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Bigrick31
02-20-2005, 03:13 PM
So i have heard from a few people that using multiple tweeters (in one door) dosnt sound very good. however the installs were all the same. one tweeter is on top of the other (or above) i am wondering if you have 2 tweeters and have them side by side and have them imaged so that they are firing at the same piont wil that sound better or worse than just running 1 tweeter? I ask because it seems like it would be easier to make a baffle for ym mids and tweets if i hade them paired together 2 mids and 2 tweets in each door. that seems easier than 2 mids 1 tweet and creating a baffle for that. any thoughts/opinions or words of wisdom from those who have experienced it would be greatly appretiated. also any one have a link for creating a baffle for some mid/tweet. (ill attempt to describe it) a circle with a triangle attached to the end.

Stangs400
02-20-2005, 05:14 PM
im also interested in this...im thinking more is better, but by the way it seems, thats not how it is! I guess it would make the tweeters a little over powering and drown out the mids, but then you could turn down the level on the tweeters say with a crossover, but then wouldnt that just make having a second tweeter useless??

Strecker25
02-20-2005, 05:17 PM
i would think if theyre aimed at the EXACt same point and receiving the exact same freq and power it would be ok, but if theyre off be even the least bit i would think u would have a type of "double soundstage" dilemma. Overall id stick with the standard 1 per side

johnecon2001
02-20-2005, 06:32 PM
^^ its called "Comb Filtering". Where you get two of the same drivers shooting in somewhat of the same direction shooting the same type of music.. you get things that cancle each other out. So in this case Less Is More. And More is definetly Less.

squeak9798
02-20-2005, 06:38 PM
So in this case Less Is More. And More is definetly Less.


x2

You'll run into major cancellation and phasing issues.

Strecker25
02-20-2005, 06:48 PM
^^ its called "Comb Filtering"..

i knew one of you would know the technical term, now i know this is o/t but any relevance to a tv's digital comb filter?

Bigrick31
02-20-2005, 11:02 PM
so it look like ill have to make 1 baffle on each door with 2 mids and 1 tweet in each door. any one have a link to a tutorial on how to do it.

Bigrick31
02-21-2005, 02:10 PM
isnt the rule of thumb that the tweeter should be no more then the radius of the mid away form the mid? so in my case idealey i owuld want to put my tweeter 3.25" away from both mids

squeak9798
02-21-2005, 03:23 PM
isnt the rule of thumb that the tweeter should be no more then the radius of the mid away form the mid? so in my case idealey i owuld want to put my tweeter 3.25" away from both mids


That's a general rule of thumb....yeah. Not the 11th commandment though

JAZN
02-21-2005, 03:39 PM
That's a general rule of thumb....yeah. Not the 11th commandment though

i thot u werent religious :p:

squeak9798
02-21-2005, 03:57 PM
i thot u werent religious :p:

I'm not.........but the analogy/metaphor (whatever it is) works good in getting the point across :D

geolemon
02-21-2005, 04:11 PM
^^ its called "Comb Filtering". Where you get two of the same drivers shooting in somewhat of the same direction shooting the same type of music.. you get things that cancle each other out. So in this case Less Is More. And More is definetly Less.

Very true - usually!

I wrote this up a while back, to try to put the issues into laymen's terms:
www.betteraudio.com/geolemon/phasing/phasing.htm

...and I think that article will help the original poster actually understand the issues at hand, so he can make up his own mind if a particular tweeter location will work out or not.

(note: the same issues hold true for phase differences between tweeter and mid - and the greater the pathlength difference between them, the more phasing issues you experience at your crossover point as well - it's not necessarily just like-frequency drivers. ;))


Now, I say "usually", because I did some experimentation to back up that research... it's not really exactly accurate to make a generalization like "more is less"... because theoretically you should be able to mitigate the issues, by being able to implement multiple drivers that have exactly the same pathlength distances to your head, and not suffer any adverse effects...
...in fact, you could see some benefits from it - that was what I wanted to play with here:
www.betteraudio.com/geolemon/Linesource/Linesource.htm

It worked pretty well - and that might be exactly what this thread is about:
"How do I implement multiple tweeters and/or multiple mids without creating [or at least minimizing] comb filtering effects?"

It worked well enough that I'm working with my new winter-beater (a Nissan Pathfinder... pretty similar), implementing a new array design - this time with three full-range drivers per door (with phase plugs, they extend from 250hz all the way up to 20,000hz - off axis! :eek: ), and two midbass drivers per door.
I haven't finished it yet, but I'm getting there.

...it's also going to be implementing an adjustable ported enclosure (that can be sealed also), and everything running through a custom-built passive crossover (in part to contend with some narrow-band filtering issues with regard to the midbass drivers), to run 11 speakers off one big 2-channel amplifier...
...mostly just to bust some other way-overgeneralized paradigms for fun too. :p

geolemon
02-21-2005, 04:16 PM
isnt the rule of thumb that the tweeter should be no more then the radius of the mid away form the mid? so in my case idealey i owuld want to put my tweeter 3.25" away from both mids
That's the point...
This generalization works, but you'll see the issue is more closely related to keeping the pathlength distance from your head to the tweet as equal as possible to the pathlength distance from your head to the mid... as opposed to "keeping the tweeter near the mid" - although there are other unique acoustical issues, such as having one driver or another near glass, or a big void, or a panel reflecting sound in a particular direction, that can help keeping the two drivers essentially in the same location...
...but sometimes, you can take advantage of those very things as well.

My bottom line is this:
Don't EVER arbitrarily choose a tweeter location, drill and mount. :eek:

Stick the tweeter in the surface-mount base, cut some extra long wire to temporarily run the tweeters on, and break out some double-sided foam tape.
Try the tweeter out in several locations.
Let your ears decide the best location.
Close your eyes and listen.

Parked, of course. :D

Bigrick31
02-21-2005, 04:44 PM
Wow very good reading there. that helped out a lot. now wouldnt you experience the same thing running 2 mids (per door) up front. they will be slightly out of phase because they are (although very close together) in 2 seperate locations and the pathlength distance will differ. I see that you are working on a simular setup. how do you fix this issue or can you 100%

Bigrick31
02-21-2005, 06:37 PM
so is what i am thinking right? should i ditch 1 set of xxx mids and just put one set in a kick cutom kick pannel?

Bigrick31
02-21-2005, 09:12 PM
bump

geolemon
02-21-2005, 09:31 PM
Wow very good reading there. that helped out a lot. now wouldnt you experience the same thing running 2 mids (per door) up front. they will be slightly out of phase because they are (although very close together) in 2 seperate locations and the pathlength distance will differ. I see that you are working on a simular setup. how do you fix this issue or can you 100%
You will experience the same thing...
But not nearly to the same degree.

With my new installl, the speakers playing 250hz up to 20,000hz are installed in the most ideal location - as far forward as possible.
The midbass drivers are still installed in a "line" with each other, but farther back... less ideal. But, less acoustically impactful, not only because they are playing such a narrow bandwidth, but because of a few other factors:
1) the lower you go, the less you are capable of locating the source of sound
2) the lower you go, the less you are capable of perceiving distortions and even details

Remember, the lower you go in frequency, the longer the wavelengths of those frequencies.
One 20hz cycle is 1/20th of a second.
One 20,000hz cycle is 1/20,000th of a second.

So - the higher you go in frequency, the smaller the difference in pathlength distance needs to be before you begin causing phasing anomolies (cancellation/combination nodes - "comb filtering")

And, conversely - the lower you go in frequency, the greater the difference in pathlength must be before you cause any phasing anomolies.



If you are looking for big midbass - first off, more speakers might not be the answer.
If you have them in your doors, and your doors haven't been prepped at all (stock doors are far from good enclosures - they have big holes in the inner structure behind that plastic door panel! :eek: ) - you ARE getting cancellations down at low frequencies, because the sound energy from the rear of the speaker can leak right around and cancel the speaker out...
...if you add another midbass, you'll just have two speakers with cancellation issues. ;)

First thing that I'd do is take that door apart, and use damping material on the outer skin, and two (maybe more) layers on the inner skin - cover all those holes right up - make it a better enclosure. That's usually enough. ;)

After doing that - I'd bet you won't wish for another set of speakers.

Bigrick31
02-22-2005, 12:55 AM
i already have my door covered in deadoner and was planngin on fiberglassing a small ported enclosure into my door pannel. so even in this case 1 mid will probably do? also would it be better for me to make a kick pannel or will a door location sound just as good if done properly?

Bigrick31
02-22-2005, 06:51 PM
bump

geolemon
02-27-2005, 10:54 PM
I think the biggest challenge would be fitting two speakers into the kicks - to say nothing of adding the tweeters as well.
I'd bet you will be forced to the door location.
I can tell you from experience - if you pathlength-align them like I did, it works out very well.