tweeter placement and comb filtering

pentoncm

I plan on installing my db component tweeters in my A pillars as far forward (aimed opposing headrest which matches 6.5 midrange in door) as possible in order to get reduce the path length distances as much as possible. The only problem with this location is that the instrument panel goes really high and will interfere partially with the sound out of the driver side tweeter. If I were to put the tweeters closer to me on the A pillar (very sharp angle), thus avoiding dash issues, I fear the stereo image will suffer because the near tweeter will be significantly closer in proportion to the far tweeter.

A big issue with installing the tweeters far back on the A pillar is that reflections off of the dash and windshield may interact resulting in cancellations because of comb filtering. I plan on laying down a dash cover (I'm thinking suede) to prevent the windshield-dash interactions.

Have any of you used a soft cover on the dash in order to prevent comb filtering when installing tweeters/midrange speakers up high?

Also, I'm going to be running the tweeters active, how low can the db tweeters be safely crossed at 24db/octave?

MacLeod

Reflections off the windshield wont be that big of a problem. I competed for several years with the tweeters in the corners of the dash firing up and didnt have a whole lot of issues. Granted I had a lot of processing power and when I aimed then on axis and in the A pillars, they got a lot more focused.

Thing is though, without time alignment and some solid EQ power, youre not really gonna have that great a stage to begin with. So I say mount them to where they can perform best tonally and let the stage fall where it may.

If they make a Dashmat for your car, they certainly help a lot. Look like total **** but make a huge difference in reflections and really take the bite out of your high end.

Id actually recommend getting them as high as you can. You want as many octaves as possible coming from as few a speakers as possible so you want your mids to be playing the bulk of the music. A good starting point and generally finishing point that Ive found in ever car Ive worked on is 4 KHz cutoff for both mids and tweets with a 24 db/oct slope.

pentoncm

I ended up getting the alpine CDA105 and imprint processor so I will have time alignment 5 band eq, and active setup.

They do make dashmat for my car, so I think i'm going to try it.

MacLeod

Since youll have time alignment and solid EQ power, I say you should definitely mount them in the A pillars above the highest point of the dash. This way youll get the uninterrupted sound from the tweeters cause no matter how much processing power youve got, you cant make up for a big piece of plastic dash in front of your tweeter.

arun1963

You need to mount the tweets above dash level, like Mac said. Also keep in mind that you "don't" want the near tweet too much on axis to you. If mounting them on the A pillar is going to bring the near tweet bang on axis, you will have your image smeared around it. You may be better off looking at mounting them deeper into the dash so that the near one is not bang on axis.

The frequencies that the tweets play are less affected by phase issues but are extremely sensitive to L/R intensity imbalance, based on how on/off axis they are. Even with seperate L/R eq you would still have an issue, without it you may struggle. Definately look at mounting them higher than dash level and the dash mat will help a lot.

I wouldn't run the tweets below 3-4khz, 24db slopes are good. If you're running a sub, try crossing the mid and sub around 50-63hz. I prefer steep slopes on everything. Gives a better focused image. When you run active turn the gains down on the tweets. The db tweets need some taming.

If you can post pic of the cars interior maybe that would help.

jay27

I'm playing around with tweeter placement myself.

When you guys say to mount the tweeter above the dash, I assume you're taking the steering wheel out of the picture? Does the steering wheel ever become an issue? When in the sail panels especially and pointing toward the opposite head rest, the tweeter tends to point straight into the steering wheel.

Also, with my tweeters in the sail panels, the driver's side tweeter is very pronounced. It's to the point where the image is essentially coming from the left tweeter, even causing ear fatigue in my left ear. Is there a certain frequency to tame, t/a to balance it out, or? What frequency tends to cause an overpowering driver's side tweeter?

pentoncm

Thats something that I'm afraid of putting the near tweeter in the A pillar in the position where it would be above the dash. Because of the slope of the pillar it is would be right next to the sail panel position. Granted playing with the angle could help some, it would be even closer to my ear than the sail panel would be.

I will take a picture of my dash so you guys can see what I'm talking about. The instrument panel wouldn't completely block my near tweeter if I put it at the close to the base of the A pillar. I could play with angling the tweeter slightly upwards so it would have a clearer path. Also, I'm planning on aiming at opposing headrest, so if the near tweeter is not as bright as the far (which has a more or less direct path), I could move the angle of the near tweeter a little closer to being on axis to try and get the image balanced.

Do any of you recommend using different crossover slopes or cutoff points on the left vs. right drivers? For instance, if the near tweeter doesn't seem to blend as well with the near woofer I could go with 12db/18/octave filters and then 24db/octave on the far side.

pentoncm

I found a picture of my dash online so you guys can see.

arun1963

pentoncm wrote: »

it would be even closer to my ear than the sail panel would be.

Don't worry about the distance, TA will cover that. Get the axis right.

pentoncm wrote: »

I could play with angling the tweeter slightly upwards so it would have a clearer path. Also, I'm planning on aiming at opposing headrest, so if the near tweeter is not as bright as the far (which has a more or less direct path), I could move the angle of the near tweeter a little closer to being on axis to try and get the image balanced.

I have my tweets mounted on the dash and angled like you're thinking. While this works fine and gives good stage height, mounting them in pillars would lessen the impact of reflection off the dash for sure.

pentoncm wrote: »

Do any of you recommend using different crossover slopes or cutoff points on the left vs. right drivers? For instance, if the near tweeter doesn't seem to blend as well with the near woofer I could go with 12db/18/octave filters and then 24db/octave on the far side.

No I don't. Its never worked, at least for me.

arun1963

pentoncm wrote: »

I found a picture of my dash online so you guys can see.

That dash is certainly less obtrusive than mine. Go with the pillars. I would play around with them in temp tape mount mode. Experiment a bit to figure out how high up the pillars and the best angles.

arun1963

jay27 wrote: »

When you guys say to mount the tweeter above the dash, I assume you're taking the steering wheel out of the picture?

Yes but that's a very minor gain. What's more important is that you're reducing the impact of reflections from your dash. With the tweets on the dash, the sound is reflecting off three major areas. The windscreen, pillars, and the dash. Since the dash is closest to you, is a huge area and affects both the mids and tweets, its impact on your sound is the highest. By moving the tweets higher, you're reducing the reflections of the dash by a bit. Not gone, but less.

Comb filtering (reflections) in a car is a given. Some things you can manage with tuning and some things like reflections are better managed by install and/or treatment eg the dash mat.

jay27 wrote: »

Also, with my tweeters in the sail panels, the driver's side tweeter is very pronounced. It's to the point where the image is essentially coming from the left tweeter, even causing ear fatigue in my left ear. Is there a certain frequency to tame, t/a to balance it out, or? What frequency tends to cause an overpowering driver's side tweeter?

The near side tweet is probably closest to you and hence you will hear that first. The brain locates sound by what it hears first. If the tweets are in sail panels then the near one almost 90deg off axis and the far one is on axis. Your upper mids and highs frequencies that the tweets play, are much stronger from the driver on axis. This smears the highs all the way to your side. Your brain is now locating the source at the near tweet and the the far tweet is adding intensity to the location. Time alignment and getting the tweets on better axis will help a ton.

jay27

arun1963 wrote: »

Yes but that's a very minor gain. What's more important is that you're reducing the impact of reflections from your dash. With the tweets on the dash, the sound is reflecting off three major areas. The windscreen, pillars, and the dash. Since the dash is closest to you, is a huge area and affects both the mids and tweets, its impact on your sound is the highest. By moving the tweets higher, you're reducing the reflections of the dash by a bit. Not gone, but less.

Comb filtering (reflections) in a car is a given. Some things you can manage with tuning and some things like reflections are better managed by install and/or treatment eg the dash mat.



The near side tweet is probably closest to you and hence you will hear that first. The brain locates sound by what it hears first. If the tweets are in sail panels then the near one almost 90deg off axis and the far one is on axis. Your upper mids and highs frequencies that the tweets play, are much stronger from the driver on axis. This smears the highs all the way to your side. Your brain is now locating the source at the near tweet and the the far tweet is adding intensity to the location. Time alignment and getting the tweets on better axis will help a ton.

My driver's side tweeter is probably more like 45 degrees because it's pointing toward the passenger headrest. The right tweeter is completely on axis.

So, would t/a alone solve this issue, or would eq be involved as well?

Would I use an spl measuring device and just try to level match the tweeters with an eq?

arun1963

You would need TA and tweets on better axis. Try aiming the tweets to point between the seats and about a foot or so in front of you.

A normal 5-7 band eq is good for balancing the sound, good tonality. If you can get an eq that gives you separate L/R control, then you can balance for L/R intensity as well. This will help a lot with imaging and improve the tonality further.

Getting an spl meter and a cd with sine waves is a good way to start. Eventually you'll have to do it by ear. Keep in mind that frequencies above~1khz are very prone to reflections so the reading may not be as reliable. But yes its a good way to start.

pentoncm

From my understanding TA will not have an effect on how highs sound except that it will fix crossover point issues. Example if two tweeters are out of phase you could get cancellation at the crossover point. How far apart is each driver from your ear? If the near tweeter is very close compared to the far one, angling can only do so much. There is a compromise by shifting the near tweet farther and farther off axis, your image will be pulled to the right, this can make your right side bright and the left side dull.

If you have the passive crossovers try attenuating the tweeters to see if that helps. If your near tweeter is significantly closer then you may want to move the near tweeter farther away. You could still play with the angle, making the near tweeter more off axis. Theoretically you should match any changes and adjust the far tweeter as well. What kind of eq do you have?

jay27

pentoncm wrote: »

From my understanding TA will not have an effect on how highs sound except that it will fix crossover point issues. Example if two tweeters are out of phase you could get cancellation at the crossover point. How far apart is each driver from your ear? If the near tweeter is very close compared to the far one, angling can only do so much. There is a compromise by shifting the near tweet farther and farther off axis, your image will be pulled to the right, this can make your right side bright and the left side dull.

If you have the passive crossovers try attenuating the tweeters to see if that helps. If your near tweeter is significantly closer then you may want to move the near tweeter farther away. You could still play with the angle, making the near tweeter more off axis. Theoretically you should match any changes and adjust the far tweeter as well. What kind of eq do you have?

I have an old school hx-d2 head unit. 5 band parametric, so I couldn't do a ton of adjustments. I'm thinking of getting an external processor or doing a carpc, but I'm not sure. Ironically, the carpc can be the cheaper choice.

The odd thing is that the more complicated your system is, the more equipment you need to get it to sound right. I find a simple coaxial with the passive crossover is the easiest way to get good sound. I barely touch the eq because the sound isn't nearly as offensive initially as having tweeters up high, mids low, etc.

Do any of you have your tweeters installed in different locations? For example, the right tweeter in the sail panel and the left tweeter further away in the a-pillar to try an minimize the path length differences? I'm not sure this would work, especially if the tweeters were not at the same height?

MacLeod

I dont worry about the steering wheel. Mount the tweeters about an inch above the highest point on the dash. You dont want them too high.

Time alignment will only sorta fix pathlength differences. It wont do anything for intensity and a tweeter closer to you that is on axis will be much louder then the opposite one. Thats why you dont want to aim it right at you. Firing across at the opposite head rest is almost always the best way.

Time alignment can change phase but not always. Swapping the polarity is the only sure fire way to change the phase. Looking at your dash, with the tweeters mounted above the highest spot on your dash and aiming towards the opposite head rest, I dont see you having a lot of problems with anything. It should work pretty well.

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arun1963

pentoncm wrote: »

From my understanding TA will not have an effect on how highs sound except that it will fix crossover point issues. Example if two tweeters are out of phase you could get cancellation at the crossover point. How far apart is each driver from your ear? If the near tweeter is very close compared to the far one, angling can only do so much. There is a compromise by shifting the near tweet farther and farther off axis, your image will be pulled to the right, this can make your right side bright and the left side dull.

If you have the passive crossovers try attenuating the tweeters to see if that helps. If your near tweeter is significantly closer then you may want to move the near tweeter farther away. You could still play with the angle, making the near tweeter more off axis. Theoretically you should match any changes and adjust the far tweeter as well. What kind of eq do you have?

There are two issues that are contributing to Jays problem. Arrival time of near tweet and intensity imbalance of L/R tweet due to the axis they ared mounted at. The TA would correct the arrival time of the near tweet so that you dont hear it first. Playing with the angles on the tweets would give you a more balanced axis response.

If the near tweet is too far on axis then the highs are going to be much brighter from this tweet, it will feel like the entire sound is concentrated here. If on the other hand the near tweet is off axis and the far one is on axis then the highs are going to be much brighter from the far side, but the effect will be the same. If like 3 octaves are almost beaming from the far side, the image is going to be smeared towards your near side.

If you put the mids and tweets on the same slope at the xover point, then the phase at the xover point is inverted yes. But, at the typical points where you would cut your tweet, your ears are not very sensitive to phase issues.

Having the near tweet say 20" from your ear will not be so much of an issue as long as you can manage arrival times and get the angles right. I think I mentioned attenuating tweets in my first post.

tk421

all the guys here are correct.

dont discount the use of the door. closer to the mid range.
dont rule out using the kick panels for both either. the deepest stage i ever had was when i placed them both there.

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arun1963

tk421 wrote: »

all the guys here are correct.

dont discount the use of the door. closer to the mid range.
dont rule out using the kick panels for both either. the deepest stage i ever had was when i placed them both there.

If you're going for the best in staging and imaging, you would not mount tweets below dash level. The typical tweet passive or active will be playing down to 2-3 khz with some degree of presence. The brain can locate 'higher' / 'lower' from about 2khz on. Hence you want driver physically up high.

Kicks are great for mids. The further away / deeper you can mount the mids, the deeper your stage depth, yes. But depth would come at the cost of width. If you mount your tweets down low (door or lower) the stage height will rainbow. Higher at the centre and down at your kicks at the edges.

If I could, I would mount mids in kicks and the tweets angled properly in the pillars.