Looking good, Jim - almost enough to shame me into building our long postponed OBs. I'm very interested in how the FF85K works in this application - it's certainly an eye-opener in the others I've tried so far.
Well, maybe after the patio pavers and landscape block wall are finished before the rain starts:
"honey, you know what else would look nice, and since we're so toned and limber from moving those 10 tons of gravel, sand and bricks, why not now?"
gotta luv her
Well, maybe after the patio pavers and landscape block wall are finished before the rain starts:
"honey, you know what else would look nice, and since we're so toned and limber from moving those 10 tons of gravel, sand and bricks, why not now?"
gotta luv her
Well, maybe after the patio pavers and landscape block wall are finished before the rain starts:
"honey, you know what else would look nice, and since we're so toned and limber from moving those 10 tons of gravel, sand and bricks, why not now?"
gotta luv her
Hey, my wife would never let me even think about trying to move 10 tons of gravel! She's trying to conserve me... hoping I'll last 'til our 50th anniversary; and I'm doing my best to cooperate.
And thanks guys!
Hi Jim - Great Job!
Very interested about your end results and impressions as I have been considering something similar but adding my old pair of ESS AMT1's to the top end. It will wind up resembling Stig Erik's Bema 150 thread http://www.diyaudio.com/forums/showthread.php?t=142015
Si what I'm up to is Ess AMT1 top - FF85K mids - Alpha (maybe Beta) 15 inch on the low end - Bi Amp powered - passive x'over. BTW - what are you doing for your crossover?
Very interested about your end results and impressions as I have been considering something similar but adding my old pair of ESS AMT1's to the top end. It will wind up resembling Stig Erik's Bema 150 thread http://www.diyaudio.com/forums/showthread.php?t=142015Si what I'm up to is Ess AMT1 top - FF85K mids - Alpha (maybe Beta) 15 inch on the low end - Bi Amp powered - passive x'over. BTW - what are you doing for your crossover?
XO’s, funny you should ask. I intended to mention this later, but since you asked...
I bought the parts for the HF end of the XO, but plan to try a Dayton (PE) plate amp that has a second order filter for the woofers. When I built a Triska sub (PE project) last year I bought the plate amp recommended in the project. It’s a 70 watt amp that has an adjustable XO with second order filter. With only a second order XO, I couldn’t get the sub to blend properly in any of my systems. When I tried another Dayton plate amp (240 watts) that I bought for an older sub, the Triska worked just fine--because that amp has a fourth order filter. Since Martin’s design used a second order filter, I thought: “Why not re-purpose the 70 watt amp? If it works out, I can use it with this OB project, then move the Alphas and the plate amp (plus another) to an H-baffle next year.”
The cost of the passive XO parts for the woofer is almost the same as the cost of the plate amp. If this works, I can avoid buying passive XO parts for this OB and the H-baffle. I’ll let you know what happens.
I bought the parts for the HF end of the XO, but plan to try a Dayton (PE) plate amp that has a second order filter for the woofers. When I built a Triska sub (PE project) last year I bought the plate amp recommended in the project. It’s a 70 watt amp that has an adjustable XO with second order filter. With only a second order XO, I couldn’t get the sub to blend properly in any of my systems. When I tried another Dayton plate amp (240 watts) that I bought for an older sub, the Triska worked just fine--because that amp has a fourth order filter. Since Martin’s design used a second order filter, I thought: “Why not re-purpose the 70 watt amp? If it works out, I can use it with this OB project, then move the Alphas and the plate amp (plus another) to an H-baffle next year.”
The cost of the passive XO parts for the woofer is almost the same as the cost of the plate amp. If this works, I can avoid buying passive XO parts for this OB and the H-baffle. I’ll let you know what happens.
You wrote: 'You may also get a pleasant surprise if you mount the Fostex from the rear, rather than in front ...'
Sometimes people are right when they feel wrong.
In fact I got the best performance from my 3'' driver (Visaton FRS 8) when mounting it exactly that way
:An externally hosted image should be here but it was not working when we last tested it.
The only tricky part I found with rear mounting the FF85K is that like a lot of drivers with pincushion basket frames, there isn't a lot of margin at the corners. In any mounting panel thicker than about 6mm, you'd probably want a bevel, which won't leave a lot of material for screws, without using a separate mounting clip.
Rudolf, how did you mount the drivers in the OB pictured?
Rudolf, how did you mount the drivers in the OB pictured?
Hi Jim - Great Job!
Si what I'm up to is Ess AMT1 top - FF85K mids - Alpha (maybe Beta) 15 inch on the low end - Bi Amp powered - passive x'over. BTW - what are you doing for your crossover?
Thomas - I've played with the AMT1 in both 2 and 3-ways, as well as the FF85K, and aside from the major sensitivity difference that would "slightly"
complicate a 3-way XO, you might find that the little Fostex doesn't need that much help up top - I certainly don'tJim - to be clear, she did more than her fair share with the wheelbarrow - and for her loads were only a hundred pounds or so at a time. All I got to do was the spreading, compacting & screeding of the 2 substrates, and laying the 1800 + bricks on 2 sloping grades.
actually, let me rethink that first sentence ....
and we're still 14 years from celebrating our 50th anniversary - probably by that time it's "hey, how was your day sweetie?" "fine, is Survivor on tonight?" (I'm sure it will be )
back to your OB's - very nice aesthetic balance on those
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The baffle thickness starts with 4 mm at the driver cutout, which has a tight fit. You don't want to loose any mm there. The mounting screws have 7-8 mm before they brake through the 45° bevel. The pictured baffle is 16 mm chipboard, but for a lasting solution I would insist on plywood. That would ensure a good enough fastening torque of the screws.
With the rear mounted driver the front-back response changed to this (compare to post #477):
Attachments
Jim - to be clear, she did more than her fair share with the wheelbarrow - and for her loads were only a hundred pounds or so at a time. All I got to do was the spreading, compacting & screeding of the 2 substrates, and laying the 1800 + bricks on 2 sloping grades.
actually, let me rethink that first sentence ....
and we're still 14 years from celebrating our 50th anniversary - probably by that time it's "hey, how was your day sweetie?" "fine, is Survivor on tonight?" (I'm sure it will be )
What Chris won't tell you, is that when it comes to wielding a wreaking bar, there is nobody, and I mean nobody, that can surpass him.
I'm certain that his wife feels privileged to work alongside her man.
There's just something about International Super Star Status that really attracts women. I've sometimes wondered if the reason Chris got married in the first place was just to get away from the hoards of "groupies."
Best Regards,
TerryO
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Hey, be fair - I laid at least 4 of those 1800... Hmm, let's see: 4/1800 = 1/450 = ~0.222%... OK, never mind.
Regards.
Aengus
Executive Summary:
Up and running!
WOW! WOW! WOW! WOW! WOW! WOW! WOW! WOW! WOW!
Review:
I am using a plate amp to provide the XO and drive the woofers; I may not have the settings just right yet. And the plate amp has a hum which was beneath notice when it was used with an inefficient sub, but which is bothersome with the 95 dB sensitive Alphas. My brother listened to them and pronounced them too bright. I applied a small amount of treble cut (via tone controls on the Yamaha CR-1000) and agree that helps. I will decide later if I want to buy the rest of the XO parts so I could eliminate the plate amp.
What I love about Magnapan and electrostatics is all there. In fact, most of what I like about Martin’s Lowther PM2A’s is there. I was thinking that I would have to save up to buy a pair of Lowthers--but no more! OK, they aren’t Lowthers, but it’s close enough for me.
Open, spacious, clear, and detailed. Not quite the holographic projection I’ve heard from Martin’s PM2A’s (both in MLTL and OB.) Still, much closer to what I want than the Fonkens and the Metronomes (both F120A and FE108eSigma.)
Jazz and vocals are excellent. Good sound stage, dept, imaging.
They can do justice to large scale orchestral works which strain the smaller speakers. And curiously, they are the first speakers I have heard which make Paavo Jarvi’s recording of Britten’s The Young Person’s Guide to the Orchestra (Telarc CD-80660) sound decent. On any other system the bass drum is loose, flabby, boomy--makes me wanna puke. Makes me sorry I bought the CD. On these OB’s, it’s OK--not quite right, but listenable. (But I still wonder WTH the recording engineer was using for monitors.)
The low freq extension seems to be enough that I am not motivated to add a sub at this point. I will make some measurements later.
Pics to follow....
Chrisb:
Stop what you are doing. Forget about the yard. You need to build the FF85k OB NOW! If you think the FF85k sounds good in a box, you’ve GOT to hear what it does OB. (Assuming you like the dipole sound.)
Martin:
Thank You! Thank You! Thank You! Thank You! Thank You! Thank You! Thank You! Thank You! Thank You!
Up and running!
WOW! WOW! WOW! WOW! WOW! WOW! WOW! WOW! WOW!
Review:
I am using a plate amp to provide the XO and drive the woofers; I may not have the settings just right yet. And the plate amp has a hum which was beneath notice when it was used with an inefficient sub, but which is bothersome with the 95 dB sensitive Alphas. My brother listened to them and pronounced them too bright. I applied a small amount of treble cut (via tone controls on the Yamaha CR-1000) and agree that helps. I will decide later if I want to buy the rest of the XO parts so I could eliminate the plate amp.
What I love about Magnapan and electrostatics is all there. In fact, most of what I like about Martin’s Lowther PM2A’s is there. I was thinking that I would have to save up to buy a pair of Lowthers--but no more! OK, they aren’t Lowthers, but it’s close enough for me.
Open, spacious, clear, and detailed. Not quite the holographic projection I’ve heard from Martin’s PM2A’s (both in MLTL and OB.) Still, much closer to what I want than the Fonkens and the Metronomes (both F120A and FE108eSigma.)
Jazz and vocals are excellent. Good sound stage, dept, imaging.
They can do justice to large scale orchestral works which strain the smaller speakers. And curiously, they are the first speakers I have heard which make Paavo Jarvi’s recording of Britten’s The Young Person’s Guide to the Orchestra (Telarc CD-80660) sound decent. On any other system the bass drum is loose, flabby, boomy--makes me wanna puke. Makes me sorry I bought the CD. On these OB’s, it’s OK--not quite right, but listenable. (But I still wonder WTH the recording engineer was using for monitors.)
The low freq extension seems to be enough that I am not motivated to add a sub at this point. I will make some measurements later.
Pics to follow....
Chrisb:
Stop what you are doing. Forget about the yard. You need to build the FF85k OB NOW! If you think the FF85k sounds good in a box, you’ve GOT to hear what it does OB. (Assuming you like the dipole sound.)
Martin:
Thank You! Thank You! Thank You! Thank You! Thank You! Thank You! Thank You! Thank You! Thank You!
"Below Fequal, response is - 6 dB/oct drop in output, that's directly dependent on the size of the baffle . .
At Fequal, SPL of the baffled driver will be the same as its response in an infinite baffle.
Above Fequal, response rises to a 6 dB peak at Fpeak (approximately equal to 3*Fequal); and at higher frequencies, the response will depend largely on the shape of the baffle."
If the baffle width is increased, can we increase Fpeak - so that the efficiency of the FF85k is increased?
At Fequal, SPL of the baffled driver will be the same as its response in an infinite baffle.
Above Fequal, response rises to a 6 dB peak at Fpeak (approximately equal to 3*Fequal); and at higher frequencies, the response will depend largely on the shape of the baffle."
If the baffle width is increased, can we increase Fpeak - so that the efficiency of the FF85k is increased?
After this past weekend, I appreciate that advice perhaps more than you do Martin's project papers
, but fat chance, until it's finishedWell actually, that's exactly how I first heard this amazing little driver- while Dave was crunching the numbers and drawings for "boxes", I rear mounted the raw drivers into a small MDF panel, and ran them in for several dozens of hours. I may yet conduct a reality check on my testosterone levels and build a pair of the OBs for the TV room that my wife seldom inhabits. My dedicated man-cave is a narrow, L-shaped former bedroom, and I fear would not be the best environ for a full sized OB.
so that's 9 wows and thank-yous - what happens when you get really excited?
being a bit lazy about the math
Jim, et al;
Any anecdotes regarding the efficacy (if any) of slight angle to the side panel/support legs to the OB design?
Jim, the aesthetic ratio of your build, including the beveled edges of the keystone shaped baffle, is very appealing; I just wonder about any sonic advantage of angled side panels ( say around the same 5deg as the tilt-back)?
Jim, et al;
Any anecdotes regarding the efficacy (if any) of slight angle to the side panel/support legs to the OB design?
Jim, the aesthetic ratio of your build, including the beveled edges of the keystone shaped baffle, is very appealing; I just wonder about any sonic advantage of angled side panels ( say around the same 5deg as the tilt-back)?
Try to keep the sides of the baffle (front AND back) free from major protrusions at the height of the FF85K. The big supporting brace near the Fostex in Jims baffle looks less than optimal to me.
If you look at the right picture beyond you can see what kind of brace I use in this case:
Having side panels (AND the top brace) around the woofer is OK -especially if it is just the 5 deg of the tilt. The (small) resonance of that U-frame should be well outside the woofer passband. And the wings will pretend a wider baffle to the woofer (added depth = added width at both sides).
Rudolf
Chrisb,
If I get any more excited, it might be hazardous to my health! With each build I have kept looking to get closer to the characteristics I find appealing in Lowthers, Maggies, Martin Logans, etc. These OBs are delivering on that. I know that these qualities are not universally appealing, as my brother found them to be just OK.
As to the design specifics: I have no way to quantify the effects of the beveled edge (it should reduce diffraction,) the side panels (which do follow the angle of the edge's slope and should have some effect similar to a shallow 'U' baffle,) or the 2x4 bracing (which should improve the quality of the bass.) I have never listened to this MJK OB in it's Rev 1.0 style. When building I just go on what little knowledge I have and a gut feeling for what might be helpful. It would be very interesting to compare my build with the original version. And if there is anyone out there in the upstate NY region in possession of the rectangular baffle style, I would be eager to get together and compare.
Cheers, Jim
If I get any more excited, it might be hazardous to my health! With each build I have kept looking to get closer to the characteristics I find appealing in Lowthers, Maggies, Martin Logans, etc. These OBs are delivering on that. I know that these qualities are not universally appealing, as my brother found them to be just OK.
As to the design specifics: I have no way to quantify the effects of the beveled edge (it should reduce diffraction,) the side panels (which do follow the angle of the edge's slope and should have some effect similar to a shallow 'U' baffle,) or the 2x4 bracing (which should improve the quality of the bass.) I have never listened to this MJK OB in it's Rev 1.0 style. When building I just go on what little knowledge I have and a gut feeling for what might be helpful. It would be very interesting to compare my build with the original version. And if there is anyone out there in the upstate NY region in possession of the rectangular baffle style, I would be eager to get together and compare.
Cheers, Jim
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