Hello,
I have an 85. I am not sure what I want to do with the stereo. It is the one with the tuner, tape, and EQ so it is a big space. I like the way it integrates into the dash and looks like it belongs, but I am also aware that it sounds terrible. I'm sure in 85 it was fine, but by today's standards...

I put some new speakers in the rear and decided to "bridge" the amps to the rear and forget about the front speakers for now. They are supposed to be two 25? Watt Clarion amps (which probably means 12.5 per channel, which means more like 9.) I figured if I could get around 20 to the pair they would sound better and my front speakers are blown anyhow.

I did this by essentially splicing the speaker wires together. Left front now hooks in with rear left and so forth. It seems to work, but it occurred to me later that it might have been smarter to let one amp do the left and the other do the right rather than "combining" the two. That's my question.

Feel free to call me a moron if need be. I just want to know if it makes a difference how I join them together. It's not an ideal situation, but it will serve until I make a decision about the head unit.

Thanks,
matt

 

It makes a difference for a couple reasons:

When you combine speakers electrically, you change the characteristic impedance (or load) of the circuit that the amp is driving.

Having the load mismatched to the amp will cause distortion, and can in many cases cause the amp to burn out.

If you wired the speakers in parallel (both speaker positives connected together, and both negatives together) you have reduced your impedance by half. Which doubles the power draw of the circuit, & can cause the amp to fry.

If you wired them in series (positive from the amp to the first speaker, first speaker negative to second speaker positive, then second speaker's negative back to amp, you've doubled your impedance. You're less likely to damage the amp, but you'll get far less volume at the same volume setting, which will cause you to up the dial and run the amp at higher settings than usual.

Proper way to do it is to use a matching transformer.

If what you are saying is that you combined the AMP outputs, so that two amps or two channels are driving one speaker, that's a recipe for disaster unless the amps are designed with isolated outputs.

 

I'm using the original stereo and amps with new alpine type s speakers and the sound is really good. I didn't mess with the amps at all.

 

Those stereos were pretty top o' the line back in the eighties and can still sound
really good with new speakers.

Go get yourself some Wally mart special 4" replacements for the front speakers
and undo what you did with the wiring and try it out.

My SA sounded terrible with the OEM speakers but once I did this I realized how
good it actually worked. I then add an aux cable to plug into my ipod and now it
plays my ipod with no problems. I'm not sure you can do the same but it wouldn't
surprise me if there weren't some extra inputs on the head unit or somewhere
so you can add an aux cable in some way.

 

I agree, new speakers will make all the difference. Chances are that the specs on any amp you buy today will not be noticably better than the Clarion. On the other hand, speaker materials degrade over time, particularly in the harsh environment of an automobile. Resatore the wiring and spend some money on good speakers first. If you are still unhappy with the sound you can upgrade the amps then.

 

I suppose that this is what I've done. I should probably undo it, then. I knew there was probably a reason why I shouldn't do what I was doing! Thanks for the explanation.

 

I did replace the rear speakers with component Alpines, and that's what I was unhappy with. There are some possible explanations, though:
1) The amps aren't putting out enough RMS power to drive the speakers correctly (the OEM speakers are rated for 5 watts, with 25 watts maximum, which is far less than the Alpines.)
2) The speakers I bought suck (but as Alpines you would think they couldn't suck that bad.)
3) The speakers did not come with a crossover. Maybe that's messing up the sound.
4) Maybe there is something wrong with the amps or wiring.

That was the reason I tried to hook the amps together, to get more power. Of course, after reading some of the other comments I plan on undoing it! Maybe like you said some front speakers would help fill out the sound.

 

Another problem I have is the analog control of the radio. It seems to "drift" a lot as I drive and have to constantly re-tune it. I also think that the after-market antenna isn't very good. I want to replace it with the original power antenna. The cassette could probably use a good cleaning, too.

 

Using a can of dust-off to carefuly blow the dustbunnies out of the guts of the tuner (esp the tuning capacitor, if it's not sealed) may help with your drift issue.

 

I'm not sure I agree with this, though I get your point. Those Clarion amps were 25 Watt. I am going to guess that is actually 12.5 X 2. In 1985 that still would have been a lot of power. But Clarion rated them, and companies usually over-report power. That would put them, my guess, at a little over 10 watts per channel. My new JVC (in another car) is independently rated at 20 Watts X 4, so each speaker is getting 20 watts RMS with much higher peaks.

I think this is supported by the OEM speakers, which are rated for "5 Watts, 25 max." They weren't meant for much power (by today's standards) even at peak. I suspect that the alpine component speakers were designed for a much higher RMS power and so I'm just not sure I've got the power I need to get a good, clean sound.

I know that RMS power is not the reliable way of measuring things these days, but the point remains the same.

Of course, my knowledge of such things peaked a long time ago. I could be out of my depth in such an assertion. It just seems to me that in 1985 when I would see car stereos advertised they would be about 3 Watts and that was cool. The RX7 with 12.5 would have been "da bomb." Even though I'm not certain I agree with you, I still appreciate you taking the time to comment.

 

i ditched all that old stereo stuff(didnt have it to begin with ) i custom modified the center peice for an aftermarket pioneer stereo deck with ipod hook up and all the extras like satilite and blah blah.....

i wire the speakers right off the deck the two rear ones and two new front ones
sounds amazing

its even better with extra sound deadining stuff in the rear and under bins, basically under everything makes a better quality sound

-kyle

 

Ophelious,

I had terrible reception issues with the stock stereo. Replaced it with another stocker, same issues. Tried several different antennas, some amplified, no improvement.

Then, when removing the 2nd stock unit, I found that as long as the head unit was not touching the metal framework that it mounts to, I had awesome reception! The moment it came into contact, aweful.

I never did figure out what that meant. I bought a high dollar HD radio and had it professionally installed, and now I get "useable" reception. Just barely useable. I should really figure this out one of these days, because I can't even listen to HD stations in my own city due to the reception issues.



.

 

Mark, sounds like some sort of ground loop or something. Check all your grounds.

 

As it happens, I posted a photo of the 1984 brochure for the premium stereo a while back. You can view it here:

https://www.rx7club.com/showthread.p...ght=iowa_hawk1

It states that the system had 100 watts over four channels or 25 watts/channel. The system did not lack power, it lacked high quality speakers.

My recollection is that when you look at speaker power ratings the first number is the nominal power required to drive the speaker to a reasonable listening level. The second number is the maximum power you can safely feed without melting the voice coil. If you have highly efficient speakers you need less power to drive them to loud levels. to compare speaker efficiency you need to look at the Sound Pressure Level (SPL) which measures db at a distance of one meter from a speaker driven at 1 watt. Higher numbers = a more efficient speaker which requires a lower power amp.

Regarding my comment on specifications, I was refering to distortion specs, not raw power. Even in 1984 car amps were available that delivered hundreds of watts of power. While today's amps can deliver awesome power, I doubt that there distortion specs are much better, if better at all, than what was available in the mid 80's.

Finally, it may be that by only replacing the rear speakers, you have made an improvement in the lower end of the sound spectrum. The high frequencies are more directional and the front speakers may well be biased toward the high end. You will certainly be well served by replacing those front speakers with a high efficiency speaker. If that brings no improvement than I would start changing the electronics.

 

Plus, if you shop smart, good speakers are both cheaper and easier to change out than are amplifiers.

 

You know the funny thing is that I came here to post on this topic and you beat me to it! I was going to say that you're right...I saw that brochure (maybe the very one you posted, without knowing it) and I saw that they are claiming 100 Watts total power. Even taking a little fudging into account that still puts it on par with what's built into most stereos today.

I'm really beginning to wonder if a crossover is the problem. The Alpine component speakers I am using didn't come with one, and I thought that was odd. Maybe I am not getting good sound for that reason. The speakers got good reviews so I am confident that they SHOULD sound nice.

Another reason is that I'm not getting a great "tune" with my tuner. It seems to drift a bit (it's the old analog type.) Oddly enough, I have the optional eq. The person who ordered the car added the eq but kept the analog tuner. I've gotten some advice to give it a good cleaning but I am also skeptical about the aftermarket antenna.

Couple that with the fact that I have only found a few 25 year old tapes to test the deck with, and that it probably needs cleaning, and I just haven't been able to get a good sound. The Alpines sound better than the stock speakers, but ironically they sound a little WORSE because they are making me more aware of the sound distortions.

Anyhow, I had just popped on here to eat a little crow and let you know that I underestimated the Clarions. The 85 Renualt Alliance I had only came with an AM radio, and the 85 Mercuri Capri my dad had still had an 8-track! It was hard for me to believe that the factory Rx7 had so much power. Kudos to Mazda!

 

You shouldn't need a crossover unless you're running multiple speaker drivers off one channel. Purpose of a crossover is to match the speakers to their center frequencies (and match impedance).

 

The Alpines I have have a separate tweeter. The tweeter connects with a second set of speaker wires, but they connect to the same terminals that feed the larger driver. I just wonder what is keeping the bass signals from going to the tweeter and how much distortion this might cause. Any thoughts?

 

If the woofer and the tweeter elements both come pre-connected to the same pair of terminals on the speaker itself, there's no way to put in a crossover without modifying the speaker.

Either the tweeter driver has a built-in high-pass functionality (no response below a certain frequency - - many ceramic tweeters work this way) or they're just not a very advanced design.

 

DD, he's using a component speaker setup in the rear of his car.

 

I realize now I've been a dummy. I like to do first and think second. I was looking at the packaging and it says "built in crossovers." Sounds good, but it turns out that "built in" means a little connector that's in wire. I thought that this was just a splice (I bought the speakers second hand) and took it out. It just looked like something you'd use to cover bare wire. Apparently it's called a "network?" Anyhow, I took it off because I thought it was just there to add more wire. Dumb.

So anyhow, I went and bought a couple of "bass blockers." I suspect they'll do the same thing. I would think that the "woofer" part would have something similar, but it doesn't seem to. I suppose it's more important on the tweeter anyhow.

So today I have to undo the wiring ****-up I did with the Amps. Then I have to install the little bass blockers on the tweeters. Hopefully that will make a difference.

I now have a pair of stock speakers if anybody wants them : )