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Thread: Speaker amp problem

  1. #11
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    Hang on Dave? The series parallel combination is surely perfect for many situations, and damping factor isn't really an issue with most modern amps unless its crazily bad, and the amp poorly designed. It's pretty common for there to be series split boxes laying around. I've certainly got some, and never ever noticed a sonic problem with them.

    I'm really intrigued by why it's such a bad idea - for me, needing to plug in an extra pair, or often even more speakers using them works pretty well.

  2. #12
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    Quote Originally Posted by rob aylestone View Post
    Hang on Dave? The series parallel combination is surely perfect for many situations, and damping factor isn't really an issue with most modern amps unless its crazily bad, and the amp poorly designed. It's pretty common for there to be series split boxes laying around. I've certainly got some, and never ever noticed a sonic problem with them.

    I'm really intrigued by why it's such a bad idea - for me, needing to plug in an extra pair, or often even more speakers using them works pretty well.
    What do you mean by "series split boxes" Rob and do you have schematics? What are the speakers you are plugging into them?

    There is another problem with seriesed speakers with valve amps? If you have a box that puts two 8R unots in series to get 16R and one is unplugged the amp is now unloaded and we all know valves do NOT like that! Valves are however very tolerant of lower loads. A 16R tap loaded to 8 even 4 R will usually be quite ok but a big amp, 50W+ might redplate and pop an HT fuse if you give it the beans.

    Damping factors: Yes, transistor amps have a high one in the hundreds. DF is the ratio of amp output Z to speaker Z and a typical sstate amp will be 0.02 Ohms* or better so DF =400 for an 8R load. Valve op stages, even very "hi fi" ones rarely get better than 0.1 Ohms DF= 80. The "classic" AC30 type 4X EL84 has an opz of about 60 Ohms! A big mother 100 watter with a whiff of NFB might get down to 10 Ohms.

    If you go back to the tranny amp with a DF of 400 and put two 4R speakers in series the DF is now ONE! High quality speaker design is based on the assumption that the drivers will "see" a very low source impedance, anything else will play ducks and drakes with the frequency response especially the lower octaves.

    *Some sstate amp use "current feedback" to raise the opz and hope to mimic the action of valves. Good idea but this entails inserting a low, 0.22-0.47R resistor in the earthy end of the speaker circuit which again is fine IF they use a meaty resistor, often a wee 5W job is used, gets hot and the print joints go dry and can even burn!

    Should say also that it is very difficult to measure such low opz's and it is done by indirect means.

    Dave.

  3. #13
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    Gee I started it with my series parallel suggestion LOL. Series parallel is used regularly to get correct speaker to amp impedance using multiple speakers. Talk about a mountain out of a molehill.

    Has the OP come back or just been scared off LOL.
    Alan

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    " Series parallel is used regularly to get correct speaker to amp impedance using multiple speakers"

    Not by anyone that wants quality bass Al! WHAT is so hard to grasp here? You Allan and you Rob are top audio blokes! You KNOW a speaker needs to be driven from a very low source impedance. The exception as I have stated is where 1) the amp has little or no damping anyway and where people don't give a ***t about the response, i.e. Gitists!

    Series speakers also means they are "protecting" each other as a fuse!

    (do I need to draw diagrams?)

    Dave.

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    Quote Originally Posted by ecc83 View Post
    " Series parallel is used regularly to get correct speaker to amp impedance using multiple speakers"

    Not by anyone that wants quality bass Al! WHAT is so hard to grasp here? You Allan and you Rob are top audio blokes! You KNOW a speaker needs to be driven from a very low source impedance. The exception as I have stated is where 1) the amp has little or no damping anyway and where people don't give a ***t about the response, i.e. Gitists!

    Series speakers also means they are "protecting" each other as a fuse!

    (do I need to draw diagrams?)

    Dave.
    If they are wired in correct phase there is not bass loss? I don't get anything you are saying? The only thing that changes is the amount of power each speaker puts out depending on the resistance of that speaker. Heres an explanation LiNK

    And here is an explanation on the wiring of Parallel, series and series parallel. LINK

    I have used series parallel in a large PA system to get the best impedance for the Amps and never suffered bad bass.

    Alan.

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    Attached is an impednace curve for a single, GP drive unit. If that is put in series with another such drive unit surely it is obvious that the current is going to be modulated BY that curve? That is the impedance plot for a single speaker. Imaging the havoc a 3 way crossover would cause!

    It is of course the current through the voice coil that produces the magnetic force, do we really want to make that proportoonal to some gahstly frequency dependant resistance? That is why speakers should be driven from a voltage source. The bass damping is a bit secondary since even if the amp had absolutely zero opz the voice coil has resistance, even so amplifiers help.

    Anyone with a bass speaker and tranny amp can try this...With the speaker unconnected, tap the cone. You will likely get a "boing". Now connect to a decent amp an power it up, VC at min. Now tap the cone..Thud. The resonance has been all but eliminated (the bigger the speaker and the bigger its maget the more obvious its effect.)

    I would not chaps, insult you by suggesting you got the speakers out of phase!

    I cannot speak for large, s/p'ed arrays but then they might have sounded even better ALL paralled with some matching transformers!

    But all this, hill or Everest is not my main point. That is that the OP needs another amplifier to drive the speakers in the remote room so he can set a proper level. (We used a mains variac on valve amps but DON'T put one on a tranny!)

    Dave.
    Attached Thumbnails Attached Thumbnails single-speaker-z-mod-png  

  7. #17
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    Have you looked up the speakers he plans to use, all this theory is not going to make any difference.

    I agree that the best way to do this is setting up a multi zone system using separate amps.

    Anyway we seemed to have managed to loose the OP.

    Alan.

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    More confused Dave. I have a pile of EV SX300s - probably 12 or so, and we use them for all kinds of things. Just a few days ago, we had a row of brass players. Two saxes, trombone and trumpet and they each wanted a monitor, and all wanted the same feed. I've got some plastic boxes, each with three speakon connectors. One is input, so the 1+ goes to out socket 1, 1+. The 1- connection goes to the last socket 1+ and then 1- back to the input 1-. Plug in a speaker to each outlet and they both work and the amp sees 16Ohms, not 8. Do the same with the other pair and in parallel the amp then sees 8 and is happy. To be honest it's find seeing 16, you just need to drive it a bit harder. Or the other connection possibility is one splitter, then daisy chain two speakers from the first two - that's a 4 ohm load, but with the splitter box, it's back to 8. I've been doing this for years and it solves all the problems.

    It can go wrong, when people don't think - you can have two in series, paralleled with one other - and that one is just louder, and this can sometimes even be useful. I don't use them as much now I have plenty of spare amps, but two in series with two in parallel works 100%, and the additional inductive load and the change to the damping factor doesn't upset the amps - most of which can drive down to 2 Ohms, so the occasional miswire to 4Ohms is never an issue. On occasions I've used the series splitter with 4 speaker, going up to a 32Ohm load, and it's strange to see a so much amp power producing so little output, but with a big amp, you can do this with no problems. 6 12" plastic boxes either side from a single stereo amp is a handy thing to be able to do.

  9. #19
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    Yes Rob, it can be and is done, (4x12 gitcabs have been mentioned) and guys like you that know what you are doing will get good results but you cannot avoid the laws of physics and putting a frequency dependant resistance in serious with another one will screw the frequency response. Whether the resultant is noticeable in any given situation is moot. I guess those guts just need "some" foldback!

    I would also be unwise to have a fairly complex series parallel setup where the unplugging of one speaker could kill sound on everything else. Then there is the fact that levels are all over the shop depending upon the Z of a particular speaker.

    I will agree, 100V line systems ARE more common in fixed site setups (the AWOL OP's!) but yonks ago we used them for point to poin meetings, AGM reinforcement and small AmDram situation. The big advantage is that you can hang more speakers on the system with virtually no change in level. If the ASM whats a feed into a dressing room 100 ft away? No problem, we just ran out some 5A lighting flex and gave them a wee box . A more sophisticated system used multicore alarm cable and so the "star" could have a FOH feed with VC but there was a relay switched full wick over ride so he/she did not miss their call.

    You have a shedload of speakers and S/Pll boxes. We had a few horns and line source speakers and big box of traffs!

    I sometimes wonder if the audio world has advanced that much?

    Dave.

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    Hey sorry I havent chimed in, travelling. At church now and i will check the unknown speakers.

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