WOOFERS WIRED IN SERIES-Help Please

**cjd** · 29 October 2007, 21:37 Monday

Impedance has nothing to do with performance, though... well... yeah. With respect to your line of questioning, nothing at all to do with performance. But your line of questioning doesn't really get you any closer to reaching your goal either. What you really should be considering is the net sensitivity of the design (even this is only important in a round-about way, as most drivers start to dynamically compress as they reach their excursion limits, not to mention amps clipping etc), the total potential output within the limits of driver excursion, and the overall enclosure design. Quality crossover will also help with certain aspects of perceived bass performance.

If you're running Class A amps, there's your heat issue.

How loud is loud?

C

**Piotr** · 30 October 2007, 04:05 Tuesday

A class A amp is producing the same heat at all time.

Short answer to your basic question, Yes!

The drivers will behave the same in series and parallell connection (if well matched).

What will differ is the voltage sensitivity. As you mention a parallell connection will give you 6dB more output for a given voltage on the amp output. The series connection will have the same voltage sensitivity as a single driver. Depending on the amp this may be a problem. Thing is you will have to raise the volume more on the series connection and that may clip the amp.. which sounds no good.

On the parallell connection you can reduce the volume on the amp with 6dB and still have the same output, hence this will give you 6dB more voltage headroom. Still the amp need to have a decent powersupply and output impedance (damping factor) in order to perform well into the parallell connection. IOW if the amp is well designed than the parallell connection will alowe you to play louder, so it depends on the voltage sensitivtiy of the speaker, the max voltage output of the amp before clipping and how current capable the outputstage in the amp is.

/Peter

**Scooter** · 30 October 2007, 15:47 Tuesday

Well, old lore on this issue tells: There are never two exactly identical drivers. And especially around the fs there are bound to be frequencies where the impedances don't match. Which places a different part of power on each driver, which in turn dimishes precision. Reflex designs with their double impedance peaks worse the issue.
And besides, the damping factor of your amp is, as far as control over a single driver is concerned, down to 1 (one), obviously.
I'd stay away from series connections for bass drivers...

**Piotr** · 30 October 2007, 19:25 Tuesday

The damping stays unchanged. If you place a pure resistance in series with one driver you are correct. In this case Q stays the same. Actually the two drivers in series will result in slightly better damping since the amps and cables series impedances becomes smaller relative the load when using two drivers in serie as comparde to one single.

It's definately possible to match drivers close enough, however it may take several drivers if you buy some chinese stuff. Buying from the better manufacturers you may get away with just ordering a quad. But sure, a parallell connection is "safer" unless you can match and measure.

I also would be more inclined to use the series connection with other than "twin-impedance-alignments".. iow. a closed box or open bafle instead of bassreflex, passive radiator or TL.

/Peter

**bottlebrush** · 30 October 2007, 21:27 Tuesday

Interesting comments so far. No one has suggested bass performance is not as good if two drivers are wired in series. I had worried about this as I had read that drivers wired in series do not produce bass as good as wired in parallel.The bass would be more 'woolly' and less controlled. With 'damping'--amp damping reduces by half when connected to 4ohms compared to 8ohms. Also, damping is not as good when drivers are connected in series---so I guess parallel vs series balances out,one vs the other. Class A amps do produce heat--no question about that. Using 4 ohm nominal speakers produces even more heat as the amp is producing more current to drive 4 ohm speakers.(I say 'nominal' because I know two 8ohm speakers in parallel actually dip to as low as 2.8 ohms(approx) .True,less volume is required to drive speakers wired in parallel,but more current is also required to drive them.To me, two 4ohm drivers wired in series would 'behave' like a single 8 ohm driver:--more volume required to drive them,but less current required.
I would definitely use quality drivers like Seas as I realise matching is important.
-bottlebrush-

**cjd** · 31 October 2007, 10:16 Wednesday

It should be a non-issue, yes. I think we've specifically stated that.

**crazybastard** · 31 October 2007, 11:30 Wednesday

May I ask a question along the same line?

say 8 woofers wired so that the net is 8ohms, you power it with 10 watts of amp power. Do each of the 8 woofers see the entire 10 watts the same as say putting 10 watt in a single 8ohm woofer?

**Piotr** · 31 October 2007, 12:08 Wednesday

Originally posted by crazybastard

May I ask a question along the same line?

say 8 woofers wired so that the net is 8ohms, you power it with 10 watts of amp power. Do each of the 8 woofers see the entire 10 watts the same as say putting 10 watt in a single 8ohm woofer?

If you have 8ohm woofers, you can't wire eight of them for a net of 8ohm... if that is what you meant. Four drivers can be wired for the same impedance as a single unit. You can also wire nine drivers.. or sixteen drivers and so on, for a net impedance of 8ohm or the same impedance as the single driver has.

That said.. assume a quad of 8ohm drivers wired in series-parallell and powered with 10 watts, then each of the four driver will receive 2.5 watts.

From another view.. the power you need (say 10W) to put into one driver for 100dB can be reduced to 2.5W for a quad. That means each driver in the quad will receive about 0.6W for a 100dB output when a single driver would need 10W for the same output. IOW multiple drivers means SIGNIFICANTLY reduced thermal compression which is a real issue for hifi drivers if reasonable dynamics is the goal.

The example above is for a driver of 90dB sensitivity and 8ohm nominal impedance.

Where the wavelength is long compared to the distance between the drivers a four driver series-parallell connection yeld a 6dB increase in output for a given input.

/Peter

**Dennis H** · 31 October 2007, 12:09 Wednesday

say 8 woofers wired so that the net is 8ohms, you power it with 10 watts of amp power. Do each of the 8 woofers see the entire 10 watts the same as say putting 10 watt in a single 8ohm woofer?

The 10 watts get divided up among the 8 drivers. Normally, you would wire them so they all get the same 1.25 watts but sometimes line arrays are wired so the drivers at the center of the line get more power than those at the ends.

**Piotr** · 31 October 2007, 12:59 Wednesday

bottlebrush;

I had worried about this as I had read that drivers wired in series do not produce bass as good as wired in parallel.The bass would be more 'woolly' and less controlled

There's no reason it should be that way. Physics say it will not.

With 'damping'--amp damping reduces by half when connected to 4ohms compared to 8ohms. Also, damping is not as good when drivers are connected in series---so I guess parallel vs series balances out,one vs the other.

Now which was it?

Now you say damping is reduced both when the impedance is lowered and when also when increased.. The series connection (as I mentioned earlier) will result in better damping factor. The series-parallell connection will give the same damping factor as a single driver.

Class A amps do produce heat--no question about that. Using 4 ohm nominal speakers produces even more heat as the amp is producing more current to drive 4 ohm speakers

No, as long as the amp is in the class A region (both output conducts for a complementary ouput) the power consumption is the same no matter the speaker impedance and the volume you play. The situation when the impedance is lower by a factor of two (4ohm speaker instead of8ohm) will result in the amp steps into class A/B territory earlier though. A complementary class A amp working as a voltage source will have it's class A power reduced to half when impedance is halved. A class A amp that delivers 100W into 8ohm will only give 50W into 4ohm. P=I^2 x R.

Well... the above is not entirely true but goes for total power consumtion. An interesting thing with a class A amp is that within the class A range the amp will produce the most heat when idling an no music signal is present. The more current the amp puts out to the load the cooler the amp will be and the hotter the voice coil will be.

There are class A amps that are different but the above is tre for a standard "high biased class A/B" type of class A amp.

True,less volume is required to drive speakers wired in parallel,but more current is also required to drive them.

Nope!

Let's put 1A thru a 8ohm speaker of 90dB sensitivity for 1W. P=1^1 x 8 = 8W. Every doubling of the power increases spl with 3dB which means that the single driver will produce 99dB with this 1A/8W input.

Now.. wire a second driver parallell with the first. For a given voltage out ie. a given position of the volume control this will result in a 6dB increase spl (from 99 to 105dB) becasue both drivers will take 1A (one ampere) from the amplifier. Now, let's turn down the volume knob so the voltage output is halved, then we will reduce the output with 6dB so we are back att 99dB which was the original output from the single driver.

Now lets look at the current. I=U/R which means that when the voltage is cut in half the current thru a given resistance will also be cut in half. The decrease of the volume knob that is required to lower the output with 6dB in order to end up at the same spl as with the single driver will now only put 0.5A thru EACH voice coil insted of 1A as was the case with the first single driver. The sum current will be; 0.5A+0.5A=1A. IOW the current needed to give a specifik ouptut from one or two driver is the same!!

Sorry for the clear as mudd explanation, I'm sure someone else could have made a better job but I did my best.

ops:

To me, two 4ohm drivers wired in series would 'behave' like a single 8 ohm driver:--more volume required to drive them,but less current required.

Hmm.. for a given voltage out from the amp the spl will be+3dB with the two 4ohm drivers and the current will also be the same. Voltage the same, current the same.. this teach us that an extra motor equals a power gain of 2 which is the same as +3dB. In order to end up with the same spl as a single 8ohm driver would have given we need to decrease the voltage iow. lower the volume with the knob, not by half as that would result in -6dB but by a factor 0.7 which equals -3dB. Less curretn as you say but also less "volume" or voltage at the output of the amp!

I would definitely use quality drivers like Seas as I realise matching is important.

Now that sounds like a wise decision to me.

/Peter

**bottlebrush** · 31 October 2007, 22:45 Wednesday

OK Peter,
thanks for your input.--what you say makes sense.
however----
""Hmm.. for a given voltage out from the amp the spl will be+3dB with the two 4ohm drivers and the current will also be the same. Voltage the same, current the same.. this teach us that an extra motor equals a power gain of 2 which is the same as +3dB. In order to end up with the same spl as a single 8ohm driver would have given we need to decrease the voltage iow. lower the volume with the knob, not by half as that would result in -6dB but by a factor 0.7 which equals -3dB. Less current as you say but also less "volume" or voltage at the output of the amp!""

---if this is the case,why do we often read "when using four ohm speakers-make sure the amp has plenty of power otherwise it may cook itself" :E

-if the amp has ''less volume'' (volume position)to produce the same SPL in a 4ohm nominal speaker(two 8ohms wired in parallel) and less volume in 8 ohm nominal(two 4ohm drivers in series)--than the volume position for a single 8ohm driver.---where's the problem in driving these loads?(compared to driving a single 8ohm driver) :roll:
-bottlebrush--

**Piotr** · 01 November 2007, 03:59 Thursday

Generally..

when the impedance is lowered more power will be dissipated in the ouputstage.

To optimize an output stage into a low impedance you need to use a PS with less voltage.

/Peter

**dobias** · 17 November 2007, 22:53 Saturday

I hope I can get an answer to my situation:
I have Wharfedale speakers, each side has (1) 12" full range speaker @15 ohms. I have (2) 12" woofers @6 ohms wired in parallel through a pair of 4.0mH air core coils(0.5DCR). My amp is a class A SS rated 120W @ 8 ohms RMS & 190W @4 ohms.
My calculations for my total impedence ignores the (2) 8 ohm tweeters as advised by Madisound. I figure my present impedence is a low 2.68 ohms. If I rewire to series connected woofers, the impedence would be 7 ohms.
How serious is my present low impedence for the amp &/or speakers?
dobias

**ThomasW** · 18 November 2007, 00:26 Sunday

Frank,

You have questions about this system scattered around 5 or 6 different threads. It's extremely confusing trying to understand what components you have and what you're trying to do.

How about starting a new thread spelling out everything and we'll go from there?

WOOFERS WIRED IN SERIES-Help Please

WOOFERS WIRED IN SERIES-Help Please

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