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

2-way Chuffing
2-way Chuffing
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 14th April 2019, 06:41 PM   #1
Trev98 is offline Trev98
diyAudio Member
 
Join Date: Jan 2019
Default 2-way Chuffing

should i be worried about chuffing when design my 15" 2-way pa speakers ?I've seen a lot of 2-way enclosure designs both DIY and "Pro Grade (JBL,EV,Mackie) with a minimum of 2-4 ports around 3" in diameter rated at 600w rms all the way to 1200w.so is chuffing really an issue i should be worried about?
  Reply With Quote
Old 14th April 2019, 08:17 PM   #2
scholl is offline scholl  United States
diyAudio Member
 
Join Date: Dec 2012
IT can be a problem so some software gives a minimal port diameter. The only speaker I've heard chuffing was the Pioneer HPM 100, an over rated design.
  Reply With Quote
Old 14th April 2019, 10:51 PM   #3
ICG is offline ICG  Germany
diyAudio Member
 
ICG's Avatar
 
Join Date: Jul 2007
Location: I had a Déjà Moo - I've seen that BS before!
Chuffing happens mostly when the port dimensions are too small which causes the air velocity to be too high. You can simulate the air speed with WinISD, the result of the air speed is quite accurate.

Big ports got disadvantages too though, they take up (a lot in some cases) of the volume because the air in them doesn't add up to the effective enclosure volume. And in a 2-way speaker, the backside dispersed mid-garbage of the driver does come out too.
__________________
I had a Déjà Moo - I've seen that BS before!
  Reply With Quote
Old 14th April 2019, 11:10 PM   #4
Trev98 is offline Trev98
diyAudio Member
 
Join Date: Jan 2019
o is that a yes i should take chuffing into consideration when making my 2-way system?
  Reply With Quote
Old 14th April 2019, 11:11 PM   #5
ICG is offline ICG  Germany
diyAudio Member
 
ICG's Avatar
 
Join Date: Jul 2007
Location: I had a Déjà Moo - I've seen that BS before!
Yes.
__________________
I had a Déjà Moo - I've seen that BS before!
  Reply With Quote
Old 14th April 2019, 11:12 PM   #6
freddi is offline freddi  United States
diyAudio Member
 
freddi's Avatar
 
Join Date: Aug 2005
2-way Chuffing
fwiw I've heard chuffing and seen what I call "vent rectification" with a 15" JBL woofer in a 3.7 cubic foot box tuned with two 4" ID x "4 PVC pipe vents at 20vrms / 37Hz sine. The woofer's position moved forwards from normal center. My Karlson with similar area vent and system tuning did not chiuff, nor woofer move out of normal position (plus excursion was half that of the reflex) Ports for high output reflex probably should have flared ends.
  Reply With Quote
Old 14th April 2019, 11:16 PM   #7
ICG is offline ICG  Germany
diyAudio Member
 
ICG's Avatar
 
Join Date: Jul 2007
Location: I had a Déjà Moo - I've seen that BS before!
The woofer position does not change any chuffing.
__________________
I had a Déjà Moo - I've seen that BS before!
  Reply With Quote
Old 15th April 2019, 01:22 AM   #8
freddi is offline freddi  United States
diyAudio Member
 
freddi's Avatar
 
Join Date: Aug 2005
2-way Chuffing
it was my ports causing the offset -

http://mariobon.com/Articoli_storici...flex_Ports.pdf


” Could ports c and d have hidden asymmetry?
All the ports were surface mounted in the enclosure. This
means that one end of the port has a baffle and the other
end does not. Thus all the ports were asymmetric. This
suggests a preferential airflow in one direction over
another, analogous to a fluid flow diode effect, and it can
be thought of as “port rectification.”
  Reply With Quote
Old 15th April 2019, 02:07 AM   #9
ICG is offline ICG  Germany
diyAudio Member
 
ICG's Avatar
 
Join Date: Jul 2007
Location: I had a Déjà Moo - I've seen that BS before!
Oh sorry, I misunderstood it.

If the offset of the membrane moves with rising excursion and no DC is in the amp signal, it is partly a possible asymmetry in the driver suspension and/or partly the effect of the port. If the driver closes in to the power compression, it gets worse as the Qt rises with the VC temperature. Klippel released several papers on that topic.

For the port: A too high air velocity in the port greatly increases the asymmetries. The port surface should aim for SD/3 as a rule of thumb. A typical 15" driver got ~855cm² cone surface, so 285cm² should be the target. Your ports got a surface of 157cm², that's a bit above the half of the suggested surface. So a larger port (or more than the two) would likely solve the problem. You can simulate the port air velocity with WinISD and other tools to get a correct dimension of the port as the effect of the asymmetries is way weaker then.
__________________
I had a Déjà Moo - I've seen that BS before!
  Reply With Quote
Old 15th April 2019, 07:34 AM   #10
chris661 is offline chris661  United Kingdom
diyAudio Member
 
chris661's Avatar
 
Join Date: Feb 2008
Location: Sheffield
Quote:
Originally Posted by Trev98 View Post
should i be worried about chuffing when design my 15" 2-way pa speakers ?I've seen a lot of 2-way enclosure designs both DIY and "Pro Grade (JBL,EV,Mackie) with a minimum of 2-4 ports around 3" in diameter rated at 600w rms all the way to 1200w.so is chuffing really an issue i should be worried about?
I'd say it depends.

To give you an idea, most 2-way speakers aren't expected to put out much bass - it would be a surprise to use them to re-inforce a mic'd kick drum without any subwoofers.

You could run an acoustic act through the speakers, all the way up to the limiters, and never have a problem with port chuffing.
You could switch to dubstep and immediately have a lot of problems.

The thing to remember is this: when you're doing simulations of port velocities etc, the software is telling you what happens when you put in a sine tone at that input voltage. If it's 90v RMS into an 8ohm load, that's approximately a kilowatt.

It's up to you to decide if 40Hz at 90v RMS is a likely input signal for the driver.
If it'll happen often, you'll need a big port. No way around that.
If it'll happen because some crazy person wants to play dubstep without any subwoofers, that's the perfect time for the salesman to connect a subwoofer and show the difference.

So, most companies probably under-size their ports on the assumption that if the customer wants bass, they'll simply add subwoofers.


If you're designing a 15" 2-way to run without any subwoofers and play bass-heavy content, you'll need to put in a bigger port than most. Again, it's up to you to look at the likely program material, and figure out how much of a problem you'll have.

IIRC, going above 17m/s will start to incur friction losses in most ports.
I have a pair of Faital Pro 10FH520 drivers in each of my main speakers, and have found that when they have a single 3" port you get a low tuning (44Hz-ish) that will give audible chuffing problems at high power.
I rarely run with that setting, though - only for small venues where I want the low-frequency extension. For larger venues, I can unblock some more ports and get louder, but missing the LF extension. That's when the subs come out.

Chris
__________________
My work: www.grimshawaudio.com
  Reply With Quote

Reply


2-way ChuffingHide 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

Similar Threads
Thread Thread Starter Forum Replies Last Post
Compact Subwoofer Port Chuffing grahamgraham Subwoofers 10 23rd November 2016 11:05 AM
Subwoofer port chuffing noise georgehifi Subwoofers 6 10th June 2016 06:52 PM
Software simulation that includes port chuffing? chris661 Subwoofers 13 8th April 2014 05:21 AM
prevent the chuffing? phase plug?? rick57 Multi-Way 14 23rd December 2004 03:12 AM


New To Site? Need Help?

All times are GMT. The time now is 02:41 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