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Discussion Starter #1
Thought I'd start my own thread here, rather than clutter Scott's amazing thread on his stereo!

I have a Forester 2.5i-S which has the 9-speaker Harmon Kardon system. To me it sounded like it was missing some frequencies, and although the bass is nice and punchy with great timing, doesn't extend enough for some of the music I listen to. On the other hand part of the premium for this model was getting the upgraded stereo so I also don't want to rip it out and spend a fortune!

The first step to making changes to something, be it sound or otherwise, is to know where you're starting from. And so I've done an acoustical measurement of the base system, unmodified. The readings mirror my thoughts on the sound, with a gradual but dramatic roll off down low, but also some surprising, and significant dips at 430Hz and a voice-critical 1,500Hz. There are also some between 2.5 and 3.7kHz, again right in the vocal region.

Now again, I really don't want to mess at this stage with the rest of the system, where DSP could easily correct the higher frequency issues to an extent. But at the bottom end I'd like to see if I can achieve a more gradual roll-off down to say 40Hz (-3dB). It's currently sitting at 55Hz (-3dB).

I haven't decided which way to attack this yet. My thoughts deviate from replacing the factory sub with a higher quality one, complemented with an external mono amplifier, to installing a 15" sub in a sealed enclosure. The first step for me is to run power to the boot, hook up an amp I have here, and take some more measurements utilising a 10" Seas SW250 sub I have in a small sealed enclosure. This will hopefully show the potential. If there is no significant change, I'll try some other no-cost experiments just to ensure I'm on the right track.

Any input is certainly welcome of course!
523873

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Get a set of the infinity 20mx or jbl version.. run it in the dash with high pass only.. should resolve your mid-range opportunity. I had some details on the install on the other thread.

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Discussion Starter #3
Ah saw that, definitely worth a go. Is the sensitivity similar?

I’m also concerned that the dramatic roll off at 40hz could be a global high pass filter. I hope not.
 

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Ah saw that, definitely worth a go. Is the sensitivity similar?

I’m also concerned that the dramatic roll off at 40hz could be a global high pass filter. I hope not.
90db and 2.5 ohm ensure it is very sensitive... I suspect it will be right at home, as the HK are pretty efficient. In the Rockford setup they are a little too efficient.. I ordered the Nappa 6*9 seperates tonight I may not use the tweeter but the 6*9 will be in tune with it to smooth it all out. They must be dropping a new line as well most infinity are on sale this week.
 

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Discussion Starter #5
Test fit to see if a dual 12” ported enclosure would fit. Ha just for laughs, doubt I’ll go this far!
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Discussion Starter #6
So today I wired up the car for an aftermarket sub. Ran power through the firewall, took the speaker-level signal from the factory sub at the amp under the seat, ran a trigger wire from the fuse box (15a power outlet), and connected to an AudioControl LC2i line out converter, into a Class D mono amp. I installed my Seas SW250 10" sub in a 25 litre sealed enclosure and took a measurement at the back seat, and then at the back of the boot facing the boot lid (which was better).

I'm glad to report that it doesn't appear to have a bandpass filter on the factory sub, but just a low pass which is what you want. Meaning that attempts to improve bass extension will not be futile. The graph speaks for itself, but a great result by going from the factory 9" to an aftermarket 10".

I'll most likely build a larger box for the 10 to suit the boot, and may also later try something fun like a 15".

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The lc2i should restore any gaps at the bottom end anyway. You could also grab signal off the deck vs Harmon side. I just basically replaced my Fosgate amp myself on the top end.. the RF would be perfect if you could adjust or reset the dsp, but since you can't when you start swapping speakers it's less than ideal, usable just not ideal. The kicker key amp is so ridiculously good and exactly what I needed to run my front and rears.. the 12" Cerwin Vega spare tire sub carries my low end. Pretty sick. Super happy. Have fun with your mods.
 

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Discussion Starter #8
Nah the AccuBASS on the LC2i only restores any bass that a HU rolls off as volume is turned up. It's only products like the Epicenter that uses higher order harmonics to 'rebuild' missing bass, but then you need a summing LOC (LC7i or higher) to utilise that. I found I couldn't use any setting other than zero on the AccuBASS otherwise there was distortion.

If I go front end mods I'll use a Helix DSP and amplifier, but hoping I won't need to go to that extent!

Bass-wise I'll probably end up with two boxes I can interchange depending on cargo requirements.
 

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Discussion Starter #10
Box building. I’m going to use a JL Audio 12tw3 sub which is compact. The idea is it can fit in the boot, but if I need the cargo space it will fit behind the driver seat or even in the passenger footwell.
I can’t stop bracing!! But the bracing is the key. It’s gone from a ringing scenario to sounding like concrete when you tap it.
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