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Discussion Starter #1
Okay, so I finally got my Nakamichi HU installed - I gave up and took it to a specialist in the area. It works, most importantly, and they didn't mess up the stereo or dent the car so I'm happy. But I noticed the sound from the factory sub is no longer the same, the stock factory head unit produced ONLY low frequency sound from the sub, whereas now I can hear mid-range sounds leaking into the sub's sound.

The work order says the installer wired the sub to a non-fade output on the deck. So, what exactly does that mean? Is there a practical way for me to "filter" out the higher-frequency sounds from the factory sub? Sorry this is probably painfully obvious to most but me not know much about car audio... [8]
 

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A non-fade output is an output that cannot be faded to either the front or the rear. Most sub outputs from an HU are non-fading.
 

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Discussion Starter #3
Okay, well that makes sense then. What I don't understand now is the "leaking" of the higher-frequency sounds. If the sub is hooked up to the sub output on the HU, shouldn't it be "filtered" so that only frequencies low enough for the sub are going to it?
 

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It may be a full frequency output. Or, the installer may have bypassed the crossover in the sub. Where is the crossover for the factory sub ?
 

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Discussion Starter #5
guerro said:
Where is the crossover for the factory sub ?
I don't know. I suspect that it was (is) built into the factory HU. The Nak HU has a dedicated sub output, but maybe the installer didn't connect to that... Some day when I have more money I'll probably just go back and replace the stock sub anyway.
 

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Well, the sub isnt going to last long playing full frequencies. Might be okay as long as you dont turn it up to high.
 

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sa_pyro_ne said:
playing frequencies over 120 hz is generaly harmful to the sub
Why would this be harmful to the sub?

It would only use up extra power and not sound right.
Playing lower frequencies in tweeters could be harmful though!


The stock head unit's sub out is extremely filtered from higher frequencies, so the stock sub amp probably has no filter for highs and relies on the head unit for it.

Maybe the Nakamichi deck's crossover is adjustable, check the manual.
 

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playing higher frequencies than the sub can play is very harmful actualy. the frequncies it can't play are "used up" by giving it off as heat on the voice coils which can fry them, also, more distortion is created when playing those frequncies around 140 that are border-line that it can sort of play, and distortion creates heat, that why you should never play a sub over 120hz.

- Scott
 

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Discussion Starter #10
Huh. Sounds like I might want to fix that soon then. I had already started looking at the F-Mods, I think that would do the trick. Is there anything else that I could use to do the job, like instead of an inline crossover? The sub out cord is RCA, but I can't see the end of it, so I don't know if they cut the RCA plugs off to tap into the wires or what - the factory sub connector was (is) most definitely not an RCA connection. I don't think the deck has any kind of crossover or filter built into it?
 

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I doubt the stock sub amp has enough power to do any damage as long as it isn't being overdriven constantly.
I would however be concerned by how it sounds. Your installer "specialists" should have done more to let you know of any problems and/or limitations of using the existing factory sub with an after-market HU.

Call them and ask them to fix it or give you some other options.
 

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if there isn't an rca for it then you need to use a different crossover, the fmods are only for rca's, they plug right into them. for this i'm not sure what you'd use, i don't know if you could use smething like http://www.partsexpress.com/pe/showdetl.cfm?&User_ID=15520651&St=2600&St2=76656221&St3=79434715&DS_ID=3&Product_ID=6741&DID=7 because it's just a signal and the impedance is definately not 4 ohmm it's more like 50 ohm probably, so it'd make the crossover point way higher. (could be wrong) i'll ask around and i'll have an answer for you tomorrow morning.

- Scott
 

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Discussion Starter #15
Uh-huh. This is starting to get complicated. I'm going to ask them about my options this weekend, the shop is near my weekend job. The simplest option seems to be the F-Mods which I'm sure they either have already or can get ahold of.

DidHeFocus?, you said this:

Your installer "specialists" should have done more to let you know of any problems and/or limitations of using the existing factory sub with an after-market HU.

They could have I guess, but they were pretty much doing what I told them to do, which was finish the installation I had already started. I probably should have told them to warn me about any complications, I think they interpreted the fact that I was doing the installation as meaning that I knew what I was doing. [rolleyes]
 

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Discussion Starter #18
sa_pyro_ne said:
well you can't od the fmods if there aren't any rca's. the low pass crossover that i linked to is your easiest solution. just wire that between the speaker and the amp.

- Scott
Well, see there are RCA's from the head unit, it's a short little wire set that has one end RCA's and and one end a teensy little micro connector. But I haven't poked my head under the dash yet to see how they handled that. In other words, they may have utilized the RCA connectors, or they may have cut the connectors off and used something else like a butt connector.
 

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ic ic, then the fmods might work, for the fmods they just plug right inline with the rca though, you don't cut anything. and i wouldn't suggest cutting rca lines either, rca's don't fair to well after being cut, you can lose alot of signal quality.

- Scott
 

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Discussion Starter #20
Okay well, talked to the shop. They sold me a big ass heavy coil of solid-core wire and told me how to install it, but it made little difference (they said it was equivalent to a 120Hz crossover). So, I took it back and now they're ordering me some other ones, 80Hz and 70Hz. I'll have to try those and see, the one they gave me still didn't block enough frequencies to keep out the midrange sounds like vocals and piano. Sounds like ass if you open the hatch and listen to the sub. Sounds okay if you are sitting in the driver's seat though.
 
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