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Capacitor/Inductor for sub ?

Discussion in 'Subwoofers' started by Koosnaff, Feb 14, 2001.

  1. Koosnaff

    Koosnaff
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    Hi All

    Bit of a techie question from a non-techie !

    I have a Pioneer 12" sub in a sealed custom-sized enclosure that used to be in my car. Its a DVC (Dual Voice Coil) sub, so have 2x4ohms voicecois and can be wired as 2ohms or 8ohms. It is currently wired as 8ohms, and I have an old Pioneer amp that I will use to poer the sub, but its a standard amp with no low-pass filtering etc. I have been told that I can use a Axial Capacitor or an Inductor to fit in-line on the cable from the amp to filter out unwanted frequencies, but am not sure what capacitor to go for.
    Maplins do some Audio Grade Polypropylene Axial Capacitors ranging from 100nF to 15uF.
    I would require filtering out everything above 150Hz (+/- 20%). The sub is 160wRMS nominal, 500w max, but for my purposes the amp will be delivering 100wRMS@8ohms.
    Does anyone know what cap I should be looking at, or where I can find a formula to work it out ?
    Any help/advice would be greatly appreciated.

    Yours

    Paul
     
  2. Ramius

    Ramius
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    Hi Koosnaff.

    The good news is that you wont need to make a low-pass filter. Just let your digital amp deal with it all. (I'm presuming you have a digital amp).

    The bad news is that you may be disappointed with the bass output using a car sub driver and enclosure in your home.
    Car drivers are normally designed to work in a small enclosure and produce high SPLs. They rely on cabin gain to produce the very low frequencies in car.
    The bigger the room the more sub you'll need [​IMG]

    Do you know the T/S parameters or what model the driver is and the volume of the enclosure?

    Can you make a new enclosure? Maybe ported?

    You mention an old Pioneer amp for the power, is that a car amp?

    Whoa, loads of questions for you [​IMG]

    Cheers
     
  3. Guest

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    i wouldn't place a capacitor, inductor, resistor, bridge rectifier, or anything else in series or parallel with any amp output unless you are technically competent, at the very least you run the risk of damaging the output transistors. Why not buy a simple low pass network from maplins or the like, as long as your not after huge power handling capacities these things cost next to nothing. On a further note the previous reply is quite correct drivers designed for "car stereo's" (i'm afraid i cannot bring myself to say HiFi) or at least the budget end do tend to work on the principle that you are actually sat IN the speaker enclosure and do not happily make the transition to home or domestic set-ups.

    Regards

    SteveEX
     
  4. Stick

    Stick
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    Agreed! stay away from the car sub idea. If you've ever seen a demo of an in car sub(i've seen many)in a shop, the person doing the demo will always turn the system up as loud as they can to get the bass depth and power. Try that in a car and you end up buying a new windscreen!.
    Car acoustics are a law unto themselves. By the way i cannot agree with with the comments on car audio not being of a hifi grade, My Genesis, DLS Kicker and Alpine setup can can eat many a home hifi for breakfast, and i'm not talking in terms of volume or crushing bass. Because my system does not have either in bucketloads. just fast accurate and spacious-besides I'm not into the modern s**t the 'boyz' insist on calling music!!.

    My sincere apologies for going wildy off subject,i just felt that I needed to point that out

    Cheers

    PS. a DIY sub is worth a look, and more economical that alot of the main player offerings!!
     
  5. Koosnaff

    Koosnaff
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    Hi SteveEX

    When you say don't put a cap/inductor etc in line with the output from an amp, I don't quite see your point about potential damage. You say use a low pass filter, which are actually made using a capacitors and inductors. If you don't use capacitors/inductors, you send the full-range thru to the speaker(s). While I take your point that car stereo may not be designed to listen to inside the house, I have in fact, had the sub sitting in a room of a similar size to my front room on extended (good quality) speaker cables running from the amp in my car, and it sounded ok to me (apart from the fact that all I could hear was the slightly muffled mid/high range from outside the room as I had the car doors open, and loads of bass almost blocking it out from within the room I was in. It may not be perfect, but it works in a fashion which is good enough for me for the time being. With regards to the low pass filters in Maplins, the only one that comes close is 70 quid ! ANd the cutoff is still 500hz which is far higher than I want. I currently have the sub in my car cutoff about 180hz. 150hz sounded best in the room. Those crossovers are really designed for bass/mid/high - not sub-bass.
    And they would have to put up with 100wrms which most of them don't.

    Stick - I have to agree re: car hi-fi. I have heard systems that are so accurate, they have literally sent shivers down my spine. Sit in a car with an pair of Infinity Perfect 6.1's in the front with 200wrms on tap for each, and a Phase Linear Aliante 12" Ltd sub in correct size sealed enclosure with 900wrms being shoved up it, and tell me thats not Hi Fi !

    Anyway straying well off-topic here so will stop right there...

    For Ramius, Its a TS-W303DVC 160w nominal/500w max in a sealed 42.5 litre box. The ported size should be 46.7 litres. Thats Pioneers recommended box sizes, and BlauBox gives very similar results when all the T/S params are entered ...

    What I didn't explain in previous post was that this is only a temporary thing until I get either a decent amp/receiver or a DD Philips TV (not sure what I'm gonna do there yet) Currently have a Dolby Pro-logic amp which has standard outputs but nothing for a sub which is why I need to filter the highs out.

    Cheers all
     
  6. Ramius

    Ramius
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    Now then [​IMG]

    If you do a search on the www for "low pass filter", or sub crossovers (whatever) you'll find plenty of info, go here for a start- http://www.epanorama.net/audiocircuits.html#eq

    The only T/S parameters I could get from Pioneer for the 303DVC are-
    Qts 0.37
    Fs 23 Hz
    Vas 220.71 litres

    Sensitivity of 93dB 1W/1M

    I did some quick modelling on WinISD. The sub models quite well for home cinema. I definitely suggest a larger box though. In the 42.5 litre enclosure (Qtc 0.92) you have the F3 point at 47Hz and the F10 point at 30Hz, no low end output, boomy. In larger sealed enclosure say 88 litres (Qtc 0.7) you'll have a shallower roll off, F3 43Hz & F10 25Hz.
    However in a large ported enclosure you'll fair much better-
    For example-
    160 litres,
    Tuned to 20Hz (4" port, 11.8" long)
    F3 30Hz
    F10 17Hz
    Room gain should help the bottom end.
    Just what you need for home cinema.

    So keep your sub and in the future try a large ported enclosure. For what MDF costs you might as well.
    You'll probably be surprised at how good it performs.

    Cheers.
     
  7. Koosnaff

    Koosnaff
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    Hi Ramius

    Thanks very much for the info. I had a play with WinISD too, and put in all the params, and you are pretty much spot on (as I presumed you would be). One question I have tho, is when measuring the literage of the enclosure, do you have to take into account the bracing required, and if so, how do you work it out ? Is it a hit or miss thing, or is it fairly easy to work out the displacement caused by the internal structure ?

    Again, many thanks

    Paul
     
  8. Koosnaff

    Koosnaff
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    Hi Ramius - forgot to mention that in the latest version of WinISD, the TS-W303DVC is already in the database with all the correct params anyway ...

    Be lucky !!
     
  9. Ramius

    Ramius
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    Everything has to be accounted for. The bracing, the port and the displacment of the driver.

    Volume of a rectangular solid- length x width x height

    Volume of a cylinder- Pi x r squared x length

    Measure it all & add it all up.

    Cheers.
     
  10. Koosnaff

    Koosnaff
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    Hi Ramius

    Darn - I thought you were going to say that. Still, keeps it interesting.

    Cheers
     
  11. Dominic

    Dominic
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    Koosnaff

    well a lot of talk about not using car subs in the house...
    hmm
    i have a couple of kenwood 10" subs in a custom box from the uk SPL champion.. to say that its not hifi is c$%p, we're talking above 130db.
    These are being feed from a 2*70w Alpine Car amp runnig off a custom Power supply from a local windings firm, the Transformer happily supplies up to 40amp at 14 volts.

    To sort out the LF i have an active crossover from the states.. an Audio Control 2XS running at 90hz low pass, with this fed from the sub out of my dolby digital amp its fantastic, but even if i run prolgic or stero sources the active crossover sorts out the LF.
    if you can get your hands on an active xover then try it, if not the inductor in line with the speaker output will suffice, altough with no control of level or xover freq, as with an active one.

    good luck

    Dom
     
  12. Koosnaff

    Koosnaff
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    Hi Dom

    Funny you should mention that. I have been recently thinking about doing something similar. I can get a switched power supply from Maplins - they do one that supplies 5-15v (variable) at 40A but its £149.99, or they do one for £99 that will do 25A. Now, seeing as my amp (Jensen, bridged=200wrms)only has a 25A fuse, in theory that should be enough. I can the use the variable (40Hz-240Hz) filter in the amp to set the cutoff. It may well be the best idea allround, and then I can keep my Pioneer seperates amp for something else...
    If you don't mind me asking, what did you pay for your transformer ?
     
  13. Dominic

    Dominic
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    This sounds like a good idea if you can get hold of the PSU, i had a friend at the windings firm that make transformers for Trace Elliot, and he made the transformer, we then went to maplins and bought a 40amp bridge rectifier and 2 4500 micro farad 63v electrolitic capacitors, and built it all. It supplies around 14v DC at up to 40amp.
    It cost me about £5 all in, and a pint of best.
    I could enquire at the windings firm about a full retail version. which would mean you would have to only buy the rectifier part of the PSU.

    Dominic
     
  14. Guest

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    For what its worth and with all due respect the DB ability of your "car set-up" has absolutely nothing to do with wether it should be considered as hi-fi i really think that we are talking about two entirely different subjects. Realistically your Alpine 70w amps are likely to offer the same experience as sticking your head in a dishwasher while listening to a pocket transistor radio when comparing it to say a Krell mono-blocked Krell transport and DAC which would most certainly be considered as HiFi buy anyone into "HiFi"

    SteveEX
     
  15. Guest

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    For what its worth and with all due respect the DB ability of your "car set-up" has absolutely nothing to do with wether it should be considered as hi-fi i really think that we are talking about two entirely different subjects. Realistically your Alpine 70w amps are likely to offer the same experience as sticking your head in a dishwasher while listening to a pocket transistor radio when comparing it to say a Krell mono-blocked Krell transport and DAC which would most certainly be considered as HiFi buy anyone into "HiFi"

    SteveEX
     
  16. Dominic

    Dominic
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    SteveEX

    Firstly, i didnt realise these forums were so serious, if i thought it was going to turn into a playground slagging match , i could have brought my football.

    steve my info for Koosnaff was only advice as to his question, i dont care about what you have or havent got or whether it sounds good.

    As for the transistor Radio in the dishwasher, you really should get out more.

    Koosnaff, i can only advise you on what ive done, i hope you appreciate it, good luck.

    Dom

     
  17. Ramius

    Ramius
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    Now then. [​IMG]

    Just because it's car audio doesn't mean it's not hifi. One of the best 12" drivers on the market is the Audiomobile Mass 2012. http://www.audiomobileinc.com/main.htm
    A bit more on that later.

    As I mentioned in a earlier post above-
    Car drivers are normally designed to work in a small enclosure and produce high SPLs.
    They rely on cabin gain to produce the very low frequencies in car.

    So you have to model your car audio driver with a design program and see if it's suited for home cinema use, it might be ok, might not be.

    I remember a guy in the states used a Infinity Kappa Perfect 12.1 with very good results.


    Back to the Mass 2012. I had a couple of e-mail exchanges with a guy called TerryC who posts on the Home Theatre Forum. I asked about the Mass 2012 as he had built a sub for a friend using 2 Mass 2012 12" drivers in a 11 cubic foot enclosure, tuned to 17Hz with 1400 Watts on tap from a Crown K1 amp.
    Read more here- http://www.hometheaterforum.com/uub/Forum17/HTML/002804.html

    Now this is a DIY sub using car audio drivers, I think the total cost to build was about $2000 (thats including the $1200 Crown amp), Terry sent me the list of equipment his friend Rich uses this sub with-

    >>>>Rich the owner of this sub has matched it with Meridian DSP6000 $20,000, Meridian DSP6000 mains $12500, DSP5500 sides $6250, DSP5500 Center and $6000 DSP5000 Rear speakers and then add the $10,000 Meridian 861 processor!<<<<<<

    That's not hifi?????

    A DIY sub will never be better than a commercially manufactured sub??? Rubbish.

    Cheers.
     
  18. Koosnaff

    Koosnaff
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    Dom

    Cheers for your post. I know exactly where you are coming from and I do appreciate it. It would seem that some people cannot differentiate between giving advice, and giving unsubstantiated opinions. I think I will stick with the idea of using the car amp, which seems to do the job quite well. It is definately better matched to the sub than the Pioneer seperate amp (which would also be a bit low on power - 60wrms short of what the car amp can deliver)

    Ramius, you little diamond. Well responded that man !

    For info, I have take your box size (160 litres) as my pattern. I was then thinking of extending the top slightly to incorporate the amp and the power supply (cooled with a couple of high-volume brushless fans drawing cool air over the heatsink fins with an outlet the other end. The fans (I have used them in the past when builing very overclocked PC's) are almost silent. The idea being that you only see the sub box, and not all the bits that go with it. The only thing I havent decided on is what to put between the amp/power supply, and the wood it will be fixed to as I want something that can absorb vibration. I dont want the amp mounted directly on the wood as it will change the resonance characteristics slightly, and also dont want too much viration on the amp. I was thinking of something like dynamat or the like - if you know of something better, I would appreciate the info.

    Many thanks to all who have contributed to my original post.

    Cheers
     
  19. Guest

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    Gentlemen gentlemen, firstly, my dishwasher remark was, i thought a humourous retort to your rather blunt "c$%p" inference.
    Secondly without any offence intended i have been involved with what i would refer to as high end HiFi for some 15 years now AND i have also attended several large "car stereo" enthusiast gatherings and competitions i.e Wembley etc etc. Now please remember i can only say as i find and I DO SAY that whilst i have heard some FRIGHTENING car set-ups (one chap have a transit completely decked out with MDF and installed a huge power-supply to drive 8*18" Fane drive units 8*10" mids etc etc) there has been NO set-up to match the "HI-FIdelity" abilities of the high-end home variety, at least not in my (as i consider) not inconsiderable experience.

    Hoping not to "tread on anyones toes" we're all entitled to our own opinions.

    Regards

    SteveEX
     
  20. Guest

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    Gentlemen gentlemen, firstly, my dishwasher remark was, i thought a humourous retort to your rather blunt "c$%p" inference.
    Secondly without any offence intended i have been involved with what i would refer to as high end HiFi for some 15 years now AND i have also attended several large "car stereo" enthusiast gatherings and competitions i.e Wembley etc etc. Now please remember i can only say as i find and I DO SAY that whilst i have heard some FRIGHTENING car set-ups (one chap have a transit completely decked out with MDF and installed a huge power-supply to drive 8*18" Fane drive units 8*10" mids etc etc) there has been NO set-up to match the "HI-FIdelity" abilities of the high-end home variety, at least not in my (as i consider) not inconsiderable experience.

    Hoping not to "tread on anyones toes" we're all entitled to our own opinions.

    Regards

    SteveEX
     
  21. Ramius

    Ramius
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    SteveEX,

    I knew what you were getting at and I agree with you, I was just making my point.

    Koosnaff.

    I'd keep the amp+power separate from the sub. Make a simple box for them or something.


    Changing the subject slightly,

    Look at this- http://www.aerialacoustics.com/sw12sub.htm http://www.aerialacoustics.com/sw12thmb.htm

    Nice subwoofer, $5000.

    Now this sub uses a driver which is an extremely close relative to the Audiomobile Mass 2012. In fact the Mass driver has more each way travel, 19mm as opposed to 15mm.

    You could DIY the Aerial for about a 1/5 of its cost.

    The Aerial does look really nice though. [​IMG]

    Given the choice I know what I'd do.

    This is hifi. [​IMG]
     
  22. Koosnaff

    Koosnaff
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    Cheers Ramius, yep. Nice looker that one but totally agree that you could DIY it cheaper without suffering any losses of quality.


    Time to put the HiFi thing to bed, I think.
    I just looked up Hi Fi in Websters dictionary, and it basically says that Hi Fi equipment, typically, comprises of a deck for playing vinyl records, a tuner for radio broadcasts, a tape recording mechanism, an amplifier to drive the above and possibly a CD player, and at least 2 speakers.

    So, from that, I derive that "Hi Fi" is totally subjective. We all know that what sounds good to some people, may not to others. Some like bass - some like trebles and definition. I think its a case of each to his own to decide whether the reproduction is High Fidelity or not. When you get in a middle-of-the-road car with standard equipment, it generally sounds dull, uninspiring and 'low fidelity' (IMHO), but then fit a head unit and speakers/amps that have had considerable research/development and the sound is vastly improved - 'Hi Fi' (IMHO). Car Hi Fi is so called because it is what it is. The Fidelity of the sound reproduction is HIGHer than what it generally replaces as standard kit.
    Comparing home Hi Fi to car Hi Fi could be likened to comparing a laptop and a fully fledged desk workstation. Just beacuse you spent £4000 on your workstation and £1000 on your laptop, does not mean the laptop is c%*p, even when compared to the workstation. They are both designed as well as possible for their individual environments, and both have their place. And remember, if all you want to do is add up some figures, then neither is necessarily any 'better' than a pocket calculator.

    I suggest that it's down to what the individual receives from the experience as to whether its Hi Fi or not, as we all have differing views on how it should sound ...

    Oh, and to SteveEX - you moved the goalposts!
    There is obviously a world of difference between 'Hi Fi', and 'High-End Hi Fi'
    I would certainly bow to the fact that Car Hi Fi (which I consider it to be) and High-End home Hi Fi could never really be compared as for a start you are hampered by the many problems associated with lack of accoustical ability in a cars interior. Nethertheless, I would still defy you to sit in, say, Gary Handa's BMW and tell him that it's not 'Hi Fi'...

     

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