I used the same values in Martin's paper as Ron did.
http://www.quarter-wave.com/OBs/OB_Design.pdf
Iron core inductors were the same part numbers in the paper above but I used Dayton caps instead of the Solen's. Thinking of bypassing the hi pass cap with a FT-3 teflon down the road once things break in. Did I say man these speakers sound good even with only around 10 hours on them!!! I think Ron nailed it by trying the FE87E's out.
BR
http://www.quarter-wave.com/OBs/OB_Design.pdf
Iron core inductors were the same part numbers in the paper above but I used Dayton caps instead of the Solen's. Thinking of bypassing the hi pass cap with a FT-3 teflon down the road once things break in. Did I say man these speakers sound good even with only around 10 hours on them!!! I think Ron nailed it by trying the FE87E's out.
BR
They are C&W but Jennifer has a great voice that is sultry and gritty at the same time - she's fun to listen to. My OB's
Hello everybody,
Here's some pictures of my work in progress... I recently moved to a nice but small brownstone house close to the city center in Utrecht, The Netherlands. My loving girlfriend would have allowed my to put my 4 feet backloaded horns in our living room but even I thought that would be a bit much. I think that clever girl of mine bluffed her way out of those 'coffins'.... ;-) Don't feel bad though, I manage just fine with a multimedia computer, 5.1 soundcard, three (!) Philips vintage AG 9016 SET amps (1964!!) driving 4" full-rangers and a sub... All very high WAF with the center speaker built into the TV table and just two visible (but very smart) TQWT's.... Keeps us both happy.
Anyway, having banned myself to the attic (which doubles as workroom, music/guitarroom, guestroom and general storage) I was in need of something new. Those horns were simply too big and too deep. So MJK's design came along. I always wanted to do an OB design, allready had some Fostex drivers and even though these babies are not mini speakers the size is ok for my small audio refuge.. Especially depth-wise and weight-wise (mind you, storage area is behind them).
Long story short: the virus hit me right between the eyes so I started building them. Took the drivers out of the old horns and donated the enclosures to a serious horn fan (with a big house and a even bigger car to pick them up...). I obviously don't have a workshop or shed for this sort of project but I lend some tools and MJK has been so kind to answer my novice questions. It has taken some time (lot's of things to do around the house when you have just moved) but the basic set-up is ready. I will start experimenting now and would like to share some of my experiences/ considerations (and recieve tips and feedback from all you seasonned builders; it will only help my system to sound better!).
No copyright issues here, I guess ;-)
My impressions:
First of all: I probably havn't heared as many systems as you all have and I am changing many parameters at the same time, so.....be gentile? ;-). The last three month the hifi set wasn't priority one and I am a bit out of shape (eardrum wise). The last 10 years of my audio life have been: vintage IMF ALS-50/ NAD SS amp, TQWT with 103S/ KT-88 PP, backloaded horns with sigma 103S/ 300-B SET amp. I just LOVE the magic soundstage of the fostexes and have been sacrificing LF for them.
Drivers:
Apart from the Alpha's I will be trying a few full rangers. I have some Fostex 103-S left over from earlier projects, which would need an L-pad (thank you MJK for the advise). Furtermore, Planet-10 mentioned the Alnico versions earlier in this thread, I have a set of two OEM Akai ones (see the last picture). I expect the most of them because sensitivity probably matches the Alpha's best. And their Alnico ;-) The Fe-83 and sigma 103-E are also candidates but I havn't got those yet so I start with what I have. In the picture you will see that I have mounted the 103-A in the back for testing. (and there's another picture below with the 103-S for dramatic effect..). The 103-A's diameter is different from the sigma's and I want to keep all options open. The final FR will go in the front and the backside will be filed out. Planet 10's phase plugs might be an option.
Amplification:
I have an 6 watt 300-B SET amp. It used to be KT-88 push-pull but my good friend and hifi/valve guru Jasper upgraded the amp. I LOVE the sound but I don't expect it to do LF very well in an OB (watt-wise). This however gave me a good excuse to purchase some A&T (Hawk Audio) monoblocks (I drove 100 miles in freezing conditions over very poor roades with my motorcycle to get them). A&T/ Hawk Audio is a dutch brand and they are 15 watts class A. Not too much but my listening room isn't very big either. Bi-amping is not in the spirit of MJK's design but I have to start somewhere.... Maybe I will move to just a valve pre amp?
X-over:
Oops once again I am deviating.... I bought a very cheap active filter (german Reckhorn B-1, see: http://www.reckhorn.com/manual/user_manualB1.pdf for details) for experimenting. Maximum high pas is 150 Hz. Mjk's choice is 200 Hz which is probably for a good reason (less load on the FR, I presume). Advantages are a low-pass filter and the possibility to boost LF. I can always go back to passive filtering but I just had to try this. let's see how it goes.
Placement:
Like I said, my listening room is small but behind the speakers are sliding doors for storage which -when opened- will give them more room to breath. I have put some carpets on the wooden floor for damping too.
Mind you, I have relativly new valves that will require some more breaking in, the 103-A's have been idle for a long time and I have no idea how interlinks will work in this new set-up. Deviations from the original design are for practical or cost reasons, I absolutly don't pretend to know things better.... Please don't expect too many experiences shortly... Some more home improvement issues and as the credit crisis has hit the Netherlands aswell I need a new job too ;-(
I'll keep you all posted and MJK thanks for sharing your designs with us, it's being much appreciated.
Cheers, Ralph
An externally hosted image should be here but it was not working when we last tested it.
Hello everybody,
Here's some pictures of my work in progress... I recently moved to a nice but small brownstone house close to the city center in Utrecht, The Netherlands. My loving girlfriend would have allowed my to put my 4 feet backloaded horns in our living room but even I thought that would be a bit much. I think that clever girl of mine bluffed her way out of those 'coffins'.... ;-) Don't feel bad though, I manage just fine with a multimedia computer, 5.1 soundcard, three (!) Philips vintage AG 9016 SET amps (1964!!) driving 4" full-rangers and a sub... All very high WAF with the center speaker built into the TV table and just two visible (but very smart) TQWT's.... Keeps us both happy.
Anyway, having banned myself to the attic (which doubles as workroom, music/guitarroom, guestroom and general storage) I was in need of something new. Those horns were simply too big and too deep. So MJK's design came along. I always wanted to do an OB design, allready had some Fostex drivers and even though these babies are not mini speakers the size is ok for my small audio refuge.. Especially depth-wise and weight-wise (mind you, storage area is behind them).
Long story short: the virus hit me right between the eyes so I started building them. Took the drivers out of the old horns and donated the enclosures to a serious horn fan (with a big house and a even bigger car to pick them up...). I obviously don't have a workshop or shed for this sort of project but I lend some tools and MJK has been so kind to answer my novice questions. It has taken some time (lot's of things to do around the house when you have just moved) but the basic set-up is ready. I will start experimenting now and would like to share some of my experiences/ considerations (and recieve tips and feedback from all you seasonned builders; it will only help my system to sound better!).
No copyright issues here, I guess ;-)
My impressions:
First of all: I probably havn't heared as many systems as you all have and I am changing many parameters at the same time, so.....be gentile? ;-). The last three month the hifi set wasn't priority one and I am a bit out of shape (eardrum wise). The last 10 years of my audio life have been: vintage IMF ALS-50/ NAD SS amp, TQWT with 103S/ KT-88 PP, backloaded horns with sigma 103S/ 300-B SET amp. I just LOVE the magic soundstage of the fostexes and have been sacrificing LF for them.
Drivers:
Apart from the Alpha's I will be trying a few full rangers. I have some Fostex 103-S left over from earlier projects, which would need an L-pad (thank you MJK for the advise). Furtermore, Planet-10 mentioned the Alnico versions earlier in this thread, I have a set of two OEM Akai ones (see the last picture). I expect the most of them because sensitivity probably matches the Alpha's best. And their Alnico ;-) The Fe-83 and sigma 103-E are also candidates but I havn't got those yet so I start with what I have. In the picture you will see that I have mounted the 103-A in the back for testing. (and there's another picture below with the 103-S for dramatic effect..). The 103-A's diameter is different from the sigma's and I want to keep all options open. The final FR will go in the front and the backside will be filed out. Planet 10's phase plugs might be an option.
Amplification:
I have an 6 watt 300-B SET amp. It used to be KT-88 push-pull but my good friend and hifi/valve guru Jasper upgraded the amp. I LOVE the sound but I don't expect it to do LF very well in an OB (watt-wise). This however gave me a good excuse to purchase some A&T (Hawk Audio) monoblocks (I drove 100 miles in freezing conditions over very poor roades with my motorcycle to get them). A&T/ Hawk Audio is a dutch brand and they are 15 watts class A. Not too much but my listening room isn't very big either. Bi-amping is not in the spirit of MJK's design but I have to start somewhere.... Maybe I will move to just a valve pre amp?
X-over:
Oops once again I am deviating.... I bought a very cheap active filter (german Reckhorn B-1, see: http://www.reckhorn.com/manual/user_manualB1.pdf for details) for experimenting. Maximum high pas is 150 Hz. Mjk's choice is 200 Hz which is probably for a good reason (less load on the FR, I presume). Advantages are a low-pass filter and the possibility to boost LF. I can always go back to passive filtering but I just had to try this. let's see how it goes.
Placement:
Like I said, my listening room is small but behind the speakers are sliding doors for storage which -when opened- will give them more room to breath. I have put some carpets on the wooden floor for damping too.
Mind you, I have relativly new valves that will require some more breaking in, the 103-A's have been idle for a long time and I have no idea how interlinks will work in this new set-up. Deviations from the original design are for practical or cost reasons, I absolutly don't pretend to know things better.... Please don't expect too many experiences shortly... Some more home improvement issues and as the credit crisis has hit the Netherlands aswell I need a new job too ;-(
I'll keep you all posted and MJK thanks for sharing your designs with us, it's being much appreciated.
Cheers, Ralph
"Bi-amping is not in the spirit of MJK's design but I have to start somewhere..."
I am pretty sure in both of MJK's open baffle projects he is by-amping. In the Lowther OB he mentions buying two new Rotel amps and an active crossover. Although not mentioned in the second open baffle project he is still using the active crossover and thus would believe it is bi-amp'ed as well.
I have also built this OB and bi-amp'ed it as well. I am very pleased with the results.
I am pretty sure in both of MJK's open baffle projects he is by-amping. In the Lowther OB he mentions buying two new Rotel amps and an active crossover. Although not mentioned in the second open baffle project he is still using the active crossover and thus would believe it is bi-amp'ed as well.
I have also built this OB and bi-amp'ed it as well. I am very pleased with the results.
Martin, thank's for sharing.
Took about 4 hours from start to finish.
Top and bottom piece from a bed.(a bit smaller : 19x36 inch ....made all the x-over parts 10% smaller also)
Cut holes .............place speakers.
Look for x-over parts in the box.......
start listening...............and be surprised!!
Total cost:
woofers 2x 40 euro (Qtc ; 0,78 was the best I could find around here)
foster 085 2x 1 euro
x-over , was in the box ??
wooden stand at the back 2x 2,5 euro
small parts , about 2 euro
anyway less then 50 euro !!!
Sound like thousend euro each !!
Great work Martin!!
Never build anything with so much ease and so satisfying result!!
Took about 4 hours from start to finish.
Top and bottom piece from a bed.(a bit smaller : 19x36 inch ....made all the x-over parts 10% smaller also)
Cut holes .............place speakers.
Look for x-over parts in the box.......
start listening...............and be surprised!!
Total cost:
woofers 2x 40 euro (Qtc ; 0,78 was the best I could find around here)
foster 085 2x 1 euro
x-over , was in the box ??
wooden stand at the back 2x 2,5 euro
small parts , about 2 euro
anyway less then 50 euro !!!
Sound like thousend euro each !!
Great work Martin!!
Never build anything with so much ease and so satisfying result!!
Attachments
![alles optio 6-5-09 104 [640x480].jpg](/community/data/attachments/112/112834-ba34df39c360a2274756beb577c79f83.jpg)
to tea-bag,
Thank's for the compliment.
All the work was already done in the bed factory.
Was the only proper way for me to re-use the bed-components.
I'm at work at this moment, will post another pic of the back-side this evening.
They have 100+ hours on them and start sounding more smooth.
Very positif reactions from the others who hear them.
Thank's for the compliment.
All the work was already done in the bed factory.
Was the only proper way for me to re-use the bed-components.
I'm at work at this moment, will post another pic of the back-side this evening.
They have 100+ hours on them and start sounding more smooth.
Very positif reactions from the others who hear them.
Sorry wixy,
from what I can see on your picture, the inner taper of the FE108 back opening looks quite narrow. Any chance to get it any wider, like chamfering a bit at the outer end?
Look, what a difference different mounting of a driver can make for the front (black) and back (red) wave on-axis:
from what I can see on your picture, the inner taper of the FE108 back opening looks quite narrow. Any chance to get it any wider, like chamfering a bit at the outer end?
Look, what a difference different mounting of a driver can make for the front (black) and back (red) wave on-axis:
Attachments
The Back Story
I bought a pair of Fostex FF85k drivers to build a pair of micro-Fonkens. Since I was in the middle of another build (Metronome with F120A,) I built a pair of cabinets (using the term very loosely) from 2 liter soda bottles and scrap wood which I dubbed The Sprites.
I was so taken with the FF85k that I decided to build an OB with it. I figured I’d build an H-baffle with Eminence Alpha 15, per Martin J King. So I bought the Alphas and another pair of FF85k’s.
Now I’m going crazy seeing the drivers just sitting in my office. Can’t wait. Must build something NOW! Maybe I’ll buy a piece of OSB and make a simple passive OB like MJK’s project. But I’ve got half a sheet of birch veneered ply sitting in the garage. Maybe I should use that. Can’t stand to make a hack job with decent ply...
OK, fire up MJK’s MathCAD worksheets and look at how the FF85k might work. And while I’m at it, how about making the baffle more attractive? Consult wife...
Sidebar
My wife has been VERY tolerant of my stereo systems. From the rather large RTR 280DR’s I bought back in ’74 to the Visonik sat/sub second system added in the late ‘70s. The key is consultation. If she is part of the process, then she is invested in the program. So the ugly little Sprites were fine in the living room before the micro-Fonkens were finished. And now they’re fine in the family room preparing for the OBs. She chuckles every time she looks at them.
An MJK OB (mostly)
Large black rectangles won’t cut it. (Too much like the monoliths from ‘2001A Space Odyssey.’) A key stone shape (22” wide at the bottom and 14” wide at the top) with a veneered, beveled edge and finished with clear polyurethane gets the nod of approval. The MathCAD model looks essentially identical to the rectangular baffle.
Perfectly vertical isn’t good; a 5 degree tilt should do it. How to support the baffle? start with a base 15” deep X 22” wide made from 2 layers of 0.5” BB ply leftover from the micro-Fonkens. Triangular side pieces 28” tall made from demolition scrape (kitchen remodel a couple years ago.) That doesn’t sound like enough to brace a 15” woofer... OK, let’s add 2x4’s up the sides and another between those supports above the woofer. Photo below shows a back view--one before and one after the flat black paint.
Second photo is a front view.
I am adding small furniture glides with 1/4-20 shafts for now. If I don’t like them, I can replace them with spikes.
By the end of this weekend I hope to have the paint and polyurethane done and enough hours on the FF85k’s for me to install the drivers. More then...
I bought a pair of Fostex FF85k drivers to build a pair of micro-Fonkens. Since I was in the middle of another build (Metronome with F120A,) I built a pair of cabinets (using the term very loosely) from 2 liter soda bottles and scrap wood which I dubbed The Sprites.
I was so taken with the FF85k that I decided to build an OB with it. I figured I’d build an H-baffle with Eminence Alpha 15, per Martin J King. So I bought the Alphas and another pair of FF85k’s.
Now I’m going crazy seeing the drivers just sitting in my office. Can’t wait. Must build something NOW! Maybe I’ll buy a piece of OSB and make a simple passive OB like MJK’s project. But I’ve got half a sheet of birch veneered ply sitting in the garage. Maybe I should use that. Can’t stand to make a hack job with decent ply...
OK, fire up MJK’s MathCAD worksheets and look at how the FF85k might work. And while I’m at it, how about making the baffle more attractive? Consult wife...
Sidebar
My wife has been VERY tolerant of my stereo systems. From the rather large RTR 280DR’s I bought back in ’74 to the Visonik sat/sub second system added in the late ‘70s. The key is consultation. If she is part of the process, then she is invested in the program. So the ugly little Sprites were fine in the living room before the micro-Fonkens were finished. And now they’re fine in the family room preparing for the OBs. She chuckles every time she looks at them.
An MJK OB (mostly)
Large black rectangles won’t cut it. (Too much like the monoliths from ‘2001A Space Odyssey.’) A key stone shape (22” wide at the bottom and 14” wide at the top) with a veneered, beveled edge and finished with clear polyurethane gets the nod of approval. The MathCAD model looks essentially identical to the rectangular baffle.
Perfectly vertical isn’t good; a 5 degree tilt should do it. How to support the baffle? start with a base 15” deep X 22” wide made from 2 layers of 0.5” BB ply leftover from the micro-Fonkens. Triangular side pieces 28” tall made from demolition scrape (kitchen remodel a couple years ago.) That doesn’t sound like enough to brace a 15” woofer... OK, let’s add 2x4’s up the sides and another between those supports above the woofer. Photo below shows a back view--one before and one after the flat black paint.
Second photo is a front view.
I am adding small furniture glides with 1/4-20 shafts for now. If I don’t like them, I can replace them with spikes.
By the end of this weekend I hope to have the paint and polyurethane done and enough hours on the FF85k’s for me to install the drivers. More then...
Attachments
- Status
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