FE107e prototypes done! 10" XLS next - diyAudio
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Old 17th May 2004, 08:16 PM   #1
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Default FE107e prototypes done! 10" XLS next

My friend and co-worker Fred finished a pair of cabinets for FE107e's while I was loafing in the mountains of New Mexico. They are constructed of 3/4 inch particle board. (The speakers, not the mountains.) The design is closely based on the mass-loaded transmission line that GM came up with. Thanks, GM! This morning, we added a baffle step correction circuit comprising a 1.7 mH inductor and 8 Ohm resistor. I had thought we would want to reduce the resistance after we listened some, but no.

How do they sound? The midrange and treble sound very, very good. The imaging is about as good as it gets. I have yet to hear it load up with a resonance and "shout," not even a tiny bit. Not surprisingly, the bass is weak. I suspect they will sound better in that regard when they are broken in more. There's only about 5 hours on the drivers. In any case, I will use my pair in conjunction with a subwoofer. Fred is still contemplating what to do about low bass.

I have the subwoofer parts sitting in my office - 10" Peerless XLS driver and 400 gram passive radiator, some spikey feet, acoustic foam and fuzz, T-nuts, and a subwoofer amp. The amp from Parts Express appears to be well constructed. It is well sealed and looks pretty stiff.

Thank you all for your very generous help, and for your patience.

I tried to download pictures, but they were too big. Not much to see, really.
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Old 17th May 2004, 09:00 PM   #2
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Any pics?? After the XLS you wont be bass light
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Old 17th May 2004, 09:47 PM   #3
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Originally posted by 5th element
Any pics?? After the XLS you wont be bass light

Here's one. It's Fred to the right, and the Ariel underneath.
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Old 18th May 2004, 04:33 AM   #4
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Here's a picture with the speaker in the proper orientation. Instead of sitting on a stand like that, one speaker will sit on the subwoofer, and the other on a matching box. The subwoofer and matching box will each be 27.5" tall including toe spikes.
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Old 19th May 2004, 04:04 AM   #5
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Well... edge.exe was right. I need a bigger inductor for the baffle step correction. I tried using 1.7 mH. Nope. It sounds better with two of them ganged up making 3.4 mH. I'm going to order some 2.7 mH inductors, which is what the program suggested.
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Old 21st May 2004, 04:14 AM   #6
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Oh golly!

I lined the top 2/3rds or so of the insides of the cabinets with 1/4" felt. Wow! That really cleaned up the sound. These things sound great now. I mean, GREAT. They do benefit from bass boost. I'm running them right now with the Richter Scale maxed out (+12dB) at 45Hz and +4dB at 63Hz. Martin's mathcad worksheet says the speakers are only good to about 65Hz unaided. To protect some against cone over-excursion, I have it all the way down (-12dB) at 22.5 and 31.5 . So far, no disaster.

With the EQ, these little speakers do quite nicely in my office. The Ariels can move in with me at home now. We are going to build a subwoofer this weekend. What that means is, Fred is going to build the cabinet and I'm going to think good thoughts. I don't know whether I'll use the subwoofer at home or office. I might have to build another one. This DIY stuff is like eating peanuts, eh?
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Old 26th May 2004, 03:06 AM   #7
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Default tweak report

Baffle step diffraction appears to be the buggaboo of this thing. I used edge.exe to calculate a BSC circuit - 2.7 mH/8ohms. But when the speakers were placed close to the back wall, that circuit produced a sound that was a little muffled. When I cut the resistor back to 5 ohms, I got some "shout" in female vocals that was disagreeable, and overall the sound was a bit bright.

I'm listening to them now with a 2.75mH/6ohms. Pretty good. Not bad at all.
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Old 26th May 2004, 06:17 AM   #8
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Default Duh!

Oops. Too late to edit the last message. I've had a major forehead-slap incident. I did the unthinkable. I changed two things at once: I hooked up the subwoofer, and I moved the main speakers nearer the wall.

I found the problem. It had nothing to do with moving the speakers closer to the wall. I was using the high level output from the subwoofer to drive the mains. I had failed to notice that the amp comes equiped with a "built-in 6dB high pass filter" - translation: a couple of electrolytic capacitors. That's what was causing the shouty sound. It was distortion in those caps. Now I'm driving the mains directly from the main amp (Rotel RA-02), and it sounds just fine.
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Old 26th May 2004, 11:38 AM   #9
sreten is offline sreten  United Kingdom
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There is some mileage in adding a parallel capacitor
to your BSC circiut to boost the extreme top end.

I'd say ~ 1uF to ~ 3uF but as ever set by ear.

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