SIMO Studio - Construction Phase

[Soundman2020]

I'm planning of using a 3mm plywood for the core, and 50mm insulation on the sides

John does NOT recommend plywood for the cores: he recommends a very low density, soft fiber board, called "Homosote", which is made from recycled paper: It's the type of board used for bulletin boards, that you can stick push-pins into easily. I don't think plywood is going to work correctly.

Following the distance recommended on John's design, i.e.150-200mm (I assume not from the center of the hangers but from its edge, well not a huge difference anyway),

As far as I know, John is talking about on-center measurements.

I measured that I would manage to place just three of them in there!
It seems a bit of a waste of space to me, what do you think?

I may be wrong, but I reckon they will work OK. You also have to line the inside of that box (the walls, floor and ceiling) with thick insulation, so there will be a lot in there. And if it doesn't work well, then you can always take the hangers out and fill the whole thing with insulation, as a superchunk

But John is probably the best guy to comment on this, as he has years of experience doing hangers, and seems to be the person who understands them better than anyone else. Maybe PM him with a link to this thread, and ask him to comment.


- Stuart -

[simo]

Thanks for your quick response Stuart, always informative and detailed.

Strangely I can't find anywhere the Homosote in this part of the world, or any equivalent material light enough for that purpose - don't know why ?… so, due to this I was just following Glenn's advise (on this thread @ pag.6 3rd post from top) about using 3mm lightweight ply as an alternative (which it's very light indeed), and will be there just to have something to attach insulation onto …but I'll keep searching for a low density fibre board - actually, anyone in UK knows where I can find it at all?

Thanks for the "on-center" clarification Stu, and yes I will line the inside with insulation

What you say about trying first with hangers and if doesn't work well convert it in superchunk makes sense !

Ciao

[BriHar]

I've seen everything recommended as a core from cardboard to plasterboard, plywood being a very popular choice. Many studio designers have their own personal choice. Core material is not considered by many to be as relevant as is size and spacing as these hanger panels work on a very different principle i.e. waveguiding - which is not very well documented and perhaps not very well understood.
The advantage of homosote, from what I understand, is that it will be more effective for lower frequencies. Homosote or soft-fiber board is the type of board used for making pin-walls, so if you go to the store and tell them you want the soft core of a pinup panel they should be able to source it.
Failing that though, you could substitute cork (albeit rather expensive) or thick carton or cardboard - you might even try honeycomb panels, but plywood will also 'work' as Glenn suggested.

[simo]

Thanks a lot for you very clear explanation Brian, much appreciated !

All the Best

ciao
simo

[simo]

Sorry guys to bother you again with this, but…
I've just found this website that sell notice board in UK made with 100% recycled newspaper, which should be what we want, right?

BUT looking at the products specification I wasn't convinced by their density, which I think is a bit on the heavy side (500 Kg/m3)….I seem to remember that in another thread it was advised for the hangers' core to use something with a density of 160 Kg/m3 or around that.
Basically my concern is that if I use this product as the core of my hangers it will make them too heavy, so they won't be able to move in sympathy with the sound as I believe they are supposed to?

If you want to have a look at the website here's the link:
- http://www.sundeala.co.uk/sundeala.htm
- click on Notice boards
- click on Sundeala Uncovered
- click full product specification

Shall I keep looking for something else lighter you reckon?

Many Thanks in anticipation guys

ciao
simo

[BriHar]

500 kg/m³ does sound a bit heavy, probably depends on the bonding agent.
The panels I will be using are 10mm thick and weigh 2.3Kg/m² (so 230Kg/m³)

see also http://www.johnlsayers.com/phpBB2/viewt ... 5&start=45

[John Sayers]

The stuff I use is 400kg/m3 so that looks about right - I don't know where you got the 160kg idea from.

[simo]

Brian and John - Thanks a lot for your response.

John, the link that Brian posted (acoustic hangers) is where I got the 160 kg/m³ information…. BUT if you say that you use material that's 400 kg/m3 (obviously with success!) and what I found looks right, well that's good enough for me - Thanks

ciao

[simo]

Hello everyone…me again sorry to post here so much recently …just a quiet time work-wise, so trying to get more stuff done with my studio.

Four questions (apologies ) about the speaker box and soffit this time…. they might be silly questions, but ones that I'd like to get off my chest ! :

Q1) Speakers height from floor:
As it stands now the acoustic axis of my speakers is at circa 1.3m from the floor.
I read everywhere that 1,2m is suggested, otherwise you need to think about tilting them down to face your head.
To give you more information, my room height (not considering the false splayed ceiling or cloud that I'm planning to build) is 2.4m, so actually having the speaker's axis at 1.2m from the floor would land exactly at half way (50%), which I gather should be avoided as well…
I could modify the soffit (not easily but I guess I could)…would you face the trouble? or if 1.2m is only a guideline, and so if my speakers are a bit higher it's nothing outrageous ?

Q2) For the decoupling layer to line the inside the speaker box:
I can find soft rubber strips of thickness ranging from 2mm up to 25mm, so I was planning on using a 5mm layer…Is that suitable in your opinion? Or would you go with a thicker / thinner one?

Q3) For the external power switch for the soffit-mounted speakers:
I'll try to explain this one with pics, hoping that it'll be easier to understand.

Option 1:

speakers power 1.jpg

... or

Option 2:

speakers power 2.jpg

I'm planning on using Option 2 (as it would give a neater finish)…. would that be correct ?

Q4) I've seen suggested somewhere around the forum to use a packing strap or a heavy string around the speakers in order to be able to pull them back out of their box if needed… BUT - don't laugh - my question is: how would you hide the ends of that strap for a neat finish?
I mean, I read on another thread about leaving a few millimetres (if possible 1mm) gap between the front panel (bezel) and the speakers front face and to seal around the edges so they are decoupled…and then I end up with the ends of this strap / string hanging out of that gap? not very neat right? I can feel the solution it's under my nose but I have to admit I'm a bit puzzled …stupid question I know, but hey…i warned you at the beginning, didn't I ?

Thanks in advance for your help guys !

ciao
simo

[BriHar]

Q1. The 1.2m is just a guideline based on the average height of a seated persons ear. Measure from the floor to your own ear when seated normally to get the exact figure - it will probably be around 1.2 m. Granted that 50 % of the floor to ceiling is not ideal - hence the invention of the cloud so we can adjust this when necessary. Prepare your space for the inclusion of a cloud or drop ceiling over the listening position should it become necessary. Testing will quickly show if you'll need it, and then you can consider soft or hardbacked (modal problems) and whether sloped for reflection problems.
Regardless, the correct height for the speakers is ear height. The space can be corrected.

Q2. 5mm sounds good - important is that the weight of the speaker compresses the rubber, but not completely. If you lay out the rubber as you will eventually install it, then place the speaker on it and measure the thickness before and after, there should be about a 15 -30 % compression if I remember correctly.

Q3. Not sure what the question is - it seems to be a matter of taste, but option 2 looks the most convenient to me. You might also consider controlling both monitors from a single switch. You've opted to install the monitors with their respective amps intact, hopefully the ventillation is adequate. Something else you might keep an eye on though - when I had my actives set up with a separate switch, they used to POP when switched on and off - the power switch on the monitors themselves had protection circuitry to prevent this, but my remote switch obviously bypassed this as they were always physically switched on. Perhaps you should test this before committing to a final decision.

Q4. I've been pondering this same problem recently. If you come up with a good idea, let us know.

[Ro]

Q3: You're planning on adding ACTIVE monitors in a soffit wall. No problem, if you have proper heat exits build in the soffit.
Active monitors have amplifiers. Thos amps will get warm, or even hot. The heat needs to escape or you'll blow your amps. You can either add a vent shaft behind the amps or detach the amp completely and place it somewhere else.

[simo]

What can I say… Brian, your answers are as clear as ever, Thanks man, all of that totally satisfies my curiosity !
…and yeah, let's see who comes up first with the solution for Q4

Ro, thanks for your response man !
Yes I'm planning on building the speaker box and soffit following John's design to allow air circulation:
- opening above & below the rear of the speaker box
- a slot on the front panel, above the speaker (connected with the top vent of the box via a 'tunnel' made with chicken wire or a duct - like the one used for the HVAC - to prevent the insulation to stop the air flow)
- a port at the bottom of the soffit

The idea of separating the amp makes a lot of sense (and I know Genelec supports that)

Genelec 1031A.jpg

…but it makes me nervous too and I haven't taken that into account either when building the soffit…

Many Thanks

ciao
simo

[simo]

Just about to buy some rubber for lining the inside of the speaker box.

Here's a chart I found…I thought it would be useful to post it here as a reference for everyone (hope you can see it ok !).

rubber technical properties guide.png

Looking at the characteristics, to me it seems sensible to get the "Natural" one (first column from the left)….but you still have some time to stop me…

Have a good weekend !

Ciao
simo

[Soundman2020]

Neoprene is what you want. Or even better, Sorbothane (which is not on your list).

- Stuart -

[simo]

Thanks Stuart for your response !

I managed to find a supplier for Sorbothane here in the UK… wow! that stuff IS expensive:
500x500 x 3mm (£39)
500x500 x 4mm (£46)
500x500 x 5mm (£53)
500x500 x 6mm (£60)

I've seen Glenn suggesting on another thread as alternatives: Sylomer (I found in the same price range as the sorbothane), soft neoprene or closed cell foam… I don't know whether his list was in order of performance, but I'm starting (for my pocket) to fear so

Would using closed cell foam be that bad, you reckon? …as it's noticeably cheeper, you know !


Or if I stretch to the Sorbothane sheets, would the 3mm option suffice?
I know you often like to quote on your posts that "every inch counts"…but at this stage of my build I would add that "every penny counts"

ciao
simo