A lot of the expensive builds I see use this layered approach with irregular curvy insides, I assume to prevent standing waves?
Example:
http://www.thesoundstation.com/caffeine/uploads/files/pbn.sammy.2.jpg
For cheap builders like me cnc'ing a cabinet from layers like these isnt really an option, as its very wasteful and requiring lots of mdf.
But I was wondering - for people who build standard square boxes like me,
Would it be a good alternative to cut out wavy strips like that and glue them to the inside of the standard square box?
I could imagine it's lots cheaper to build a standard box, and have one piece of mdf cnc'ed into lots of strips with one straight edge and curves on the other side, so you could cut them to size and glue these stripe on the inside of the usual cheap coffin..?
(I hope you get what I mean?)
Example:
http://www.thesoundstation.com/caffeine/uploads/files/pbn.sammy.2.jpg
For cheap builders like me cnc'ing a cabinet from layers like these isnt really an option, as its very wasteful and requiring lots of mdf.
But I was wondering - for people who build standard square boxes like me,
Would it be a good alternative to cut out wavy strips like that and glue them to the inside of the standard square box?
I could imagine it's lots cheaper to build a standard box, and have one piece of mdf cnc'ed into lots of strips with one straight edge and curves on the other side, so you could cut them to size and glue these stripe on the inside of the usual cheap coffin..?
(I hope you get what I mean?)
No, it is a stupid novelty for milking extra money from unsuspicious audiophiles.
No, it is waste of time and money.
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You probably can get some answers from this similar thread: Innerchoic cabinets - should I?
I have used the wavy shaped insides myself in my build:
I don't think the wavy shape does that much for breaking up waves inside the enclosure, I mostly wanted the rounded exterior shape which certainly does have actual acoustic benefits. One thing the wavy shape does have going for it is the irregular wall thickness. I don't regret all that work (non CNC with a simple router and templates)
As said, the outer shape was much more important to me. The wavy cabinet (irregular) still needs damping materials on the inside, though the end result for the cabinet as a whole was very pleasing and inert. The irregular wall thickness does have advantages compared to flat panels i.m.h.o. I'd never use MDF for any of it though.
It did not take much more material, as I used U shaped parts that I could pattern optimally. The huge stack I made (2.25 Meter) was prone to cracking though. Hence it got divided into smaller parts and an epoxy/matt outer skin.
I have used the wavy shaped insides myself in my build:
I don't think the wavy shape does that much for breaking up waves inside the enclosure, I mostly wanted the rounded exterior shape which certainly does have actual acoustic benefits. One thing the wavy shape does have going for it is the irregular wall thickness. I don't regret all that work (non CNC with a simple router and templates)
As said, the outer shape was much more important to me. The wavy cabinet (irregular) still needs damping materials on the inside, though the end result for the cabinet as a whole was very pleasing and inert. The irregular wall thickness does have advantages compared to flat panels i.m.h.o. I'd never use MDF for any of it though.
It did not take much more material, as I used U shaped parts that I could pattern optimally. The huge stack I made (2.25 Meter) was prone to cracking though. Hence it got divided into smaller parts and an epoxy/matt outer skin.
Hah! I think your build may have been one of my reads going "hm I might need to look in to that" 
You say it still needed damping - I assume that's not a matter of bitumen or felt applied since that would be fairly impossible on cabinet walls like these.
So what's the reason for building the walls with the inside shape like this?
You say it still needed damping - I assume that's not a matter of bitumen or felt applied since that would be fairly impossible on cabinet walls like these.
So what's the reason for building the walls with the inside shape like this?
I agree with this, but the building time and effort are huge.
Shape doesn't need to be wavy, any irregular pattern will do.
Damping was done with wool felt (on the walls) and fiberglass insulation.
Checked with impedance plots to get the best result. There's even some automotive damping materials in there, the butyl + alu foil kind, Silent Coat.
And mass loaded vinyl and butyl rope and aluminium damped baffles, I went all out.
As to the why? To get a wall thickness that varies all over the place, It can't hurt that it has no parallel planes inside but for the most part: I wanted the continuously curved outside shape and this was the easiest way to get it.
That outside shape really does work. I've seen stacked constructions, very similar to mine but they still have corners at the front baffle. I see that as a missed opportunity. The main reason for me to use a stacked construction was the outer shape, the rest was bonus at little cost. Well, except for the blood, sweat and tears.
Checked with impedance plots to get the best result. There's even some automotive damping materials in there, the butyl + alu foil kind, Silent Coat.
And mass loaded vinyl and butyl rope and aluminium damped baffles, I went all out.
As to the why? To get a wall thickness that varies all over the place, It can't hurt that it has no parallel planes inside but for the most part: I wanted the continuously curved outside shape and this was the easiest way to get it.
That outside shape really does work. I've seen stacked constructions, very similar to mine but they still have corners at the front baffle. I see that as a missed opportunity. The main reason for me to use a stacked construction was the outer shape, the rest was bonus at little cost. Well, except for the blood, sweat and tears.
Sure, but this was an easy decision for me as I wanted to get that outside shape. I don't mind going all out on a build like this. I don't regret any minute of it. Even if it did take me over a year to build it (with breaks). It was a bit like therapeutic work at that time, and I enjoyed every minute of it. These speakers will last me a long long time, that was the intention from the start. I'm not in this hobby to try something new once I grow tired of the previous build or concept. I went with something I believed in, planned it for almost 2 years, building it took over a year and getting the most out of it took at least another year. And I'm still toying with it to learn more.
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I have been building coffin speaker boxes for 40 years without any problems.
I have occasionally branched out into bass reflex and W bins.
KISS keep it simple.
We all have different standards of what simple is .
As long as you're having fun with it, it serves its purpose. I like a good challenge.
As a mechanical engineer I've done far more complicated stuff. I agree with the KISS principle though, whatever it may mean for each of us.
Another cliché I really like in everything I do: form follows function.
.As long as you're having fun with it, it serves its purpose. I like a good challenge.
As a mechanical engineer I've done far more complicated stuff. I agree with the KISS principle though, whatever it may mean for each of us.
Another cliché I really like in everything I do: form follows function.
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I do want to keep it simple as my budget and lack of knowledge only allows me to build a diy kit costing maybe 500 euros per speaker max...
I was just wondering if there was anything "smart" I could do to improve the build that wouldn't break the bank.
I thought that if all pro builds here use that wave pattern inside the cabinet, there might be a way to include something like that without going all the way layering the entire cabinet.
And if not, I can learn from all the responses here
Keep in mind I'm doing this as a hobby - for fun. Im not here to intentionally post bad ideas to **** people off...
We all have to start somewhere, and we're all looking for stuff we can improve, I hope
I might just be where you guys were 20 years earlier
I was just wondering if there was anything "smart" I could do to improve the build that wouldn't break the bank.
I thought that if all pro builds here use that wave pattern inside the cabinet, there might be a way to include something like that without going all the way layering the entire cabinet.
And if not, I can learn from all the responses here
Keep in mind I'm doing this as a hobby - for fun. Im not here to intentionally post bad ideas to **** people off...
We all have to start somewhere, and we're all looking for stuff we can improve, I hope
I might just be where you guys were 20 years earlier
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Good luck on whatever you decide to go for. No shame in building something pré designed. Just the learning experience by itself and the pride of doing it yourself are well worth it.
Read the thread I linked earlier, many more replies on the same subject. Take your time to find something you believe in, build it with pride!
Read the thread I linked earlier, many more replies on the same subject. Take your time to find something you believe in, build it with pride!
The cabinet is essentially there to prevent low frequency cancellation and to provide some air loading for the bass driver at low frequencies for better acoustic output.
As the wavelengths are so long at those low frequencies internal structures have little effect and all that is produced is a rise and fall of internal pressures. As wavelengths get much shorter internal structures begin to have an effect in the reflection of internal waves, here too absorbent materials are most effective.
It is essential that the enclosure be rigid and braced securely to minimize panel vibration which would otherwise be another vibrating surface with its own contributing resonances.
A great deal of the cost in loudspeaker manufacture of course goes into cabinet design and finish with the added detriment of a boxy colouration of the air trapped within. Getting rid of that colouration is a challenge in itself and is usually only partly successful.
C.M
As the wavelengths are so long at those low frequencies internal structures have little effect and all that is produced is a rise and fall of internal pressures. As wavelengths get much shorter internal structures begin to have an effect in the reflection of internal waves, here too absorbent materials are most effective.
It is essential that the enclosure be rigid and braced securely to minimize panel vibration which would otherwise be another vibrating surface with its own contributing resonances.
A great deal of the cost in loudspeaker manufacture of course goes into cabinet design and finish with the added detriment of a boxy colouration of the air trapped within. Getting rid of that colouration is a challenge in itself and is usually only partly successful.
C.M
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Probably doesn't do anything significant. I built enclosures with curved sides very similar in profile to yours, but instead of a big stack like yours mine are a bent lamination of six 3mm MDF sheets so I have a constant thickness of ~18mm. If I put my ear up to a curved side there is amazingly little resonant sound compared to when I put my ear to the top of the cabinet which is flat 16mm MDF sheet. I believe this is mostly due to the curve itself - like when you hold a piece of paper in a curved shape it is much stiffer in one direction compared to if the paper is just held flat.
As far as I'm aware, the external profile of the curved sides does almost nothing of benefit. The roundover at the front edge of the cabinet is most critical. Simply having a enclosure with straight sides tapering in towards the rear would be functionally almost identical if the roundover on the front is the same radius.
Internally, just having tapered side walls would also reduce standing waves by similar amounts to the curved sides.
It should bring some benefits: they should "deflect" the secondary waves- reflections from the side walls and objects - so that they are spreaded more than a planar baffle
The goal is to have less "out of time" ghost sounds coming from the cabinet, near the first source of sound, the speakers.
The pertebations inside the box need to be a significant portion of a wavelength to be affected. The box you linked as an example, is a multiway, and the size of th eperyebation is so small that its affect will be above the passband of the midbass.
The B&W 302 is a loudspeaker that has sufficient pertebation to be effective at frequencies produced by the midbass.
Use quality plywood, not mdf.
dave
The B&W 302 is a loudspeaker that has sufficient pertebation to be effective at frequencies produced by the midbass.
Use quality plywood, not mdf.
dave
Bent sheets are inherently very stiff, glue between sheet layers add up to better damping, so the result is a very good enclosure (almost "composite" material).
On the other hand, different shapes of stacked flat layers may contribute to better dissipation of resonances inside the MDF enclosure as a whole. If there are only two different layers as a building blocks (as in the shown examples), there are two different resonances instead of one unison resonance with bigger amplitude.
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