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Old 13th December 2009, 08:08 PM   #1
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Default MJK OB over H-Frame finished

Greetings!

I have finished putting a Fostex FE103E on an open baffle over an Eminence Alpha 15 in an H-frame (both on the same baffle). This is based on Martin King's papers "Designing a Passive Two Way Open Baffle Speaker System" and "Comparison of the Bass Performance of Passive Open Baffle, U
Frame, and H Frame Speakers" that I found online.

My Polk Monitor 7's that I bought back in college were starting to make noise on hard hits, looking at how expensive a good pair of new speakers would be I decided it would be better to rebuild. I didn't want to be stuck w/o anything besides my iMac to listen to music with, so I decided to try my hand at building a pair of speakers that would be a good keep once the Polk's were done. That's when I discovered MJK's papers/this and a few other forums as well. The internet is so cool (it's like a series of tubes).

This is my first speaker build and I am very pleased. With all the writing about how Fostex drivers need time to break in, I half expected these to sound horrible, but they are very acceptable right out of the box. I can only imagine what is in store for the future of these as they get more hours on them. I don't have any measurement equipment outside of my MkI E.A.R.S., so I can only say "They sound good to me!" They may not sound as nice as a pair of Dynaudio BM6A MkII speakers, but I wouldn't expect something built on my back patio to be in that league (plus OB is completely different from Near-field).

I was up way too late last night listening to different CD tracks from my library- mostly classical and rock- as well as the Jazz Traditions channel on my dish receiver. They sound fine on everything I threw at them. They sound best with recordings from the concert halls where I work.

My thanks to MJK for putting something so do-able online for a beginner to get started! Now I just have to decide how to approach rebuilding those Polks!

cordially,
Graf
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Old 13th December 2009, 08:22 PM   #2
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I tried to upload some pic's, but after 10 minutes of waiting for the upload to happen I gave up. Maybe the "tubes" are full right now. I'll try again later.
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Old 13th December 2009, 08:49 PM   #3
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Congrats on your new speakers. I'm on the verge of building the same open baffle project myself. I already have the eminence woofers so I'm part-way there. Did you change the crossover values since you put the woofer in an h-baffle?

Are you listening to classical on them?
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Old 13th December 2009, 10:14 PM   #4
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Hello Graf - and Welcome to diyAudio!!!

Congrats on your build and fer-sure we wanna see some pic's!! Plus all the info about cross-overs, cryo treated - silver plated - solid core - silk insulated hook-up wire etc

You work in a performing arts center so ya know what the real deal is in terms of "sounds good" - and thus we do await your listening impressions.

My Fostex 167's did need a couple of hundred hours break in before they started sounding right (subjective term) and I'm pretty sure that you will find yours sounding better after a bit of "burn-in" is put on 'em.

There are treatments and tweaks for 'em - see BudP's EnABLE thread if you are daring - and have a steady hand. David D aka "Planet10" has many tricks to make 'em clean up as well.

It's good to see another Southern lad here with us! We keep trying to get enough of us around to start up some meets every now-and-again - there was one near Atlanta GA awhile back but I couldn't make that one - maybe next time.

As far as the "uploads" go -the site is switching over to a new server at the moment and there might be some glitches there - also notice that there are size limits on what you can upload and if you exceed those limits the server will bounce you out.
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Last edited by c2cthomas; 13th December 2009 at 10:21 PM.
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Old 14th December 2009, 01:49 AM   #5
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Default pic's and stuff

Thanks for the congrats and welcome! Well, I couldn't get any pic's to load up here on the second try so I loaded them up at Imhoof Studios on MySpace.

The cross-over is the only hiccup. I ordered the parts listed in MJK's first paper before I found the second on H-frames (oops). However, I don't think I'm that far off. I'll be able to make an informed decision once these break in and I borrow a real RTA from work. Right now I've only got the free iPhone app and my ears, but I don't see (or hear) any real problems. Since the cross-over is in the open on the back, it won't be a big deal to change if necessary. No fancy wires. Just the cheap Radio Shack 16ga speaker wire throughout.

I'm driving these with an Onkyo TX-8222 stereo receiver fed from a Sony DVD player or from my dish receiver. I work in a place with two concert halls that have world class acoustics so I'm not even going to try to compete with that in my living room.

These speakers sound really good with less than a dozen hours on them. So far, the only thing I can criticize is the "tightness" of the sound. As I listen to recordings made in our concert halls I can here every note, but not the halls themselves. A recording of Sasha Cooke (mezzo-soprano) w/ Pei-Yao Wang (piano) in our recital hall sounds wonderful- every note/syllable/vowel is right on, but once it's done I don't hear that characteristic hall sound that I'm used to. Same problem when I listen to a recording of the Helsingborg Symphony Orchestra playing in our big hall. Everything is there but the after effect. I can always tell when our halls are played on PERFORMANCE TODAY, but with these speakers I just don't have that. I think that once these things get more hours and relax, I think that will resolve itself.

When I say everything is there, I mean the balance of these is very realistic. I know a lot of people have stated that these need more bass, but I hear the same amount of base out of these that comes off a stage. I wouldn't recommend these for Home Theatre, but that's not what they're made for. I like this design because it lends itself really well to acoustic music. This makes them a really good pair of speakers for over 50% of what I listen to- concert recordings. Once these are broken in and I decide what tweaks I want to commit to, I see many, many smiles in my future. Especially when I remind myself of how much money I spent on these things- WITH costs for tools I don't think I spent $600.

Please let me know if there is a problem finding the pic's at Imhoof Studios.

Cordially,
Graf
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Old 14th December 2009, 02:12 AM   #6
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Quote:
Originally Posted by gvimhoof View Post
Please let me know if there is a problem finding the pic's at Imhoof Studios.
A URL would be hekpful

dave
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Old 14th December 2009, 02:53 AM   #7
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Quote:
Originally Posted by planet10 View Post
A URL would be hekpful

dave
Imhoof Studios's speakers Photo Album - MySpace Photos

Nice combo - OB + H frame.
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Old 14th December 2009, 06:17 AM   #8
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Those certainly look cool!

Congratulations,

Dan
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Old 15th December 2009, 12:22 AM   #9
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oops. Earlier post should read less than $600 WITHOUT tools. Thinking it through, I'm not sure I broke $550. Obviously not the least expensive build in history, but I'm happy with this result. I would never spend the money, but I would really like to hear what those Jamo 907's sound like in a synergetic system.

Thanks for putting that link up, c2cthomas! I grew up a Hoosier, but I've spent the last few years here in GA and before this I lived in Houston, TX. I just keep going where the career takes me. I think I would enjoy one of those DIY meets. Have to be in the summer. I'm silly busy during the school year.
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Old 15th December 2009, 01:17 AM   #10
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Quote:
Originally Posted by gvimhoof View Post
oops. Earlier post should read less than $600 WITHOUT tools. Thinking it through, I'm not sure I broke $550. Obviously not the least expensive build in history, but I'm happy with this result. I would never spend the money, but I would really like to hear what those Jamo 907's sound like in a synergetic system.

Thanks for putting that link up, c2cthomas! I grew up a Hoosier, but I've spent the last few years here in GA and before this I lived in Houston, TX. I just keep going where the career takes me. I think I would enjoy one of those DIY meets. Have to be in the summer. I'm silly busy during the school year.
1) Now ya have some tools for the next project!!
2) Spending $$$$ on sawdust therapy - pricless
3) Happy with the result - For a 1st try out of the blocks = Grrrreat!

My Uncle "Buddy" was an engineer for NASA down Houston way + an A&M Alumni. Mom and Sis were born in Wichita Falls and Brother in Amarillo. I love Austin Tx and would live there except that I married a Nashville TN Gal and she drug me from Sacramento Ca to where we now live near Nashville. I have lived in many places and find that I have enjoyed returning to the "South". Here in middle Tennessee it's not to hot - or to cold - or to crazy!

How's the speaker break in period going? You can speed things up by putting on some AC/DC or Kiss at high volume levels - but somehow I doubt that would be up your alley
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Last edited by c2cthomas; 15th December 2009 at 01:21 AM.
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