GoodSoundClub - Romy the Cat's Audio Site - There is no such a thing as optimal distance

Horn-Loaded Speakers
Topic: There is no such a thing as optimal distance

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Posted by haralanov on 07-26-2012

I think it is very interesting subject and I’m looking for first hand opinions by people, using properly sounding upper bass horns in their listening rooms. I’m not interested in theoretical opinions – only by opinions, coming from personal listening experience.

Everybody knows there is no such thing as "sound of a driver" or "sound of a horn" – the sound varies depending on how the channel is being used – distance, angle, positioning in a room and many other factors. So if we take a given properly made upperbass horn channel, placing it in a big room away from the walls, then how does the sound change with distance? What I’m interested to know is there any optimal distance from the mouth of the horn (I’m talking about tractrix horn of let say 90cm diameter – the size of Romy’s UB horn), where the tone develops its maximum value. How does the tone changes when we listen to the horn at 1m, then at 2,5m and then at let say 6m away from it? Another important thing that deserves to be discussed is how does the type of sound presentation change with distance – I’m talking about the size and shape of the sound. Any deeper analyses of the subject are welcomed.

Best regards,
Petar

Posted by Romy the Cat on 07-26-2012

haralanov wrote:
I think it is very interesting subject and I’m looking for first hand opinions by people, using properly sounding upper bass horns in their listening rooms. I’m not interested in theoretical opinions – only by opinions, coming from personal listening experience.

Everybody knows there is no such thing as "sound of a driver" or "sound of a horn" – the sound varies depending on how the channel is being used – distance, angle, positioning in a room and many other factors. So if we take a given properly made upperbass horn channel, placing it in a big room away from the walls, then how does the sound change with distance? What I’m interested to know is there any optimal distance from the mouth of the horn (I’m talking about tractrix horn of let say 90cm diameter – the size of Romy’s UB horn), where the tone develops its maximum value. How does the tone changes when we listen to the horn at 1m, then at 2,5m and then at let say 6m away from it? Another important thing that deserves to be discussed is how does the type of sound presentation change with distance – I’m talking about the size and shape of the sound. Any deeper analyses of the subject are welcomed.

Of cause there is no such a thing as optimal distance. The “propagation of tone” with distance is to a great degree the acoustic properly of given listening space and I do not think that it is possible to generalize anything in it.

The bass horns do not sound good from short distance and do not sound good when they pointed to listener. Then we need to define what “bass horns” are. I would say that anything under 200Hz is benefited by indirect sound.

The “distance where tone develops its maximum value” is a bit slippery concept. I feel that instead of thinking about the “distance of max tone” we need to think the “distance of proper integration”. The upper/mid bass horns are complicated animal themselves and I do not see that it is practically possible to evaluate the “tone distance” alone. The upper/mid bass horns are narrow bandwidth devises and this tone is hugely moderated by the associated channels. You can’t just slide the upper/mid bass horns a few feet closer and further. Moving of an upperbass horn for a few feet in most of cases means a complete change of installation topology. I just do not see how it might be done from practical perspective. I think the topology of installation is chosen in respect of the configuration of the given listening space and the objectives of the listeners. This sets the upper/mid bass horns at the very specific distance and considering the obligatory need for time-alignment I do not see any flexibility in it.

So, from a theoretical point of view for sure would be nice to talk about the preferable distance to let tone to be developed and I would advocate for relatively large distance and indirect sound. However, I do not think that it makes any practical sense. I feel to change the drivers in the horns is more practical and more effective way to find optimum tone then to move the horn.

It is good idea however to use (or at least to think of using) the impediments within the bass horn’s direct sound. I did illustrate it before but I am not sure if the “impediments” directly affect “tone”. You see, by fracturing the directly output of bass horn we change the gain output of the horn. If we add let say 1dB to the upperbass horn at let say 80Hz and it changed the balance between the upperbass and MF horns then what we did was “Tone” or “Volume”? I do not have an answer to this question and in practical terms I do not think that anyone does.

Rgs,
Romy the Cat

Posted by haralanov on 07-26-2012

Yes, I know it is not correct to make any generalizations and it all depends upon the acoustic environment, where the horn is being placed and the influence of the other channels, so my original question was in context of listening to the upperbass horn itself, with all other channels switched off. So imagine you place your UB horn in the middle of a stadium, and there are no reflective surfaces but the ground. So if you listen to that bandwidth restricted sound, coming from the horn, you must be able to identify the distance from the horn, where it sounds best in comparison to other shorter or longer distances, right? But to avoid generalizations, tell me what happens in your particular case with your UB horn in your new room. If you switch off all other Macondo channels and listen only to the UB horn itself, then at what distance you prefer to listen to it and how does the sound change when you move back from the horn?

You said “The bass horns do not sound good from short distance” and you probably meant to say upper-bass horns. Then would you tell me about the specifics of the term “do not sound good” – which property of sound is not correct within the usable range of the horn and what means short distance. I remember you once said you was listening at extreme nearfield (1,80m) in your old room, so is it what your refer to short distance?

Posted by rowuk on 07-28-2012

It is easy to calculate the lobes that are created when we use multiple drivers. That means we can mathematically derive the closest distance that all of the horns in the entire system will "play" together. When we are close to sound sources, the proximity effect will change what we perceive to be the frequency balance. This is often a problem in many recording studios where I have spent a lot of my life. I do not want to be less than 10 feet away from any "studio" monitor that I have ever heard.
We have to factor the resonance of the room also into the "listening distance" a live room or wall proximity will dramatically change everything.

The problem with this thread is that we are separating things that belong together. Divide and conquer only works when destroying countries or personal relationships. As I will never set my reproduction equipment up in a freee field environment, I see no way to answer the question.

Posted by Romy the Cat on 07-29-2012

rowuk wrote:
It is easy to calculate the lobes that are created when we use multiple drivers. That means we can mathematically derive the closest distance that all of the horns in the entire system will "play" together.

Nope, it is imposable. The lobes will derive from the crossover slopes, proximity of driver’s resonances to the horn rate, proximity of the horns axis and many other factors, room acoustics and many many other factors. I truly do not think that anything besides the empirical methods would bring any result. The drivers integration is not a Boolean algebra and there are always degrees of integration acceptance. Anyhow, the question Petar asked doe not deals even with relation between distance and integration but between distance and tone. This is WAY more complex subject and I do not think that anyone would be able to generalize on it, particularly if they know what they are talking about.

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