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Hi All!

I recently acquired a 2005 987, with the Bose system. PO bought it with an Android/Carplay head unit already installed. No instructions or anything, but it did connect with my phone and it worked so I had no issues. Or so I thought!

When I got home, I realized that the larger speaker on the driver side door does not produce any sound, and also when headlights are turned on, I hear a hissing start from the said speaker (no hissing when headlights are off) I do not think this is some sort of deal breaker, but it is an annoying issue to have and I would like to make it right. Maybe it could be a simple fix such as unplugging the wiring, plugging it back in as the speakers in the door have not been touched so must be something with the wiring behind the unit.

I have some questions here, as I want to A) figure out why sound is not working on just one speaker, B) hopefully replace head unit with one that has a physical rotating volume knob

1) If I purchase ANY double din unit on Amazon, would it simply be plug and play? Or do I need to use that unit's specific wiring harness? Do I need another fascia, or are those universal?
2) PO also installed an upgraded amplifier in the frunk. Could there be a wiring issue there that affected this one speaker? I can take a look at that as well.
3) If I decide "F** IT!" and just install the included, original head unit, would it be easy to go back to original? Do installers typically cut the original wiring or leave it in place?

Thank you all in advance!
 

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For the speaker issue, I'd start by using a DVM to check 1) that you're getting signal to the speaker from the HU and 2) that the speaker isn't blown (check resistance). Ideally, you'd check the ohms between the other door speaker, if you can... they should match or be close. If you can't do that, you can just see what the reading is - typically should be 6 or 8 ohms for most speakers. From there, you can see what your next steps would be. I'm guessing the HU isn't getting signal to the speaker, particularly if you're hearing hissing (which implies the speaker may be fine, but it's best to check anyway.)

For the hissing - do you have HID headlights? They can usually generate electrical noise, which might be what is being picked up? Still seems odd. Maybe someone screwed up the wiring.

DoubleDIN should be a standard, so you may be able to use the existing fascia.

Plug and play? Unlikely... most HUs have a specific connector for themselves, so there is likely an adapter between that and the car's connector. If you get another HU, it will likely come with a different connector, so you'll need to either rewire or replace the adapter. You might get lucky if you stick to the same brand - sometimes the HU connector will match, but you'll need to do some research to make that happen.

Amplifier in the frunk - yes, this is certainly a likely candidate for the speaker/hiss problem. I would certainly check the wiring there. Again, with HIDs if they shared wiring with that circuit or something, that could be the source of the hiss.

Returning to stock is an option. It could be easy, if they didn't cut wires... but you never know. You can't predict what people will do... you just have to get in there and look and figure it out. The frunk amplifier may not work with the stock HU, so you might have to remove that as well, in order to get it all working normally again.

In the end, there are lots of variables... you just need to dig in and see what's up.

EDIT: Forgot to mention... in my brief reading on the matter, the Bose systems are very annoying to work with. My car happened to come with a Bose + Pioneer setup, and whoever did the work did a good job... everything is working. The Bose complicates things, so you never know what was/wasn't done in there... and what was/wasn't done properly...
 

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The key here is that you have/had a Bose system. That is an optical system, which means the "sound" travels via light signals instead of electrical signals throughout parts of the system (from head unit to amplifier). Putting an aftermarket head unit into a BOSE car can be done in one of two ways:
1. A special MOST amplifier is used between the head unit and the BOSE amplifier. This new amplifier converts the electrical signals out of the aftermarket head unit to optical. Then the BOSE amplifier does what it previously did and feeds all of the (special) speakers. This is an expensive solution but maintains most of the BOSE system.
2. You rip out the entire BOSE system and replace it with aftermarket. You end up changing the speakers when you go this route as the BOSE speakers are not "standard".

If you get to the point where you believe your amplifier is working, a quick way to test whether your one door speaker is blown or not is to simply put a 9V battery (like your home smoke detectors use) across that speakers terminals. If you hear a tick it is good. If you don't, it is bad. Unfortunately you need to get to the speaker which requires pulling the door apart. Debug everything else first. First step, try to figure out whether the previous owner used method #1 or #2 above.
 

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Discussion Starter #4
Amazing responses. Thank you.

I will buy some audio prying tools, and try to figure it out. I’m pretty sure there’s a wiring issue as the speaker should be fine. The amplifier looks to be of good quality and I doubt the PO ripped out the speakers and such (if it helps, the Bose speaker between the seats work)

Also I do have the xenons but never experienced any hissing before in any other car. Not a big issue, but thought it might be a cause of the speaker not working.
 

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If you check the speaker coil resistance with a plain old DC ohmmeter, what most of us have in our toolbox, you'll get a few tenths of an ohm. Not 6 to 8 or even 2. This is still a good way to check for a blown speaker as it will be an open circuit if blown.

To measure speaker impedence you need a special meter that inputs an AC signal. Or do it the old fashioned way with a frequency generator, amp, AC voltmeter and ammeter along with Ohm's law..
 

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Does the ripping out of the bose system work the same on the 981 cars? That is something I can do and go fully aftermarket with a pair of nice components, small sub, and carplay headunit for about the same price as buying the $900 kit to maintain the Bose speakers and add a carplay headunit.
 

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Does the ripping out of the bose system work the same on the 981 cars? That is something I can do and go fully aftermarket with a pair of nice components, small sub, and carplay headunit for about the same price as buying the $900 kit to maintain the Bose speakers and add a carplay headunit.
Don't forget all of the speakers, which requires you to rip up your entire interior. The Bose speakers are not standard impedance.
 

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If you check the speaker coil resistance with a plain old DC ohmmeter, what most of us have in our toolbox, you'll get a few tenths of an ohm. Not 6 to 8 or even 2. This is still a good way to check for a blown speaker as it will be an open circuit if blown.

To measure speaker impedence you need a special meter that inputs an AC signal. Or do it the old fashioned way with a frequency generator, amp, AC voltmeter and ammeter along with Ohm's law..
I partially disagree. Yes, you're not going to measure full performance of the speaker with a meter, but you also won't get "tenths of an ohm". We're not looking for performance of the speaker overall, and are looking to check the coil, for which this is a reasonable test. I think we agree that this will tell you if the speaker is blown or shorted. Either way, you don't have to believe me, you can see this test is recommended here as well: How to Test a Speaker | Sweetwater

But, yes, I was wrong to state that it would be 4 or 8 ohms... my mistake.

The Bose speakers are not standard impedance.
Agreed on this too... I keep forgetting Bose does silly stuff with their systems. I've never been a fan of Bose systems...
 

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I partially disagree. Yes, you're not going to measure full performance of the speaker with a meter, but you also won't get "tenths of an ohm".
Correct. In fact just last week I pulled one of the rear mids out of my car with SPP and measured the coil resistance at 6 Ohm.
 

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Interesting. Learned something new contrary to experience or anything I've read. I measured a sub that uses an external crossover so nothing in the circuit but a fuse and the voice coil. Speaker is a nominal 8 ohm impedance and measured 5.8 ohms DC.

Still don't understand why it's not uncommon to have speakers with a nominal 8 ohm impedance that drop to 2 ohms at places in the audio range. Yet you get reasonable coil resistance.

I imagine that the reason Bose and others use low impedance speakers is a cheap way to get power with 12 Vdc rails in the amp. They probably have current limiters that kick in after a few seconds to keep the amp in the frunk from melting down . Also keeps the speaker wires from frying.

Look back in this forum some years. I recall someone replacing the Bose amp with a standard one and not having issues with the Bose speakers. Well other than ground loops and some alternator whine to chase... Not a problem when the amp is optically coupled with MOST.
 

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There's actually a much better/detailed explanation of impedance/resistance here: How To Tell The Impedance of A Speaker - A Guide For Everyone along with a list of what you should see with a DVM.

They also go into the explanation of why this happens - basically, it's due to inductive reactance. A DVM only reads resistance, really, which is why the number is different... and in AC waveforms the inductance changes depending on frequency, hence the changes of impedance throughout the range of frequencies.

I agree, Bose probably does this to make things cheap. I actually have been to the Bose factory in MA (as an engineer they brought us there for a tour). Their speakers are garbage and VERY cheaply manufactured. The real tech is in the bandpass filter boxes they make around them... and crossovers to prevent damage to the speaker. But that's exactly why I don't like their speakers, because bandpass speakers typically have very notchy performance, so they're great for a narrow range of frequencies, and then do nothing everywhere else. This means my favorite low frequencies (midbass levels) are ignored and often missing. And in the case of my Boxster, which has a Pioneer HU now (came that way, so I don't know how it's wired in the back, but it works so I don't care)... there are certain songs and frequencies where I can hear the speaker distorting like crazy, which means I have to turn the volume down. So annoying. Eventually, I may do a frequency response (cheaply, using a phone or something) and see if I can figure out which frequency is causing the problem and tune it out...
 

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I suspect that the deficiencies in Bose is what drove the Burmester option. Wish it had been available in 2008.

I've always wondered if the Bose amp and its special equalization for the Cayman's cabin wasn't redone from the Boxster. But not enough to check PET.

If it helps any the impression I get from all the threads I've read on Bose upgrades is that the head unit is the weakest link followed by the speakers. Rather the inverse of usual. I've not upgraded so no direct experience so YMMV.
 

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The problem with "upgrading" on most Bose speakers (particularly with ones inside any sort of enclosure) is that you will not get the proper behavior from such a system. Enclosures are made for a specific performing speaker, particularly bandpass ones, which is what Bose loves to use. If you change the speaker for something "better" it won't work the same, because you can't retune the bandpass. Normal speakers, sure, you can replace those... probably makes sense to do that, since Bose raw-speakers are not very good... but, again, now the "tune" of the system (Bose loves crossovers and DSPs) will make the better speaker sound poor.

IMO, it's best not to "upgrade" the Bose systems, as they are heavily tuned in various ways to their own speakers. Deviating from those speakers makes for a bad result. Again, one of the many reasons I hate Bose systems. A quality set of "standard" speakers will generally outperform Bose.

I actually used to sell speakers back in the day, and one of the brands we had were Bose. In most cases, when I showed people a quality other-brand (eg Jamo or NHT to name a few) the people would hear the massive difference and go with them instead.

Granted, in a car, Bose does a good job tuning the system to work well in that difficult environment, but so do many other companies (I recall Nakamichi systems in Lexus, which sounded incredible). Compared to a thrown-together set of speakers, there's no contest. But if I can avoid a Bose system and get any other brand, I will.
 
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