Robert_J

If you go with an 8ohm sub, the drop in power is around 1db if the subs have the exact same sensitivity. If you get a more sensitive sub, then your should should be a little louder. Also, a 4 ohm sub shouldn't present a problem to the amp. All subs have a natural impedance rise across their operating frequency. If you measure the impedance at the sub's free air resonance, it can be as high as 50 to 60 ohms.

Buy a quality sub. If you want piece of mind, choose an 8 ohm model. If you don't mind modifying your deck a little, the TC7 that I mention in my linked thread would be great.

-Robert

1996LS400

Hey Robert, thanks for trying to decipher the Chineese for me.

I think for my first attempt at it, I'll drop a quick 8 ohm sub in there from Kicker. Can you look at the specs for me and tell me how you think this one would work.

The sensitivity you mentioned is dB1w/1m (whatever that is)

Frequency Response 30-500

Speaker rates at 200w peak / 100w RMS kicker says knock the 100 in half for free air, so that would be 50 watts. I'm sure the Nakamichi amp puts out more than 50 watts, but if I go 8 ohm, maybe it will be safe or close.

I think I can get the sub here locally with a 30 day return policy, so not too much to lose.

Robert_J

All speakers posted wattage rating is the thermal rating. That means the voice coil can handle a 1khz sine wave for a specific period of time (like 1 hour) without melting. That spec is almost useless unless you are going into an SPL contest and want to burp your system. Almost always, your sub will reach its mechanical or linear limits with lower wattage. Like I mentioned earlier, when a sub is mounted in the deck, there is no air spring to control the cone movement. It is now controled by the suspension (spider and surround) and the magnet's interaction with the voice coil.

I could go into more detail, but I already covered everything in another thread. Please read my posts concerning Fs (speaker's resonant frequency), xmax (linear excursion) and xmech or xsus (a speaker's maximum excursion before the suspension or something else stops the cone).

I don't mind looking at the specs, but you need to post the important ones like Qts, Fs, xmax, etc. Those are the Thiele-Small Parameters. Another useful page is How a Speaker Works.

-Robert

1996LS400

This could be a good thing for other members if it works.

Robert I was able to find a PDF on the specs for the Kicker Comp C8. Can we peek at it and let me know what you think?

Robert_J

The Kicker will be great replacement if you decide to stay with the factory amp. In the graph below, with 30 watts you can drive the sub to full excursion at 30hz. The frequency roll-off is very nice and the natural cabin gain will fill in the lows nicely. You should get about 100db at full power and that is very respectable for a factory stereo.


If you decide to go with an aftermarket amp, I modeled the TC-7. With 250 watts of power behind it, it reaches maximum linear excursion at 30 hz while producing a max of 106db. It never reaches it's mechanical limits so you can't destroy this sub with this amount of power.


In both cases, this program is estimating output in an open area at 1 meter distance. So the 100db and 106db are very conservative estimates. But since they are being compared under equal conditions, you can still get a good comparison between two different subs.

-Robert

1996LS400

Damn... graph and all! To bad I can't tell what the heck any of that means, but I'll take your OK on the stock sub replacement for now.

I really appreciate you going above and beyond. If I'm not happy with the quick sub replacement, I'll go with that other sub you've been talking about. Thanks a ton Robert!

Robert_J

It means the 10" the will play at quite a bit louder and provide deeper bass but requires an aftermarket amp to perform.

If the Kicker doesn't perform to your expectations, then the same company I mentioned earlier has an 8" model that will also work. If you reall want to go all out, there's an overstock 10" that would be killer. It would require some additional bracing on the deck though.

I know it may sound like I'm pushing TC Sounds products, but I'm not affiliated with them in any way other than being a very satisfied customer over the years. So much so, that I'm upgrading my home theater subs with a pair of 15" TC-3000's and a very nice 2,400w amp.

-Robert

1996LS400

Sweet! I'll post back and let everyone know how it works out.

akxx

iTrader: (1)

Robert_J: what happens when you run a 4ohm sub off the stock Nak sub amp from a 1990 LS4, which I believe drives a 2ohm sub?

Robert_J

Your new sub receives less power than the factory sub.

-Robert

dashan

Expecting your post back.

Neofate

iTrader: (1)

ROFL -- Only been a year now.

Good thread though,.. good info. My second modification is going to be an aftermarket sub to my stereo. Already put in the Alpine head unit. I'd like to go free-air/IB with an aftermarket amp -- Then take precautions to prevent any rattling whatsoever.

If I were to go with something like this other guy was,.. Robert.. Would I need to do anything extra to prevent rattles? If so, would I need to dynomat, or would a sufficient 'brace-housing' for the Sub work?

Thanks

dashan

Has any one ever put a 10" sub in the OEM hole of 96 LS400 rear deck without metal cutting?