Understanding the Replikon horn - diyAudio
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Old 19th April 2005, 06:03 PM   #1
Tyimo is offline Tyimo  Hungary
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Default Understanding the Replikon horn

Hi!

I open this new thread about the Replicon BLH speaker from Klangform Akustik, because I would like to understand theirs special BLH calculation method.

The Replikon is unique by having a BIG pressure chamber behind the driver and a relative short horn length.
I haven't got much infos about this speaker:

-The website of the makers of the Replikon horn:
http://www.klangform-akustik.de/

-"...Die Replikon verkörpert hingegen die nächste Generation von Backloaded Hörnern. Als echtes Fullrange Horn konzipiert, weist es einen -3db Punkt von 35 Hz auf. Möglich wird dies durch die neue Form der Hornberechnung, die für die berechnete Grenzfrequenz erforderliche Öffnungsfläche aufweist. Durch die relativ große Druckkammer verstärkt das Horn nur die Frequenzbereiche die unterhalb der Einbauresonanz des Treibers liegen und interferiert somit nicht mit dem direkt abgestrahlten Schall. Um wirklich sicherzugehen, dass keine Mitteltonanteile aus dem Horn treten weist der Hornhals der Replikon ein neuartiges passives akustisches Filter auf. Durch diese ausgeklügelte Geometrie des Hornhalses entweicht kein Mitteltonschall mehr in den Hornhals. Eine saubere und klare Wiedergabe ist die Folge. Der Einsatz von tiefbassvernichtenden Dämmmaterialien wird somit unnötig. Völlig sauber ohne Resonanzen werden Tiefbassanteile der Musik verzerrungsfrei und sehr druckvoll wiedergegeben...."

- There is a dialog on the
http://www.audiomap.de/forum/index.p..._id/19186/page
where Till Roemhild, one of the developers of the Replikon, suggests a same type horn for the Fostex FP 253:

"...Am besten hat der FP253 in unserem Raum in knapp 130 ltr geklungen. Somit hat der Treiber eine Einbaufrequenz bei ca. 55Hz die noch durch die Öffnungsfläche und die Länge des Horns nach unten erweitert wird. Die Abstimmfrequenz der Öffnungsfläche haben wir auf 35Hz gelegt und die Länge liegt um knapp 45Hz. Die Öffnungsfläche liegt somit bei knapp 4500 cm² und die Länge würde bei knapp 1,2 m liegen. Die ersten Simulationen zeigten anhand der nach links verzerrten Impedanzkurve und den zerrissenen Frequenzgang eine zu tiefe Abstimmung der Länge..."

Die technischen Daten des Horns:

· Druckkammer 130 ltr
· Länge 1,2 m
· Halsfläche 210 cm
· Mundfläche 4500 cm
· Breite ca. 55 cm
· Tiefe ca. 60 cm
· Hoehe ca. 140 cm..."

Sorry for the German text, but may be some German DIYer will read it and could hepl me. :-)

So, this design is totaly inconsistent with what I have learnt about the BLHs: the rear chamber is much larger, the horn lenght is much shorter then the "classical" method calculation would give. (Too big rear chamber give "boomy" bass, too short horn lenght will give bad low effiency, etc)
Ther is a very good article-project on the Lowther Club of Norway ( the All fun horn ) where man could learn a lot about horn theory!

I know how I need to reduct the mouth size:

...The clasical calculated dimensions apply if the horn mouth is radiating into all 8 quadrants of the space (i.e. the horn is actually hanging from a high ceiling, so that sound radiates in all directions). If the mouth exits at floor level in the middle of a very large room, sound will radiate into 4 quadrants, enabling us to halve the mouth area. Following the same principle, if the horn moth exits where wall meets floor (away from the corner), the mouth radiation goes into 2 quadrants. It follows that for corner placement we can reduce the size by a factor of 8, since sound only will be radiating into 1 quadrant of the space....

and how to compromising the mouth size:
...An accepted rule of thumb for bass horns is that the mouth area may safely be reduced to 1/5 of the original size....

and about the horn length:
...Regardless of contour, the length of a horn is a function of Fc, and At (Area at Throat). These parameters are initially balanced so that the horn is efficient enough to match the increasing output of the driver at higher frequencies, while at the same time maintaining low distortion figures (which, by the way, are insignificant in a horn system, compared to vented and closed boxes). It follows that a lower Fc means a longer horn.

However, as we have now seen, mouth size compromise will eventually dictate the horn's length. The accepted rule of thumb concerning horn length is that the horn will work as intended provided the horn is no shorter than 1/4 wavelength of Fc....

So, after this "short" leading in, I would like to ask the experts to help me to understand the Replikon design. My ultimate purpose would be to design in this way a BLH enclosure for the Fostex 166E or 166 ESR.

Thanks and greets:

Tyimo
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Old 19th April 2005, 06:30 PM   #2
ScottG is offline ScottG  United States
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I can't read German, but I suspect the specifications given are misleading.

My thought is that the low freq. generation is NOT provided by the horn but rather due to the interaction between amplifier output impeadance and the Fostex Sigma load impeadance - (i.e. they are getting anywhere between 8-12 db of gain from the impeadance interaction with an apropriate amplifier).
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Old 22nd April 2005, 07:22 AM   #3
AndrewT is offline AndrewT  Scotland
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Hi,
this is the first time I have seen 1/5 quoted as maximum reduction factor on mouth area.
I have seen 70% and 50%.
Thinking about Tannoy Westminster, I guess they must be about your 20% (approx mouth size 1.5m *0.25*2=0.75sqm.)
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Old 22nd April 2005, 08:18 PM   #4
Rudolf is offline Rudolf  Germany
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Default Re: Understanding the Replikon horn

OK, lets try a translation:

http://www.klangform-akustik.de/

Replikon incorporates the next generation backloaded horn. It´s designed as a true fullrange horn with a -3dB point at 35 Hz. This is achieved by a new kind of horn calculation, which results in the adaquate mouth area for the calculated frequency limit. By virtue of the comparably large pressure chamber the horn only amplifies frequencies below the in-box-resonance of the driver. They will not interfere with the direct output of the driver. The horn throat of the Replikon forms an innovative passive acoustic filter that keeps middle frequencies from escaping the throat, resulting in a clear and pure rendition. ...

http://www.audiomap.de/forum/index.p..._id/19186/page

In our room the FP253 did best in 130 ltr volume. This results in a in-box-frequency of ca. 55 Hz, that will be even lowered by the mouth area and length of the horn. We designed the mouth area for 35 Hz and the length for ~45 Hz, resulting in a mouth area of app. 4500 cm² und a length of ~1,2 m. First simulations showed that horn length had been calculated for too low .....

I regret that I can´t be of any more help, since I don´t know much about horns

Rudolf
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Old 22nd April 2005, 08:56 PM   #5
GM is offline GM  United States
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Greets!

I couldn't find any specs for the driver so can't really comment on the design beyond the fact that it's not the 'next generation' BLH unless they jumped into the 'way back machine' and first published it in the early 1930s. FWIW, the Jensen Imperial is one of the better versions of this style horn and will perform much more closely to their posted sim than their design apparently did.

Any idea what their 'innovative passive acoustic filter' might be? Last time I checked, that's what the rear chamber Vb/throat area was supposed to handle.

GM
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Old 23rd April 2005, 03:31 PM   #6
Tyimo is offline Tyimo  Hungary
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Thanks Rudolf for the translation!
I hope so will be easyer.

Keep on the investigation!! :-)
Greets:

Tyimo
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Old 23rd April 2005, 05:04 PM   #7
Tyimo is offline Tyimo  Hungary
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Default FP253

Hi GM!

Here is the specs!
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Old 23rd April 2005, 05:48 PM   #8
GM is offline GM  United States
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Greets!

Since Qo isn't the same as Qts, I'll have to make up a bogus set of specs to create a Qo = 0.5, then make an equally bogus set of Qes,Qms, Qts specs from the results, so how accurate any sim from them will be is open to debate, but it's the best I can do with what I have to work with.

What's Vas, I can't read it?

GM
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Old 23rd April 2005, 10:53 PM   #9
dupree is offline dupree  Germany
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Old 30th April 2005, 06:36 AM   #10
Tyimo is offline Tyimo  Hungary
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GM!
Are you out there? Did you made something up?

Rudolf!
Could you get contact with Till Roemhild and invitate here to explain he's methode?
I think your german is the best here... :-)

Greets:

Tyimo
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