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Old 8th April 2009, 12:39 AM   #1
jaencer is offline jaencer  United States
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Default f120a in DBR is done and :-/ better alternative?

Dear more knowledgeable audio fellows,

I have recently purchased a pair of F120A drivers. I did some research to find a cabinet for them, but they are not very well documented by DIY builders. Fostex doesn't help much either, but they do give simple BR plans. Because the FX120 and F120A are so similar, I built the fostex recommended FX120 DOUBLE BASS REFLEX cabinets for my F120A. The cabinets were built very carefully, and came out exactly according to the plans.

But.

I have listened for a couple weeks, given the drivers a chance to break in, and they sound a bit congested and stuffy. Good still, it really isn't bad-- better than what I was using before-- but I have a sneaking suspicion that they could do better.
Bass isn't really a priority, I just want clarity. They are also near field, so doesn't have to be loud.

I know ppl will recommend a fonken-style box, but that looks HARD and I'm no carpenter (plus i'm broke after buying the drivers).
The recommended bass reflex, sealed, or open baffles seem like better candidates.
What would you build?
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Old 8th April 2009, 04:05 AM   #2
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Since you say "bass isn't really a priority," I would personally mount them in some OB's at least temporarily while you search for other enclosure options.

The bass will be light, but there's a certain raw purity, and anyway, it's just a temporary way to listen to them. I don't think two weeks is anywhere near enough break-in time for most Fostex.

Are you aware of the normal break-in regimen? (Wired out of phase, facing each other, for maximum cancellation, playing loud to stretch the suspension, covered with heavy blankets?) Some people do /that/ for two weeks. If you listened to normal music at normal levels for two weeks, it probably wasn't much of a real workout.

Good luck and keep us posted!
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Old 8th April 2009, 05:51 AM   #3
jaencer is offline jaencer  United States
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thanks!! the break-in has begun... will update in a week about this issue
(and wow, LOTS of fostex break-in time, i wonder if that means they'll last a super long time)
(hofefully the box will turn out to sound good :fingers-crossed:
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Old 13th April 2009, 03:52 AM   #4
kmaier is offline kmaier  United States
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Default break-in

For my F120A drivers, I did some break-in time on the bench driven with a 1.5-watt tube amp and a sine generator. I ran them for a couple hours at rated Fs (65Hz) with 1V (RMS) signal, then repeat at 2V, 3V and 4V levels.

Regards, KM
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Old 13th April 2009, 04:58 AM   #5
jaencer is offline jaencer  United States
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Every night since my last post, I just left the speakers in the workshop all night playing pretty loudly, with a different album each night on repeat. They do sound significantly better for that, but also because I have optimized a lot of other variables.
They sound best like 7 feet away (farther than I wanted but its worth it). Regarding volume level, it turns out that my SET tube amp sounds best with it if played at softer volumes, and my LM3886 chipamp (with tube preamp) sounds better at higher volumes. Actually, the chipamp will ONLY sound great at higher volumes, but I have no problem swapping the bananas plugs to the other amp when the music needs to be quieter/louder. But surely they belong in this cabinet after all, so no need for open baffles.
Attached is a picture of the DBR cabinets during construction. The white padding is 2" thick cotton pad, that has been roughly (intentional) ripped down the middle to make it 1" with one bumpy side. The wood is 3/4" birch ply.

EDIT: i'd like to add that the dynamic range is surprising. the bass, specifically, is enormous. While they do integrate with my 10" vented subwoofer very smoothly, there is really no need for it. The top end also kind of took me by surprise (my first full-range)- it doesn't need a tweeter.
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