zoomer

iTrader: (3)

OK,, here is my researched report
1: Damping factor of IDENTICAL speakers in series is the same as for speakers by themselves. There is no change here. Thus for DVC subs, series connection of each vc is fine.

2: Damping factor will change and the effects of variying impedance and back emf from different drivers is a problem. So it is NOT recommended at all that you put different subs in Series. This would include same subs but in different boxes.

3: There can be an argument made that even same subs in one box or in identical boxes should not be put in series because of the differences between unit to unit. (however, I have not found any measuremnts or theoretical calculaions backing this up- In other words, what effects does the differences due to manufacturing tolerances have on the electrical and audio performance of 2 subs in series)
That is why if you have 2 4+4ohm DVC subs,, then wire each subs VC in series (=8 ohms) and then the 2 subs in paralell. (back to 4 ohms) as opposed to the othe way around (dvc in paralell, 2 subs in series)

However the question is WHY? Why would you want to put 2 subs in series stickyfingaz? Or was this just a theoretical question?
I can see someone (not a pro like you fingaz..) having 2 4ohm subs and only an older (probably low power) amp that cannot drive 2 ohms... In this case there would be very little advantage to putting them in series with a result of 8 ohms. That would cut the power output of the amp in half... No advantage to this... keep just one sub.


I will still ask JL...

StickyFingaz

iTrader: (4)

Well when I asked the question thinking of ways to wire 3 subs for a load of at least 1.5ohm. I was also looking at Fi Audio's subs and they only offer 2ohm and 1ohm DVC models so I was just trying to figure out a way to wire 3 of these for a load compatible for my amp. (Just daydreaming about future setups really ) I did some more reading on the JL Audio site and someone already somewhat revealed JL audio's reason for not wiring in series:

It is far less desirable to make subwoofer to subwoofer connections in series. Because of slight and unavoidable differences between speakers and because of the high likelihood of uneven loading between different speakers in a car, there will be slight differences in the mechanical behavior of the two speakers in series. These differences in movement result in induced voltage (called back EMF) being created by the speakers across the series connection. This effect causes a problem when two speakers which behave differently are connected in series because the speakers can modulate each other (cause each other to move), resulting in distortion. The problem becomes more serious as more speakers are connected in series.

A good experiment to show the effect of back EMF is the following: connect four speakers in series and short the positive and negative input leads of the series circuit. Push down on one cone with your hand; you will notice that the three other speakers will move in the opposite direction of the one you are pushing. Now, reconnect the speakers in parallel, short the inputs and push down on one cone. The speakers will not modulate each other because each one is shorted directly.

Back EMF modulation is not a concern when the voice coils of a dual voice coil speaker are wired in series to each other because the coils are physically coupled on one moving mass. Therefore, they cannot possibly modulate each other because they cannot move independently.

loud'n'proud

wow we can figure out how they work but we dont want to build one lazzy thats what it is.

zoomer

iTrader: (3)

Stickyfingaz:

I agree with what JL says except that they do not offer any DATA to show what happens when you put two same model subs in series.
I read a lot of theoretical stuff on many boards and advertising, and I am carefull. The concern about placing 2 identical subs in series is because of the variations in manufacturing. If the were perfectly the same then it would be OK. But they are not.

I am not suggesting in any way that you connect them in series, unless it is for low power use. So do heed their advice...It is just that I am curious and obtuse and do not take everything for granted. (especially if it comes from a company selling me speaker cables for $1000.)


The question is how small/big are the manufacturing differences from sub to sub, and how does this affect performance compared to the many many other effects.

For example, if one sub modulates another, how much distortion does it add? and how does this compare to the overall distorion of the sub? is it a small fraction of the overall distortion? or a large contributor.

Theory is good if you do the math with rigor. If you do not have all of the data to put in the equations, then you have to measure. I have seen neither theory nor measuremnts that tells me in numbers what happens when you put 2 subs in series. So I cannot comment on how much worse 2 subs in series will sound compared to in parallel.

I asked JL for data to back up their statement...I am not optimistic if they will provide.

eg0r

iTrader: (2)

wow thats some good info
i do have coils in series but subs in parallel but ill definatly remember this for the future
thx for bringing the info up guys!

StickyFingaz

iTrader: (4)

Thanks for all the insight and help Zoomer! Please keep us up to date if JL ever gets back to you.

What? JL makes overpriced stuff?!?

zoomer

iTrader: (3)

I was refering to a well known cable company..um what was it Godzilla? Frankenstein? umm oh yes Monster!

Dukk

I have said it before and I will say it again:

SERIES wiring is the DEBIL!!

And I see that you have discovered the reasons why.

Haunz

iTrader: (3)

zoomer makes a good point and as usual JL is only telling 1/10 of the story... And thats already on top of the first assumption made.....

anyone who understands the nature of electricity knows that the signal between voice coils in series must be identical... so whats better.... several voice coils all modulated to each other due to electro/mechanical variation...... or the same coils not modulated to eachother with the same electro/mechnical variations.... ?


As I recall this topic came up in the carsound forums years ago and RC pointed out that there is no real difference..... coincidently, this same topic is currently being discussed in the same forums and all Navone has recommended is avoiding multiple drivers all together....

JohnVroom

I suppose a large number of drivers in series COULD 1-put together a difficult impedance load for an amp at a particular frequency 2- each woofer in series or parallel would electrically affect the others (EMF and CEMF) making transients slower and everything a little less precise (bad for SPL and SQ) 3- I would like to think the CEMF would not be of a significant magnitude to damage a transistor or reverse bias the system... but you never know.

I don't think the 16 ohm load to the amp would be a big deal (probably not too loud though) but the accumulated inductance of 4 or 5 drivers might be.

On a similar thought I suspect a 16 ohm PA driver would work fine in an auto. But a lot of amplifiers don't have a very strong voltage generation capability (that's expensive). The US Amps USA1000X cost more to manufacture than the USA1000 due to the voltage drive circuit of the 1000X