Speaker and Amp selection

Archived from groups: rec.audio.pro (More info?)

I'm building a little system using a speaker switch. The unit takes
amplified input and outputs to 8 speaker zones. Each zone can be
independently turned on and off. How can I figure out what the proper
speakers / amplifiers to purchase are?

I'm not looking for brands or anything but more about the power of the amp
that I need to properly power the speakers w/o blowing them. I'm confused
on how the Amp can be used to supply enough power so that lets say 4 of the
zones are appropriately powered and also not blow out the speakers when only
1 zone is in use. Sorry if this question is dumb; I'm not that clear on
this stuff.

I'm also not sure what is the simplest amp that can do the job. I just need
one input, and one output (in the form of speaker wire connections).

Thanks,
Frank
16 answers Last reply
More about speaker selection
  1. Archived from groups: rec.audio.pro (More info?)

    Frank A <notme@yahoo.com> wrote:
    >I'm building a little system using a speaker switch. The unit takes
    >amplified input and outputs to 8 speaker zones. Each zone can be
    >independently turned on and off. How can I figure out what the proper
    >speakers / amplifiers to purchase are?

    Buy the Yamaha Sound Reinforcement Handbook and read the section on
    70 volt systems.
    --scott
    --
    "C'est un Nagra. C'est suisse, et tres, tres precis."
  2. Archived from groups: rec.audio.pro (More info?)

    In article <1ygQc.3171$zc4.3001553@news4.srv.hcvlny.cv.net> notme@yahoo.com writes:

    > I'm building a little system using a speaker switch. The unit takes
    > amplified input and outputs to 8 speaker zones. Each zone can be
    > independently turned on and off. How can I figure out what the proper
    > speakers / amplifiers to purchase are?

    Use a constant voltage system. Put a "70V" transformer at the output
    of the amplifier and either use speakers that are already set up for
    70V operation or get a transformer for each one.

    In this system, you decide how many watts you want to deliver to each
    speaker and buy the appropriately sized transformer (typically 5, 10,
    25 watts). The impedance is such that the amplifier side has the
    correct impedance to draw the rated power at 70 volts. Just make sure
    the amplifier has sufficient power to handle the maximum load you
    intend to put on it and you'll be OK.

    But better check with the switch manufacturer to be sure that there
    isn't some solid state stuff inside that won't like the higher
    voltages involved.


    --
    I'm really Mike Rivers (mrivers@d-and-d.com)
    However, until the spam goes away or Hell freezes over,
    lots of IP addresses are blocked from this system. If
    you e-mail me and it bounces, use your secret decoder ring
    and reach me here: double-m-eleven-double-zero at yahoo
  3. Archived from groups: rec.audio.pro (More info?)

    "Scott Dorsey" <kludge@panix.com> wrote in message
    news:cesbhv$s3s$1@panix2.panix.com...
    > Frank A <notme@yahoo.com> wrote:
    > >I'm building a little system using a speaker switch. The unit takes
    > >amplified input and outputs to 8 speaker zones. Each zone can be
    > >independently turned on and off. How can I figure out what the proper
    > >speakers / amplifiers to purchase are?
    >
    > Buy the Yamaha Sound Reinforcement Handbook and read the section on
    > 70 volt systems.
    > --scott
    > --
    > "C'est un Nagra. C'est suisse, et tres, tres precis."

    Any chance you could give me the basic jist of things. I don't have that
    book handy and am very anxious to start shopping around for the equipment.

    Frank
  4. Archived from groups: rec.audio.pro (More info?)

    In article <z6qQc.6549$zc4.4526745@news4.srv.hcvlny.cv.net>,
    Frank A <notme@yahoo.com> wrote:
    >
    >"Scott Dorsey" <kludge@panix.com> wrote in message
    >news:cesbhv$s3s$1@panix2.panix.com...
    >> Frank A <notme@yahoo.com> wrote:
    >> >I'm building a little system using a speaker switch. The unit takes
    >> >amplified input and outputs to 8 speaker zones. Each zone can be
    >> >independently turned on and off. How can I figure out what the proper
    >> >speakers / amplifiers to purchase are?
    >>
    >> Buy the Yamaha Sound Reinforcement Handbook and read the section on
    >> 70 volt systems.
    >
    >Any chance you could give me the basic jist of things. I don't have that
    >book handy and am very anxious to start shopping around for the equipment.

    There is some discussion of 70V systems in the FAQ for this group, but you
    really want to read the book and you also want to look at a couple installed
    systems before you even think about buying anything.
    --scott
    --
    "C'est un Nagra. C'est suisse, et tres, tres precis."
  5. Archived from groups: rec.audio.pro (More info?)

    I'd recommend an amp that works with 70 volt systems. I've used the
    JBL ceiling speakers in a 4 zone install with attenuators on a couple.
    There's some good stuff on thier site. Check out the sound system
    design manuals.

    http://www.jblpro.com/pages/tech_lib.htm
  6. Archived from groups: rec.audio.pro (More info?)

    "Mike Rivers" <mrivers@d-and-d.com> wrote in message
    news:znr1091708849k@trad...
    >

    > Use a constant voltage system. Put a "70V" transformer at the output
    > of the amplifier and either use speakers that are already set up for
    > 70V operation or get a transformer for each one.
    >
    > In this system, you decide how many watts you want to deliver to each
    > speaker and buy the appropriately sized transformer (typically 5, 10,
    > 25 watts). The impedance is such that the amplifier side has the
    > correct impedance to draw the rated power at 70 volts. Just make sure
    > the amplifier has sufficient power to handle the maximum load you
    > intend to put on it and you'll be OK.
    >
    > But better check with the switch manufacturer to be sure that there
    > isn't some solid state stuff inside that won't like the higher
    > voltages involved.
    >

    Just so I understand this correctly, what happens here is that lets say I
    buy a 150W amp. I use the 70V transformer on the output of the amp (but
    before my distribution box) Each speaker would hav e a transform (lets say
    10 W) so that it only gets 10 W regardless of if 1 speaker pair is active or
    all 8? Is that correct?

    I had a second thought (that might be crazy). Since this system is being
    controlled by a computer, I was thinking that if I had the same 150W amp,
    and a bunch of regular speakers (all same Watt) and then had my software
    alter the volume of the computer (which is the input to the AMP) to control
    the overall power? E.g. If 1 speaker pair is active computer volume =10% ,
    2 speaker = 20%, etc... Is that a crazy / silly / stupid idea?

    Thanks again
  7. Archived from groups: rec.audio.pro (More info?)

    Frank A <notme@yahoo.com> wrote:
    >
    >
    >Just so I understand this correctly, what happens here is that lets say I
    >buy a 150W amp. I use the 70V transformer on the output of the amp (but
    >before my distribution box) Each speaker would hav e a transform (lets say
    >10 W) so that it only gets 10 W regardless of if 1 speaker pair is active or
    >all 8? Is that correct?

    Right. Or you can use an amplifier that will drive a 70V system directly.

    You can not only swap speakers in and out of the system, but you can put
    attenuators in front of speakers and adjust the level of each individually
    without affecting the level of the other speakers.

    As long as the total system wattage is lower than the wattage rating of
    the transformer or amp, everything is fine.

    BUT, the reason why this works requires a long explanation and you really
    should read the FAQ on the subject.

    >I had a second thought (that might be crazy). Since this system is being
    >controlled by a computer, I was thinking that if I had the same 150W amp,
    >and a bunch of regular speakers (all same Watt) and then had my software
    >alter the volume of the computer (which is the input to the AMP) to control
    >the overall power? E.g. If 1 speaker pair is active computer volume =10% ,
    >2 speaker = 20%, etc... Is that a crazy / silly / stupid idea?

    Aside from the fact that paralleling all those speakers will cause the
    amplifier to see _way_ lower output impedance than it is designed for?
    --scott

    --
    "C'est un Nagra. C'est suisse, et tres, tres precis."
  8. Archived from groups: rec.audio.pro (More info?)

    >
    > Just so I understand this correctly, what happens here is that lets say I
    > buy a 150W amp. I use the 70V transformer on the output of the amp (but
    > before my distribution box) Each speaker would hav e a transform (lets say
    > 10 W) so that it only gets 10 W regardless of if 1 speaker pair is active or
    > all 8? Is that correct?

    YES... assuming a SET CONSTANT LEVEL for what's going through the amp.

    >
    > I had a second thought (that might be crazy). Since this system is being
    > controlled by a computer, I was thinking that if I had the same 150W amp,
    > and a bunch of regular speakers (all same Watt) and then had my software
    > alter the volume of the computer (which is the input to the AMP) to control
    > the overall power? E.g. If 1 speaker pair is active computer volume =10% ,
    > 2 speaker = 20%, etc... Is that a crazy / silly / stupid idea?

    It's fun

    it's interesting

    it's WAY more complicated and accident-prone that what you initially said
    you wanted.

    AND most importantly it does NOTHING about the mismatch of the speaker-load
    to the amp.

    Say you have a typical 8ohm amp output...
    with 8-ohm speakers, you can turn on ONE speaker and have a match

    turn on 2 and you have a 4-ohm load... will the amp tolerate that? probably

    turn on all 10 speakers and you have a less-than-1-ohm-load... looks like a
    dead short to the amp
    poof.


    A 70v system runs (in essence) runs the AMP always at full output (not
    clipping, merely at a set output level) -YOU- then decide IN THE DESIGN
    PHASE how much power you NEED at each speaker in the room it's in. Since
    there is a STANDARD here (the amp is built so that at full-power, it
    averages 70v across the output) You place a special transformer AT THAT
    SPEAKER which then is hard-wired to pull some percentage of the amp's
    running power into that speaker. the transformer pulls XXwatts off a 70v
    line and then matches it to that speaker. Usually these transformers have
    several wire choices so you can feed the speaker, say, 1/2w 1w 2w 4w
    10w depending on what wires you hook up to the amp line. That speaker will
    be louder or softer relative to others depending on how much power it can
    pull off the line.
    It's a hell of a lot like lightbulbs for different rooms on a single
    circuit, some you want brighter, some you want dimmer but they all work off
    the same line voltage. You want to be able to turn any one or more of them
    ON at any time and not affect the others or blow the breaker.

    Say you have 10 speakers and 100 watts (in REALITY you will lose some small
    amount of real power going through the transformers... so we'll assume you
    have a 120 watt amp but are going to be USING 100 watts to keep the math
    easy)

    If you plan to use ALL speakers at once at some time, you need to remember
    that you only have 100 watts to use amongst ALL of them. Each speaker could
    have, say a 10 watt transformer on it so when they're all ON, they;re
    together drawing 100 watts. If 5 rooms are bathrooms and the other 5 are
    bedrooms, you might want to draw only 2watts for each bathroom, that's 10
    watts for the baths and then leaving the rest (90watts) for the 5 bedrooms
    (18watts each).

    The simplicity here is that the amp is matched to EACH speaker by that
    speaker's transformer and, as long as the TOTAL load can never be more than
    the amp can deliver, everybody's fine and no matter which speakers are
    switched on or off (since the amp is always at the same level and each
    speaker is matched to teh amp) no volume change happens to any speaker when
    other speakers are switched on or off.

    Buy good xfrmrs (cheap ones start to look like shorts at lo frequencies)

    You're describing classic mistakes-in-ignorance approaches in your posts and
    thus really should heed the first reccomendations you got...
    GET, READ, and STUDY either the YAMAHA book on this AND get the DAVIS Sound
    Engineering book ... best coverage of it I know.
    If you dont really understand this approach, you will, at best have a
    confusingly bad-sounding system and more likely just spend much money and
    turn it into smoke.
  9. Archived from groups: rec.audio.pro (More info?)

    > >"Scott Dorsey" <kludge@panix.com> wrote in message
    +*+*+*+*+*+*+*+*+*+*
    > There is some discussion of 70V systems in the FAQ for this group, but you
    > really want to read the book and you also want to look at a couple
    installed
    > systems before you even think about buying anything.
    > --scott
    ___________________________

    Yup, do like scott says.

    -bg-
    www.thelittlecanadaheadphoneband.ca
  10. Archived from groups: rec.audio.pro (More info?)

    "**bg**" <info@thelittlecanadaheadphoneband.ca> wrote in message
    news:VCsQc.15810$M95.14735@pd7tw1no...
    > > >"Scott Dorsey" <kludge@panix.com> wrote in message
    > +*+*+*+*+*+*+*+*+*+*
    > > There is some discussion of 70V systems in the FAQ for this group, but
    you
    > > really want to read the book and you also want to look at a couple
    > installed
    > > systems before you even think about buying anything.
    > > --scott
    > ___________________________
    >
    > Yup, do like scott says.
    >
    > -bg-
    > www.thelittlecanadaheadphoneband.ca
    >
    >

    I've read through the questions on http://www.recaudiopro.net/faq/index.htm
    that seemed relevant to my situation. Yet I see know discussion of 70V
    systems. Perhaps they are referred to by another name in the FAQ, or I'm
    just blind. Am I looking in the right place?

    Frank
  11. Archived from groups: rec.audio.pro (More info?)

    >
    > >I had a second thought (that might be crazy). Since this system is being
    > >controlled by a computer, I was thinking that if I had the same 150W amp,
    > >and a bunch of regular speakers (all same Watt) and then had my software
    > >alter the volume of the computer (which is the input to the AMP) to
    control
    > >the overall power? E.g. If 1 speaker pair is active computer volume
    =10% ,
    > >2 speaker = 20%, etc... Is that a crazy / silly / stupid idea?
    >
    > Aside from the fact that paralleling all those speakers will cause the
    > amplifier to see _way_ lower output impedance than it is designed for?
    > --scott
    >
    > --

    Just to try to shed some more light on what I'm working with. The
    manufacturer of the speaker
    distribute/selector(http://www.hacs.com/ab8ss.html) had the following char
    on their site:

    Resistance impedance matching information:
    Number of speakers selected= 1 2 3 4 5 6 7 8
    Ohm load seen by amplifier= 8.49 4.98 4.13 3.96 4.05 4.27 4.85 4.92
    % power to speakers= 94 80 64 50 40 31 29 20
    max power internal resistors 10 20 30 40 50 60 70 80
    max power speakers 156 80 53 40 33 27 29 20
    max power from AMP 166 100 83 80 83 87 98 100

    Since with all 8 speakers the impedence seen by the amp is show at 4.92 with
    a min impedence of 3.96. From some reading I've done I was thinking that
    most amps would be able to handle that.

    Frank
  12. Archived from groups: rec.audio.pro (More info?)

    Frank A <notme@yahoo.com> wrote:
    >
    >Just to try to shed some more light on what I'm working with. The
    >manufacturer of the speaker
    >distribute/selector(http://www.hacs.com/ab8ss.html) had the following char
    >on their site:
    >
    >Resistance impedance matching information:
    >Number of speakers selected= 1 2 3 4 5 6 7 8
    >Ohm load seen by amplifier= 8.49 4.98 4.13 3.96 4.05 4.27 4.85 4.92
    >% power to speakers= 94 80 64 50 40 31 29 20
    >max power internal resistors 10 20 30 40 50 60 70 80
    >max power speakers 156 80 53 40 33 27 29 20
    >max power from AMP 166 100 83 80 83 87 98 100
    >
    >Since with all 8 speakers the impedence seen by the amp is show at 4.92 with
    >a min impedence of 3.96. From some reading I've done I was thinking that
    >most amps would be able to handle that.

    This is not a simple switchbox.

    This is a box that is throwing series resistors on each speaker as you
    increase the number of speakers on the load. This means that as you
    add more speakers, first of all the amount of power being thrown away
    increases (note here that when you have 8 speakers, 80% of the power is
    being thrown away with the series resistors and only 20% is making it to
    the speakers), and secondly the impedance the speaker _sees_ is changing.

    You can believe there will be substantial level changes as you add and
    remove speakers.

    And the changing source impedance means that the low end response will
    change substantially as you turn speakers on and off.

    THIS sort of disaster is why we have 70 volt systems. The whole constant
    voltage concept allows you to avoid all of this stuff.
    --scott
    --
    "C'est un Nagra. C'est suisse, et tres, tres precis."
  13. Archived from groups: rec.audio.pro (More info?)

    "Scott Dorsey" <kludge@panix.com> wrote in message
    news:ceu50o$ra9$1@panix2.panix.com...
    > Frank A <notme@yahoo.com> wrote:
    > >
    > >Just to try to shed some more light on what I'm working with. The
    > >manufacturer of the speaker
    > >distribute/selector(http://www.hacs.com/ab8ss.html) had the following
    char
    > >on their site:
    > >
    > >Resistance impedance matching information:
    > >Number of speakers selected= 1 2 3 4 5 6 7 8
    > >Ohm load seen by amplifier= 8.49 4.98 4.13 3.96 4.05 4.27 4.85
    4.92
    > >% power to speakers= 94 80 64 50 40 31 29 20
    > >max power internal resistors 10 20 30 40 50 60 70 80
    > >max power speakers 156 80 53 40 33 27 29 20
    > >max power from AMP 166 100 83 80 83 87 98
    100
    > >
    > >Since with all 8 speakers the impedence seen by the amp is show at 4.92
    with
    > >a min impedence of 3.96. From some reading I've done I was thinking that
    > >most amps would be able to handle that.
    >
    > This is not a simple switchbox.
    >
    > This is a box that is throwing series resistors on each speaker as you
    > increase the number of speakers on the load. This means that as you
    > add more speakers, first of all the amount of power being thrown away
    > increases (note here that when you have 8 speakers, 80% of the power is
    > being thrown away with the series resistors and only 20% is making it to
    > the speakers), and secondly the impedance the speaker _sees_ is changing.
    >
    > You can believe there will be substantial level changes as you add and
    > remove speakers.
    >
    > And the changing source impedance means that the low end response will
    > change substantially as you turn speakers on and off.
    >
    > THIS sort of disaster is why we have 70 volt systems. The whole constant
    > voltage concept allows you to avoid all of this stuff.
    > --scott
    > --
    > "C'est un Nagra. C'est suisse, et tres, tres precis."

    I'll stop and catch up on my reading after this post... just need to ask one
    more thing. Now that you've seen the box will the 70V system still provide
    the functionality we originally were talking about? Or is there something
    about this box that makes it insufficient for my goals?

    Frank
  14. Archived from groups: rec.audio.pro (More info?)

    Frank A <notme@yahoo.com> wrote:
    >
    >I'll stop and catch up on my reading after this post... just need to ask one
    >more thing. Now that you've seen the box will the 70V system still provide
    >the functionality we originally were talking about? Or is there something
    >about this box that makes it insufficient for my goals?

    Well, it means the sound quality will change as you add and remove speakers,
    and a substantial amount of the amplifier output power is being wasted as
    heat rather than being sent to your speakers. You will not be able to
    control levels individually. If this does not bother you, it's fine. And
    it will probably be much cheaper than good 70V transformers.
    --scott

    --
    "C'est un Nagra. C'est suisse, et tres, tres precis."
  15. Archived from groups: rec.audio.pro (More info?)

    In article <jzrQc.7181$zc4.4773928@news4.srv.hcvlny.cv.net> notme@yahoo.com writes:

    > lets say I
    > buy a 150W amp. I use the 70V transformer on the output of the amp (but
    > before my distribution box) Each speaker would hav e a transform (lets say
    > 10 W) so that it only gets 10 W regardless of if 1 speaker pair is active or
    > all 8? Is that correct?

    Essentially yes.

    > I had a second thought (that might be crazy). Since this system is being
    > controlled by a computer, I was thinking that if I had the same 150W amp,
    > and a bunch of regular speakers (all same Watt) and then had my software
    > alter the volume of the computer (which is the input to the AMP) to control
    > the overall power? E.g. If 1 speaker pair is active computer volume =10% ,
    > 2 speaker = 20%, etc... Is that a crazy / silly / stupid idea?

    It might work with some amplifiers, but if you use common 8 ohm
    speakers and have all of them switched on, you're loading the
    amplifier with 1 ohm. Few amplifiers are happy that way.


    --
    I'm really Mike Rivers (mrivers@d-and-d.com)
    However, until the spam goes away or Hell freezes over,
    lots of IP addresses are blocked from this system. If
    you e-mail me and it bounces, use your secret decoder ring
    and reach me here: double-m-eleven-double-zero at yahoo
  16. Archived from groups: rec.audio.pro (More info?)

    In article <XAwQc.9961$zc4.5609856@news4.srv.hcvlny.cv.net> notme@yahoo.com writes:

    > Just to try to shed some more light on what I'm working with. The
    > manufacturer of the speaker
    > distribute/selector(http://www.hacs.com/ab8ss.html) had the following char
    > on their site:
    >
    > Resistance impedance matching information:
    > Number of speakers selected= 1 2 3 4 5 6 7 8
    > Ohm load seen by amplifier= 8.49 4.98 4.13 3.96 4.05 4.27 4.85 4.92
    > % power to speakers= 94 80 64 50 40 31 29 20

    OK, it's a box for people like you who just want to connect a bunch of
    speakers to an amplifier. It has more than just switches inside. You
    won't harm an amplifier, but as you see, the more speakers, the less
    power to each speaker, so switching in more speakers will change the
    volume of the speakers that are already on.

    This is not appropriate for a 70V system.

    I suppose you could work on your idea of increasing the volume from
    the computer when you switch in more speakers. Better check to see
    what it takes to burn out the internal resistors. It may not be able
    to handle the power you'll have to give it in order to get the same
    volume with several speakers as you do with one.


    --
    I'm really Mike Rivers (mrivers@d-and-d.com)
    However, until the spam goes away or Hell freezes over,
    lots of IP addresses are blocked from this system. If
    you e-mail me and it bounces, use your secret decoder ring
    and reach me here: double-m-eleven-double-zero at yahoo
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