SPACE COUPLERS. Theory, construction and effectiveness on traps.

[terry j]

In this thread Is a totally dead room useful for a small home studio? the idea of using space couplers was floated.

The claim is that at lower frequencies the effectiveness of trapping can be increased dramatically.

This idea came at a pretty good time for me as the look and finish of the traps this would give is just what I was after.

So, a quick re-do of my build and now I will use space couplers. This is for aesthetic reasons, but any gain in effectiveness will of course be welcomed!

The build itself is easy as, happy to post pics for others (and have alternative ideas too).

For now tho, I am happy to run tests and measurements (as directed/suggested by others more knowledgable) so we can have a bit of hard data on the effects of space couplers facing traps.

I will use REW for those measurements, ....I guess there is a way that I can e-mail the raw data??? I ask because the more knowledgable guys might find it easier to have a look at what they want to see if they had the files themselves. It is a bit clumsy for them to ask me what to generate, then for me to do it and post it.

Better off they just post the point they want to see??? (so if it can be done I am happy to send the data to them...but you will have to tell me how to do it)

This is what I can do. I can measure the traps effectiveness as-is (without couplers) so we establish the base line performance.

Then of course I can re-measure when (maybe even as, it can be in installments) the space couplers get added.

The only difference between the two stages will be the addition of the coupler structure, the amount and placement of the f/glass will remain the same.

There seemed to be interest in this in the other thread, so now is the time to ask what you would like done.

I do not have heaps of time to wait here, if the interest has waned then so be it, I will go ahead and just install the couplers (as I say I am doing it for looks). This will start happening in the next few days, so I guess questions/requests need to start appearing soon.

I have just blindly followed the construction of the couplers from pictures available, three inch depth and three inch square wells.

I see no reason why those figures are 'magic' figures, why (for example) the depth cannot be greater or less, the square size greater or less, indeed even why it needs to be square (eg could be longer in one dimension than the other, or even the coupler could be made from 'discs'...lop off lengths of suitable pipe and butt them all together, would look funky and have an opening where the circles do not meet, which would vary the diffusion/scattering etc).

Still, for the looks I want I will go with the design outlined.

Let me know what you want to see measured with this.

[tINY]

You really just want a hole. You can back-scatter some of the higher frequencies , but 1x3 furring strips flat could do that too.

Who is forwarding this idea? I've seen a couple references to it in the last couple of weeks.



-tINY

[terry j]

hi tiny

who is forwarding the idea?? me of course!!

I do recall seeing this thing in the past, but it must not have made too much of an impression with me. Anyway, in the thread that I linked to it was suggested that 'if I was handy making 'exotic' things the why not try the space coupler?'

The claim is that it increases the effectiveness down low of bass traps.

Dunno personally, and it is one of those things with not much data to back it up (?)

In any case, I am right in the middle of some humungous trap making, and this kind of look was always in the back of my mind.

So, combine the two. Gonna build them anyway for the looks, and maybe answer some of these questions as well.

What's not to like about that??

[DanDan]

I have mentioned Space Couplers a good few times now. I would love to test them, but the woodworking is beyond me. I am waiting for some tests from Gavin at Auralex. I have an article here which describes how the author (designer?) Jeff Syzmanksi, reckons they work. To me, it is all hypothetically plausible. However the increase of LF absorption of 40% in the 125 Octave band really caught my attention. If this is true, plus the promised 'liveness' this is truly a device worthy of experimentation. Hopefully Terry will show us that.
Terry, I would rather see FuzzMeasure, 3 in particular used. However, assuming I will assume REW and get to know it a bit better in order to help you-
Mark your measurement spots on the floor with tape. Tie some thread and a weight to your measurement mic. This will ensure that the mic measures in exactly the same spot before and after the introduction of the Couplers. Drive the room well by putting the speakers in the corners, on the floor, if possible. We are interested in modal decay here not frequency response. The more Couplers and Traps involved, the more meaningful the test. Four corners floor to ceiling would be ideal.
I very strongly encourage your efforts here. I have a good feeling about this.
40% more LF action. Better looking. Some HF diffusion/liveness.
A lot to like!
DD

[Jeffrey Hedback]

I'd be glad to offer some back story and application support. I worked along side both Jeff Szymanski and Gavin Haverstick at Auralex when the SpaceCoupler was brought forth by Russ Berger. Original application was to bring to the "common" room the possibility of a loosely coupled space as defined by Russ in his AES white paper (approx 1995...forget exact date). The concept is that a performance space can be very desirable for recording when it has a tightly controlled early reflection field (lower walls are highly absorptive) and then a longer (more vibrant) secondary decay slope (architecturally acheived by the upper region have different footprint and hard/diffusive surfaces). The SpaceCoupler grids, in this application, could simply be located in drop tile ceiling grids to create an aperture...variations allow brighter or more lush/warm responses.

As the product was put through some applications, Jeff Szymanski put it to test in a basement studio of well-known audio reviewer: coupler>drop tile laid on top>thick batt insulation between joists...result: subjectively cleaned up sub 50 Hz issues to both ears. Also, imaging and midrange detail improved.

I have used this product in many applications: above mix position, lateral early reflections...tracking rooms. I've noted that many Russ Bergers' latest rooms have the Couplers in use above mix as well. It is a product that is fully reliant on the adjoining surfaces be they hard or soft for the ultimate result.

Sometimes it is the deal-maker, sometimes part of comprehensive solution, but always...they look cool.

[DanDan]

Hi Jeff, thank you for joining in. Do you know the source of the 40% increase claim, e.g. a test?
DD

[Jeffrey Hedback]

Hi DanDan,

As I recall, that is from Jeff Szymanski's "in-house" testing in the Auralex testing lab (likely 2006). I don't think Auralex ever took the product to Riverbank. One of the issues with testing the "Coupler" in a Riverbank situation beyond sub 125 Hz room variance is how the Coupler redirects off-axis reflections toward perpendicular impact with absorber. Acoustical testing labs test only normal incident reflections. So it's somewhere between an absorber & a diffusor.

In use, I've had most success at mid-wall axial pressure points compared to corner assemblies.

Attached is front & rear views of small control room where the Couplers made great difference in conjunction with passive soffit traps that wrap the side & rear walls.

[Jeffrey Hedback]

I could add that 3" x3" wells were said to be significant in the products original design by Russ Berger, but other than a quick 1/4 wavelength relevance to mid frequency efectiveness...I'm not sure what that is. You can see this "smoothing of reflections" use in many lighting diffusors that have open grid patterns. In regard to the Auralex SpaceCoupler it is 3/8" Paulonia wood which is an instrument grade wood. I do think the wood itself has bearing on it's overall effectiveness.

[Ethan Winer]

Originally Posted by Jeffrey Hedback

the Auralex SpaceCoupler it is 3/8" Paulonia wood which is an instrument grade wood. I do think the wood itself has bearing on it's overall effectiveness.

Wood used for musical instruments is selected for its resonant properties, and is then carefully sculpted to vary the wood's thickness over distance to reinforce the fundamental and harmonic frequencies generated by the strings. But for diffusors and "space couplers" etc I'd think it's best for the wood to be rigid and non-resonant. Otherwise, resonances will be added into the room.

--Ethan

[Weasel9992]

Jeff, thanks a bunch for those comments. It's always great to have an expert with your experience and credentials weigh in on a topic like this. It takes it out of the realm of conjecture and into the world of real information.

Frank

[terry j]

Originally Posted by DanDan

I would love to test them, but the woodworking is beyond me.

You can do some tho can't you dan?? It is pretty easy, hopefully easy enough that my pics can show you how. Fingers crossed eh?

I am waiting for some tests from Gavin at Auralex. I have an article here which describes how the author (designer?) Jeff Syzmanksi, reckons they work. To me, it is all hypothetically plausible. However the increase of LF absorption of 40% in the 125 Octave band really caught my attention. If this is true, plus the promised 'liveness' this is truly a device worthy of experimentation. Hopefully Terry will show us that.

You mentioned in that other thread about 'pm for details', is there anything you need to let me know privately rather than publicly before I start?? You'd agree that if we want a good valid trial, we had better get it right construction wise.

Terry, I would rather see FuzzMeasure, 3 in particular used. However, assuming I will assume REW and get to know it a bit better in order to help you-
Mark your measurement spots on the floor with tape. Tie some thread and a weight to your measurement mic. This will ensure that the mic measures in exactly the same spot before and after the introduction of the Couplers. Drive the room well by putting the speakers in the corners, on the floor, if possible. We are interested in modal decay here not frequency response. The more Couplers and Traps involved, the more meaningful the test. Four corners floor to ceiling would be ideal.
I very strongly encourage your efforts here. I have a good feeling about this.
40% more LF action. Better looking. Some HF diffusion/liveness.
A lot to like!
DD

Looks like we are starting to hit the first of our problems or compromises. Fuzzmeasure, is that mainly used for mac guys???? Anyway, will stick with REW as I know it and have no need to learn another program. It does not have to be you I e-mail the file to (heck I guess I don't need to mail it to anyone-just that it might be easier and quicker is all) it can be anyone who knows more than I do (ie read everyone!!).

The more Couplers and Traps involved, the more meaningful the test. Four corners floor to ceiling would be ideal. Ok, is this a problem. Unfortunately what I will not be able to do is 'four corners normal trapped, vs four corners space coupled.' The coupler will be built into the traps, not an add on that can be taken off and put on at will (like it is in the photo earlier by Jeffery, it is clearly hanging in front of existing traps).

As I have already built some traps now, I CAN measure them as is, keep exactly the same f/glass and re-measure with the coupler (as I will be building new frames).

Conceivably I could do each succeeding trap likewise, but could not do four final traps with/without the coupler.

(hope that made sense, it's just the way and the order in which these will be built that I am trying to explain)

Tie some thread and a weight to your measurement mic. I can do that, but in the bass region here is that degree of repeatabilty and accuracy required???

Drive the room well by putting the speakers in the corners, on the floor, if possible. Ok, not going to move my speakers at all. If however you can convince me that this is needed, what I can do is haul out some subs (two subs each with four tens enough??) and lug them into a corner and leave it there. Bit of a hassle, but if needed then we may as well do it. (no point in doing it half arsed really) EDIT it would be much quicker and easier for me to simply use my mains where they are. Your call tho, let me know and I will obey!

Here is the current layout so you can see if it's acceptable to do the measurements with the layout as is



The red is the current layout, the space I am currently filling with the traps is marked beside the fireplace

Last thing from your post, as this is so we all can learn, can you amplify/explain more this line?

We are interested in modal decay here not frequency response. Can you seperate the two for me and tell us what we will be looking for?

Does this influence where you want me to put the mic for example?? (ie you want me to place the sub in a certain spot, do you want me to put the mic in a certain spot?)

Originally Posted by Jeffrey Hedback

In regard to the Auralex SpaceCoupler it is 3/8" Paulonia wood which is an instrument grade wood. I do think the wood itself has bearing on it's overall effectiveness.

Arrggghhh I got off audiophile forums for this sort of reason!! hahahah...was sick of discussion about how important it was to have your equipment rack built out of the right wood...for SONIC reasons (yeah, serious. Evidently the bees knees is canadian rock maple..arrggghhh)

Only having a bit of fun jeffery, but using a certain type of wood in things like this is just marketing rubbish surely. My only surprise is that it was used in a pro context, that's all.

Originally Posted by Jeffrey Hedback

In use, I've had most success at mid-wall axial pressure points compared to corner assemblies.

Typical aint it!! Mine are going into the corners.

[spm_gl]

Would it be feasible to make a prototype out of cardboard or other waste material, just for a first comparison? I've identified two corners in our new room that would look really good with space couplers from floor to ceiling, but the construction and material cost is prohibitive for a non-tested solution.

[Jeffrey Hedback]

Interesting discussion. Regarding the resonant quality of the paulownia wood verses another material, I'll start by what I have heard. I have heard both the Auralex paulownia products (SpaceCouplers & SpaceArrays) as well as the RPG hemishperical diffusor and all three are top rate devices. I don't know the history of the product development process taken by Russ Berger on materials benefits when designing the SpaceCoupler, but there is certainly no detrimental resonance.

So, I think it (the material of the product) is worthy of mention. At some level everything is resonant and this is important...at other levels it's important to keep a balance between esoteric and meaningful. That being said, were a "Coupler" to be made of MDF/HDF I do think it would perform and could have different qualities (would have to be tested both objectively and subjectively to know). I do not think that a typical cardboard would give same performance.


I look forward to the field test results Terry J

[Ethan Winer]

Originally Posted by Jeffrey Hedback

were a "Coupler" to be made of MDF/HDF ... (would have to be tested both objectively and subjectively to know).

Yeah, that's all I'm saying. Though I'd expect MDF to sound and measure pretty much the same due to the 3/8" inch thickness, but who knows...

I do not think that a typical cardboard would give same performance.

For sure.

--Ethan

[spm_gl]

I'm not considering actually using cardboard, the question is rather, would it work for prototyping, i.e. would it show any effect? Two 3x1m couplers are not something one builds to see if they work at that position. Any ideas for cheap (ugly) material?

[terry j]

a few very slight alterations

first off, will be using 1/8 plywood (will be clear why when I post pics of construction method..and I can stain to match existing wood architrave etc ie aesthetic reasons)

guess that part is open for 'debate', let's see, practical first. More chance of resonating (given that they are intended to be in the place where the bass has built up the most does not help that one!!), so maybe more care taken to ensure a good bond.

theoretical..less scattering of the highs? (smaller surface to reflect from) yet maybe better direction of 'air' into the trap? (smaller 'obstruction')

Haha, will it be audible. Doubt it, but we can have our very own 'audiophile' discussion on it and argue till the cows come home!..ie an audiophile discussion is always about the minutiae and things that don't matter.

a very slight increase in the spacing between dividers works well for the sizes I have in mind, so the well size goes from 75 to 77.5 mm, cannot imagine that being significant at all.

Still waiting on answers to the procedure I asked above, but for now (speakers and LP in the spots indicated on the diagram) here are some preliminary graphs. All unsmoothed.



The red is a close mic measurement of the woofer, so we can see what the room does to what is the 'reference'.

The others were done at the LP, green is with the trap facing ON, purple is with it removed (ie no f/glass at all anywhere in the room in the corners, still have some f'glas on the walls for reflection control).

Maybe a pic is in order so you understand what is going on and what the tests will consist of.



That is the little cutout in the diagram above, something like 4700 high and 1350 wide, and about 300 deep or so. (you can just see some of the reflection batts hanging). That frame is what carries the panels.



That is with the panels up, and the two pics show what was measured.

The cavity behind the facing (2 inches of 48 kg/m3 btw) will be stuffed with normal ceiling insulation. Two batts deep, slightly compressed into that cavity.

I will re-measure once they are in, and then replace the facing and get the final measurement. (ceiling insulation is cheap, been wondering-and will probably try-compressing it even more and fitting three layers rather than two behind it. Any thoughts from the experts whether it is worthwhile?? Guess we can just wait and see, the measurements won't be too far away)

That will cover the set of baseline measurements, then over the next week I can re-do them with the coupler installed.

Anyway, is there anything in what you see here that tells you I need (for example, as asked above) to place subs in the corner etc etc, or does it look like we can get useful data from things the way they are?

EDIT one thing that has been in the back of my mind to test, the idea of a membrane as well in front of the f/glass.

Ethan do I recall correctly that you say it also gives a performance increase?? I am thinking black builders plastic pretty taut, but 1/4 inch or so off the f/blass, not touching. Have I got that right??

If it helps performance great (tho would reflect highs, good depending on what you need I guess??), but there is a very good practical reason also. Whatever we use (fabric or plastic) we still need to hide the yellow f/glass behind the coupler. So a hidden booster if we can get away with plastic behind it (given that it helps performance, which is the question)

[terry j]

Originally Posted by spm_gl

I'm not considering actually using cardboard, the question is rather, would it work for prototyping, i.e. would it show any effect? Two 3x1m couplers are not something one builds to see if they work at that position. Any ideas for cheap (ugly) material?

I may be different from most, but I am doing it for the looks. IF there is also an improvement in performance then great! I'll take it.

In any case, I get the idea that the only thing cardboard has going for a test is cheapness, I feel it would be more a pita to build a test piece out of c/board than wood?? (flimsy, won't stay still for you etc)??

[spm_gl]

I'm watching your build, and seeing if my apprentice is up to the woodworking task

[DanDan]

Terry, I hope I have not put you off with red herrings. Some answers-
The info I have was in Resolution Magazine, thus I can't really just put it up here.
I also hope Russ Berger doesn't mind our activity here!
As far as I can see you have the right dimensions. I would use a hardish wood, like ply or mdf. There is nothing else to know.
This is a comparative test, without then with. Everything needs to stay exactly the same apart from the one change. Positions and repeatability are vital.
Leave the speakers as is, including sub. Drive both channels simultaneously.
You can limit the sweeps to below 300Hz if you wish.
We are trying to observe a significant 40% increase in LF absorption with Coupler added to Trap. Your Waterfall plots will have one or two long booms at LF. If the Coupler works as claimed, these booms should shorten. One in the whole room may not make enough of a difference to be clearly measurable. Two would be a lot better, and four ideal.
Try one and see if a difference appears.
Test in 4 spots, average them if you can. I am not sure if REW can make a waterfall of averaged measurements. If not pick the best looking one.
Read the Sticky Room Analysis Primer.
A membrane in front of a SuperChunk or your trap will almost certainly increase LF absorption. This is currently only an opinion as there are no tests. I promised to do it but goofed off. If you have the time and patience, please try it. I think using both a membrane and a Coupler would hinder each other.
It may not be 40% but I am convinced you will see a benefit from the Coupler. Plus they look good and deal with the fronting issue very nicely. I can send you this PDF privately if you wish, send me an email
soundsound@eircom.net
Hope this helps but keep em coming if you are not clear yet.
DD

[terry j]

righto Dan, onward and forward.

I will have a look today and see how practical it is to throw some subs in a corner, I might be able to do it...real estate is tight right now! Even so, it won't be exactly in a corner but pretty close, be buggered if I am pulling all the books out of yet another bookcase only to move it two feet!!

Will indicate on the diagram where it is if I manage to get it in.

Four positions, for sure that's no problem. Around the LP? Or do you mean a few feet apart, really widely spaced? I mean I don't care, it's pretty easy for me to do what is best here, as long as I know. Each corner of room, see what I mean?

I mean where is the best position to pick up what we want? May as well stick the mic there, the LP is kinda 'middle of roomish', so maybe not the best spot for these tests?

Pretty sure I have read the primer, will do it again tho, thanks.

Can easily test the membrane, but with what I had in mind not so easy to test then BOTH membrane and coupler. Would be a real bugger to have one undo the work of the other tho, so somehow need to know that so I can rule it in or out. Must have to think of a way to do that test.

Just for clarification, I don't use subs per se in my mains, just a pro woofer (18 inch PHLs), so any talk of subs makes me think of other things if you follow.

(Quite proud of my diy speakers, so be warned that any encouragement about them will make me wax lyrical,flowery and long!!)

EDIT last thing on all things 'mic', does it matter or do you have a preference for how high??

[terry j]

Ok, using my mains (the beautiful diy ones with 18 inch PHLs remember!) and with measurements done at the lp, think I have finished the preliminary testing.

Trouble is, there will be loads of graphs, hope that is not a problem.

I filled in the void behind the compressed fg facing layer by layer with normal ceiling f/glass. I also did my own test of going to three layers (with the view of going to four if indicated).

So that is what I will show first. Sorry for the number of graphs to come, can't see any other way? (it's confusing to have multiple graphs shown simultaneously)

No layers *purple* (ie completely empty and no facing) with one layer added *blue*



now one layer *blue* and the second layer *red*



Two layers *red* and three layers *purplish*



My conclusion is that the third layer did not bring enough benefits to keep it there, so it will come back out.

Anyway, the three layers were there when I put the facing back up, so this graph is three layers *purplish* and three layers plus facing *ocherish*



Hope that was not too confusing, but shows the progression as I added each bit.

May as well show nothing and everything, three layers and facing



***********************************************************************************************

Purely according to the FR I decided the third layer was not warranted.

then I looked at the decay times for two and three layers



they go down in this graph along the 100 hz line according to two, three and three plus facing. Anyway, even tho the FR change from two to three layers was nothing to get too excited about, I did like the improvement in decay times.

that is one third octave bands.....'but a funny thing happened on the way to the forum'....if I switch to one octave bands, the three plus face suddenly switches and becomes the longest!!




Arrggh, hope I hear in one third octave bands!!

Can someone help me interpret what is going on there?

That is more than enough graphs for one sitting, the main point is that I should have enough to be able to compare what we want when I add the couplers.

Any requests with this, or is it fine for now? (must remember to save the measurement set!!)

[terry j]

So the panels are coming down for the new build, took the opportunity to do an average of four measurements as asked.

Basically each corner of the listening chair, pointing outwards. maybe two and a half feet deep by three feet wide, and one and a half feet difference in height (arm of chair vs top of chair)

As before, (at least in the FR department) very little difference between two layers and three layers of the ceiling insulation



Does nothing to change my decision to remove the third layer.

Here is the average of two layers of ceiling insulation vs three layers plus compressed f/g facing



I have left the two layers in there, so no average measurements for one and none...well at least not now. If it comes up I will get them then.

On to the build, with pics....and of course measurements.

fingers crossed it does help eh?

[DanDan]

Hi T, I think I have confused the issues by going for full on testing.
Let's cut this down to the essentials.
Leave the speakers where they are. Drive both.
Pick one spot, mix position, ear height.
We are interested in LF decay only. In REW only Waterfall plots will show that.
There should be one or two long mountain ranges at the bottom end.
With the Couplers this should shorten considerably.
DD

[terry j]

Hi dan, got your e-mail thanks.

Just for reference sake in the thread, here is a link that lupo gave in the thread this 'grew' from http://www.resolutionmag.com/pdfs/SWEETS~1/bigsoundsmallroom.pdf. For all I know this may be the only data available.

The measurements I am using were simply deduced from pics and dimensions of the coupler I have seen.

Originally Posted by DanDan

Hi T, I think I have confused the issues by going for full on testing.
Let's cut this down to the essentials.

Ahh, can I conclude that the series of graphs above are just cluttering the thread?? If so, let me know and I can edit them out (or the uneccessary ones?).

My verbiage clutters most threads anyway, no need for extra!!

Leave the speakers where they are. Drive both.
Pick one spot, mix position, ear height.

Hahaha, You honour me. My mix position?? Dude, I am a dumbass 2 ch stereo guy, playing in the big boys forum!!

Only here to learn about room treatment for my listening room. Audiophiles play with components to get 'the best sound'. the sensible ones consider the room.

We are interested in LF decay only. In REW only Waterfall plots will show that.
There should be one or two long mountain ranges at the bottom end.
With the Couplers this should shorten considerably.
DD

Let me know about the graphs and whether they should stay. I have generated a few waterfalls, but for some strange reason I can't seem to get them to show from 20-200...I can get 40-200 or 20-100, but there is a point where either the top cuts off or the bottom cuts off.

No biggie, will give you the bottom..(which is not the same as giving you the arse btw)

These measurements are at ear height, listening position, both channels driven.



my speakers drop like a stone under 35 hz, so only noise under that. This setting gave me the highest reach FR wise.

Purple without any traps, ochre compressed f/glass facing and ceiling insulation behind it.

[jayfrigo]

Late to the party, but a few additional thoughts:

While the coupler allows 90 degree incident waves simply to pass through, sound at angles of incidence greater or less than 90 degrees are reflected into the coupled space, and subsequently returned as a kind of artificial reverberant field, or diffused (loosely speaking) back into the environment (behavior changes with incident angle of course, and the diffusion is not as even or predictable as with something like the typical 1D QRD or 2D PRD).

In a control room, this could be one simple method of breaking up some mid-range early reflections without removing too much energy in a room, or causing comb filtering effects of QRDs that are placed too close to the listening position (typical of attempted use at first reflection points in a narrow room). Of course you would have to take into account speaker locations and incident angles. Also, this implementation would not address any low frequency concerns.

They could also be used with absorption behind depending on goals and application. One example is as part of a cloud overhead, with absorption behind the grating. This is one area where they claim the enhanced bass performance. I have a couple theories as to why this might be the case, but I couldn't say definitively without some more study and testing.

In a recording room, the application would seem more obvious. With more absorption lower in the room, you can control the early reflection characteristic, yet by coupling a live space overhead, you get the added benefit of a longer-than-expected, smooth reverb tail, without sacrificing your control. This technique, while it may seem new to studio practitioners, has been practiced for some time in certain large-scale projects, including some concert halls.

[terry j]

Ok, some progress now, moving on from the mundane measuring stuff.

A shot or two of the first coupler.





Ha! tip number one for you. Obviously it is best to prepare the sheet first, in my case I used plywood. I mixed a stain that would suit the joinery in the room, and gave a coat of varnish. If you want to use MDF or whatever, it is easiest if you paint a sheet when it is whole rather than in strips.

If you use stain and varnish as I did, then don't make this mistake. To do a quick stain on the cut edge, I clamped them together as a pack and did all the edges at once. The stain dribbled between each sheet and stripped back the varnish. Those are the blotches you can see in places.

The simplest way to stain the cut edge is to use the side of the brush, not too wet. Takes thirty seconds an edge, do them individually.

As a result, I threw it all away and started again (because the main reason I am doing it is for looks, hopefully it works better too), but nonetheless you should still see the method of construction, and hopefully get how easy it is to do.

So those of you who previously thought 'my woodworking skills are not up to it'...or your apprentices!!...forget it, it's as easy as pie.

I used an el-cheapo saw, been laying around unused for years so cannot remember how much it cost...hundred bucks or so?? anyway, each country is different so go to your local bog cheap retailer, these things are a dime a dozen.



There are many different cut thicknesses with saw blades, all you need to do is find a blade that has a cut pretty close to the thickness of the material you are using. (I can make another post later if needed if someone says 'my material is 12 mm thick, what blade do I use? Well you can't obviously, but there are many ways to skin a cat)

Make up a carriage to hold your workpiece. The thing I want you to notice is how I did it, scraps of wood laying around and a bit of glue. It truly is not rocket science.

All you want is a slider that you can move backwards and forwards without rocking or looseness. start with one edge, glue the strip and then glue another strip on the other side. Make it fit snugly on the top, and for ease later just use a square to make sure is right angles to the edge of the saw. (don't know how easy to make the explanation, but going into a little bit of detail as some have mentioned 'no woodworking skills'...so excuse me if it is too trivial for you, it's for the other blokes ok?)

Here is the carriage on the table, you should easily envisage it sliding back and forth with little rock.



Another look at the carriage, and look closely.

It is the next BIG tip, and the secret of it all. It is how anyone will be able to turn out repeatable accurate work.



See the little bit of ply to the right of the blade? that is the trick.

It is the ONLY time you need to be halfway accurate. It is a locating lug. It will be very clear in the following pics how it works. And even if you are not accurate in placing it (you wanted 77.5mm but instead got 75.8, does not matter as every cut will be the same from here on out).



There are two options for the first cut, either it is exactly a well width wide, or as in this case, less than. That little bit of pine was a test jig, (as I am fitting it inside an existing frame) so I cut the series of notches you see, and then positioned it within the frame evenly so I had equal space each side of the well. I can then use that (as you see here) to get the first cut right.

Also note that I clamped the entire pack together, another way of making everything 'the same'.




Sorry for the wordiness earlier, but now it is all clear.

We make the first cut (if smaller than a well width then as above, if exactly a well width then butt it up against the locating lug and make the cut) and then we lift the whole pack and place the cut on the lug, ready for the next cut (by sliding the carriage back and forth).

Each time you make a cut, move the lot over and do the next. As they are all in a bundle together, we cannot BUT have each piece exactly the same as the next. (something I have not mentioned yet, the saw needs to be adjusted so the the cut is at, or just over, halfway thru the piece)



I know you have worked this out, here is how they (quite literally!) slot together.

There you have it, easy as. I think it is pretty self explanatory, but hey fire away if I was unclear somewhere.

Gee dunno, that took me maybe an hour?? (including photo shots!). Pack them all together (note I had two different pack sizes, more in the direction than the other) and truly, it takes maybe two/three minutes to do ten/fifteen slides of the carriage?

It is all in the care taken to do the preparation of the slide, lug etc, everything else just naturally follows.

hmmm, one last tip??

Can YOU pick the difference in the carriage in these two shots?






No?? I will give you a hint.

It has something to do with the perfect three mm groove in the end of the middle finger on my left hand.

Don't leave the blade exposed on the other side yeah? It is now (strangely enough) hidden within the extra pieces I glued on.

A surgeon could not have done it better, thru all the skin, down to the pink meat...no blood as it was not deep enough. lucky I have quick reflexes, it could have been just that tad bit more serious.

Please don't forget little things like that eh? (hah, the things I do for YOU, hope you appreciate it)

The most important tip I saved for last.

[Blind]

brilliant... even though its not rocket science!

[DanDan]

Jeez Terry you should have a DIY TV show! I have a friend with a decent saw and a garage, so I will very likely follow your lead. Let's face it, you will definitely end up with fine looking trap fronts, and there is bound to be some acoustic benefit. Russ, Jeff, etc. are unlikely to be wrong.
Although this is worth a look.....Acoustics Forum • View topic - Helmholtz formula, is this incorrect?
DOH, I'm sure you will have more luck than me T.

I'm gonna stick with the economical here, lose the Frequency response graphs.
Measurement of Decay times is very unreliable, plus we are very interested in action below 90Hz so lets do Waterfalls only.
Unfortunately your Waterfall is quite good, I was hoping for something a lot worse :-)
e.g. Attachment 134301
As you can see here, there is a long low boom. If the story is true, couplers in front of the SuperChunks should shorten it noticeably.
We will have to work this. I will ask you to try taking measurements in different spots. Start with the couch or near the wall behind you. Try the corners.
We are looking for the worst longest boom. When you find it, that's our spot. One is fine. You asked about insulation way back, sorry didn't notice. In the current context, most of us just go for 3 p.c.f. insulation because it has proven itself over and over. It has been suggested that less dense is OK or even better in deep traps. Whatever, I recommend you go with the known. As you can see even testing is not so conclusive.
3pcf is 48Kg per cubic metre. Some people recommend going denser when RockWool is involved, e.g. 60Kg.
Onward, DD

[terry j]

Originally Posted by DanDan

Jeez Terry you should have a DIY TV show! I have a friend with a decent saw and a garage, so I will very likely follow your lead. Let's face it, you will definitely end up with fine looking trap fronts, and there is bound to be some acoustic benefit. Russ, Jeff, etc. are unlikely to be wrong.

Tv show eh? Couple of probs with that...one is the ugly mug, and maybe I am a one trick pony!

Nahh, actually I was serious about the ugly mug, but as it so happens I do have a few other tricks up my sleeve in this acoustic building area (very quick way to build qrds and prds), and eerily spookily coincidentally I HAVE been thinking about making some sort of dvd/video so they can be properly shown.

Are we entering the twilight zone??

And another equally spooky thing about your muck about observation, in about two weeks there will be about six hundred people coming thru the place (yearly regional tour or something by the National Trust) so to help make it interesting and educational for them I will be setting up a big bench and showing them all how to make/replace/duplicate the intricate ceiling cornice etc that you find in old houses...all the old plasterwork that are handmade and cannot be bought off the shelf.

It won't change the ugly mug tho, but it will be in the spirit of your suggestion! Might grab a happy snap and post it here for laughs when it happens.

will read the link.

(I can gather that the explanation WAS clear enough??)

I'm gonna stick with the economical here, lose the Frequency response graphs.
Measurement of Decay times is very unreliable, plus we are very interested in action below 90Hz so lets do Waterfalls only.

Did you mean clean the thread up and remove the earlier clutter? or just from now on.

Re the waterfalls, is it a help or hindrance to have one superimposed on the other.

Unfortunately your Waterfall is quite good, I was hoping for something a lot worse :-)
e.g. Attachment 134301

you were hoping for a lot worse? thanks.

Bastard

Invalid attachment BTW, but reasonably sure I get what you are saying even tho I can't see the illustration of it.

I will ask you to try taking measurements in different spots. Start with the couch or near the wall behind you. Try the corners.
We are looking for the worst longest boom. When you find it, that's our spot. One is fine.

Ok then, give me a few days tho yeah? Just so's we are on the same page (let's be honest, it HAS taken us a bit to finally get here, let's make sure we HAVE arrived!!) you do not care where at all I end up with the mic, just as long as I find a really bad spot in the room and stay there.

Ha, where I type traditionally had a ten or fifteen db boom, will try here first. (always had to have a special eq setting for this seat!!) Just to clarify for you, when I run the measurements I do not use eq, it is all raw and untouched, my last comment may he=ave been misinterpreted you see.

You asked about insulation way back, sorry didn't notice. In the current context, most of us just go for 3 p.c.f. insulation because it has proven itself over and over. It has been suggested that less dense is OK or even better in deep traps. Whatever, I recommend you go with the known. As you can see even testing is not so conclusive.
3pcf is 48Kg per cubic metre. Some people recommend going denser when RockWool is involved, e.g. 60Kg.
Onward, DD

Ok then, we are on the same page. The facing I use is two inch 48kg compressed f/glass, with one foot of 'densely packed' ceiling (fluffy) f/glass behind it as fill. (that was the two layer three layer bt I was talking bout earlier)

[DanDan]

T, sorry about the attachment. Dunno how to fix that. Here's a particularly ugly one with a singular low boom. Imagine if we could shorten that by 40%! Room Analysis Primer
You could take out the earlier graphs if you wish. I have seen one of these low booms shorten from 1.3S to 0.6 with no sign of that on the Freq Resp graph.
A Waterfall is all we need. Yes pick your worst spot and lets see if we can make it a little better.
You insulation scheme is very likely OK, but I can't be sure about that. I would use all 48Kg as it is known to work.
Just to clear something else up for other readers, the link
http://www.resolutionmag.com/pdfs/SW...dsmallroom.pdf
is exactly what I have been referring to. I didn't know it was publicly available.
I think it is fascinating that something so simple will probably deliver such benefits.
Well worth a read.
DD