? about speaker wiring

[radiorickm]

Ok...i just rewired my entire PA system, bi-amping it. tired of soldering now!.

anyway, i'm sure i did this right....but at 4:00 in the morning, thought i better get one of the ee types to check that i ain't going to blow somehting up


I have a 3 conductor wire running to my speakers. So, insted of running separate cables for the low and hi enclosures, i used the 3 conductor wire.

i have the 2 commons/negatives together, and a + for the hi, and a + for the low.

running the negatives together will not hurt anything will it? after all, they are probably connected together in the amp eventually anyways? right?

(ps....it's plugged in and working.....no smoke yet)

 

[Farview]

I may be wrong, but I don't think that the - is ground on a speaker connection. I'm assuming that you are using a separate amp for both high and low.

I don't think this is a good idea.

 

[radiorickm]

hmmm.

you got me thinking

now my head hurts.


anyways....

i just checked continuity. On the amps, the two commons (black connectors) are connected to each other, and they do have a path to ground. so? think i should be good

if any one else has anything im still open.

and thanks farview for answering

 

[boingoman]

Something sounds very wrong about what you are doing.

 

[radiorickm]

interesting....

ok. right up front. i am not trying to start an argument. I am trying to start a discussion to learn something here.

I have a fair knowledge of electric principle

lets say we are builing a balanced cable, to hook a mixer up to an (well, anything really)

we use a trs to trs cable, to complete the balanced circuit. great.

what is the trs cable?

it has a + Tip, - ring, and ground/shield to the sleeve so far so good, right?

but if you think about it, the ( - ring) side isn't really a minus or negative voltage, it is a positive voltage fed 180* out of phase to the + voltage.
it uses a common ground for the return path of the 2 voltages. But even if it were two voltages, it is still using the SAME common as a return path

Same thing if you were to actually use the cable as a stereo send. You have two, separate +'s (a left and a right) and a common ground path for the return. This is exactly how headphone (speakers) are wired right?

If you really think about it, that is how all 220V single phase is wired. (2) 110 positives and (1) common.

I think electically, i am pretty safe. I know it sounds weird.

I think what I am more concerned about is the interaction of the electo magnetic field having the 2 so close together in a common cable.

is there going to be any phase cancelling or just plain degredation of the signal having the physical wires so close together?

like i said, i am trying to learn here so if anyone has any ideas....chime in!

thanks

 

[Farview]

The only thing that makes me think this is wierd is if you bridge an amp, isn't 1 side of the amp handling the positive and the other the negative? If it is then the pos of the speaker cable would be pushing pos and the neg would be pushing neg. So would this still be a common?

I really don't know, these are just the random thoughts that keep me from doing anything really cool.

 

[boingoman]

It's just that you aren't bi-amping. Bi-amping is splitting the signal and using one amp or amp channel to drive your highs and a seperate amp or amp channel to drive your lows. What you are doing is sending the same full-range signal to your top and sub boxes. This will rob you of the biggest advantages of a bi-amped system, the ability to send lots more power to the subs and control their output relative to the tops.

There are some basic problems with your approach. First, the high and low boxes tend to overlap in freq response. If your subs go up to 300hz and your tops go down to 80 hz, you get that 80-300hz section overlap. You end up equing the hell out of that region, and lose anything that cancels out due to time delays, unless all your drivers are time-aligned, like JBL SR-X series boxes.

The other problem is power. The low band requires a lot more power to achieve the same SPL. Since you can't control the level to each band, the solution is to run subs that are lower impedance. If you run a 4-ohm and an 8-ohm box on the same channel, the 4-ohm box will get more power. A compromise at best, since all you can say is that the subs will get more power.This also drops the load to under four ohms. Your amp needs to be able to do this.
If subs and tops are both 8-ohms, they split the juice evenly. You will still get more low end, but not a significant amount. It will also be very muddy, and the subs lose some power putting out freqs that are covered by your tops. Correcting this kind of set-up with eq is just about impossible.

If you don't want to get a crossover, run your subs on one channel, and your tops on the other. This gives you control over the level of your subs with the gain control on your amp. You still have the problems of overlapping bands, but at least you have some control.
If you want to run stereo, a truly bi-amped system requires 2 amps, or one amp with four channels.

 

[radiorickm]

ok. my bad

sorry, i didn't list all of my equipment....

I am running a crossover. (in stereo)

i also have 2 stereo amps, 1 dedicated of course to hi's, and the larger of the 2 dedicated to the lows.

My subs are rated to 500Hz, and my tops come down to about 80. I disabled my graphic EQ and just listened to the system as i tuned the cross over point. Came out that about 200Hz "SOUNDED" the best, so i used that as a crossover point.

Everything seems pretty balaced, sound wise. I didn't have to add any gain on the crossover stages to balance things out, so everything is setting at "0" and is pretty happy.

i built up all of the interconnecting cables, so i was very careful about the phasing, and kept everything in order.

thanks for all of the help guys.

I guess i ended up with a true 4 way system. My tops have a passive crossover network in them, so i fed them everything above 200. The tops have a 12" driver, 10" midrange, and 3-2x2 horn tweeters. turns out it sounds decent. But i did make one mistake, my "LO" amp probably isn't near big enough for the sound i want. So, i see a Peavey or QSC amp in my near future.

 

[radiorickm]

oh yeah, one more thing....

I went to the trouble of BUILDING all of my own cords for this project.....
Now, my local music store has PROEL connectors. They seem to be very good, nice quality and everything...

The XLR's were marked @ $5.95 ea.

That comes out to about $14.00 for a short cable, plus it took me hours to solder them all up.

Now.....somebody tell me why i did the right thing insted of just spending 10 minutes, and going to Wally world and buying the damn cords for $ 9.99?

just ranting.

really thanks to everyone who answered my questions.

 

[Sonixx]

What guage wire?

How many watts per channel?

How long are the runs?

Since you are using a common return path, the guage of the return needs to be able to handle the sum of the two supply currents. One issue with the common return path is the amp/speaker impedance will be affected to some degree due to the cable length... the longer the cable to more affect.

A better option is to use four conductor (probably 12 guage stranded) wire with Neutrik Speakon connectors on each end. Then make adaptors as necessary to accommodate the speaker connector if they are not NTK Speakon.

 

[radiorickm]

hi sonixx

sorry i din't answer sooner......graveyard shift!

right now, i am running 14ga wire into 50' lengths

I ordered these amps because i have had good luck with the brand in the past, and i knew if they didn't work out for the PA i would still use them in the studio as pretty clean amps for the monitors

the top amp is 100 W per channel, the bottom is 150 W per channel so right noW i'm not pushing a lot.

but, i dont have enough low end, so i will be adding in probably a cs800 on the low side at least.

but even then at 400 watts per channel, i think the line will be ok.

i do a one man band thing and, i guess the system sounds REALLY good as is, but should i (get volunteered) to do DJ stuff, i would like a little more low end.

thanks for the reply and the info

 

[TexRoadkill]

Are you using XLR cable as speaker cable? Stop now before you fry your amps. Only use non-sheilded copper wire. It's also much cheaper.

 

[the Ozlee]

I would not have done it this way. First unless I am mistaken you are dealing with DC volatge, the negative is not out of phase. Also all crossover points are affected by resistance and the size and length of wire can significantly effect the DC voltage ( the amount of power that actually reaches the speaker ).

Personally I don't using anything less than 12 gauge multistrand oxygen free speaker cable from my amps to each cabinet. I use unshielded 2 wire cables to each cabinet and have not had any problems caused by RF. However a shielded cable in theroy is a better way to go (the shield is not connected it is just a sheild). I worked with a professional touring sound company and this is the way they did it.

Ozlee

 

[Sonixx]

Are you using XLR cable as speaker cable? Stop now before you fry your amps. Only use non-sheilded copper wire. It's also much cheaper.

No... radiorickm stated he is using 14ga

 

[Sonixx]

... First unless I am mistaken you are dealing with DC volatge...

Are you serious...

Personally I don't using anything less than 12 gauge multistrand oxygen free speaker cable from my amps to each cabinet. I use unshielded 2 wire cables to each cabinet and have not had any problems caused by RF.

For this use, oxygen free is a waste of money...

However a shielded cable in theroy is a better way to go (the shield is not connected it is just a sheild).

Not for speakers...

Yes... shielded from the board to the amp or crossover. The shield can be left open on one end. The open ends should be connected to the same piece of equipment.

 

[the Ozlee]

Sonixx, where did you get your electrical engineering degree? I said "unless I was mistaken" I thought it was DC current (the output from the power amp to the speaker) please correct me if I'm wrong. Don't confuse ground loops with shielding, I haven't. I also said that this was theory (something I read somewhere, I probably picked this up from an audiophile purist) I also said my personal experience did not bare this out. Having said that, when you go to eliminating noise for a clean quite system in a studio, I think this is a valid consideration. I also said that I use oxygen free cables, I didn't say that anyone else should and I don't, at this point, think they are a waste of money. I have a set that are not oxygen free that are 12 gauge enclosed in a clear protective covering that have turned green. The others have not. Since you probably know more than me maybe you could explain how voltage or current is transmitted through a multistrand cable and how oxidation would or would not effect it.

My intention was to share my experience, not establish myself as an authority, there are probably plenty of people around here that can do that better than me anyway. I only hope that the three wire system works out. From what I have read so far no one has really said that this is a good way to go with any confidence.

It was just my opinion, Ozlee

 

[Soundbyte]

First of all your wiring method, while being unorthodox, will not harm your equipment and will work. What you are doing is bootstrapping the ground terminals of your amps together. Some audiophiles will run a signal through a X-over and into multiple amps then bootstrap the amps outputs together before driving a single set of passive high end cabinets. In those cases there is something to be gained in doing it this way. In this case all you are doing is saving the cost of a wire and with 14Ga cable running 50', you are not doing your system any favors either.

Ozlee, you are mistaken. The output of a poweramp is AC. If it were DC the speakercones would only move through half of their full excursion.

 

[wilkee]

As long as both of your amps negative speaker outputs are at ground potential (which is normal) then you will not do any harm.

As you were rewiring why did you not use 4 pole neutriks which are designed for this very job and would have enabled you to use proper 4 core speaker cable?

 

[Sonixx]

Sonixx, where did you get your electrical engineering degree?

Electrical & Computer Engineering, Clemson University, 1981

 

[radiorickm]

reply

As you were rewiring why did you not use 4 pole neutriks which are designed for this very job and would have enabled you to use proper 4 core speaker cable?

i guess there are several "excuses" rather than good reasons.

#1 it was an effort to clean up a stage, for my performances (less wires)
#2 all of my equipment is either 1/4 or bananna. I come from a RF background and we basically assume we are going to loose 1 db per connector/adapter and i guess the signal loss thing kind sticks in my mind.
#3 i live very long ways from a real music store as you guys know them, so i end up paying a LOT of freight. SOmetimes i just settle for doing it the easy way or with what i can get a hold of.
#4 i have never used, or even heard of this particular one) and have no experience with the neutriks and would have to have made at least 8 adapters anyway.
#5 budget consideration, already had and was using the existing cable

i now have some better suggestions which I thank you all very much for.