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I just had this reply from a US member..... Now this all seems a little complex for a novice like me, but I hope that by adding the tweeters (like I have) I will not do any damage to my amp!
Hi Richard
The main problem here is not the filters of the THA475, is the way that you connected the OEM speakers to this aftermarket amp, specifically the front speakers.
Your base system originally have the underseat subs connected in parallel to the front full range 4" drivers. There is a capacitor inline between the 6.5" underseat woofer and the 4" full range driver which accomplishes two jobs: keeps the total impedance in 4 ohms and separates the low frequencies (woofer) from the mid/high frequencies (4" full range).
By adding an extra set of tweeters to the front speakers you effectively changed both the impedance and the frequency filtering.
The filtering can be fixed, but the new impedance can damage your THA475 if it goes below 2 ohms, which it is in fact 1.33 ohms with the new tweeters at least. The amp will eventually overheat and fail if it is drawing too much current due to the low impedance.
If you do not understand all this mumbo-jumbo of technical information at least understand this: you cannot set this THA475 and the front speakers the way you did.
You will need to connect the THA475 4-channels only to the front speakers:
- channels 1-2: connect them to the front 4" full range driver and the new tweeters. Set the THA475 front filter to high pass, at around 150Hz.
- channels 3-4" connect them to the underseat woofers. Set the THA475 rear filter to low pass, at around 150Hz.
The rear OEM speakers will be driven by your OEM HU/iDrive unit.
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