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      01-17-2009, 06:42 AM   #1
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Exclamation Impendance, Alpine retrofit kit

After i read a lot about improvments caused by changing stock subs for SWS, i thought it would be nice to fit them to my car. I have already cleared that stock amp has got 2 ohms impendance, but what about the alpine amp from the retrofit kit(http://www.babybmw.net/forum/viewtop...f=29&t=11090)? which is already in my car, powering stock subs. Personaly i suppose it has got the same impendance cause it integrates in stock system, but iam not totaly sure, so please, i need your help
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      01-17-2009, 09:00 AM   #2
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Originally Posted by ysv View Post
After i read a lot about improvments caused by changing stock subs for SWS, i thought it would be nice to fit them to my car. I have already cleared that stock amp has got 2 ohms impendance, but what about the alpine amp from the retrofit kit(http://www.babybmw.net/forum/viewtop...f=29&t=11090)? which is already in my car, powering stock subs. Personaly i suppose it has got the same impendance cause it integrates in stock system, but iam not totaly sure, so please, i need your help
I would assume that if you are talking about the Alpine OEM retrofit amp your sound system is the OEM "Stereo System" (no OEM amp).

According to the base OEM "Stereo System" description, the 6.5" underseat OEM woofers are connected in parallel with the front OEM mids. To avoid causing problems of impedance to the OEM HU, a capacitor was installed inline with the OEM mid.

Because the OEM HU per channel power output is 15W at 4 ohms, that tells me that each front mid and the underseat woofers are 4 ohms, as connecting them in parallel will yield an effective impedance of 2 ohms without that capacitor. That means that the OEM HU is not 2 ohms stable and thus the purpose of the protecting capacitors to keep the impedance the the OEM HU "sees" at 4 ohms.

Therefore, if you are planning to swap the OEM woofers with the SWS-8 you will need to get the 4 ohms version of the SWS-8 to properly match the new Alpine amp output.

On a side note, I would like to know how this Alpine OEM amp retrofit kit compare in price with a Blaupunkt THA555, the PnP harness and a pair - or two- of OEM Logic7 mid and tweeter sets. I think that the THA555 is a much better amp in a Pnp configuration than that Alpine, as the THA555 is a 5-channel amp with plenty of power for the whole system (front, rear, underseat woofers) than the Alpine that only powers the front and the underseat woofers. I doubt that the Alpine amp puts out as much power as the THA555 as well.
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      01-27-2009, 05:39 AM   #3
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Quote:
Originally Posted by Technic View Post
I would assume that if you are talking about the Alpine OEM retrofit amp your sound system is the OEM "Stereo System" (no OEM amp).

According to the base OEM "Stereo System" description, the 6.5" underseat OEM woofers are connected in parallel with the front OEM mids. To avoid causing problems of impedance to the OEM HU, a capacitor was installed inline with the OEM mid.

Because the OEM HU per channel power output is 15W at 4 ohms, that tells me that each front mid and the underseat woofers are 4 ohms, as connecting them in parallel will yield an effective impedance of 2 ohms without that capacitor. That means that the OEM HU is not 2 ohms stable and thus the purpose of the protecting capacitors to keep the impedance the the OEM HU "sees" at 4 ohms.

Therefore, if you are planning to swap the OEM woofers with the SWS-8 you will need to get the 4 ohms version of the SWS-8 to properly match the new Alpine amp output.

On a side note, I would like to know how this Alpine OEM amp retrofit kit compare in price with a Blaupunkt THA555, the PnP harness and a pair - or two- of OEM Logic7 mid and tweeter sets. I think that the THA555 is a much better amp in a Pnp configuration than that Alpine, as the THA555 is a 5-channel amp with plenty of power for the whole system (front, rear, underseat woofers) than the Alpine that only powers the front and the underseat woofers. I doubt that the Alpine amp puts out as much power as the THA555 as well.
Ok, thank you for the info. As for retrofit kit, a have alredy installed it, and in comparison with stock it sounds much better (pure clean and power ok sound), but as for stock subs, they really can not coupe with increased power output, so thats why they also have to be replaced.

By the way, will SWS-8 be equal increase in terms of: stock mid-bass -retrofit kit mid-bass, stock subs - SWS-8 subs? Or they will outperform (sound louder then any other part of the system)?

And as for impendance, it is all clear now - 4ohms.

Concerning the comparison of retrofit kit with the variant you proposed - frankly cant say anything, cause iam not really an audio enthusiast, just a simple user...
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      01-27-2009, 08:56 AM   #4
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Quote:
Originally Posted by ysv View Post
Ok, thank you for the info. As for retrofit kit, a have alredy installed it, and in comparison with stock it sounds much better (pure clean and power ok sound), but as for stock subs, they really can not coupe with increased power output, so thats why they also have to be replaced.

By the way, will SWS-8 be equal increase in terms of: stock mid-bass -retrofit kit mid-bass, stock subs - SWS-8 subs? Or they will outperform (sound louder then any other part of the system)?

And as for impendance, it is all clear now - 4ohms.

Concerning the comparison of retrofit kit with the variant you proposed - frankly cant say anything, cause iam not really an audio enthusiast, just a simple user...
They should sound much louder than your OEM woofers, as the SWS-8 are 8" subs with a much longer cone extension than your 6.5" OEM woofers.

Do you have any technical information on this Alpine amp?
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      01-27-2009, 10:28 AM   #5
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Quote:
Originally Posted by Technic View Post
They should sound much louder than your OEM woofers, as the SWS-8 are 8" subs with a much longer cone extension than your 6.5" OEM woofers.

Do you have any technical information on this Alpine amp?
All i know is that this Alpine amp is class d and has 80w x4

If the subs are 8", how come they will fit in places made for 6.5"?

Are you totally sure about 4 ohms? I am asking again because i saw a topic were a man installed 4 ohms and due to high impendance, they volume was half of the normal...
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      01-27-2009, 10:59 AM   #6
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Quote:
Originally Posted by ysv View Post
All i know is that this Alpine amp is class d and has 80w x4

1) If the subs are 8", how come they will fit in places made for 6.5"?

2) Are you totally sure about 4 ohms? I am asking again because i saw a topic were a man installed 4 ohms and due to high impendance, they volume was half of the normal...
1) The OEM enclosure is the same in all 1- and 3 Series, regardless of the driver (6.5" or 8").

2) As previously explained, your Stereo System OEM front speakers are connected in parallel (the 6.5" woofer to the 4" full range driver). For them to be connected in parallel they must be at the most 4 ohms, just because in parallel their total impedance will be a maximum of 2 ohms. For them to be 2 ohms will equate to 1 ohm total impedance... neither the OEM HU or the iDrive computer are stable at 1 ohm.

The OEM HU is stable down to 4 ohms, the iDrive computer is stable down to 2 ohms, according to BMW.

Therefore, your 6.5" driver should be 4 ohms.

The only way to conclusively determine the impedance of your 6.5" driver is to measure it.
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