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Old 10th October 2009, 03:29 AM   #1
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Default OB or sealed?

This is my first home speaker project.

I would like to build a speaker system based on the JBL E145 and PR170M0s.

#1- I have read most of the work regarding open baffle PR170MO’s here and on ‘High Efficiency Speaker Asylum’. Specifically I would like to replicate the work that Magnetar did regarding the twin OB PR17OMO’s. I believe the last generation had the APT80’s and rear firing Leson TCL1. It seems that the Leson was modified, but how I am exactly not sure. But I thought that I read that he also tried a Beyma CP21's and thought they sounded great. I read that at one point the construction of these speakers was on his web page, but when I did find the link I was unable to open it. It was probably an old link. Does anyone know where I could acquire the specific information regarding his build?

#2- Using the E145, 2123, PR170M0 and horn tweeters. All first order crossovers.

What do you guys think? If I go with choice #1, I need to buy 2 PR170M0 and tweeter. If I go with choice #2, I only need to buy tweeters. The speaker location will be my entertainment center. These will be used for music and some HT.

The E145's will be ported and I have a seperate sub.

Last edited by mitchyz250f; 10th October 2009 at 03:32 AM.
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Old 10th October 2009, 03:41 AM   #2
cuibono is offline cuibono  United States
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I have a clear preference for OB speakers - but the only way to know what you prefer is by trying both...

I might add though, that you might want to think more about 'how' you're going to do this, whatever path you take. IOW, if you're not doing any measurements, you're flying blind. It is much easier to copy someones design - they've done a lot of the work for you. But if you want to go your own way and you can't take frequency response measurements, its likely you won't be satisfied (at least for long), and you won't know why not. Just my two cents...
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Old 10th October 2009, 03:58 AM   #3
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Thanks for your response. I have a very good friend who is an EE and getting in audio. We will be doing this project together. He has the equipment to take readings, but I still think my best start would be to copy someone elses design first.

How critical is placement of the OB speakers compared to sealed box?
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Old 10th October 2009, 04:49 AM   #4
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IMO placement is easier. Just keep them out from the rear walls.
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Old 10th October 2009, 04:53 AM   #5
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Just to be clear I now have 2 JBL e145's, 2 Audax PR170M0's, and 2 JBL 2123's and a Tempest sub.
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Old 10th October 2009, 05:43 AM   #6
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#2- Using the E145, 2123, PR170M0 and horn tweeters. All first order crossovers
6dB is not recommend if you use a PR170. See Audax application note 600Hz@18dB :

also see JBL 2123 : http://www.jblpro.com/pub/obsolete/2123.pdf

JBL E145 : http://www.jblproservice.com/pdf/Dis.../E145-8-16.pdf

Note : OB is not so easy to have a smooth response, the panel should be at least for the PR170 30cm (11.8 inch) width if you want to go as low as 600Hz. It is your first project, I recommend a closed box or better an aperiodic box.

Last edited by jerome69; 10th October 2009 at 06:01 AM.
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Old 10th October 2009, 12:17 PM   #7
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Thanks Jerome. I was thinking first order for the 4 way with crossovers at 300, 1000 and 5-6k.
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