1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Improving the sound in a Hijet.

Discussion in 'Daihatsu Hi jet' started by mael, Aug 14, 2010.

  1. mael

    mael Member

    Caps. Well if I was really being fussy about it then I'd probably use a 0.1 mF on the piezo/highest frequency tweeter. And I'd try for a 4 to 5 mF on the midrange - if it is intended to be used more like a tweeter.

    Ceramic caps (cheap ones) will do for the 0.1mF and you can use an electrolytic on th 4 - 5 mF cap. If you can get non-polar then great. But if not then use an electrolytic cap rated for around 50V. ... Unless you are planning to put enough watts through your system to run a toaster or something - in which case you need caps rated somewhat larger.

    Bottom line is use any electrolytic between around 3.5 to 5.5mFd and you would be doing well if you can tell you are using the wrong cap.

    I used a value several times what it should be so I can tell.:sly:

    * Audio experts will likely disagree with me. - There are precise values one should use, but for my hacked-together system it isn't so important. - Especially seeing as when you are driving over - say 50 km/h you can't hear the high frequency bits very well anyway.

    - I thought I'd use the truck for picking up chicks in and so the stereo only needs to sound good when the engine isn't going. Speaking of which - I reckon I can pick up loads of chicks in the Hijet. I can get at least ten in the tray.
     
  2. Groz

    Groz Member

    I Made a mistake on that last Question; I meant the sound of the truck; like the exhaust noise
     
  3. mael

    mael Member

    Hiya. It's been a long time since I have posted here. One reason is the truck is giving me no trouble.

    I've still got that pretty reasonable sound system in my truck. The only hassle was someone pulling the wires out of one of the speakers - a year or so back.

    Oh! I put insulating mat and carpeting on the roof to deaden the sound when I put in the sound system. I glued it to the roof. Well (As expected), that's sagging in the middle, but it doesn't come down much, and it won't fall. I can fix it by fitting a crossmember or two accross the top so that they are bent upwards and under lateral stress - that is if I can be bothered.

    The MD system is dated now, but although dated means it's time is ending, MDs still sound better than the solid-state digital stuff I've noticed - that'll change of course. The stick memory systems are potentially more robust and durable than MDs. B.U.T. I'm certain new electronics for sale to us disgusting peons will have a life-span of about 5 years built in. At least with my aging MD, when the condensation makes it hard for the laser to see through the lens, all I need to do is let the set warm up with the radio on - or use the air conditioner for a short time, and then it works - usually anyway.

    * I have often thought about the truck and how noisy it is. Well, it's a truck, and it's made of very thin metal and it is unreasonable to expect much in the way of creature comforts in such a small thing. But I noticed when I have the tyres pumped up hard, there is quite a bit more noise. I used to have the tyres at 3.5kg/cm3, but now I have them at 3. I think formerly the tyres were too hard - well, I'm not afraid of learning. One of the tyres developing a bulge informed me that very hard tyres might be good for economy, but after time, they can come apart from the pressure.

    I grabbed a couple of plastic sheets from some scrapped mini-trucks here and again, the back being covered does seem to reduce noise even more (but it's certainly not quiet).

    The Hijet flew through the road tests, and has given me no problems at all - but I might change the wheel bearings because I'm bored. I want to advance the timing a smidge as well, but on that score, I know that messing with it might upset things, and as it runs like clockwork (noisy clockwork), it is wise to leave well alone.

    My wife's Sambar however is in need of some advice for a serious problem though.

    Exhaust? Yeah! It's a bit on the loud side, isn't it.
     
  4. Dynamat made a huge difference.

    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]

    I need to do under the seats and inside the doors, though.

    I don't know what you used, but this stuff stays put! Make sure you really want it where you stick it cuz it ain't coming off.
     
    Acerguy likes this.
  5. mael

    mael Member

    That was a really good set of pictures showing how you did it.

    To be frank, the reason I didn't shell out for that sound insulation you used was because I didn't/don't have the money.

    I was planning to do inside the doors as well, and generally everywhere in the cab. I used asphalt-type spray paint and covered that with some foam-backed carpet. I put thick felt insulation in the roof and put carpet on that as well.

    I suppose I just compromised and improved the sound insulation somewhat.

    Y'know something funny? Well I'm 50, and I tested my ears on Youtube and I can't hear anything much over 12k anyway!

    It was using relatively softer tyres that made the biggest difference for me.

    * edit:- The 200W subwoofer that fits between the seats makes me smile. Without it, a lot of the music I like is just - tinny!

    Anyway, well done! Good job.
     
    Last edited: Sep 4, 2012
  6. I think the asphalt and carpet probably did a really good job for you. Those single ply sheetmetal panels are like drum heads. I am so close to ripping out the dash and matting the back of the trucks nose. I drive a street vehicle and the rain hitting the front of the truck at speed sounds like a whole drumline!
     
  7. Acerguy

    Acerguy Moderator Staff Member

    Great pics of your dynamat job. :)
     
  8. Groz

    Groz Member

    I put some of that rubberized stuff (expensive stuff) and it did help a bit; I think some stuff that sprays on a half inch thick would help; and no I don't have a clue what it is, I am going to leave the radio (such as it is) off. Maybe try Rhino hide?
     
  9. mael

    mael Member

    When it rains I can play a game of 'guess what the music is, and if the stereo is on at all.'

    Carpet on the outside? Now that's radical! It's also easier. I'm just thinking to myself because I think by the time I'd got the dash out I'd have the next couple of weeks figuring out how it all goes back together plus finding parts I should have put on before and have to take half of what I've done out to get it in. ... Or do without!!!

    Fantastic vehicle. It hasn't had a wash for three years, one oil change and just had gasoline and a few windscreen wiper fluid additions. Tyres last a long time even with my sideways driving a lot of the time. And so useful! The only thing you can't reasonably do in it is something I can't mention in polite company anyway.
     
  10. mael

    mael Member

    well, anything gooey is going to help deaden the sound. I think 'undercoat' is an inexpensive option which works - somewhat. Carpet helps a lot as well - anything with bubbles in it will deaden sound.

    The Hijet would cost too much to make as quiet as a regular passenger car, but asphalt spray paint and carpet and maybe some felt underlay will make it better. I seem to remember under the wheel arches must be a good place to go to town on some foamy covering for the thin steel, but balked because the work involved... and the cost of the materials, of course.

    It's not so much the engine than the road noise which is the loudest. I suppose one could try to put shock absorbing spacers here and there, but I'm quite satisfied with how my work turned out.
     
    Acerguy likes this.
  11. MotorMike76

    MotorMike76 New Member


    I know it's been a long time, but any guess as to how much (Sqft) you used for this?
     

Share This Page