Anyone ever use FMODS? - diyAudio
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Old 1st December 2002, 11:19 AM   #1
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Join Date: Oct 2002
Default Anyone ever use FMODS?

I've been thinking about using these in future projects and they seem like a pretty good deal. There cheap, passive (which my creek pre-amp proved is a very good thing), and from what I've heard you can stack them to get 24 db/octave slope.

The only other cheap alternative I see is the Marchand XM-1, which fully assembled is $60 a pair which is also 24 db/octave not including caseing. I've also thought about using a car audio crossover unit, because those are usually 3 way to start out with so expandability is always there.

Anyways I was just wondering if any of you have used the FMODS before and wether or not they changed anything.


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Old 1st December 2002, 04:36 PM   #2
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Join Date: Jun 2002
Location: NH, USA
I have used 100 Hz High Pass F-MODS for my car at 12 db-slope. Yes you can stack them to get a 24 db/octive slope just like with any x-over, I think. I'm not an SQ expert or great judge, but they worked fine.

Not sure what you're referring to when you say that they're "passive." Active reffers to whether they're adjustable or whether they go between the input signal and the amp As I understand it they're active x-overs, cause they go between the input signal and the amp.

Very good price also. I got them at for $15 with free shipping.
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Old 1st December 2002, 07:40 PM   #3
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Active means there powered. Which means they can give gain, but usually introduce some distortion or background hiss.
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Old 15th July 2004, 07:39 AM   #4
kspv is offline kspv  India
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Location: Bangalore, India
Default "As seen on TV"?

I was searching on the net for an external crossover device, and stumbled upon FMODs on Crutchfield. Initially I thought these are for car audio only. But the manufacturer's site,, says that these can be used in high-end home audio applications as well. They have referred to FMODs as "active crossover simulators".

FMODs are passive filters no doubt, as they do not use any independent power supply to do the job, but what makes the manufacturer liken them to active crossovers, is perhaps that they are added in-line before the power amplifier (work with line-level output of the pre-amp upto 10 V). According to the manufacturer, they cause no noise, no distortion, and no degradation in sound. There was no mention about phase alteration. The roll-off is supposed to be 12dB/octave, and they come in fixed values of high-pass and low-pass frequencies.

They have got customer testimonials on their website, which seem incredulous like most of those "as seen on TV" product testimonials. They even got one from Absolute Sound magazine.

Just what are these devices? Are they usable in D.I.Y. audio? How do they work? If things are so easy as FMODs, why is the world pulling its hair over crossovers? Definitely there is something untold here! Would anybody care to reveal the truth?
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Old 15th July 2004, 07:52 AM   #5
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To work properly, passive line level filters must be custom designed and built to match the output impedance of the specific amp or amps being used .

Here's how to design them
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Old 15th July 2004, 08:46 AM   #6
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Join Date: May 2003
Location: Ft. Worth, TX
You mean to tell me I actually registered Westrock2000 here along time ago!?!? It says that post was in January 2002, and I registered this account in May 2003.

This is so crazy, because on every other online place I use Westrock or Westrock2000 (even my webpage is Westrock Online), yet for whatever unknown reason I chose Hybrid Fourdoor for this site. And yet the West was here the whole time.

Haha, sorry this is just weird thats all. I was even interested in the title too, I was like hmm....ya I wondered about the FMODS before....
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