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JP2.0 Project Part 3 A.K.A PR170s sound amazing.. And a few questions!
JP2.0 Project Part 3 A.K.A PR170s sound amazing.. And a few questions!
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Old 4th April 2005, 05:32 PM   #1
DIY_newbie is offline DIY_newbie  United States
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Talking JP2.0 Project Part 3 A.K.A PR170s sound amazing.. And a few questions!

I just wanted to take a moment to thank everyone who has contributed advice to my project so far. I've been really busy with school so I haven't had as much time to devote to speaker building as I would like

I finally decided on using the Audax PR170m0 midrange with the fountek ribbon. The PR170's arrived last week. I couldn't wait to hear them so I mounted in some temporary carboard baffles 18"x42" with nothing more than some screws from home depot. I'm running them widerange without a cross over and they sound great! I'm suprised at how high these drivers can play. I was worried since the FR plot looked like it had some serious cone breakup above 2.5K and I tought they might sound harsh without any filtering.

Overall the vocals are amazing! I spent the week listening to Diana Krall, Eric Clapton, Sting, Brian Adams. If the rest of my drivers sound this good I'm never going to remove the grin from my face I'm not sure if its the open baffle/dipole or the speaker itself but the sound is effortless and just draws me into the music.

Right now the PR170s are mounted in the center of the baffle. I've been playing around with the Baffle Diffraction Excel spreadsheet and think I've come up with a more optimal placement. This week I would like to mount the Fountek and the PR170 on a cardbooard baffle and start playing with the crossover between the two.

I had a couple of questions for the experts out there.

1) Offsetting the midrange to the side and placing it at the top of the baffle seams to give me the best response is this normal? What sort of placements have other people used?

2) Is it ok to place the midrange above the tweeter?

3) I need some sort of bass drivers that will maintain the same feel as the PR170. I was thinking an H-baffle dipole woofer? Maybe a critically damped sealed box? Any suggestions on a good bass setup to match the sound/feel of the ribbon/pr170?

--- Here is the layout I was thinking about :

Click the image to open in full size.

Thanks,

--Chris
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Old 4th April 2005, 10:10 PM   #2
Saurav is offline Saurav
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I used that spreadsheet to try baffle placement options for my speakers too. I ended up with the PR170M0 and JP-3.0 aligned vertically, tweeter on top, with both of them offset about 1" from the center of the baffle. Of course, my baffle dimensions are different from yours, your simulated output from the PR170M0 is much smoother than what mine looked like when I tried it that close to the edge.
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Old 5th April 2005, 03:32 AM   #3
DIY_newbie is offline DIY_newbie  United States
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Quote:
Originally posted by Saurav
I used that spreadsheet to try baffle placement options for my speakers too. I ended up with the PR170M0 and JP-3.0 aligned vertically, tweeter on top, with both of them offset about 1" from the center of the baffle. Of course, my baffle dimensions are different from yours, your simulated output from the PR170M0 is much smoother than what mine looked like when I tried it that close to the edge.
Saurav,

I was actually suprised how smooth the PRs response was according to the simulation. I still don't like how jagged the Fountek's response is being predicted. Can you post the dimensions and speaker positions on your baffle? Are you using any EQ? I'm hoping some of the baffle experts will chime in and give me some ideas, otherwise I'll just keep moving things around and see what seems to work best..

I'll take some pictures of the cardboard baffles and post them this week

--Chris
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Old 5th April 2005, 05:33 AM   #4
Saurav is offline Saurav
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No EQ, I'll play with that and the XO once I've moved to my new place. I picked a 14" wide baffle because my lower bass enclosure is 14" wide. The baffle is 19" tall, and driver centers are 6" and 13" from the bottom edge. These dimensions do not include the lower enclosure, which is 14"x24". No one could really tell me if I should include that or not. I also put some wings on the sides that aren't visible in this photo.

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Old 5th April 2005, 06:29 AM   #5
jdybnis is offline jdybnis  United States
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I'm not an expert but...

Try puting the fountek on a non-rectangular baffle. I think the response will smooth out.
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Old 5th April 2005, 08:46 PM   #6
DIY_newbie is offline DIY_newbie  United States
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Quote:
Originally posted by jdybnis
I'm not an expert but...

Try puting the fountek on a non-rectangular baffle. I think the response will smooth out.
Thanks for the great suggestion.. I started modeling the baffle with a triangular peak at the top raised about 5" and placing the ribbon within this triangular section. This seems to help A LOT !!

However Now I'm having a hard time trying to get the PR170's response to look nice and smooth, it always seems to end up with a sharp dip (~2db) at 1Khz. I'll post some more graphs when tonight after I play with it some more...

I can improve the response by moving the PR170 further away from the Fountek Tweeter. Is this a good idea? I thought you wanted to keep the midrange and tweeter as close together as possible??

Any other suggestions??

Thanks in advance,

--Chris
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Old 5th April 2005, 08:50 PM   #7
tiroth is offline tiroth  United States
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It might improve the individual driver response, but you'll likely have progressively worse lobing issues the farther apart your mid and tweet are.
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Old 5th April 2005, 09:03 PM   #8
pinkmouse is offline pinkmouse  Europe
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JP2.0 Project Part 3 A.K.A PR170s sound amazing.. And a few questions!
Doesn't the PR170M0 have a little bit of a peak at 1K anyway?
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Old 5th April 2005, 09:38 PM   #9
DIY_newbie is offline DIY_newbie  United States
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Quote:
Originally posted by tiroth
It might improve the individual driver response, but you'll likely have progressively worse lobing issues the farther apart your mid and tweet are.
Thats what I suspected However how do you calculate the spacing for a ribbon tweeter and a cone midrange? Do you use the vertical center of the ribbon to the center of the midrange cone?

I understand that ribbons have a very wide horizontal dispersion pattern and a very narrow vertical pattern. Doesn't that imply that offsetting the midrange to the side would be a good solution? This seems to smooth out the frequency response quite a bit.

How much offsett is too much? Moving the midrange 2" to the right allows me to raise it up about 0.5" until it touches the tweeter again.. Is this a good idea, or should I try to keep them vertically alligned and play with the baffle some more?

Quote:
Originally posted by pinkmouse
Doesn't the PR170M0 have a little bit of a peak at 1K anyway?
From Audax's FR plots it looks like there is a slight rise around ~1.7Khz.. I'm not sure if I can trust those, I already purchased a behringer ECM-8000 and UB802 (for the mic preamp) so I can do real FR measurements. I just need to order parts to build the Wallin-Jig and I'll be all set

--Chris
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Old 5th April 2005, 10:02 PM   #10
pinkmouse is offline pinkmouse  Europe
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JP2.0 Project Part 3 A.K.A PR170s sound amazing.. And a few questions!
Hmm, maybe I was thinking of the Z0...Or maybe my memory is shot!

It's a good idea to get your measurement setup going, you can simulate for days, but nothing is quite like the real thing in a real room. To be honest, you may not even hear a 2db dip if it's fairly gentle, and if it's a problem, an active eq might be the simplest way of getting around it.
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