Good idea and its something I will look more closely at.
I have made enquires previouslyabout locally made product and it is obtainable but is very expensive compared to std ply and MDF. AUD$300 per 1.2 x 2.4 metre sheet.
There is also the Green Glue from the USA which is popular as damping layer.
So I am exploring buying a the damping layer and making my own damped board.
Something like this:
Damping layer SWEDAC DG-U 6 and Damping Glue DG A2
http://www.swedac-acoustic.com/
Some nice Plywood to build from: http://www.fincolorply.com/koskisound.htm
mats
Last edited by matsj; 12-16-2008 at 01:40 AM. Reason: More
4345 diy, K2/Array diy Ht. TAD 4 way diy.
So I am exploring buying a the damping layer and making my own damped board.
Thats the idea !!!!
Have you ever thought about building a box out of chipboard and then building another around it out of MDF? Stuff it full of fibre glass at it works real well.
Hi Allan,
Can you please elaborate?
Are you saying laminate the particle board to the MDF? What type of Glue or epoxy?
How big a gap b/n the two layers if you are saying stuff the gap with fibre glass?
What thickness of board 9, 12, 18, 25 mm
Cupboard material research
http://babelfish.yahoo.com/translate...rUrl=Translate
http://www.soundguard.com.au/PDFs/news60815.pdf
I think by chipboard, he is referring to OSB (oriented strand board)
http://www.medtimbermerchants.com/_userimages/osb.jpg
It's pretty much replaced plywood for floors and roofs over here in NA.
I read something about this method of CLD, but I can't remember what the properties of OSB that were that were sought after aside from providing a different impedance than the MDF.
When I was using the lam system for turntables ( Ariston ) we laid up sheets of MDF on the factory floor and spread a measured amount over the surface and sat the second board over the top. Nothing fancy at all. The makers give application notes regarding the qty for ideal results No problems at all in fact the layer of 'goo' was remarkably even throughout the sheet. ( We were using this for plinths to good effect. Markedly better than the same thickness of MDF without treatment. Joe public would never see this as the edge was hidden in a shadow gap )
I can see no reason not to use a combo of mdf on the inner as the ballast layer and something better like Birch Ply as the outer.
In conjunction with well applied bracing and / or tension rods you should be in clover. I think one very quickly gets into the area of diminishing returns, and should also be taking a long hard look at the build of your listening area.
Single skin drywall shakes rattles and rolls , and all that other stuff. Now we need Andy.
Mac
Ian (and to all the guys contributing in this thread),
Thanks for a most fascinating, well-documented journey. I'm new to DIY and this is an awesome read (like a lot in this forum). Very inspiring indeed.
Keep it coming guys! and thanks for making this forum a great one!
cheers
I have contacted Accoustica locally and will work with them to come up with a practical and hopefully affordable solution
There are a lot of ways to do this but a lot of ways of wasting time and effort so I plan to get advice (technical ) which they have.
Please bear in mind I am dealing with a 2 way project and the woofer runs from 30 - 750 hertz or as high as 1200 hertz. This is quite difference to a sub woofer or a woofer box resonance and sound absorber issue.
Looking at Accoustica's product range they have roll form visco elastic sheet product for extensional for contrained layer damping and a board type product for marine applications that is mutifunctional as well as varioys grades of acoustic foams. They also have damping pads for industial applciations and home flooring as well as barrier and isolation materials.
I see the issue as a problem in the 30 -750 hertz range (up to 1500 hertz attentuated assuming 750 hertz crossover point)
We also dont want destructive sound from the box coming back out the big cone area or air born resonances created by the dimensions of the box.
As pointed out earlier we also dont want a noisy box in that zone.
It sounds simple but its not because sound is energy that has to go somewhere. Some of the materials used for industial applications and like marine are grouped as absorber, barriers and dampers.
According to what I have read below 300 hertz the threshold of audible box problems is not as accute as above 300 hertz and it is preferred that the noise is 30 db or more for more below the output of the cone driver.
So in a simplic way I want the woofer to act as if it were on an infinitely large baffle that did not resonate. Just like an open baffle speaker. People like open baffle because they dont sound boxy and because of the directional pattern.
All the box does is stop the rear radiation from cancelling out with the front wave of the woofer. The reflex porting tunes the mass of air / compliance in the box with that of the woofer equivalent compliance and the mass of air on the port to add reinforcement to the woofer cone output. So we dont wont to screw up how the port works trying to make the bax less noisy.
Therefore if we can absorb a portion of the sound energy on the region of interest from the woofer cone before it hits the hard structure of the enclosure cavity the structure is less likely to react and be noisy at those frequencies.
Typically this is more easily done at mid and higher frequencies than low frequencies. But we dont wont to absorb too much bass energy as this will effect the port action. Some of the materials are able to absorb as well and damp the substrate panel and I think this is the key to arriving at a workable solution.
I think the second line of defence is then to select a panel material as the enclosure shell that is inherantly well damped in the region of interest ie 300 - 750 hertz and is rigid at frequencies below 300 hertz. Below this frequency vibration and damping are a function of density and stiffness.
Somewhere on the www there was a good graphic that explained how to deal with sound problems in each region.
It was along the lines of 30-300 hertz stiffness and bracing, 300 -1000 hertz, mass damping and above 1000 hertz coincidence control .
I will see of I can find the graphic.
As you may have guessed I dont think making the box rediculously heavy is the answer to this type of enclosure application.
I have discussed this type of issue (large 2 way system) with some people who have applied some of the above and the results are night and day compared to building a plain box out of mdf or particle board.
This will take a little while to figure out so have a nice Xmas break.
Ian
Therefore applying simple logic one way to stio
Seems to me you're trying to construct a DMT cabinet a la Tannoy.
The 215 consists of a hardwood frame with all panels(35mm front rear MDF, 25mm thick elswhere) attached via a lossy mastic type adhesive( not unlike No more nails).The internal figure 8 bracing runs horizontal across a vertical spine, all panels braced with eachother but whereas the lap joints on the brace are glued with wood glue the parts that meet the walls/top/ bottom again use a lossy mastic type adhesive.
The rear of the bass unit couples to this brace via a blutack type of putty that is stiff at LF but flexible to HF (and absorbs HF energy).
As often happens with diy audio you get distracted while waiting for other things to happen........
So I started to think about what I listen to most of the time..at least when the main system is not in pieces.
This raises the age old question of pure audio versus the HT sound ie 5.1- 7.1 and how do you work it with the pure audio aspect.
Running enough class A power to heat a NY apartment in the middle of winter (all the time) is also not friendly on the packet or the environment.
For the most part I use seperate speakers for surround (read that smaller JBLs) with a receiver because I regard HT as entertainment and pure audio as late night stuff when its quiet and that special bottle of Port comes out.
Well things are a changing and if the content keeps coming the new Blue Ray lossess audio standards will exceed or at least equal PCM cd red book.
This all converges on what to do about the centre channel. Up until now I have elected to down mix the centre to the front L + R for practical purposes.
Of course HT fanatics will freak out at not having a centre speaker. My attitude is show me a centre speaker worthy of the job.
As the 4345 clones are semi retired and the E2 inspired project will be somewhat more compact I am wondering if a new centre speaker is do-able .
I am going to play with the idea while working on the main speakers (the AE TD-15m + Tad 4001/EH500).
What I might try is a pair of JBL 2123H cones with small vented alignments in a horizontal MTM arrangement much like some of the JBL centres seen in the NEW JBL 2008 catalgue. (now up on the reference section posted 24-12-2008.)
The high frequency device will most likely be a Eighteensound ND1095N driver and XT 1086 wave - guide. With a bit of room gain it will be -6 db at 75 hertz and woof out around 125 db at that frequency. It would have to be setup as a small front so as not to bottom the 2123's. But the real deal is the very seriously low mid band distortion of dual 2123h's .The crossover point will be around 1300 hertz and the 2123H centres will be about 20 inches apart. I am looking at the ND1095N because its the closest low cost alternative to the Tad drivers that I am aware of. It uses a titanium nitride (treated) dome and a polyestrer suspension. Its also a 1 inch exit and the XT1086 is a ready made wave-guide http://www.eighteensound.it/index.as...roduct&pid=178
If I am inspired by the results I might then look at a 1000 hertz wood horn like this http://www.geocities.jp/arai401204/Horn/A1K/A1K.html which is a drop dead gorgous horn and would match the larger 290 horns I have in the pipeline for 2009 along with single Tad 2002 compression driver. Matching customised AE TD10M mid bass woofers will then replace the 2123H which will find their way back into a modified 4345 along with the Eighteensound driver and horn.
At least that is the plan.
Also on the drawing board is the question of a suitable HT receiver or processor to route all the 1080p video / HD audio and drive the new Panasonic Plasma screen. I had alook at the Pioneer range and while I have not seen the 9th generation Pioneer screens the Panasonic 2008 range is very close to the 8th generation Pioneer stuff. Black is Black as they say.
I quite like LCD but Plasma better suitable my video needs.
The Integra installer range from parent Onkyo and the Pioneer LX 81 looks interesting. The digital engines in these newer boes are so good to makes sense to use them as the hub of a high performance A/V system
Well that was quite a distraction
Tell me about it.Originally Posted by Ian Mackenzie
I simply have the best mains I can and use then for both 2ch and HT. If I want to use some tube amps to power them for example, I unplug the AVR and use the audio via a switcher/pre (input select and level control). Takes about 30 secs to changeover. I use Yamaha pro poweramps for HT duties and only the DVDP goes through the AVR.
The only centre I would have in a HQ HT would be identical to the mains. If you only need a one or two person wide sweet spot, then in most rooms a centre is not required.
I have one of the drivers boxes open.
My inital reaction is OMG..what have I got here...Holy F.
Who made this thing. Robby the Robot!
Its a weird thing to say the least..not conventional by any means
Massive is an understatement.
The driver is 380 mm in diameter, 230 mm deep and the maget is 150 mm in diameter and 100 mm high. The top plate is about 20 mm.
Those numbers are not normal.
The cone is a variation of curveliner and quite deep. The rear of the cone is uncoated and appears a stiff paper, no corrigations and the front has a think coating that is slightly reflective. The driver appearance is dominated by the large metal phase plug, there being no dust cap.
Below in the works I can see a deep voice coil former the extends like a long tube in past a massive spider sourrounded by vents into a massive top plate. There appears a thick curved ring of aluminum like a core above the top plate. The basket is solid metal not pressed.
My impression is it obviously not a mass produced driver and has been assembled with great skill and care. The paper cone has been hand spayed apparently while other aspects like the top plate appear freshly turned. The ceramic magnet appears of a stacked approach.
It would appear to be of a design for the engineer with a well equiped machine shop who made it for himself as a a diy project driver.
weight 32 lbs
TD15M - 8ohm
Fs: 34.7Hz
Qms: 5.09
Vas: 312L
Cms: .3mm/N
Mms: 70g
Rms: 3kg/s
Xmax: 6mm
Sd: 855
Qes: .35
Re: 6.6
Le: .2mH
Z: 8ohm
Bl: 17Tm
Pe: 500W
Qts: .33
1W SPL: 97.8dB
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