warbs

Hi,

After hours and hours - I've finally got Infinity 605's fitted into my front doors coupled to a JVC-SH99R head unit with no extra amplification.

I've sound proofed the doors with some black stick-on stuff, as well as the foam underlay used under wooden laminate floors to cut out the rattles (which is perfect) - and blu-tack round the studs.

I'm pretty sure I'm not going to be able to improve the soundproofing any further.

Cutting to the chase....I've noticed that I still get a lot of what sounds like rattle or distortion at low frequency and high volume (high enough not to hear TSL backbox anyway!) - but I'm beginning to suspect this is down to MP3 quality and not the speakers/headunit...Sooner or later I'll get round to ripping a bass heavy track to compare the MP3 playback with Original - anyone got an opinion on whether it's likely to be an MP3 thing or my installation ineptitude ?

When this sounds good it's great - but occasionally the extra noise drives me crazy - should I just get used to this ?

It's dance stuff that causes the distortion..

Cheers

Chris

DJ Dunk

iTrader: (5)

Wouldn't have thought It'd be the MP3's, although it depends at what bitrate they were created at. If they are sub 112kbps then they could be to blame. Obviously a lot depends on the original source too. Like you say, try out an Audio CD and a 192kbps or 160kbps MP3 with the same track and see how much difference it makes. That way at least you can rule out MP3 distortion.

David_Wallis

All you could have got wrong really is not got a good seal with the speaker... (dont use silicone whatever you do..) not tightened it up, or wired them out of phase...

What crossovers are you using, are they wired up correctly and can you change the crossover points?

David

warbs

I used the original crossovers that come with the 605's.

The Woofers are mounted on MDF spacers and are tight.

I used the original wiring and made extensions from it into the crossover. All the wires are stuck down or wrapped in foam and there's a door shaped piece of foam between the door and the interior panel.

Suppose it could be the original wiring, or part of the window mechanism that's making the noise.

I don't think the wiring is the wrong way round - if it is wrong will it cause any damage, or is it safe to swap it round to see ?

I'll try ripping a track to various MP3 bitrates and see what the difference is really like before I spend any more real time or cash on it.

I suppose when I finally get round to putting some bass into the boot I can turn down the bass on the fronts and the problem will just go away - as if by magic ?

Thanks for the advice.

Chris

DJ Dunk

iTrader: (5)

Thats what I just did. Front 605's running off the headunit and an amped Inifity bass tube in the boot to compensate for the lack of bass in the front. Sounds mile better now, well pleased They are not very good speakers for bass, more of a mid-range driver.

David_Wallis

Wouldnt turn the bass down, I would make your own crossovers with coils and caps then you can still have the bass turned up

You can change the phase without affecting anything.... You should really replace all the speaker wire, but if your running them off the head unit then I doubt you've got enough power / quality to notice the difference.

David

chiark

Some encoding *can* cause bass distortion, but this is exceedingly rare. The only time I've heard it on a reproducable track is the very low stuff on LFO/LFO (remember them? ) . Strangely, this happens on both Minidisc and MP3 at any bitrate.

Given that you're probably not referring to that track I'd go with putting some passive filtration in your fronts.

Just a thought, have you played the track at the same level with the door cards off, just to see if anything's resonating? The other possibility is that the drivers could be hitting their maximum excursion which means that they collide with the door card...

Nick.

warbs

Chiark - I remember LFO although I never had a whistle to blow along to the music! - this is what I was getting at really I wondered if mp3 occasionally throws away too much - although I suspect this is not my real problem.

With the door cards off the distortion is still there - so I expect I'm just running them too loud - like AudioGMan said - and I'll check the autoleads thing out.

Thanks for all the comments.

Chris

warbs

Hmmm, just swapped the polarity into one of the cross-overs and the sound improved - certainly had to turn the volume down to get the level of bass I am used to! - so I assumed they were out of phase....did a queck check on the other crossover - ie. swapped the polarity going into it and the sound is sublty better still - nowhere near as big a difference though - now I'm really confused!

Which would make the bigger difference - left and right out of phase or polarity wrong on both ?

Chris

audio g man

If they are both wrong then they are actually both right ie. the same.

audio g man

I remember LFO too.

Sounds like a massive polarity checking session may be order.

audio g man

As said, changing the polarity won't cause more distortion.

It sounds like you're just whacking too much bass through 'em.

I'd get a couple of caps rated around 125hz (this will stop everything under 125hz going to the speakers) and stick them in the positive speaker wires either between the h/u and x-over or between the x-over and midbass driver. Autoleads part no. G5-2318

These have a 6db per octave slope but they'll do a good job. With these installed you will hear less distortion at high volumes and they will prolong the life of your speakers.

If you're considering buying an amp and sub, I'd buy a 4 channel amp and use channels 1 & 2 to power the Infinitys and bridge channels 3 & 4 into one to power the sub. Then you can use the built-in active filters and you won't need the above.

Lastly, I'd upgrade the speaker cables for better efficency.


[Edited by audio g man - 6/13/2002 10:30:34 AM]