Speaker building 101 - eff ratings.

RuSsMaN
RuSsMaN Posts: 17,986
edited September 2003 in Speakers
Is there a 'rule of thumb' for how efficiency ratings increase/decrease with additional drivers? Does the wiring scheme (parallel/series) have different effects on the whole eff wise?

Ie:
2 single 86db 1w/1m wired in series = ?db 1w/1m
2 wired in parallel = ?
4 in series = ?
4 in parallel = ?

Are there other factors to consider? Not looking for pinpoint mathematics (although that would be fine too), but is there a general accepted rule to get a close guess (to actual)?

Cheers,
Russ
Check your lips at the door woman. Shake your hips like battleships. Yeah, all the white girls trip when I sing at Sunday service.
Post edited by RuSsMaN on
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  • VR3
    VR3 Posts: 29,384
    edited September 2003
    Dosn't it increase 3 db each time you add a speaker??:confused:
    - Not Tom ::::::: Any system can play Diana Krall. Only the best can play Limp Bizkit.
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  • TonyPTX
    TonyPTX Posts: 545
    edited September 2003
    Let's see if I can answer this...
    Originally posted by RuSsMaN
    Is there a 'rule of thumb' for how efficiency ratings increase/decrease with additional drivers?

    2 equal speakers play at +3dB. So two speakers with an efficency of 86 dB each should have a combined efficency of 89 dB.
    Does the wiring scheme (parallel/series) have different effects on the whole eff wise?

    No. Just affects the load on the amp. 4ohm vs. 8ohm etc...
    Are there other factors to consider? Not looking for pinpoint mathematics (although that would be fine too), but is there a general accepted rule to get a close guess (to actual)?

    The other major factor IMHO would be the actual cabinet the speakers are placed in (ported vs. acoustic suspension). I have heard that a good rule of thumb in designing the dimensions of a cabinet is to abid by the golden ratio.

    Tony
    Damn....8 lines...I've gotta put my sig on a diet now....
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  • gidrah
    gidrah Posts: 3,049
    edited September 2003
    It's been pretty much answered, but I wanna help.

    Every time you double the surface area you add 3db in dipole and focused arrays. Other designs don't quite get the full benefit, but are usually fairly close. The closer they are to each other, the closer the increase will be to 3db.

    single driver = 86db 1w/1m @ 8ohms
    2 drivers (parallel) = 89db @ 4ohms
    2 drivers (series) = 89db @ 16ohms
    4 drivers (series parallel) = 92db @ 8ohms
    16 drivers (series parallel) = 98db @ 8ohms

    Of course depending on the speakers and amp used, the halfing or doubling of the resistance can also half or double your power. Or it will stay the same, or it will damage something.

    Good luck!
    Make it Funky! :)
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  • RuSsMaN
    RuSsMaN Posts: 17,986
    edited September 2003
    2 similar, but different answers.

    Mark, I know you know what I'm thinking - line array. Your 2 driver examples follow Tony's thoughts - but you are saying as we *double* the drivers, ie 2,4,8,16,32 - each is a 3db step? (vs each individual driver = a 3db step)

    Now that I re-read Tony's post, this is what he may have been going after also.

    How about power handling? Same speaker - 5w continuous power handling. 2 drivers = 10w, 4 drivers = 20w, 8 drivers = 40w? How does parallel/series affect the useable power rating?

    Cheers,
    Russ
    Check your lips at the door woman. Shake your hips like battleships. Yeah, all the white girls trip when I sing at Sunday service.
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  • gidrah
    gidrah Posts: 3,049
    edited September 2003
    Originally posted by RuSsMaN
    Mark, I know you know what I'm thinking - line array. Your 2 driver examples follow Tony's thoughts - but you are saying as we *double* the drivers, ie 2,4,8,16,32 - each is a 3db step? (vs each individual driver = a 3db step)

    >>>That's the way I understand it.

    How about power handling? Same speaker - 5w continuous power handling. 2 drivers = 10w, 4 drivers = 20w, 8 drivers = 40w? How does parallel/series affect the useable power rating?

    >>>I might be wrong, but I think when in parallel you add the wattages, but in series it remains the same and should be treated as the lowest rated driver (or drivers in parallel) being the max.

    Cheers,
    Russ

    Do you remember those 12 8"FRs I was going to get? I still haven't received them. It's gonna get ugly over at FRDForum pretty soon. I still plan on making some pseudo straight 8s out of a bunch of 4" and some bullet tweets. I just want some big open baffle arrays.
    Make it Funky! :)
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  • RuSsMaN
    RuSsMaN Posts: 17,986
    edited September 2003
    How long has that transaction been pending? Jeez.

    Per-side I'm looking at 2 x 299-721, 7 x 269-568, and couple 269-702. (7 of the 8ohm 568's and use the 2 4ohm 702's in series as the 8th '8ohm driver - if that makes sense)

    Either straight OB, or a hybrid with the array open, but the woofs in a ported enclosure.

    The tweets would be passed at 10K - 6db/oct, just not sure I want to use more than a couple but appears I would need to in order to match the eff of the other drivers. Oh, and a simple 6db/oct low/high pass at 180-200 between the woofs and array.

    -R
    Check your lips at the door woman. Shake your hips like battleships. Yeah, all the white girls trip when I sing at Sunday service.
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  • goingganzo
    goingganzo Posts: 2,793
    edited September 2003
    i was thinking of bulding a set of speakers. i was looking at gr reaserch they have the a/v-2 and the The Diluceo. you can get the a/v-2 with a matching center but i dont know if they have a matching center for the The Diluceo and at 3 times the price.
    http://www.gr-research.com/catalog.htm
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  • HBombToo
    HBombToo Posts: 5,256
    edited September 2003
    Originally posted by RuSsMaN


    How about power handling? Same speaker - 5w continuous power handling. 2 drivers = 10w, 4 drivers = 20w, 8 drivers = 40w? How does parallel/series affect the useable power rating?

    Cheers,
    Russ

    Here is an easy way to remember and using all 8 Ohm speakers in this case.

    In a parallel network current splits and voltages remain constant. What this means for your amplifier is that it must be able to handle the total power P=V(I1+I2+I3+In).

    In a series network current remains the same but the voltage is dropped across each component. What this means for your amplifier is that it must be able to handle the total power P=I(V1+V2+V3+Vn).

    Hope this helps.

    HBomb
    ***WAREMTAE***
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  • Tour2ma
    Tour2ma Posts: 10,177
    edited September 2003
    Russ,
    Though he ended up addressing amp demands, I think what Herny said applies to the speakers' power handling capability. In either case, series or parallel, the final speaker rating would be the sum of the individual drivers' rating. Same is true of series/ parallel hybrids.

    Fits what I remember of the Bose 901's design, i.e., 270 wpc rating through utilization of 9 - 30 W drivers.
    More later,
    Tour...
    Vox Copuli
    Better to remain silent and be thought a fool, than to open your mouth and remove all doubt. - Old English Proverb

    "Death doesn't come with a Uhaul." - Dennis Gardner
    "It's easy to get lost in price vs performance vs ego vs illusion." - doro
    "There is a certain entertainment value in ripping the occaisonal (sic) buttmunch..." - TroyD
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  • Fastmerc
    Fastmerc Posts: 99
    edited September 2003
    Sorry to jump in here guys but as you are in a similar discussion...what effect if any does the crossover network place on ohm loads and power handling?
    Thanks,
    Brett
    Mains: RT20Ps
    Center: CS350LS
    R. Surround: RT16s
    R. Center: CS350LS
    F. Effects: LS/FX
    Sub: Titanic 15
    Reciever: Yamaha RX-Z1
    TV: 55 LED LCD
    Interconnects:AR, RSF, MC
    Speaker Cable:MC
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  • RuSsMaN
    RuSsMaN Posts: 17,986
    edited September 2003
    Good question.

    I'm curious also, as I'm looking at crossover components, I noticed some had a 'dc resistance' rating, measured in ohms.

    Cheers,
    Russ
    Check your lips at the door woman. Shake your hips like battleships. Yeah, all the white girls trip when I sing at Sunday service.
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  • HBombToo
    HBombToo Posts: 5,256
    edited September 2003
    Originally posted by Tour2ma
    Russ,
    Though he ended up addressing amp demands, I think what Herny said applies to the speakers' power handling capability.

    Your right Tour and for me it comes down to the chicken or egg thing.
    Originally posted by Tour2ma


    I'm curious also, as I'm looking at crossover components, I noticed some had a 'dc resistance' rating, measured in ohms.


    Now your really into the nuts and bolts of RLC circuit design. To really understand what is going on an understanding of the Complex Plane/Complex math is necessary.

    I forget alot of this due to my time away from it, "use it or lose it I guess", but from a base equation we would be looking at { a+bi } where in a capacitive or inductive circuit (a) would be the real resistance at DC and bi would be the reactive resistance. The 2 resistance if matched would give 100% power transfer across the circuit whereas if the real resistance were sightly greater or less than the real you would have what is referred to as a positive or negative match.

    I would suggest that the closer the match the greater the power transfer hence a higher efficiency.

    HBomb

    :( Its been a long time for me fellas and were diggen into alot of beer between learning this stuff and know!
    ***WAREMTAE***
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