does on axis waves reflect in straight lines.

[The Camry]

For example let's say instead of having a tweeter faced on axis to you. You had it faced towards a wall that was exactly 45 degrees from your head. Would that give you the same response?

If you took a laser pen and pointed it at a 45 degree mirror. That mirror would reflect the laser at a 90 degree angle. If your face is at the end of the 90 degree laser...then in my head. A soundwave would be effected the same way.

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[trumpet 5,000+ posts]

You're looking at a single tree and forgetting about the forest. I recommend you do a web search for sound reflections. This is a very well researched and documented subject of which the basics translate to all venues of sound reproduction, whether it's a concert hall, your living room or a car. A book I highly recommend is 'Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms'. It is written in relatively plain English, but it's still rich with excellent information.

@keep_hope_alive

 

[Boominburban 10+ year member]

And check out the section on sound wave propagation ... specifically sub freq waves ...... 1/4 wave-1/2 wave-3/4 wave- full wave. And how it affects the level of sound pressure ....

 

[keep_hope_alive Premium Member]

if you only consider specular reflections of smooth, hard surfaces (such as glass), then yes. many acoustics programs assume straight lines, or rays, for calculations of reflections because the math is easier. the frequency response of the reflection varies with the absorption and diffusion of the reflecting plane, which programs can also account for.

in reality, consider that sound spreads from the source spherically - like waves in a pool. fill your tub with a few inches of water then drop a single marble in it. watch the simple spherical wave reflect and become chaos. that's what happens in a room or confined space with flat surfaces. you hear the first arrival which is typically the direct path, then you hear all reflections. each reflection varies in frequency response and amplitude. frequency response is determined by the polar response of the angle relative to the reflection and the absorption coefficients of the reflecting surface. as the source arrives at the reflecting plane, the resulting reflection varies in origin and spreads hemispherically. as reflecting waves interact with other reflecting waves the result is total chaos.

in an automobile, what we can control is the frequency response and amplitude of the reflections. we control this with location and aiming of drivers.

 

[The Camry]

Well i was thinking itd be interesting to have just one tweeter or two side by side facing upwards on your dash with something near your rearview mirror that would direct the signal directly to both listeners ears.

 

[Boominburban 10+ year member]

if you only consider specular reflections of smooth, hard surfaces (such as glass), then yes. many acoustics programs assume straight lines, or rays, for calculations of reflections because the math is easier. the frequency response of the reflection varies with the absorption and diffusion of the reflecting plane, which programs can also account for.
in reality, consider that sound spreads from the source spherically - like waves in a pool. fill your tub with a few inches of water then drop a single marble in it. watch the simple spherical wave reflect and become chaos. that's what happens in a room or confined space with flat surfaces. you hear the first arrival which is typically the direct path, then you hear all reflections. each reflection varies in frequency response and amplitude. frequency response is determined by the polar response of the angle relative to the reflection and the absorption coefficients of the reflecting surface. as the source arrives at the reflecting plane, the resulting reflection varies in origin and spreads hemispherically. as reflecting waves interact with other reflecting waves the result is total chaos.

in an automobile, what we can control is the frequency response and amplitude of the reflections. we control this with location and aiming of drivers.

And this is why the same exact model car, with different interior options will need to be tuned differently .... I was trying to explain this to someone a few weeks ago .... Great reply ....

 

[wew lad 5,000+ posts]

It's really great to see such informative detailed information, I just love reading things like this that teach me new things. You wouldn't know it, but a lot of this translates into other things in the world that have to deal with pressure and aerodynamics.

Anyways, it sounds like the interior of cars are so complex that your best bet would be to simply test different locations and aiming, albeit time consuming.

 

[SimulatedZero 10+ year member]

Would mounting the tweeters off the dash about an inch and putting them in tweeter spheres really help cut down on some of the initial reflections and help with clarity? I know they would still have peaks and cancelations from everything else still in the car, but I was wondering if it was worth the effort?

 

[trumpet 5,000+ posts]

Would mounting the tweeters off the dash about an inch and putting them in tweeter spheres really help cut down on some of the initial reflections and help with clarity? I know they would still have peaks and cancelations from everything else still in the car, but I was wondering if it was worth the effort?

It will probably sound a little different. Without accurate measurements of before and after you would have to rely on your ears for purely subjective comparisons. That is a flawed method of testing. You're influenced by confirmation bias to judge the outcome, which means if you want to hear an improvement your mind will decide it sounds better. It's more difficult to get accurate measurements of high frequency response at the listening position in a car because you can't separate the initial sound from the response of the interior. They are one and the same.

 

[SimulatedZero 10+ year member]

Fair enough. Awhile back I was looking at redoing my mids and highs and came across that on another forum. Granted it was all subjective, but a lot people were saying it had a much clearer and open sound stage. For all that's worth. They also *claimed* it helped with sibilance which is what got me interested.