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Speaker Cabinet Design Considerations

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Is this from one of Dr. Harry Olson's books or papers? If so, could you please add a citation to your post? Thanks! I wish people would give him credit. So much is based upon his work.

(Not an issue of copyright necessarily, but rather proper credit and respect. I have no idea which if any of his books have had copyright extended in the U.S. or elsewhere.)

I'm with you, Hugo. Rather than wait for the citation, here's the whole paper. You're right, Dr. Olson is the source.
 

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It would be interesting for @amirm to repeat Dr. Olson's experiment with his advanced rig, no? There'd be so much more data! I'd be interested to see the outcome of introducing reflections as a variable, too. Maybe speaker boxes should be chamfered on every edge! Who can whip up a couple dozen cabinets for the same tiny driver?
 
I'm with you, Hugo. Rather than wait for the citation, here's the whole paper. You're right, Dr. Olson is the source.
Thanks very much, I didn't have that paper in my collection! :) Presented in 1950--I wonder if there was any other researcher/scientist/engineer in these fields who shared his work so openly as Dr. Olson. (And kudos to RCA Labs from that era, for being willing to share so much valuable research and knowledge with the public and obviously sharing it with competitors in the process!)
 
Thanks very much, I didn't have that paper in my collection! :) Presented in 1950--I wonder if there was any other researcher/scientist/engineer in these fields who shared his work so openly as Dr. Olson. (And kudos to RCA Labs from that era, for being willing to share so much valuable research and knowledge with the public and obviously sharing it with competitors in the process!)

No sweat!

Come to think of it, a sphere/egg is just an infinitely chamfered box. 1950 is clearly still way ahead of me :) Still, chopping a few extra corners off of boxes but keeping the interior shape the same for convenience seems like a small but potentially worthwhile thing to try
 
Baffle shape is one parameter to consider, it has huge impact on sound.

We started doing edge round-offs and separate egg or spherical hf-sections back in the 80ies. This evolved into acoustic absorption damping on the baffle surface. The round-off and damping reduces diffraction, which can improve imaging/sound-stage, makes the speakers disappear better. And it does. Imaging did improve.

My new designs have no significant round-off, no damping on the baffle. And they have imaging and sound-stage that you would not believe possible back then, even if you heard it. So there are several ways to do this.
 
Might as well add some observations on cabinet material and such;

Almost any sorts of cabinet material and mechanical construction have been tried by different manufacturers through the years. Wood, chipboard, MDF, HDF, panzerholz!, plywood, plastic materials, concrete, metal - aluminum, sandwich laminates of combinations of those materials, and the ultimate - sand filled totally dead boxes.

All claim to be the ultimate solution to the seemingly unsolvable mystery of cabinet vibration and panel resonances.

If any of those were superior, would it not be so, that eventually all good speakers were made using that material? Instead, we continue to see all sorts of cabinets, and from what I can see, there is no good correlation between type of cabinet material and sound quality.

There is, however, a correlation between execution - how it is used, shape, thickness, physical cabinet design - and sound quality.

I have ended up choosing to make the cabinet reasonably dead and rigid, and free from any obvious resonances, and then believe there is little to be gained by further chasing the totally dead box. But of course, I can be wrong.

There are reasons why this approach makes sense - technical and measurable reasons. Because other properties of the cabinet easily end up obscuring what is left from resonances and emitted sound from the cabinet itself.
 
Unsure how much of an audible difference it makes, but when I look at a speaker cabinet, I'm looking for a a few things ideally:

-No parallel surfaces
-No sharp edges along the entire front
-A waveguide or a front that is spherical
-Not shaped like a box
Am sure you already know it, but I better to add for the readers that we have to be carefully about such "binary" generalisations.

For example parallel casing surfaces are not a problem when the wavelengths of the woofer cone driver frequency range (mids and and tweeters usually have their own internal housings) are larger than its dimensions. Also for floorstanders which have one dominant internal standing wave due to their length you can use (and actually some do so) internal Helmholtz resonators to suppress it.

Also even a flat front surface can be used if it has cleverly designed waveguides even for the midwoofers, see for example http://www.kef.com/uploads/files/THE_REFERENCE/REF_White_Paper_preview_path_200514.pdf chapter 4.1.4
 
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Material? plumb but you know, it is prohibited.

As I have commented several times already, my KEF Q100 (5.9 Kg) are of thin MDF, full of white absorbent, without any damping material. Now they weigh more than the KEF LS50 (7.2 Kg) after adding mass and damping -> substantial improvement in the sound quality.
 
Material? plumb but you know, it is prohibited.

As I have commented several times already, my KEF Q100 (5.9 Kg) are of thin MDF, full of white absorbent, without any damping material. Now they weigh more than the KEF LS50 (7.2 Kg) after adding mass and damping -> substantial improvement in the sound quality.

What is plumb? Do you mean plum, the fruit tree? Why is plum wood prohibited?

I haven't seen any comments about q100, I suppose you mean in other threads. What sort of damping did you add? And mass? Was this inside the cabinet? If so, how did you adjust the port length to compensate for the change in internal volume? New tubes? Those cabinets are really small!

Is your typeface some sort of code? The colors and bold letters and such? So many questions
 
What is plumb? Do you mean plum, the fruit tree? Why is plum wood prohibited?

I haven't seen any comments about q100, I suppose you mean in other threads. What sort of damping did you add? And mass? Was this inside the cabinet? If so, how did you adjust the port length to compensate for the change in internal volume? New tubes? Those cabinets are really small!

Is your typeface some sort of code? The colors and bold letters and such? So many questions

Maty is Spanish. Plumb (plomo) = lead

plumber /ˈplʌmə/

noun
noun: plumber; plural noun: plumbers
1. a person who fits and repairs the pipes, fittings, and other apparatus of water supply, sanitation, or heating systems.







Origin
late Middle English (originally denoting a person dealing in and working with lead): from Old French plommier, from Latin plumbarius, from plumbum ‘lead’.
 
First I wrote lead but after I edited as plumb :facepalm:

Viscoelastic material. Years ago, bitumen / asphalt as BBC loudspeakers series. Tecsound SY70. About 38 € in the professional store, a great roll!

Many years ago, absorbent with compressed fiberglass. After, rockwool. My bigger loudspeakers with strange 3-ways crossover design has a sandwich of TS70+acrylic sealant+TS70+acrylic sealant+compressed fiberglass.

big-3-way-speakers-sandwich-tecsound-acrylic-fiberglass.jpg


And yes, the typace has some codes. The first, the evident, cookie monster, but in Spain the Muppets...


PS: I have a problem. After 22 years Galeon have canceled the free hosting service I used with the images (FTP service). I have a copy of 99% images and files but the old links do not work more :facepalm:
 
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Ahh, thanks guys!

Yeah that would be useful. Nice and soft, you can smear it around a cab interior, or easily work with a thin sheet. High density, so won't alter your cab volume much. Soundproofing properties.

Is the dampening capability of lead still as useful in a very small enclosure?
 
Ahh, thanks guys!

Yeah that would be useful. Nice and soft, you can smear it around a cab interior, or easily work with a thin sheet. High density, so won't alter your cab volume much. Soundproofing properties.

Is the dampening capability of lead still as useful in a very small enclosure?
It is worthwhile knowing a bit about sound transmission/reflection when thinking through what to do.
Imagine two adjoining rooms with noise sources in both and you in one of them.
If you put sound "absorption" foam on the wall on the room you are in it will become quieter by reducing the reflections from the walls but if you put the same in the adjoining room only it will make no difference in the room you are in.
If you put a sound barrier on the adjoining wall - usually just mass - it will reduce the noise coming through the wall.
If you put a dampening layer on the wall it will reduce resonant transfer but may not have much effect on simple transfer.
When I used to make kit speakers I used a proprietory material called Coustilam FS. This had about ¼" of foam then 1/16" lead then 1" of foam. With the ¼" foam bonded to a wall the 1" foam acts as an absorber, the lead as a barrier and the ¼" foam as a damper.
It worked quite well but we are talking 1970s here and lead is harder to find now.
 
If you put sound "absorption" foam on the wall on the room you are in it will become quieter by reducing the reflections from the walls but if you put the same in the adjoining room only it will make no difference in the room you are in.

You said sound sources in both rooms, right? Wouldn't absorption in the other room attenuate the sound from the other source, and reduce your exposure to it in the room you're in?
 
You said sound sources in both rooms, right? Wouldn't absorption in the other room attenuate the sound from the other source, and reduce your exposure to it in the room you're in?
Not really.
"sound absorbers" considerably reduce reflection from walls but not transmission through them.
It is a common mistake to think sound transmission will be effected a worthwhile amount (because of the name) but it isn't, you need mass (or blocking any tiny hole) to make a difference of consequence.
 
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