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High-cut/Gain Subwoofer Adjustment

18K views 18 replies 9 participants last post by  slaskey099 
#1 ·
Anyone made any adjustments to either of these trim pots on the Sub amp (HK) under the seat? The factory set for gain "looks" to be set towards the louder setting. The High-cut (crossover frequency?) has no reference point.?
 
#2 ·
Well, That question went over like a lead zepplin. I am a bit surprised that with all the questions/complaints about the HK sub that nobody has fiddled with the adjustments on the amp. The next dry day I guess I'll have to park in the driveway and see if I can get a good open door look at the adjustment knobs under the passengers seat and give it a go.
 
#4 ·
I'm not sure. I've only looked at the amp while kneeling in the drivers seat and leaning over the center console. Not the best position for exploration. From what I can see the "front" of the amp facing the front footwell has the plug connections. The side to the driver has a bit of a metal shroud and no trim pots are visable. If it is that side it might be tough to make any adjustments. My hope is there is a clean shot from the passenger door side. I'm still waiting on a dry day to spread out on the driveway.

Maybe someone who has done an aftermarket stereo install and taken out the seats can chime in?
 
#5 ·
Well my curiosity got the best of me so I grabbed a bathmat to put on the wet driveway and went in for a close look at the sub amp.

The front (dash) side is all the wiring harnesses. Drivers side is blank as is back side. The side towards the passenger door is where they are located towards the back.

There is a raised face plate across that whole side of the amp with access holes stamped into it. The hole over the forward most trim pot lines up perfectly. However you cannot get a straight look through the hole to see much of any thing. The faceplate casts a shadow on the side of the amp where the adjustment is made. The side seat trim blocks any straight on view.

The rear trim pot is even worse as the hole in the faceplate doesn't even line up. Maybe with a straight on look (with flashlight) it could be adjusted.

It is my conclusion that even though there are adjustments available they are not operator accessable. Bummer.

Has anybody taken the seat out and seen anything different at a better angle?
 
#6 ·
I too am going to have to check this out in detail, your right if we ever get a dry weekend here in Nor Cal I just might pull the seat altogether and get a closer look myself. Id be lying though if I wasn’t scared to mess with it, I personally like the way mine is tuned. Mine is set up like the exhaust on the late model Ferraris, it’s quiet at idle to mid range but at WOT there is thunderous bass. In short with the wife and toddler in the car I can listen to music and not bump them out of the car, when it’s just me turning the sound up past 28-30 and I get monstrous bass.
 
#8 ·
I have the subaru subwoofer in mine and the crossover and gain controls are on the side towards the passenger. I was able to adjust them with a stubby phillips screw driver, careful they are plastic. There's no real reason to see them since they are just arbitrary adjustments but I'm sure you could use a small angled mechanics mirror if you really feel the need to see which orientation they are in.

For what it's worth I adjusted the crossover as high as it would go and then adjusted the gain (volume) to a point just below where it clips with bass heavy music. It sounds OK - nothing spectacular but an improvement.
 
#9 ·
Wow, Post #7 really had me turned all around.:gasp: Post #8 has me back on track. I think.

I went back to a Subaru install pdf file I downloaded onto an iBook I use while watching TV. I wanted to attach a link so everyone could see what the he** I've been talking about. That file on page #10 shows the trimpots and gives a picture of how they are set at the factory + a wave form chart showing how much the crossover and gain can be changed. Great stuff.

I am now on my PC and downloaded what I thought was the same Subaru pdf file. Guess what? Same file, but no page #10. Everything else is identical and I am so iBook retarded I don't know how to move that file to my PC. Ugh!

Seaweed,
I moved the passengers seat all the way forward and looked again under the seat and there appears to be a plastic "protective" cover over the top and sides of the amp. Like a shoe box lid. There are 4 torx screws in the top of the amp holding it in place. Did you remove that cover? The reason I ask is this is what is blocking a good view of the door side of the amp. Also I stuck my pinkie finger into the hole for the adjustment and it was deeper than a stubby screwdriver with cover attached.

Well now that I have my OCD in full gear, back to the trimpots for anyone still (if ever) interested. Both appear to adjust from "7 o'clock to the left and 5 o'clock to the right".

The one towards the back seat is the crossover/high cut. If I am reading the chart correctly it can be adjusted from about 130hz to about 350hz. Doesn't look like it's really a true sub-woofer? The factory set is at 2 o'clock.

The other one is the gain/volume. Again if I'm reading correctly it can add from 0db to about +25db. The factory set is 3 o'clock.

Conclusions/guesses: I would think that setting the sub at the lowest 130hz setting would put the 130+hz frequencies to the more able front door mid loaded speakers and let the sub deal with the truly lower frequencies. To me that would keep the sub from clipping trying to reproduce the lower frequencies and the mids at the same time. I believe that would also allow for a boost in the sub's gain w/o any ill effect/clipping. To my ears the HK has always been a bit weak in the low mid area. Maybe shifting those frequencies from the sub to the front doors would fill in the gap? But then again they were set at the factory for a reason.
 
#10 ·
OBnube/Seaweed,

Thanks for the info. I was looking at my amp tonight and have two questions:

Do you know if the gain adjustment is for the subwoofer only or across all speakers? I'd like to increase the gain on the sub a bit as I barely hear any output even with the stereo at high volumes.

Also, were the knobs hard to turn with a screwdriver? I was able to get a small screwdriver lined up in the notch to make the adjustment, but I could not get it to turn. Since it's plastic I didn't want to put too much pressure on it, but typically these adjust pretty easily on other amps.

Thanks.
 
#11 ·
OBnube/Seaweed,

Thanks for the info. I was looking at my amp tonight and have two questions:

Do you know if the gain adjustment is for the subwoofer only or across all speakers? I'd like to increase the gain on the sub a bit as I barely hear any output even with the stereo at high volumes..
I believe it is only for the sub. I think the others are driven by the head unit. The less rear fader you use the more bass you will hear. From 0 to any plus (front) setting doesn't seem to increase bass any more.
Also, were the knobs hard to turn with a screwdriver? I was able to get a small screwdriver lined up in the notch to make the adjustment, but I could not get it to turn. Since it's plastic I didn't want to put too much pressure on it, but typically these adjust pretty easily on other amps.

Thanks.
I have to defer to Seaweed on that one as I haven't adjusted mine yet. One possible caution, I do not know if they can be adjusted past "5o'clock". The factory set for gain is 3o'clock. That doesn't leave much room left to turn.

Since you have gotten further along than I have could you answer a couple of questions for me?

1. What position did you put the passengers seat in to get a good look?

2. Did you take off the plastic cover from the amp?

3. If not, were you able to get a screwdriver lined up on the rear crossover trimpot? The plastic cover hole is offset a bit and I can't seem to get a good look at it.

Thanks
 
#13 ·
Mine is a premium and I installed the tweeter kit and subwoofer kit from subaruonlineparts.com myself. So I have no idea if the HK sub is different or if so, how to adjust it. To access the gain/crossover adjustment I put the drivers seat all the way forward and all the way up with the power adjusters. It is still tight but my stubby philips fit in there - a very poor design for sure, it would be nice if you could see them but not necessary. There was very little resistance in the adjusters but with a light touch I could feel both ends of the adjustable range of the plastic "knobs."
 
#14 ·
Thanks for checking back in. Yours is different than the Limited trim. My amp is under the passengers seat and has that aggravating plastic cover. Not having any up and down seat adjustment only adds to the frustration. When I get the chance(dry day) I'm going to remove the plastic cover and with a small mirror scope out the amp in detail. The pdf file I have been referencing is for your style sub. It might be that the Limited sub amp has no adjustment other than in the head unit. Your info/input helps either way. Thanks
 
#15 ·
OEM Amp/sub under passangsr seat


This thread from awhile ago I know but I just wanted to add my 2 cents anyways. The sub/amp under the seat depends on the model of outback and thr stereo options that were added at the dealership. I found site that breaks down a stereo options for the gen two 2000 outback and outback wagon. I cant find the line right now but a simple google search should find it. The screw placement for the gain and high output is on the left side of the unit itself of you are seated in passenger rear seat. If you push the seat forward the amp/woofer is easily or should be easily accessible. They gain and the output do make a difference in stereo sound and bass. Turn your radio on and leave head unit in preferred setting that it is set at normally . Put on a song or CD with lots of bass....grab a small screwdriver and adjust the settings to your bass preference that you like. With the other setting adjust and listen if the sound gets distorted or cracks. Turn the switch back a little until sound quality is okay with you and ears. This is my first time responding to anything here so hopefully I helped.
 
#16 ·
Whew, It has been a long time. Thanks for the response and welcome aboard. On the Gen 4 the information I got was the factory Harmon Kardon amp has no trim pots at all on the amp. The factory accessory amp does have the two pots. Too bad they didn't put the adjustments on the supposed upgraded amp.
 
#19 ·
This is an OLD thread so - hope you get this. My 2013 Limited with HK and Navi, I have pulled the sub from the back, removed the wire harness from it - dual voice coil 2 ohm sub, CONNECTED a Line Output Converter, and run the LOC to a 800W 2 channel amp bridged. To be useful, the LOC is adjusted to minimum sensitivity - ie it takes a higher level signal reduces it the most it can, the AMP is also set to MINIMUM GAIN - If i had a 150W amp it would be better, Crossed over the amp at 100,

The amp feeds an 8" Skar 2-Ohm dual voice coil sub wired in series to increase the impedance to 4 Ohms, this is then run in Series with a Kicker 10" sub ( both are in smallish separate ported boxes - wedged together so they fit tight behind the seat and wheel well to wheel well )

The change in sound is incredible- The bass is extremely deep and tight - BTW the EQ settings on the head unit also have to be drastically altered 50 is normal, next is -5, next is -3 then normal, normal, +2.
The soundstage is moved back from the windshield, and down a little. The channel separation is now better, voices are clear, most music sound awesome - I listen to classic rock, bro country, and some gen 1 new wave ( cars, squeeze, elvis costello etc)

What is missing is any signal over 10,000 hz I put a sound generator on it and used a mic and sound pressure app and at 10K it completely cuts off. To test if the signal was there - I wired an old Hertz 1in tweeter in parrallel into the drivers dash speaker and it does get up to about 12k but very faint.

Next step - is to A) replace the driver door speakers with some infinity 2 way, and then CHANGE THE PINOUTS ON THE AMP to duplicate the feed from the rear doors to the Front Doors - this should give a full range signal to the front doors. IF that proves successful, then a smallish 4 channel amp with line level inputs is the next step - adding power to the door speakers
Hope this helps
 
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