally), then use the SAME area on top of the speaker as underneath and make the box 10mm higher than the speaker instead of 12mm higher, to ensure that you get the correct deflection in that direction too.

I would arrange the rubber as one thin strip under the full front edge of the speaker, then small pads arranged under the sides and back, until you get the right total area. Do the same up the sides and across the top. The reason for the thin trips around the front edge, is to get a good air-tight seal between the speaker and the box, to reduce low frequency "pumping" effects from forcing air in and out around the edge of the speaker.

Not sure if that makes any sense! It's not easy to describe it in words...


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.


Report this post
Top
 Profile  
 
PostPosted: Thu Oct 10, 2013 12:53 pm 
Offline
User avatar

Joined: Sat Dec 08, 2012 4:58 am
Posts: 42
Location: Italy
Hi Simo, thanks for posting, really nice work!!!

I'm currently building my room and now i'm scared about my soffits (they are also angled) as i'm not a carpenter :ahh:
i should rethink my design without soffits, maybe same as northavenue studio (designed by John) before i make mistakes!!! To do or not to do... :roll:

Anyway, any measurement yet???
How does it sound???

As always sorry for my english, i should include it in my signature! :mrgreen:
Greetings from Italy!


Report this post
Top
 Profile  
 
PostPosted: Thu Oct 10, 2013 5:26 pm 
Offline
User avatar

Joined: Wed Jan 27, 2010 1:14 am
Posts: 246
Location: London (England)
Ciao Finck! tutto bene?

No, no measurement yet…I'm currently re-building them…hopefully - all going well - they should be finished by the end of the week.

In terms of how they sound…. well, just by trusting my hears I was already extremely pleased with them even with my previous construction, which was a bit of a three leaf-structure (thus, for what I understand, it should no behave well at low frequencies)… I mean, I was literally laughing when playing back music that I know well through them... I noticed small details I never focused on before, plus I great stereo image and very well balanced low end.
Hopefully that would improve with the new construction which is way more solid than the previous one and without the extra sorbothane… we shall see :-)

Basically, all of this to say that I would give it a try building the soffit...
It's almost fun….If you don't have to do it twice !!! :twisted: :mrgreen:
I am Not a carpenter myself…actually I never build anything in my life before, but necessity got me here…just take your time!!… and I'd recommend to do a very detailed model with SketchUp… that FREE program will surely help to figure out any "strange" cut and to see in advance how it will look like


In bocca al lupo Fink !!


Simo

_________________
http://www.slipwaystudio.com/


Report this post
Top
 Profile  
 
PostPosted: Fri Oct 11, 2013 2:46 am 
Offline
User avatar

Joined: Sat Dec 08, 2012 4:58 am
Posts: 42
Location: Italy
Quote:
Ciao Finck! tutto bene?

Tutto bene, tu?

Quote:
I am Not a carpenter myself

Me too, but i'm not as good at it as you! :mrgreen:

I'm waiting for your next update! Bye! :thu:


Report this post
Top
 Profile  
 
PostPosted: Mon Nov 25, 2013 7:19 am 
Offline
User avatar

Joined: Wed Jan 27, 2010 1:14 am
Posts: 246
Location: London (England)
Hello all !

I'm moving at a snail rate especially comparing to some of you guys (sometimes you make me feel even slower :-)), but I'm nevertheless moving forward, so update time I guess…

… Update Part-1

first of all this is the updated speaker soffit, the MKII :-)
Attachment:
IMG_2938.jpg

Attachment:
IMG_2982.jpg

As planned I extended the superchunk above the speaker:
Attachment:
IMG_2985.jpg

filled in the cavity with insulation
Attachment:
IMG_2986.jpg

Attachment:
IMG_2989.jpg

rockwool between the framing
Attachment:
IMG_2990.jpg

plastic sheet layer and final black cloth cover
Attachment:
IMG_2998.jpg

Attachment:
IMG_3011.jpg


end of part-1...


You do not have the required permissions to view the files attached to this post.

_________________
http://www.slipwaystudio.com/


Report this post
Top
 Profile  
 
PostPosted: Mon Nov 25, 2013 7:28 am 
Offline
User avatar

Joined: Wed Jan 27, 2010 1:14 am
Posts: 246
Location: London (England)
… Update Part-2

Time to finish off and hang up the clouds.

First I placed a layer of a material called "batten' (following RJHollins' advice) which - along with the small wood strips - should help to avoid the insulation from sagging over time…
Attachment:
IMG_2733.jpg

On the part of the cloud that will be closer to the ceiling, I made the plywood backing flush with the framing, in order to be able to lift the cloud closer to the ceiling….my room isn't very high so I figured that every inch will help (I tried with and without it and the difference was very noticeable).
Attachment:
IMG_2734.jpg

rockwool and plywood back cover
Attachment:
IMG_2743.jpg

front view
Attachment:
IMG_2758.jpg

For the finishing layer I added a thinner (9mm) planned softwood all around to hide the screws, and stained it
Attachment:
IMG_2759.jpg



Exact same process for all the other clouds:
Attachment:
IMG_2837.jpg

Attachment:
IMG_2843.jpg

Attachment:
IMG_2954.jpg

Attachment:
IMG_2956.jpg

Attachment:
IMG_2968.jpg

Attachment:
IMG_2972.jpg

Attachment:
IMG_2973.jpg


end of part-2...


You do not have the required permissions to view the files attached to this post.

_________________
http://www.slipwaystudio.com/


Report this post
Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 343 posts ]  Go to page Previous  1 ... 16, 17, 18, 19, 20, 21, 22, 23  Next

All times are UTC + 10 hours


Who is online

Users browsing this forum: No registered users and 16 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group