Dolby 5.1 ?

[iwire]

I did a theater where I had to provide the prewiring for the speakers.

To save money I made them multiwire circuits by running one negative for all 5 channels.

 

[TwinCitySparky]

Thanx! Amps I have. A Sunfire Stereo (300w/ch x 2) for the main speakers, and a Sunfire Cinema Grand (200w/ch x 5) for the center, sides, and rears.

Add the stereo powered subs (300w each, built into the main speakers) and that brings the total audio power up to 2200w, and that's a continuous rating.

There's just about nothing this pre/pro doesn't do. The camera input is a neat feature. I was thinking of getting a peep-hole camera for the front door.


If you find yourself in the neighborhood, gimme a call and come watch a movie. (Offer open to any MH member.)

Holy cow 2200 continuous!!. I figured you had some big guns in there.

Now that my youngest is six I can dream about putting together a new system. In a previous life before kids, I was given opportunity to buy some gear from my brother. Main components consisted of a 2 channel Sunfire amp feeding a pair of STAX F-81 electrostatic speakers along with some powered subs. I still remember being just blown away - awestruck hearing for the first time all the hidden sonic details of a Dire Straits CD that I had listened to many times before.

Then one day the speakers suffered a strange event where portions of the wire tracing between the glass panels began to burn up right before my eyes in a bizarre miniature fireworks like fashion. The closest thing that I could quickly power down (the Sunfire) did little to save those wonderful seperatly powered speakers.

At least I had 3 great years of use before that sad "event".

 

[mxslick]

I did a theater where I had to provide the prewiring for the speakers.

To save money I made them multiwire circuits by running one negative for all 5 channels.

And I'll bet you used #12 solid too. :grin:

You're a hoot. :grin:

Holy cow 2200 continuous!!. I figured you had some big guns in there.

Now that my youngest is six I can dream about putting together a new system. In a previous life before kids, I was given opportunity to buy some gear from my brother. Main components consisted of a 2 channel Sunfire amp feeding a pair of STAX F-81 electrostatic speakers along with some powered subs. I still remember being just blown away - awestruck hearing for the first time all the hidden sonic details of a Dire Straits CD that I had listened to many times before.

Then one day the speakers suffered a strange event where portions of the wire tracing between the glass panels began to burn up right before my eyes in a bizarre miniature fireworks like fashion. The closest thing that I could quickly power down (the Sunfire) did little to save those wonderful seperatly powered speakers.

At least I had 3 great years of use before that sad "event".

2200 is nothing these days. The new screening room I put in at UC Irvine which is roughly 35 x 25 feet (90 seats) has over 4,400 watts and dual 18" subs.

In the average size cinema over 10,000 watts is not uncommon, and I have done a few large cinemas with over 25,000 watts of audio power. (Which would burn up iwire's puny wiring attempts.) :grin:

Those electrostatic speakers were indeed magical and had sonic qualities that can't be beat, but as Twin City discovered, they could fail catastrophically and without warning.

 

[LarryFine]

To save money I made them multiwire circuits by running one negative for all 5 channels.

You can actually do that for amplifiers that use chassis as one speaker terminal. I wouldn't do it, but you theoretically could.

Back when I was in high school, I was in the "radio club." We got the school admin's permission to pipe music into the cafeterias during lunchtime, and we even did DJ duties, playing requests, and making announcements.

We ran two conductors from a stereo amp in our room to the three cafeterias, one for each channel, and used the building EGC system as the return for both channels. We actually got decent stereo separation and no hum.

We ran #8 wires for the 'home run', which was about 100', switched to #10 from the first room to the second, and #12 to the third, and for each speaker. We connected two speakers to each channel in each lunchroom.

We paralleled everything, but the wire resistance was enough to present a decent load at the amplifier. We did a DC measurement before we connected to the amp, and found it was high enough to prevent overloading the amp.

 

[iwire]

And I'll bet you used #12 solid too. :grin:

You're a hoot. :grin:

Glad you could see I was joking. :grin:

I did do a theater and we did prewire for the speakers, the spec was 14 AWG stranded.

They installed the speakers early and I could drive a pair behind the screen pretty well with a small 'boom box' I had.

 

[iwire]

You can actually do that for amplifiers that use chassis as one speaker terminal. I wouldn't do it, but you theoretically could.

I bet it would work on most any amps. Each output would be like an SDS correct?

 

[LarryFine]

I bet it would work on most any amps. Each output would be like an SDS correct?

Not necessarily. Most modern solid-state amps, which use bi-polar power supplies, yes, because they use the chassis/power supply ground as a speaker terminal (reference). Or, tube amps, with output transformers.

But, many "mid-fi" stereo and surround receivers use what is called a "hybrid" amp, basically a single-package amp-in-a-chip, and they sometimes are actually bridged amps, so neither output terminal is grounded.

A bridged amp uses two amps (or, amp channels) driven out-of-phase, and the speaker is connected from one + out to the other + out. This doubles the output voltage, which is capable of quadrupling the output power.

That, however, is dependent on whether each amp is capable of doubling its output power into half the load impedance, and that's partially dependent on whether the power supply is capable of handling the current.

 

[mxslick]

Glad you could see I was joking. :grin:

I did do a theater and we did prewire for the speakers, the spec was 14 AWG stranded.

They installed the speakers early and I could drive a pair behind the screen pretty well with a small 'boom box' I had.

Yep I saw your fine sense of humor in it's full glory this time. :grin: Glad we can joke about the hot button issues. :grin:

Just curious, how long were the runs? I usually spec 12 ga for stage speakers and 14ga for the surrounds. On one large house with a long throw it was 10 and 12 respectively.

Modern cinema speakers are highly efficient and you can easily drive them quite loudly with the average boom box. But the old Altec Lansing "Voice Of The Theatre" series speakers (which were designed in the days of low-power tube amps) can be driven very loud with a simple transistor radio powered by a single 9v battery!

Not necessarily. Most modern solid-state amps, which use bi-polar power supplies, yes, because they use the chassis/power supply ground as a speaker terminal (reference). Or, tube amps, with output transformers.

But, many "mid-fi" stereo and surround receivers use what is called a "hybrid" amp, basically a single-package amp-in-a-chip, and they sometimes are actually bridged amps, so neither output terminal is grounded.

A bridged amp uses two amps (or, amp channels) driven out-of-phase, and the speaker is connected from one + out to the other + out. This doubles the output voltage, which is capable of quadrupling the output power.

That, however, is dependent on whether each amp is capable of doubling its output power into half the load impedance, and that's partially dependent on whether the power supply is capable of handling the current.

Larry is correct, with a few caveats. Even some modern amps which may have the speaker minus terminals tied together are sometimes (but rarely) still isolated from ground. So one must be very cautious not to allow any speaker leads to short to ground or allow the minus leads of one amplifier to short to another amp's minus leads.

Another thing in reference to bridge mode operations: Some amplifiers are capable of voltages and currents that make the speaker lines Class 2 or even Class 1 systems and the wiring methods must be done accordingly. Crown made a single amplifier (for large venues like racetracks) that REQUIRED a MINIMUM 8 Guage speaker wire!! It had about 10,000 watts of audio output into a 100v or 70 volt line. EACH amplifier had to have a 30amp 3-phase 208/240 volt circuit. I think I still have the original brochure somewhere.

 

[LarryFine]

Even some modern amps which may have the speaker minus terminals tied together are sometimes (but rarely) still isolated from ground. So one must be very cautious not to allow any speaker leads to short to ground or allow the minus leads of one amplifier to short to another amp's minus leads.

Agreed. It would have been more accurate for me to say that the amp negatives either should be, or must be capable of being, tied together, but not necessaril grounded.

In response to Bob's question about audio outputs being like SDS's: in theory, any two conductors, one from each source, may be tied together as long as no other ones are.

In audio, the chassis ground is a lot like the power EGC system, and the signal ground is a lot like the power system's grounded conductor: they're not always the same thing.

 

[ItsHot]

Sure! Here ya' go:

:grin:​

Set myself up for these Kliens!! Thanks Larry!:grin:

 

[iwire]

In response to Bob's question about audio outputs being like SDS's: in theory, any two conductors, one from each source, may be tied together as long as no other ones are..

Pretty much what I figured, I am aware that working is not the same thing as correct.

 

[Smart $]

...
Larry is correct, with a few caveats. Even some modern amps which may have the speaker minus terminals tied together are sometimes (but rarely) still isolated from ground. So one must be very cautious not to allow any speaker leads to short to ground or allow the minus leads of one amplifier to short to another amp's minus leads.

Agreed. It would have been more accurate for me to say that the amp negatives either should be, or must be capable of being, tied together, but not necessaril grounded.

Caution advised. Many modern bridgeable amplifiers internally tie together the positive of one output to the negative of the other (others require an outboard jumper). One output is inverted as are its polarity terminal markings. This is how the output wattage is doubled into the same impedance.

In response to Bob's question about audio outputs being like SDS's: in theory, any two conductors, one from each source, may be tied together as long as no other ones are.

In audio, the chassis ground is a lot like the power EGC system, and the signal ground is a lot like the power system's grounded conductor: they're not always the same thing.

While I agree, I recommend not wiring as such. Modern amplifiers also have circuit protection built in. Using common wires between amplifiers may defeat this feature, or cause two amps to shutdown when only one driver circuit is faulting. Not 100% certain about this, but all the more reason not to wire as such.

 

[Smart $]

...

Another thing in reference to bridge mode operations: Some amplifiers are capable of voltages and currents that make the speaker lines Class 2 or even Class 1 systems and the wiring methods must be done accordingly. Crown made a single amplifier (for large venues like racetracks) that REQUIRED a MINIMUM 8 Guage speaker wire!! It had about 10,000 watts of audio output into a 100v or 70 volt line. EACH amplifier had to have a 30amp 3-phase 208/240 volt circuit. I think I still have the original brochure somewhere.

Crown was a top name in power sound reinforcement amps... back in the day I was an extracurricular audio tech for live bands. I seem to recall that puppy

Today, I only use my audio tech knowledge for personal enjoyment. I have a 10kW-rated (continuous) 2-channel subwoofer amplifier in my personal van. Being that it is battery powered (~12VDC), I connected it using 4/0 welding cable... undersized for full power, but I have no desire to push it to the max

 

[LarryFine]

Caution advised. Many modern bridgeable amplifiers internally tie together the positive of one output to the negative of the other (others require an outboard jumper). One output is inverted as are its polarity terminal markings. This is how the output wattage is doubled into the same impedance.

The bridging I'm familiar with is where you take a pair of amplifier channels (either mono amps with speaker neg's tied together, or a stereo amp in which both channels use chassis ground as speaker neg's), and use a phase splitter to drive one channel with an inverted signal.

The speaker is driven from one speaker pos out to the other. The total output voltage doubles, which doubles the output current, resulting in quadrupling of total output power. This requires each of the amps to be capable of doubling power into half the load impedance.

The circuit you show is effectively the same thing, without having to invert one amp's input, and it seems should also be capable of quadrupling the output power. I don't see is how one channel's pos can be tied to the other's neg, unless one channel operates inverted already.

Maybe it doesn't quadruple power because the amps and/or their power supply just don't have the capacity. I once made a 25a bipolar supply for four mono amps I bridged into two channels. It's not just about volune, it's about the amp's ability to control speaker cone motion.

While I agree, I recommend not wiring as such. Modern amplifiers also have circuits built in. Using common wires between amplifiers may defeat this feature, or cause two amps to shutdown when only one driver circuit is faulting. Not 100% certain about this, but all the more reason not to wire as such.

Again, the amps I've used did use chassis ground as signal ground. The speaker neg's ran directly from the point the transformer's CT and filter caps connected together, and to the chassis. I know because I built the amps from kits. (Southwest Technical Products Corp.)

 

[LarryFine]

I have a 10kW-rated (continuous) 2-channel subwoofer amplifier in my personal van.

Wow. My big inverter is only roll rated for 2500w cont.

... I have no desire to push it to the max

But, if you ever get stuck in sand, you can vibrate your way out.

 

[Smart $]

The bridging I'm familiar with is where you take a pair of amplifier channels (either mono amps with speaker neg's tied together, or a stereo amp in which both channels use chassis ground as speaker neg's), and use a phase splitter to drive one channel with an inverted signal.

The speaker is driven from one speaker pos out to the other. The total output voltage doubles, which doubles the output current, resulting in quadrupling of total output power. This requires each of the amps to be capable of doubling power into half the load impedance.

The circuit you show is effectively the same thing, without having to invert one amp's input, and it seems should also be capable of quadrupling the output power. I don't see is how one channel's pos can be tied to the other's neg, unless one channel operates inverted already.

Maybe it doesn't quadruple power because the amps and/or their power supply just don't have the capacity. I once made a 25a bipolar supply for four mono amps I bridged into two channels. It's not just about volune, it's about the amp's ability to control speaker cone motion.



Again, the amps I've used did use chassis ground as signal ground. The speaker neg's ran directly from the point the transformer's CT and filter caps connected together, and to the chassis. I know because I built the amps from kits. (Southwest Technical Products Corp.)

I did say one amps output is inverted, as are its terminals.

I am not disputing your claims. In fact I agree with them... for certain equipment. However, today there are just to many configurations to say what you are saying is true for most configurations

Yes, the power is quadrupled when bridged into the same impedance value load. I was referring to keeping the load impedance the same on the amps. For example, 400W/channel ? 2 into 4-ohm loads is the same as 800W/channel ? 1 into an 8-ohm load (...each amp section still sees a load of 4 ohms).

 

[LarryFine]

I was referring to keeping the load impedance the same on the amps. For example, 400W/channel ? 2 into 4-ohm loads is the same as 800W/channel ? 1 into an 8-ohm load (...each amp section still sees a load of 4 ohms).

Ah, you mean the same impedance for each amp channel. My perspective is from a given pair of speakers you want more oomph from. You can't change the impedance of one speaker, so you drive it harder.

Way back then, my speakers were Rectilinear III's, which were notoriously inefficient for cone-based speakers. They were rated at 100w cont. each, a bit high for those days. Bridging was cheaper.

This was back when my interest in the hobby outweighed my ability to afford it. (Not that it's so different these days, either. :roll I built what I couldn't afford, and this was experimentation, anyway.

 

[Smart $]

Ah, you mean the same impedance for each amp channel. My perspective is from a given pair of speakers you want more oomph from. You can't change the impedance of one speaker, so you drive it harder.

Way back then, my speakers were Rectilinear III's, which were notoriously inefficient for cone-based speakers. They were rated at 100w cont. each, a bit high for those days. Bridging was cheaper.

This was back when my interest in the hobby outweighed my ability to afford it. (Not that it's so different these days, either. :roll I built what I couldn't afford, and this was experimentation, anyway.

In many cases, bridging is still cheaper

I never built an [power audio-grade] amplifier for myself, but I once helped a friend put together a Heath kit receiver.

 

[Smart $]

Wow. My big inverter is only roll rated for 2500w cont.

But, if you ever get stuck in sand, you can vibrate your way out.

Perhaps... but I'd have to be pretty desperate... Replacing all the windows after I got unstuck would be more expensive than calling a tow truck

 

[LarryFine]

What??????