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Old 6th November 2011, 05:00 AM   #1
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Default Fostex F120A in BIB

I built a couple of BIB's for my never used Radio Shack 40-1354A speakers two weeks ago to the Terry Cain specs of 70 inches tall, 5.5 inches wide and 12.5 inches deep inside dimensions. Outside 7 inches wide and 14 inches deep. No supra baffle.

I listened to them for about a week, sounded real good, couldn't believe the bass out of these, they are close to the corners of my room and my room is small 12 feet by 13 feet.

Decided I liked them so well that I ordered a set of Fostex F120A's from Madisound and had them shipped in 2 day delivery.

Built a 13.75 inch round supra baffle for them as the hole was too big for the F120A's.

When I first fired them up sounded tinny and hollow and could hear the coloration but in about 4 hours started settling down. Have about 20 hours on them and they are starting to sound really good. The bass is solid down to 40 Hz, stronger at 40 Hz then at 80 Hz and very little bass at 31.5 Hz. Guessing fairly strong at 35 Hz. This is with a Sterophile test CD. Will have to bring in the tone generator and radio shack sound meter to see how low it really goes.

Made the cabinets out of 4 X 8 birch (from Home Depot) with I believe 6 plys and plenty of voids, but hear no buzzing or looseness. Cut the sides 45 degrees and glued them together using straps to hold them together until dry, 6 per cabinet. left the bottom so I could remove it if I had to. Stuffed the top above the drivers with Dacron tight and put one 5.5 by 14 inch piece of carpet under-pad felt on back panel right below speaker and another 5.5 by 14 at bottom of cabinet. Stained the cabinets with one coat of Golden Oak and then one coat of Walnut and then one coat of Flat Polyurethane clear coat.

This was just a throw together cabinet to test the RS 40-1354A's with and turned out so good I had to try a better set of speakers because I liked the Radio Shacks so well.

Its funny I was setting in my stereo room listening to The Moody Blues the singles+ CD and was dozing off at about 10:50 pm Saturday night when I felt a shaking of my Lazy Boy and looked over to see who was shaking me (could only be my wife), but nobody there. Kinda spooked me. Then my wife came in from her craft room and asked me if I felt the shake. We live in south Wichita, Kansas and we felt the earthquake from Oklahoma. My wife thought if he has that music up so loud that he is shaking the house I am going to have a talk with him.

I use Elvis 30 hits CD to test speakers with and also Best of Jim Reeves 3 set CD, both to test for voice purity. These F120A's and my old JBL L14A transmission line woofers with JBL M151 mid bass with JBL L175 drivers on Altec 511 horns for mid range are the only speakers that can reproduce these voices realistically That I have had.

So far I am more than happy. And I hear no slowness in bass or a lag in sound in general. Maybe I would if they were in bass reflex enclosures.

Kenny
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Old 6th November 2011, 06:58 AM   #2
GM is offline GM  United States
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Cool!

GM
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Old 6th November 2011, 07:48 AM   #3
ODougbo is offline ODougbo  United States
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BIB, that must be Big is Better.

I've been on a roll lately with 5" Fostex designs, and have a couple of cabinet ideas, but if you want the ultimate cabinet, you're going to want to talk the Pros. about Fonkens.

In the mean time, pick up a sheet of 3/4" MDF at HD. I would build the BR and the DBR, with the plans came with them. One $30 sheet will build both sets (I think).

The bass goes pretty darn low with FX120s, you can get lower than 30hz I'm sure.

Last edited by ODougbo; 6th November 2011 at 08:02 AM.
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Old 6th November 2011, 02:02 PM   #4
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Quote:
Originally Posted by ODougbo View Post
BIB, that must be Big is Better.

I've been on a roll lately with 5" Fostex designs, and have a couple of cabinet ideas, but if you want the ultimate cabinet, you're going to want to talk the Pros. about Fonkens.

In the mean time, pick up a sheet of 3/4" MDF at HD. I would build the BR and the DBR, with the plans came with them. One $30 sheet will build both sets (I think).

The bass goes pretty darn low with FX120s, you can get lower than 30hz I'm sure.
That would be cool! 30Hz with a 5 inch driver. I have 3 sheets of 13 ply Baltic Birch and would use it. The reason I used the 4 X 8 is the 13 ply is 5 X 5 foot. I have built cabinets with MDF and it isn't too hard to work with.

I have looked into the Fonkens and BR and DBR, but the BIB's peaked my interest.

The mid range and lows are blowing me away and the highs are not bad, not great but not bad. The extreme lows are MIA.

It's like everybody says, it's hard to adjust your mind to the fact that a 5 inch full range driver can get that much overall sound. And it is plenty loud enough in my room. Of course in a bigger room it would probably struggle.

I could hear the cone cry in the 1354 driver, but if you kept the volume down it sounded really good. I bought 18 of these drivers when they had them on sale. I put 14 in my home theater in the walls in .5 cu ft boxes. I just blocked off .5 cu ft between the studs and sealed up with caulking and stuffed with Dracon. I lined the whole room including the ceiling with OSB 1/2 inch 4 x 8 sheets then put sheet rock over the OSB. I put 4 1354's in for center, one each for left and right front, one each for left and right side and one each for left and right rear. Then I took 4 and put them in on the rear wall and tied them in for center so I could turn down the volume and still hear the center voice. I thought it would mess up the balance but I like it, you can turn down the sound and hear the speech and it makes my wife happy as it won't blast you out of the room. The 1354's just seem to be made for home theater. I then put in 2 air vents in the floor and put 2 sub woofers in the crawl space with cabinets and the woofers up against the vents. That way I have no speaker cabinets in the room. The room is 16 X 15 foot.

I was really looking into Lowther DX3's but decided to give the F120A's a try. So far I am happy with the results.
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Old 6th November 2011, 03:05 PM   #5
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Mater of fact, working on cabinets today, should have them done in a couple of hours. I pulled out the industrial use only lacquer. Don't try that at home.......

I built 1 Fostex BR box so I could test it against a slightly larger pair - with a bigger port - I all ready know the answer though, the Fostex design BR box looks good, but it's pretty wimpy.

I was going to say, at some point, put the speakers in the walls and ceilings, but that sounds like what you have done.
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Old 6th November 2011, 03:53 PM   #6
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Post your pics.
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Old 6th November 2011, 04:13 PM   #7
ODougbo is offline ODougbo  United States
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Default FF125wks

Not finished ~ but had to listen...they are about the same.

However:

The oak ones (left) have a hint of extra bass and sound a bit more "full".

I need to recess/flush the drivers, I made a router guide (It's a tricky shape), but may ask my buddy with the CNC router to make a guide.

The speakers have about 30 hours on them.
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Old 6th November 2011, 06:07 PM   #8
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What sort of amp are you using on the F120A's? Both MJK & I have found that direct coupled SS amps work very poorly with these drivers. The highs are just awful.

With my old Sansui receivers which have cap. coupled output, they sound pretty good. Best results have been with tubes.

Cheers, Jim
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Old 6th November 2011, 08:43 PM   #9
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Don't look at the baffles too closely as it was sprinkling outside and I cut them outside so I didn't have to move the cars out of the garage, so I was in a hurry. Also you may be wondering why I used a wood plate for the terminals. I glued up the cabinets and found out I put one of the dividers in backwards so I had to cut a new speaker hole in one of the cabinets. LOL! I really felt dumb when I found out I did that. I am going to build new baffles and terminal plates and also probably veneer the cabinets as I am really happy with the sound. Like I said I just was experimenting and didn't want to spend a lot of time and money on these if they sounded bad. Been there done that many of times. And one of the terminal plates are stained the other one isn't. The one stained was the one I experimented with to see what the stain would look like.

I use a Doge 6 tube CD player with 2 Siemens ECC801S's and 4 GE JAN 5751s, Doge 8 tube preamplifier with 4 Siemens ECC801S's and 4 Telefunken 12AX7 smooth plates (for phono). And a Audioromy FU13 amplifier with 2 Amperex PQ 6922s, 2 GE 6V6 GT black plates and 2 FU13s. I also have a Empire 598III turntable with Dynavector DV20H cartridge.
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Old 8th November 2011, 08:40 AM   #10
ODougbo is offline ODougbo  United States
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Kenny,

With all those drivers and wood you have on hand, you might want to try some different boxes.

Pic one is a double tall DBR, I didn't end up using the bottom section, but may someday. When they are hooked up, it sounds like a 10" subwoofer.

If you do build a DBR, flip the small port "L" upside down and put the bottom port on the back. Might want to line the small top chamber with Dynamat(.com) or something. Keep your eyes open for Ultra Touch insulation (for fill).


Of course you want to build a Onken set, I didn't think they were that difficult once I studied the plans. [not that mine are finished quality, but did build them in a day]
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File Type: jpg Onken 2.JPG (134.4 KB, 74 views)
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Last edited by ODougbo; 8th November 2011 at 08:42 AM. Reason: typo
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