1st order tweeters - 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 3rd June 2012, 03:37 PM   #1
Banned
 
Join Date: May 2012
Default 1st order tweeters

hi,

Often its said that 1st order crossovers do not provide sufficient protection especially for the tweeter. I have read that signals down to 100hz get through at almost full power. That sounds pretty tough for a tweeter to cope with. How do you make a design like that work? I have seen that B&W used 1st order slopes on a number of their models, how do their metal dome nautilus tweeters cope with all that energy?
  Reply With Quote
Old 4th June 2012, 04:07 AM   #2
Tino is offline Tino  Canada
diyAudio Member
 
Join Date: Jan 2004
Location: Toronto
I assume they cross it over fairly high.

Quote:
Originally Posted by theaudiophile View Post
hi,

Often its said that 1st order crossovers do not provide sufficient protection especially for the tweeter. I have read that signals down to 100hz get through at almost full power. That sounds pretty tough for a tweeter to cope with. How do you make a design like that work? I have seen that B&W used 1st order slopes on a number of their models, how do their metal dome nautilus tweeters cope with all that energy?
  Reply With Quote
Old 4th June 2012, 04:35 AM   #3
diyAudio Member
 
norman bates's Avatar
 
Join Date: Nov 2003
Location: iowa
well, usually the tweeter impedance shoots really high at its resonance, the resistance is so high there that instead of the tweeter rolling off 6db at say 3khz, it goes fairly flat down to say 1.5khz. Then you get carried away with the volume, then oops, why is the tweeter goings schhh, schhhhh on voices ?

And yes, A lot of power gets through a 6db filter. A driver moves 4 times farther as you drop an octave, even a tweeter. And you tend to get more and more power the lower you go in music on the freq spectrum. I think a 6db filter barely counteracts this.

You can build a rugged tweeter with a low resonance. I think rule of thumb is to cross 2-3 octaves above its resonance (for a 6db).

I've been wanting to play with 6db tweets (then you can get time aligned) but havn't yet.

Norman
  Reply With Quote
Old 4th June 2012, 06:09 AM   #4
VaNarn is offline VaNarn  Australia
diyAudio Member
 
Join Date: Dec 2010
Location: Ivanhoe
The correct xover choice is determined by the tweeter you wish to use , exactly where you wish to implement the freq. of the xover and power distribution considerations. Ferrofluid and improved construction methods have eased the constraints imposed by first order networks and it useful to consider the quasi second order as a preferred type.
  Reply With Quote
Old 21st June 2012, 11:03 PM   #5
Banned
 
Join Date: May 2012
If you look at the current B&W diamond 800 series it seems they use first order crossovers. Are these speakers time aligned? I dont usually think of B&W as a proponent of the phase coherent speaker system and they dont advertise it. Everybody says first order speakers are difficult to do and cause all sorts of problems yet it seems they have pulled it off. How have they managed to avoid all the problems people talk about like cone breakup, tweeter damage, as well as the fact that you need drive units which are fairly flat well beyond the crossover points?

What actually happens if the drivers are not wide bandwidth but roll off quickly? You would get an overall steeper slope however does it mean the phase is no longer phase coherent?
  Reply With Quote
Old 22nd June 2012, 01:33 AM   #6
tvrgeek is offline tvrgeek  United States
diyAudio Member
 
Join Date: Dec 2009
Location: Md
It all depends on the tweeter. Look at their specs. Take their advice. Personally, I would not use a "typical" 1" dome at first order below 4 or 5K. Distortion. Yes, you can take advantages of the natural roll-offs of the drivers. Smart designs often do, but the are NO help with protecting the driver from power. A tweeter with a second order LF roll off at 1K with a first order crossover may give the third order acoustic slope, but for power, it is still a first order crossover.

Don't second guess what big companies that design and build their own drivers may do in some specific speaker and think that is a general rule. You will fail. Been there, done that. Paid for my errors.
  Reply With Quote
Old 22nd June 2012, 01:54 AM   #7
diyAudio Member
 
Join Date: Nov 2006
Location: Adelaide, South Australia
Blog Entries: 19
The point about managing the resonance of the tweeter is critical. If you implement a trap to flatten out the impedance of the tweeter at resonance and also across over at a sensible frequency - greater than 3khz for most tweeters, then a first order crossover is no great feat.

Getting the trap right is critical and is something most novices balk at.

The difference in energy a typical tweeter sees with and without a trap on a first order crossover is significant. Totally audible and I would expect it to impact the ruggedness of the driver under abuse. To be blunt the crossover just does not work properly with the variable impedance of an untreated tweeter.

If you don't want to implement the trap (and to be honest I think it is best used for any passive crossover!) then you would be best using a higher order crossover to minimise excitation of the tweeter at resonance.
  Reply With Quote
Old 22nd June 2012, 04:33 AM   #8
diyAudio Member
 
Join Date: Apr 2012
Location: Sydney
Quote:
Originally Posted by tvrgeek View Post
A tweeter with a second order LF roll off at 1K with a first order crossover may give the third order acoustic slope, but for power, it is still a first order crossover.
I thought the acoustic slope was what counted? Third order acoustic is third order crossover regardless of the components used to get there, no?
  Reply With Quote
Old 22nd June 2012, 07:45 AM   #9
diyAudio Member
 
Join Date: Sep 2010
Quote:
If you look at the current B&W diamond 800 series it seems they use first order crossovers. Are these speakers time aligned? I dont usually think of B&W as a proponent of the phase coherent speaker system and they dont advertise it. Everybody says first order speakers are difficult to do and cause all sorts of problems yet it seems they have pulled it off. How have they managed to avoid all the problems people talk about like cone breakup, tweeter damage, as well as the fact that you need drive units which are fairly flat well beyond the crossover points?
B&W uses pseudo-LR2 slopes. Tweeter damage is avoided since it's an LR2 at 4khz, which means it's already ~30+db down at resonance and I would imagine even more down than that in actuality. (it may be an LR2 in the crossover region, but probably shifts to 4th order out of band)

As for avoiding cone breakup, they don't. Their woofer plays right through it with a crossover around 4.2khz and a cone breakup at 3.8khz.

As for flat... the end speakers aren't flat IN band, so why would they care about out-of-band behavior?

Quote:
Originally Posted by samadhi View Post
I thought the acoustic slope was what counted? Third order acoustic is third order crossover regardless of the components used to get there, no?
For excursion, acoustic slope matters. But limiting thermal buildup, electrical slope matters too. Also, even if the tweeter is inefficient at x frequency, there is still "attempted motion" being produced from the voice coil at those frequencies - it's just being stifled by the "enclosure" of the box.

Last edited by RockLeeEV; 22nd June 2012 at 07:53 AM.
  Reply With Quote
Old 23rd June 2012, 01:51 PM   #10
Einric is offline Einric  United States
diyAudio Member
 
Einric's Avatar
 
Join Date: Feb 2011
Location: Bozeman, MT
One of my favorite crossover points for the Dayton DC28F is 1st order at 4500-5000.
I have driven 50W into it from multiple amps without strain, it sounds quite good actually.
Here is an example....
Attached Images
File Type: png DA175-RS100-DC28F.png (115.6 KB, 323 views)
  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
Tweeters for 1st order crossover martinbls Multi-Way 12 20th August 2011 09:59 PM
1st order Passive Line Level Crossover + 2nd order Highpass? alexclaber Multi-Way 11 4th January 2008 07:15 PM
deceptive perception ? 1st order-2nd order question poldus Multi-Way 4 10th April 2007 11:58 PM
My 1st order butterworth filter better than 4th order L-R: Why? philipreji Solid State 61 1st March 2007 04:50 PM
1st order ? L-R 2nd order? or transient perfect?? Ken L Multi-Way 6 17th October 2003 04:22 PM


New To Site? Need Help?

All times are GMT. The time now is 10:01 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