Can someone answer this for me?? Who else has replaced their stock headrest speakers with aftermarket 4ohm speakers?? Looking at this diagram, the headrest speakers appear to be wired in parallel. Isn't this going to create a 2ohm load if you use 4ohm aftermarket speakers (stock were 10ohm I believe) and blow the amp in your factory deck? Has anyone run into any problems doing this?

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3.4L S/C 87 GT www.fierosound.com
2002/2003/2004 World of Wheels Winner &
Multiple IASCA Stereo Award Winner

Mine have worked perfectly since summer, with the OEM head unit, a UP3 head unit, and an aftermarket Alpine head unit. Using Eclipse SE8233 3.5" speakers

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1984 Fiero SE

From an engineering standpoint, I wouldnt gang them in parallel. For starters, it will shorten the life of the amplifier, it will never have the correct volume, and the weird impedance will make it sound worse than a stock setup.

quote Originally posted by AP2k: From an engineering standpoint, I wouldnt gang them in parallel. For starters, it will shorten the life of the amplifier, it will never have the correct volume, and the weird impedance will make it sound worse than a stock setup.

That's what I was thinking. Even most mid-range add-on amps want to see no less that a 4ohm load, never mind an OEM deck. The Delco unit runs 10ohm speakers from the factory. The Fiero wiring would give 10ohm loads on the front channels and 5ohm loads on the rears because of their parallel wiring. I'd think that ideally, you need either a pair of 8 to 10ohm speakers as replacements or a pair of 2ohm speakers wired in series to work properly without overloading the Delco deck's amp.

I've only seen Infinity 3.5" 2-ohm speakers, and there's also 8-10ohm replacements here http://www.turnswitch.com/speakers.htm

Just rewire them to be in series. that will give you 8 ohm rear, 10 front, should be a better balance, and less strain on the amp.
should not effect your sound, but if they are 2 way wiht built in crossovers, it may soften the bass a tad. this should create less distortion than overloading your amp will. most of those units use a common SDA type amp chip, and they will drive down to 2 ohms, but the distortion numbers go way up.

the rewire is fairly simple, you can see the change I made in your diagram circled in the lower part. I added the polarity to be clear. You may not need this, but someone else might:

[This message has been edited by tjm4fun (edited 01-26-2007).]

quote Originally posted by fierosound: That's what I was thinking. Even most mid-range add-on amps want to see no less that a 4ohm load, never mind an OEM deck. The Delco unit runs 10ohm speakers from the factory. The Fiero wiring would give 10ohm loads on the front channels and 5ohm loads on the rears because of their parallel wiring. I'd think that ideally, you need either a pair of 8 to 10ohm speakers as replacements or a pair of 2ohm speakers wired in series to work properly without overloading the Delco deck's amp. I've only seen Infinity 3.5" 2-ohm speakers, and there's also 8-10ohm replacements here http://www.turnswitch.com/speakers.htm

Actually they arent in parallel. The wiring harness behind my seat has 4 wires.

Thanks to whatever ******* replaced my damned seats with non-headphone seats I know this.

I've taken apart a stock radio and it appears that there are two dual output transistors. the radio I had...the front speakers worked but the rear did not. check of speakers was a-ok. I would think at moderate volumes the stock radio would hold up fine to a 4 ohm load. back in my younger days before I knew better we used to put all kinds of speakers on stock radios...beat the snot out of them and never had any problems. Right now I have a stock pontiac cd/radio with 4 ohm spkrs in the headrest...sounds good....no problems yet.

quote Originally posted by AP2k: Actually they arent in parallel. The wiring harness behind my seat has 4 wires.

They are wired parallel in the harness BEFORE it gets to the seat connector, not in the seat itself.

[This message has been edited by fierosound (edited 01-27-2007).]

^^^

Wiring 2ohms I dont think will hurt anything, on smaller speakers. If this was subwoofers that spiked with high amounts of current then I would be worried.

quote Originally posted by Fosgatecavy98: Wiring 2ohms I dont think will hurt anything, on smaller speakers. If this was subwoofers that spiked with high amounts of current then I would be worried.

You must be right, because nobody has mentioned they cooked a Delco deck's rear channels yet, or at least didn't realize what happened if they did. I'd still expect people to notice the amplifier distortion at higher volume levels, but even that may sound clear compared to the blown old speakers they replaced.

[This message has been edited by fierosound (edited 01-29-2007).]

I haven't cooked a deck, or an amp wiring seat speakers to a 2-ohm load, but on a Pioneer deck in my brother-in-law's GT, it kept tripping the deck into "cut-out" or amp protection mode. Past a certain volume level, the deck would trip into protection mode, and not give any sound for a second. Sounded like it was clipping badly, even at lower volumes when it was tripped. Once we changed it to an 8-ohm load, and had them in series, the problem went away. We've considered changing the capacitors for the seat speakers' tweeters, but there isn't really enough volume out of them to make it worthwhile.

Hope this helps...

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Nic



Beware the toes you step on today, for they may be attached to the ass you must kiss tomorrow.

Proud member of MIDWEST FIEROS!

quote Originally posted by musicman_L7: ...but on a Pioneer deck in my brother-in-law's GT, it kept tripping the deck into "cut-out" or amp protection mode. Past a certain volume level, the deck would trip into protection mode, and not give any sound for a second. Sounded like it was clipping badly, even at lower volumes when it was tripped. Once we changed it to an 8-ohm load, and had them in series, the problem went away.

Thank you for replying - I thought this would have to be the case and I'm surprised nobody else has reported this problem. I'm wondering if perhaps the Delco units DO NOT have this "smart" protection mode. It would just keeping playing and you'd never be the wiser to it - until it stopped due to burn-out. This is a new Delco Monsoon unit (cost a pretty penny too) and I sure don't want to kill it any time soon.

Anyone else??

I would insert a stereo L-pad before each set so you could trim the volume of the headrest from the rear channels. The amp would only see the impeadance of the L-pad+speaker in parallel with the rears in typical applications.

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yellow 88 GT, not stock
white 88 notchie, 4 banger

you don;t need to change the caps on the tweeter crossovers. they are only there to isolate the tweeters from bass, and should not effect anything in a series setup.

most of the stock radios of that era don;t have any advanced protection, they just go til they smoke.
I don;t know how you listen to your radio, but if you like to crank it a bit, you might hear distortion in parallel 2 ohm mode,
but if you just use it for some background distraction at medium/low volumes you may not hear it.

the L pad might also be a way to go, sets a safe resistance to the head, and allows you to set a better balance.

quote Originally posted by tjm4fun: you don't need to change the caps on the tweeter crossovers. they are only there to isolate the tweeters from bass, and should not effect anything in a series setup. most of the stock radios of that era don;t have any advanced protection, they just go til they smoke. .

I'll need a different "bass blocker" inline if I change the line impedance because it affects the crossover point. In the main line I'll be using a 99mfd cap on an 8 ohm line.

I'd imagine the tweeters are crossed-over at 3500Hz (have to dismantle seat to check) and would have a 11mfd capacitor. The value should be half that with 8 ohms, otherwise the crossover point will be moved down to about 2000Hz. That could damage the tweeter, unless of course it doesn't matter because they are in parallel to the woofers in series. This gets complicated fast.

Values for 50 Volt non-polarized Bass Capacitors for 2/4/8 ohm speakers.



Extensive crossover charts here: http://www.the12volt.com/caraudio/cross.asp

I've searched the 'Net and it looks like most people haven't thought about any of these issues and have just "got lucky" and not destroyed equipment, but I see lots of them are complaining "just installed new speakers - why does it sound like crap?"

Then they rip everything out and install aftermarket decks with new amps and speakers where everything is geared for 4 ohms. I think a Delco deck should sound great with excellent speakers and proper impedance loads.

[This message has been edited by fierosound (edited 02-03-2007).]

The Delco OEM stereos are built as inexpensively as possible - right down to the minimum number of screws holding the case together.

One of the places they save some change on the design is to use 10 ohm speakers. These speakers draw less current and allow the use of smaller (cheaper) output transistors and smaller (much cheaper) heat sinks.

Anyway, the output "protection" circuit you're looking for is the speaker itself. Using lower impedance speakers will result in distortion and cause the output stage of the stereo to run hotter. It'll take a little abuse, but if you push your luck it'll die a horrible death.

8 ohm speaker load is OK - you'll notice a little distortion at high volumes but the stereo won't fry. 2 ohm speaker load is NO GOOD. The stereo will die in very short order if you try to drive 2 ohms...

4 ohm loads are iffy - it'll distort at higher volumes, but if you don't run it at sustained high levels it'll probably survive.

If you're installing aftermarket speakers, look for 8 ohm units and don't connect them in parallel - or replace the Fiero stereo with an aftermarket unit that's designed to drive 4 ohm loads.

I dont know, but my stereo sounds great with 4 ohm speakers. As far as the Delco radios being built cheaply, they're not built any cheaper than anything else out there. I've repaired all kinds of electronic audio devices and the stuff that comes out of the orient is as cheap as it gets. The original radio that was in my car had the rear channel toasted....it still had all the original speakers in it. The problem was that some one decided to wire in some other speakers at some point and instead of actualy soldering and using shrink tubing they just twisted the wires together and used tape......thats the worst this to do. you HAVE to have good wiring habits and good grounds. Poor wiring connections will sound like distortion, bad amp or blown speakers.

quote Originally posted by PhatMax: I dont know, but my stereo sounds great with 4 ohm speakers. As far as the Delco radios being built cheaply, they're not built any cheaper than anything else out there. .

4 ohms seems to be a safe impedance even for Delco units, but what about 2 ohms? I think that's pushing it.

I drew up this diagram when I was installing headrest speakers in my '87 convertible. I was using an aftermarket stereo at the time. I never had a problem running them this way and the extra little base was pretty nice. I am not an expert with stereo equipment, but it worked.... FWIW

Here is my writeup

http://www.mrmikes.com/fierospeakers.htm

J.

quote Originally posted by fierosound: Can someone answer this for me?? Who else has replaced their stock headrest speakers with aftermarket 4ohm speakers?? Looking at this diagram, the headrest speakers appear to be wired in parallel. Isn't this going to create a 2ohm load if you use 4ohm aftermarket speakers (stock were 10ohm I believe) and blow the amp in your factory deck? Has anyone run into any problems doing this?

ok, now you are getting confusing in what you are asking. are you talking just bass blockers or the tweeter caps?
the tweeter caps stay the same. the tweeter is still 8 ohms, or whatever it is. adding a cap inline to the whole assembly changes alot of things.
first off, the total resistance of the system will raise up at frequency. ohm meter readings will not show this. depending on the frequency of the signal, the capacitor and the speaker resistance, the effective impedence at most frequency will be higher.
the lowest impedance usually will be at 2 points, the point where the tweeters lowest pass is effective, and again at the point where the main driver is kicking in at it;s lowest point. Hope you are following along here. speaker crossovers are a royal PITA to figure correctly for high end stuff and not have either dead spots or hot spots. using bass blocker caps is effectively making this a midringe and tweeter assembly. proper wiring would be having the + connect to both capacitors, then the capacitor to it;s respective speaker, not having the 2 caps in series, as they would be just putting it in line with a dual element speaker.
it also makes calculating the values easier, the chart would be for the 8 ohm speaker for the main driver, and whatever the existing cap is for the tweeter.
but that doesn;t work for a series arrangement.
in reality, if both of the drivers in each set is 8 ohm, and you use a bass blocker and if you split the crossovers as in this diagram, you will likely end up with very close to a 4 ohm load.

The crossovers would definitely be easier to figure out. But it looks to me that you now have all 4 8ohm speakers wired in parallel. You would still have a 2ohm load in the end.
http://www.bcae1.com/spkrmlti.htm
http://www.the12volt.com/caraudio/boxcalcs.asp#par

A combination series/parallel will make an 8ohm load again, but what a wiring headache with 2-way speakers.

[This message has been edited by fierosound (edited 02-01-2007).]

I'm not positive because I have not seen schematics for a stock Delco radio but when I opened my my stock radio there were two dual output transistors. I'm thinking one handles the front and one the rear. the reason I think this is that on my radio the front speakers worked...the rears did not and this was confirmed on the bench and the seat speakers were tested seperatly. Can anyone confirm the output transistors or get me a schematic to look at.

yes, all 4 are in parallel, but they are now all seperately crossed over. that should effectively raise the impedance at frequency.

since it is a simple crossover, it;s just a SWAG, but I expect at 200-3000 hz you would be seeing about 6 ohms, and at 3000+ you would be seeing 3-4 ohms, but there could be some spike in there that would drop it to 2 where the crossovers are both active, which is definately possible as there are no coils in the circuit to make a definative cutoff line. if you were to add a choke in series with the midrange, you would definately be above 4 ohms all the time.

now if you want to use your diagram, you will need to change the tweeter cap to adjust for the now 16 ohm speaker, ditto the bass blocker. that would require some additional wiring in the seats, 4 new wires to the speakers in each. Since I don;t know how they run the wires, this could be a big issue.

it is definately going to give you higher (min 8 ohm) impedance, and will likely be higher. that can also cause distortion if the amp was designed for a 4-8 ohm load range, but I doubt it would be an issue.

the actual easiest way is to use an l-pad, adds some level control. next would be to add a 2 ohm 10w resistor in series with the speakers in a parallel arrangement, this guarantees a min resistance of 4 ohms, but will get waqrm and lower volume. If you went that route, do not use a wirewound resistor,as that will act like a choke and hurt high end frequency, use a composite type.

I found a really nice simple writeup on crossovers in an old speaker case deisgn boot, I'm attaching the pics of the pages here, you may get some ideas here....
click em for full size....

[This message has been edited by tjm4fun (edited 02-01-2007).]

Thanks, but that is just more work than it's worth...

I think I'll just get a set of aftermarket Miata headrest speakers. They are 2-way, the correct power rating for a stock deck and 7-8 ohm.
Then the Fiero wiring can stay the same with no changes other than an inline bass cap and it won't overload the amplifier.
Details here and I see them selling on eBay http://www.clearwateraudio....ter_Audio/CWC3D.html


Anyone want 2-sets of Eclipse 3.5" 2-way coax speakers????
http://www.eclipse-web.com/integrated/se8235.html

[This message has been edited by fierosound (edited 10-02-2008).]

If any one wants I have a crossover calaulator that is in Excel. you just put in your impedance, crossover point and it gives you all the values for 6 different types of crossovers. Send me your email and I'll forward it to you.

pm sent. always nice to have a stnadalone calculator.

I've ordered a set of the above mentioned Clearwater Audio Miata headrest speakers in the last couple of days. (had to get quote for shipping) I'll post my impressions of them once I have them installed.

[This message has been edited by fierosound (edited 02-25-2007).]

^^^

A Bump !! That is something am going to work on in a later date to change mine Want to know also to how this is going whit you ?

[This message has been edited by Newbfiero (edited 02-18-2007).]

I just received the Cleawater Audio headrest speakers yesterday. They look really good! They created a new part number CWC-3F (F for Fiero) and added the correct connectors so it's just a plug and play installation (once you get the seat apart). For anyone who's never had their seats apart, here's how to do it. http://www.mrmikes.com/fierospeakers.htm

I hope to install them over the weekend and get back to you.

They are already available on eBay at an introductory price of $99.
http://cgi.ebay.com/Clearwa...QQrdZ1QQcmdZViewItem

T.

I've installed the Clearwater Audio speakers this weekend, and here's what you can expect.

What you get in the box - 4 high quality speakers, well packed.


The speakers already have a pigtail with the correct connector to plug into the existing harness in the seat.


The connector makes installing the speaker a simple "plug 'n play". I checked, and the polarity is correct.


Here's how the Clearwater Audio speakers compare to the stock Delco headrest speakers.


Here they are pressed into the foam of the headrests. It works, but GM could have found a better way to install these.


Bottom line, I'm very happy with the results and would recommend these. They fit easily because they are the same 3.5" diameter as the stock ones, and they a nominal 7-8 ohm speakers, and won't produce a too low impedance that could damage your deck's amplifier.

More on system here https://www.fiero.nl/forum/Forum2/HTML/081643.html


Q Sound http://www.qsound.com/2002/technology/main7.asp
Psychoacoustics http://en.wikipedia.org/wiki/Psychoacoustics

See related threads here:
My subwoofer system https://www.fiero.nl/forum/Forum2/HTML/076432.html
My front speakers https://www.fiero.nl/forum/Forum2/HTML/080031.html

[This message has been edited by fierosound (edited 10-02-2008).]

fierosound: I've been following this thread because I also would like some better speakers. I like the idea of miata speakers having close to the right impedance. But what about the front speakers? Are you using the stock units or something else and what are their impedance?

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85 GT 3.4
14.9 @ 90 1.9 60' Old TH125/3.06
Unknown New 4T60/3.42

quote Originally posted by Lilchief: fierosound: I've been following this thread because I also would like some better speakers. I like the idea of miata speakers having close to the right impedance. But what about the front speakers? Are you using the stock units or something else and what are their impedance?

See links posted above please.

[This message has been edited by fierosound (edited 02-25-2007).]

oops! wrong spot.

[This message has been edited by FieroWannaBe (edited 05-19-2007).]

I can't find the Clearwater speakers for Fiero. They are not listed on the Clearwater website.

For the record, mine are still working fine, now wired into a five channel Alpine V12 amplifier that is rated for 2-ohm loads.