Octavia II Poor Sounding Stereo Fix

[Mr Kite]

RDX Hi Again,

Very interesting. The tweeter covers remove by prising them out with a credit card. Having done this, I looked and looked of a way to remove the door handle/tweeter assembly but it always seemed like it would break(there is a torx screw to remove). You can loosen it at the tweeter end but cannot reach the plastic clips holding it in at the handle end. Well I couldnt anyway!

Have a go and let me know.

By the way if I was fitting it all again I would paint the tweeter mounts black and they would "disappear" to a degree.

Mr Kite

[bahnstormer vrs]

Interesting thread this.

Whilst the suggested fix to poor sound from the Audience (& Stream) is to fit new speakers and crossovers etc. and here I will bow to Mr Kite's expertise, IMHO you can't make a silk purse out of a sows ear! That is to say; the output, to the discerning ear, from the OE Audience and Stream units is poor in the first place.

I had this problem on my Fabia, and subsequently with my current Octavia, I therefore visited my local ICE shop who do a lot of high end custom ICE fittings. I told them my sound was poor and asked about better speakers.

Their immediate response was to forget about upgrading speakers and get a decent head unit first!

Taking their advice; I bought a mid range Alpine unit and found a huge improvement (in the Fabia). Subsequently, transferring the Alpine to my Octavia, again, a huge improvement particularly with MW radio reception (but that's another story and thread) and I have no grumble with the present sound using OE speakers.

One final point; IMHO its a lot easier to fit a new Head unit than it is to start pulling doors and speakers apart.

[Genoa1893]

The tweeters are certainly 'noticeable' like that. Im more of a stealth install man myself but if you are happy thats all that matters

Me too on the stealth side ,

so I decided to give a look to the tweeters.

Between each tweeter and our ears there is a lot of diffraction sources: the door handle, the tweeter external grill, and tweeter internal plastic grill.

I decided to cut this latter away and applied a spruce-based lacquer to the tweeter. The result is a smoother and cleaner sound (for free).

Next time I would reconsider tweeter mounting to the card via some blue tack to decouple it from the shaking door panel and add more mass to the tweeter magnet to reduce vibration frequencies (again, no costs involved).

HTH,

[RDX]

Bahnstormer, yes I agree, the head unit is always what the ICE men will recommend you change first and I am considering it. However at the moment I want to retain the OEM look and functions.

I saw the post from Mr Kite and thought that could be a quick fix for a start. But only if it can be done without taking off the door card.

Very interesting Genoa1893. Do you have some experience with lacquering tweeters? Where can you get the correct stuff?

This is interesting, keep it up!

Cheers,

RDX

[Mr Kite]

Gentlemen,

The only true way to "prove" if the head unit or speakers are to blame for the poor sound would be thus:

Disconnect the door speakers and connect a pair of small Hi Fi speakers of known good performance to the head unit. Alternatively connect the door speakers to the output of a suitable Hi Fi source.

I would put money on which would sound the best.

The output from the Audience unit is quite clean. The colouration in the sound that we all dislike so much is a characteristic speaker fault. If I had designed a system that sounded this way in my Castle Acoustics days I would have been shot!

However thats not to say that changing out the Audience unit would not bring about further improvement - Im quite sure it would but great gains can be made by just a proper tweeter and crossover, much cheaper and easier.

Mr Kite

[Genoa1893]

Do you have some experience with lacquering tweeters? Where can you get the correct stuff?

Yes, I had very positive results (at least to my and my wife's ears) in DIY lacquering devices of my hi-fi system (like headshell, tonearm, DAC, cables). I just used spruce resin and turpentine. Give a look at:

Mother of Tone - The Effect of Lacquer

HTH

[Genoa1893]

Hi Mr Kite,

did you get any measure of the parameters of the OEM tweeter?

BTW, I looked at the infinity xover. Well it seems a bit complex and those yellow cans reminds to me bipolar electrolytics... why don't consider changing them with poly one?

[Mr Kite]

Genoa1893 Hi,

My original tweeters are still in place so I didnt get a chance to measure them.

The capacitors on the crossover are non polorised electrolytic type which are fine for most applications. As you suggest Poly prop ones could be a useful upgrade at some point but the standard ones do sound fine.

A point about laquering or doping tweeters. The technical result of this is that it adds mass to the dome so lowers the resonance of the unit.

This is a good thing as the resonant point (usually about 1500Hz) is what makes the tweeter tizz and spit on "S" type sounds, so lowering this frequency is likely make this problem less audible.

However it requires a deal of precison to apply it correctly. Just blathering it on willy nilly is likely to mess things up somewhat.

I cannot possibly comment on what effect it may have on other Hi Fi items!

Mr Kite

[Genoa1893]

Just blathering it on willy nilly is likely to mess things up somewhat.

Well it really took a few of minutes to use a small soft paintbrush to apply the lacquer onto the tweeters, and a smoother sound is already here!

Anyway, being a DIY addict, it seems it's time for me to open the door card again and give a look at original xover. To do a proper work one should know the parameters of both woofer and tweeters, anyway a good step up might be a better quality cap or a more refined xover. Then I plan to physically decouple the tweeter from the "baffle" and add some more mass on the magnet.

At the cost of open the door panels to access woofers, adding some blue/grey tack to the spiders would improve sound, too.

BTW, have you got any idea of the value of the original tweeter xover cap?

[Mr Kite]

Genoa1893 Hi,

Its good that you got a result with your laquer.

Im afraid I dont know the value of the tweeter cap but it is the only component in the "crossover".

Im not sure where you can get the drive unit specs from so I used the infinity crossover (HF section) and modified it to best effect. It is now a 3rd order T network which controls the tweeter well. It allows connection either way round as the phase error is the same in each case. This can be tried for best integration.

The bit of extra damping you suggest is a good idea but take it easy with the laquer!!!

Let me know how you get on with your mods.

Mr Kite

[RDX]

Hi again,

I've been looking at some Infinity tweeters which might fit, but they are only 2 Ohms impedance. Is that going to cause a problem?

Thanks for any info.

Cheers,

RDX

[RDX]

Anyone?

Mr Kite, any comment, please?

Thanks,

RDX

[Mr Kite]

RDX Hi,

The lower the impedance of a drive unit, the more severe the load is on the amplifier. A 2 ohm tweeter on an amp deigned for 4 ohms means double the curent flow for the set voltage (volume).

It May work but unless the amp has a power supply like a brick outhouse it will sound poor. It could overstess the amp or have its output protection circuit "limiting". Not good.

Also the crossover may now be wrong if designed for 4 ohms. You would have to halve the inductor and double the capacitor values to correct it.

Thats the theory.

Heres the quick fix. Connect 2 ohm or higher 5 watt power resistors in series with your tweeters. This would be instead of trimming their output level on the crossover.

The tweeter is then effectively 4 ohms for the amp.

Mr Kite

[RDX]

Thanks Mr Kite, I was wondering if a series resistor would be OK.

I'll report back when I've done the switch.

Cheers, RDX

[Genoa1893]

Sorry, I missed your question. Of course, be aware to place the resistor after the xover, or you would dissipate amp power in heat

Further zero cost mod project still awaiting for time...

[Penguin]

Much has been written about the Octy speakers/stereo and I had some objections to the sound as well.

The problem (as identified by Mr Kite also) seems to be the front tweeters which sound harsh/hard and seemed to produce rather too much upper mid range. Various folk have replaced the crossovers & tweeters to much acclaim but I didn't fancy spending lots of money or changing the look either.

After removing a tweeter (complete with panel) and connecting it to a hi fi unit (in lieu of the original tweeter) I came to the conclusion the unit wasn't that bad after all. The "crossover" though lets too much upper mid (squawky type midrange ) to pass to the unit making it sound harsh & orrible!

Crossover is a single 8uF 35v non-polarisd capacitor mounted on the tweeter casing (actually I measured its value as couldn't read it) This is a rather high value to feed a tweeter - no wonder it tries to produce mid-range.....badly. I up-ended the 8uF cap. & wired in a 3.3uF instead to see what the effect was - MAGIC - most of the squawky mid-range goes, leaving the detailed Hi end being produced quite sweetly. This isn't the most hi-tech job but believe me I'm quite happy with the sound now & difference is really noticeable - no longer jarres my ears.

I would guess any value from about 3-4uF (=< 30v non polarised electrolytic)would be OK. Any bigger & the horrible harsh mid/trebble will re-appear I suspect.

This mod is achieveable just by removing the door handle/tweeter panels from the door cards (no need to remove the whole panel) and doing a little soldering of capacitors. It also preserves the "original look" and costs peanuts. (2 x 3-4uF caps)

As an observation The FM side of my unit (Stream mP3) is rather dull sounding compared with the CD /MP3 /Aux. in but this at least allows one to increase Treble (mine about +2) to bring back some sparkle, without it sounding harsh or squawky on fm.

Edited 24 September, 2008 by Penguin

[Penguin]

Very poor phone camera Pic of LH door tweeter & mod. (SWMBO gone out with real camera!)

[Mr Kite]

Penguin Hi,

Initially I was trying to remove the tweeter panel to try a similar mod but it looked very much as though I would break it.

Can you give a few more details as to how you removed it particularly at the door handle end which looked near impossible on mine.

Many Thanks

Mr Kite.

[RDX]

Hi Mr Kite,

I've managed to get the panel off. Basically I followed the intructions from this thread:

http://briskoda.net/octavia-ii/add-illumination-internal-door-handle-l-k-vrs/93651/?highlight=handles

Once you have the Torx screw off it is possible to unclip the panel at the tweeter end and then gently pull out the handle end. It is quite tricky to unclip the door lock cable but it is possible. It helps if you have small hands! It's more tricky to get the cable back on, but again it is possible.

Good luck.

RDX

[Genoa1893]

Penguin Hi,

Initially I was trying to remove the tweeter panel to try a similar mod but it looked very much as though I would break it.

Can you give a few more details as to how you removed it particularly at the door handle end which looked near impossible on mine.

Many Thanks

Mr Kite.

Hi Mr Kite,

I removed tweeter panel simply by inserting a shop card, and popping the frame out. Quite simple once you get the "feeling"

Penguin, thanks for measuring!!! I'd go with some poly cap, as soon as I find (or buy a new) soldering station :D:D

Ciao,

[A16NS V]

I've been messing around with mine for a couple of weeks and agree the tweeter's crossover is troublesome. I wouldn't recommend it but i bypassed the the OEM crossover with a soldered wire and spent a horrific day listening to a harsh sound.

I did it to answer some questions on staging and although it sounded horrid you do get some of the imaging back as more midrange comes back to the tweeter location as opposed to being dragged back to the midwoofer by your hip.

Penguin, after your 3-4uF caps mod i'd be interested in how your imaging is now? My assumptionwould be you are asking the midwoofer to do 'more work' so the staging may be more biased to the driver's side?

I've just bought some Infinity components for mine but may also try your fix to note the differences:)

[bogey555]

Does anybody know the exact impedance of the tweeter?

If it is 4 ohm then the cap should be 11.36 µF for a frequency range from 3500 Hz .

3500 Hz should be a good cut off point for the tweeter. If you know its resonance frequency, double this and this should be the cut off point. If you don't know it take 5000 to 5500 Hz as a cut off point.

If it is 4 ohm and you use 3.61 µF then the cut off point is 11000 Hz, so hardly any high frequency's would go to the tweeter. If it is 8 ohm then the cut off point is 5500 Hz and you lose less high. I' am asking myself this question because the only picture I found on the net shows an impedance of 4 ohm. So this can't be correct because you have a great improvement on your tweeter.

@ Penguin : Have you placed the cap in serie/parallel with the original one or did you disconnect it?

thanks

Edited 1 October, 2008 by bogey555

[chavdarlk]

IMHO you can't solve the problem just changing the capacitor value...

Taking up cross-over frequency enough, using first order filters (6 dB / octave), you are going to lose the mid-range.

You have to use second(12 dB)- or even third(18 dB)-order highpass filter.

Using this calculator you could note, that second-order filter with 3500 Hz cutoff frequency and 4 ohm impedance is made with !!!8 uF!!! and 0.26 mH.

Is there some inductance near the tweeter ???

Or it is just missed and needs to be added :confused:.

[bogey555]

You are correct, if you use a Butterworth filter. But the problem will be that the exact resonace frequency of the tweeter is not known. You can only use 3500 Hz if its res freq is 1750 Hz.

If it is unknown it is better to take a higher value and end up with +-5000 Hz as cut off. But 11000 seemed a bit high to me.

However it is not a bad idea to try a 0.26 mH inductance and go from a first to a second order filter

[RDX]

Hi folk's,

The tweeters have 4 ohms printed on them, which will produce a Xover freq. of 11000Hz with a 3.6uF cap, as you point out.

This does seem high. However, I did a little experiment the other day. I ran the system with the tweeters disconnected to see what it sounded like. Amazingly it didn't sound that bad! If you turn up the treble a bit the woofers produce a fair bit of top-end, very harshly though. Obviously there is no Xover for the woofer and I think it is partly to blame for the harshness of the system.

It would be interesting to hear the system with a proper Xover for the woofer as well as the tweeter.

Anyone fancy a challenge?

Cheers,

RDX