Closed Thread
Page 1 of 8 1 2 3 4 5 6 7 8 LastLast
Results 1 to 15 of 107

Reload Thread: drivers, enclosures and other helpful(useless) knowledge

  1. #1
    PV Audio's Avatar
    PV Audio is offline The Vision of Sound



    Join Date
    Apr 2004
    Location
    Indy
    Age
    25
    Posts
    19,655
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quoted
    0 Post(s)

    drivers, enclosures and other helpful(useless) knowledge

    this thread was inspired by another member stating that it would be good to have a general guide to loudspeakers, so here's all i know. every member is welcome to add or change anything i say to correct terms. this is to clear up the misconceptions and confusions in loudspeaker design.

    Let's start on speaker drivers themselves, and with that, a little on sound.

    General sound

    The audible range of sound is roughly 20hz-20khz. This means that anything below 20hz is subsonic (infrasonic) and i am not aware of the term for above 20khz. This means, speakers that try to sell you on frequency responses up to 25khz are not worth the extra money unless you are a dog. Now, this does not hold the same for infrasonic waves. These waves while inaudible, are rather felt. Because of the wavelength of the sound, they fluctuate less and thus travel through barriers. An easy way to think of this is by taking a sword. Drive that sword (soundwave) into the ground. It goes into the ground. Crumple the sword, and try it again. It just bounces off (this is similar to high frequencies).

    Within the audible range of sound, there are different regions. We shall start from the bottom and go up. We start with infrasonic bass (1hz-19hz). Now, from 20hz to around 60-80 hz is called subbass. The drivers used for this are subwoofers. More on the word later. From around 80-500 can be considered the bass to midbass region. The drivers used for these are woofers. Now from there up to around 2khz is the bandpass or midrange region. These drivers are obviously midrange cones. These most often are paper coned speakers anywhere from 3"-6.5" in diameter and are generally in typical cone shapes, domes or planar. From about 2.5khz to 20khz are the high frequencies. These drivers are tweeters and most generally range from 3" to 1/2". Planar or ribbon tweeters are very popular for this sound range.

    Most subbass drivers are very large, because to make large sound, you must move large air. This concept also makes sense if you think about Jurassic Park. Who wants to listen to dinosaur steps that sound like you are tapping a dixie cup? These diameters are generally 18" up to multiples of 5"-8" drivers. Most commonly, 12" subwoofers are used, and most HTIB setups are either a few 6.5" speakers in bandpass boxes.

    When selecting a speaker to use in a cabinet, it is most often useful to know the specs of the speaker. More importantly, it is useful to know what those specs mean

    I'll give you a run down on some basic terms, and suggestions on clarification and correction are very welcome.

    A - Attenuation, loss of db
    B - Magnetic flux density in gap
    Bl - Electro-magnetic force factor
    BL - Driver motor strength
    Cab - Acoustic compliance of air in the enclosure
    Cas - Acoustical equivalent of Cms
    Cmes - The electrical capacitive equivalent of Mms
    Cms - The driver's mechanical compliance (reciprocal of stiffness)
    D - Effective diameter of driver
    F3 - -3 dB cutoff frequency
    Fb - Enclosure resonance (usually for reflex systems)
    Fc - System resonance (usually for sealed box systems)
    Fs - Driver free air resonance. This is the point at which driver impedance is maximum
    Lces - The electrical inductive equivalent of Cms
    Le - Driver inductance (voice coil, mainly)
    Levc - Driver voice coil inductance
    Mas - Acoustical equivalent of Mms
    Mms - The driver's effective mechanical mass (including air load)
    n0 - The reference efficiency of the system
    p - Density of air at STP 1.18 kg/m^3 (rho)
    Pa - Acoustical power)
    Pe - Electrical power)

    Vd - Venerial disease No, but for real. It is the volume of air displaced by the speaker. A word on this: DO NOT TAKE THIS NUMBER AS DEFINITE. Many people assume that more Vd = louder sound. Most cones are rather the same size (same diameter cones i'm talking about) and those with a similar xmax will have a similar Vd. But why are some of these tailored to SPL and some to SQ? If you don't believe me, here is an example. My dayton 15" has 21mm of xmax. My DD 9515 has 13mm of xmax. THe dd walks on the dayton in spl, even though technically they have a similar Vd. Reason Vd doesn't account for pure, all out SPL is because Vd takes distortion and linear output into account. For musical listening, we only want our subwoofers to function in a linear, relatively low-distortion manor. For SPL, distortion and linear output goes out the window. All we care about is moving as much air as possible, so they can push the subwoofer well beyond it's linear limitations and out to it's mechanical limitations (Xmech) Vd is calculated by multiplying the xmax by the Sd.

    Ras - Acoustical equivalent of Rms
    Re - Driver DC resistance (voice coil, mainly)
    Revc - DC resistance of the voice coil only
    Rg - Amplifier source resistance (includes leads, crossover, etc.)
    Sd - Effective piston radiating (surface) area of driver
    Vab - The volume of air having the same acoustic compliance as the enclosures
    Vas - The volume of air having the same acoustic compliance as the driver suspension: Cms
    Vb - Net internal volume of enclosure
    Xmax - Maximum peak linear excursion of driver
    Z - Total driver impedance

    Q (es) (ts) (ms) (tc) - Q stands for "Quality Factor", which describes the ratio of energy stored to the energy dissipated. These are very useful tools when designing a cabinet. For the sake of time and people not liking to read, Qts is generally the only useful tool in PRELIMINARY cabinet construction (Qtc, someone else can explain that because i'm not too sure). Qts it the total Q of a speaker, thus Qes and Qms. A lower Qts driver is generally suited for a ported enclosure (.3>), higher values (.7<) are suited for sealed enclosures. The median values can either be used for other enclosure types. Qtc describes the total "Q" of the "system" (driver in the enclosure). Qts is used to indicate the low frequency behavior of the subwoofer. Qtc is used to indicate the low frequency behavior of the system; ringing/overshoot/decay, frequency response, low frequency extension, group delay, etc. How does this tie into the stored/dissipated energy ratio? Well, the higher the Q(tc), the higher the ratio of energy storage compared enery dissipated....resulting in "ringing" and slow decay, and an underdamped response. The lower the Q(tc), the opposite, less ringing and faster decay, and an overdamped response. A Qtc of .707 is said to have maximally flat requency response and lowest F3, with a transient response (ringing, overshoot, etc) that is "not too bad". Good graphical representation here: http://www.carstereo.com/help/Articles.cfm?id=29 I SHOULD ALSO MENTION THAT THIS IS THE TIP OF THE TIP OF THE ICEBERG ON PARAMETERS
    Enclosure types

    Let me see, where to start.

    Vented (ported) are very common enclosures at they most usually are used in subwoofers, which people seem to take the most notice to. The port on these enclosures is used to enhance or bring out a sound around a certain frequency that the enclosure is tuned to. Using damping materials in these enclosures can also smooth out the sound much like in sealed boxes.

    Sealed are very common because they are simple. 6 pieces of wood, some glue and maybe a bit of alcohol and u have yourself a sealed box. While these may seem to be easy and not very difficult to design, this is not the case. These have the tendency to be "peaky" in higher frequency ranges. They also have a tendency to require smoothing in certain response ranges. This is where the use of damping materials comes into play. Eggcrate foam, fiberglass, Dacron, pillow stuffing or Polyfill is very popular to use to dampen these waves.

    Bandpass enclosures are also common because they are easy to **** up and be loud no, but really these are probably THE most commonly used speaker designs in the commericial budget subwoofer market. Nearly, actually i'd venture to say that EVERY HTIB has a bandpass subwoofer. All bose subwoofers are actually bandpass as well. They are very tedious to design and generally do not perform well on paper or in the physical. I have heard one good bandpass, and that is unfortunately a bose. The enclosure consists of a variation of one half of the driver firing into a sealed enclosure, and the other half firing into a ported enclosure. These are VERY hard, mine you VERY VERY hard to get correct, but they are the best for sheer output when other options are either impractical or undesirable.


    Horns: Here is a brief overview of how horns work via Dan Wiggins: Horns operate on the principle of a lever and dispersion control. A high pressure, low velocity end (the throat) is connected via an air-load to a low pressure, high velocity end (the flare end). SPL is the integral of velocity, meaning that if we can double the velocity at the end of the horn, we can increase the effective SPL by a corresponding amount. Longer, slower flare rates tend to amplify the effect, and is why high SPL horns are quite long with slow flare rates. Radiation angle is also affected by the flare shape, meaning that dispersion is reduced, so the output from the off-axis angles is reduced, and that energy is redirected into the on-axis (in the flare angle) of the horn, further increasing output. This is why you can find horns that will have outputs beyond 112 dB SPL in their beam angle - a theoretically "impossible" number, since 100% efficiency is 112 dB SPL! Of course, that is for a full-space radiation pattern; cutting down the radiation angle means one can reach levels higher than 112 dB SPL over a narrowed dispersion range.

    There are alot of other types that are less popular such as transmission line, DBR (double bass reflex) and passive radiator, infinite baffle and isobaric.

    That is all for now, i'll probably update it later with more stuff when i get home, probably a general overview on filters.

    - Dave

    Single spaced parameters courtesy of Michael Lalena
    Last edited by PV Audio; 10-26-2005 at 09:26 PM.







  2. #2
    ballstothewall's Avatar
    ballstothewall is offline CarAudio.com Veteran



    Join Date
    Feb 2005
    Location
    Kansas (KSU)
    Posts
    3,054
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quoted
    0 Post(s)

    Re: drivers, enclosures and other helpful(useless) knowledge

    Sticky??? I believe this thread will be sticky worth when we get some more input from a few other members.

    Wow, I learned something today, and it sure wasen't from the classes I'm paying out the *** for.




  3. #3
    noob with an RS's Avatar
    noob with an RS is offline i poop on you



    Join Date
    Jan 2005
    Location
    earth
    Posts
    3,743
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quoted
    0 Post(s)

    Re: drivers, enclosures and other helpful(useless) knowledge

    hmm.. interesting. so i have my car system crossed over at 52 hz. my idmax plays up 2 52 hz.. and my infinity perfect components are playing from 52 hz and up.. do u guys think i should raise my crossover point? the reason im asking is because above, it says 80 hz and up are played by woofers.




  4. #4
    squeak9798's Avatar
    squeak9798 is offline Banned



    Join Date
    Jun 2004
    Location
    USA
    Posts
    26,300
    Post Thanks / Like
    Images
    16
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quoted
    0 Post(s)

    Re: drivers, enclosures and other helpful(useless) knowledge

    Too lazy to do a full write-up, so a few quick thoughts:
    • Reason Vd doesn't account for pure, all out SPL is because Vd takes distortion and linear output into account. For musical listening, we only want our subwoofers to function in a linear, relatively low-distortion manor. For SPL, distortion and linear output goes out the window. All we care about is moving as much air as possible, so they can push the subwoofer well beyond it's linear limitations and out to it's mechanical limitations (Xmech)

    • Q stands for "Quality Factor", which describes the ratio of energy stored to the energy dissipated. This ties in to Qtc...

    • Qtc describes the total "Q" of the "system" (driver in the enclosure). Qts is used to indicate the low frequency behavior of the subwoofer. Qtc is used to indicate the low frequency behavior of the system; ringing/overshoot/decay, frequency response, low frequency extension, group delay, etc. How does this tie into the stored/dissipated energy ratio? Well, the higher the Q(tc), the higher the ratio of energy storage compared enery dissipated....resulting in "ringing" and slow decay, and an underdamped response. The lower the Q(tc), the opposite, less ringing and faster decay, and an overdamped response. A Qtc of .707 is said to have maximally flat requency response and lowest F3, with a transient response (ringing, overshoot, etc) that is "not too bad". Good graphical representation here: http://www.carstereo.com/help/Articles.cfm?id=29

    • Here is a brief overview of how horns work via Dan Wiggins: Horns operate on the principle of a lever and dispersion control. A high pressure, low velocity end (the throat) is connected via an air-load to a low pressure, high velocity end (the flare end). SPL is the integral of velocity, meaning that if we can double the velocity at the end of the horn, we can increase the effective SPL by a corresponding amount. Longer, slower flare rates tend to amplify the effect, and is why high SPL horns are quite long with slow flare rates. Radiation angle is also affected by the flare shape, meaning that dispersion is reduced, so the output from the off-axis angles is reduced, and that energy is redirected into the on-axis (in the flare angle) of the horn, further increasing output. This is why you can find horns that will have outputs beyond 112 dB SPL in their beam angle - a theoretically "impossible" number, since 100% efficiency is 112 dB SPL! Of course, that is for a full-space radiation pattern; cutting down the radiation angle means one can reach levels higher than 112 dB SPL over a narrowed dispersion range.




  5. #5
    thylantyr's Avatar
    thylantyr is offline CarAudio.com Elite



    Join Date
    Apr 2005
    Location
    [Yoda] Belong to us all your base are...
    Posts
    1,395
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quoted
    0 Post(s)

    Re: drivers, enclosures and other helpful(useless) knowledge





  6. #6
    flakko's Avatar
    flakko is offline Veteran (my butt)



    Join Date
    Aug 2004
    Location
    So Cal
    Age
    28
    Posts
    10,477
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quoted
    0 Post(s)

    Re: drivers, enclosures and other helpful(useless) knowledge

    whhere is BL?




    1998 Acura TL 3.2L
    Crappy Sansui DVD player
    Stock Speakers
    ----------------------------------------------------------------------
    "Hi ladies, my name is Wo-Hen Nankan"

    "I like you. You have balls. I like balls."

  7. #7
    PV Audio's Avatar
    PV Audio is offline The Vision of Sound

    Threadstarter


    Join Date
    Apr 2004
    Location
    Indy
    Age
    25
    Posts
    19,655
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quoted
    0 Post(s)

    Re: drivers, enclosures and other helpful(useless) knowledge

    thanks everyone, i put in the new information




  8. #8
    PV Audio's Avatar
    PV Audio is offline The Vision of Sound

    Threadstarter


    Join Date
    Apr 2004
    Location
    Indy
    Age
    25
    Posts
    19,655
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quoted
    0 Post(s)

    Re: drivers, enclosures and other helpful(useless) knowledge

    thylantr, care to do a write up on line arrays? i take u as the resident expert

    perhaps on the use of phase plugs as well?




  9. #9
    PV Audio's Avatar
    PV Audio is offline The Vision of Sound

    Threadstarter


    Join Date
    Apr 2004
    Location
    Indy
    Age
    25
    Posts
    19,655
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quoted
    0 Post(s)

    Re: drivers, enclosures and other helpful(useless) knowledge

    oh and if y'all want something added, send me or post the info and i'll edit it into it. y'all better, cause i spent my lunch period writing this stuff




  10. #10
    thylantyr's Avatar
    thylantyr is offline CarAudio.com Elite



    Join Date
    Apr 2005
    Location
    [Yoda] Belong to us all your base are...
    Posts
    1,395
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quoted
    0 Post(s)

    Re: drivers, enclosures and other helpful(useless) knowledge

    Quote Originally Posted by lemans23
    thylantr, care to do a write up on line arrays? i take u as the resident expert

    perhaps on the use of phase plugs as well?
    The hard work has already been done on line array babble.
    http://www.audiodiycentral.com/resource/pdf/nflawp.pdf

    if this isn't enough, in that document there is 11 references too

    Re: phase plugs
    <McCoy aka Bones - Star Trek>"Jim... I'm a doctor not a scientist"

    Here is one resource on that topic but it's a different phase plug
    http://www.eaw.com/technology/propri...phaseplug.html

    You see them installed on high frequency cone drivers to 'help' high frequency response
    because the dust cap 'svcks'. .. and if you are clever and make a solid metal one with
    thermal joint compound it helps as a heatsink to cool the speaker, a bonus. But some
    phase plugs are of the phoney variety were the cone is just glued on the cone, so there
    is no heatsinking.




  11. #11
    PV Audio's Avatar
    PV Audio is offline The Vision of Sound

    Threadstarter


    Join Date
    Apr 2004
    Location
    Indy
    Age
    25
    Posts
    19,655
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quoted
    0 Post(s)

    Re: drivers, enclosures and other helpful(useless) knowledge

    no see, that is why i wanted u to write something lol. i don't want babble, i want things people understand. you won't learn if you don't understand the material




  12. #12
    thylantyr's Avatar
    thylantyr is offline CarAudio.com Elite



    Join Date
    Apr 2005
    Location
    [Yoda] Belong to us all your base are...
    Posts
    1,395
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quoted
    0 Post(s)

    Re: drivers, enclosures and other helpful(useless) knowledge

    Quote Originally Posted by lemans23
    no see, that is why i wanted u to write something lol. i don't want babble, i want things people understand. you won't learn if you don't understand the material
    The Jim Griffin document is as easy as it gets. He took the complicated data
    and made it easy to understand.

    Maybe just ask questions about the document itself to make it even easier?




  13. #13
    PV Audio's Avatar
    PV Audio is offline The Vision of Sound

    Threadstarter


    Join Date
    Apr 2004
    Location
    Indy
    Age
    25
    Posts
    19,655
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quoted
    0 Post(s)

    Re: drivers, enclosures and other helpful(useless) knowledge

    i added new parameters, going to start on what i know about filters after geometry stops taking me prisoner




  14. #14
    PV Audio's Avatar
    PV Audio is offline The Vision of Sound

    Threadstarter


    Join Date
    Apr 2004
    Location
    Indy
    Age
    25
    Posts
    19,655
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quoted
    0 Post(s)

    Re: drivers, enclosures and other helpful(useless) knowledge

    Quote Originally Posted by thylantyr
    The Jim Griffin document is as easy as it gets. He took the complicated data
    and made it easy to understand.

    Maybe just ask questions about the document itself to make it even easier?
    no i mean, i don't know what is really important and what people don't need to know in full. thats why i wanted ur run down, hence not like 50 pgs going into detail, just the most important things to know.




  15. #15
    PV Audio's Avatar
    PV Audio is offline The Vision of Sound

    Threadstarter


    Join Date
    Apr 2004
    Location
    Indy
    Age
    25
    Posts
    19,655
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quoted
    0 Post(s)

    Re: drivers, enclosures and other helpful(useless) knowledge

    what is sound>20khz called




Closed Thread
Page 1 of 8 1 2 3 4 5 6 7 8 LastLast

User Tag List

Posting Permissions

  • You may not post new threads
  • You may post replies
  • You may post attachments
  • You may edit your posts
1e2 Forum