RT-2 Horn sub, the result - Page 11 - diyAudio
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Old 17th January 2009, 10:40 PM   #101
AKN is offline AKN  Sweden
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The sim from here does not include the external part of the RT-2 horn, one should add approx ~60cm (estimated) additional horn path radiating into Pi space.

The back camber is (as seen in the link obove) is actually divided into two chambers with a 192cm2 19mm long duct connecting them.
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Old 18th January 2009, 12:04 AM   #102
tinitus is offline tinitus  Europe
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Looking at the picture from start of thread...I think I would mount a baffle/devider at the end of the hornpath, so that the two hornpaths doesnt meet untill they leave the box
Further I am certain that some things could be done to the box on the OUTSIDE, making the outside prolonging more effective and achieve better coupling to outside surroundings
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Old 18th January 2009, 01:52 AM   #103
Ivo is offline Ivo  Netherlands
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Quote:
Originally posted by GM


Greets!

Yes, it yielded the most, best overall gain BW based on this layout: http://www.kensonpro.com/linnaraudio...simulering.htm

GM

Ah, I see. As I stated, I disagree with that model. I believe there's at least 2.25 meters in that horn, and possibly a good deal more.

I really should type the entire article through Google translate again (and save it, this time...) and read the full text again. As far as I know, it doesn't mention the aimed for flare rate, or intended pathlength/mouthsize.

This horn comes from a time when standard exponential and quarter wavelength was the norm (I think), so by determing some parameters, we can hopefully extrapolate the rest. Throatsize is around 400 cm^2, I guesstimate length at 2.25-2.75m and mouthsize as is around 3700 cm^2. The article suggests doubling of mouthsize through floorfiring (BDEAP similarity), which would suggest 7400 cm^2. With that throat, 2.6m length and a 7400 cm^2 mouth, that's roughly a 30 Hz horn. In Hornresp, it sims to 40 Hz with a variety of drivers.

Now, being perfectly realistic, it could also be a 2.25m horn with a 3700 cm^2 mouth (sims to 45 Hz). Those are more or less the extremes of my assessment. Not too shabby for a visually small cabinet.

So far, my Eminence Kappa 12 doesn't sim badly in "my" Rt2.
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Old 18th January 2009, 01:53 AM   #104
Ivo is offline Ivo  Netherlands
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Quote:
Originally posted by 4fun
The sim from here does not include the external part of the RT-2 horn, one should add approx ~60cm (estimated) additional horn path radiating into Pi space.

The back camber is (as seen in the link obove) is actually divided into two chambers with a 192cm2 19mm long duct connecting them.

Are you suggesting some sort of rexlex port between the two volumes? Interesting.
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Old 18th January 2009, 09:42 AM   #105
AKN is offline AKN  Sweden
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Quote:
Originally posted by Ivo



Are you suggesting some sort of rexlex port between the two volumes? Interesting.

Hi Ivo,

Well, something should happen as the area in the "port" is about half driver SD. Maybe the effect of this port (intentional or not) is out of the horns pass band, I don't know.
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Old 18th January 2009, 01:33 PM   #106
Elbert is offline Elbert  Norway
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Regrettably, the original magazine articles do not say anything about the exponential or moth area calculations and compromises, i.e. the theoretical deductions behind the horn is not quantified in any way..

The only thing to go by is that the horn was designed to cover the 30- to 300Hz range, and Fo is at one place referred to as being 30Hz.

Regarding the connection between the main closed volume and the triangular "foot", I've been wondering about this my self.

I've been thinking that perhaps this would act as some sort of Helhmoltz resonator or something, but i can only speculate. There is certainly no specific reference to this in the article..

Who Knows, perhaps I'll do a translation from Swedish to English of these articles if I have some spare time on my hands one day?
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Old 18th January 2009, 07:40 PM   #107
AKN is offline AKN  Sweden
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Hi

About the duct/port,
The RT-2 horn has the same inner height (300mm) as the old horn, RT-1 which had 10" driver. For a 12" to fit RT-2 the designer let the baffle go through to meet the outside of the bottom, by doing this they gained another 19mm in excess of 300mm, just about enough for 12" drivers to fit.
To cover the necessary rectangular cutout one small piece of hatch would be needed.

Allow me to speculate,
Later on during the RT-2 design the author discovered that a foot in form of triangle could be fitted in the bottom instead of the hatch. A triangular shaped section would have dual purposes, a more optimal last horn section and an additional rear chamber.

Now, the narrow slot will form as a port at some frequency. At low frequency the two chambers will be seen as one higher up we will come to resonance, higher up the second box will be disconnected. At a quick guess, the transaction frequency would be about 140Hz.
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Old 18th January 2009, 11:12 PM   #108
chops is offline chops  United States
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Quote:
Originally posted by jbell
If you are listening to music, you don't need below 40hz, period. Even for listening to HT... below 40hz is only effects, and the harmonics carry the day.

To this day, I will never understand why people insist on stating this. Unless you are using seriously inferior equipment with seriously limited BW, that above statement is far from the truth and you have absolutely no clue what you're missing out on.

I have plenty, PLENTY, PLENTY of recordings with more than enough sub-40Hz information in them. Not just pipe organ recordings and movies either. I'm talking about just about any kind of music imaginable. Jazz, blues, rock, heavy metal, classical, orchestral, easy listening (elevator music), pop, indie rock, Yanni.... I can go on and on and on. Just about all of them will have some form of sub-40Hz information on them.

On any given type of music, I would have to say there' s about a 70:30 ratio of sub-40Hz information in it. The 30% being sub-40Hz.

I challenge anybody to take whatever music CD they want, demo it on a system that only plays flat to 40Hz, then play that same CD on a system that plays flat to 20Hz or lower, then sit there and tell me "If you are listening to music, you don't need below 40hz, period". I always have and always will call this out as total BS.


Sorry for the rant. Just wanted to make my point.
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Old 19th January 2009, 01:00 AM   #109
jbell is offline jbell  United States
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You are welcome to your rant.. no worries there. However, I'd like to know the math behind your rant, and what notes you are missing?

Yes, I'm a geek, AND a musician. (one of my degree's is in music) I've played BBb clarinet, and contra-bassoon, so I know something about low frequency instruments. (Low-A bari-sax is still my favorite.... bassie rocks!!!)

What specific note are you referring to below 40hz? The 27.5 low A on a piano that is the lowest identifiable tone, or the lower overstrung bosendorfer strings?

A couple things to consider. ANY string, produces roughly 10db more volume at the first harmonic, than it does at it's fundamental. So a 40hz open E, is producing 10db more 80hz, than 40hz. Couple that with the equal loudness curves http://en.wikipedia.org/wiki/Equal-loudness_contour and you find out that what you are hearing, is not really 40hz after all, and when it gets to 20hz... it's even more exaggerated. A 60-80db concert setting needs 100-110db 20hz to be heard 'equal loudness' of the very moderate 60-80spl notes that are higher in pitch.

Here's some good reading on pitch, and low frequencies. And keep in mind, these were for pitches that were of 'equal loudness' and you see peoples ability to discern 27.5 hz at next to nothing, even with the severe boost in spl.

http://www.psych.ryerson.ca/russo/Fr...so_Galembo.pdf

I'm very accurate on my music, and my music reproduction systems. Those systems should reproduce the ORIGINAL music, not create things that weren't there before. In that intent, below 40hz is not necessary, as the 'notes' are just not there in 95% of music...

Now, if you are a pipe organ music person... I take it all back. 16hz rules... It's not a note, but it WILL take your breath away.
http://en.wikipedia.org/wiki/Symphon...nt-Sa%C3%ABns)
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Old 19th January 2009, 01:09 AM   #110
tinitus is offline tinitus  Europe
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chops, I thought you had gone fullrange, and didnt care much about that down low any more

jbell, as I understand it, whats below say the 40hz you relate to, its mostly related to "room-information", which does enhance ambience and soundstage...if sub is working properly, and im not thinking about those "house-wrecker" subs
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