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[razzo]

If you had to improve on a sound system in an Omega what would you do with a budget of £250 & with a budget of £500. The base system is non Bose. Would you always go for a ported sub as opposed to sealed

[razzo]

And what if you could have any system you wanted

[Admin]

Well until Mark comes along, I will give my (less knowledgeable) opinion.

£250 is difficult, but just about workable.

Start with a good headunit, ideally Pioneer or Alpine. 3 pre outs is very useful (control crossovers from headunit, much to Marks disgust!  ) Buy 2nd hand as you will get much better value for money. £100-£130.

Next you want a good 4 channel amp, at a very good price. Older V12 Alpine if you are lucky or Kenwood, Pioneer, Phoenix Gold QX series.
You don't need huge power, 35w rms x 4 is plenty. £30-£40

Sub and amp...
I personally prefer sealed subs, but Mark will say "you haven't heard a proper ported sub!"
(apart from the ones in his house that he designed and built)
Sealed is more compact (a lot more!), but requires considerably more power to achieve the same result.
I would say a 10" sub in a box can be had for £40 if you are patient.
I got a nice JL Audio 12" sub in a custom built ported box with a Phoenix Gold amp for £46. Just a question of patience.

Finally you need a wiring kit, most notably a LONG fused power lead and a splitter.
Most are 5m and that really is not enough. 6 or 7m gives a lot more freedom on placement.

I think I know his answer on "any system you wanted" in a car....

[razzo]

So i am assuming you would keep the standard door speakers & maybee cross out the lower frequencies ?

[Marks DTM Calib]

As per above although Laidback66 is totally wrong in the 'sealed is smaller'.....the construction has nothing to do with size....its down to the driver selection....

In answer to your question....yes, 30-35WRMS to the four door speaker setups ideally with the bass filtered to remove the sub 130Hz component.

Then use the boot fitted sub to fill in the bass.......

The reasons being

1) You don't want lots of low frequency sound in a door cavity.....no matter what you do to it will rattle and boom...

2) Bass has very little directional effect and hence its easy to add it back in from a different point in the car..

It will take a little tweaking on the cross over responses but, the results are very good and for little layout....

This can all be done for around 250 if you spend wisely....

Once you go beyond 250 its a case of diminishing returns......unless you want to buy new components in which case your starting budget would need to be 400-500!

For money no object.......I would fit a good sound system in my house.....where I can get true Hifi!

[Kevin Wood]

Fit pre-outs to CCR2006 (standard stereo). £free
Buy Alpine MRV-F407 amp on ebay for £26 (ok. it was a duff one so add £4 for a pair of MOSFETS to fix that)
A few quid on wire and fuses, etc. (an auto electrical specialist will be MUCH cheaper than a car audio place for this)
A few hours with head under dashboard.

Alpine amp powers the front two standard speakers and ...er... an old Wharfedale chucked in the boot as a sub! Must sort something better out there!

It sounds as good as any car system I have heard, though, and I don't see the need to spend any more. If someone nicked the whole lot tomorrow I wouldn't have lost a great deal - not that they would because, with the bog standard stereo in the dash, they wouldn't look any further. And they don't know my alarm doesn't work.

Kevin

[Paul M]

As per above although Laidback66 is totally wrong in the 'sealed is smaller'.....the construction has nothing to do with size....its down to the driver selection....

In answer to your question....yes, 30-35WRMS to the four door speaker setups ideally with the bass filtered to remove the sub 130Hz component.

Why 130Hz, is this as low as the door speakers can handle without rattling or just generally crapping out? The reason I ask is that I always try and get the front speakers to drop as low as possible (well close to 80Hz anyway) so I can keep the crossover on the sub low. At 80Hz it's very slightly noticable that it's coming from the boot, but not enough to detract from the sound stage much. At 90Hz it becomes more noticable. 100Hz or higher I find it's very obvious that the bass is coming from the boot and the mids/highs from the front and it all sounds very disconnected.

One of the things I really like about the setup in my BMW is that the front is a 3-way setup with the low frequency drivers in the kick panels built into a little ported enclosure filled with acoustic wadding. It doesn't drop low enough to negate the need for a sub (probably beacuse the enclosure is too small) but it means they can play cleanly down to about 70 Hz or so with the sub making up the rest. With the crossover points that low the bass really does sound like it's all coming from the front, you would think there's no sub at all just really good mids up front. Turn off the sub output from the head unit and you notice the lack of low-end to the music, turn it back on and it just blends in nicely. They actually do reasonably well with no sub and the crossover removed, but they sound a bit muddy with lower frequencies and really start to struggle as the volume increases.

[Marks DTM Calib]

Its totaly dependent on the application and the roll off of the filter used....most car audio filters seem to have poor roll off and hence the speakers are still pretty active at slightly lower frequenceies...this reduces the noticeable cut over....

You have to play with each setup to get it just right because the kit is all very different...

[Paul M]

Its totaly dependent on the application and the roll off of the filter used....most car audio filters seem to have poor roll off and hence the speakers are still pretty active at slightly lower frequenceies...this reduces the noticeable cut over....

You have to play with each setup to get it just right because the kit is all very different...

The crossovers I'm using are 2nd order actives built into the amp (12db/oct) not particularly sharp but better than many of the single capacitor passives that many people use. The whole system is amped too, it comes from the factory running an 8-channel amp bi-amped for both front and rear, low-freq driver running off a dedicated channel and with a passive crossover between the mids and highs. Does the job OK but as with almost all factory systems it's not brilliant, particularly considering the £2k or so some numpty paid for the "HiFi" upgrade :O

[snappa]

Could you not run the front speakers direct from the player if it has a built in amp & using a capacitor, cross out the low frequencies that way. Just an idea

[Marks DTM Calib]

Cap filtering is somewhat harder to do....

...more so when you have a bridged output stage.....and given that speakers are a complex model formed from various R, L's and C's.....


Plus head unit amps are very restrictive in power output....mainly due to the lack of a high voltage supply to run the ouput stages off......

Assuming that the fronts are 4 ohm (Bose ones are 2ohm...)......!

The trouble is that if you consider that you have a 12V supply available and assuming your headunit output uses a bridge setup, you can in theory get close to a 12V swing....

So with a 4 ohm speaker ......and using W=V²/R, you get 36W peek......some quote 40W but that assumes a higher supply voltage (12.6V)...

Now, thats peek.....RMS (which is the true power figure)  is 25Wish.....

In the real world, given some V drop in the power amp output stage and the supply system....you will be lucky to get much more than a 11V output swing....which is 21W RMS....it gets worse when you then consider cable resistance etc.....

Power amps employ an in-built DC-DC converter to boost the 12V supply to +/- 18-20V (some even higher).......but, this function is not small and often takes up 50% of the circuitry and space in a power amp....hence it does not fit in a headunit...

[Kevin Wood]

I agree. Avoiding at all costs the use of head unit amps is the first step towards achieving passable sound quality.

In addition to what MarkDTM says, there is also very little space for amps in a head unit, meaning you'll end up with 2 channels (4 amps bridged) in a single nasty integrated circuit. There is no room for much filtering of the 12 volt supply, and the desperate need to preserve every last volt discourages this anyway, so your amp is directly in parallel with your injection system, ignition system, wiper motor, etc.. Even if you listen to them well within their power ratings they sound horrible, IMO.

By contrast, my alpine has +/- 30v supply rails, reasonable filtering of the power input and the amplifier channels all use discrete components. It's constructed as nicely as a mid-range Hi-Fi separate amp, I'd say.

BTW are you sure it's as much as 21W RMS? 11v Peak is about 7.8 v RMS, V2/R =  15 watts. Either way, quality is the biggest problem, not quantity.

Kevin