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McIntosh subwoofer hack


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Whilst I think think the McIntosh OEM sound system in my BH5 Legacy sounds pretty nice for a factory setup, I always thought the sub lacked a bit of punch. To compensate I find myself turning up the bass control but unfortunately this just ruins the sound. The sub actually seems to be quite effective when turned up and I like the fact it takes up no space in the boot.

If you also find your sub a bit quiet but don't want to replace it, this mod will sort it out. You won't believe your ears! ;D

The McIntosh EF-1080I amp sits under the drivers seat. Remove it and take it apart. Make a note of where each screw goes as they are not interchangeable; you can permanently damage the amp by shorting things out of you replace the screws incorrectly.

Find R519 on the underside of the PCB. It's a 10k SMD resistor near the power and speaker connector with 103 written on it.


Replace this resistor with a higher value to increase the gain. Don't leave it out of the circuit or it may overdrive the sub and do damage. If you short it you will mute the sub entirely.


After some experimenting I personally recommend 33k to get s good balance in sound. This should boost the sub by about 5.2dB. Feel free to choose any value you want between 10-100k.

You might want to use a potentiometer instead so you can adjust the sub gain as you please. If you do this, I suggest a 50k linear (type B) pot in series with a 10k resistor. Make sure you use shielded cable and keep the cable very short to help prevent any instability in the amp. Connect the cable shield to a suitable ground point in the amp and (ideally) a 100nF or similar capacitor between the cable shield and the pot casing to prevent ground loops.


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  • 4 months later...

Well, I've just done this mod. Those SMD resistors are A LOT smaller then I was expecting :o

I'm sure it'll require a bit of extra work when a few of the other bits (like using a capacitor between the shield and the pot etc) as I bought an rf choke rather then a capacitor and I wasn't quite sure how to wire it up.

But it seems to work :)

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Guest keltik

For the same reasons i ran the sub output wires from the McIntosh amp to the speaker level inputs on another amp under the passenger seat. I then use this to drive the sub in the boot so all the crossover levels stay about right.

I tend to listen at a level higher than than your average and found the factory sub didnt have a lot in reserve at those volumes.

Now im finding on some days to be overstressing the front tweeters. Interestingly, the woofers dont seem to have any problems with it.

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  • 11 years later...
On 4/01/2022 at 10:35 AM, kiwisurf said:

Old thread bump but does anyone know if this works on the BL BP shape legacy? I have the amp out and it is different than shown in the photos? Cheers. 

if you have the bp theres a adapter thing u can just plug in and put your own sub/amp

im not on here much so join the legacy loonies group on facebook and message me (im the admin) and ill show u what you need

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