ron1stknight

iTrader: (1)

In general, how big of a deal is the impedance rating for speakers vs radio? This would be along the line of having speakers rated for a certain ohms and a radio that puts out at a different ohms.

For FD, if I remember correctly, the bose speakers are rated for 4 ohms (center) and 1 ohm (door & wave). What would happen if you ran a replacement unit operating at a totally different range?

Is there an easy way to take a signal and convert it to the correct impedance? Is there also a way to drop the amplified power down so you don't blow the speakers?

FearNoPiston

iTrader: (17)

I'm not totally sure but ohms will not matter as the power fed from the deck is used as a signal to the factory amp, I am pretty sure this is how it works. So you shouldnt have a problem unless you by-passed the amp and went straight to the speakers.

mike_merryguy

iTrader: (8)

ohms do matter, if you run a 4 ohm deck and hook up a speaker out of that range it will eventually blow the speaker or the amp in the radio, or whatever amp you are using.
it will most likely work for a while, but your speakers may pop or crack, it may even cut out requiring you to shut off the head unit and turn it back on

rotary8

here is my answer In the begining there was nothing and god said let there be light and there was light but still there was nothing . But by god you could see it !

rotary8

on a serious note most radios might be able to play 4 or 8 ohm loads but when you start going to 2 ohm the amplifier will not be able to deal with such a low impedance and you will run into problems . can you be more specific .

FearNoPiston

iTrader: (17)

I know ohms matter I was just saying in this case becuase the deck is not going to the say 2 ohm speakers it is sending signal to the stock amp which can obviously handle two ohms....on a side note it is easier on an amp to run 8 ohms than 4 but you will sacrifice power but have a more accurate speaker

John64

Take DMM and test the leads for your front speakers. I very seriously dought that they are 1 ohm loads, most high end amps can't even touch that.

X-JaVeN-X

alot of bose crap does run 1 ohm stuff (I don't know if this is true on the FD). You don't want to run a 1 ohm speaker on a 4ohm rated amp/receiver...it'll fry the receiver or the receiver won't play at all and go into a "protection mode".

My opinion...if you're going to keep the bose crap...keep the factory deck...otherwise (and this would be my choice), ditch all that bose crap and get new speakers and deck and run new wires.

ron1stknight

iTrader: (1)

How about keeping the bose acoustic wave sub? I agree that replacing the speakers is the best bet, but I'd like the keep the sub. Is that just a matter of sending out a pre-amp signal from the new radio?

That would be again where the ohm rating question comes from. According to shop manual, the sub is looking for 1 ohm impedance, max input of 5.5V.

Thanks everybody for all the input!

mike_merryguy

iTrader: (8)

https://www.rx7club.com/interior-exterior-audio-26/bose-wiring-diagram-25090/

there is a wiring diagram on that thread for the bose setup, if that is what you are running I dont think you can keep that speaker with an aftermarket head unit.

mike_merryguy

iTrader: (8)

http://www.crutchfield.com/App/Produ...C4MA02&tp=3486

here you have it, 40 bucks, the Scosche OEM Amplifier Adapter
1993-up Mazda is supposed to allow you to integrate the bose system with an aftermarket radio, says it does line level matching, this is a 4 channel setup so i am assuming it will door both doors, center and the acoustic speaker, then read this
https://www.rx7club.com/interior-exterior-audio-26/bose-schosche-adapter-42023/

in there it tells you how to rewire things so that your amps turn on, apperantly they didn't put the power trigger in the wire

ron1stknight

iTrader: (1)

That is awesome! Thanks!!!

mrgne

iTrader: (6)

The ohm rating on the speakers is actually the impedance of the speaker. It is very important that the speakers impedance is the same as what is required for the deck. If you change that, you will either get muddy underpowered sound or it will be overpowered and distorted. Anyway you cut it its not good. If you really want to, I think you can throw another componant to balance out the circuit. Talk to an electrictian, they would be able to help you.

rotary510

iTrader: (1)

unfortunately, the oem bose system in most cars is not easy to upgrade with aftermarket speakers or amps. like it was mentioned earlier, you can buy an adapter to change the head unit or vice versa the amp and speakers. but i can't remember hearing anything that sounded good using one of those.

from my experience most bose speakers are rated at an odd impedence which is tuned specifically for the amp and equalizer circuit of the system. so to replace a pair of speakers usually requires replacing all speakers and you probably will end up removing or replacing the entire wave setup.

so its pretty much an all or nothing kind of proposition if you want to do it "right".
there's my 2 cents.

dblboinger

iTrader: (3)

FearNoPiston - Aren't you the guy who told me 6 months ago that I didn't know what the **** I was talking about and that you "work in a car stereo shop in Vancouver"? Yet you make a statement like this? WTF!!!

If you bypass the factory amp you won't get **** from your speakers because the signal to the amplifier is a low-level signal which most likely won't even drive a speaker.

For the record...the "radio" does not put out ohms...it outputs watts the amount of which is determined by the ohm rating on the speaker and the amount of current supplied by the "radio". The amount of current available is dependent on the amount of voltage the power supply section can supply.

ron1stknight...to answer your question you need to consider 2 things...the sound level produced and the possibility of damage to equipment. If you replace a 1 ohm speaker with a 4 ohm speaker you increase the load by a factor of 4, which causes a reduction of power by a factor of 4 and a significant decrease in audio output. Here's an example: Say I have an amplifier with a power supply section that produces 40 volts and I am using 1 ohm speakers. Ohms Law states Voltage = Current X Resistance and Power = Current squared x Resistance. According to these formulas that equates to 40A of current and that produces 1600w of power. Take the same amplifier and put a 4 ohm speaker on it...the voltage produced will not change because it is a function of the power supply. However the current will drop to 10A and that produces only 400w of power.

You would think then that if you replace a 4 ohm speaker with a 1 ohm speaker you would have the opposite effect, which is theoretically correct. The problem here is you most likely fry the output stage of your amplifier because the current demand is above what your amplifier is designed for. There are, of course, exceptions to this but to get an amplifier of this quality you will have to spend some $$$.

BTW, you can not measure the impedance of a speaker by simply measuring it with a DMM as suggested above. The reason is, the voice coil in a speaker is a straight piece of wire. To a DC meter (DMM) it will measure very low resistance. A speakers impedance rating is determined by measuring the voltage drop across the speaker terminals at a specific frequency (normally 1000 Hz) which is why a correct impedance rating for a speaker will be listed as 4 ohms @ 1kHz. As the frequency increases the impedance increases and vice-versus.

mrgne

iTrader: (6)

Listen to that guy ^. he knows what he is talking about. the only thing I disagree with is that the amp is not absolutely necissary. Let me justify this, you can bypass the amp and you will get sound, HOWEVER (< notice how big it is.) as it has been said before, the signal sent to the amp is very weak. Weak signal = weak sound, so you will have to turn up the volume to hear it. The reason I know this is I have done this. DOING THIS IS A BAD IDEA A BAD BAD IDEA. but if you want some crappy sound instead of no sound then its a bad idea you could do.

mike_merryguy

iTrader: (8)

I agree with all you said except this, when I put my DMM on the pos and neg speaker terminals of a 4ohm sub I read 3.8 ohms, so how is it that you "can't" measure the speakers ohm value?
a change of .2 ohms is not significant enough to say that you can't measure without power...
don't really feel like getting into detail here, but basically

1.
amp puts out power, requires a certain LOAD on the circuit in order not to over heat and to meet the power output of the amp, power is dissipated by heat, so the wrong load will overheat the circuits in the amp or overheat the load itself, depending on if the load is to high or to low
2.
Speaker creates a LOAD on the circuit, the load is predetermined at design of speaker usually running 2, 4, 6, or 8 ohms (most common that i have seen)
the Load can be changed by running speakers in Parallel or Series circuits
in series resistance is additive so (2) 4ohm speakers = (1) 8 ohm
in parallel resistance is the reciprocated sum of the reciprocals, (google it) (2) 4ohm speakers = (1) 2 ohms speakers
AND NO ITS NOT HALF IT JUST WORKS OUT THAT WAY WITH 2 4ohms!!! for example (3) 4 ohm speakers = (1) ~1ohm speaker
3.
speaker has the same properties as a RESISTOR, it has an OHM value that does not change with amount of power applied, that would be a VARIABLE RESISTOR
usually variable resistors only change resistance by twisting a screw, not by amount of power applied, a small amount of resistance change is usually accepted in circuits and handled according to the circuit needs

and just for reference I am an Aviation Radio Repair Technician, I know just a few things about electronics, surely not everything though... much more to learn, always is...

John64

"BTW, you can not measure the impedance of a speaker by simply measuring it with a DMM as suggested above. The reason is, the voice coil in a speaker is a straight piece of wire. To a DC meter (DMM) it will measure very low resistance. A speakers impedance rating is determined by measuring the voltage drop across the speaker terminals at a specific frequency (normally 1000 Hz) which is why a correct impedance rating for a speaker will be listed as 4 ohms @ 1kHz. As the frequency increases the impedance increases and vice-versus."


You are wrong on this. Check your DMM, pop it on ohm and put + with + And - with - and you will get the impredance. Most speakers are rated at a nominal impedance, thus they are not all the same. You can get a 4 ohm speaker with a 3.8 ohm reading. Just make sure you don't listen to know it alls on here and replace your batteries often as it can give you a false reading.

dblboinger

iTrader: (3)

This is a common misconception. If you apply a DMM you measure the DC resistance of the voice coil only, NOT the impedance of the coil. While they are both expressed in ohms, they are not the same. Resistance is a DC measurement where impedance is an AC measurement. Speaker ratings are impedance because a speaker reacts to an AC signal. Put DC on your speaker leads and you get a good "pop" but that is all. The only way to measure impedance with a DMM is to measure the AC voltage drop across the speaker while it is in use. This is a fact regardless of what you may have been told or think you have seen. There is no argument for this fact. Now, is 3.8 close enough to 4 ohms...probably. But like I said....acurracy.


The reason you may get 3.8 ohms or 3.6 ohms or whatever, is because there are other factors, such as coupling coefficient, voice coil diameter and stack height, that cause the 3.8 ohm reading you see with a DMM. If you take the wire on a speakers voice coil and straighten it out it will measure at or very near 0 ohms with a DC meter. When you wind it around a spool the magnetic field induced in the coil is what causes the DC resistance to increase. Among other things, I use to test speakers for a living for a short period of time. I also use to teach basic electronics, including AC theory. I know it is a miniscule difference, but I believe if I am going to comment on an issue I want to be as specific and accurate as possible. This is the way it is, accept it or don't, it doesn't matter to me or change the facts.

And the amount of heat has noting to do with this discussion. The amount of heat (in watts) is a completely seperate speaker specification that basically tells the current handling capability of the voice coil.

Also,

John64

You contradict yourself again. Above you state that you cannot measure the impedance of a speaker with a DMM, now you say you can but not as accurate. Thats why I said "Nominal Impedance", which is what all manufactures use. Heres some quick little things I just looked up for you.
"If you just want to find out the nominal impedence of the speaker e.g. ist it 4, 8 or 15 ohms then there is a rough & ready way. Just use your multimeter to measure the DC resistance of the voice coil i.e. across the speaker terminals (with nothing else connected) and multiply the answer by 1.3. So if the DC resistance is say 6 ohms then the speaker is nominally 8 ohm impedance."

Yeah, if you want to get all up on it you use a frequency generator and the such, I'm talking nominal impedance nothing more or less.

dblboinger

iTrader: (3)

You misunderstood something cause I never said you could measure the impedance using a DMM. What I said was you could measure the DC resistance of the voice coil, not the characteristic impedance. Two totally differenc things. I still say if you are measuring across the terminals with a DMM you are measuring the resistance of the voice coil, NOT the impedance. If being within 2 ohms is good enough for you then so be it, but regardless it IS NOT accurate. For instance, using your 6 ohm - 8 ohm statement. If the power supply in your amp produces 48 volts and you have an 8 ohm speaker your power is 288 watts. If you have the same amp with a 6 ohm speaker you will have 384 watts, nearly 100 watts more. That, in my opinion, is a significant difference. And there are speakers out there that have a 6 ohm impedance.

Furthermore, if you start designing crossovers based on an inaccurate impedane rating your cross-over points will be off and you may not get the expected results or worse you could damage your speakers. I know most people are not this involved with their system, but some are and maybe the person who started this thread would like to be.

But you are right about one thing...what I should have said is you can't measure impedance with a DMM by doing an ohm check directly across the speaker terminals. You can use a DMM to measure the voltage drop across the speaker terminals and this is the correct and accurate way to measure impedance.

I'm done with this. The info is there, use it as you will.