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hybrid ported with rectangular conical horn

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Teunos View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Teunos Quote  Post ReplyReply Direct Link To This Post 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:

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''
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bob4 Quote  Post ReplyReply Direct Link To This Post 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:

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


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Elliot Thompson View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post 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:

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
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bob4 Quote  Post ReplyReply Direct Link To This Post Posted: 20 April 2017 at 10:23pm

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:// https://www.reddit.com/r/RELounge/comments/34axqh/download_academiaedu_files_without/
4. print paper -> save as pdf Big smile
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bee Quote  Post ReplyReply Direct Link To This Post 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...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote concept-10 Quote  Post ReplyReply Direct Link To This Post 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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post 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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post 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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bass*en*mass Quote  Post ReplyReply Direct Link To This Post 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)


Edited by bass*en*mass - 21 April 2017 at 8:30pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post 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,



Edited by Elliot Thompson - 21 April 2017 at 7:31pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post 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
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mini-mad Quote  Post ReplyReply Direct Link To This Post 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.
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