Hello all! I own a 1992 Lexus SC400 with a Nak Premium Sound system.

I am having troubles with the sound system and was wondering if all of you could give some input if you have any experience with sound systems etc.

My symptoms/problems are:

3 Speakers are not working anymore. (The front drivers side, the rear two on the shelf) The 2 tweeters and 1 sub is still working.

One day when I was driving, all three speakers just cut out. I can hear a VERY FAINT noise coming from them, but that is all. If I fade the speakers to the rear, I get nothing.

I don't think the speakers are blown because if they were, I would be getting a very POOR quality sound. But I am getting no sound at all.

From reading the posts I am getting more of an idea on how my sound system works. And what it is comprised of.

From what I read, my car has the Nak sound system which is comprised of:
4 Speakers (2 Door - 2 Rear Shelf)
2 Tweeters (2 Door)
1 10" Sub (Rear Shelf)
1 5-Channel Amp (Under the 12 CD Stacker)
1 12 Disc CD Stacker

Could anyone verify how many amp(s) I have, where it/they is/are located? Thank you! I would just like to make sure I know what I am doing before I start to rip the interior out of my car

Possible Problem?

I think that my sound system has the 5 channel amp and 3 of the channels have blown.

What do you guys think?

Testing?

How would I test the amp to see if the channels are blown?

Rear Seat Removal:
Also to take out the rear seats, do I need to removed the front seats as well?

THANK YOU ALL IN ADVANCE!
Michael

I'm pretty sure your speakers are blown. There are various ways to blow speakers. You can tear the surround from the diaphragm, you can freeze the voice coil, you can tear the cone, if it's a peizo, you can cook the cooling fluid. Depending on how you blow them, they will emit different types of distortion. If you've fused the voice coil to the magnet structure, you will hear a very faint, almost inaudible sound. This is the sound of a struggling voice coil trying to resonate.

As for the amp, I'm pretty sure there is only one amplifier, which suggests that it's a 5-channel amp. Most amps under $1000 (especially 5-ch amps) are monoblocks with a secondary transistor stage that divides the power into any of a number of channels. This means that if you had an internal problem with the ampflier (other than bad connections), the whole amp would completely die and you'd get no power to any speaker.

Your best bet is to remove and replace all speakers. Any *quality* aftermarket speaker will sound way better than OEM. While you're removing the blown speakers, you can locate the crossover inside the black box it's housed in, and connect it directly to the input terminals to test the sound directly. (Since the amp is sending power to the tweeters at least, that means it is sending power to the input terminals.)

The chance of all those speakers fusing at the same time is pretty small. Was the music really blasting when they went out? I would check the plugs into the amp. My factory Nak system has been completely replaced, so I don't remember much about it, but maybe there is two plugs into the amp and one has shaken loose.

Do you have the factory phone installed? When I purchased my new SC (used) the dealer mentioned another SC in the shop with the same exact problem!!

I have the same problem with driver mid-range speaker and rear 2 speakers (not the sub) all blown.

I have taken working speakers out of my wrecked sc so I will test them soon.

If you've taken a good look at those speakers, you'd see they have very poor build quality by aftermarket standards (most OEM speakers are complete garbage anyway, but Nakamichi is slightly above the curve). It is quite easy to blow them progressively (increasingly so as they age) as I'm sure many Lexus owners have experienced. The materials used aren't optimal for durability and power handling. It's more likely that the speakers blew out than three selective channels of the amp----as the poster stated only the midrange drivers aren't functioning (the amp doesn't discriminate by frequency band or speaker drivers). This arguement also correlates to the 'loose wire' theory. Also, the only way for a five-channel amp to lose only three or so channels at a time is the result of a cold solder (which is just faulty wiring at that point). If Nakamichi car amps are anything like their stereo amps circa 1980, they aren't cold soldered (although the company has gone way down hill in recent years).

Hey guys thanks for the replies! I remember a while ago I posted in this forum and I had not one reply! Its great to see this forum growing with as many people helping as there are asking questions!

I actually bought the car from my friend because he was moving. When I got the car from him the rear speakers were already blown. And then a few months later I was listening to my music rather loudy and then it kinda "cracked" then my drivers door speaker did not work anymore.

The weather is really cold here now and my garage is not big enough to be working in so I will wait a few and take out my back seats and update you all!

Again, thank you very much!
Michael

I also have another question. But first, I know next to nothing about sound systems and installing the new speakers will be a FUN challenge.

I was wondering what the mounting depth is in the Lexus and if there is a restriction on how deep I can go. (Is there something blocking it?)

Also, most of you have fit 6 1/2" in your front door trims. How exactly is that done? I have heard that I need to remove the old speaker housing and make a new one out of MDF and mount the 6 1/2" on that. But where do I mount the MDF?

To also preserve the speaker life, I have read but forgot, that some people spread a thin layer of... PVC...SVC??? I totally forgot what it was called but does anyone know what I mean?

Bizzy, that was my post you recall reading, from about a month ago. What I said was, whenever I buy a new speaker, I usually take some DOW CORNING® RTV SILICONE SEALANT and spread it lightly over the entire exposed foam surround - that seals that side from the air and makes the foam last much longer. The only drawback is the RTV is too thick to be applied with a brush, so it is hard to get a smooth, attractive surface (of course, hidden by the grille, who cares?). Also, the addition of RTV will slightly thicken and stiffen the foam surround assembly, altering the Q and VAS (or something like that) properties of the speaker and theoretically affecting its sound. But in my experience it is not altered to the point I can hear it, and besides, a rotted surround sounds MUCH worse! My priority is to make the speaker last as long as possible. If your speakers have any sort of warranty, you might want to wait till the warranty period is over before doing this, since "modifying" your speakers with RTV might void the warranty.

RTV silicone is available at any hardware or auto parts store- they are sold in toothpaste-like tubes, or cartridges that plug into calking guns.

Here is the post, in case you are interested:
https://www.clublexus.com/forums/sho...290#post200290

The stock speakers may use organic/synthetic foam surrounds (very popular in the 80's), but very few aftermarket speaker companies still use a foam surround for their speakers. The common material used today is a santaprene and butyl rubbers for their similar properties to foam, yet drastically longer shelf life. Foam in speakers will dry out and deteriorate within 5-10 years of manufacturing as many have already discovered. Today, you'll only find them in cheaper speakers (like Bose), but they do have their utility in subwoofer surrounds (more flexible than rubber for improved tightness). Since service track records reveal that most people blow their subwoofers in a period of 3 to 5 years, this shouldn't present too much of a problem. Also subwoofer foam is much thicker, thus takes a bit longer to fall apart.

Anyway, my point is don't put any silicone sealant over a rubber surround. It'll only serve to make the midrange driver stiffer and less responsive resulting in a bright and sometimes tinny sounding speaker. Silicone may also affect the foam surround's performance (I don't know cause I've never tried, but it's my theory). The best solution is to avoid foam by all means.

How about a think layer of Vaseline?
That would surely keep it moist!

I was also just wondering, when I removed the seat backing in the rear seats. (The part that is bolted down) Do I have to removed the front seats to take out the rear backing?

Thank you!

Its a nice day outside today, I might give it a shot.

On second thought, maybe I won't reply with what I was going to.



heh

SR

Hello!
Okay, I just did the dirty work and it took me about 2 and 1/2 hours.

I took both rear speakers out and they APPEAR to be in perfect shape, other than some slight discolouration in the centrel. There are no gaps or cracks.

Is this common with blown speakers?
How could I test these speakers to see if they are working?

I also checked the fuses and they are all in working condition. Are there any fuses on the amp under the 12 CD Stacker?

I am very stumped, I can't figure out what is the problem! Blowing the 3/5 channels of the amp is very highly unlikely... And it does not appear that my speakers are in bad shape. What else could it be!?

Please help, I am going to go insane!

Micahel

lex400sc

I read your post again, and I was just wondering what that would look like, if i fused the voice coil to the magnet structure.

I took my speakers out and they look fine. There is no abnormal concavity etc...

Thank you!

To test a speaker, I hook it up to an amp that I know is working and listen to what happens.

To test an amp, I hook it up to a speaker that I know is working and listen to what happens.

This used to be harder back in the 80's, when my home speakers were the size of microwave ovens, and I had to lug them out to my car to test the amp. Now that (most) home speakers are smaller, the ones I lug out are likely to fit in my trunk!

And since your speakers are already removed, you can bring them inside your home and find a stereo to hook them up to.