Where i should put the tweeter?

ramiro77

Member
2010-06-07 3:09 am
Hi everyone!
I´ve ordered a pair of Peerless HDS 830875 and a pair of Seas H1189 tweeters.
I´m going to build a pair of bookshelfs, but i don´t know how i can calculate the distance between the midwoofer to the tweeter, and the distance between the tweeter to the side walls of the cabinet.
Basically the cabinet will be builded with curved walls and curved edges to avoid the baffle step.
Hope someone can help me.
 
The tweeter should be as close to the mid-woofer as possible;

re: 'curved walls and curved edges to avoid the baffle step' - you're confusing baffle step with baffle diffraction, curved edges & walls will not avoid baffle step.

(Fortunately, baffle step isn't important in most bookshelf designs - but this depends on how you want to use them)

Diffraction from baffle edges
 
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Re " Where i should put the tweeter?"

Oh, sooooo tempting to give an anatomical answer :D

But yes, as close as possible to the woofer to reduce lobing at the crossover transition. Then for baffle diffraction, off-center if possible (but not too much as it tilts the off-axis response). Flushing in the woofer and tweeter also eliminates one more set of tiny reflections.
 

nickf

Member
2005-09-04 9:54 am
Tweeter location

As others have noted, as close to the woofer as possible so that the sound pressure at crossover frequency from both drivers combines.

Next, place it different distances from every edge. The last time I tried to figure some optimal distances I placed the center of the tweeter 35% of the way across the cabinet horizontally and the distance from the top of the cabinet to the center of the tweeter was 45% of the width of the cabinet.

Hope this makes some sense...
 
As others have noted, as close to the woofer as possible so that the sound pressure at crossover frequency from both drivers combines.

Next, place it different distances from every edge. The last time I tried to figure some optimal distances I placed the center of the tweeter 35% of the way across the cabinet horizontally and the distance from the top of the cabinet to the center of the tweeter was 45% of the width of the cabinet.

Hope this makes some sense...

Maybe this helps?
Tweeter diffraction

Regards -j
 

ramiro77

Member
2010-06-07 3:09 am
Yes jrenkin, i´ve heard about tweeter diffraction and flush mounting.
I´ve heard too that the best proportion to put the tweeter is a ratio of 1.6 (known as golden number).
Casually, putting the tweeter at 35 percent of width, you are respecting the golden number (aproximately).
I will put the tweeter in that proportion, and midwoofer horizontally centered, closest possible to the tweeter.
What do all of you think?
 

ramiro77

Member
2010-06-07 3:09 am
Well, i´ve been working with different driver´s positions according to suggestions and measurements, and i´ve found that this is the best:

[IMGDEAD]http://img833.imageshack.us/img833/3484/img00061201011042025.jpg[/IMGDEAD]

The tweeter is off center. The woofer is placed in that position to take advantage of its truncated part, and thus bring it closer to the tweeter.
I know that it´s not the most aesthetic position, but according to measurements is the best.
What do you think about?
 

ramiro77

Member
2010-06-07 3:09 am
Well, interesting!
At least there is one person who likes my design :)
Anyway, still do not know if I will use this alignment. Probably i will place the woofer without twisting, probably i will leave it as in the sketch. I have still about ten days until the speakers arrive to my country, and five more days until they arrive at my house. so I have time to decide.

Meanwhile, I'll tell you that the baffle will have curved walls. The construction method I use is to do a lot of ribs, which have the external shape of the baffle. then glue a rib on the other, and that's it. is a much simpler method Than bend mdf.
 
Modeling tweeter location and frequency response

I can also highly recommend Jeff Bagby's Baffle Diffraction and Boundary Simulator, which can model the baffle diffraction and in-room response effects for a single driver (at a time). It is free software that runs in Excel. Find it here:
Loudspeaker Design Software

You can find other useful speaker modeling software at my web site:
software

-Charlie
 

mashypie

Member
2010-11-03 10:37 pm
I really like it too, are you doing them as mirror images of each other?

I was looking to use Peerless in the future to make use of the chopped edges but to make a really slim cabinet, as most designs I've seen use them horizontally but I really like what you've done there, I think it will look really smart
 

ramiro77

Member
2010-06-07 3:09 am
@charlielaub: Thanks for the info. Very usefull.

@mashypie: Thanks!. I will build it as mirrors of each other. I think that is a smart design, i´m taking all the advantages of each driver. I really don´t care a lot if it´s a good looking design, i prefer good sounding. But i think that it will be attractive.
 
Sorry, but I think it looks cluttered to not line up the truncated edges with the long sides of the cabinet.
 

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Yes, i know. I would like to put the woofer in that way, but i think that it gets too away from tweeter. Do you think that putting woofer in that way will not make any difference?
Interesting that, after reading this thread for the first time, no one mentions the xover frequency. So, Tosh might be right after all, if the frequency is not very high and (in)adequate.