[Badmunky]

Ok this is a repost from my build log as no one responded to it there and it really should have been posted here in the first place.

I just finished tuning the amp and box.
First off let me explain tuning the box because I know some will ask me what I'm talking about. Now this may not be the correct way to do it but it has always worked for me so I used this method again.
First you have to start when you build the box. I like to build the box about 20-30% to big for the sub I'm using. Then I add and remove Hard foam from the inside of the box until I get the box and sub tuned to what I like. In this case the whole back wall of the box now has 1/2 of hard foam glued to it. This changes the affective size of the box as well as adding a damper to the back wall of the box. As I said this may not be the right way but it was shown to my by a shop that was at the time well respected (now closed to economic reasons) and has worked well for me in the past.

Next I tuned the amp.

Now at low to moderate levels every thing is all good. But at higher levels I'm getting a bit of a distortion I cant seam to figure out.
It sounds at times like the box has an air leak. Now this is a sealed box and I have checked to make sure it is in fact sealed. I can find no air leaks of any kind and am 100% sure I have none.

Yet I'm getting this sound?

It only happens at certain frequencies as well. So some songs the sound is not there at all and others its there for most of the song.

Any one ever have this problem?

Here is a link to my build thread.
http://www.diymobileaudio.com/forum/diyma-build-logs/55791-2007-impreza-wrx-custom-10-sub-install.html

Thanks.

 

[mr1spd]

The only problem I ever had with a sub mounted that way is that. When you open the trunk the bass get about twice as loud. The install does look very nice though.

 

[Badmunky]

When I open the trunk the bass drops off by 20-30% actually.
opening a door on or window on the other hand dose increase the out put of the sub but dos not change the sound problem I have.

If this is do only to the way I mounted the sub then this is not going to work. Its driving my nuts!

Later.

 

[mr1spd]

Do you have a friend with a similar woofer that you could try out. That would be the next step I would take.

 

[mr1spd]

Also I would go to Rockford's site the have a box calculator that can calculate the exact volume of the box you have built. Here is the link Rockford Fosgate® - Woofer BoxWizard I hope this helps.

 

[Badmunky]

Box is the right size Im sure of it. And I dont have any friends that run a 10" sub. Every one has a 12" or 8" subs right now.

I have 2 12" Kicker Comp VRs that are basically new that I can us if I have to but I wanted to run this 10" sub.

I bout the kickers new in 06 and used them for about 3 months and less then 15 hours play time in my last car. They just dont go well with the WRX and I need trunk space so I wanted to run a smaller woofer.

But If I have to I will run 1 of the 12s.

Was hoping to sell them and there box thou.

Later.

 

[sqshoestring]

Can you determine if it is the sub or box or something else?

Nice install BTW!

 

[Xander]

Are you sure you're not just pushing either the sub or the amp too hard?

How much clearance is in front of the sub? Is it possibly hitting the backs of the seats at high excursion levels?

 

[Badmunky]

Can you determine if it is the sub or box or something else?

Nice install BTW!

I know there are no leaks in the box and it is the right size as well. Not sure about the sub as I have never used this sub before or known any one that did.

Are you sure you're not just pushing either the sub or the amp too hard?

How much clearance is in front of the sub? Is it possibly hitting the backs of the seats at high excursion levels?

Its tight but the sub is not hitting the seat. I removed the seat back and it sounds the same.

I thought I was pushing the sub or amp to hard but the amp is not even getting hot and was pushing a 12" sub that wanted almost 200 watts more power with no problems.
And the sub dos not sound distorted. It just sounds like I have a leak in the box or a lot of port noise.

Later.

 

[Aaron'z 2.5RS/WRX]

Can you push on the cone of the sub and have the box "deflate" so you push the cone in, and then it slowly returns to rest position?

If you can, the box has a leak, if you can't than it doesn't...

High volume, are you hitting the seatback at all? The subs surround would show signs of it if you were...

How is your gain set-up... did you follow a proceedure or did you just set it and call it good??

 

[Badmunky]

Can you push on the cone of the sub and have the box "deflate" so you push the cone in, and then it slowly returns to rest position?

If you can, the box has a leak, if you can't than it doesn't...

High volume, are you hitting the seatback at all? The subs surround would show signs of it if you were...

How is your gain set-up... did you follow a proceedure or did you just set it and call it good??

First as for the leak test I did that and if I hold the cone in fore 15sec and then leg go it pops right back out.

So Im sure there is no leak in the box.

The vary outer part of the surround can touch the seat back at high volume but just barely. And removing the seat back did not remove or have any change to the problem.

As for setting the gain, I started by maxing the gain on the Sub out line on the CD player. Then I set the gain so that at the max I can run the CD player the sub was seeing about half what I thought it could take.
That had the gain at about 1/4.
After a few weeks and many hours of play time I retuned the amp and made some changes to the box as I said in post one as well as changes to the amps EQ setting. At this point the gain is at about 2/3s.

The CD players gain is now at about 3/4-7/8 so I can add more if the station I"m listening to needs it.

Here are some pics of the amp Im using as well as the specs I have.


50 x 2 @ 4 ohms
100 x 2 @ 2 ohms
200 x 1 @ 4 ohms
400 x 1 @ 4 ohms PEAK

I got the pis from here\/
http://www.diymobileaudio.com/forum/classifieds/55129-fs-memphis-16-page-ranking-200-2-165-obo.html

But its the same amp and same specs.

And here are the specs for the sub.

T6104 10" Subwoofer 4 Ohm 31Hz-150Hz 250/500 87.1dB 2" 33oz. 5 1/8"

So I was wrong about the subs RMS power. I thought it was 150 and its 250.
But this amp should be able to put out 200-250watts RMS so it should be a good match.

Thanks.

 

[sqshoestring]

You can roughly check for clipping of the amp by playing about a 45Hz tone on repeat, the run the gain up unit you hear a metallic sound from the sub. That would be clipping and the sub will not travel much more after that, it will get worse sounding. Of course don't do it for long and don't do it at all if you are exceeding the sub's ratings a lot. Only takes a few seconds to hear it. You should be able to run that much gain (if you do it w/HU volume at max you run, and shut down high amps or make sure tone is well under the xover for them) easily on music as only real bass heavy music will load it that much. But I tend not to over amp my subs so I can do this. If you are at xmax doing above, then your amp has more power than the sub can handle in that install. Just playing a tone can also help you find noise issues and where they come from. Make sure your enclosure is not moving too. I had a mtx 4500 10 on a smaller amp that sounded nice in a small sealed, better than a bunch of 12s I tried in a larger box. It had less output, but I have to say it worked really well. Only a 225rms sub though, and I used no stuffing like I often do.

If the amp is clipping, it can make some strange sounds. If so it will only do it at high output and typically you can't get much more output beyond that without huge distortion and not much more xmax providing the sub has some left. You have to watch the cone. Some amps the power light will dim. Also test the voltage at the amp when you do it, if it drops past what your wiring should give then that can cut the amps output fix the wiring. If the amp is dying it will do it faster with car off due to lower voltage, where if it is the sub there will be less difference in max clean output.

Just some things I do maybe one will help.

If you are getting some kind of cone noise or resonance, you can try stuffing the box sometimes it really helps. Check the tinsels on the sub to see if they can be slapping.

 

[Badmunky]

Im sure there is no power problem.
I just dropped in a new Optima Yellow top and I have 4 gauge run the back of the car and the about 2 feet of 8 gauge to the amp as that is what it needs.
The ground it good I checked it as well when I was trying to find the problem.
I did not check the voltage at the amp as I did not have the tool needed at the time but I will.
With the car on or off it seams to be the same.

If i still cant find the problem I will take the car to an audio shop to have them look at it.
I know the sub is not clipping. The sound I get is not metallic at all. And I had an amp that would clip on a sub a long time ago and this dosnt sound like that did.

It sounds just like port noise or a box leak.
But I have no port and Im 100% sure I have no leak in the box.

Later.

 

[sqshoestring]

Any $10 DMM should work fine to check voltage drop. What about the history of this sub is it new?

I can't tell you anymore not knowing what the sound is, I don't know what an air type noise would be from if the box is sealed and you had the seat out and it still did it so it is not a clearance-to-the-sub issue. I'm not sure if air would try to get into your trunk around your setup there, that might be possible with enough output.

 

[Xander]

You said it only makes it at certain frequencies...

Can you hook up a laptop and play a sweep (use sweepgen or something else free) and tell us at what frequency?

Now look at your EQ settings. Does it match where you boosted?

 

[Aaron'z 2.5RS/WRX]

As for setting the gain, I started by maxing the gain on the Sub out line on the CD player. Then I set the gain so that at the max I can run the CD player the sub was seeing about half what I thought it could take.
That had the gain at about 1/4.
After a few weeks and many hours of play time I retuned the amp and made some changes to the box as I said in post one as well as changes to the amps EQ setting. At this point the gain is at about 2/3s.

The CD players gain is now at about 3/4-7/8 so I can add more if the station I"m listening to needs it.


Thanks.

Ok, I'm seeing a glaring issue with your gain set-up... If i've read it correctly, you've kinda gone about it backwards...

First thing I note is MAXing anything is bad.. You said you maxed the Sub out in the HU, does it have a range, or a center point? like -15--------0--------+15 or something like that?

If so, set it to zero..

I give this as a gain set-up guide... it's just that though, a guide.. rear it and tell me if it makes sence to you, in the grand scheme of things, K..

First off, EQ flat, levels flat and gains at zero...

Find and download a 1khz tone and a 60hz tone (the 45hz mentioned above is a bit low, 60hz is the strongest of the "bass" tones and it's what is used for SPL drags, because of that) Stereo System Test & Analysis Tones by Nino B.

Play the 1khz tone on repete, turn up the HU until you hear a distinct change in the tone (you should have output even with gain at zero) back off, try again, back off.. make sure you hear a change.. The point that you back off to is your HU MAX now... (keep following, you'll understand in a minute)

Now, with the new HU MAX, play the same tone, move to the amp... bring up the gain until you hear a distinct change, back off... You now have the amp MAX (keep following)

Now, play the 60hz tone at the HU max... turn up the sub amp gain until you hear a distinct change.. back off, you are now at the sub amps MAX.. You can unplug the RCAs from the other amp, so they don't have to be playing for this if you like..

Now, this is just a guide, once you find these points, it's totally up to you to listen to some music you know well and make adjustments from there...

AFA the sub level in the HU, you should never MAX anything.. and by setting up this way, you have adjustability to go BOTH directions, not just down...

If I haven't followed you right, please let me know, i'll retract my statements..

 

[Brian Steele]

First as for the leak test I did that and if I hold the cone in fore 15sec and then leg go it pops right back out.

So Im sure there is no leak in the box.

If it pops right back out, then you DO have a leak in the box.

If it returns SLOWLY to the rest position, then you don't have any leaks to be concerned about.

 

[Badmunky]

Any $10 DMM should work fine to check voltage drop. What about the history of this sub is it new?

I can't tell you anymore not knowing what the sound is, I don't know what an air type noise would be from if the box is sealed and you had the seat out and it still did it so it is not a clearance-to-the-sub issue. I'm not sure if air would try to get into your trunk around your setup there, that might be possible with enough output.

I will check Voltage the next time Im home. I just didnt have the tool needed with me at the time. I do have a DMM though.

You said it only makes it at certain frequencies...

Can you hook up a laptop and play a sweep (use sweepgen or something else free) and tell us at what frequency?

Now look at your EQ settings. Does it match where you boosted?

I will try that for sure!
As soon as I get home next I will do this and get back to you guys.

Ok, I'm seeing a glaring issue with your gain set-up... If i've read it correctly, you've kinda gone about it backwards...

First thing I note is MAXing anything is bad.. You said you maxed the Sub out in the HU, does it have a range, or a center point? like -15--------0--------+15 or something like that?

If so, set it to zero..

I give this as a gain set-up guide... it's just that though, a guide.. rear it and tell me if it makes sence to you, in the grand scheme of things, K..

First off, EQ flat, levels flat and gains at zero...

Find and download a 1khz tone and a 60hz tone (the 45hz mentioned above is a bit low, 60hz is the strongest of the "bass" tones and it's what is used for SPL drags, because of that) Stereo System Test & Analysis Tones by Nino B.

Play the 1khz tone on repete, turn up the HU until you hear a distinct change in the tone (you should have output even with gain at zero) back off, try again, back off.. make sure you hear a change.. The point that you back off to is your HU MAX now... (keep following, you'll understand in a minute)

Now, with the new HU MAX, play the same tone, move to the amp... bring up the gain until you hear a distinct change, back off... You now have the amp MAX (keep following)

Now, play the 60hz tone at the HU max... turn up the sub amp gain until you hear a distinct change.. back off, you are now at the sub amps MAX.. You can unplug the RCAs from the other amp, so they don't have to be playing for this if you like..

Now, this is just a guide, once you find these points, it's totally up to you to listen to some music you know well and make adjustments from there...

AFA the sub level in the HU, you should never MAX anything.. and by setting up this way, you have adjustability to go BOTH directions, not just down...

If I haven't followed you right, please let me know, i'll retract my statements..

I will retune my amp and Head unit the way you said just to be sure. All thou I think my way should have had the same end resoult as yous. But hay you never know. I may have messed something up during my tuning.
So I will redo it.

If it pops right back out, then you DO have a leak in the box.

If it returns SLOWLY to the rest position, then you don't have any leaks to be concerned about.

I think you have the reversed. If it had a leak air would get out and so the cone would slowly return to its rest position. If it has no leak it should go right back when you let it go.

Later.

 

[sqshoestring]

Well, if it had no leak it would go in hard and pop right back out. If it had a tiny leak it would stay in after holding it for a time, and slowly come back out. If it had a huge leak it would go in easy and pop back out. Used to be huge leak and no leak you could tell by it going in easier with a huge leak because you are not compressing the air in the box, but subs today have stiff suspension so harder to tell but you can listen for air sounds. I never found a tiny leak to affect performance anyway, the sub moves way too fast for any amount of air to get in/out in time to change the box pressure and you can tell by how fast the sub can come back out with a tiny leak (unless you are playing subsonic sounds). What is worse is if the wood can vibrate at a gap and that will do much more harm to your sound.

Most subs I've checked they eventually will stay in some, like the surround leaks air even if the box is perfect....but you have to hold it for a while.

 

[Oliver]

Testing subwoofer box for leaks - Google Search

Mobile Electronics Australia > How do you tell if your sub box is ...
And yeh for pushing the cone in to test the sub. If the box is fully sealed, ... If the sub rebounds fast you have an air leak, if it rebounds slow your ...
Mobile Electronics Australia > How do you tell if your sub box is sealed? - 26k

some reading- ^^

Candle , cigatte...sub playing loudly, move cig around edges watch for smoke to change it's movement