Exponential Ports!!!! - diyAudio
Go Back   Home > Forums > Loudspeakers > Subwoofers

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 December 2005, 05:09 PM   #1
venki is offline venki  India
diyAudio Member
 
Join Date: May 2005
Location: india
Lightbulb Exponential Ports!!!!

Hi all,

i dont know if this topic has already been discussed in this forum . i was thinking .... if the port of a bandpass (or any ported) box be such that the length is decided by the helmontz resonator eqn, and the area expoentially increases from throat to mouth (just like horns)(something like the "wicked one" in Decaware ), will the efficiency increase? Will this really work ? I read somewhere that the area in the helmontz equation is the minimum area of the port. Any thoughts on this?

Venki

Ps:Sorry for my grammar
  Reply With Quote
Old 3rd December 2005, 05:44 PM   #2
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Hi Venki,

simple answer is no it won't work.
The "horn" is far too short to work at bass frequencies.

/sreten.
  Reply With Quote
Old 3rd December 2005, 05:51 PM   #3
diyAudio Member
 
Join Date: Jan 2005
Location: Rotterdam, NL
It's a fairly common concept. Of course it doesn't need to be exponential, other hornflares are possoble as well.

The Band Pass Horn ussually is a hybride of a 4th order BP and a hornshaped port. In concept any order BP is possible. But most BPH are 4th order, basically just horns that are to short to fully function as an horn. For example the HD15 from speakerplans:

http://www.speakerplans.com/index.php?id=hd15horn

An other concept is the hybride of a basreflex and a horn:

http://www.iven.nl/fotoarchief/fotoa...ap%20sm18b.jpg

Quote:
I read somewhere that the area in the helmontz equation is the minimum area of the port. Any thoughts on this?
A basreflex is based on a mass-spring principle, where the Helmholzresonator is the mass and the air inside the box works as an spring. So the area is just a part of the equation to form the mass and therefore in this case you can not aspect the smallest area to be the actual area of the port since the difference is quite large.

Eiter by looking at the basreflex or BP aspects you can predict the response, because they can act as both do. For instance lowering f3 by stacking multiples. The concept does however focus on 50 -60 Hz and up most of times to be effective.

Wkr Johan
  Reply With Quote
Old 3rd December 2005, 06:14 PM   #4
venki is offline venki  India
diyAudio Member
 
Join Date: May 2005
Location: india
sreten and Rademakers Thanx for the Quick replys..

Hey Rademakers, you mean this should work ..neways are there any advantages of using the configuration over the conventional bass reflex boxes ? Are there any rules (eqns for eg) for designing such boxes?

Thanks in Advance,
Venki.
  Reply With Quote
Old 3rd December 2005, 06:29 PM   #5
Relax is offline Relax  United States
diyAudio Member
 
Join Date: Jun 2005
Location: Dayton
So, Rade, could you describe a little more in depth how the Wicked one by decware should/does work?

Wherever I ahev asked this question I have usually gottent the whole "the horn isn't long enough to produce bass" yet I have builat several and all blow my mind.
  Reply With Quote
Old 3rd December 2005, 07:51 PM   #6
diyAudio Member
 
Join Date: Jan 2005
Location: Rotterdam, NL
Depends on the design parameters. The horn length needs to be close to 1/4 wavelength of the frequency it's going to support. The low cut off can be pushed down by using a larger rear chamber and/or front chamber at the cost of powerhandling. By putting it in 1/4 th or 1/8 th space the f3 is lowered.

Benefit would be the high efficiency compared to basreflex. Downside is that it doesn't go really low, 4th order BPH make excellent kickbins.

There are some 4th order BPH mainly used in PA that can go pretty low, they're also pretty big as well. The low end extension in those cases mostly depends on the principle of the 4th order BP which has increased efficiency in trade of bandwidth.

"The Wicked One" would behave in a similar way. The length of the horn is long enough to support hornloading down to an estimated 70 Hz (upper bass frequencies). The horn mouth however is way to small to support full hornloaded efficiency down to 70 Hz (each driver takes half).
Anything under that frequency is mostly going on the 4th order BP principle.

@Relax: "It's not a horn". So what, you're still impressed

The sound of a 4th order BP can be very impressive. Same goes for TL, basreflex, 6th order BP, etc etc..
It doesn't have to be hornloaded to be impressive.

@Venki:

4th order BPH's can be simulated with Hornresp (see diy Wiki), same goes for the basreflex-horn-hybrid (that last one should be seen as an short back loaded horn (aka rear loaded).

Wkr Johan
  Reply With Quote
Old 4th December 2005, 12:12 PM   #7
venki is offline venki  India
diyAudio Member
 
Join Date: May 2005
Location: india
Thanks for the info
Rademakers,

Hey by the way will i be able to simulate the 4th order BP box with exponential ports using the Hornresp program???

I read somewhere (in some website) that we can make a horn shorter for the same frequency by:-

finding the mouth area of the horn and dividing it by 5(rule of thumb i think) and reducing the length of the horn to flare till this area.

If this works (i have not tried),this should work more or less like the flared reflex box. am I correct. Any thoughts on this?

The above method would compromise for the efficiency.

Venki.
  Reply With Quote
Old 4th December 2005, 01:32 PM   #8
Coolin is offline Coolin  Netherlands
diyAudio Member
 
Coolin's Avatar
 
Join Date: Apr 2003
Location: Holland
Quote:
Originally posted by venki
Thanks for the info
Rademakers,

Hey by the way will i be able to simulate the 4th order BP box with exponential ports using the Hornresp program???

I read somewhere (in some website) that we can make a horn shorter for the same frequency by:-

finding the mouth area of the horn and dividing it by 5(rule of thumb i think) and reducing the length of the horn to flare till this area.

If this works (i have not tried),this should work more or less like the flared reflex box. am I correct. Any thoughts on this?

The above method would compromise for the efficiency.

Venki.
Nope, hornresp wont simulate this.

"finding the mouth area of the horn and dividing it by 5(rule of thumb i think) and reducing the length of the horn to flare till this area."
This sound more like (if you can) get the mouth placed in a corner you can do this because the walls will extend the rest of the horn.
You would still have the effeciency though.
  Reply With Quote
Old 4th December 2005, 01:42 PM   #9
venki is offline venki  India
diyAudio Member
 
Join Date: May 2005
Location: india
Hi Coolin,

I dont think the 1/5 rule is restricted to coner horns...but not sure...
let me try and find the link...

Thanx,
Venki.
  Reply With Quote
Old 4th December 2005, 03:41 PM   #10
diyAudio Member
 
Join Date: Jan 2005
Location: Rotterdam, NL
Quote:
Hey by the way will i be able to simulate the 4th order BP box with exponential ports using the Hornresp program???
Yes, you can, but:

Look at it as a (4th order) BPH rather then a 4th order BP with exponential ports. So it's now designed like a horn, meaning you're not going to choose chamber volumes and tune it to a specific frequency.

The design characteristics would be a large rearchamber, a large frontchamber and a short horn (instead of port). The horn doesn't need to be exponential tho. Other horn flares like conical, hyperbolic, catenoidal and about anything in between is possible. Exponential is a good start.

Wkr Johan
  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
BIG exponential sub tuned to 22Hz madam Subwoofers 11 4th January 2009 05:29 PM
biradial or exponential holger honda Multi-Way 0 15th June 2005 04:25 PM
My exponential Horn Piper Subwoofers 19 9th March 2005 06:16 PM
Exponential potentiometer argo Everything Else 9 28th November 2002 10:41 PM
curved ports vs. multiple ports Craig Multi-Way 1 22nd September 2002 08:30 AM


New To Site? Need Help?

All times are GMT. The time now is 09:47 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