'89 Convertible Sound System Help

[eco325iX]

Hello R3V community,

I have an ‘89 E30 vert with the original BMW Sound System, however the PO made some modifications that I am trying to revert back to somewhat stock. The head unit is the BMW Alpine CM5908, which is paired with the BMW Blaupunkt QuadroBoost amplifier in the trunk. I believe the first owner (I am now the third owner) added a genuine BMW 12 disc CD changer, which is mounted underneath the convertible top storage area in the trunk along with the addition of a Zack Morris brick style hardwired mobile phone, the phone was removed by the second owner, but the antenna and coaxial wiring in the trunk are still present and need to be removed. The second owner added a giant subwoofer box in the trunk, which he kept as I have no need for, but left all the wiring in place. The sub's wire gauge was almost 3/4" in diameter, which was directly connected to the battery in the engine bay with a giant in-line fuse, then ran through the footwell firewall and then back to the trunk. I removed this wiring along with an air raid style horn that was in the engine bay with a sensor that detected if the car was being lifted, which triggered a blaring alarm, ask me how I know... it went off when I was removing the level sensor. Four of the six speakers are blown as the PO used to live in Vegas and cruise the strip, while the E30 was a low rider.

My plan is to resto-mod the E30 back to OEM+ (lots of projects to do...). As it's now spring and summer is quickly approaching I am taking my wife and children out more to cruise and grab ice cream and they like the creature comforts of music and not just the wind and exhaust like I do. I want to keep the original CM5908 head unit and have it converted to Bluetooth (most likely Cantaloupe) to keep the stock appearance and functionality. Since only two speakers are working I clearly need to replace all six, I've been researching speakers on Crutchfield as I am into music, but not an audiophile. I’m looking for good-to-great sound, not top tier bragging rights that wins awards. I would like to keep the speakers the stock sizes and not cut any sheet metal to increase their size.

Here's where I need help and I am becoming more confused with all the threads I am reading here on R3V and other BMW forums, the HU and/or amp must be in need of repair, why do I suspect this, because sometimes there is sound from the radio or cassette player which seems to be working okay with what life is remaining in the two speakers, then all of a sudden the system goes haywire and sends out alien signals, like a blaring high pitch noise that destroys your ears or a deep pulsing sound that is also loud and disturbing. Here is what I have checked and tried to do so far:

+ The original radio antenna grommet was falling apart, which I replaced with a genuine BMW grommet. I initially thought that the metal antenna touching the sheet metal body this was causing the sound frequency issues, but after replacing the grommet the problem still persists.
+ The ground cable from the hood to the chassis is still in good shape, are there any other grounds for the sound system that I should inspect?
+ I pulled the on/off volume control knob off of the HU and tried spraying some compressed canned air into the pot, then tried electrical contacts cleaner and spinning it to clean off any corrosion or dust. The problem still persists.
+ I pulled the amp out of the trunk and opened it up to see if anything looked unusual or melted, everything seemed fine so I reinstalled and tested again, the problem still persists.

I did notice that there is a screw with what looks like two grounding wires that were clipped and currently attached to nothing, which is screwed into the trunk wall underneath the amp, this did not look like it was stock, it was probably added by the PO when he added the bass cannon.

I am starting to think the HU or amp is faulty as they are almost 38 years old. Any suggestions?

[PDX_MTECH2]

The audio issue would be easier diagnose if more working speakers were connected. I'd be curious to know if the blaring high pitch noise was present on all channels on the amplifier or just the front or vis versa. My guess is the amplifier is going bad. Electrical components can degrade over time. IIRC, the radio outputs a single left and right signal that then goes to the fader switch. Fader switch is known to go bad but that would present a sound similar to a scratching noise or slight pops not the noise you describe.

In regard to replacing speakers, the issue I've seen is most manufacturers stopped development speakers in the sizes that these cars need. The selection of 5.25" speakers is slim picking. The front kick panel speakers sit very close to the plastic trim which is why the OE used an inverted surround on the speaker. To my knowledge there not any speakers that incorporate this style surround in a 5.25" speaker anymore. BMW does still sell OEM speakers for our cars but they are a tad pricey in my opinion for what they are. OEM replacement would be tried and true while potentially giving you the result you're looking for. The rear speakers are a 4" I think.

Here is the part number for front kick panel 5.25" - 65131386546

Link to purchase
https://www.fcpeuro.com/products/bmw...0w-65131386546

[eco325iX]

Thanks for the feedback, but now I am even more confused. I was under the impression the CM5908 did not have a fader switch in the late model vehicles, or am I wrong?

In regards to the 5.25" speakers, when I enter in my vehicle's information on the Crutchfield website they list 45 speaker options for the kick panel zone. You're telling me none of these speaker options will fit? If so, they need to update their website.

When I was looking in realOEM I found a diagram that listed the front and rear speaker as part # 9 with the following part # 65131386541 which lead me to believe the front and rear speakers were the same in the convertible.

[reelizmpro]

Front and rear speakers are not the same in a convertible. The front speaker is a premium speaker with passive crossover for the tweeter and plenty of room. The rear speaker is a midrange shallow speaker to clear the window mechanism. This is where it gets kinda tricky finding an aftermarket replacement that fits. I used a 2 way mid with a small/medium magnet (Alpine SPE-5000)

[eco325iX]

Okay this is starting to make sense, realOEM has two speaker wiring diagrams for my vehicle, one diagram that list the front and rear speakers as the same part number and the other diagram that illustrates them inside a coupe or sedan silhouette with the front and rear speakers with different part numbers. For the diagram that lists them with different part numbers this is what I am seeing:

Fronts listed as diagram part # 8, with a BMW part # 65131386546
Rears listed as diagram part # 17, with a BMW part # 65131386541

So the front speaker is deeper than the rear speaker? Maybe this is why Crutchfield lists 45 speaker options for the kick panel area and 2 speaker options for the rear? The Alpine SPE-5000 is no longer available.

[PDX_MTECH2]

I apologize, you're correct about the fader switch.

Yes the rears are different, as the previous person stated to clear the window mechanism. RealOEM was giving me conflicting results but I think that was user error . The correct one is the one you listed above #17 with a BMW part of # 65131386541

Crutchfield's site will populate with options that there system says will fit just based on the bolt pattern which is a 5.25". They will physically fit the hole but not the application. The point I was trying to make is that the OEM has a reverse surround to provide more clearance between it and the panel when the speaker is moving in the XMAX. Traditional aftermarket speakers do not have this reverse surround so it places that rubber surround closer to the panel where it will likely hit or rub.

[eco325iX]

No worries about the fader switch, I'm no expert when it comes to car audio systems, hence my questions.

Correct me if I'm wrong, but from what I am understanding thus far is that the two of you are saying the only option for the rear speaker(s) has to be the genuine BMW speaker, which is part # 65131386541 and I can choose any of the 45 speaker options for the front speakers. Is that correct?

[eco325iX]

I did some looking around for those genuine BMW speakers, both are still available at GETBMWPARTS.com however they are rather expensive...

Fronts: BMW part # 65131386546 = $149.42 per speaker
Rears: BMW part # 65131386541 = $140.56 per speaker

Roughly $600 for the 4 speakers before tax and shipping, and from what most people say they are not the best sounding speakers. This lead to me to this thread, which is rather old at this point:

https://www.r3vlimited.com/board/forum/e30-technical-forums/convertible-technical-discussion/334976-fitting-rear-speakers

I tried to look up the speaker models listed within the thread only to find they are no longer available, no surprise there. However, the JVC's lead me to these newer JVC CS-DR521 which are available. Does anyone have these fitted into their convertible rear armrest area?

[reelizmpro]

Yeah, they want crazy money for original speakers but there really is no need. There are a few aftermarket speakers that will fit, you just have to find them. Audio suppliers discontinue speaker lines all the time, tweak them a bit and rename them. All you need is a shallow/smaller magnet midrange speaker.

Here's what AI says...

The closest direct equivalents to the 5.25-inch Alpine SPS-500 Type-S speakers are the updated Alpine S2-S50 (Next Gen S-Series) or the discontinued Alpine SPS-510. These provide similar power handling (approx. 50-55W RMS), shallow-mount designs, and silk dome tweeters for smooth high-frequency response.
Crutchfield +3
Comparable Alternatives (5.25-inch Coaxial):

• JBL GX502: Often considered for similar 2-way performance, featuring 5.25-inch, 2-45W RMS handling, and an edge-driven soft dome tweeter.
• Kenwood KFC-1366S: 5.25-inch 2-way coaxial speakers often used as a direct, affordable upgrade.
• Focal or Morel 2-Way Series: Higher-end alternatives offering similar 2-way, 5.25-inch configurations, though often at a higher price point.
  eBay +2

Key Specs to Match for Equivalent Sound:

• Size: 5-1/4" (5.25-inch) coaxial 2-way.
• Power Handling: 50-80W RMS (SPS-500 was 50W RMS).
• Materials: Silk dome tweeter and rubber surround for durability.
  Crutchfield +2

The current Alpine S-Series (S2-S50) is the best replacement for maintaining the same sound profile and fitment.

[reelizmpro]

5.25" Alpine SPE-5000 on ebay...

https://ebay.us/m/WpXEwi

[eco325iX]

reelizmpro, thanks for the suggesting the Alpine S2-S50 speakers.

I removed my passenger side speakers to get a better understanding of the sizes. Here are some photos to compare the tweeters, front kick panel and rear armrest panel speakers (from left to right in the photos) for anyone that is undertaking this task in the future.







These are all original genuine BMW speakers. Notice the front and rear are almost the same depth. The rear was measuring roughly 2-5/16" to the top of the brass mounting clip, which mounts inside of the rear back panel, whereas the front mounts onto the sheet metal (towards the inside of the cabin).

[eco325iX]

reelizmpro, is there a corresponding Alpine speaker for the front kick panel that would pair well with the rear Alpine S2-S50 speakers? And would component speakers be ideal to replace the tweeters in the pods?

[Vincenze]

The E30 sound is a two-way system: a tweeter and a woofer.
The red wire around the woofer plus a capacitor is a crossover to split high frequencies that go to the tweeter and low frequencies that go to the woofer.

It looks like your rear woofer doesn't have a crossover unlike the two-way rear speakers in a coupe.

The Alpine speaker that you show has a more complicated design that has both a woofer and a tweeter in it; thus, it may reproduce a wider frequency range, but it's taller.

There are laws of physics.
If you want lower frequencies, you must use bigger woofers, but you can't due to the size limits.
If you want higher frequencies, you may change the tweeter, but the current one is Ok.

You can connect any sound signal to your speakers and test them.
Then, you can connect it to the 4 output wires from the headunit and test the amplifier. You must provide +12V to the white wire that turns on the amplifier.

There are cheap TDA2030 amplifiers for testing on Amazon, eBay.

[reelizmpro]

reelizmpro, is there a corresponding Alpine speaker for the front kick panel that would pair well with the rear Alpine S2-S50 speakers? And would component speakers be ideal to replace the tweeters in the pods?

I'm sure Alpine has a component set that matches up well but in all honesty...the stock premium front speakers are fine as long as they aren't blown. So I left them alone and just changed the rears to 2 way.

[eco325iX]

Guys, I appreciate all the advice and thanks for hanging in there with me. Surprisingly this is the first vehicle that I have ever had that has audio problems, so this really isn't my wheelhouse. I watched some YouTube University videos about testing speakers with a multimeter and 9 volt battery. The following readings are for the passenger side speakers:

Door pod tweeters listed at 8 ohms ~ tested at 5.8 ohms
Front kick panels listed at 4 ohms ~ tested at 3.9 ohms
Rear armrest listed at 4 ohms ~ tested at 3.4 ohms

All the speakers moved inward and outward when you switch the + and - terminals on the 9 volt battery.

I would say that these speakers are in okay condition according to those tests, it must be the head unit or amp. I'll test the drivers side speakers tomorrow.