hybrid ported with rectangular conical horn |
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Teunos
Old Croc Joined: 23 November 2008 Location: The Netherlands Status: Offline Points: 1799 |
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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). |
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Best regards,
Teun. |
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bob4
Old Croc Joined: 29 February 2004 Location: Finland/Germany Status: Offline Points: 1842 |
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Hi Teunos, thank you for your answer & link! Part I would be nice too best regards, Bob |
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Elliot Thompson
Old Croc Joined: 02 April 2004 Location: United States Status: Offline Points: 5172 |
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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, |
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Elliot Thompson
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bob4
Old Croc Joined: 29 February 2004 Location: Finland/Germany Status: Offline Points: 1842 |
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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
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bee
Old Croc Joined: 14 June 2011 Location: Middlesex Status: Offline Points: 4553 |
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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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https://www.elements-audio.com
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concept-10
Young Croc Joined: 17 May 2016 Status: Offline Points: 1292 |
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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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gen0me
Young Croc Joined: 20 February 2016 Location: UK Status: Offline Points: 999 |
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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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snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3118 |
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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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bass*en*mass
Old Croc Joined: 03 September 2009 Location: "unknown" Status: Offline Points: 4009 |
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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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Elliot Thompson
Old Croc Joined: 02 April 2004 Location: United States Status: Offline Points: 5172 |
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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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Elliot Thompson
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Elliot Thompson
Old Croc Joined: 02 April 2004 Location: United States Status: Offline Points: 5172 |
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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, |
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Elliot Thompson
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mini-mad
Old Croc Joined: 13 July 2012 Location: london Status: Offline Points: 6903 |
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Or to but it nicely.... something else to break!!! |
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If it sounds like a gorilla is trying to escape, turn it down.
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