[johnscales]

So I had a nice sounding Kicker 10" square sub mounted in my bmw convertible firing through the ski pass.
However, in order to have it playing with the roof down I would have to go to the boot and lay it down so it would be facing upwards which meant having to trim the base a little because of the smaller space it would be firing into causing car body vibrations and an earlier distortion point in the volume.
Anyway I take it to a shop who suggest that they will re house the sub in a box not so tall and deep so that it could fire through the ski pass with the roof up or down.
The job was done and all is not so well. Yes the roof goes down without me having to dick about with the sub but it now sounds different. It doesn't sound nearly as round and bassy at low levels and although it definitely fires out the sub frequencies it sounds more or less like a bass driver. It's good and loud still but I feel as though I need to buy a second sub in order to get those frequencies playing again which wasn't my intention in the first place.
Also, and this is worse, my amp now gets extremely hot (the casing is literally iron hot) when not even set beyond half max sensitivity and there is a definite electrical smell which now emenates around the car shortly after playing a tune at a high volume which comes from the amp. This was definitely not the case previously. I especially don't want this going on with passengers in the car as you can imagine.
Initially when I got the sub re installed the guys had the sensitivity on max but this caused the protection mode to come on three times on my journey home. It took a good couple of hours worth of tweaking to get the set up acceptable to most of my music collection.
As mentioned already I do like the now louder bass drive element but I do miss the continual sub frequencies which were there before but now only show up when out and out sub frequencies are played (particularly Drum 'n bass).

Without having the original box I don't know whether it was chambered internally. I do know that it was ported. I've got to go over this new box to see just how much dimentionally smaller it is.
Any audio savvy members with any thoughts/ideas on what I could be doing to improve the performance and also why my amp is now getting incredibly hot. It definitely seems to be linked with introduction of the new enclosure.

[MEGA]

Personally? And I can't be certain as I've not seen it - but I'd say that the box is too small which means the sub is having to work much harder, is drawing more power, increasing resistance.

You risk blowing the sub and/or amp like this.

the shop you took it to sounds like cowboys tbh, they should know the dimensions the kicker sub needs and not give you a box smaller than that.


I recommend you pick a different sub, but truth be told a sub in the boot of a vert will always lead to limited options as the height you have with the roof down is extremely limited.

Have you considered under seat 8" subs?

Dave

[rs32]

I would go with something free-air firing into the boot with the magnet pointing through the ski-hatch, and reverse the phase/polarity (+/-) on the sub wiring.

That way you don't need a box and you can enjoy the decent output of a proper 12" SQ sub that hits low and hard.

[johnscales]

Thanks Mega. I was pretty sure it had to be related, just didn't have an explanation as to why. Now I do so I can let them know and hopefully they won't charge me for a fix. Any idea whether a port of some sort might help, or would that again change the characteristics of the sub output negatively?
Rrs32. Sounds like a plan but tbh I don't really want to fork out on another sub if I don't have to. I spent £200 last July on this one and have been v happy with it barring the regularity of having to go in and out of the boot area

[MEGA]

A port would mean you need an even bigger enclosure fella, so would likely sound worse.

It "might" sound lower with a port but it's not otherwise likely to help matters ...

[johnscales]

Ok. I'll have a think about what options are left to me. Thing is there is still space for the box under the roof protector thing (sory don't know it's proper name). They just built it slimmer than it needed to be I think. Maybe I can get them to rebuild or if needs be rehouse again. Would have been good if theyd checked the size required in the first place as you've mentioned.
Will give them a call.

[Sparky68]

In my e46 330 vert I had 2 8" s in a custom box that was small enough to remain in place the whole time. You will always struggle unless you make other sacrifices.

[johnscales]

How good are 8's really? I've never invested in them before.
Have had 15's, 12's and my current 10 and i've been through my fair share of setups with each. Never tried 8's though. Always thought they looked weedy and would sound punchy when I would want roundness (If that makes sense). Somebody tell me i'm wrong...

[Sparky68]

Get the box designed right and they are very good.

[johnscales]

Cheers Sparky68.
One last q guys.
It's about free air subs. Clearly I risk damaging either or both sub and amp in the current set up so I will defo have to remove the sub from it's enclosure.
Am I at risk of causing damage to either amp or sub if I have it playing as a free air sub (Infinite baffle)?

[MEGA]

If the sub is not designed to be IB then it will sound shite fella... Like a flappy wet fart.

Check the specs of the sub

[johnscales]

Sorry if i'm re hashing this thread.
I've been busy and haven't had a chance to do much at all around resolving this problem.
Reason i'm bringing it back up again is that i've measured the dimentions of the new box (allowing/assuming for 3/4 thick mdf) and compared it to the subs recommendations and the box is or should be plenty big enough.
Documentation states sealed enclosure should be .8 - 3 cu ft in size.
Measurments of the box came back as 1.07 cu ft so I shouldn't be having this amp cut out problem.
The only thing else I can throw out there is that my amp is 75 watts rms and the sub is 400watts rms. Previous box was ported, this one is sealed.
I've read that subs work harder in sealed enclosures and if that's correct then i'm wondering if it's therefore working the amp harder ad making it go into protect mode. Happened to me three times last night with my HU bass on 4 (out of 20)!?!
Anyways. New amp going in today so i'll see what happens.
I'll post up what I find.

[johnscales]

Box was ported and thus too small (1.25 cu ft minimum). Will plug the port an all should be well... I hope.

[rs32]

it's possible with such a low power sub amplifier that the sub could have been asking too much of the amp in its old enclosure and you've just got unlucky at the time you made the switch to sealed.

You need to understand more about the specifications of the sub (T/S parameters) and match your amplifier and the enclosure to the specs of the driver.

Can you provide the model numbers of your amp and sub please

[johnscales]

The new enclosure is ported. Sorry, I didn't explain that very well in my last post. I thought it wasn't ported but after removing it from it's tightly wedged position I found the port.
Sub is a kicker solobaric l3 dual voice coil (200w rms per coil).
Amp phoenix gold qx 150.4 (New amp is Jl Audio Jx 360/2 (360w rms bridged)
The manfacturer specs say that ported enclosures need to be 1.25 - 1.75 cu ft in size while a sealed enclosure should be .8 -3.0 cu ft.
I measure the internal dimentions of the enclosure to be 1.07 cu ft in size and therfore it is too small to cope with the sub whilst ported.
If I plug the port then the enclosure should be plenty big enough to cope. This will be my next move.

[rs32]

ok - so here's a possible explanation (or at least a way of getting it 100% right with your new amp)

your sub is a dual voice coil @ 2 Ohms each

When you wire this up in series, it will present a 4 Ohm load to the amplifier. I'm guessing this is how you had it before you took it to the shop for the new box.

When you wire this up in parallel, it will present a 1 Ohm load to the amplifier - forcing the amp to deliver every last little bit of power to the speaker. If the amp is not stable at 1 Ohm (and the PG QX 150.4 is only stable down to 2 Ohms), it will start to fry itself - then you get frustrated and turn it up, then the problem gets worse.

I'm suspecting the audio shop didn't understand how to wire up a DVC sub properly, or they've done something wierd with your amplifier connections.

Neither of the amps you mention can deliver power at a rated 1 Ohm level so you can only use your sub @ 4 Ohms unless you buy a 1 Ohm stable amplifier.

To get the most out of you JX 360.2, you need to bridge it to 4 Ohms for Mono operation (read the manual) and wire up to your sub as per option 2 on this page

Then you need to set your gain levels on the 360.2 as per JL's instructions with no bass boost or EQ on etc. If your box and sub/amp combo are correct then you should be able to deliver the full range of bass that the sub can deliver without any boost - this is the biggest mistake people make with subs, they think that more EQ boost is better when in fact 99% of the time it makes it sound completely shit (and overworks the amplifier). Get the box right and the amp gains right and you'll have genuine beefy musical bass.


Hope that helps

[johnscales]

Good stuff rs32. I'm going to pull the sub and check how the two coils have been wired. It's an interesting one because I wasn't aware that the sub was a dvc 400w rms until I read up about it due to this very problem which I'm having. I distinctly remember the original shop which i'd bought it from telling me that it was 200w rms a year ago which leads me to believe that they'd only wired one of the coils. Also remember them telling me at the time that my amp (phoenix) would be under powered for the sub's capabilities which would lead me to believe that they may well have only wired one of the coils. I've since read 2 schools of thought on this. One being that the sub won't work if only one coil is wired and the other being that it will. In any case IF it does work with one coil and also IF the original shop did only wire one coil then i'm soon to be in for a serious increase in bass drive.

Update.
I blocked the port and the new sub didn't cut out at all after 20mins of plaing a mixture of bass heavy tunes. I let it cool right down and pulled the plug from the port. The amp cooked and went into protection mode after about five mins. That confirms the sub is defo too small ported but perfect enclosed.
Will reblock and bridge Looking forward to this.
I'll set up as per the instructions regarding sens/gain later when I have time and hopefully will not need to use any boost as you say.
Sounds great too btw even if I had to take extreme measures to test