[vettett15]

Got bored so I spend some time cooking up an idea, not something i'd be able to do real soon but perhaps in the near future.

Translam built Tempesta that utilizes damping/sound proofing materials to assemble the pieces and inside the walls.

Bottom compartment for the x-over and then ideally the monitors would be sitting on a pair of 12" subs (Rythmik 12" GR research?).

Not sure how high the Tempesta's need to sit above the floor (or relative to the LP).

[Rick Craig]

Got bored so I spend some time cooking up an idea, not something i'd be able to do real soon but perhaps in the near future.

Translam built Tempesta that utilizes damping/sound proofing materials to assemble the pieces and inside the walls.

Bottom compartment for the x-over and then ideally the monitors would be sitting on a pair of 12" subs (Rythmik 12" GR research?).

Not sure how high the Tempesta's need to sit above the floor (or relative to the LP).

If you want to buy a kit and DIY the cabinet design that's fine. I'll offer what support I can; however, a stacked laminate cabinet can sometimes have a strong coloration if not correctly executed. The TC12 subwoofer cabinet can be reconfigured to work well as a base.

[navin]

Got bored so I spend some time cooking up an idea, not something i'd be able to do real soon but perhaps in the near future.
Translam built Tempesta that utilizes damping/sound proofing materials to assemble the pieces and inside the walls.

Why not use layers of wood and sandwich the damping material between layers?

[vettett15]

Rick,  i wonder what would cause that... The shape alone (curved sides) would give it more rigidity than a typical box. 

Navin,  that would be the idea.  I just modeled it up as one piece to make it easy.  The only thing I would check is the strength of those adhesives because some of the ones I have found say they are not a "structural adhesive".  If it is stronger than the wood than I would say its fine.

For this I would build the baffle out of two pieces and attach them with the damping material too.  The source of the vibrations would be coming from that first baffle panel, so the more I can dampen it out before it gets to the cabinet the better.

[navin]

Navin,  that would be the idea.  I just modeled it up as one piece to make it easy.  The only thing I would check is the strength of those adhesives because some of the ones I have found say they are not a "structural adhesive".  If it is stronger than the wood than I would say its fine.

For this I would build the baffle out of two pieces and attach them with the damping material too.  The source of the vibrations would be coming from that first baffle panel, so the more I can dampen it out before it gets to the cabinet the better.

We have built about 6 pairs of speakers using layered cabinets.

The first thing we do is make some curved "templates" using 30mm MDF. 30 mm MDF is easier to work with than thinner wood as it does not bend and gives a really nice smooth surface for the curved sides to grip. The number of templates depends on the height of the speaker but about 6-8 are usually fine.

Then we start with a layer of 4mm MDF. On this we place fiberglass mat and pour epoxy over the mat ensuring the mat is well soaked in the epoxy. Then comes another layer of MDF. The contraptoin is strapped and left to cure over night. Then we lay epoxy glue and a layer of 1.5mm lead sheet some more epoxy glue and a layer of 4mm MDF on top. Again the cabinet is strapped and left to dry over night. On the 3rd day we place a second layer of fiberglass mat  pour epoxy to bond the fibers and a 4th layer of MDF (my last pair used 6mm marine grade plywood for this last layer) and the cabinet is strapped for the 3rd night. After this is the veneer or primer (actually if you want to paint the speaker there is a different variety of marine grade ply to be used made with a surface that is really smooth and ready for primer) then stain, polish and atleast 5 coats of laquer and finally buffing. 7 coats is nice, 10 coats are ideal. THe more coats the thinner each coats neads to be.

The pics below (not mine) show a "layered cabinet". Only they've used only wood.
http://clearwave.forumotion.net/t100-rbr-curved-cabinet-build

[vettett15]

Sounds like you have made some nice cabinets.  What is the purpose of the fiberglass between layers?   I was thinking of just cutting the model I show above into about ~16 1.25" MDF layers.  I would like to bond them together with the damping glue and then fill up the slots with damping compound.  I would imagine this would lead to a very solid cabinet.

[navin]

Sounds like you have made some nice cabinets.  What is the purpose of the fiberglass between layers?... into about ~16 1.25" MDF layers...I would imagine this would lead to a very solid cabinet.

I found fiberglass has a very good stiffness to weight ratio and stiffness to thickness ratio but fiberglass is resonant (I admit to only have rap-tested about 5-6mm of fiberlglass - this is 2 layers of mat layered with epoxy - vs 6mm of marine grade ply)

The fiberglass provides the stiffness, the wood provides the damping and some stiffness, and the lead provides damping and weight.

Before I got to this combo I used to make cabinets out of 30mm MDF as that is the thickest MDF we commonly get here (India). Then I built one MTM pair out of concrete (copying Rauna's Balder and I think the Freja was also concrete). The woofers were Focal 8N515 and the tweeter was Morel's MDT 33. This was a great concept but execution was terrible. If it had not been for a friend's father who was experienced with concrete I would have never got it done. Then I once dropped the speaker on my foot while moving it and realised that concrete is not practical.

Then I tried fiberlgass cabinets with a whole lot of bracing becuase I wanted to reduce weight so that less energy is stored (remember B&W's Matrix cabinets) and realised the fiberglass does add it's own sonic signature (like wood does).

I wanted to try make speakers out of aluminum extrusions but could not get extrusions big enough. I tried glass but drilling holes were diffcult - my goal was to make glass walled cabinets with hard rubber grommets holding the glass pieces together (along with glue).

Finally I settled on this combination of layers. It is cumbersome for mass market manufacturers but for 1 pair it is very doable. For damping I do a variety of things. I hang fibers of glass wood on the braces (like we hang cotton on christmas tress to absrob the energy in the box and convery it into heat (inside the fibers). I layer the inside walls with wate wood (woofer coutouts choped into quarters for exmaple) to diffused the energy that reaches the cabinet walls (like RPG diffusers).

I also prefer to make seperate baffles for each driver with a very thin sheet of rubber in between so energy transmitted to the baffle by a woofer for example is not transmitted to neighbouring tweeters.

I dont know if Rick will approve of my methods. So far they ahve worked for me, I am sure his experience far outstrips mine so as far as Selah speaker systems are concerned it is best to take his advice.

[vettett15]

Man you've tried just about everything.  My thought was to try something that has been proven out by other guys like Ryan @ Vapor.

I wonder what we are really trying to accomplish with all of these different methods..  We use thick walls and stiffeners to increase the resonant frequency which reduces deflection and thus dampening.  Then we add damping materials which add weight (thus reducing the resonant frequency) and increase dampening. 

Aren't there two things going on:

1.  The energy is causing the panels to resonant which causes noise
2.  The sound in the box is getting outside the box thus causing noise

I would think #2 is the bigger problem but it certainly depends on which part of the frequency spectrum we are talking about.  A tweeter isn't providing output in the region of the panel's resonance but a woofer certainly is.

That's why i think a combination of stiff panels to drive down deflections and sound proofing material in the walls will ultimately reduce the box's influence on the sound.  Also, damping material between panel (baffle and side panels) will help reduce energy transfer between panels.

Don't know enough to know if this would require adjustments in the cross-over or would just provide cleaner sound with the same x-over.

[vettett15]

Added sub

[navin]

Man you've tried just about everything.  My thought was to try something that has been proven out by other guys like Ryan @ Vapor.

I wonder what we are really trying to accomplish with all of these different methods..  We use thick walls and stiffeners to increase the resonant frequency which reduces deflection and thus dampening.  Then we add damping materials which add weight (thus reducing the resonant frequency) and increase dampening. 

Aren't there two things going on:

1.  The energy is causing the panels to resonant which causes noise
2.  The sound in the box is getting outside the box thus causing noise

I would think #2 is the bigger problem but it certainly depends on which part of the frequency spectrum we are talking about.  A tweeter isn't providing output in the region of the panel's resonance but a woofer certainly is.

That's why i think a combination of stiff panels to drive down deflections and sound proofing material in the walls will ultimately reduce the box's influence on the sound.  Also, damping material between panel (baffle and side panels) will help reduce energy transfer between panels.

Don't know enough to know if this would require adjustments in the cross-over or would just provide cleaner sound with the same x-over.

1. Thick (read as heavy) walls REDUCE resonant frequency
2. Thick walls also store MORE energy (which some say is released later and adds distortion to the sound- more on this later)
3. Stiffeners do increase the resonant frequency but are used to REDUCE the amplitude of the resonance.
4. Damping materials do add weight but the best damping materials would be those that convert the energy stored (potential energy) in the panels into heat which can slowly be radiated as heat and not as vibration. Remember energy cannot be created or destroyed but we can change it's form into one that is not audible (such as heat).
5. The acoustic energy inside the box needs to get out. One of the best ways are ported boxes and even better TLs and MLTLs. There is no free lunch however and every method of letting the energy inthe box comes with it's challenges for example Aperiodic boxes make the system very lossy (by their very nature).
6. I belive the layered way of making curved panels pre-stresses the wood (which is why I am now thinking of using all 4 layers of marine grade ply wood - as I can now source 100% Gurjan Ply which is very very good and void free) and pre-stressed wood is stiffer.

In the end we need to make boxes lighter (to store less energy), better damped (to suppress/release what ever energy is stored into inaudible energy) and stiffer to reduce flex so that only the cone is singing and not the box. Hence the solution of resin-bonded fiberglass (light and stiff), lead sheet and glass wool (damp and convert energy), and curved pre-stressed wood panels (stiff and reasonably damped) might offer a solution.

I do believe that Albert Von Schweikert is on to something by using different materials of different density here. This same principles are used to make soundproof doors for recording studios. The only hitch is that the panels become 60-100mm thick and can't be curved.
http://www.audiocircle.com/index.php?topic=70291.0
http://www.dagogo.com/View-Article.asp?hArticle=233

Take everything I post with a whole barrel full of salt. I am just an interested DIYer. Not a professional. I have not made many a speaker since the late 90s. I started in 1975 when I was about 12 and was in hospital for an appendix operation. My father was travelling to the US (we lived in India) at the time and when we asked me what I wanted I said "stereo system". He then told me that he can't import a whole stereo (we had punitive duties and exchange controls in those days in India) so if I promised to build the amplifier and speakers he would get me a tape deck. I was infected and got more and more interested in audio. Between 1975 and 1998 (I think) I must have made about 40 pairs of speaker - each different from the first. My 'best' years were probably between in 1986 and 1995 when I was living in the US and Europe and earning enough money (I moved to the US for education in 1981) to support my madness.

[Rick Craig]

Rick,  i wonder what would cause that... The shape alone (curved sides) would give it more rigidity than a typical box. 

Navin,  that would be the idea.  I just modeled it up as one piece to make it easy.  The only thing I would check is the strength of those adhesives because some of the ones I have found say they are not a "structural adhesive".  If it is stronger than the wood than I would say its fine.

For this I would build the baffle out of two pieces and attach them with the damping material too.  The source of the vibrations would be coming from that first baffle panel, so the more I can dampen it out before it gets to the cabinet the better.

Some shapes can create a strong resonant mode. Damping the stiff panels to reduce ringing is important as well.

[navin]

Some shapes can create a strong resonant mode. Damping the stiff panels to reduce ringing is important as well.

Rick talking about shapes what about the tear drop like shapes used in Micheal Barnes's Norh speakers and B&W'd Diamond mid and tweeter enclosures?

Another 'small manufacturer' uses a variation of this shape as well for a 2 way that competes with the Tempesta.

[Rick Craig]

Rick talking about shapes what about the tear drop like shapes used in Micheal Barnes's Norh speakers and B&W'd Diamond mid and tweeter enclosures?

Another 'small manufacturer' uses a variation of this shape as well for a 2 way that competes with the Tempesta.

The Nohr speakers I heard didn't sound very good but from what I understand the crossovers had significant problems. Some of these shapes work fine but others not so good. As far as that 2-way it's really better to compare it to the Verita.

[vettett15]

Don't think "my" shape is as exotic as those Norh speakers or even the 2-way we are talking about.  It would really be more of a fun thing for me, try and build a super dampened cabinet with some awesome components.  If it doesn't work, I scrap it and buy some pe cabinets.

Rick, do you think having braces behind the drivers is a problem?  Or would it be better/safer to have the braces in the spaces between the drivers?

[jonbee]

I've owned Norh 9.0s and I can vouch for what Rick said. Very disappointing to me, even with the Dennis Murphy crossovers.
This weekend I listened for 4 hours to a pair of very highly reviewed, fairly famous $9k floorstanders, with a very fine front end and several great amps in a dedicated, treated listening room. This model is touted for its' complex cabinet design, meant to surpress resonance. The owner has also spent a lot of time dialing them in.
Except for absolute bass extension, the Tempestas are so much better in every respect it surprised me. The other was colored, indistinct and somewhat muddy by comparision.
Studying these drawings I'm left with the thought that maybe you are trying to fix a problem that has already been fixed, and more simply and elegantly. The cabinets and damping that Rick uses seem very optimally tuned to my ears- and it is what we HEAR that counts. There is less midrange, midbass, and bass smear than anything I've owned or heard. If the cabinet talk was a problem that is where it would show up.
You MAY end up spending a lot of effort creating cabinets that don't sound as good, but I agree it may be a fun project.
Something to think about.

[vettett15]

jonbee, your points are very well taken, to sum it up we could say "leave well enough alone".  I would think it is kinda hard to know if the Tempesta cabinets don't color (even in the least) the sound unless you built some that sound "deader".  Your comparison is interesting, but obviously there are more variables there than just the cabinet.  How do I know that a completely dead cabinet would sound better anyway?  I suppose I'd be surprised if a cabinet that is stiffer and better damped could sound worse (assuming x-over adjustments are made if necessary), but anything is certainly possible.

[Rick Craig]

Don't think "my" shape is as exotic as those Norh speakers or even the 2-way we are talking about.  It would really be more of a fun thing for me, try and build a super dampened cabinet with some awesome components.  If it doesn't work, I scrap it and buy some pe cabinets.

Rick, do you think having braces behind the drivers is a problem?  Or would it be better/safer to have the braces in the spaces between the drivers?

Some of the Nohr problem was from the round baffle which is really bad for diffraction. The shape you have is similar to the cabinet I use so I don't find that to be a problem. As far as the braces that looks fine though it would be more common to have them between the drivers.

[jonbee]

How do I know that a completely dead cabinet would sound better anyway?  I suppose I'd be surprised if a cabinet that is stiffer and better damped could sound worse (assuming x-over adjustments are made if necessary), but anything is certainly possible.

Yep. There's only one way to find out. Have fun!

[navin]

I've owned Norh 9.0s and I can vouch for what Rick said. Very disappointing to me, even with the Dennis Murphy crossovers...Studying these drawings I'm left with the thought that maybe you are trying to fix a problem that has already been fixed, and more simply and elegantly.

As Rick said above much of Norh's issues lay with the round baffle. I much prefer Focal's egg baffle for the mid-hf section.

I absolutely agree that in all probablity Rick has covered all the bases....on another forum I had made a similar post...
"Many years ago (early 90s) I was visiting a rather well known speaker designer. In his lab I saw a rather simple 6" 2 way speaker half finished. I was surprised that there was a electrolytic cap in the tweeter circuit so obviously I asked. He said the cap's sonics were part of the design and when he removed the electrotytic and replaced it with a "esoteric" cap of the same value the speaker did loose it's "danceability". After that experience I dont question methods of people who know far more than I do. There is a method in their madness. In the end it is the music that matters."

But...we DIYers have an itch...we want to know why, how, which for everything. Sometimes we overstep our boundaries not realising that we are infringing on the intellectual property of the professionals.

BTW even while considering Rick's designs for my living room and bedroom I am considering building a speaker whose internals may look something like this (see link http://www.weidinger-online.de/tml/seas.html ) using other drivers I happen to have around. Just to scratch that itch!

It's a diesease!