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Old 15th May 2008, 01:36 AM   #1
devodad is offline devodad  United States
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Default New twist on Fonken project?

I have searched this area and have not been able to find any references to what I would like to accomplish. I am restoring an old farmhouse with the first item of business being the master bedroom. It is 12' x 18' with a 7-1/2' ceiling. One end of the room, where all of the equipment will go, has a sloped ceiling down to about 5' height (about 6' of sloped ceiling). I originally wanted to install built-in speakers, but the cost was more than I wanted to bear, besides, that just sounded too boring to me (no design problems to solve, no chance to make serious sawdust) So, with my Madisound catalog in hand, I started to search here and stumbled upon designs like the frugel-horns, the spawn designs, etc. Many of those I felt were too big and invasive to the room and furniture layout. There is the WAF factor as well.

So, long story short, I am looking at one of the fonken designs and trying to figure out how to make it a built-in. The wall cavity is 5-1/2" deep, so ufonken or the GR fonken would appear to physically fit. So, at this point I have two questions:

1. Are the fonken design senistive to small interior dimension changes or is the voulme the major factor to performance?

2. Since the baffle attachment would have to be re-designed, would it be possible to screw/bolt it to the box carcass such that it would actually stand proud of the finished wall? I know that sealing it would be critical.

3. Lastly, is there any benifeit to adding a tweeter to the fonken design? Does the full range provide adequate coverage?
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Old 15th May 2008, 04:01 AM   #2
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Default Re: New twist on Fonken project?

Quote:
[i]Originally posted by devodad [/i
1. Are the fonken design senistive to small interior dimension changes or is the voulme the major factor to performance?

2. Since the baffle attachment would have to be re-designed, would it be possible to screw/bolt it to the box carcass such that it would actually stand proud of the finished wall? I know that sealing it would be critical.

3. Lastly, is there any benifeit to adding a tweeter to the fonken design? Does the full range provide adequate coverage?
1/ Box volume (13 litre net) + port shape & size are the important bits, i'm happy to offer suggestions

2/ sure

3/ most people find little need... if you were to add a cap XOed tweeter it would need to come in at 15k or so... if you wanted to make a 2-way out of it an XO juts below the 7k bump would be where i'd target.

dave
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Old 15th May 2008, 05:11 PM   #3
chrisb is online now chrisb  Canada
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If I may?

Having experienced most of them, IMHO a big part of the "magic" of the (original) Fonken design, as well as subsequent siblings / progeny, is the combination of narrow baffle, resistive port tuning, and the small, well braced (not massively damped) enclosures

The imaging doesn't disappear in the smaller the boxes, although the bass extension and weight of course decline in absolute quantity. Powered woofers would definitely be required with the microF (FF85K) for anything other than computer monitor use.

I digress - my intuition is that a wide baffle design like the Mileva might be better adapted to an in-wall application. The width would certainly fit between standard wall stud spacing of 16" o/c, and the finished depth of approx 132mm (5 1/4") of the free-standing box when constructed with 15mm (5/8") material would protrude slightly past the drywall on typical 2x4" frame construction.

If the reconstruction of the room allows the option to increase the depth of the wall to 2x6" framing, then the front baffle could be mounted flush.

I might also suggest that the lack of baffle step loss could alter the freq response enough that some might well feel the need for a tweeter, in which case Dave's suggestion of 6 8K XO would be a good starting point.
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Old 16th May 2008, 05:51 AM   #4
devodad is offline devodad  United States
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Dave,

Thanks for the advice. I took a few moments tonight to bash a qucik and dirty sketch together (no scale) to give you a better idea at what I was thinking of (first time I attempted to use Sketch-Up - took about 20 minutes). It sounds like this will work well. These would be going in a 2x6 wall, so it sounds as if there will be plenty of depth as well.

Chrisb suggested the Mileva - would that provide a better bass responsethan the GR? I am looking to use at least one pair of FE127 cabinets and may supplement them with another pair of the FF85's for the B channel, but if one pair does the job well, I could just stop there.

I hate to cover the speakers with grilles or grille cloth, but with little kids in the house, I think it will reduce the chance of dirty fingers and other stuff on the drivers. Would some sort of grille cloth greatly reduce the sound output? On of the drivers for buillding them in the wall is to get them out of reach.
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Old 16th May 2008, 06:04 AM   #5
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Quote:
Originally posted by devodad
Chrisb suggested the Mileva - would that provide a better bass responsethan the GR?
Yes.

dave
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Old 22nd May 2008, 04:09 AM   #6
devodad is offline devodad  United States
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Dave,

Received the Mileva plan yesterday. Looks like it will work well in my installation. I hope to start on the cabinet rears this weekend. I will also be ordering a pair of EnABLed FE127's to match up with them. I will post updates as I can, but expect it will be a lengthy process since there are other jobs which take priority (installing insulation, wallboard, plaster, etc.)
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Old 31st October 2008, 12:16 AM   #7
devodad is offline devodad  United States
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Default wool felt????

The Mileva's have slowly taken shape and I close to getting them in the wall. I have a question about the wool felt for the stuffing. I found one of Dave's sketches on aonther thread that shows how to plan the stuffing/damping, but the wool feltmay be a problem. What is it exactly? I used a link I found for Buffalo Felt and took a look at their products, but am still unsure on what I should use i.e. thickness, density, etc. On of my buddies suggested going the the Salvation Army store and buying an old wool coat, such as the Navy Pea Coat (reaally heavy, dense wool) I saw. It seems like it could work. I did buy the premium poly stuffing at WalMart for the other areas in the cabinet. Any body ever try to use old wool piece good like this?
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Old 15th October 2009, 04:54 PM   #8
devodad is offline devodad  United States
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Default Mileva extension?

One of the Mileva cabinets (the finished one) was damaged when our basement was flooded a couple of monts back . About 3"-4" of the bottom was saturated with water and the plywood is starting to de-laminate (I thought the glue used in abuco plywood was supposed to be waterproof). I will try to salvage what I can. But as I think about placement in the wall cavity, it occurs to me that my plan for placing the speaker approximately 60" above the floor will not work as well as having the port directly on the floor. So my question is this: Can I extend the horn section ino a longer enclosure, keeping the folded upper section (it appears to be approximately 9 liters) the same size? I would like the port to vent out through the baseboard and the speaker to appear as a picture frame mounted on the wall. I haven't been able to find a whole lot of info on the specific design requirements. Thanks.
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Old 15th October 2009, 05:10 PM   #9
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The distance relation between the driver and the port is fixed. If you want the driver 60" off the floor, flip the box upside down so that the vent is near the ceiling. This will have the same affect as floor loading.

dave
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Old 16th October 2009, 04:52 PM   #10
devodad is offline devodad  United States
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Thanks Dave. That's a great idea! I wish I could remember to think outside the box like that more often.
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