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largo

DIY Auralex Gramma Pad-a-like

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[quote name='lemmywinks' post='608772' date='Sep 25 2009, 04:50 PM']Yeah i tried my Schroeder on a stand and the bottom end went walkies, on the Gramma it's right there and nice and tight. Maybe it's the magic pixie dust in the Auralex foam? So that's where my £50 went!

Btw i got all the p1ss taking when i started using it, especially when i foolishly told our singer how much it cost. You sound like a total clown trying to justify spending money on wood and foam[/quote]

Same here. I hate having to elevate my cab for the same reason. I was a bit weary about using the foam but it does seem to keep most of the low end.
Maybe its different if i used the platform as well. Quite fancy getting one now.

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Ive decided to buy one at some point soon.
Over the past couple of weeks ive used my foam at all the gigs and i do like what i hear.
I find my DJ5 is a bit deeper sounding than my P5 and its been getting a bit out of control on the hollow stages/wooden floors. The foam has really helped but i feel a proper platform will be even better.

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[quote name='lemmywinks' post='606872' date='Sep 23 2009, 05:41 PM']Pics up as promised, if you need any more from different angles give us a shout

Like i said, a bit cheeky for £50![/quote]
What is the purple foam in the middle "supposed" to to?

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I'd be interested in building one too. Any idea where I can get the foam strips from?

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[quote name='Kirky' post='619523' date='Oct 7 2009, 01:06 PM']I'd be interested in building one too. Any idea where I can get the foam strips from?[/quote]

I got mine from Studio Spares.

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This thread inspired me to buy a Gramma (absolute music had an ex display one - took me 5 mins to actually find what was wrong with it).

I'm intrigued how its going to sound but I've got a lot of rehearsals and 3 very different gigs in the next few weeks so I'll give it a go. If nothing else I'm hoping it will enable me to dial in a fairly consistent sound on varying stages/floors and clean up a little bit of boominess.

J

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[quote name='MoonBassAlpha' post='619486' date='Oct 7 2009, 12:40 PM']What is the purple foam in the middle "supposed" to to?[/quote]


It makes your car go faster and also increases the size of your wang twofold.

Really, i have no idea!

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[quote name='warwickhunt' post='608768' date='Sep 25 2009, 04:44 PM']I have to confess that I thought I'd be losing some bottom end but that doesn't seem to be the case, I'd love to hear the science behind why that doesn't happen.[/quote]

You don't lose any true bottom because the cab is still close to the floor. As you elevate the cab further from the floor the highest frequency that benefits from boundary coupling gets lower and lower, until eventually it goes below the useful range of a bass cab - by which point the cab would need to be 7 feet from the floor boundary!

The coupling the PlatFoam reduces is mechanical coupling, not boundary reinforcement aka acoustic coupling. With boundary reinforcement the floor acts as a solid and unmoving reflector, so you just get more bottom in a consistent and predictable manner. With mechanical coupling the floor acts as a wobbly resonator, like a giant drum skin - as a non-harmonic resonator it has a rather atonal series of resonant modes, which different notes will excite in different ways, hence almost random booming on some notes but nothing on others. Nightmare!

Glad to see that the PlatFoam idea is catching on, I've been banging on about it for years - just ordered a load myself in fact.

Alex

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[quote name='alexclaber' post='619773' date='Oct 7 2009, 05:16 PM']Glad to see that the PlatFoam idea is catching on, I've been banging on about it for years - just ordered a load myself in fact.

Alex[/quote]

I think it was you who put me on to in in the wooden stage thread a while ago. Glad you did.

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Haven't built mine yet, but now have everything I need so hoping to grab a bit of time this weekend. My Schroeder cab is pretty much 60cm x 40cm so going to build a platform pretty much this size.
Will post some pics when I get started.

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Mmmm, not sure if I should be speaking to you as you beat me to a P5 by (I reckon) 2 minutes.....
And still a bit peaved as I was told by voxpop that he would get in touch on Saturday to let me know whether the bass was gone or not. Still waiting!!!!
I'd be grateful for first dibs on the P5 if it doesn't work out for you?

Back to the build, last weekend I went about building my very own Gramma-pad-a-like. I'll go through this Blue Peter style, so starting with the shopping list.

Auralex Platfoam X1 from Studiospares @ £11.07 - I cancelled my web order half-way through and was emailed the next morning offering free delivery if I wanted to go ahead with the order. Wee tip!!!
Carpet Speaker Covering from Maplin - 0.5m x 1.5m at £4.97 inc shipping
Other stuff I had lying around. PVA Glue, Evostick Glue
15mm external plywood. Got an offcut from a joiner friend of mine.
Staple Gun


[b]Step One[/b] - Measure Schroeder 410L and cut plywood to size. 62cm x 45cm is a couple of cm bigger in each dimension.




[b]Step Two[/b] - Measure carpet covering and cut to size, around 10cm too big round all edges.




[b]Step Three[/b] - Spread PVA glue on top side of board and pulled tight.




[b]Step Four[/b] - Stapled underside to hold in place.




[b]Step Five[/b] - Measured Auralex Platfoam. Cut in half using a sharp meat carving knife. Don't tell the missus !!!




[b]Step Six[/b] - Cut another panel of carpet cloth. Glue in place, and then use staples. Most of these will be hidden by the platfoam anyway.




[b]Step Seven[/b] - Glue underside of platfoam using PVA. Also used fair amount of Evostick (not shown) as the PVA didn't seem strong enough.




[b]Step Eight[/b] - Put on some extra weight and left overnight to dry.




I now have what I think a Gramma pad will look like. Will be trying this out on Saturday's gig and will let you all know how it goes. My only complaint is that I forgot to take a picture of this when it was finished, and it's now chucked in the back of the trailer. I'll post a finished article picture after the weekend.

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That's pretty much how I did mine.
The only differences are 1) I used carpet tiles which I [s]stole[/s] [s]lifted[/s] borrowed from work, 2) I cut a carry-handle slot in mine -- I highly recommend this, it makes it dead easy to carry even if you only have 1 or 2 fingers free! and 3) the layout of the foam.
I used 3 bits of foam because at the time I had an SWR Triad, and I was a bit concerned that 2 bits of foam wouldn't handle all 80+lbs..! I expect it would have though. I suppose it's possible that with that centre strip added, mine will block less vibration than yours. It certainly works bloody well as it is though!
Excuse the tatty black paint on the underside... the spray can ran out and after all this time I [i]still[/i] haven't got my arse into gear to buy another.
So... yay for homemade Grammas! :)

[attachment=34769:platform_1.jpg]
[attachment=34770:platform_2.jpg]

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I've ordered the parts and am going to have a go this weekend. Do you reckon it needs the carpet on the underside or could I just glue the platfoam direct to the wood?

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[quote name='warwickhunt' post='608768' date='Sep 25 2009, 04:44 PM']I use one (the 30"x19" one) with my pair of Aggie DB12's and aside from the isolation benefit it lifts the cabs that bit extra off the floor which does help with such diminutive cabs. The guitarist in one of my bands laughed when I first used it but wasn't laughing so much when we played on a big hollow stage and he struggled to control the bottom end on his guitar amp... I had no such problems! I have to confess that I thought I'd be losing some bottom end but that doesn't seem to be the case, I'd love to hear the science behind why that doesn't happen.[/quote]

Hiya mate. Do you have any pics of that setup? Got the two aggie cabs myself and keen to se what it look slike :-)

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[quote name='biskitbass' post='637089' date='Oct 26 2009, 05:18 PM']Hiya mate. Do you have any pics of that setup? Got the two aggie cabs myself and keen to se what it look slike :-)[/quote]

I have to confess the pad is pretty unobtrusive and I've yet to have anybody at a gig (other than band members) even notice that it is there. I'll flick through some recent gig pics later but I've not 'specifically' taken a pic of it so it may well be a background jobbie. :rolleyes:

If I can't find one I'll get one taken but I don't have a gig for a couple of weeks, so as and when. :)

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[quote name='warwickhunt' post='637150' date='Oct 26 2009, 07:23 PM']I have to confess the pad is pretty unobtrusive and I've yet to have anybody at a gig (other than band members) even notice that it is there. I'll flick through some recent gig pics later but I've not 'specifically' taken a pic of it so it may well be a background jobbie. :rolleyes:

If I can't find one I'll get one taken but I don't have a gig for a couple of weeks, so as and when. :)[/quote]


Thankyou :-)

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[quote name='Kirky' post='631757' date='Oct 20 2009, 07:25 PM']I've ordered the parts and am going to have a go this weekend. Do you reckon it needs the carpet on the underside or could I just glue the platfoam direct to the wood?[/quote]
You can glue the platfoam to the wood. That's what I did.

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OK I finally got round to making mine. Not sure it was all that much cheaper than buying one in the end, but had fun making it. Haven't tried it in anger yet.

[attachment=37592:GRAMMA_1.JPG][attachment=37593:GRAMMA_2.JPG][attachment=37594:GRAMMA_3.JPG]

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Looks better than the real thing :) Very nice work.

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Thanks I'm no DIY expert. Looking forward to hearing what difference it makes.

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