6.5" open baffle speakers - AVS Forum
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post #1 of 8 Old 02-19-2007, 04:32 PM - Thread Starter
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Here is a set of speakers I built, mostly as a learning experience. My design criteria were;

a) Get an F3 around 100 Hz in open baffle arrangement.
b) Make it no taller then 12" and cool looking for high WAF.
c) Practice using my router.
d) Practice designing and building a crossover (1st time).
e) Practice soldering (never been good at it).

Starting out I had zero experience with open baffle speakers or building crossovers. I had gotten some tips on both from both this forum and others. From what info I gathered I picked the Pyle 6.5" PA speakers as my woofers and the Hi-Vi TN28 tweeters (mainly because they would look cool).

Pictures of my results are included. They sound good, very detailed and with a huge soundstage. They do a great job of filling the whole house with sound. There are a few issues remaining though.

1) The rolloff around 79 Hz is as modeled, but there is another more shallow rolloff that goes from 120 Hz to almost 700 Hz. Some folks I communicated with think the 10" baffles aren't big enough. I know the problem isn't in the crossover - I have tested the speakers without the crossover to verify.

2) From about 13kHz to 20kHz the tweeter gets a steady rise in output. I have read that a R-L contour circut might fix this. I'm still waiting on a resistor I ordered to cut the tweeter down some before I try this.


To address #1 I'm going to order a set of these or these. They are cheap, model well and will fit the existing holes I drilled for the Pyle driver. I'll test these to see if there is any difference. If anything, it will be fun to test and will reduce the possibilities of things that could be causing the problem.
LL
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post #2 of 8 Old 02-19-2007, 07:45 PM
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You may want to try posting on diyaudio.com
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post #3 of 8 Old 02-19-2007, 07:53 PM
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Issue #1: Get a scrap large piece of wood and cut out a hole that is less than 10" diameter,
but greater than the midrange diameter. Place the wood in front of your speaker and
redo the midrange measurements [ignore the tweeter for now].



The storm was gone, but dark clouds still hung around
The perfect setting for things to come......

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post #4 of 8 Old 02-19-2007, 08:37 PM - Thread Starter
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After doing some more reading, I think it is baffle step diffraction that is causing my problems. I'll do more research into how to combat this, if possible (without making a huge baffle).
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post #5 of 8 Old 02-20-2007, 03:54 AM
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From the little experience I have so far round baffles like that cause the worst baffle diffraction. Have you measured the FR of that speaker? Show a pic if you have.

Also a CR shunt will contour that tweeter response.
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post #6 of 8 Old 02-21-2007, 11:47 AM - Thread Starter
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Quote:
Originally Posted by augerpro View Post

From the little experience I have so far round baffles like that cause the worst baffle diffraction. Have you measured the FR of that speaker? Show a pic if you have.

I'm getting that! I did measure the FR of the woofer by itself. I don't have the plot with me here but it has the same response (so the problem probably isn't the crossover). I did some research into baffle step diffraction and the step I'm getting fits the "theroetical" step almost perfectly. I'm pretty sure that is my problem.

This can be fixed with a shelf filter, but that will cut the sensitivity of the speakers by 6dB over the non-stepper portion. Since I don't want to do that I'm going to build auxiliary speakers just for that step region and see how they work. The crossover for that (and the original speakers) is shown in the attached picture. I wasn't sure if I could pull out the mid-range's high-pass filter and put it where I did - I'd appreciate if someone else could verify this.

Quote:
Originally Posted by augerpro View Post

Also a CR shunt will contour that tweeter response.

That's what I have read. In my design there should be a 3 ohm resistor to cut down the tweeter. Sadly, the resistor I ordered got back ordered so I don't have it now. When it comes in, I will test it out. If the tweeter still has too much rise then I'll do a R-C contour.
LL
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post #7 of 8 Old 02-21-2007, 11:36 PM
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That circuit doesn't make any sense to me.
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post #8 of 8 Old 02-22-2007, 05:00 AM - Thread Starter
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Quote:
Originally Posted by augerpro View Post

That circuit doesn't make any sense to me.

Well, the part inside the box in the upper left is the original crossover which, other then the diffraction problems, works just fine. It's just a second order high-pas and a second order low-pass.

The rest is for an auxiliary speaker that will (hopefully) turn the 2-way speaker into a 3-way and boost the frequencies where I'm having diffraction problems. It is just a first order highpass and lowpass. I added an L-pad to it so I can fine tune the response.

My question is in a traditional 3-way design the highpass for the mid-range is usually in the same parallel branch as the mid-range itself. Because I don't want to muck with the original crossover I want to move it in the path of the tweeter and the mid-range. Will this work?
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