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From: Rupert on 18 Jul 2010 00:50 On Jul 17, 5:43 pm, "The Post Quartermaster" <quartermasterextraordina...(a)postfiftyone.org> wrote: > "Rupert" <foodste...(a)gmail.com> wrote in message > > news:ca82262e-2262-4349-8223-996d839fe684(a)z15g2000prn.googlegroups.com... > On Jul 17, 2:41 pm, "liquidator" <mi...(a)mad.scientist.com> wrote: > > > > > > > "Krooburg Science" <kroob...(a)gmail.com> wrote in message > > >news:b6655c0d-5d42-481a-9cc9-92a6ac196193(a)z34g2000pro.googlegroups.com.... > > On Jul 16, 12:09 pm, "The Post Quartermaster" > > > <quartermasterextraordina...(a)postfiftyone.org> wrote: > > > I've never quite caught on to the Ohms thing. If I am running two > > > speakers (I forget the terminology - series or parallel) in a > > > system > > > in which the speaker cable runs from the power amp to the first > > > speaker, and then another cable runs from that speaker to the > > > second > > > speaker, what must I calculate in order to safely run yet another > > > cable from the second speaker to a third speaker? > > > -- > > > Careful how you respond. I have people! > > > > JC > > > Daisy chaining speakers is a *parallel* connection which is > > electrically the same connection is hooking all the speakers > > directly > > to the amp terminals. The disadvantage to daisy chaining is that > > cable > > resistance is higher and electrical damping is lower since all the > > speakers go through a single cable to the amp. Anyhow, every time > > you > > take two identical speakers (loads) and connect them in parallel to > > the amp by either method, you effectively cut the impedance of the > > load that the amp "sees" in half. So two 8Ù speakers nets a 4Ù > > nominal > > load - nominal meaning average. Speaker impedance varies with > > frequency which can be very important depending on the amp and how > > well it can handle dips in impedance below nominal. Now adding a 3rd > > speaker requires the use of a formula since you're dealing with an > > odd > > number. The formula is Rt = 1 / [ (1/R1) + (1/R2) + (1/R3). I > > suffices > > to say that the load with three 8Ù speakers is ~2.66Ù. If your amp > > channel is rated to handle 2 ohm loads (four 8Ù speakers in parallel > > or two 4 ohm speakers in parallel), then 2.66Ù should work fine. If > > it's rated for 4Ù minimum, don't do it. > > > - K > > > Quick and dirty for the math impaired, if the same just divide the > > original > > impedance by number of speakers...ie 8/2=4 8/3=2.66 8/4=2 > > Thanks for tip Liquid. That does simplify things. > > Rupert > > I don't remember if their set up has a monitor output. But if it does, > wouldn't it work if I ran out of the monitor output into another power > amp out to a couple of outside speakers? I know back in the old days > (I'm pushing 70) we daisy chained power amps a few times. Frankly, I > don't remember that accomplishing anything though. > Sure, you can drive another power amp off of any of the line level signal outputs from a mixer. That has no effect on the "power amplifier" portion of the powered mixer. Unfortunately, the PMP518M has no monitor output or secondary balanced outputs. The only extra outputs are the unbalanced tape outputs or using the "Insert" jack as an unbalanced output. Neither is meant to drive very long signal lines as unbalanced lines are susceptible to picking up noise. So if you use those to drive another amp, it should be in close proximity and running off the same power circuit to avoid ground loops. Keep in mind also that the drive voltage from those outputs may or may not be adequate for professional power amps in terms of getting them to full output. Rupert
From: The Post Quartermaster on 18 Jul 2010 10:03
"Rupert" <foodsteaks(a)gmail.com> wrote in message news:cb826dfa-3c2a-4b92-a945-8f775b24a6c5(a)z34g2000pro.googlegroups.com... On Jul 17, 5:43 pm, "The Post Quartermaster" <quartermasterextraordina...(a)postfiftyone.org> wrote: > "Rupert" <foodste...(a)gmail.com> wrote in message > > news:ca82262e-2262-4349-8223-996d839fe684(a)z15g2000prn.googlegroups.com... > On Jul 17, 2:41 pm, "liquidator" <mi...(a)mad.scientist.com> wrote: > > > > > > > "Krooburg Science" <kroob...(a)gmail.com> wrote in message > > >news:b6655c0d-5d42-481a-9cc9-92a6ac196193(a)z34g2000pro.googlegroups.com... > > On Jul 16, 12:09 pm, "The Post Quartermaster" > > > <quartermasterextraordina...(a)postfiftyone.org> wrote: > > > I've never quite caught on to the Ohms thing. If I am running > > > two > > > speakers (I forget the terminology - series or parallel) in a > > > system > > > in which the speaker cable runs from the power amp to the first > > > speaker, and then another cable runs from that speaker to the > > > second > > > speaker, what must I calculate in order to safely run yet > > > another > > > cable from the second speaker to a third speaker? > > > -- > > > Careful how you respond. I have people! > > > > JC > > > Daisy chaining speakers is a *parallel* connection which is > > electrically the same connection is hooking all the speakers > > directly > > to the amp terminals. The disadvantage to daisy chaining is that > > cable > > resistance is higher and electrical damping is lower since all the > > speakers go through a single cable to the amp. Anyhow, every time > > you > > take two identical speakers (loads) and connect them in parallel > > to > > the amp by either method, you effectively cut the impedance of the > > load that the amp "sees" in half. So two 8� speakers nets a 4� > > nominal > > load - nominal meaning average. Speaker impedance varies with > > frequency which can be very important depending on the amp and how > > well it can handle dips in impedance below nominal. Now adding a > > 3rd > > speaker requires the use of a formula since you're dealing with an > > odd > > number. The formula is Rt = 1 / [ (1/R1) + (1/R2) + (1/R3). I > > suffices > > to say that the load with three 8� speakers is ~2.66�. If your amp > > channel is rated to handle 2 ohm loads (four 8� speakers in > > parallel > > or two 4 ohm speakers in parallel), then 2.66� should work fine. > > If > > it's rated for 4� minimum, don't do it. > > > - K > > > Quick and dirty for the math impaired, if the same just divide the > > original > > impedance by number of speakers...ie 8/2=4 8/3=2.66 8/4=2 > > Thanks for tip Liquid. That does simplify things. > > Rupert > > I don't remember if their set up has a monitor output. But if it > does, > wouldn't it work if I ran out of the monitor output into another > power > amp out to a couple of outside speakers? I know back in the old days > (I'm pushing 70) we daisy chained power amps a few times. Frankly, I > don't remember that accomplishing anything though. > Sure, you can drive another power amp off of any of the line level signal outputs from a mixer. That has no effect on the "power amplifier" portion of the powered mixer. Unfortunately, the PMP518M has no monitor output or secondary balanced outputs. The only extra outputs are the unbalanced tape outputs or using the "Insert" jack as an unbalanced output. Neither is meant to drive very long signal lines as unbalanced lines are susceptible to picking up noise. So if you use those to drive another amp, it should be in close proximity and running off the same power circuit to avoid ground loops. Keep in mind also that the drive voltage from those outputs may or may not be adequate for professional power amps in terms of getting them to full output. Rupert Thanks again. -- Careful how you respond. I have people! JC |