# Under dash horns and stage height



## fury

Hey Guys,

Must admit I haven't heard a lot of horn setups as they're not really run in cars over here.

How do under dash horns acheive a decent stage height at eye level / middle of the windscreen?

My understanding is that our ears pick up height cues from ~4khz and above.
If these frequencies are coming from under our dash, then our perceived stage height would be quite low.
I understand that the underside of the dash helps extend the horn throat and guide the wave, but the dash stops at about stomach/chest level, and I can't see how the wave can propogate much higher than this.

Any help much appreciated...
This is the one thing "mentally" stopping me from trying horns.

I hooked up a pair of ID full bodies and BMS 4550 compression drivers with Dyn 8" MW170's to my home system and was thouroughly surprised. The sound was only ever so slightly "honky", and was easily "tamed" with a bit of foam in the throat.


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## Patrick Bateman

fury said:


> Hey Guys,
> 
> Must admit I haven't heard a lot of horn setups as they're not really run in cars over here.
> 
> How do under dash horns acheive a decent stage height at eye level / middle of the windscreen?
> 
> My understanding is that our ears pick up height cues from ~4khz and above.
> If these frequencies are coming from under our dash, then our perceived stage height would be quite low.
> I understand that the underside of the dash helps extend the horn throat and guide the wave, but the dash stops at about stomach/chest level, and I can't see how the wave can propogate much higher than this.
> 
> Any help much appreciated...
> This is the one thing "mentally" stopping me from trying horns.
> 
> I hooked up a pair of ID full bodies and BMS 4550 compression drivers with Dyn 8" MW170's to my home system and was thouroughly surprised. The sound was only ever so slightly "honky", and was easily "tamed" with a bit of foam in the throat.


Since the devices are short and wide, you would think that the soundstage would be short and wide also.

But that's not how directivity works. A device will control directivity down to a point that's dictated by it's dimensions. For instance, a horn or a midrange or an array that's 12" wide will control directivity down to 1125hz* *in the horizontal plane.* In the vertical plane, most HLCDs are less than two inches in height, so there's basically NO directivity control below 10khz or so. You'd have to do some polars to figure out where directivity collapses exactly.

Or to put it simply, you'd think that a horn would have a beam that's short and wide. But it's the opposite - the beam is tall and narrow. The narrowness in the horizontal plane reduces reflections off the car doors, which helps preserve imaging cues which exist on the recording. And the height of the soundstage is even taller than a conventional loudspeaker, *because of the short height of the horn.*

My horns under the dash don't sound like the soundstage is at eye level - it sounds like the stage reaches from floor to ceiling. Because they're so short.

Note that this doesn't just apply to horns. If you want a big tall stage, consider using a horizontal array, or at least smaller drivers. Large drivers beam.

_* speed of sound / wavelength _


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## fury

Intersting...

Would be keen to see some polar responses in the horizontal and vertical domains...

I have heard an increase in perceived stage height when moving dome tweeters from the corners of my dash/a-pillar to halfway up the a-pillar. The soundstage effectively moved up in line with the position of the tweeters (play 3.5khz and up).

With a dome, the direct sound on axis is generaly far louder than the off axis response. 
In these horns, is the (approx 45') off axis response louder than the on-axis response, to give us perceived stage height?


Maybe i'm missing something here... but stage height in a conventional system has always (to me) been dictated by the placement of the driver playing ~4khz and up.


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## Eric Stevens

fury said:


> Hey Guys,
> 
> Must admit I haven't heard a lot of horn setups as they're not really run in cars over here.
> 
> How do under dash horns acheive a decent stage height at eye level / middle of the windscreen?
> 
> My understanding is that our ears pick up height cues from ~4khz and above.
> If these frequencies are coming from under our dash, then our perceived stage height would be quite low.
> I understand that the underside of the dash helps extend the horn throat and guide the wave, but the dash stops at about stomach/chest level, and I can't see how the wave can propogate much higher than this.
> 
> Any help much appreciated...
> This is the one thing "mentally" stopping me from trying horns.
> 
> I hooked up a pair of ID full bodies and BMS 4550 compression drivers with Dyn 8" MW170's to my home system and was thouroughly surprised. The sound was only ever so slightly "honky", and was easily "tamed" with a bit of foam in the throat.


It is a psycho acoustical effect that gives us the stage height at eye level. In any good stereo system if it is imaging correctly and creating a good sound stage with a phantom center image you no longer localize to the actual speakers and the sound seems to emanate from the air where the performers would be located within the soundstage that is created.

So in a car when things are working really good you hear the stage at eye level because there is no localization to the individual speakers, if you look down the stage will move downward. 

Also if there is some frequency steering or response problems that localize you to the speakers the stage will move downward or towards the drivers that arent working correctly. So you could have the high frequencies up high and properly placed within the sound stage. The lower midrange could have issues and pull the stage downward and loose image focus with lower male vocals where female vocals are higher more centered and focused.

I have found getting a good sound stage is as simple as a proper install with simple tuning done as in crossover level and phase/polarity. It then gets better as you tune it further, and the same is true of direct radiator type systems also.

Eric
Image Dynamics


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## Eric Stevens

fury said:


> Intersting...
> 
> Would be keen to see some polar responses in the horizontal and vertical domains...
> 
> I have heard an increase in perceived stage height when moving dome tweeters from the corners of my dash/a-pillar to halfway up the a-pillar. The soundstage effectively moved up in line with the position of the tweeters (play 3.5khz and up).
> 
> With a dome, the direct sound on axis is generaly far louder than the off axis response.
> In these horns, is the (approx 45') off axis response louder than the on-axis response, to give us perceived stage height?
> 
> 
> Maybe i'm missing something here... but stage height in a conventional system has always (to me) been dictated by the placement of the driver playing ~4khz and up.


IMHO Then you are using the height of the speaker as a band aid to proper system set up and tuning.

There are three dominant factors that create a sound stage in a stereo system.

1- Time arrival
2- Amplitude
3- Phase

Staging and image placement are controlled or dominanted by different factors at different frequency ranges. 

*High frequencies* above 3 Khz are predominantly placed within the sound stage by amplitude and time and phase have very minimal effect.

*Midrange frequencies* say 500Hz to 3Khz are controlled by time arrival, phase and amplitude. At the higher midrange frequencies the placement becomes more time and amplitude dominated and at the lower midrange frequencies it is more phase and time dominated.

*Mid-bass and Low midrange frequencies* are dominated by phase and more so as the frequency gets lower. Time and amplitude still have effects but are minimized compared to the higher midrange area.

When you get Time, phase and amplitude working at all frequencies is when the sound stage gets three dimensional and starts to get involving and create emotion like listening to live music when combined with dynamic range and low distortion output.

Eric
Image Dynamics


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## fury

I understand what you're saying, and I agree if the speakers are at ear level.

If you listen to a pair of bookshelves, at ear level, then the soundstage is in front of you, at ear/eye level.
If you put that pair of bookshelves on the floor, then the stage drops to your ankles.

This is what I have experienced with conventional direct radiating speakers in a car.

How do horns overcome this?

There was a thread discussing stage height, with Lycan and Patrick taking place, I think it may have been this one (i dont have time to re-read it right now):
http://www.diymobileaudio.com/forum...cal-advanced/72655-how-move-stage-higher.html
Where by the ears determine stage height with frequencies smaller than the distance between our ears (due to differences in amplitude to each ear).
If these frequencies are playing from a source around our knee height, how then do we get a perceived stage height at eye level?


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## subwoofery

You could try with your bookshelves but I've noticed that when you have your face right between the L and R speaker, the soundstage is at eye to forehead. The further you move, the higher the soundstage. 
Another thing I've noticed is that when you have your speakers closer to you, the soundstage is well narrow but not that high. The farther (from each other) they are, the higher the soundstage. 

I've noticed that with my mids in my doors, center stage is way too high lol - but that could be my car's acoustic 

Kelvin


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## Mic10is

alot of this has to do with how Horns function in a car.
Sound follows the contours of the dash, in effect making the dash become and extension of the horn.

so despite being mounted under the dash, the dash is an extension of the horn mouth and thats how you can get Eye level Stage height with horns


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## ErinH

^so, then, is it a reasonable assumption that a more steeper angled underdash would get you better height than a less steep underdash (assuming same mounting distance from the 'end' of the dash)?


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## Mic10is

bikinpunk said:


> ^so, then, is it a reasonable assumption that a more steeper angled underdash would get you better height than a less steep underdash (assuming same mounting distance from the 'end' of the dash)?


more to do with transition from what I understand. so if the angle gets closer to being vertical it doesnt flow or transition as well.


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