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stevem
02-02-2005, 06:49 PM
I am connecting two pairs of identical 8 ohm woofers (1401Nd) to two mono amps. Is it better to wire them in parallel for 4 ohms, or in series for 16 ohms impedance? Should one way sound any different than the other? My amps are Bryston 7Bs which are actually bridged amps (series), which can also be wired in parallel. The manufacturer states that in bridged mode they will handle impedances down to 4 ohms. In Parallel they will handle 2 ohms. Any opinions on what is the optimum way to set this up? Thanks.

4313B
02-02-2005, 07:04 PM
Best practice is to wire in parallel for home use. Series is ok for SR venues.

stevem
02-03-2005, 02:42 PM
Thanks, Giskard. That's the way I had them hooked up, but then I started to wonder.

I checked with Bryston, and they told me I should use the series hook-up (bridged) with the amps. They recommend using this configuration down to 2 ohms. This surprised me because I didn't think bridged amps were stable into low impedances.

Steve
02-03-2005, 02:58 PM
Aloha
I have found this( attached pict ) to be very helpful in wiring multiple speakers in keeping the ohmage within specs. Simple diagram.....

The link is the page of the web site I pulled the diagram off.
http://www.abrown.com/spkrwire.htm

Steve

duaneage
02-03-2005, 08:31 PM
For parallel speakers this equation will solve for more than 2 drivers

1
------------------- = R total
1/R1 + 1/R2 + 1/R3

For three 8 ohm speakers

1
------------------- = 2.66 ohms
1/8 + 1/8 + 1/8

Keep adding drivers to the bottom of the equation if needed. Best to start out with 16 ohm drivers if you plan to have 4 or more in parallel. You can also have parallel networks connected in series. Two 3 driver networks in series in the above example would yield 5.3 ohms.

Of course you realize speakers have impedance that can vary from around 15 ohms at resonance to as low as 4 ohms in the passband to over 8 ohms around a crossover and any amount in between. Different speakers systems with different crossover networks will exhibit wild impedance swings and unusual phase changes if connected together. Amplifiers really don't like loads like that. Unless your driving electrostatic speakers (which are largly resistive) the phase changes may disturb your amp, hence Bryston's legal department recommends that their technicians say "go with series".

A voltmeter and frequency generator is really helpful for checking the impedance through the range, a O-Scope can be used to check the phase relationship. Sounds like a lot of work but it prevents problems with multiple driver arrays.

Flodstroem
02-04-2005, 04:08 PM
hi Stevem

When take in to account the damping factor and the clipping level of your power amp when series or parallel connecting your speaker, you must also think of that.
Maybe this could be of interest:

If your power amp have a lot of reserv power (high voltage output), then you will get the best damping factor with a high impedance speaker connected to your low impedance output (speakers in series connection).

If your power amp have a low voltage output, but a high level of current output capabillity, then you should connect your speakers in parallel (you will get high power output before clipping).

This is my own thoughts, maybe Im wrong but there is always Giskard or someone else in the Forum who could explain it more specific ?

Best Regards

stevem
02-05-2005, 08:54 AM
The amps I have can be set up to provide either high voltage (series bridged) or high current (parallel), so theoreticlly I could optimize either of the two examples you gave. Bryston still recommends the series (bridged) connection to the woofers wired in parallel.