Sub Enclosure problem on a PG RSDc 10" Sub

finkle636 · Post by **finkle636** » Sun Oct 12, 2008 12:35 pm

I've now built THREE seperate boxes for this damn sub and i know im doing something wrong and have no idea what.

The first attempt was running the sub 'free air' on a board in between the back seats in the ski hatch, it worked but sounded....wrong.

The 2nd attempt was more regular, 100% sealed box 11"H, 11"W, 8"D. Sounded fine, no problems.

So i figured all i had to do was make yet another box with the same volume that would fit in the limited space i have in the trunk of my convertible.

3rd attempt (using same volume as 2nd attempt) Was 10.1"H,14.9"W and 6.5D"

The 3rd attempt, although it fits in the car, sounds ...... crap, it sounds like its putting out midbass and wont play low or hit hard, it basically sounds cheap and i have no idea why as i've been reading posts all over the internet and they say box shape is irrelivent as long as its sealed and has the same volume.

The only thing i can think of is that between the magnet on the sub and the rear wall of the box as its only 6.5" deep there is only like 3mm of gap. would this make a difference?

Capital_M · Post by **Capital_M** » Sun Oct 12, 2008 2:01 pm

You should have a couple inches at least between there. Check the wiring, switch the positive and negative

finkle636 · Post by **finkle636** » Sun Oct 12, 2008 2:50 pm

Wiring is ok, why does there need to be a 2-3 inch space between the rear of the magnet and the rear panel?

Is this my problem do you think?

If so, i may have to invert the sub so it goes into the ski hatch hole as i cant really increase the depth.

Any thoughts on this idea ?

thedeal7235 · Post by **thedeal7235** » Sun Oct 12, 2008 5:59 pm

what kind of amp, and are ur settings, on the amp, switched to lowpass? and what hertz is it crossed over at?

finkle636 · Post by **finkle636** » Sun Oct 12, 2008 6:13 pm

thedeal7235 wrote:what kind of amp, and are ur settings, on the amp, switched to lowpass? and what hertz is it crossed over at?

PG RSD600.1, the amp is fine because i can put the sub back in the 2nd enclosure and it plays fine, but not with the 3rd box.

thedeal7235 · Post by **thedeal7235** » Sun Oct 12, 2008 6:38 pm

what is the thickness of the mdf board ur using for enclosure?
ie- .50 "thick means ur box, based upon ur measurements would be .41 , which by the pg specs is enuff; but i use .80(2 seperate chambers on my rsdc 10s, and they hit hard, and accurate, i think, but i use a rsd 1200.1-also,

finkle636 · Post by **finkle636** » Sun Oct 12, 2008 6:45 pm

0.75" MDF

thedeal7235 · Post by **thedeal7235** » Sun Oct 12, 2008 8:45 pm

i know the pg specs show them to sound good in a small enclosure, but i would consider going bigger, jmho

bretti_kivi · Post by **bretti_kivi** » Sun Oct 12, 2008 11:01 pm

the reason for the clearance at the rear of the magnet is air. You're shifting air around and if there's only 3mm of clearance, that's all being used and there's no volume for it to push. At least one inch, preferably two, between base of magnet or port and the edge of the box is the rule IIRC.

I'll also agree on checking the phase, swap + and - and see what happens.

using it "arse out" will probably create more noise. Could you do something creative with Fibreglass to give it more space?

Bret

Post by **stipud** » Mon Oct 13, 2008 5:44 am

I think you should try mounting it inverted. I have never noticed any more noise unless I am sitting right next to the driver. Since it's firing through my trunk and seats, that noise is long gone before it gets to me.

The pole vent on the woofer needs to be able to expel the air within the voicecoil, and allow air to come in when it rises. Impeding this by having your subwoofer mounted nearly touching a piece of wood will stop this flow of air, causing vacuum damping to happen inside your voicecoil. This probably describes the weird sound, since it will have much more difficulty reaching excursion this way.

finkle636 · Post by **finkle636** » Mon Oct 13, 2008 2:55 pm

I swapped the phase round and theres alot more bass, i dont understand it, but hey it works.

My next problem is this

I moved it from the middle of the trunk to behind the rear seats (with the ski flap still removed) and the sound changed, it wouldnt play low all i was hearing was midbass.

So i moved it right to the rear of the trunk, this time i got the other extreme, it played very low but bits of the sound were.... missing.

I put it back in the middle and all was well again.

WTF is going on ?, i have tried it facing forward, backward, on its back. everything.

Oh and in my boot there is a lever that if you push it you get more trunkspace when the roof is up.

If the sub is in the middle (the only place it seems to sound right) of the trunk and i dont have the extra trunk space by pressing this lever, the bass nearly disappears ?!??"!!?!?!?

Post by **Bfowler** » Mon Oct 13, 2008 2:59 pm

what frequency is the amp crossed over at?

i think we need some pictures to help diagnose this

finkle636 · Post by **finkle636** » Mon Oct 13, 2008 3:39 pm

Pics of the trunk

Post by **Rold Gold** » Mon Oct 13, 2008 4:09 pm

You get better sound if ya turn the sub around and face it back.IMO that is...

thedeal7235 · Post by **thedeal7235** » Mon Oct 13, 2008 4:45 pm

im trying to help, not be rude, is the amp going into protect, or feel like its getting really hot? i ask, b/c one time i put my diamond subs back in., and i assumed i knew the correct voicecoils, what im getting at, is I WIRED THEM WRONG< and felt sooooo stupid once i figured it out, not sayingthis about you, but i did this , and ive wired subs up , probably 50 different times

thedeal7235 · Post by **thedeal7235** » Mon Oct 13, 2008 4:46 pm

also, is the one sub, a dual 4ohm sub, or dual 2ohm sub? that , with the wiring, will determine the ohm load that amp will see

thedeal7235 · Post by **thedeal7235** » Mon Oct 13, 2008 4:50 pm

9200 North Decatur Street Portland, OR 97203 tel: 503.286.9300 fax: 503.978.3380 www.phoenixgold.com
© 2007 Rodin Audio
SUBWOOFER WIRING GUIDE - 1 SUBWOOFER w/ DUAL VOICE COIL (2 & 4 ohm)
Option One: Series Wiring
(These diagrams represent One Dual Voice Coil Speaker)
Series wiring is connecting components to a source so that they share the same
current. Connect the amplifier’s positive terminal to the positive terminal of the first
speaker and then connecting the negative terminal of the first speaker to the positive
terminal of the second speaker and so on. The final speaker in the chain will have it’s
negative terminal connected to the negative terminal of the amplifier.
Final Load
(1) 2 Ohm DVC Subwoofer: 4 ohm**
(1) 4 Ohm DVC Subwoofer: 8 ohm
*Phoenix Gold Mono Block amps make full power at 2 ohm
**Phoenix Gold 2/4 channel amps make full power at 4 ohm
9200 North Decatur Street Portland, OR 97203 tel: 503.286.9300 fax: 503.978.3380 www.phoenixgold.com
© 2007 Rodin Audio
SUBWOOFER WIRING GUIDE - 1 SUBWOOFER w/ DUAL VOICE COIL (2 & 4 ohm)
Option TWO: Parallel Wiring
(These diagrams represent One Dual Voice Coil Speaker)
Parallel wiring is connecting components to a source so that they share the same
voltage. Connect all of the speaker positive terminals to the positive terminal of the
amplifier and connecting all of the speaker negative terminals to the negative terminal
of the amplifier.
Final Load
DVC Subwoofer: 1 ohm
(1) 4 Ohm DVC Subwoofer: 2 ohm*
*Phoenix Gold Mono Block amps make full power at 2 ohm
**Phoenix Gold 2/4 channel amps make full power at 4 ohm

finkle636 · Post by **finkle636** » Mon Oct 13, 2008 5:04 pm

Its a 4ohm DVC, wired to put out a 2ohm load, the amp runs fine, my problem is the box and or the positioning of the box.

If i leave it as pictured in the centre of the trunk with the extra trunk space lever engaged (as pictured). the bass is 100% fine.

If i move the sub closer to the front of the car, i loose the lows

If i move it to the rear of the car all i get is lows and the sound lacks depth.

If i lower the trunk extension (making the trunk smaller, this is where the roof goes when the tops down) i loose 80% of the bass.

Does this make sense.

Adjusting the amp doesnt make a difference.

I orginally wanted it in the ski hatch between the rear seats but all i was getting was midbass as it was running 'free air'.

So i abandonned that idea as i dont have the ability to make a sealed box for that area.

As you all can see from the pics i'm limited in the trunk for height when the trunk expander is down. hence my need for a wide/ low / shallow box.

Any other suggestions for a new box would be more than welcome as i am out of talent at this point !!

Post by **VW337** » Mon Oct 13, 2008 5:09 pm

Wow, all these excellent minds here and nobody has mentioned standing waves........

That box you have your sub mounted in, looks to have all right angles. Do you have anything inside the enclosure to dampen or breakup any standing waves? Poly-fil, egg-crate foam?

Part of the issue you may be experiencing is when you have an enclosure that is all right angles you have sound waves that are being reflected the exact direction they came from. Think back to science class with the pool ball idea, two pool balls rolling at one another at the same speed and exact opposite direction....upon collision both balls stop. Same idea in the audio world.

Now box placement will produce a similar concept but has to do with cabin reflections and where your ears are placed. If you need the enclosure placed in a specific area for maximum storage within your trunk, try turning the enclosure different directions until you get the best response, also try putting risers of some form under different sides to play with the face angle of the sub as well. Make note of the best location and secure the enclosure there with brackets or additional panels or something but secure it.

finkle636 · Post by **finkle636** » Mon Oct 13, 2008 5:10 pm

This is how i have the sub wired

Post by **Rold Gold** » Mon Oct 13, 2008 5:14 pm

Did you try turning the box and facing it out the back?????

Put it to 1 side firing back and see how that sounds. Firing it forward through the hole, you'll need to "seal" it off from the trunk. Why do you think you see woofers firing backward in alot of cars????? SPLer's build walls and fire forward for a reason too. But look how they do it. A wall from side to side and top to bottom. Right.....???? Just turn it around and see how it sounds..........

I thought everybody put polyfil in the box.......that's 101

......

finkle636 · Post by **finkle636** » Mon Oct 13, 2008 5:15 pm

Nothing inside the enclosure at the mo as im still in 'test' mode, i want to get it right and shaped to fit the trunk before i dynamat and carpet the finished item.

I am 100% happy with the sound as the box sits there slap bang in the middle of the trunk but i cant leave it like that.

I have never had a problem like this where you move the sub around in the trunk or lift the trunk expander and you loose/change the sound this severely.

thedeal7235 · Post by **thedeal7235** » Mon Oct 13, 2008 5:16 pm

yep, that looks right for a single dual 4ohm .then amp sees it at 2ohm, but id take vw337s advice, i think he does, or did used to work for pg, if memory serves me correct???? all, id like to add is that when u look at the frequency select on the rsd, i think that 80hz is at 10'oclock posistion for xover adjustment, at least thats where my 2 rsdcs seem to sound best, , almost bline up before u see the f, for frequency, thats right about 10'oclock on the rsd line

finkle636 · Post by **finkle636** » Mon Oct 13, 2008 5:16 pm

I shall turn it round, no worries.

finkle636 · Post by **finkle636** » Mon Oct 13, 2008 5:26 pm

Because i only have 3mm of clearance between the end of the magnet and the rear panel inside the box, could the sub box's placement be making up for this accoustically ?

And when i move it what im hearing is the REAL sound of the box?