door speaker replacement

Weasel · #1 08-20-2008, 07:15 PM

The mid-bass speakers in the front doors of my X5 w/DSP started clipping on the bass notes, So I did some research on the better quality aftermarket speakers and ended up buying JL Audio VR650-cxi speakers as they have the cleanest bass response due to separate bass blocking capasitors for the tweeter and the woofer... the one on the woofer only blocking frequencies too low for the speaker to handle, thus letting it handle more.

My question is that the oem speaker is 8 ohms and I was wondering if anyone has used 4 ohm aftermarket speakers with the oem DSP amp without problems, or if I should just follow my instincts and buy the available resistors to drop it back to 8 ohms... thus avoiding possibly frying the expensive a$$ dsp amp. I figure enough people on this great forum have dealt with this for some quick advise, thanks!

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dkl · #2 08-20-2008, 10:48 PM

It's not as simple as adding in a series 4 ohm resistor with your speaker to make your 8 ohm. Noticed that the specification indicated is 8 ohm impedance, NOT resistance. Impedance is made up of resistance + reactance. Your "lump" series 4 ohm resistor will only contribute to the resistance part of the impedance equation. Unfortunately, there's no easy way to figure out what the equivalent reactance of your OEM speakers would be unless you have a network analyzer handy (or know how to use one).

BTW, those bass-blocking capacitor that you're referring to is nothing more than a passive cross-over.

Weasel · #3 08-20-2008, 11:21 PM

I just seem to remember seeing a "impedance resistor" sold at a car audio store to bring the ohm load back up when you wire up 2 dual voice coil speakers and want 2 ohms, not 1 or 4... I guess I am wrong in assuming these would be available for full range speakers, or are worth a damn for that fact... I guess what I am mainly asking is does anyone have basic 4 ohm aftermarket speakers in their DSP equipt BMW without problems with the amp. I would hate to overload the circuit and kill the amp... especially not knowing if it has circuit overrun protection.

dkl · #4 08-21-2008, 12:23 AM

BSW seems pretty confident that their 4 ohm speaker solution won't kill the OEM amp. How they would warranty that would be another question. Another issue that I see when driving a 4 ohm speaker with an 8 ohm Amp (impeadance mismatch) is that you won't get maximum power delivered to your load (speaker). You'll get a double whammy here. First, your 4 ohm speaker won't be as loud as it should when driven by an 8 ohm Amp because only half of the power actually gets delivered to your speaker. Second, your Amp will heat up more because half of that power that's supposed to be delivered to your 8 ohm speaker (now replaced with a 4 ohm speaker) is now being dissipated as heat in your Amp (thus shortening it's life). To get maximum power delivery, your source and load impedance must match. So, even if you add in a series "load" resistor (trying to match your amp), then half of the power will be consumed by that resistor, which turns it into heat and your speaker would still be only getting half of the power from the amp. Therefore...adding the "load" resistor will only help prolong the Amp life, but will still make the overall experience (sound-wise) pretty bad...depending on what's exactly is in that "load" resistor that may introduce other distortion factors.

To make a long story short, find an 8-ohm speaker

Weasel · #5 08-21-2008, 01:04 AM

Well, I guess all I can do is try. What gets to me is alot if the aftermarket speakers have dropped down to 2 ohms! And they all claim th be "fully compatible with all oem sound systems" claiming by having 1/2 the ohm load, it pulls "twice the power from your stock radio" which would spell a quick, heated, overload related death for the 8 ohm DSP amp... lets see them cover that one after their compatibility claim. But a true quality 8 ohm speaker has proven to be hard to find...

Weasel · #6 08-21-2008, 05:02 PM

Ok, new question. I decided to try the JL's I already have before getting the BSW's that I know will work... has anybody installed aftermarket speakers in the door period? The speakers will not clear the window or sound worth a crap if installed flush with the door... and don't look like they can be installed in the plastic mount of the oem speaker. Any ideas?

And to those of you who did the right thing and went with the BSW speakers, Do they come in the plastic adapters that mount to the door frame, or fit in the mount as a replacement for the oem speaker? Thanks!

Weasel · #7 08-21-2008, 05:28 PM

Ok scratch that last thing.. for some reason I thought the "top shelf" in regular aftermarket speakers would sound better than what I have... I was dead wrong. I just made some quick adapter wires because I refust to cut the harness in any BMW I own and just try one out while holding it... good sounding speaker, but sounded like shit compared to the OEM speakers. I am not so much surprised at the sound quality of the JL's, but was just reassured of the sound quality of BMW's DSP system!

I will inevitably be going with the BSW stage 1 upgrade, and apparently have some JL's for sale if anyone wants to upgrade the sound in their honda/ford/chevy? they're new, played for less than 20 seconds!

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