My Volvo Speaker says 4 ohm, why does everyone say 8 ohm?

[PDLarson]

I took the car to a stereo shop and discussed my situation with them. They didn't seem real interested in the details of how Volvo / Alpine may or may not have wired things. However, as soon as we turned up the volume the guy's first question was if the impedance was right. I'm going to try 8 ohm speakers in front and see what happens, just for an experiment. Hopefully I won't get any magic smoke from my amp. I had been planning on ordering a pair, then it occurred to me, I have a pair, in the back doors! Dang it, I just put my refinished door panels back on the rear doors today, arghhhhhh! I hate taking those panels off because I'm sure I will break off some of those stupid plastic attachment points that I just glued back on.

[VOLVOGUY8306]

My two cents. Consider that the date on the speaker is the alphanumeric, like 99W15 (meaning the 15th week of 1999), on one of the above photos. Maybe that'll help sort things out.

[PDLarson]

Yep, in the post above with the pics of three speakers together I said "So the stamped dates don't mean anything unless the one stamped 12 is 100 years old or brand new. I suspect the code on the right of the label is a date code, they are 98W36 (from the S70) 99W16 and 99W15 from my car. I suspect this is the year and week of the year that they were made."

But thanks, I'm glad that made sense to someone else.

Now if I can just get someone to conenct the rear speakers to the front door connections, adjust the fader to the front only and crank up the bass to see what happens This would be my test to see if the front doors should actually be 8 ohm, not 4 ohm as they are labelled. Sorry I forgot who but someone mentioned that they could be labelled wrong. Seriously, I just had my door panels redone (I'll update my build thread soon) and I DO NOT want to take those stupid panels off again. I left the front pass panel loose (hooked on the top and the one screw by the handle but no plastic tabs) if I needed access to the front speaker but the rears are all buttoned up. If I find a solution I'll deal with the driver's panel but I just cannot bring myself to take them all off again. I just know all those black plastic holders will come unglued from the back of the panel if I pull or even use the correct tool.

[DragosGD]

PDLarson, front speakers (dashboard and front doors) are 4 Ohms. Rear doors and rear shelf are all 8 Ohms. The radio has 6 separate channels (all in 4 Ohms) You can find all the info about the radio in the Wiring Diagrams that MVS collected for us. In my pictur the blue circles are 4 Ohms speakers in 4x4 Ohms channels, the green circles are 8 Ohms speakers connected in parallel in 2x4 Ohms channels. Good luck with your project !

[ojdorson]

Another thing that can cause loss of bass is the phasing of the speakers. Basically, the speakers will produce sound whether the positive and negative wires are hooked up correctly or not. When you have one speaker, it hardly make a difference, but when you have two speakers in a system, if one is wired out-of-phase you will lose low frequency information as they are canceling each other out. On one of the front speakers, hook up the wires in reverse and have a listen.

[DragosGD]

Another thing that can cause loss of bass is the phasing of the speakers. [....]

That's a very good point indeed !!!

[PDLarson]

DragosGD, thanks for the schematic.

I have triple checked polarity / phase but yes, that could have an impact and always good advice to check.

See this thread to see what I ended up doing. In the end, I am satisfied with just replacing the front door speakers.
Speaker Upgrade. What to Get
https://www.matthewsvolvosite.com/forums ... =1&t=48451

[bill d cat]

PN 3533622 labeled 8 Ohm seems to be the correct PN for the rear door speakers for both the S70, which has rear deck speakers, and the V70, which doesn't have a rear deck or speakers.

I can understand using 8 Ohm speakers if both the rear door speakers and rear deck speakers were on the same channel, but why are the V70 rear door speakers 8 Ohm? (It's been quite a few years since I took Physics II, so please forgive me.)

[mrbrian200]

Putting an 8 ohm speaker where a 4 ohm was previously used will not hurt anything. If the new speaker's efficiency rating (SPL/Watt @ 1m distance) is 3db higher than than old 4ohm speaker it will produce the same volume levels while drawing less current from the amplifier, which generates less heat within the amplifier. Which for OE equipment is generally considered a good thing for longevity. If there is a 'known hack' that involves replacing older 4 ohm speakers with newer 8 ohm speakers, this is possibly what it revolves around as it is likely the newer 8ohm speakers are also more efficient.

What you never want to do is place an impedance load to an amplifier that is lower than it was designed for. IE if there are two 8 ohm speakers wired in parallel without a crossover (a 4 ohm load to the amplifier) that was designed to drive a 4 ohm load and you replace one of the 8ohm speakers with a 4 ohm speaker the load to the amplifier will be 2.6 ohms. Which will draw too much current through the amp and possibly damage or destroy it. Keep in mind that the impedance of any speaker actually varies with frequency and that 8 ohm speaker can present loads to the amplifier both above and below 8 ohms depending on frequency which is where replacing speakers with a lower impedance can get particularly dangerous with regard to 'protecting' an amp from overheating/self destructing.
The following is a graph that is typical for any bass/midrange driver:

Capture.JPG (75.19 KiB) Viewed 1383 times

The blue line is the impedance presented to the amplifier over the speaker's frequency range. Though this speaker's 'nominal impedence' is rated at 4 ohms, you will see peak around the speakers resonant frequency (in this case around 15 ohms at 33hz). However at other frequencies the impedance presented to the amplifier can be below 4 ohms (in this case closer to 3 ohms though much of the midbass region).
So, fiddling with speaker impedance, especially when switching to a lower impedance speaker, can be tricky and dangerous if you don't understand fully all the variables at play. Most people casually fiddling with this stuff really don't have a firm handle on much of it.

So be careful. And don't assume that replacing that (likely newer) 8 ohm speaker with a 4 ohm will accomplish anything. You have to dig deeper to know.

[bill d cat]

Thanks for the quick response!

But in the DIY, viewtopic.php?f=33&t=57976 "S70 speakers demystified", Lee used Blaupunkt GTx 803 SC 8-inch speakers (which according to specs are 4 Ohm) for the rear deck, and used Kenwood KFC-G1620 6 1/2 inch 4 Ohm speakers for the front and rear doors.

6 1/2 inch 8 Ohm speakers seem difficult to find, at least from major manufacturers at reasonable prices.

Volvo put 4 Ohm x 6 1/2 inch speakers in the front doors and 8 Ohm x 6 1/2 speakers in the rear doors of both the S70 and V70, which use the same stereo head unit. The S70 has the 8 inch rear deck speakers that the V70 doesn't.

The small front dash speakers (tweeters) seem be 8 Ohm.

There are a couple of small speakers (tweeters) in the V70 "D" pillars, which are 8 Ohm according to the sticker. Fortunately, they are so far back that they probably don't do much. I'm not planning to replace them (although who knows what I could use since they are NLA from Volvo).

Thanks