I have a '90 LS400. I want to change my stock sub and DO NOT want to get involved in aftermarket amps. My stock sub is shot. I'm pretty sure it is an 8" 2ohm single voice coil. I have had difficulty finding an aftermarket sub with these specs that are free air compatable. I should be able to get a 4ohm double voice coil and wire it in parallel which would essentially read as a 2 ohm speaker. Is this correct? Also, any recommendations on wattage (RMS). I do not want to get a speaker that requires alot of wattage to drive it because I know the stock amp doesn't put out all that much.

 

Since you have a stock system, you may want to worry more about matching speaker efficiency and not so much about matching the impedance, and you don't want to present an impedance that's too low to the stock amp, you might want to be extra sure before you get something that's 2 ohms. If you're not doing SPL contests, a 4 ohm single voice coil sub may do the trick and be a bit easier on your amp than what you're suggesting, provided you can get close to what's in there in efficiency. The same also goes for a 4-ohm DVC as you suggest, even though you've supposedly matched impedance, if the efficiency doesn't match, you'll have to compensate for it elsewhere in the system (bass level control). Have you tried getting a local dealer to just temporarily swap in a couple of different subs to see what you get, just to get an idea? Assuming you only have one set of leads going to your sub, a 4 ohm SVC that's relatively efficient would be something to try.

 

I'm a little unclear on what you mean by "speaker efficiency". If you are referring to RMS, that was part of my question pertaining to the stock sub. My intention is to try and replicate to specs of the stock sub so I will not do any damage to the stock amplifier. Which is where impedence comes in. It is my understanding, and correct me if I am wrong, a higher impedence speaker, in this case 4ohm, would damage the stock amp which is rated at 2ohm. Does anybody have an idea what the specs are of the 8", 2ohm stock Pioneer sub?

 

I think I get it. I've done some searching and it seems all the aftermarket subs are running 10 or more db's below the 98 quoted above. What happens if I install a sub with lower db's?

 

Look man, no need to talk down to me. No s**t if I install a less efficent speaker it is going to sound like crap! Do you even know what the efficiency rating of the stock sub is? The way I read it now, you just picked 98db out of the sky! I appreciate your input and knowledge, but if you are going to talk down to people you can stick it!

 

You know... I agree... Have fun...

 

Go to wall-mart and buy a POS pioneer 8 inch sub, you'll think its stock again, but not blown.

 

Using a speaker of a higher impedance will not harm your amplifier. Using one with a lower impedance that your amplifier is rated for could do. You should make absolutely sure that your amplifier is rated for 2 ohms before fitting a 2 ohm speaker.

My GS has a 2 ohm sub, so you are probably OK.

Sensitivity figures are meaningless when talking about subwoofers. What determines the efficiency is the design of the driver (res. frequency, magnet size, cone weight, etc.) and the box that it's in. Quoted sensitivity figures are only relevant for midrange frequencies. Only by using the correct enclosure design will you be able to extend that sensitivity down into bass frequencies.

You won't lose that much by going to 4 ohms. You could compensate for any loss by fitting a larger driver - a 10 inch, for example.

If you are just looking to replace the stock driver with something less extortionately priced than a Lexus replacement, most free air 8's will do the job because Lexus drive units are basically crap. I am assuming that the 8" on the LS is a free air design (mounted on the rear shelf and firing into the trunk). If it is a free air design, make absolutely sure you get a free air woofer. Standard woofers are too overdamped and will kill the bass.

Stevie

 

Stevie - Thanks for the info, it will definitely help in my decision of which speaker to go with.

 

Did I miss something while I was away, or is my browser wacked? :-) Where did the 98 dB come from, and who picked it out of the sky? Who is talking down to you?

 

My stock sub was also shot when I got my 90 LS.

I purchased a cheap aftermarket sub and popped it in there, but couldn't deal with the weak power and rattling from that metal mount.

So I bought my friends 15"'s and removed all the rear subwoofer components (woofer and mounts) and what a great improvement!

lol..

 

98 was out of the sky...and he was asking for help but thought my (now self-deleted) posts were condescending. Don't try to figure it out....I wasted too much time trying..