Hey All,
I've had my car stereo for 2 and a half years I tuned the amp when I got it but it was a fairly ad hoc and I didn't really know what I was doing and thats how its stayed for the last two years!

The system consists of
JVC MP3 Head Unit - GD505 or something
Coustic 320QE 4ch Amp
Hertz ESK165 Splits
Cadence 12" Sub in a home made sealed box (can't remember the model can find the manual if its relevant)
Misc Sony splits amped off the head unit for rear fill.

Splits are off two channels on the amp and then the sub takes the other two in bridged mode.

The amplifier has adjustments for
- High, Low or Off Filter pass.
- Frequency Selection for the Filter Pass.
- Input Sensitivity
- Bass Boost

The adjustments can be made for the front and rear.

The HU also offers adjustments of bass, treble and a "loud" mode, it doesn't offer any sort of frequency specific adjustment.

Basically I followed the instructions of the amps manual which just said crank the volume to 2/3s max and adjust the sensitivity until it distorts then wind it back a bit. Did this with the splits, did it with the sub but to my ears it didn't distort the whole way up so the sensitivity is at max.

Splits are set to a high pass filter and the sub to a low pass filter, with the frequency at around 80Hz for both, I'm not sure how this works? If I set it to 80Hz on the low i think it blocks anything above 80Hz and on the high pass it blocks everything below 80hz?

Turned the bass boost up a little on both but it didn't do a heap.

Basically my issue resides in the bass response. At 2/3s volume its fine no issues but at 2/3s volume its like standing in front of a speaker at an AC/DC concert. the head units volume goes from 0-50 and i usually listen at between 15-20. I'm not a big chaple st doof doofer and far and above prefer SQ over SQL. I want crisp punchy bass at low volume but when i turn the volume back down from 2/3s the bass is all but gone the sub isn't doing any work at all. If i turn LOUD on the HU it does but the bass is muddy and who likes the loud feature anyway.

So basically after that extremely long winded post can anyone help me in how i should be tuning my amp to provide high quality crisp bass at low volume.

Here is a link to my amps manual in PDF form if it helps, the stuff about tuning that I followed is on page 12/13 of the manual. http://www.coustic.com/classic/PDFs/Coustic320.480.QEManual.pdf

Lower the gain on your speakers, so you can go louder on the headunit but still have heaps of bass.

Did the sound change suddenly or has it always been the same? An incorrectly built sub box will cause major problems with bass. If its too small there won't be good bass. Audiophiles would also go into the type of wood to use and the thickness. Is the inside of the bass box padded? Bass can become muddy due to interference of the sound waves if the inside of the box is bare wood. Basically the sound reflects off the surface and bounces back whereas with it padded the padding absorbs it, which is actually better. What phase have you got the subwoofer set to? This again has got to do with interference. Even though you have got the high/low pass filters the sound can still 'cancel' out in your sitting position. A very complex version of this is how virtual surround works, but you won't get that without a processor to do it! If you want to see how much of a difference it makes, with your home stereo, in stereo mode, swap the cables from negative to positive on one of your speakers (one only). This doesn't do any damage don't worry! this will only be truly noticeable with separate component systems where the wires come off the amplifier and not the woofer, as its bass thats most clearly affected. Now put on some bassy music and stand back from the middle. There'll be hardly any bass at all. Move towards either speaker and you'll start to hear nice deep bass! The purpose of doing that is to show how much correctly making a speaker box affects it (as the same thing is happening inside the box, the reflections act as the second speaker, and will be out of phase), and how much the actual phase setting of the subwoofer affects it to. The inside capacity of the speaker box does have an ideal size for the given speaker which should also be taken into account.


Could always put the high pass filter down and the low pass filter up... Yes, in theory setting them both to 80 is ideal, but if your front speakers can handle it reducing it to 63? or whatever JVC allows may make the SQ better, especially at low volumes. Its got to do with acoustics and dynamics etc. and I know a lot of people will disagree, but the best way to see is to try it and go by personal preference.

A lot of loudness controls work around 100hz, which is why turning it on gives a muddy bass sound. A good bass sound is like 30hz (20hz :D but by the time your in your 20's not only do you lose high end hearing, but lower hearing as well). On that note, why do people get super tweeters that have a response up to like 28,000hz, the normal human range is approx 20-20,000 but by the time you're in your late 20's, its more like 25-18,000 (or less).

Anyway hope this helps. Hopefully if you do need to mod your subwoofer box it won't take much effort. You can't just make a box and whack the speaker in!

Yeah I think a ported box would have been better for my style of music, alt, folk, world, rock etc at low volumes but heinsight is a wonderfull thing!

I built a sealed box because it was easier to do as a DIY job, I built it using the manufactures specs for volume and a CAA calculator i think from memory the box is pretty smick for a home job and I'm sure its spot on volume wise, and yeah its padded with fluffy stuff some sort of acrylic crap that you'd put in cushions or something (it was 2.5yrs ago so details are sketchy :P)

I don't really want to build another box if i dont' have to. I'm sure my tuning is out so i want to made sure that is alright before I go and spend money and time on a new box...

IF you have the Orange cone Cadence I wouldn't expect to much out of it. Have tested one of those in its factory ported box and in a sealed box off 450WRMS and 600WRMS and it doesn't get overly exciting.

Saying that the ported box worked well giving a noticable gain. If you can turn you gain up all the way there must be something wrong. Do you have EQ control?

yeah it was a bit of an inpulse buy. I couldn't get the sub I wanted and was buying my HU From JB and was just recomended it :S.

What do you mean could be wrong by me been able to turn the gain up too high? Its not clipping, at high volume so i'm thinking the amp is giving it enough power? or am I wrong what else could be wrong?

What I think could be happening is that the Cadence has a 300WRMS coil and your amp only puts out 150-200WRMS in bridged mode. The bigger 304q puts out 260WRMS when bridged.

Have a look on you headunit to make sure all bass settings are on 0 and not -6 etc. Turn everything to 0 then start again. I would try the woofer first by itself. Its hard to hear distortion from a woofer. For the amp to give the sub everything its got, the gain should be set near the gain that you got for the front splits which is probably just past half way to almost 3/4 full gain.

stuff.

yeah i think you might be right. HU was EQ was flat, didn't have the splits pluged in and yeah no distortion. The splits start to distort at about halfway so i think it might be my amp not giving enough juice. Bah I can't afford a monoblock or what ever why tell me this!!!! :bowrofl:

Sorry I just know that I needed a lot of juice to get that woofer going.:D