Wiring multiple speaker - please advise

I'm trying to improve the sound in my 87 MR2. It ain't an easy thing! Talk about no space! I've tried to make a box for an 8" sub, but it just ain't going into this car! So I've given up on that for the moment. What this car has: front dash, 2 4" Boston's. Integrated into the front channel is a factory sub. It ain't much but it does help. How it is wired I have no idea. There are 7 wires going into the sub box. There is a 4" sub in the box. For the rear channel there are 2 3.5" Boston's in the c-pillers, just about ear level. I've put caps on all 4 Boston's, 200hz on the front ones and 300hz on the rears. The deck is a Pioneer of some type 4x45watts. I keep blowing the rear 3.5 boston's! Now, what I did today: I found some old Pioneer truck speakers. TX-nn04 (sorry, can't remember what the nn was) These look like they could hold a 6x9. But there is something about 4" in the front and it is ported, and a small tweeter facing upwards. The car has a lot of base now. By no means booming, but I ain't after boom! So it is getting close to what I'm after. But with these truck speaker behind the seats I loose all mid and highs from them. So with only the front's producing high's and mid's it is still not quite complete sound. So now I'm thinking that I should add the 3.5 Boston's back into the rear channel. But how? If I wire them in series, then they get reduced to 2ohms ?? And this would double the power to them??? I'm already blowing the 3.5's If I wire them in Parellel they become 8 ohms??? and get half the power???? Am I totally wrong?? So, how should I wire them in? And if you could, could you give a brief explination of how to wire series and parellel, I can't keep it straight in me noggin! Thanks,Craig

The HU is DEH-P3100  and it is mosfet.   What is mosfet??? and what does that do for me?

BTW, those Pioneer truck speakers are TS-TRX40, if you were wondering.

Thanks again,

Craig

MOSFET amps do not "get more power to your speakers."  MOSFET amps simply tend to be cleaner (less distortion at a given volume level) than non-MOSFET car amps.

The DEH-P3100 is an older model with Pioneer's MOSFET 45 X 4 amp built in.  This produces about 19 wpc RMS and 45 WPC max into four outputs.  It is intended for a 4 ohm load and cannot be bridged.  If you run a 2 ohm load on this HU you run the risk of overheating it and blowing the amplifier outputs.

The setup you describe in the first message is really odd.  There is a factory sub?

MR2's are a royal pain as there is no room inside those things.  It sounds like your install is already so kludged up that if I was you I'd pull everything and start over.  Run the front speakers off the front outs of the HU.  Run the rear speakers off the rear outs of the HU.  Do not put anything in parallel or in series.  Use the single RCA out from the Pioneer and run a seperate amp to a subwoofer.  In the MR2 you can squeeze a sub behind the seats, under the passenger seat, or in the front trunk.  I have also fabricated an enclosure and put two 6 1/2" subs into the center storage area between the seats, but with only marginal results.

Good luck.

yes, there is a factory sub wired into the front channel.  it is a very small box.  It contains a small amp as well as a small 4" speaker.  I replaced the POS speaker that was in there with the best 4" woofer I could find.  Sadly that was a Radio Shack special.  And it is 8omh.  it is located under the driver seat.  Like I said it isn't much but it does help.

I found a 4" mid base speaker mail order that was 4omh.  The box says that it is supposed to be 4ohm.  So I figured I'd try the 4ohm as it should get twice the power (if I understand how that works correctly) it should be louder.  The 4ohm speaker was rated at 40watts.  Well it blew in less than an hour!  I don't know what the build in amp generates, but I guess it is addition to the 45x2 the HU produces?  There are 7 wires going in to this box, the front right and left + and -, power, ground and ??????

When I use the rear 3.5's the entire thing is using the factory wiring. And yes, I've blown two 3.5's  One was before I put the caps on, the other since.  They haven't cut out, just sound like the teacher from Peanuts!

Now that I'm useing the Pioneer TS-TRX40's I've run my own speaker wires from the HU rear channel out to those speakers.  I would like to add the 3.5's back into the rear channel, and will run new wire to them.

I'd rewire the fronts but I have no idea how the factory sub is wired, and like I said it doesn't do much, but it does help, so I'd hate to loose it.

Now, if I were to add the 3.5's back into the rear channel how would I wire it?  I don't want to wind up with a 2ohm rear set up because of possible damage to the HU, plus if I'm correct and that will double the power to them I risk blowing the 3.5's.  I'm not sure I want to go the other way and wind up with an 8ohm rear and drop the power.

Should I just stop where I'm at?  Pull the 3.5's and hold them for another car/project?

Thanks,

Craig

I have a DEH-46DH with the MOSFET45 chip in it, and am running 2 pairs of front speakers (wired in parallel), and 2 pairs of back speakers (wired in series) and have not had any problems with it.

I am drawing on personal experience as well as various Pioneer documents and manuals I have seen which describe their mosfet amp chips.  Here's a page about the mosfet 50 amp chips but the same principal applies to the '45s.  I would not recommend running subs off the head unit cuz it'll sound like crap, but I do strongly believe that when properly hooked up, more than 4 speakers can be run off this one deck.

That being said, I still have to agree with DYohn.  Basically it sounds like you need to run new, dedicated speaker wire directly from the head unit, and bypass any factory wiring or harnesses.  Run the 2 front speakers off of the head unit's front speaker outputs, and the 2 rear speakers off of the head unit's rear speaker outputs.

A 6.5" amplified bazooka tube would probably fit in your car somewhere, and it would do just fine filling in the low frequency stuff sounds.  The reason I suggest this is because it's not all that easy to find 6.5" component subs and enclosures.  Now I'm not saying it's impossible, just that they are not very common at all.  If you can find 6.5s and their enclosure for a good price, and you're sure that plus the amp will fit, then by all means go for that.  I just want to make sure you know of all the available options. 

And of course, whatever type of sub/amp you decide to use, just use the head unit's preouts to send it a signal as DYohn said.

One more thing to note: make sure the front and back speakers have a good tight seal around the surround.  Get some foam and wedge it under there, or if possible remove the the speakers, apply some foam tape to the metal just outisde of the speaker's surround (where it comes in contact with the opening in the vehicle), and then replace the speakers in their correct positions.  This might help to give you a little more bass with a more airtight setup.  This really varies among vehicles and how the speakers are mounted, but it's something you should look in to.  You're gonna have to take the speakers out anyways to connect the new speaker wiring, so you might as well do that at the same time.

Thanks esmith69 for the excellent input!  It's good to know those Pioneer amps can handle a 2 ohm load.  I was simply quoting the factory info.  And yes, I believe the smallest Bazooka powered tube would fit nicely behind the passenger seat in a MR2, but man those things are small inside!

ToyNut, your  factory sub setup sounds like an internally crossed-over system with a power booster for the sub.  I suspect the seven wires are L+, L-, R+, R-, +12V, ground, and remote power on.  Since this system was intended to be used with the factory head unit, which probably produced about 4 wpc, the amp for the sub is probably rated at about 25 watts and is most likely a booster, not a real amp.  So, if you are now sending the 45 watt peak into this booster it is most likely a) trying to produce about 10X it's designed output, and b) distorting and clipping and generally making the woofer cone into garbage.

You say you replaced the factory 4" woofer with a "Radio Shack special," the 4" drivers in the dash  and the 3.5" in the B pillar with drivers from Boston Acoustics, and you keep "blowing" the 3.5"?  And you have a set of surface mount Pioneer speakers in there now that you like?

Here's my humble suggestions:

• Don't get hung up in the "ohms make more power" thinking.
• Stop using the factory wiring for the speakers.
• Make sure the 4" Boston speakers are rated at least 50 watts each and run new (good quality) wire from the front output of the HU directly to them.  Use your caps to cross them over at 100 Hz or so as they won't produce usable sound much lower than that anyway.
• Make sure the 3.5" Boston speakers are rated at least 50 watts (75 more like it) and go ahead and parallel them with the surface mounts you like.  Use your caps and cross the 3.5" over at 300 Hz or higher and make sure the surface mounts are running full range.
• REMOVE the factory 4" sub system and don't try to use it.  Sell it for $5 on eBay to someone else with an MR2.
• Install a new sub with a signal from the RCA pre-outs.  The suggestion above to get a small Bazooka is a fantastic one and should give you pretty good SQ.  Or you can use the space under your seat where the old sub was to locate a new amp for a new passive subwoofer.

If you want more "boom" have a custom enclosure made and you can put a good quality 10" and whatever amp you want in the front trunk space.  This will cost you a few hundred $ but if it is the type of sound you want, it's the only reasonable way in that car.

Good luck!

Thanks Guys!

I do have all 4 of the Boston's sealed with Dynomat, and that did help a bunch.

I'm not hung up on the "ohms make more power" thinking. I just want to be certain that I'm not going to damage the Boston 3.5's that I already seem to have the ability to destroy!  And in the same train, I don't want to damage the HU that I can't afford to replace.

The bottom line here is $$ or a severe lack of it!

With the factory sub box, (which DYohn, I think you hit it right on the head!) and the "truck" boxes (Hey that's what Pioneer calls them!) I have bottom that I'm happy with.  I would much perfer to run a sub run off the HU's pre-amp output.  I have a Boss AVA-400TR and a 8" Kicker comp lying around that I think would do nicely in this small cabin.  But I just can't figure out how to make a box that will fit.  Boxes that fit won't hold the speaker.  Boxes that fit the speaker won't fit the car.  So since I'm happy with the bottom from the factory sub and the truck boxes I think I'll return the Kicker and use the money for a K&N air filter.  (ok, so I had the amp lying around, and if the wife finds the new Kicker, I'm a dead man!)

Now, having said that I'm at a point where I'm ok with the bottom.  The front 4's just aren't producing enough mid and highs.  Thus, I'd like to bring the rear 3.5's back online.  But I don't want to destroy them or the HU.  I'm not sure what the Boston 3.5's are rated, I think 60watts.

DYohn, from your suggestion of running the 3.5's in parallel with the truck boxes (and the 300hz caps WILL stay on them)  I take it that you think the 3.5's will be ok?  How does Parallel work?  The HU will see a 2ohm circuit?  And will each of the four speakers on the rear channel see 45w max?  (actuall there would be 6 speakers on the rear channel as each truck box has a tweeter and a ported sub)  Should I increase the caps on the 3.5's to 600hz?  More?  Just to be certain?

esmith, Thanks!  I feel much better now for you saying that a 2ohm load won't damage this deck.

Ok, now on to the really dumb question time.  Which wiring is parrallel and which is series?  Is HU + to speaker A +, then speaker A - to speaker B +, and HU - to speaker B - Parrallel?     Now that ya'll have convinced me that this is doable, please don't let me screw it up by bad wiring!!

OH, about the front factory sub.  I know that it isn't much and probably isn't worth keeping, but I think I probably will.  I will probably do an experiment one day and run better (dedicated) wires to the front speakers, dropping the factory sub out of the circuit.  But unless it is a tremendous SQ gain I'll probably go back to using it.  Do you think its existance in the front channel is somehow reducing the SQ of the front Boston's?

Again, Thanks alot guys!

Craig

there may be factory crossovers in the factory wiring that are preventing the speakers from getting some of the lower midrange sounds, and instead are sending all of those as well as bass and sub bass, to the subwoofer.  That is a possibility but if I had to guess I'd say that's not the case as usually the crossover will be be built into the factory amp or directly on the speaker itself, not as part of the factory wiring.

The head unit is going to see a 2-ohm stereo load, not a 2-ohm mono load, so when you see 2-ohm you might think oh no way the head unit can't handle that! because most external 2-channel amps can't handle 2-ohm mono loads.  They CAN, however, handle 2-ohm stereo loads and that's really why you can do that with the pioneer head unit.

In order to hook up the rear speakers, you'll be wiring up each pair of speakers (one pair for the left and one pair for the right) in parallel, giving the head unit a single 2-ohm load per channel.  Basically the way to do this is just to hook each pair up as if they're both using the same positive and negative terminals.  So you'll have two wires going to each positive and negative connection, even though usually you would just hook up a single wire to each terminal.  Then you take a positive and a negative and run to one of the speakers, and the remaining positive and negative to go to the other speaker. 

Check out this page--it's designed for subwoofer wiring but you can apply the same principals to wiring up your speakers.  Use the top diagram, and consider the diagram to be what you'll use for each of the head unit's 2 rear channels (left and right).

Here's a good page to check out if you're interested in learning more about series and parallel wiring.