Sound Quality question

LethalLee
LethalLee Posts: 27
edited October 2004 in Custom Fabrication
To the poeple who won sq competitions using ported, what is the best tuned frequency for ports with hp and lp crossovers and what the subsonic filter is at.

Would there be a problem in sound quality if the sub is only recomended for sealed and u build a ported box for it?
Post edited by LethalLee on

Comments

  • exalted512
    exalted512 Posts: 10,735
    edited October 2004
    for sound quality, usually about 30-33Hz tuning frequency
    and i dont know for sure, but as far as building a ported box for a sealed box only...it probably wont mess up the SQ, but it will cause the sub to blow quicker...if you dont ever turn it up, i think youll be fine
    -Cody
    Music is like candy, you have to get rid of the rappers to enjoy it
  • neomagus00
    neomagus00 Posts: 3,899
    edited October 2004
    generally, sub specs are tuned for a specific kind of box; sometimes, obviously, they're suited to many kinds of boxes, but most are best in one kind. you shouldn't hurt the sub if you play it ported, just make sure you set the gains right - go here - and put a subsonic (another name for highpass, just really low frequency) filter at the tuning frequency or you WILL blow the sub - no matter what's in there. other than that, keep the tuning down pretty far, like cody said, around 30, if it's a big or powerful sub, maybe somewhat lower, closer to 25.
    It's not good, very fundamentally simply not good. - geolemon

    "Its not good enough until we have real-time fearmongering. I want my fear mongered as it happens." - Shizelbs
  • bknauss
    bknauss Polk Engineer Posts: 1,441
    edited October 2004
    I have never seen someone use a ported box and win an SQ competition. The types of boxes I have seen are:
    -sealed
    -infinite baffle
    -aperiodic

    Yes, if the sub is usually recommended for sealed, there's generally a reason for them stating that.

    But again... ported and SQ just don't seem to mix.
    Brian Knauss
    ex-Electrical Engineer for Polk
  • neomagus00
    neomagus00 Posts: 3,899
    edited October 2004
    certainly sealed sounds best, but ported can provide excellent - and louder - results if done properly. sq competitions don't really require a ton of bass volume - it certainly helps on the spl score, but for the listening sections, most judges don't like a lot of bass, so sealed provides plenty of volume here.

    now, lee did mention compeitions, so you might have a very good point, bknauss - lee, are you planning on competing? cause if you are, sealed all the way; for what reasons are you looking at ported, competition or not?
    It's not good, very fundamentally simply not good. - geolemon

    "Its not good enough until we have real-time fearmongering. I want my fear mongered as it happens." - Shizelbs
  • bknauss
    bknauss Polk Engineer Posts: 1,441
    edited October 2004
    Josh and Thom said ported has been done in competition. But then again, its not seen much at all, especially if the person is experienced and is serious about winning.
    Brian Knauss
    ex-Electrical Engineer for Polk
  • neomagus00
    neomagus00 Posts: 3,899
    edited October 2004
    in this context, i was asking if lee was building the system solely for competition, in which case sealed is the only way to go - as you mentioned. however, if he's building it for daily use with some competition thrown in, and wants the ported/sealed tradeoffs, that's another thing... and if he asked about what competitors do in order to do what sounds best - as we all do - then that's a third thing :)
    It's not good, very fundamentally simply not good. - geolemon

    "Its not good enough until we have real-time fearmongering. I want my fear mongered as it happens." - Shizelbs
  • bknauss
    bknauss Polk Engineer Posts: 1,441
    edited October 2004
    Aperiodic and infinite baffle seemed to have done very well in competitions over the years also. Big names like Richard Clark and Steve Cornell have used AP, and there have been more than a handful of people who have used IB over the years.
    Brian Knauss
    ex-Electrical Engineer for Polk
  • MacLeod
    MacLeod Posts: 14,358
    edited October 2004
    John Sketoe was in the Sept/04 issue of CA&E and is undefeated in his power class and uses a ported box with a single 10.

    However hes only using 300 watts and the box appears to be EXTREMELY tuned so Im sure its not your typical ported box.

    Also, he sticks his tweeters AND mids in the A-pillars! Wierd.
    polkaudio sound quality competitor since 2005
    MECA SQ Rookie of the Year 06 ~ MECA State Champ 06,07,08,11 ~ MECA World Finals 2nd place 06,07,08,09
    08 Car Audio Nationals 1st ~ 07 N Georgia Nationals 1st ~ 06 Carl Casper Nationals 1st ~ USACi 05 Southeast AutumnFest 1st

    polkaudio SR6500 --- polkaudio MM1040 x2 -- Pioneer P99 -- Rockford Fosgate P1000X5D
  • LethalLee
    LethalLee Posts: 27
    edited October 2004
    Originally posted by neomagus00
    and put a subsonic (another name for highpass, just really low frequency) filter at the tuning frequency or you WILL blow the sub - no matter what's in there.

    If my ports are tuned to 25hz i subsonic it at 25hz or lower like 20hz?

    I was thinking of having a sub and around 4 ports. This may make people think im wack but im experimenting. Maybe four 3inch ports. Each one tuned to 25hz, 30hz, 40hz, and 50hz(maybe a lil higher). ill move the box to reflect different surfaces and tweak and port frequencies around to sound balanced. Like if 30hz port had too much boom than other ports ill dampen that area a lil bit.

    If anyone has tried multiple tuned port frequencies and know it doesnt sound good tell me before I waste wood. :rolleyes:
  • LethalLee
    LethalLee Posts: 27
    edited October 2004
    Originally posted by bknauss
    I have never seen someone use a ported box and win an SQ competition. The types of boxes I have seen are:
    -sealed
    -infinite baffle
    -aperiodic

    Yes, if the sub is usually recommended for sealed, there's generally a reason for them stating that.

    But again... ported and SQ just don't seem to mix.

    Sealed is reccomended cause it has the flattest response in car. But some tweaking of ports may solve it. Ported and sq dont mix . . . they must have made ported home theater subs cause they have the worst sq :p
  • neomagus00
    neomagus00 Posts: 3,899
    edited October 2004
    actually, a lot of home theatre subs (yes, theatRE) are made for gut-wrenchingly low movies, and thus don't need to have the tightness or clarity of musical subs, they need to have the crazy-low extension; also, room gain tends to be less than cabin gain, so they'd need a lower and flatter sealed tuning for equivalent musical results; now, this is a generalization, but a fairly accurate one...

    the problem that comes to mind with mixing port frequencies is loss of driver control. the reason that you need a subsonic filter at the tuning frequency is because below that frequency, the box no longer has control over the cone of the subwoofer, and it tends to exceed xmax very quickly and destroy itself. this is why sq ports are tuned very low, in order to cover more of the sub-bass spectrum. now, if you were to tune just two ports to say 50 and 35, the driver would begin to experience a lack of support below 50 Hz, and would likely blow very quickly. if you were to put a relatively shallow (6 dB/octave is not likely, but would be best for this scenario; it's likely that you'd have to use 12 dB/oct) filter at the first tuning frequency, in this case 50 Hz, then another steep one (24 dB/octave) at the second frequency, you could possibly get at least sound all the way down to tuning; i can see this taking an enormous amount of testing, tuning, and equalization, and at the end of the day it'd probably sound worse than a single sq-tuned ported box, and amost definately worse than a sealed box.

    if you have the time, energy, and determination to test your multiple-tune idea, i'd say go for it; start with two, then if you can get that to work, come back and tell us all about it :D.

    mac - he probably uses an insane amount of phase adjustment and time equalization to make those a-pillars work; i'm sure he's got a good soundstage, though :p.

    i'm not familiar with the aperiodic design, can anyone elaborate?

    a final note - IB is probably good if you can pull it off because it's got the lowest extension, seeing as the speaker sees essentially free-air (well, that's the idea, at least). it's like a bigger sealed box having lower extension than a smaller one, and IB is an infinitely large sealed box :)... so i can see how this would be good... pulling it off properly could be real tough though...
    It's not good, very fundamentally simply not good. - geolemon

    "Its not good enough until we have real-time fearmongering. I want my fear mongered as it happens." - Shizelbs
  • Joelsbass
    Joelsbass Posts: 637
    edited October 2004
    Originally posted by neomagus00
    i'm not familiar with the aperiodic design, can anyone elaborate?

    my thoughts exactly.... although my wording was more along the lines of... WTF is an aperiodic enclosure?
    MacLeod: I guess youre lucky Polk has such lax hiring standards.

    Josh: Damn skippy!
  • bknauss
    bknauss Polk Engineer Posts: 1,441
    edited October 2004
    AP is somewhere between sealed and vented (ported). You have an extremely small box, and a fairly large sheet of the AP membrane that allows some air through. IIRC, it works more like a sealed box at higher frequencies, but gives you better bottom end like a vented box.

    As for home subs, they're vented for that real low end like neo said. They're definitely not intended for extreme SQ... that is generally done by the two fronts alone and no other speakers. And music speakers and HT speakers are generally pretty different... but that's another story.
    Brian Knauss
    ex-Electrical Engineer for Polk
  • neomagus00
    neomagus00 Posts: 3,899
    edited October 2004
    well, other than the fact that car speakers are built to take way way more abuse, cause they do, the listening environment is totally different... for example, car subs take into account typical cabin gain, which is why you get a ~12 dB/oct rolloff, which is almost made up for by standard cabins... i hate cabins... cause i don't have one... :D

    so why isn't aperiodic in more general use, it sounds like a very good idea in theory? it also sounds very touchy and difficult to make and tune...
    It's not good, very fundamentally simply not good. - geolemon

    "Its not good enough until we have real-time fearmongering. I want my fear mongered as it happens." - Shizelbs
  • Joelsbass
    Joelsbass Posts: 637
    edited October 2004
    Originally posted by neomagus00
    so why isn't aperiodic in more general use, it sounds like a very good idea in theory? it also sounds very touchy and difficult to make and tune...

    ^ sounds like you probably just answered your own question ;)
    MacLeod: I guess youre lucky Polk has such lax hiring standards.

    Josh: Damn skippy!
  • LethalLee
    LethalLee Posts: 27
    edited October 2004
    Originally posted by bknauss
    AP is somewhere between sealed and vented (ported). You have an extremely small box, and a fairly large sheet of the AP membrane that allows some air through. IIRC, it works more like a sealed box at higher frequencies, but gives you better bottom end like a vented box.

    Its still mainly a ported box yay. You cant say sealed cause it has air leaks that escapes out of a tuned port. Now i have a chance. Forget about my multiple tuned ports I can sense it hearing only chuffing untight bass. Now does the affrodeisiac (aperiodic) design use slotted ports cause that seems easier to build. And where can i buy the aperiodic material.

    whats wrong with having 2 subs one in sealed and one in ported then adjusted with gains lowering ported performance?
  • bknauss
    bknauss Polk Engineer Posts: 1,441
    edited October 2004
    The one huge PITA about AP or IB is that you have to seal the front wave from the back wave. In english, that means you have to seal the front wall of the "box" so there is no possible way for the noise coming out the front to hit the noise coming out of the back... if that makes any sense.
    Brian Knauss
    ex-Electrical Engineer for Polk
  • neomagus00
    neomagus00 Posts: 3,899
    edited October 2004
    lee - the multiple ports idea was original, i can say i've never heard of multiple-tuning, but i think that you've come to the right conclusion with that.

    aperiodic is essentially a very small sealed box with one wall being made out of a different material. This material prevents air from moving much through it at higher frequencies, but the lower the frequency, the more air can move through it. this will provide more bass at the very low end. as bknauss said, this involves elements of an infinite baffle design in addition to the AP membrane, so as a beginner at this i'd stay far away from it.

    for 2 subs, one sealed and one ported, you're going to run into balance issues. it will be exceedingly difficult to get a flat resonse, and even if you do, the 'character' of the two subs will be different. it's like trying to mix big and little subs, or mixing brands left-and-right across the car - it just doesn't work...

    btw, technically speaking, you cant ever get true infinite baffle in a car, since it tends to be the trunk and the cabin as the 2 half-spaces... and the idea being to seal the trunk as completely as humanly possible, you're effectively just using a very very large sealed box. just a thought...
    It's not good, very fundamentally simply not good. - geolemon

    "Its not good enough until we have real-time fearmongering. I want my fear mongered as it happens." - Shizelbs
  • LethalLee
    LethalLee Posts: 27
    edited October 2004
    Originally posted by bknauss
    The one huge PITA about AP or IB is that you have to seal the front wave from the back wave. In english, that means you have to seal the front wall of the "box" so there is no possible way for the noise coming out the front to hit the noise coming out of the back... if that makes any sense.

    You cant buy one of these already tuned box from any manufacturers out there? (might be a custom design only) So the design isolates the trunk from the cabin somwhat like IB, but the ports come through the cabin or trunk. Maybe if you have the subs facing the cabin with port shooting into the sealed trunk it would hit low and not be boomy at all? Any pictures or webpages?
  • neomagus00
    neomagus00 Posts: 3,899
    edited October 2004
    no, no, AP has no ports. it is a sealed box with a special wall, and in addition to tuning the special wall, you have to completely isolate the front of the box from the back. this is usually done by mounting the box in the rear deck of the car, and sealing the trunk completely, or the equivalent.

    and no, aperiodic and infinite-baffle is all custom, and can get pretty expensive if you do it right.
    It's not good, very fundamentally simply not good. - geolemon

    "Its not good enough until we have real-time fearmongering. I want my fear mongered as it happens." - Shizelbs
  • LethalLee
    LethalLee Posts: 27
    edited October 2004
    An aperiodic install using xtant subs.

    http://www.rtol.net/scornell/2002NI.htm

    Now umm:rolleyes: Anyone here has build this yet?
  • neomagus00
    neomagus00 Posts: 3,899
    edited October 2004
    no, i don't think anyone has, but i very well may give it a shot at some point in the far future...
    It's not good, very fundamentally simply not good. - geolemon

    "Its not good enough until we have real-time fearmongering. I want my fear mongered as it happens." - Shizelbs