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hybrid ported with rectangular conical horn

Printed From: Speakerplans.com
Category: Plans
Forum Name: Ported Enclosures
Forum Description: Post all your reflex and bandpass and 'other' boxes with holes in stuff here...
URL: http://forum.speakerplans.com/forum_posts.asp?TID=98330
Printed Date: 28 June 2017 at 9:53am
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Topic: hybrid ported with rectangular conical horn
Posted By: jayam000
Subject: hybrid ported with rectangular conical horn
Date Posted: 18 April 2017 at 3:42am

Normally the port is recatangular, square or round. here it is like horn. Any advantage?
If yes, then how to calculate the same. 


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"I do not want to make my stomach a graveyard of dead animals." George Bernard Shaw



Replies:
Posted By: bass*en*mass
Date Posted: 18 April 2017 at 9:42am
don keele, if i remember correctly, wrote a good article about flared ports and their influences etc.. lots of info online aswell as its still up to date tech, see new Lacoustics 218 subs for example..


Posted By: bob4
Date Posted: 18 April 2017 at 12:20pm
Originally posted by bass*en*mass bass*en*mass wrote:

don keele, if i remember correctly, wrote a good article about flared ports and their influences etc.. 

except the port of this ported wbin is NOT flared at all, just increasing in cross-section. So none of that theory applies.    

some french guys have done research, with prototyping and measurements

http://bgavinsound.com/Reference/Music/AES/AES_116th.pdf" rel="nofollow - http://bgavinsound.com/Reference/Music/AES/AES_116th.pdf

http://https://fr.wikipedia.org/wiki/Tuyère_acoustique" rel="nofollow - http://https://fr.wikipedia.org/wiki/Tuyère_acoustique




Posted By: Elliot Thompson
Date Posted: 18 April 2017 at 3:39pm
The flared port just reduce port shuffle noise. A noble idea for home audio when High SPL is not a factor. However in sound reinforcement, you would have to have a really piss poor design to have the port noise as loud as the woofer playing at high sound pressure levels.

Best Regards,


-------------
Elliot Thompson


Posted By: jayam000
Date Posted: 19 April 2017 at 2:55am
Thanks for the nice information bob4 & Elliot Thompson.
Now if we want to impliment,  how to calculate?



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"I do not want to make my stomach a graveyard of dead animals." George Bernard Shaw


Posted By: bob4
Date Posted: 19 April 2017 at 5:44am
Originally posted by Elliot Thompson Elliot Thompson wrote:

The flared port just reduce port shuffle noise.


If you believe so, you should carefully read the aes paper that i linked      


Posted By: mobiele eenheid
Date Posted: 19 April 2017 at 6:12am
The easiest way is to simulate the port in Hornresp, as a single segment (S1, S2, L12) with the chamber volume (Vtc in cm^3) leaving the effect of the horn out. Then approximate the ports tuning by a straight port (Ap and Lp), so that you can simulate the horn as well, now using the segments for the horn.

I haven't read the AES paper yet but I'm pretty sure that, in this particular case, the effects aren't so immense, that it justifies you learning AkAbak to fully grasp it's influence on the whole.

Johan

- Edit -  Now that I've read the AES-paper, my advice remains unchanged ;)


Posted By: Elliot Thompson
Date Posted: 19 April 2017 at 11:19am
Originally posted by bob4 bob4 wrote:

Originally posted by Elliot Thompson Elliot Thompson wrote:

The flared port just reduce port shuffle noise.


If you believe so, you should carefully read the aes paper that i linked      

I am sorry I cannot take a paper seriously with tubes longer than the actual box it is residing in. It tells me automatically that the cabinet is so small that the tubes need to be longer than the actual enclosure in order to achieve low frequencies.

 

Ask yourself a question. How many times have you seen a Bass Reflex enclosure with ports sticking out of a box aimed for Sound Reinforcement?

 

This paper reaps Home Audio Setup as I mentioned in my previous post why such a method would be beneficial under low SPL conditions. Under High SPL Conditions in the Sound Reinforcement World which we all do, such methods are not going offer tremendous results for the majority of the sound stems from the loudspeaker, not the port. 

 

Not everything posted in AES is aimed for Sound Reinforcement.

 

 

Best Regards,



-------------
Elliot Thompson


Posted By: jayam000
Date Posted: 19 April 2017 at 1:20pm
Thanks to all for nice guidance.


-------------
"I do not want to make my stomach a graveyard of dead animals." George Bernard Shaw


Posted By: bob4
Date Posted: 19 April 2017 at 1:34pm
Originally posted by Elliot Thompson Elliot Thompson wrote:

I am sorry I cannot take a paper seriously with tubes longer than the actual box it is residing in. It tells me automatically that the cabinet is so small that the tubes need to be longer than the actual enclosure in order to achieve low frequencies.
 

it's a small prototype for research….


Originally posted by Elliot Thompson Elliot Thompson wrote:

Not everything posted in AES is aimed for Sound Reinforcement.

Agreed (well, duh… Tongue)

Originally posted by Elliot Thompson Elliot Thompson wrote:

Ask yourself a question. How many times have you seen a Bass Reflex enclosure with ports sticking out of a box aimed for Sound Reinforcement?
  

while I'm not claiming that it's useful for PA, if you had read the blurb, you would have noticed that the nozzle shape yields notable improvements/stability in phase behavior at high input power:

Originally posted by Pellerin, Pollack, Mokerken Pellerin, Pollack, Mokerken wrote:

 we proved, with the help of the phase space representations, that well tuned nozzles ensure a better global dynamical stability even for very high feeding power in the case of a dipole configu- ration and the dipole moment is then an interesting physical property which allows to build complex di- rectivity patterns in the low frequencies.

  

I mainly wanted to point out that the nozzle port is about more than just reducing port chuffing.


I don't know about you, but to me this statement in the article's conclusions is an interesting one:

Originally posted by Pellerin, Pollack, Mokerken Pellerin, Pollack, Mokerken wrote:

 We demonstrated first that it effectively exists a second cutoff frequency under the well known Helmholtz frequency which could be exploited to design sources radiating in the very low frequency domain with dipole directivity patterns and that, in theory, this frequency could be decreased near zero Hertz. 
  

I don't see why any of these principles couldn't be applied to PA systems at some point.

Best Regards,

Bob





Posted By: Elliot Thompson
Date Posted: 19 April 2017 at 3:15pm
Originally posted by bob4 bob4 wrote:

I don't see why any of these principles couldn't be applied to PA systems at some point.

Best Regards,

Bob





Because in the Sound Reinforcement Market we do not use a port larger than actual size of the enclosure in addition to the size of a loudspeaker in a reflex enclosure to attain greater SPL. The size of the cabinet makes a huge factor on the performance.

We will use a larger enclosure to extend the frequency response. We will use multiple drivers in order to increase the coupling effect to attain more SPL in which, will offer lower distortion than forcing one speaker to do all the work.  We will use woofers with the proper TS Parameters in order to attain optimum results.

Phase? I would recomend measuring the impedance plots of loudspeakers in free air offering various TS Parameters. Not even a sealed back driver will be in phase once it approaches its fs.


If you feel the author's idea is intriguing, build a Sound Reinforcement version of his Home Audio Bass Reflex concept, make the proper measurements and, post your findings.


Best Regards,



-------------
Elliot Thompson


Posted By: gen0me
Date Posted: 19 April 2017 at 7:25pm
Maybe the reason why port is so huge is because autor wanted to get flat response from strong speaker?
Haha is it still br or a miniscoop

Just a thought: could be good idea to design telescopic brs


Posted By: Teunos
Date Posted: 19 April 2017 at 7:55pm
Originally posted by Elliot Thompson Elliot Thompson wrote:

Originally posted by bob4 bob4 wrote:

I don't see why any of these principles couldn't be applied to PA systems at some point.

Best Regards,

Bob





Because in the Sound Reinforcement Market we do not use a port larger than actual size of the enclosure in addition to the size of a loudspeaker in a reflex enclosure to attain greater SPL. The size of the cabinet makes a huge factor on the performance.

We will use a larger enclosure to extend the frequency response. We will use multiple drivers in order to increase the coupling effect to attain more SPL in which, will offer lower distortion than forcing one speaker to do all the work.  We will use woofers with the proper TS Parameters in order to attain optimum results.

Phase? I would recomend measuring the impedance plots of loudspeakers in free air offering various TS Parameters. Not even a sealed back driver will be in phase once it approaches its fs.


If you feel the author's idea is intriguing, build a Sound Reinforcement version of his Home Audio Bass Reflex concept, make the proper measurements and, post your findings.


Best Regards,

A previous fellow of my university actually researched the flared ports in depth using Schlieren imaging.
His papers can be found in public domain (or at least part II) at:
http://www.academia.edu/19837501/Vortex_sound_in_bass-reflex_ports_of_loudspeakers._Part_II._A_method_to_estimate_the_point_of_separation" rel="nofollow - http://www.academia.edu/19837501/Vortex_sound_in_bass-reflex_ports_of_loudspeakers._Part_II._A_method_to_estimate_the_point_of_separation

If desired i am sure the author would not mind me sharing Part I as well (being a student at his Uni).



-------------
Best regards,
Teun.

,,Diamonds are forever''


Posted By: bob4
Date Posted: 20 April 2017 at 12:23pm
Originally posted by Teunos Teunos wrote:

A previous fellow of my university actually researched the flared ports in depth using Schlieren imaging.
His papers can be found in public domain (or at least part II) at:
http://www.academia.edu/19837501/Vortex_sound_in_bass-reflex_ports_of_loudspeakers._Part_II._A_method_to_estimate_the_point_of_separation" rel="nofollow - http://www.academia.edu/19837501/Vortex_sound_in_bass-reflex_ports_of_loudspeakers._Part_II._A_method_to_estimate_the_point_of_separation

If desired i am sure the author would not mind me sharing Part I as well (being a student at his Uni).


Hi Teunos, 

thank you for your answer & link! Part I would be nice too Big smile

best regards,

Bob




Posted By: Elliot Thompson
Date Posted: 20 April 2017 at 1:13pm


Originally posted by Teunos Teunos wrote:

 

A previous fellow of my university actually researched the flared ports in depth using Schlieren imaging.
His papers can be found in public domain (or at least part II) at:
http://www.academia.edu/19837501/Vortex_sound_in_bass-reflex_ports_of_loudspeakers._Part_II._A_method_to_estimate_the_point_of_separation" rel="nofollow - http://www.academia.edu/19837501/Vortex_sound_in_bass-reflex_ports_of_loudspeakers._Part_II._A_method_to_estimate_the_point_of_separation

If desired i am sure the author would not mind me sharing Part I as well (being a student at his Uni).


So the conclusion is basically such a method is more beneficial for small enclosures due to the limitation of the enclosure. The ratio between the sound being 0 dB of the amplified signal and distortion without using such a method is -20 dB which is inaudible compared to a room full of punters screaming their lungs out to their favourite song.

 

In order to hear an equal amount of distortion as the amplified frequency, the distortion would need to be residing on a 10,000 watt amplifier to match the output of a frequency residing on a 100 watt amplifier. That would be a 20 dB ratio.

 

All loudspeakers offer additional harmonics in which will be looked upon as distortion however, only a few are willing to post such graphs. Unfortunately, this is what many do not realise. The source material offers more distortion today than it did 20 years ago due to many recording engineers inserting distortion/saturation plug-ins and hardware equipment designed to deliver distortion in the mix to achieve that “Analogue Sound” on Digital Audio.

 

The idea seems like a useful method for the Home Audiophile-Classical Music type of crowd where they get very temperamental on any type of residue sound in their household.  

 

Best Regards,

 



-------------
Elliot Thompson


Posted By: bob4
Date Posted: 20 April 2017 at 10:23pm
Originally posted by Teunos Teunos wrote:

His papers can be found in public domain (or at least part II) at:
http://www.academia.edu/19837501/Vortex_sound_in_bass-reflex_ports_of_loudspeakers._Part_II._A_method_to_estimate_the_point_of_separation" rel="nofollow - http://www.academia.edu/19837501/Vortex_sound_in_bass-reflex_ports_of_loudspeakers._Part_II._A_method_to_estimate_the_point_of_separation

Thank you again for the link Teunos! But it links actually to part I. 

Little hint for anyone who wants to download/save the file to their own computer:

1. open the source code view
2. do a text search for "scribd"
3. follow these instructions :  http://%20https://www.reddit.com/r/RELounge/comments/34axqh/download_academiaedu_files_without/%20" rel="nofollow - http:// https://www.reddit.com/r/RELounge/comments/34axqh/download_academiaedu_files_without/
4. print paper -> save as pdf Big smile


Posted By: bee
Date Posted: 20 April 2017 at 10:36pm
Originally posted by Elliot Thompson Elliot Thompson wrote:

Originally posted by bob4 bob4 wrote:

I don't see why any of these principles couldn't be applied to PA systems at some point.

Best Regards,

Bob





Because in the Sound Reinforcement Market we do not use a port larger than actual size of the enclosure in addition to the size of a loudspeaker in a reflex enclosure to attain greater SPL. The size of the cabinet makes a huge factor on the performance.

We will use a larger enclosure to extend the frequency response. We will use multiple drivers in order to increase the coupling effect to attain more SPL in which, will offer lower distortion than forcing one speaker to do all the work.  We will use woofers with the proper TS Parameters in order to attain optimum results.

Phase? I would recomend measuring the impedance plots of loudspeakers in free air offering various TS Parameters. Not even a sealed back driver will be in phase once it approaches its fs.


If you feel the author's idea is intriguing, build a Sound Reinforcement version of his Home Audio Bass Reflex concept, make the proper measurements and, post your findings.


Best Regards,

 
Totally agree with you, but what if some one has a box, with a port twice the length of the box, designed for pa use... its defo possible, and the gains can be massive, not only keeping the box footprint small, and keeping the port in side the box... its 100% possible...


-------------
https://www.elements-audio.com


Posted By: concept-10
Date Posted: 21 April 2017 at 8:32am
Malcolm Hill was a big user of flared reflex ports in PA, i still have some flared port 10 inch boxes, sound very good.


Posted By: gen0me
Date Posted: 21 April 2017 at 12:54pm
Originally posted by bee bee wrote:


 
Totally agree with you, but what if some one has a box, with a port twice the length of the box, designed for pa use... its defo possible, and the gains can be massive, not only keeping the box footprint small, and keeping the port in side the box... its 100% possible...


And I dont agree. When you use small br with long port you should consider second br resonance. It means the high cutoff should be lower and it implies bigger tops. So its not as colorfull. In home audio full ranges go easily low enough.


Posted By: snowflake
Date Posted: 21 April 2017 at 3:02pm
straight ports suffer distortion at a much lower port velocity than flared ones. if you want to make ports short it is vital that you flare them so that you don't have to make their cross section and length huge. so these methods are especially useful for PA use.

"In order to hear an equal amount of distortion as the amplified frequency, the distortion would need to be residing on a 10,000 watt amplifier to match the output of a frequency residing on a 100 watt amplifier. That would be a 20 dB ratio."

No. above the distortion threshold the port noise increases more than linearly with input signal - so at high volumes the distortion can completely mask the signal.


Posted By: bass*en*mass
Date Posted: 21 April 2017 at 4:18pm
Have to aggree with snowflake, from personal experience, same cab, same driver, same power etc. - regular port chuffs quite noticable, flared port remains silent..  (flared outside only, inside just rounded over)


Posted By: Elliot Thompson
Date Posted: 21 April 2017 at 7:26pm
Originally posted by snowflake snowflake wrote:

straight ports suffer distortion at a much lower port velocity than flared ones. if you want to make ports short it is vital that you flare them so that you don't have to make their cross section and length huge. so these methods are especially useful for PA use.

"In order to hear an equal amount of distortion as the amplified frequency, the distortion would need to be residing on a 10,000 watt amplifier to match the output of a frequency residing on a 100 watt amplifier. That would be a 20 dB ratio."

No. above the distortion threshold the port noise increases more than linearly with input signal - so at high volumes the distortion can completely mask the signal.


The distortion you are mentioning that is so prominent comes from the loudspeaker not the port. The port responds like a band pass filter. The port is tuned to a frequency. The tuning frequency determines the length and the radius of the port based on enclosure size and of course, the TS Parameters of the loudspeaker at a given dB level.

 

Unless you are tuning the cabinet extremely high (So it will ring) in which, will require a very large radius for a port, the port is not large enough to deliver equal amount of SPL as the loudspeaker at high sound pressure levels. And if you are tuning the cabinet so high that requires such a large port radius you are better off making a bass horn.

 

A port does not need to be the focal point in a reflex box. So the most common method to reduce any audible shuffling noise is to put the ports in the rear of the box.

It is very old method that has been around since the1950s.

 

I am going to expand on very large ports in small boxes that a lot of home audio guys pay no attention to for a moment. Large ports in small cabinets reduce in the internal chamber in the eyes of the loudspeaker. That of course, alters the low frequency extension. It is the next biggest culprit compared to bracing a small box to the point you lose 50% (I’ve seen some designs with higher percentages) of the internal chamber due to excessive wood bracing posing their presence inside the cabinet.

Many of you may not know Rog purposely made the G-Sub’s dimensions larger to compensate the bracing in the box to avoid losing the low frequency extension.

Best Regards,



-------------
Elliot Thompson


Posted By: Elliot Thompson
Date Posted: 21 April 2017 at 7:29pm
Originally posted by bee bee wrote:

 
Totally agree with you, but what if some one has a box, with a port twice the length of the box, designed for pa use... its defo possible, and the gains can be massive, not only keeping the box footprint small, and keeping the port in side the box... its 100% possible...


 

Anything is possible. However having ports protrude in such a manner for sound reinforcement will more than likely look like a place to kotch  your foot from a punters perspective or stand on top of for whatever reasons. They will also look like a nice handle to move the box about.  

Best Regards,


-------------
Elliot Thompson


Posted By: mini-mad
Date Posted: 21 April 2017 at 9:29pm
Originally posted by Elliot Thompson Elliot Thompson wrote:

Originally posted by bee bee wrote:

 
Totally agree with you, but what if some one has a box, with a port twice the length of the box, designed for pa use... its defo possible, and the gains can be massive, not only keeping the box footprint small, and keeping the port in side the box... its 100% possible...


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<p ="Msonormal">Anything is possible. However having ports protrude in such
a manner for sound reinforcement will more than likely look like a place to
kotch <span style="mso-spacerun:yes"> </span>your foot from a punters
perspective or stand on top of for whatever reasons. They will also look like a
nice handle to move the box about. <span style="mso-spacerun:yes"> </span>



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Or to but it nicely.... something else to break!!!

-------------
If it sounds like a gorilla is trying to escape, turn it down.


Posted By: jayam000
Date Posted: 09 May 2017 at 1:07pm
Hi Friends,
David the master himself has suggested to simulate as compound horn.
Hence i have designed one.
Now Atc & Vtc is confusing one.
Now help me to do Hornresp input.
I have not added the Sd & speaker cutout volume in the front side.
This is marked by red line. 


-------------
"I do not want to make my stomach a graveyard of dead animals." George Bernard Shaw



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