Diffraction - coaxial tweeter? - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

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 December 2003, 07:48 AM   #1
Serow is offline Serow  Canada
diyAudio Member
 
Join Date: Feb 2002
Location: Regina, SK, Canada
Default Diffraction - coaxial tweeter?

I have a 7 inch "full range" driver and a small tweeter that I'd like to mount coaxially in front of the full ranger, something like the following:

Click the image to open in full size.

From my reading, an obstruction with a size less than the wavelength of interest is basically invisible, as the sound wave will diffract around the object.

In my case, the size of the tweeter is about 4 cm and therefore theoretically should not affect the output of the full-range until around 6000 Hz. Do you think that mounting the tweeter in this manner will be detrimental to the sound of the full range driver?

I was also thinking of adding a layer of absorptive material to the back of the tweeter to reduce high-frequence reflections.

Thanks,
Eric

(P.S. planet10, the drivers look great and were packed superbly. Cheers.)
  Reply With Quote
Old 21st December 2003, 01:40 PM   #2
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Default Re: Diffraction - coaxial tweeter?

Quote:
Originally posted by Serow

In my case, the size of the tweeter is about 4 cm and therefore theoretically should not affect the output of the full-range until around 6000 Hz. Do you think that mounting the tweeter in this manner will be detrimental to the sound of the full range driver?

I was also thinking of adding a layer of absorptive material to the back of the tweeter to reduce high-frequence reflections.

The results from the arrangement in the picture would be very poor.
But you say your tweeter is only 4cm diameter which should be OK.

One option is to remove the drivers dustcap and mount the tweeter
on an extended pole piece, airflow needs to be smooth.

But there are cogent reasons not to mount the tweeter in such
a fashion if you are running the main driver full range without a
crossover.

What crossover arrrangments are you thinking of ?

sreten.
  Reply With Quote
Old 21st December 2003, 03:49 PM   #3
Serow is offline Serow  Canada
diyAudio Member
 
Join Date: Feb 2002
Location: Regina, SK, Canada
Default Re: Re: Diffraction - coaxial tweeter?

Quote:
Originally posted by sreten


But there are cogent reasons not to mount the tweeter in such
a fashion if you are running the main driver full range without a
crossover.

What crossover arrrangments are you thinking of ?

sreten.

Thanks for the reply. The crossover, if it can be called such, will be a series cap for the tweeter with a crossover point of 4000-6000 Hz and the main driver will be run wide open.

I was thinking that I should mount the tweeter as close to the main driver as possible. As far as lobing goes, where should the tweeter be in relation to the main driver - above, below, etc?

Eric
  Reply With Quote
Old 21st December 2003, 04:57 PM   #4
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
If the drivers are not too high directly below as close
as possible will probably give the best results.

You should also consider attenuation of the tweeter
for good matching.

sreten.
  Reply With Quote
Old 21st December 2003, 06:37 PM   #5
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
I've got a set of 8" whizzer full rangers, i was going to play with co-axially mounting the same tweeters to.

I was thinking of just building an "H-shaped" cross piece which the tweeter sits in the middle of, and adding ductseal to the back of the T to give it a nice smooth shape (even naked they aren't a bad shape). This assembly would then just velcro to the cabinet. I'll also probably continue my tweeter phase plug experiments with these.

dave
Attached Images
File Type: gif tweeter-mount.gif (22.7 KB, 371 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 21st December 2003, 06:55 PM   #6
diyAudio Member
 
RobWells's Avatar
 
Join Date: Aug 2002
Location: UK
what about using 4mm metal rod rather than wood etc, and welding/ epoxying the tweet to that ? (possibly some kind of drawer handle could work?

The mounts for the Linn speaker's tweet/supertweet would be bigger than a rod.(I'll post a link in a sec..)

Rob

edit link and pic:

http://www.linn.co.uk/spec_sound/pro...inn.co.uk/#174
Attached Images
File Type: jpg product_shot_komri.jpg (9.7 KB, 359 views)
  Reply With Quote
Old 21st December 2003, 06:56 PM   #7
Serow is offline Serow  Canada
diyAudio Member
 
Join Date: Feb 2002
Location: Regina, SK, Canada
Dave, I was initially planning on using an appropriately-sized metal door pull to mount the tweeters coaxially. Just bolt the tweeter on one side, and screw it to the enclosure right beside the FR.

Are you still using foam ear plugs to make the phase plugs for the tweeters? How does the existing dust cap come off?

Also, where did you find the ductseal - the stuff I've found has a quite liquid composition that wouldn't seem to hold itself together on the drivers.

ERic
  Reply With Quote
Old 21st December 2003, 07:24 PM   #8
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Quote:
Originally posted by Serow
Are you still using foam ear plugs to make the phase plugs for the tweeters? How does the existing dust cap come off?
Yes, still playing with them. I use a heat gun to lossen the glue and then pry it off with a knife.

Dusctseal should be avalable at heating/air conditioning supply wholesalers.

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 December 2003, 01:08 AM   #9
diyAudio Member
 
Brett's Avatar
 
Join Date: Jan 2002
Quote:
Originally posted by planet10
I was thinking of just building an "H-shaped" cross piece which the tweeter sits in the middle of, and adding ductseal to the back of the T to give it a nice smooth shape
Something like this? They sound quite good, better in some ways than my 12" red.
Attached Images
File Type: jpg peak 10cx small.jpg (9.1 KB, 333 views)
  Reply With Quote
Old 2nd January 2006, 02:37 PM   #10
konut is offline konut  United States
diyAudio Member
 
Join Date: Apr 2005
Location: Pacific Northwest
Heres a company that uses this technique for some very well reviewed pro studio monitors. http://www.me-geithain.de/index.html
  Reply With Quote

Reply


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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Pioneer B20 Coaxial Tweeter Install db6546 Full Range 13 6th December 2008 02:18 AM
Waveguide tweeter and baffle diffraction breez Multi-Way 0 25th July 2008 10:24 PM
Tweeter Above Enclosure - Diffraction Issues? tschanrm Multi-Way 7 20th February 2008 06:08 PM
4 way + coaxial midrange/tweeter Thomasjunta Multi-Way 0 30th April 2007 06:06 PM
Strange coaxial tweeter from Swans/HiVi Snickers-is Class D 1 19th July 2006 07:02 PM


New To Site? Need Help?

All times are GMT. The time now is 01:18 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2