EMUSIC-L Digest Volume 28, Number 2 This issue's topics: Speaker Cables & Noise & Quadraverbs (14 messages) Your EMUSIC-D moderator is Joe McMahon. Please send articles to emusic-L@auvm.american.edu (or EMUSIC-L@AUVM.BITNET). Administrative mail should be directed to xrjdm@scfvm.nasa.gov. Digests will be distributed semi-monthly to monthly. For faster response to questions, subscribe to EMUSIC-L@AUVM.BITNET (or emusic-l@auvm.american.edu). The EMUSIC-L discussion group can alo be accessed via bit.listserv.emusic-l on Usenet. Subscribers to this list may send articles to EMUSIC-D@AUVM.BITNET (or emusic-d@auvm.american.edu); they will be reviewed and forwarded to EMUSIC-L. Back issues are available from xrjdm@scfvm.gsfc.nasa.gov. This is a manual operation, so requests for things like "all back issues" will take a long time. ------------------------------ Date: Fri, 3 May 91 10:51:57 CDT From: Frank Bello Subject: Speaker Cables & Noise This is a question for you experts in audio. How important is the quality of the connectors & cables within the speaker system? I just got a pair of a Peavey HKS-12 speakers for my home keyboard setup, and I'm getting some disturbing hiss noise, specially when I boost the treble using the HKS's built in EQ. Before I get mad at Peavey I want to check how badly a pair of "common-quality" speaker cables can produce this effect. Then I'll decide on getting new pro-cables, or exchanging the HKSs for something better. Any comments/help/feedback/roumors/notes/tips ? Thanks everyone in advance. Frank. UCS_FNB@SHSU ------------------------------ Date: Fri, 3 May 91 13:20:23 EDT From: Jeffrey R Kell Subject: Re: Speaker Cables & Noise Speaker cables/connectors don't contribute much as long as they make contact (and not with each other!). Low-quality cables might heat up a bit or not deliver full power, but they won't affect sound quality. I suggest you check your AUDIO cables and connectors, your mixer, and other things. Speaker cables have practically zilch to do with that. As for the EQ in the speaker itself, it is most likely passive (hard to be much else without power, eh?). You could be picking up a bit of hiss from the EQ unit itself, but again, not the cables/connectors. /Jeff/ ------------------------------ Date: Fri, 3 May 91 14:30:00 EDT From: "William R(ay) Brohinsky" Subject: Re: Speaker Cables & Noise I've had very little problem with speaker cables. Never have I seen anything after the last active amplification stage create hiss. Hiss is high-freq noise (usually--it depends on what you're actually hearing and what you call hi-freq 8^), and results from a number of sources in audio amps: Transistors can be very noisy. Carbon Comp resistors are great noise producers, especially old ones. Any noise generators will be more obnoxious, the further from the final stage of amplification they are, simply because the noise will have that many more levels of increase before it gets to the speaker. A good way to isolate the noise maker is to define a point in your system that you can hook everything to, one at a time. Then, set the gain up fairly high at that point, and hook each preamp, effect, keyboard, etc. to that point, one at a time. Turn up the output level of the device, either to the point you usually use it, or better still, to mid-point. Try to be consistant. (note: for preamps and effects, short the inputs or turn input attenuators to minimum!) Once you've found the noise generators, you have a few things you can do about it: a) ensure that they are close to the poweramp. ie, if you have a keyboard, two effects boxes, a mixer-preamp, and a power amp, and one effects box hisses, consider putting it after the preamp. This way, its noise will not be increased by the preamp. b)set input attenuators as high as possible without distortion, and keep outputs low. This reduces internal amplification of noise, and keeps the (signal+noise)/noise ratio high. If you start with a weak signal and strong noise, all is lost! c) consider adding eq to your system to reduce the bands where hiss is worst. This costs in flatness (you'll attenuate desirable harmonic signal with undesirable noise), but may be your only hope. As for speaker cables, bad ones can limit high and low frequency response. (gee, maybe what you need are really BAD cables?) And the EQ in the speaker is mostlikely passive, as /Jeff/ said. You can knock down the hiss at the speaker with that, and pump it for the signals at the mixer (if it has EQ), but you can end up with real bad compromises that way. I had this kind of problem with my system after adding some effects. I have a noisy Quadraverb, which I will get fixed some day... Let's do it this way: I have a Randall 125W/side stereo amp. I feed it with the output of a Boss 8-channel mixer, through a DAK/BSR graphic equalizer (the one with the spectrum analyzer). Into this goes a few microphones (directly) and the output of the Quadraverb. The inputs to the QV are the stereo channels from an Alesis MicroLimiter, which is fed from two guitars, one electric and one acoustic with a piezo mic stuck in the hole. The MicroLimiter used to come after the QV, but I was having troubles with distortion at the QV's input, so I moved it to the front of the QV. After resetting all the controls, I found that my QV `blank' patch (50% input signal, no effects) was much quieter than the effects patches. I use this when I want the acoustic to sound like an acoustic, but that's another story... I'd been compressing the output of the QV rather severly, which is why I hadn't noticed this before. Turning up the mix to 75% in the QV helped match this, but also really increased the noise it made. I tried to live with this, (I use it in church during services, playing in a small worship band: bass, piano, congas, voices, and me) by putting a very nice stereo Yamaha volume pedal in the string between the EQ and the power amp. When I wasn't playing, I could shut up the whole system. Lazy. Very lazy. It got me into trouble this last Sunday, when we had to go a capella---I had to keep the pedal on for the voices, but the QV noise was intolerable. So I gave up, and re-set the system. By maximizing the input at the QV for the acoustic's output, then resetting the electric output to match, I was able to knock down the QV output by about half. Again, at the Boss, I upped the attenuator about 6dB, and I could reduce the Boss output (another noise maker) a bit. That reduced the noise to the level of the ceiling fans. If I need to, I can up the electric guitar volume a bit more (I left some headroom on the QV!) and pull the overall post-EQ mix down a little with the pedals, and we can get by without the fans on. So fool with your settings, keeping in mind that what comes in should be big, so the local noise needn't get bigger. raybro ------------------------------ Date: Fri, 3 May 91 15:24:48 EDT From: Coup D'Etat Subject: Re: Speaker Cables & Noise The quality of your connectors and the cable is very important in the quality of the sound produced by a speaker system. The most important aspect of a speaker cable is the gauge. I'm not sure, what the pros recomend, but I know that the speaker cable has to deal with a lot of current, so the bigger the gauge the better. Also important is the quality of the connector. It should be an airtight fit and with the type of metals that a good connexion is possible. The pros recommend gold, but copper will do. Insolation for speaker cable is not that important as the signal in a speaker cable is quite high (somewhere in the neighborhood of several amps). -Jeff ------------------------------ Date: Fri, 3 May 91 16:13:00 EDT From: "William R(ay) Brohinsky" Subject: Re: Speaker Cables & Noise >The quality of your connectors and the cable is very important in the >quality of the sound produced by a speaker system. note that poor quality in speaker cables will subtract from the sound, not add to it. Even if the speaker cables/connections could generate noise, it wouldn't be large enough to be heard on the speakers. That requires amplification, so look for hiss before the power amp. If you are operating a 100W speaker with a continuous 100W signal (a sine wave, 'cause the equations get worse for complex signals, or the equations get easier, but the damage to the speaker gets worse!) you can expect (at a nominal 8-ohm impedance, which is another spurious point, and for a 50-volt max rms level) to see about 2 amps in the cables. If you have to drive these speakers through 100-foot cables with .01ohm/foot impedance, you'll be adding another ohm in each direction. If you've really maxed out the power supply, your speaker output level will drop, because of the power being lost in the cables. If you have more headroom, you're total power consumption will increase by about 25%. These numbers are all spurious, and only for illustration's sake. I don't know what the specific resistance would be (lessee, Belden's charts say that 16-guage stranded, tinned bare wire has 4ohms/meter at a stranding [let's use 19/29 @16guage: 4.27ohms/meter] and 18guage stranded at 19/30 is 5.75 ohms per meter.24guage, 19/36 is up to 21ohms/meter.) and the impedance of a speaker is rated at 8ohms at 10000hz, and varies wildly for all other frequencies. Also, there's no indication of how much of that impedance is resistive and how much is reactive, so it's harder to figure out the exact losses. Like I said: for illustration's sake. your mileage will vary! Any way, 16 guage is what I'd consider a minimum for a gig: Ok for in the home. 12 is Much better (averages 1.5ohm/meter), but with a weight factor of around 20lbs/meter (how's that for disregard for mixing units?) it's kinda boring to drag around... As for connections, the good old 1/4-inch plug is a disaster, even though it seems to be fairly standard. If you're driving 1000 watts through each cable, you can get hot spots that cause increased corrosion, which causes increased resistance, which causes increased loss. The springs in the jacks are also easy to weaken; normal useage will do it in about two months. The best kind of connectors are screw-driven brass pincers: they look like mini-thumb-screws. Next best are the spring-driven toothy clamps in some amps. You'll find small ones on almost all home stereos. None of this addresses the hiss problem. See earlier postings. raybro ------------------------------ Date: Sun, 5 May 91 13:43:33 BST From: "Benjamin M. J. Ellis :->" Subject: Re: Speaker Cables & Noise Jeff, I used to think cables didn'T make any odds to the sound, but they make an AWFUL lot of difference, as I found out when I did some tests. Having said that, its not worth spending a fortune on cables! While a bad lead may not directly cause hiss, if it gives a large signal loss, it will mean you turn up the amp, hence raise the noise floor. For audio: use nice thick noiseless cable, of appropriate rating (don'T use UHF cable or thin Tandy ****), for speaker wires, use nice thick copper CABLE, NOT screened wires, use the figure 8 type stuff, coax affects the bandwidth! Also, good connectors are important, try to avoid plastic plugs like the plague, metal shield connectors properly soldered are best (with strain reliefs as well).. ...right sorry, off my soap box, its sunday, I must be felling the need to preach 8-) -Benjamin. UKC England. ------------------------------ Date: Fri, 3 May 91 10:52:28 HST From: Mike 'IR' Ressler Subject: Re: Speaker Cables & Noise (well, Quadraverbs) Raybro says: > I had this kind of problem with my system after adding some effects. > I have a noisy Quadraverb, which I will get fixed some day... [...] > The MicroLimiter used to come after the QV, but I was having troubles > with distortion at the QV's input, so I moved it to the front of the QV. > After resetting all the controls, I found that my QV `blank' patch > (50% input signal, no effects) was much quieter than the effects > patches. I use this when I want the acoustic to sound like an acoustic, > but that's another story... [...] > So fool with your settings, keeping in mind that what comes in should be > big, so the local noise needn't get bigger. Did you fool with ALL your QV settings? The QV is well known for its infamous noise "non-problem". Make sure you've upped all the levels on the mix page and cut out the dry signal completely (I think that's the right direction - I need to go home to check). I substantially reduced the QV's noise just by setting to levels to something more sane than the factory presets. There's one or two sentences in the manual (not very informative) on how to set the levels for use with a mixer. It seems that Alesis assumed you were going to use the QV bare or something ... Mike Ressler ------------------------------ Date: Sun, 5 May 91 22:26:43 CST From: Frank Bello Subject: Thank's Speakers/cables/noise I usually thank personally everyone who post an answer, but this time there are too many, so please accept this global message in this ocassion. Thanks. In regard to the noise problem, My main source of noise is definitively my mixer that I'll get the rid of it as soon as I can. However, the HKSs's EQs, create some noise. Disconnecting everything from the speaker, and boosting the power to the max, if I hear an acceptable hiss, but if I set the EQ treble or midrange to the max, the hiss turns into a HISSSSS which is everything but acceptable. I'll see how the system will perform wit a good mixer and EQ. By the way... the commments about the FX units were kind of interesting, do you owners of Alesis Midiberbs III can tell me how noisy is this unit?, I'm thinking on getting one. Thanks again to everyone Frank. UCS_FNB@SHSU ------------------------------ Date: Mon, 6 May 91 11:21:48 BST From: Nick Rothwell Subject: Re: Speaker Cables & Noise >The quality of your connectors and the cable is very important in the >quality of the sound produced by a speaker system. ...and all this time I've just been using cheap bell-wire. I do, however, use top-quality cable and (metal) connectors for MIDI and audio since the signal levels are much smaller and the cables are in close proximity to each other and the mains/power supplies. Nick. ------------------------------ Date: Mon, 6 May 91 09:17:00 EDT From: "William R(ay) Brohinsky" Subject: Re: Speaker Cables & Noise (well, Quadraverbs) Mike Ressler, The Boss effects loop is too noisy to use, so I have to have some dry signal in the mix. Such is life. If you have any more in-depth info on the non-problem, such as messages, files, pointers to articles, I'd be very happy to hear about it! `seems that Alesis assumed you were going to use the QV bare or something...' Try as I might, I can't get this phrase to parse. What is `using the QV bare' supposed to represent? (Maybe it's studio gig jargon---I havent' haven't been in studio...) raybro ------------------------------ Date: Mon, 6 May 91 09:35:00 EDT From: "William R(ay) Brohinsky" Subject: Re: Speaker Cables & Noise Nick reminded me of anothyer caveat: Some time ago, we were running a 100-foot 12-input snake. I'd have thought that was enough, since we were running 5 voices, a mike for a violin, a bass guitar, and three acoustics. Then somebody decided that we just had to do weddings, and that it would be good to have Rusty (head ego) operate the tapes from the stage. He'd done Yeoman duty as a DJ when he was in the Army band, and was very good at it. The only lines left were the monitor lines, of which there were four. Two brought monitor outs from the board to a distribution amp on the stage, and the other two sat there looking real useful. I should note that this snake had two speaker lines built into it. We were in a hurry, so we ran the tape machine into monitor 3 and 4, and hooked the other end to the line-ins on the mixer board. The squeals were horrendous. The best reason we could ever figure out (not wanting to autopsy a snake that wasn't dead yet...) was that the monitor lines were not the same quality as the other line-level lines in the snake, and/or were run right next to the speaker lines. When we went to heavy duty (16gauge twinwire, jacketed to look like coax, with soldered metal connectors, unfortunately 1/4in) speaker cables and ran them outside the snake shield (but right next to the snake cable) the problem dissapeared. Musta been feedback from the speaker lines in the snake to the monitor lines. I'll never do that again... raybro ------------------------------ Date: Mon, 6 May 91 09:27:39 EDT From: Jeffrey R Kell Subject: Re: Speaker Cables & Noise A postscript to raybro's suggestions in regard to attenuation... Try hooking everything up with all attenuation at max and faders at minimum (ie, max attenuation, min amplification). Turn the system on and set the power amp WIDE OPEN. It should be relatively quiet and clean, if not you are going to have problems (or you have a cheap amp!). Now you can work your way backwards briefly cranking each device in turn up and back down listening for hiss. If something has a bad/cheap/noisy amp section, it will give you the hissing noise, and you want to minimize any gain you obtain from that device. Once you finish this, start at the other end. Get your instruments up to at least midpoint (after adjusting attenuation to just avoid clipping). Try to keep a hot signal with a minimum of amplification; if its too hot use attenuation, if too low use a 'clean' amplification and avoid making up for it with one of the noisy sources found above. When you finish, you should end up running relatively hot until the last stage or two, then attenuate back down to compensate for the open amps (but of course leave some leeway in the mains faders). /Jeff/ ------------------------------ Date: Mon, 6 May 91 10:04:00 EDT From: "William R(ay) Brohinsky" Subject: Re: Speaker Cables & Noise another thought on noisey amps: If you have low, midrange, and hi eq controls on an amp or mixer, you will see the least effect on noise (of the hiss variety) with variation of the bass control. The mids and hi's will affect the noise more and a lot respectively. However, some of this comes from the fact that hiss noise is largely a mid and hi-freq phenomenon. Buzzes and hums tend to be lowfreq. However, if you have a clean signal coming into a fairly nice amp, and you have eq'd the system flat, turning up the highs or mids will usually up the noise level simply because you are amplifying the area where the noise is. It is interesting to note that music tends to have a 1/f characteristic: the higher you go, the farther apart (linearly speaking) the componants are and the less power they will have. Noise (gaussian noise, that is, where all frequencies are present at a constant level, regardless of frequency, also called `white' noise) doesn't have this characteristic: by definition, the frequency distance between componants is constant regardless of frequency. Pink or `colored' noise is less of a problem, because the level of the componants drops with frequency, but the distance between componants is constant still, meaning that the ratio of signal to noise from a band of low frequencies to a band of high frequencies will be decreasing. The higher the freqs, the more effect noise will have. Since you accrue noise at each level of amplification, it is generally best to `weight' your highs at the generator-end of the string. If you have a guitar, and the you have a tone control, set it more towards the high end, and compensate by cutting the highs near the power amp. Result: you get more high-end signal, and less noise. You also have to understand how each effect, preamp, signal conditioner, and transformer effects your signal. It is probably well known that the tone control affects the sound of the guitar in ways that are very hard to duplicate with the lo/mid/hi EQ controls on a mixing board! Find compromises that get the most sound to your speakers without growing the most noise. Another place for noise to get in is in effects loops. Why people don't spend more time on making effects-loops in mixers quieter, I don't know... What happens, usually, is that you patch an effect/many effects into this loop, which may be mono or stereo. The effects are set for max in without clipping, and reasonable outs. The input of the mixer's effects loop runs full bore, with a fader to attenuate it at the busses. Then, you use another fader (potentiometer, really) to add some dry signal to the input of the effects loop. The problems I've seen, especially with mixers we can afford, have been this: the outputs from each channel to the effects buss are noisy. The more dry signal you send from one channel, or, worse yet, the number of channels you send dry signal from directly affect the level of noise! UGH! Another one: where the effects come back in, the recieving amp is noisy, so turning up the effects pot by the mains faders puts noise in the system. The final biggie is when the level of the effects input amp gain is such that you have to get a bad output level from the effects, ie, the effects loop input gain is low, so you have to turn up the effects output level, which amplifies the effects noise more... There are more ways to make a bad mixer than a good one! raybro ------------------------------ Date: Mon, 6 May 91 10:23:23 HST From: Mike 'IR' Ressler Subject: Re: Speaker Cables & Noise (well, Quadraverbs) To Raybro and anyone else who was confused by what I tried to say ... >Try as I might, I can't get this phrase to parse. What is `using the QV bare' >supposed to represent? (Maybe it's studio gig jargon---I havent' >haven't been in studio...) What I meant is that Alesis seems to have assumed that you would not use the QV in a mixer effects loop (i.e. send & return - I'm not a studio person either). That's the only thing I can think of for why they set their levels the way they did; also, there is some phrase in the manual to the effect of "if you are using the QV with a mixer, set ...". There was also a discussion of the this on the (long inactive) quadraverb discussion list as well. I'll dig up my manual and discussion "archive" and get back to you via private e-mail, Ray, unless there is a mass outcry to post the stuff to the list (if you want to be part of the mass outcry, please send e-mail to ressler@..., not to EMUSIC-L!!!!) Mike Ressler ressler@galileo.ifa.hawaii.edu ------------------------------ End of the EMUSIC-L Digest ******************************