[Invinsible]

Firstly I would suggest pushing them in the corner. The idea of having the tweeter in the sphere is to reduce diffraction which creates peaks and dips in the frequency less than 8kHz. it may also help to reduce some amount reflection coming of the windscreen, dash floor and A piller provided you have mounted them 3" above the dash floor, 1" away from the Apiller and 2-3" away from the windscreen. Dome tweeter have wider dispersion and we surely dont want to had more reflection or any peaks. Placing sphere enclosure in the corner will result in breaking the smoother dispersion that would be created by the sphere resulting in basically not much of great results.

[Gill]

Originally Posted by DerAlte

@Gill, are you not able to mount it on the A-pillar cladding like in the pic above?

Alternatively, if you are mounting those wooden cups, position them in the corner (where windshield, A-pillar and dash meet).
* Position the pods as far as they will go in that corner. Make sure you have drilled holes in the pod for the wire to come out. Hold it down with cellotape temporarily
* Use M-Seal to fashion a profile below the pod, to extend gradually beyond the dash. Extend it till it supports the cup stably in that position (without the tweeter). Should look like an elbow ultimately. Position it to get the right direction (left one towards driver, right one towards passenger). Smoothen it to look good
* Allow this profile to harden, and then stick it to the pod with Araldite. Paint the whole assembly to match the color of the dash
* Mount the tweeter in the pod
* Use a long strip of double-sided tape below this profile to stick it to the dash where you want it

Voila!

Thanks Sir, You gave me a lead.

Originally Posted by Invinsible

Firstly I would suggest pushing them in the corner. The idea of having the tweeter in the sphere is to reduce diffraction which creates peaks and dips in the frequency less than 8kHz. it may also help to reduce some amount reflection coming of the windscreen, dash floor and A piller provided you have mounted them 3" above the dash floor, 1" away from the Apiller and 2-3" away from the windscreen. Dome tweeter have wider dispersion and we surely dont want to had more reflection or any peaks. Placing sphere enclosure in the corner will result in breaking the smoother dispersion that would be created by the sphere resulting in basically not much of great results.

Spot on, but I am confussed between first line and end line.

[Invinsible]

Oops! Just a typo error i meant i wouldn't suggest pushing them in the corner..

[DerAlte]

If one visualizes in 3D, there doesn't seems to be a likelihood of reflections & diffraction if the tweeter is kept in the corner facing the opposite front head rest. On the other hand, as mounted on the A-pillar cladding, the problem is definitely possible. In either arrangement, the tweeters are firing (effectively) off-axis.

Let me explain: Mounted in the corner, the high frequency beam emanates with theta 45Deg around the main axis, which is pointed at the opposite head rest. It is not difficult to visualize the beam cone size, and that the closest it encounters a significant reflective surface is the window beyond the seat, the ceiling and perhaps a bit of the dash board.

On the other hand, with the A-pillar base cladding mounting the main beam encounters a large expanse of the windshield directly in its main cone, giving rise to a strong reflection.

In either of the above cases, there is a strong reflection to account for from the side window glass, appearing in the opposite ear. Effectively, this is 'cross-talk' - signal from left channel appearing as a part of right, and vice versa. Do you think this is a big problem?

Seen in a continuous sense, multiple reflections will be continuously happening, but whether they lead to degradation of the image or not has to be seen w.r.t. the area where the waves have maximum amplitude: in the main beam cone and significant reflections! Beyond that, IMHO there is no limit to what one can imagine can happen.

Much more significant is the noise coming in from outside, which one has no way of stopping unless the windscreen, windows and car body are made of concrete (kind of defeats the purpose of a car, doesn't it), and the fact that one is concentrating on the road while driving, makes it rather difficult for the aberrations in nuances to show through. One does wish that one can replicate the conditions of a purpose-built music room in the car. Very few people would replace their music rooms with a stationary car.

While I am not dismissing the idea of interference and diffraction affecting the sound, perhaps you can throw some light on what other considerations we should account for?

EDIT: If the pod @gill has is kept in the corner, the tweeter will be 3" away from any nearby surface - A-pillar, windscreen and dash! :-)

[Gill]

Originally Posted by DerAlte

Position it to get the right direction (left one towards driver, right one towards passenger).

Originally Posted by DerAlte

If one visualizes in 3D, there doesn't seems to be a likelihood of reflections & diffraction if the tweeter is kept in the corner facing the opposite front head rest. On the other hand, as mounted on the A-pillar cladding, the problem is definitely possible. In either arrangement, the tweeters are firing (effectively) off-axis.

Let me explain: Mounted in the corner, the high frequency beam emanates with theta 45Deg around the main axis, which is pointed at the opposite head rest. It is not difficult to visualize the beam cone size, and that the closest it encounters a significant reflective surface is the window beyond the seat, the ceiling and perhaps a bit of the dash board.

On the other hand, with the A-pillar base cladding mounting the main beam encounters a large expanse of the windshield directly in its main cone, giving rise to a strong reflection.

In either of the above cases, there is a strong reflection to account for from the side window glass, appearing in the opposite ear. Effectively, this is 'cross-talk' - signal from left channel appearing as a part of right, and vice versa. Do you think this is a big problem?

Seen in a continuous sense, multiple reflections will be continuously happening, but whether they lead to degradation of the image or not has to be seen w.r.t. the area where the waves have maximum amplitude: in the main beam cone and significant reflections! Beyond that, IMHO there is no limit to what one can imagine can happen.

Much more significant is the noise coming in from outside, which one has no way of stopping unless the windscreen, windows and car body are made of concrete (kind of defeats the purpose of a car, doesn't it), and the fact that one is concentrating on the road while driving, makes it rather difficult for the aberrations in nuances to show through. One does wish that one can replicate the conditions of a purpose-built music room in the car. Very few people would replace their music rooms with a stationary car.

While I am not dismissing the idea of interference and diffraction affecting the sound, perhaps you can throw some light on what other considerations we should account for?

EDIT: If the pod @gill has is kept in the corner, the tweeter will be 3" away from any nearby surface - A-pillar, windscreen and dash! :-)

Does that means when tweet fires at Opp head rest, if reduces the reflection from right side window glass? Reason I am asking is, I intend to have the tweeters on axis, the right and left tweet both aiming at drivers seat(Both beams meeting in front of drivers nose.
Would this be leading to more reflections then the tweet firing off axis?
Yes you are right about the distance, there is ample distance of tweet from surroundings.

[DerAlte]

Arrey Gill-saheb, just draw your desire on paper and you will realize the folly! Look, the closer the ear is to the sound source on-axis, the louder it sounds. So, your right tweeter will fire on all barrels into the right ear. But, the left one, being at a much greater distance away, will produce a correspondingly weaker signal at your left ear. What do you think will happen? Wonky right-heavy image! You could also land up hating the treble-heavy shrill sound. Ideally both tweeters should be equidistant from your head, but that is not possible in a car.

An additional problem in your proposed arrangement is that image will be totally spoilt for anyone in the front passenger seat. For them the image will be totally above the steering wheel.

In off axis mode, since you are not on the main axis, the signal at your right ear is weaker, but it will turn out to be as strong as the left channel signal (which is on-axis) coming from a longer distance. Result, better balanced image, and no chhan-chhan headache. You happy, passenger seat-wala/wali happy.

[Invinsible]

If one visualizes in 3D, there doesn't seems to be a likelihood of reflections & diffraction if the tweeter is kept in the corner facing the opposite front head rest. On the other hand, as mounted on the A-pillar cladding, the problem is definitely possible. In either arrangement, the tweeters are firing (effectively) off-axis.

It's not just about where to face the tweeter. Try having the tweeter in sphere and place at the extreme corner. One will hear the high frequency more sharper. All the diffraction takes place above 1khz and below 15khz mainly. Try moving the sphere away from the winshield and there will be some noticeable difference in the freq. response in which case it would sound all the more sweeter. It's the windscreen angle that also plays the imp role. But mainly what we looking at is smoother dispersion of the high freq. of the sphere. Any sharp edges around the sphere enclosure or off the tweeter will add to the diffraction. Diffraction works in a different manner, any change in slope will cause diffraction. The greater the change in slope, the greater the diffraction. Diffraction is an issue for the first 10 milliseconds of travel, at least. Sound travels eleven feet in 10 millisecods. This is also one of the reason that home speakers frequently image better than the car speakers. At home we have the luxury of pulling them away from the sidewalls. Diffraction occurs when the sound crosses a sharp boundary. That's why the typical rectangular enclosure causes so much of it. The most bang for the buck is found by putting a roundover on the front of the enclosure. After that's done, putting the roundover on the rear of the enclosure has benefits too. And after that's done, moving the speakers away from the sidewalls will yield an improvement.
A spherical enclousre will sound fairly similar to an enclosure with a roundover on the front and the back, since the shapes are somewhat similar. The reflection are still there, but they're not in that critical 10 millisecond window. Placing the tweeter in the corner may sound good but imaging them is hardest part compared to placing them little away from "windscreen". Diffraction can add a bit of harshness to a speakers response. Having said that biggest audilble improvement from reducing diffraction is an improved soundstage. Once you move the tweeter away from the windscreen, one will notice that the soundstage or imaging will be better and can be easily made them dissappear. The other imp part is direction where even a few degrees can pull the image on either side. Having the tweeters facing the opposite side headrest is not the only solution. It's not as easy as it looks. I had to keep playing around with different deg. for days to get the imaging right. Both my tweeters are playing offaxis. With degres set to get the perfect center imaging.
In the end all I can say is it's not easy as it looks. Just getting the tweeter in a sphere and placing them on the dashboard is not the only thing, more imp is where you place them and the angle the tweeters.

Here is the pic of the spheres placed on the dash in my car.

[Gill]

@ invisible, Can't agree more with you, its not only about sphere and dash, it's about making it sound better, that's why this thread is there.

I have tried the tweets in almost all the postions since last 24 days like close to Midbass in doors,in center of dash, on A-pillars, aiming at each other, and so on.I liked them palying on-axis alot, with the help of balancing and time alignement.
Moreover the setup is to tuned up for a driver seat only.So I have a liberty to do on-axis position.

PS:-Car Audio is quite Complex :-O

[shreyasma]

@Invisible,

The tweeter pod looks like a 60's microphone. nice! nice! nice!

Is that white thing, at the bottom, double sided tape? And is the steel thing a hollow tube or a solid piece?

[Invinsible]

Originally Posted by shreyasma

@Invisible,

The tweeter pod looks like a 60's microphone. nice! nice! nice!

Is that white thing, at the bottom, double sided tape? And is the steel thing a hollow tube or a solid piece?

Well, microphone or not but it works great, the path length distance between Right tweeter and Right midwoofer is around less than 1", same is on the left hand side. That way running them in passive and applying TA, makes the imaging much better. What distracts is the angle of the tweeter which are angled in such a way where they cross light below the Rear view mirror. Soundstage is more wider, adds a lot of space to the music giving the illusion as though one is sitting in much wider/bigger enviroment. There is a natural echo effect more like sitting in a Hall, that takes place also due to the help of rear speakers that are bandpassed along with TA. Vocals are right in the center with instruments playing around. The left tweeters are little more than 30deg offaxis with right at 45deg.
It's standing on double sided tape and yes it's a solid metal spacer with a brushed metal finish that are easily available in hardware stores. One could find many other better options once visit it. Am in the process of getting a bracket done for the same which will be at the bottom of the spacer, on the dash floor with the other side going into the Apiller for the support. I had thought of painting the spacer black that way it would like one piece along with the sphere but chose to leave it the way it is right now coz of the finish.

@Gill: I am guessing you tried those position without the sphere enclosure. Once you have the tweets in an enclosure with giving them a height of minimum 3" off the dash, they will work differently. With the dyn tweets that you have there is a light edge on the outer side which you might want to smoothen it out. In a sphere the result are more smoother and it's easy to have a feeling of tweeters being invinsible provided you keep some placement needs in mind.

[DerAlte]

Originally Posted by Invinsible

... All the diffraction takes place above 1khz and below 15khz mainly. ... it would sound all the more sweeter. ... Diffraction works in a different manner, any change in slope will cause diffraction. The greater the change in slope, the greater the diffraction. Diffraction is an issue for the first 10 milliseconds of travel, at least. Sound travels eleven feet in 10 millisecods. This is also one of the reason that home speakers frequently image better than the car speakers. ... The reflection are still there, but they're not in that critical 10 millisecond window. ...

Your description reminds me of Gulzar's lyrics, @invinsible.

You seem to be ignoring the fact that in a car tweeter, the dome is inset (as opposed to home setup tweeters which project beyond the mounting plate). In a way, that seems to be a worse inherent generic problem (w.r.t. diffraction as you describe) - diffraction is expected to be 10 times worse in ALL car tweeters, since the first discontinuity (encountering a step, which you perhaps described as "change in slope") is at the highest wave strength near the dome. Wonder why *none* of the designers have caught this so far in the last 30 years!

There is significant attenuation at the edge of the wave, i.e. high frequencies emanate more as a paraboloid lobe than a cardioid lobe. If one has to go by your description, *almost all* speaker system designers would have had tweeters jutting out of the boxes like submarine periscopes or eyes of martians in cartoon strips.

Of course I understand emotion begins where engineering stops, but IMHO it is hardly constructive if we propagate myths without a rational way of explaining cause and effect. If sound travels 11' in 10ms, and one says that diffraction is about the first 12", one should realize that is about the first 1ms of the wave propagation - and one hasn't even accounted for the wavelength to relate to whether diffraction would take place or not. You seem to contradict yourself. Reflection, on the other hand, is much more significant in the window of time and distance you describe - many more reflected wave possibilities which spoil the party, so to say!

Anyhow, the focus of the discussion being @gill mounting his tweeter without them toppling, "diffraction" is an unnecessary digression. Reflection is a bigger issue. I am sure Gill-sab will figure out what suits his taste, by playing around with the direction before fixing it.

Originally Posted by Invinsible

... a feeling of tweeters being invinsible ...

Errr... I am sure you meant to say something else, rather than 'tweeters cannot be destroyed'!

[Invinsible]

Originally Posted by DerAlte

Your description reminds me of Gulzar's lyrics, @invinsible.

Or rather like a lullaby I should say.

The only reason I added about diffraction and reflection occuring at the peak was against due to the mounting of the tweeters into the extreme corners. There is reason why sphere enclosure is used here, to reduce the diffraction that would occur normally and placing them in extreme corners would'nt help at all. And it surely doesn't eliminate it or the reflection that would always stay come what may. All this is based on the experience I had while trying these spheres in various location. The solution I found best to my choice may not work for everyone but it kinda gives an idea what can work the best. Trying out is more imp than just going by what others prefer.
There have been award winning competition projects that have involved spheres not just for the tweeter but by even placing the mids in it even almost 20yrs back. Some interestingly going for more than 2 tweeters in front to get the perfect soundstage and cancelling of some of the reflection that's present. JL audio did a project with 6 tweeters in front. But as I said it what one prefers may not be the choice of others.

[Gill]

I have enclosed some pics of the problem that I mentioned few posts back. The wooden pods does not fits in. The tweeter is too big to fit on dash.The contact area between dash and wooden pod.Next weekend will look for A-pillar options.DIY does test your patience limits.

[Invinsible]

looks good. The idea of having the pods is already discussed. I say it fit perfects. Just smoothen out the the edge on the pods where the tweeter's outer ring ends. Also just get a stand and get one made of about 3". It will make quite a bit of difference.

[Gill]

Pod with stand won't fit in. I am thinking of droping these pods outright.
What If I sand out the base of pod so that the contact area is more and flat too.With a flat base it might fit in.How about the placement in last pic?