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Implementation of Fostex FF85wk
Implementation of Fostex FF85wk
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Old 23rd February 2021, 04:53 PM   #21
KCHANG is offline KCHANG  United States
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Hi Vix,

That's as big a set of balls as I am willing to have.

The main reason for size of the balls is that it allows the baffle step attenuation f3 to be around 200 Hz, where the bass modules take over.

Kurt
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Old 23rd February 2021, 05:19 PM   #22
KCHANG is offline KCHANG  United States
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Quote:
Originally Posted by planet10 View Post
Have you tried with the woofers closer to the FF85?

dave
Hi Dave,

That's a good question, and the main concern I had when I was building the system.

My design constraint was that I wanted to use those bass modules, which I have been using for >20 years as the "foundation" of various speaker projects, and I had no intention of building a new set of bass modules. The resultant center-to-center distance between the FF85wk and the upper woofer is around 27.5" (31.5" between the center of the FF85wk and the mid-point of the two woofers). This is of course a large distance.

I try to ameliorate the issue by doing two things. First, the crossover frequency is 200Hz. Second, I listen to the speakers from ~10-12 feet away. So far, I have not noticed a problem.

Kurt
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Old 23rd February 2021, 05:43 PM   #23
Bigun is offline Bigun  Canada
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Implementation of Fostex FF85wk
Kurt, I suspect Dave is suggesting that you simply turn the bass units upside down.
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Old 23rd February 2021, 06:01 PM   #24
KCHANG is offline KCHANG  United States
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Ah, I did not think about that. It is actually a good idea. I'll give it a try.

Kurt
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Old 23rd February 2021, 06:08 PM   #25
planet10 is offline planet10  Canada
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Implementation of Fostex FF85wk
The large size has the advantage of pushing the 2π to 4π transition, it also makes centre-to-centre larger resulting in (ideally) pushing the XO down in frequency.

To be more specific, the first thing i would look to in that system is to flip the woofers around do they are closer to the FR, and i would trim the paper mâché down so that the woofer box can be imbedded into the sphere.

I would suspect centre-to-centre could be halved, allowing for halving of the XO point while still maintaining the magic quarterwave distance.

dave
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Old 23rd February 2021, 06:12 PM   #26
planet10 is offline planet10  Canada
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Implementation of Fostex FF85wk
Quote:
Originally Posted by KCHANG View Post
The resultant center-to-center distance between the FF85wk and the upper woofer is around 27.5" (31.5" between the center of the FF85wk and the mid-point of the two woofers). This is of course a large distance.
You need to maesure to the middle of the bottom woofer.

Guess about 36”. Suggests an XO less than 100 Hz to mauintain the optimal spacing. If that could be halved, you XO point would be close to perfect.

dave
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