I've got a 1991 Infiniti M30 with a factory Bose system. At least 3 of the 4 speakers have blown amps and put out only very low volume sound. Rather than spend about $400 to get the speakers rebuilt, I'd like to simply remove the blown amplifiers and then drive the existing speakers with a couple of 2-channel amplifiers, one for the front and one for the rear. I'm told it will work if I match the amplifier output impedance to that of the speakers. Does anybody know the impedance of the factory Bose speakers?

Any other suggestions?

There's some different numbers out there, but it's commonly agreed that the factory (Bose) speakers are about 1 or 2 ohm. If you're planning on undertaking this task. I'd suggest you replace the whole thing. You're about "dead on" regarding the cost of having the factory units replaced/rebuilt, and you could proabbly buy a powered HU and at least 2 door speakers for much less, and add MP3 playback at the same time.

Is your M30 a coupe or 'vert? I'm thinking about trying to find one next year as a project, here's my goal .

Like Rex said, the Bose speakers are either 1 or 2 Ohms.

I don't really see the point of getting an aftermarket amp and keeping the OEM Bose speakers. If you get an aftermarket amp, get aftermarket speakers to go with it.

I think that a 4 channel amp would be good.

Ask and we'll help you find some replacement equipment

bose speakers are 1/2 ohm THEY CANNOT BE SAFELY USED WITH AFTERMARKET AMPS!!!!!

PoorManQ45 wrote:Like Rex said, the Bose speakers are either 1 or 2 Ohms.

I don't really see the point of getting an aftermarket amp and keeping the OEM Bose speakers. If you get an aftermarket amp, get aftermarket speakers to go with it.

I think that a 4 channel amp would be good.

Ask and we'll help you find some replacement equipment

Okay.....you talked me into not using the existing speakers with other amps. This is my wife's car, and she's not that fussy about having the highest quality audio. I don't want to spend a lot of money on this, or I might as well just have the Bose parts replaced. I've bought a couple of ESA 2-Channel Amplifier (EA250) amps, one for the front and one for the rear. http://www.circuitcity.com/rps...ew.do Can you recommend some reasonably priced speakers to go along with these amps and give me any tips for installation?

Very nice buy! 55W RMS by 2 channels for $50 !

What type of speakers are you looking for? Components or Coaxials? What is your price range/Limit?

*edit* What are the speakers sizes for you vehicle(M30?)?

PoorManQ45 wrote:Very nice buy! 55W RMS by 2 channels for $50 !

Actually, I paid $29 each for them on a Circuit City closeout sale.

PoorManQ45 wrote:What type of speakers are you looking for? Components or Coaxials? What is your price range/Limit?

*edit* What are the speakers sizes for you vehicle(M30?)? [/QUOTE]

The rears are 6 by 9, and I believe the fronts are 4 round. Not fussy about speakers, would like to stay in the $15-$20 each range.

Is it mandatory that I also have to install one of these for each amp? Or can I simply adjust the gain on the new amp?

http://www.pac-audio.com/oem1kits/aoemresults.cfm?

91M30 wrote:The rears are 6 by 9, and I believe the fronts are 4 round. Not fussy about speakers, would like to stay in the $15-$20 each range.

Hmmm. That is exactly the price range that my 6x9s that I put into the Q45 are in. Go to Car section in your local Walmart. Look for a pair of 6x9 Roadmaster speakers. The box is mostly red, and the cones of the speaker are red too. They should cost about $20 for the pair.

I don't know if Roadmaster makes a 4in round speaker . They do make a 5.25in round speaker though. Is the M30 like the Q45, where the door speakers are mounted in pod like things?

If the M30 has Bose, it is going to be mounted in a plastic enclosure.

Update: Looks like I can use the existing rear Bose speakers in conjunction with the new ESA 250 2-channel amps noted earlier in this thread.

Just to try it out, I removed the Bose Amp from one of the bad rear Bose speaker assemblies and temporarily wired one channel of the new ESA 250 amplifier directly to that Bose speaker, using the existing four wires to power the amp and provide input to the speaker level input of the amplifier. Sounds good, and even better when I turn the bass boost switch on for another 12db. The speaker puts out plenty of of volume even with the amplifier gain adjusted to the minimum setting. I tested it at various volume levels for 30 minutes or so before I unwired the temporary setup.

I jumpered the remote power on terminal on the amplifier to the existing positive power lead, so the amp is turned on with the existing Bose relay under the hood. Wiring changes will be minimal, and I won't cut into any harnesses....I'll just connect to the existing four wire connectors in the trunk area.

Anyway, I'll mount the amp under the rear deck and permanently wire it in tomorrow. If it still looks okay, I'll try to do a similar thing with the front speakers. If it all works out, my total cost for fixing all four speakers/amps will be about $70 for the two 2-channel amps and connector splices.

Bose speakers are severely low impedance. Those amps do not have internal low impedance protection to know when too low is too low. You have been warned.

Simmsled wrote:Bose speakers are severely low impedance. Those amps do not have internal low impedance protection to know when too low is too low. You have been warned.

Yeah, I was worried about that too, but the manual for the amplifier says "Easily Drives 2-ohm Loads", and also has the following section about low impedance and other protection circuits:

Protection Circuits- The amplifier has extensive protection circuits to protect your amplifier and speakers. these protection circuits can help minimize damage to the amp or speakers if something goes wrong during installation or during normal operation.

Low Impedance Protection - The amplifier monitors the output section from low impedance loads. If an abnormally low impedance is sensed at the output, the amplifier will shut down automatically.

Thermal Protection- The amplifier will shut down if its temperature exceeds a safe operating level. The amplifier will remain off until it cools to a safe operating temperature.

Short Circuit Protection - The amplifier will shut down if a short circuit condition exists.

Update: Today I installed a new ESA 250 2-channel amplifier in conjunction with the existing rear Bose speakers in the rear of my wife's 1991 Infiniti. I removed the existing bad Bose Amps from both of the rear Bose speaker assemblies and then wired the existing Bose speakers directly to the output channels of the new ESA 250 amplifier (normally $69, closeout price $29). I mounted the amp in the trunk under the rear deck between the speakers. (Note that after I removed the blown amps from the speakers, I put the plastic shrouds back on the speaker assemblies to provide protection for the speakers from stuff getting loaded in the trunk.)

I cut the harnesses off the bad amp connectors, and used the two four wire plugs to connect the existing left and right speaker inputs and power wires to the speaker level inputs and power input (combined LH and RH power wires) of the ESA 250 amplifier. I jumpered the remote connection at the amplifier, so the amp turns on whenever the existing Bose relay under the hood is actuated.

Especially now with both channels hooked up, it sounds really good, and even better when I turn the bass boost switch on for another 12db. The speakers put out plenty of of volume even with the amplifier gain adjusted to the minimum setting.

If everything still looks okay after a week or two, I'll try to do a similar fix using the existing Bose front speakers. (I have to find a place to mount the front amp....hopefully it'll fit behind the radio.) After I replace the fronts, my total cost including tax for replacing all four speaker amps will be less than $70.

The reason the volume seems so loiud, even at the lowest gain settings it the amp is being "over driven" by the low ohm loads of the speakers. I would go see if they have any more of those amps for when on of them fries. Another idea is to run 2 channel stereo off 1 amp with both right and both left speakers wired in series to (numercially) increase the ohm load and thus decrease the load on the amp.

Just a suggestion, as "we" think running the amp to the low (numerical) ohm load will sounds great, but shorten the amps liife.

EDITED: Simple brain fart series/parallel/series odd/even/odd/even, I'm an idiot.
Modified by Rex at 11:27 AM 12/28/2004

Rex wrote:Another idea is to run 2 channel stereo off 1 amp with both right and both left speakers wired in parallel to (numercially) increase the ohm load and thus decrease the load on the amp.

I think that you meant to say wire the speakers in series

Rex wrote:The reason the volume seems so loiud, even at the lowest gain settings it the amp is being "over driven" by the low ohm loads of the speakers.

Hmmm....I didn't mean to imply that the volume was excessively loud......just that without adjusting anything (the gain was factory set at lowest setting), the volume control on the radio seemed about normal.

With the built in protection circuits as described earlier in this thread, doesn't it seem that the amp should never operate beyond it's rated range; i.e., it's not being overdriven?

What does it consider to be "abnormally low"?

Usually that kind of protection is designed to prevent grounded speaker wires (= 0 ohms), if it suts itself down for low (>2 ohm) loads, I would think it wouldn't run at all, as it's seeing a load lower than that, or bloody close to it.

By all means run the set up as you see fit, we just want to make sure you're aware. The best anyone can do is make an informed decision.

Bose's nominal speaker impedance is .49 ohms. I just put 4 of them on the meter. Your amplifier says that it has low impedance protection, but it does not. Those amps can be advertised with all of those protection devices to make you feel warm and fuzzy.

The only way that the impedance can be monitored in an electrcal circuit is with a microprocessor. That amp does not have a microprocessor to monitor impedance. What it DOES have is a circuit breaker that will turn the amp off if it gets too hot (simple switch and temp sending unit) and it has an on/off switch inside that will sense a shorted circuit. This means that ZERO resistance is observed.

THAT BEING SAID...

A lower impedance figure doesn't make life easier for an amplifier - on the contrary it means the speaker sucks more amplifier power for a given output. Not a problem provided your amp measures up to the ideal, doubling its power as impedance halves, but many a 50W amp delivers not 100W, but 70 or 80W, into a 2ohm load. And there aren't too many 100W amps (even taking into account the fanciful way many manufacturers arrive at such a figure) capable of producing 200W into 2ohms, let alone even surviving 400W into 1ohm. High current amplifiers are the exception (such as the $$$ Orion HCCA amplifiers)

Indeed, some amps have a power rating that's quoted into a 2ohm load, to make them seem more impressive. If this is the case, remember your 50W/4ohm amp may only be 25W in terms of standard amplifier measurement.So low-impedance speakers will make many an amplifier struggle, and it doesn't help if you start off with lowish 2ohm power output on the amp.

The problem is that the power supplies can't top up the power as fast as the speakers are draining it. THE POWER SUPPLY FOR THE ESA AMPLIFIER IS NOT STRONG ENOUGH TO KEEP UP WITH THE CURRENT REQUIREMENT OF EXTREMELY LOW IMPEDANCE SPEAKERS. That is why it all works. But you will run the amplifier's max current at that specific voltage thru it every time you turn it on and play something. This will shorten the life of the amp greatly and it will die.

Some amplifiers that DO have microprocessor controled impedance measurement are Precision Power's Art series and PowerClass series. They call it AM IV and AM V. The reason that they have this microprocessor is because their power supply is capable of producing enough current to fry itself and burn up into a massive car fire.

But like I said before... you have been warned. But I wish you the best of luck!

Simmsled wrote:Bose's nominal speaker impedance is .49 ohms. I just put 4 of them on the meter. Your amplifier says that it has low impedance protection, but it does not. Those amps can be advertised with all of those protection devices to make you feel warm and fuzzy.

The problem is that the power supplies can't top up the power as fast as the speakers are draining it. THE POWER SUPPLY FOR THE ESA AMPLIFIER IS NOT STRONG ENOUGH TO KEEP UP WITH THE CURRENT REQUIREMENT OF EXTREMELY LOW IMPEDANCE SPEAKERS. That is why it all works. But you will run the amplifier's max current at that specific voltage thru it every time you turn it on and play something. This will shorten the life of the amp greatly and it will die.

But like I said before... you have been warned. But I wish you the best of luck!

Thanks. I really appreciate the responses, and understand that life of the amp will probably be reduced. But if it does die, I'm only out $29 plus a few hours installation time. In the meantime it sounds as good as it did before the original Bose amplifiers went south. I've run it at pretty high volume for an hour, and the case of the unit is only slightly warm to the touch. Here's some pix of the installation: http://www.villagephotos.com/m...58761

Not all Bose systems are <1ohm. My '02 has 4ohm tweeters and something like 2.95 ohm mids.

Check the speakers with a multimeter and design the system accordingly.

audtatious wrote:Not all Bose systems are <1ohm. My '02 has 4ohm tweeters and something like 2.95 ohm mids.

Check the speakers with a multimeter and design the system accordingly.

Interesting. My wife's car is a 91, and if the rear speakers in this Bose system are actually above 2 ohms, that may be why after several days the system still sounds good.

Dumb question, but how do I measure speaker impedance with a mulitmeter? I thought it had to be an AC test of some sort to measure speaker impedance. ????

Or is there some way I could find out from the part number on the speakers?

There should be a setting for Ohms, the Omega icon??

Just tap the multimeter leads to the speaker terminals and it should disply the resistyance.

Rex wrote:There should be a setting for Ohms, the Omega icon??

Just tap the multimeter leads to the speaker terminals and it should disply the resistyance.

I just found the following on another website:

The actual speaker impedance varies with frequency and is difficult to measure outside a lab. For convenience, we deal with the nominal impedance. The nominal impedance will approximate the DC resistance of the voice coil in the speaker.

You can attempt to measure speaker impedance with an ohm meter. The ohm meter will read slightly low; e.g., : 3 to 3.5 ohms.....4-ohm speaker 6 to 7.5 ohms.... 8-ohm speaker 13 to 15 ohms.....16-ohm speaker

yey, you can read .

Most misinformed people think that a speaker stays at the rated Ohm throughout the entire frequency range. That is untrue.

Most speakers will drop down to about 1/2 their rated Ohm load, and spike up to about 2~4 times their rated Ohm load.

REX/Simmsled,

Couldn't he just put two 1 ohm shunt resistors in series in the line between the speakers and the amp which would increase the ohm load by 2 resulting in a 2.5 ohm draw (including the .5 ohm speakers) keeping the amp from shutting down for low impedance. This solution would decrease the power to the speakers and I am not sure by how much or if it would be significant enough to affect acceptable listening levels. Thoughts/Corrections?

Yep, he could do that, but I don't see the point. I mean, he has to add resistors, which are going to decrease the power available to the speaker, just to be able to use his amp "safely"

Dude, I'm telling you, just go buy some aftermarket speaker replacements. I can guarantee you that you will thank me after you do so. Nobody should have to suffer through the horror that some like to call BOSE.

For about $40~$75 you can get some nice replacement speakers that actually have seperate drivers. ANd if you wanted to, I could actually find you a decent pair of components for about $80