Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Multi-Way Conventional loudspeakers with crossovers

Curved sided speaker enclosures, why?
Curved sided speaker enclosures, why?
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 21st January 2009, 10:38 PM   #21
bear is offline bear
diyAudio Member
 
bear's Avatar
 
Join Date: Apr 2002
Location: New York State USA
Ummm... if you want to do something about transmission through speaker walls, you do not want an airspace inbetween. You want something that will convert the sound energy to something else... what would that be? That would be heat.

That's how it works...

The thing to put between cabinet walls is something like sand or glass beads. That works.

For box wall transmission you want to thing two things: damping and absorption. Stiffness works only in concert with the those two as a system.

You can make a curved surface for a cabinet without creating any tension on the curved bit of whatever it is... plywood for example you could cut kerfs and bend, you could steam bend it, you could mill it out of solid wood, or mill it out of MDF. So unless you deliberately create some tension, there won't be any.

Tension, what does it do to resonant frequency?
Is that good?

Internal "early reflections" do not bounce around enough to make any real world difference at frequencies of interest - comparing a "right angle" box with a curved surface box...

Again, you have to take a minute to calculate the wavelength (dimension)of the wave, ie. frequency, and see if that 1/4 wave or 1/2 wavelength (or other multiple) is of any scale near the dimensions inside the cabinet - and then figure out what effect your internal treatment will have.

chris661 wrote:
Quote:
The idea behind them is to make 0 loading by air pressure on the tweeter, to allow movement more freely. Like those speakers that have channels inside the speaker cabinet which makes the pressure dissipate as it goes through the chanel.
I'm not sure what you are referring to here. But if you are talking about internal cabinet pressure effecting the tweeter (diaphragm), then the problem is not with the cabinet per se, but that the tweeter has not been isolated from the cabinet volume.

The tweeter should always be isolated from the cabinet volume!! Tweeters are not designed to be "air tight" at all. One should always put them in a sealed section or place a "cup" or "box" behind them that is very very well sealed!

I would think that using the case of a tweeter with a vented pole piece that this idea would be made be self-evident?
__________________
_-_-bear
http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- every once in a while I say something that makes sense... ]
  Reply With Quote
Old 22nd January 2009, 01:59 AM   #22
bear is offline bear
diyAudio Member
 
bear's Avatar
 
Join Date: Apr 2002
Location: New York State USA
I just noticed that the Nautilus design was referenced... not sure that the tweeter is open in the back, and if it is, if this is significant? ... to the extent that it is sitting on the end of a reverse cone that is not stuffed at all... given that the length of the back cone is then long compared to the wavelength, I'd expect that it looks somewhat like an infinite baffle, or at least a transmission line of sorts... and in that case there would be very little HF energy to reflect back directly, except in the case where the volume at large would resonate - which presumably is below the F3 of the driver by some margin...at least that's what I thought about that... dunno if that matches the reality or not?

A long tapered pipe...eh?

_-_-bear
__________________
_-_-bear
http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- every once in a while I say something that makes sense... ]
  Reply With Quote
Old 22nd January 2009, 02:02 AM   #23
planet10 is offline planet10  Canada
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Curved sided speaker enclosures, why?
Quote:
Originally posted by cirrus18
Well, if this is a problem and everybody is going down the road of thicker and heavier enclosure walls how about thinking of something different and possibly better .... To my mind the gap between the double glass facings is attenuating the sounds from the road dramatically. Couldn't this apply to speaker cabinet making?
Not me on the 1st point...

Instead of reiterating my build stiff, high frequency panel resonance box methodology it is explained in detail here http://www.diyaudio.com/forums/showt...threadid=98834

On the 2nd you are describing the major panels on the Fonken s(or any Onken for that matter)

Click the image to open in full size.

They aren't perfect but they do work very well.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 22nd January 2009, 02:04 AM   #24
planet10 is offline planet10  Canada
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Curved sided speaker enclosures, why?
Quote:
Originally posted by bear
Nautilus design was referenced... not sure that the tweeter is open in the back, and if it is, if this is significant? ... to the extent that it is sitting on the end of a reverse cone that is not stuffed at all... given that the length of the back cone is then long compared to the wavelength, I'd expect that it looks somewhat like an infinite baffle, or at least a transmission line of sorts...
It is a half-wave (terminated) transmission line. Where did you get the idea that there is no damping?

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 22nd January 2009, 05:03 AM   #25
Cloth Ears is offline Cloth Ears  Australia
diyAudio Member
 
Cloth Ears's Avatar
 
Join Date: Dec 2001
Location: Melbourne, Australia
Quote:
Originally posted by planet10
For the outside of a loudspeaker (actually the shape used in the B&W Nautilus 801 is better). For the inside of a loudspeaker it is worst.

dave
Agreed re internals, sphere is the worst shape. Olsen found that the sphere and the (like Dave's Fonkens, but with another big bevel on the top edge) were the best baffle shapes. Article is here. Mods - if you don't like the picture posted (from the above article), please remove it.

But this is about the rear shapes, and yes, it does improve standing wave performance, but it also allows for a larger speaker to sit in the same position (ie. good SAF).
Attached Images
File Type: jpg olson.jpg (79.6 KB, 1163 views)
__________________
Jont.
"It is impossible to build a fool proof system; because fools are so ingenious."
  Reply With Quote
Old 22nd January 2009, 05:17 AM   #26
Drew Eckhardt is offline Drew Eckhardt  United States
diyAudio Member
 
Join Date: Jun 2003
Location: Menlo Park, CA
Quote:
Originally posted by bear

As far as -40db down being important, I'd say that it is, but show me an enclosure that has the rear reflected energy down -40db?

Linkwitz Pluto

SL measured a 40dB return loss on the mid/bass enclosure after determining an appropriate stuffing quantity and density.

Some place there is or was a description of the bursts he used to measure it and the resulting graph.

Quote:
And, let's understand that a standing wave means nothing unless it is radiated through the diaphragm and out of the box... what we're really talking about is reflected energy, and if a standing wave at some frequency will cause a peak or dip in the response.
Perhaps more noticeable as a time domain stored energy aberation.

Quote:
Obviously the ideal enclosure has no baffle step, radiates nothing, and has zero reflected internal energy... anyone got one?
Pluto's baffle step starts around 2.5KHz. The 1.7" tweeter is getting directional at that point so it doesn't diffract too much at higher frequencies.

The ABS sewer pipe is also round, so pressure waves attempting to deform the enclosure are trying to stretch it instead of deflect it. There's an AES paper where the abstract says the round enclosure was as stiff as 4" concrete; I should renew my membership and read it for fun as a $5 download.

Absorbing 99% of the internal energy is close enough to zero for an engineer who is thinking about masking effects.

Any one with a soldering iron and screw driver could build a pair. Easy.

Driver cost is about $140/pair. The six (woofers are bridged) channels of amplification and active cross-overs are in line with what you'd spend on passive cross-overs and a used mid-fi stereo amplifier. Inexpensive.

It's really a wonderful piece of work. I like my Orions more than my Plutos, but doing so much with so little impresses me more as an engineer.

The B&W Nautilus shares the same small baffle, damped transmission line, active cross-over concept. While its SAF is probably a lot higher, output limits from the 4-way higher, and tapered transmission lines "better" the price tag and need for external amplification make it less accessable than the Pluto or average German sports sedan.
Attached Images
File Type: jpg pluto.jpg (14.4 KB, 1135 views)
  Reply With Quote
Old 22nd January 2009, 07:26 AM   #27
planet10 is offline planet10  Canada
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Curved sided speaker enclosures, why?
Quote:
Originally posted by Cloth Ears
[Mods - if you don't like the picture posted (from the above article), please remove it.
Someone sure mangled that picture... things like that should never be jpgs.

Thanx for the link to the article. That adds the 2 rectangular shapes at the bottom to what he has in his book Acoustics... here are the pages from that.

dave
Attached Images
File Type: gif page2223-olson.gif (54.5 KB, 1130 views)
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 22nd January 2009, 10:47 AM   #28
HK26147 is offline HK26147  United States
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally posted by annex666
I'm surprised that no-one has mentioned the baffle step yet, so I'll chirp in...
A while back I posted an inquiry for links to software that could generate diffraction patterns for any given design like the following:

http://www.acoustics.hut.fi/demos/di...IIndorder.html

To an extent you can see trends in evolution in enclosure shape.
Set-back baffles were the norm in cabs in the past. Then baffles became flatter. Now virtually every cab has at least a little round-over.
With advances material science and fabrication, non-rectilinear enclosures are more common.
  Reply With Quote
Old 22nd January 2009, 08:45 PM   #29
HiFiNutNut is offline HiFiNutNut  Australia
diyAudio Member
 
Join Date: May 2004
Location: Sydney
I don't have the means to do the measurements but would the sound transmit through the panels be substantially lower (e.g. 40-60dBdB) than the direct sound (unless your panels are paper thin)? hence transmission becomes a non-issue? Point me to some solid measurements to convert me if otherwise.

Also, would the effects of the box internal reflections be magnitude higher than box / panel resonances? I would assume so. Again, point me to some solid measurements to convert me if otherwise.

Regards,
Bill
  Reply With Quote
Old 23rd January 2009, 12:00 PM   #30
delphiplasma is offline delphiplasma  United Kingdom
diyAudio Member
 
Join Date: Dec 2007
Hi,

I see that there has been reference to Pluto's cylindrical enclosures. How would internal standing waves, in a cylindrical cabinet, compare to a flat panel cabinet with no parallel walls?

Thanks
  Reply With Quote

Reply


Curved sided speaker enclosures, why?Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


New To Site? Need Help?

All times are GMT. The time now is 03:51 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki