Geddes on Waveguides - Page 701 - 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 20th June 2014, 02:28 AM   #7001
diyAudio Member
 
Kindhornman's Avatar
 
Join Date: Aug 2012
Location: Los Angeles, California
I hear you Patrick! I'm still riding sewup tires so they handle higher pressure than a tire and tube.

Just keeping the conversation going Earl. Got anything new to add about horns. I see you do what I would say I pioneered with urethane years ago. Do you actually make your own horns, mold the urethane? I used and still use high density 65pcf rigid foam for all the things I have done. If you don't make your own tooling things can get rather expensive fast.
  Reply With Quote
Old 20th June 2014, 02:22 PM   #7002
gedlee is online now gedlee  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Novi, Michigan
Yes, I mold my own horns but the polyurethane is not foam. I make some of my own tools and buy some parts from a tool and die house.
  Reply With Quote
Old 16th August 2014, 12:50 AM   #7003
diyAudio Member
 
Join Date: Sep 2008
Location: Bristol
Is there a golden rule for XO slopes for OSWG / Conical horns?
  Reply With Quote
Old 16th August 2014, 01:30 AM   #7004
badman is offline badman  United States
diyAudio Member
 
badman's Avatar
 
Join Date: Sep 2003
Location: Sunny Tustin, SoCal
Quote:
Originally Posted by Studio Au View Post
Is there a golden rule for XO slopes for OSWG / Conical horns?
One good method:

You can cross higher, electrically first order, and if you tune it right, it can allow you to use the same cap for protection with about a 3rd order final slope, as well as to provide the constant directivity EQ- but you may still need some impedance compensation etc, and it does demand a robust driver.
__________________
I write for www.enjoythemusic.com in the DIY section. You may find yourself getting a preview of a project in-progress. Be warned!
  Reply With Quote
Old 16th August 2014, 10:31 AM   #7005
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
with about a 3rd order final slope
Is this assuming the waveguide creates a 2pole roll-off?
__________________
regards Andrew T.
  Reply With Quote
Old 16th August 2014, 01:13 PM   #7006
gedlee is online now gedlee  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Novi, Michigan
Quote:
Originally Posted by Studio Au View Post
Is there a golden rule for XO slopes for OSWG / Conical horns?
The short answer is no, there is no golden rule - whatever works. Since the passband of a waveguide is not flat (it falls with frequency) the compensation is really part of the crossover.
  Reply With Quote
Old 16th August 2014, 04:13 PM   #7007
badman is offline badman  United States
diyAudio Member
 
badman's Avatar
 
Join Date: Sep 2003
Location: Sunny Tustin, SoCal
Quote:
Originally Posted by AndrewT View Post
Is this assuming the waveguide creates a 2pole roll-off?
It's not really that simple- you've got the highpass power characteristic of the compression driver, which ends at about 2nd order, but then the cutoff of the waveguide on top of that. It winds up being a multi-stage cutoff characteristic unless you really hammer it with the crossover, 3rd is just a rule of thumb for the slope immediately below where you'd typically want to have equal amplitude response (the crossover point but not the electrical crossover point as far as the C.D. is concerned).

I hope that helps, it's just my experience and others may feel otherwise. The behavior of the CD/Waveguide/Horn combo will really define what you have to do, if you had to reduce the low end cutoff of the compensation cap by bypassing it with a resistor, for example, you'd need to tack on another high-pass stage to protect the driver.
__________________
I write for www.enjoythemusic.com in the DIY section. You may find yourself getting a preview of a project in-progress. Be warned!
  Reply With Quote
Old 16th August 2014, 05:19 PM   #7008
gedlee is online now gedlee  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Novi, Michigan
Quote:
Originally Posted by badman View Post
The behavior of the CD/Waveguide/Horn combo will really define what you have to do ...
That's really the point, there is no hard and fast rules - too many variables.
  Reply With Quote
Old 25th August 2014, 03:40 PM   #7009
Paul W is offline Paul W  United States
diyAudio Member
 
Paul W's Avatar
 
Join Date: Oct 2003
Location: North Georgia
Hi Earl,

I believe you've stated that the wavefront produced by most compression drivers is not flat.

What are the typical wavefront shapes produced by good quality CDs with circumferential phase plugs?

Thanks,
__________________
Paul
  Reply With Quote
Old 25th August 2014, 04:35 PM   #7010
gedlee is online now gedlee  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Novi, Michigan
I don't have much data on this, but the few measurements that have been made show that the wavefront is not flat. Flat, of course, is a relative thing - relative to the wavelengths. So this is really only an issue at the higher frequencies where the HOMs start to appear. And even then we are talking about relatively small variance from flat, maybe 10-20% at most. Flat is the intent and it is mostly achieved, but there are errors in typical devices.
  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



New To Site? Need Help?

All times are GMT. The time now is 02:25 PM.


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