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Understanding the Replikon horn
Understanding the Replikon horn
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Old 8th May 2005, 01:38 PM   #21
Klangform is offline Klangform  Germany
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Default Understanding Replikon

Hi @ all,

first of all I want to introduce me. My name ist Raffi Bauer and I am the constructor of the Replikon Horn you are discussing. Please forgive my bad english. It is a long time I have practised English.

I can understand your questions about this new method of constructing Backloaded Horns. My partner Till an I have investigated the last 7 years to optimize backloaded horn enclosures. I will try to give a translation of our philosphy from our homepage and hope you can understand a little. Nevertheless we are planning to fix the pahe hornlautsprecher.de within the next month. We will explain the way in constructing horns with this method.

Philosophy


To reach the best performance over the whole audio spectrum, our Till Römhild (MSC) has developed new theoretical concepts for the calculation and construction of hornspeakers over the last couple of years overcoming present but still well known dysfunctions of classical horn constructions.

Backloaded horns providing very deep bass reproduction need child- to man-tall enclosures and often kill any kind of atmosphere in living rooms. Let us take a walk mentioning the physique inside a backloaded type horn speaker cabinet:

A horn as an acoustic transformer forces an increase of radiation resistance of sound and output pressure and decreases distortions by reducing the mileage turn length of the membrane hub during bass reproduction. To reach a deep enough reproduction the mouth surface of the cabinets needs to be very large and very long, otherwise basses are sizzling and funny but not really true!

Causing frequencies lower than 400 Hz are reproduced in a spheric 4 PI room it is possible to reduce the mouth surface to a half or a third of the theoretical needed value, if the cabinets are placed near the walls or corners of their audience room.

But mentioning this case conventional horns are still too large. If the mouth surface is reduced to create smaller dimensions it does not match the length of a calculated horn, so it does not causes flat- frequency response by this misconstruction.

And then there are the interferences between the directly radiated sound in front of the driver and the backward radiated sounding via its horn; their frequency ranges overlap often over more than two octaves, and that is too much if you want to create a single point acoustic transmission source. This has its reason in too small volumes of pressurized chambers and leads to a wavy low-basic midrange area and an overproduction of higher basses, so this looses precision at basic range frequencies and sounds a little bit dump and foggy, especially during voice reproduction. And this may lead to another phenomenon: The higher overproduced bass range hides the chance to recognize deep basses even at louder volumes causing on two much efficiency in a too small range. And if it is tried to muffle the too loud basic deep-mid frequency range inside the horn the lower boundary frequency increases, the cabinet stops breathing and does not sound really free like it could be …

However, our Replikon embodies the next generation of backloaded hornsystems. As a true fullrange type concept are -3db at 35 hz delivered. She came to us through a new type of process in calculating horns for finding the matching mouth surface to a given low boundary frequency and is quite handsome in comparison to other real large speakers!

The choice of a relative large dimensioned pressurized chamber in comparison to classical horns makes it possible to amplify only frequencies lower than the resonance frequency of the built cabinet, preventing interference effects between direct radiated sound from the driver and the backward emitted driver sound of the horn. But taking deep care about preventing midrange in the horn the horn neck we realized a rather new passive acoustic filter type with a special geometry. So after all a true natural performance with microscopic precision was reached, without any muffling killing deep basses. So basses can work at their best performance without any resonances. Powerful driven and fully controlled sound appears without any distortion at all. She (the Replikon) is a gift for best possible listening music living room performance,- including your wife next to you, and this is not to be taken for granted!

During a process of engineering, testing and research we found out that the geometry of a horn created through production processs has a great influence to the flatness of the overall frequency response. So Klangform Akustik Horns are free from any discontinuities preventing straight wood plates which would lead to interferences inside the horn, and therefore a reproduction witch is absolutely stable in preventing any unsteadiness of the air stream inside the horn. Our horns are as true as possible to their own given mathemathical functions, because we disclaim from straight wood parts in production process. We just only take from full wood blocks the curves we need for each construction, no instable edges anywhere at all!

To realize this value without any compromises concerning design and to adapt Klangform-Akustik Systems fully to emotional living room ambience we took much care of the optical expression of our products. A floating harmonic edgeless appearance is provided by our “form follows function” motto and comes due to passion and warmness not only to women hearts, because we only use best beech and birch wood products from Germany.

They have best acoustic facilities and enable the visualisation of the cut-edge with a smooth and warm prominent design. Our Hornsystems are moulded on digital cnc-machines and are glued in a disk on disk procedure to get massive and solid resonance free cabinets.


Have a lot of life!


Yours Rafael Bauer, CEO

If you have further questions feel free to ask

Greetings
Raffi Bauer
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Old 8th May 2005, 02:43 PM   #22
Tyimo is offline Tyimo  Hungary
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Hi Raffi!

Thank you very much for you kind and detailed answer!
You helped me (or us) a lot!
Could you give us some suggestions how to build a BLH in your sytle with the Fostex 166E or 166ESR? (May be you have some simulations already)
I ask this because there are several diy-er, how would like to know is it possible or not, and would like to build such a wonderfull design like yours.

Thanks again!

Greets:

Tyimo
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Old 8th May 2005, 07:03 PM   #23
mgoedeke is offline mgoedeke  South Africa
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Hallo Raffi, danke für die Werbung

Could you please elaborate more on your model? I meantioned the effects you have likely made play along symbiotically further up. Are you prepared to share this?

That most designs run over too wide a range is clear, but this also means stronger loading of the system (generally in the upper-bass). The likely trade-off of the larger rear chamber is that the horn will only load the driver acoustically at a couple of (lower) frequencies, but if the results posted are a true I recon it is a very fair trade-off.
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Old 8th May 2005, 11:33 PM   #24
GM is offline GM  United States
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Quote:
Originally posted by mgoedeke
It is more of a continuum of which effect predominates. For these kind of "horns" (much too small mouth and generally very low flare rate) you need the system to resonate more strongly to get useable output (i.e. more of a "bandpass" and less of a pressure-> velocity "converter" type of behaviour which you'd get with a correctly sized mouth).
Greets!

Hmm, we're discussing BLH horn design here AFAIK, ergo neither can we make it a 'converter' in anything less than a room of the equivalent volume the front of the driver 'feels' nor are we interested in max efficiency, otherwise the response will be very bass 'heavy'. Regardless, it doesn't change the fact that whether it's reactance annulled or not, they are both just bandpass designs with a very large, long, expanding 'vent'.

GM
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Old 9th May 2005, 12:25 AM   #25
mgoedeke is offline mgoedeke  South Africa
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A design where the bass-midbass is boosted a fair bit has potential in that one can EQ out the difference and gain a lot of headroom. I have been toying with the idea of using a larger bi-polar capacitor to achieve this in a very inexpensive potential school project I have lined up for my little brother. It will draw on inspiration from TD's External air path idea and I am aiming for 60Hz extention, not 35. Planned amplification will be a PC speaker with 5W output. This is OT though, so guilty as charged. Already found a promising FR speaker for silly money (like 2 US$) that measures rather well.
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Old 9th May 2005, 12:43 AM   #26
GM is offline GM  United States
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Quote:
Originally posted by Tyimo


GM!

Nice sims you did, but why are they saying that the line length for ~45 Hz is 1.2m?!? (1.2m =71Hz.)

Tyimo
Greets!

Horns sitting on the floor have an acoustic mouth area with double the actual area due to the mirror image projected on the floor. The acoustic length of a pipe, etc., is somewhat longer than the actual length. Through much impirical evidence, it's been determined that this so called end correction varies with the terminus's radius and what, if any boundaries it's near.

If these were the only issues, it could be easily calc'd with a fair degree of accuracy, but alas, the flare's 'M' factor complicates it, so unless you're prepared to wade through all the math like MJK and a few others have, you build a prototype and measure it. In general though, if a BLH's mouth terminates at the floor and has at least an 1/8 size mouth (including the mirror image) area of Fc, then it can be ~an octave shorter and will still perform acceptably, hence a ~71Hz length for a ~35Hz Fc.

I guess what you're failing to account for when using rules-of-thumb engineering on a fullranger BLH design is that you don't want the horn's gain to 'be all it can be' or it will completely overpower the mids/HF, hence the need (or lack thereof) for a long horn with a big mouth WRT Fc.

The other consideration is where do we want it to begin rolling off? With a BR ~flat to 30Hz, if it was 'boomy' in-room you just make the vent longer or damp it, but lengthening a horn and/or getting the damping right can be a tedious affair, so best to design in some roll off. This one sims ~35Hz/ -3dB, just as advertised, and a reasonable compromise overall WRT size/gain/LF extension.

Nice design, and with the 'stacked' construction/apparently high quality wood, it's well built and not just another pretty piece of 'furniture' masquerading as a hi-perf audio speaker.

GM
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Old 9th May 2005, 12:51 PM   #27
mgoedeke is offline mgoedeke  South Africa
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At LF this design would have nothning to do with a horn, much more with a bass-reflex (helmholz resonance) with a super-imposed resonance at 1/4 wavelength (accounting for some end-factor correction). Loudspeaker output in this range will be rather insignificant and dominated by the rear-part. As one moves up the FR range one has to factor in the the acoustic dimention of the "horn"-path and phase difference in such a way as to not cause too many interferences with the front radiation in this transitional band. A larger rear chamber (and a suitable narrow-band horn geometry) would make this band smaller. This is followed by the band where the output is predominated by the output of the loudspeaker as the rear wave is damped acoustically.

The interresting thing is that they have presumably set up a model with which to optimize this behaviour if their postings are to be believed they will be making this available (or perhaps they are just teasing, who knows). Such a model might do the BLH FR fraternity a world of good.
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Old 9th May 2005, 02:57 PM   #28
Klangform is offline Klangform  Germany
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Hi @ all,

ok I have no problem to share our ideas regarding construction horns to you.

The Replikon Horn ist not a hybrid horn.

@tyimo i will make a simulation and post it.

@mgoedecke

first of all I think it is well known that backloaded horns work as expo tml below 100 Hz.

So what makes the horn sound like characteristic as a horn. You are right with your suggestion that a horn with a small chamber loads a horn stronger than horns with big rear chambers. I suggest that it is the load of the frequencies between 100 Hz and the cut off frequency lets say 700 Hz which is required by the small rear chambers.

But especially these frequencies interfere with the direct radiation of the driver. Our aim was to reduce these interference, so that the horn only loads the fq range below the QTB of the driver in the chamber. We have then only a load of the lower frequencies.

So in the praxis we have a lower SPL of the air load than conventional horns, but do not forget that in the praxis of conventional horns there is a need of damping materials to eliminate the peaks in the upper bass. So with the damping you actually kill most of the high load efficiency.

Nevertheless we have to admit that our horns sound therefore different without that what might be characteristic for a conventional horn. But at the other hand you have a very smooth reproduction of the frequencies below 100 Hz wihich is also not comparable with tml or br sound. Because of the lack of interference in combination with big rear chambers you are able to listen frequencies down to 30 Hz -3db like in my listening room.

The big rear chamber in combination with a horn neck AH 0f 2/3 of SD we reduce the distortion factor in addition.
The result is a distortion free sound reproduction of the horn loaded frequencies. Due to the fact that we also use normaly 2/3 of SD the sound is very near to oncken enclosures but in additional to the air load of the horn the bass sounds very very open with clear 3D image down to the lowest frequencies.

The construction:

My Partner Till has worked out the mathematical basis of this kind of construction:

Our formulas wil be presented in June 05 at http://www.hornlautsprecher.de

Just one idea to that:

We have 3 basic formulas in constructing our horn enclosures:

At first we have the co-orrdination frequency of the rear chamber
Second we have the coordination fq of AM
Third is the coordination fq of the length

enclosed you find the impedanz curve. As you see it is like a bass reflex enclosure. Nevertheless it does not sound like a br.

It is a totally different approach to the material horn enclosures and maybe the definition horn is not suitable, in fact our horns follow the exponential function.

There is also a lot of other thigs to say to that, but that is just for the beginning.

Greetings
Raffi Bauer
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File Type: jpg impedanz.jpg (49.9 KB, 2077 views)
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Old 9th May 2005, 11:05 PM   #29
mgoedeke is offline mgoedeke  South Africa
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One gets a couple of effects which if combined in certain ways make certain "Schallführungen" (to introduce a German word) which are labelled BR, BLH, bandpass etc. However the lines become less clear when one starts to make hybrids between these categories by employing less tandard configurations and a bass-reflex that tunes more broad-band would probably best describe the effect we are seeing with a couple of arberations at some frequencies which need to be taken care of (geometrically and employment of some basic acoustical concepts, the use of which needs to be optimized, possibly resulting in certain alignments)

What would interrest to me is whether the model you want to present will be usefull for higher-gain situations where one filters out the added gain at LF (where Fr drivers are generally very weak) or whether it is generally more analogous to BR with a delayed rear radiation.

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Old 10th May 2005, 07:38 AM   #30
Klangform is offline Klangform  Germany
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Hi mgoedecke,

the interesting thing of this metod is, that in fact the impedance curve looks like bassreflex it does not sound like bassreflex. But why is it so ? Comparing to BR enclosures the LF gain has more volume, a wider and deeper stereo image. It sounds very open . You have not a break in the stereo image, where you have a sharp stereo image of the direct radiated sound, but a lack of stereo image in the lower frequencies. Due to the fact that the horn makes a good adaptation of the air molecules to the room response (Anpassung des Strahlungswiderstandes an den Raum) this is resonsiblble for this open bass response.

Now we have tried several times to construct the horn smaller by (shorten length, but at the same time shorten AH and AM !!!!!!!) The smaller you build the horn, the more it sounds like Bassreflex, in fact the impedance curve is the same as for example the big horn. That leads uns to the knowledge that the bigger AM is and in relation to that also the length, the bass sounds more open with a brider and opener stereo image.

Now to your question. It is more analogous to Bassreflex. The Replikon for example has a length of 1,4meters. We have made the experiance that a length bigger than 1,6 meter can acoustically be identified as delayed bass, will say you can heear the timing problem. Only very good ears are aible to listen time delays of 1.4 meters ore less. So this is a further advantage. I have no more timing problems.

The weakness of the driver by FS is a problem you are right. Therefore we do not coordinate tuning frequency below FS of the driver.

Now this as also a reason why we use likely drivers with QTS more than 0,4, because in addition with big rear chambers you can reach a high gain by low frequencies. Nevertheless the Replikon is loaded by the Fostex FE 208 Sigma and it functions very well.

There is also a technique of using drivers with QTS 0,2. To enhance deep bass you can make the horn neck AH bigger than simulated and calculated. So you have also the chance to variable between these three parameters of construction till you adjust the driver to the horn.

If you ask me directly what the main advantage of this kind of constructing is, I will answer you first: Very open and low bass response with a very deep 3D stereo image down below to lowest frequencies.

The disadvantage is with no doubt the lack of high gain in the upper bass which is characteristic for conventional horns and in consequence the lower SPL.


@tyimo

enclosed you find a simulation for the FE166E. As I mentioned above the FE166E has a low QTS and is therefore not very ideal. So that I suggest to place the horn near to room corners. In fact that the horn only loads frequencies below 120 Hz there will be no resound of upper bass frequencies.

Greetings
Raffi
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