This query relates to a recent build of a SLOB, which uses 4x8" drivers per side, configured push-push. The speaker was my variation on XRKs XSD (a much more budget version!). I figured I'd post a separate query to avoid cluttering up his build thread.
My question is about the merits of series vs parallel wiring for woofers that are configured as push push. I currently have them in series, as I originally had a passive xo and it helped with impedance. I now have a fully digital crossover using dsp.
When playing some bass heavy tracks I noticed that a woofer on one side appeared to be showing a much greater level of excursion than its opposing driver. Bearing in mind the drivers are cheap as chips - could this effect somehow be a result of series wiring? The obvious answer would be to wire them in parallel and compare, but I'm wanting to understand if there is any theoretical reason for what I observed?
My question is about the merits of series vs parallel wiring for woofers that are configured as push push. I currently have them in series, as I originally had a passive xo and it helped with impedance. I now have a fully digital crossover using dsp.
When playing some bass heavy tracks I noticed that a woofer on one side appeared to be showing a much greater level of excursion than its opposing driver. Bearing in mind the drivers are cheap as chips - could this effect somehow be a result of series wiring? The obvious answer would be to wire them in parallel and compare, but I'm wanting to understand if there is any theoretical reason for what I observed?
Im just guessing but till an expert turns up heres some food for thought.
Theoretically it looks like an out of spec driver ( coil or suspension) or a bad wiring connection.
If wiring is good the high excursion driver may or may not be the problem. The problem may be its partnered driver.
Try wiring in parallel and see if the high excursion driver is now lower excursion. If so it may have high Re or its partner is low Re. If its still high excursion the partner driver might be stiff. If you press on it is it noisy or stiff? Put a AAA battery across the terminals and measure the displacement. Then test Re with a multimeter set to ohms. Can you measure the resistance across the drivers terminals and list the values with the driver with the greater excursion and its pair labelled. Also paste the driver model and specs?
Theoretically it looks like an out of spec driver ( coil or suspension) or a bad wiring connection.
If wiring is good the high excursion driver may or may not be the problem. The problem may be its partnered driver.
Try wiring in parallel and see if the high excursion driver is now lower excursion. If so it may have high Re or its partner is low Re. If its still high excursion the partner driver might be stiff. If you press on it is it noisy or stiff? Put a AAA battery across the terminals and measure the displacement. Then test Re with a multimeter set to ohms. Can you measure the resistance across the drivers terminals and list the values with the driver with the greater excursion and its pair labelled. Also paste the driver model and specs?
Woofer model is MCM 55 - 3231. Nothing special but a cheap woofer to experiment with.
I think the next step will be to wire in parallel, or at least 2 pairs in parallel and see if it makes a difference. Could variations in Re cause this type of behaviour in when wired in series?
I think the next step will be to wire in parallel, or at least 2 pairs in parallel and see if it makes a difference. Could variations in Re cause this type of behaviour in when wired in series?
Normally wire in parallel, then series since this way a driver can go bad/blow and doesn't take down the entire series leg.
The excursion should be the same for identical series or parallel woofers individually given the same voltage in free air.
Variations in Re, suspension, or coil position in the magnetic gap all could cause variations in excursion whether wired in series or parallel.
Though the speakers are mounted "open baffle", there is a slight difference in loading between each of the four drivers due to the different proximity to the rear wall, floor and planter cabinet placed along side.
You choose the exact woofer I had picked out to try this speaker.
Did you measure in room response or specs of the woffers?
Klaus
I am currently driving speakers with a cheap class D amp with DSP and boosting low end. I'm getting reasonably even in-room response to 40hz which is sufficient for my needs. From my measurements, distortion ramps up below 50hz, but overall I've been happy for such a cheap driver.
The reason may be in the different resonant frequencies of the speakers. They have a higher impedance at their resonant frequency.
Beautiful job on your SLOB. Do you have any pictures of the back showing details of driver mounting?
You do amazing woodwork. Thanks.
You do amazing woodwork. Thanks.
You can use a cheap amplifier board D for each pair of speakers. Parallel connection.
Slightly different note. How should the wiring be done for 5 ohms if I were to use 6 x 8 inch per speaker with
cones facing each other. A drawing would be much appreciated
Thanks
cones facing each other. A drawing would be much appreciated
Thanks
This is the most accurate answer so far.
This does not only happen with cheap drivers. I even experienced it with new out-of-the-box JBL2226 woofers when i was running them in in free air and wired in series.
Try to wire them in parallel. Maybe you would have to use two amp channnels for the woofers in this case. You may also use series-parallel with the middle nodes of both series connections wired together (I don't have a better description if unclear I can do a drawing).
And last but not least: If one of the four drivers is wired in opposite polarity things like that could also happen with perfectly equal divers.
BTW: Very nice looking speaker !
Regards
Charles
That hypothesis is spot on for narrow resonate frequencies but I cant see how it would generalise to music? Cheap drivers with divergent Re and or Qms are common likely issues with series wiring.Its easily tested for.
Ohms has a law for that. Hornresp is not just good for slob's (aka ripoles) but will do the impedance calcs too for serious slobs with multiple drivers eg Re = 8ohms:
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I can tell you wiring in series vs parallel with most passive crossovers or DC, the first driver in any of my arrays takes the heat. It is also the first in a series/parallel if I use an accelerometer fitted to a controller/driver for the correction VC.
The last driver is getting the least voltage. I've set up several arrays they are all the same. I always feed array drivers from the middle of the wiring run to either end, never top to bottom or visa versa. I did the testing so long ago it was done with analog test equipment and 3 people watching the dials. Not to sophisticated but it was what WE needed to stop blowing drivers and amps up. Phase Linear (s) were blowing up faster than you could get one fixed. Macs, Krells, and ML could suck a power pole dry. Your pocket book too.
I normally wire planars 2 or 3 drivers in series and then in parallel. I always shoot for above 10ohms (static) for mids and highs. I seldom wire lower than 8ohms (static) for sub or bass drivers. I use PP valve amps for above 300hz and HD class D pro amps for bass duty. Everything (bass) is direct coupled with correction.
I need to see a schematic of your wiring. I suspect how your drivers are wired is the key to better voltage distribution but also how well the dampening works. Direct coupled with short heavy cable WILL have dampening for the drivers and a passive XO will NOT. It relies on a spring to return the driver from overshoot, there is usually a cap, inductor and a resistor before it gets to the VC in a passive, in other words there is NO dampening via the power amp at all. DSP depending on the type can be a issue to. I've had to deal with some pretty primitive DSP programming and implementation of the little they did use. Don't discount the fact you may not have enough dampening to control the drivers and a wiring experiment is in order.
Do you have a heftier amp? I use 12Ks, they haven't let me down in over 10 years of use. I paid 375.00 each at the time.
They will control anything and not over dampen.
I'm sure there is a more eloquent answer with all kinds of ways to figure it out. My way is very simple field test with simple hand held equipment. I don't like complicated things, especially when they aren't to begin with. LOL Does that make any sense?
If you want to test my information on how the drivers respond to your current wiring, use a thermal gun. It will tell you very quick if one driver is being driven harder vs (just being) moved. Just because it's moving doesn't mean the VC is receiving voltage. BUT something is moving that cone. Don't rule out an optical CONCLUSION either. LOL
The last driver is getting the least voltage. I've set up several arrays they are all the same. I always feed array drivers from the middle of the wiring run to either end, never top to bottom or visa versa. I did the testing so long ago it was done with analog test equipment and 3 people watching the dials. Not to sophisticated but it was what WE needed to stop blowing drivers and amps up. Phase Linear (s) were blowing up faster than you could get one fixed. Macs, Krells, and ML could suck a power pole dry. Your pocket book too.
I normally wire planars 2 or 3 drivers in series and then in parallel. I always shoot for above 10ohms (static) for mids and highs. I seldom wire lower than 8ohms (static) for sub or bass drivers. I use PP valve amps for above 300hz and HD class D pro amps for bass duty. Everything (bass) is direct coupled with correction.
I need to see a schematic of your wiring. I suspect how your drivers are wired is the key to better voltage distribution but also how well the dampening works. Direct coupled with short heavy cable WILL have dampening for the drivers and a passive XO will NOT. It relies on a spring to return the driver from overshoot, there is usually a cap, inductor and a resistor before it gets to the VC in a passive, in other words there is NO dampening via the power amp at all. DSP depending on the type can be a issue to. I've had to deal with some pretty primitive DSP programming and implementation of the little they did use. Don't discount the fact you may not have enough dampening to control the drivers and a wiring experiment is in order.
Do you have a heftier amp? I use 12Ks, they haven't let me down in over 10 years of use. I paid 375.00 each at the time.
They will control anything and not over dampen.
I'm sure there is a more eloquent answer with all kinds of ways to figure it out. My way is very simple field test with simple hand held equipment. I don't like complicated things, especially when they aren't to begin with. LOL Does that make any sense?
If you want to test my information on how the drivers respond to your current wiring, use a thermal gun. It will tell you very quick if one driver is being driven harder vs (just being) moved. Just because it's moving doesn't mean the VC is receiving voltage. BUT something is moving that cone. Don't rule out an optical CONCLUSION either. LOL
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What I'm seeing vs what it's saying is 3P 2S? Am I missing something? That is 3S 2P if the left side is + and the right -. I can't see how the voltage is being distributed to drive them equally. I'd use a simple DMM.
That's part of a schematic? The schemo is L/R, + -, ?
I sure like your cabinets. Top notch work, you'll get it worked out.
The wiring above needs to be 3S 2P to drive equally. It's close to a 4 ohm static load if the drivers are 7.5-8.0 ohm.
The only other issue is, if this is another dream. Coffee!
Regards