Impedance Matching

[wesw]

I have a friend that wants me to add an extra pair of speakers to a sony bookshelf system for his patio. The problem I'm running into is that the speakers of the system are 6ohm speakers, and every oudoor speaker I can find for a reasonable price is 8 ohm.

What are my options for the setup of this? Could someone point me to an impedance matching transformer that would do the job? or a set of 6 ohm patio speakers? (If I have 2 sets of 6 ohms, I can wire in parallel and use a transformer to double that) I want to keep each load balanced, so the indoor speakers don't have to be blaring loud to hear the outdoor speakers.

Thoughts...??

[curt_c]

> I have a friend that wants me to add an
> extra pair of speakers to a sony bookshelf
> system for his patio. The problem I'm
> running into is that the speakers of the
> system are 6ohm speakers, and every oudoor
> speaker I can find for a reasonable price is
> 8 ohm.

> What are my options for the setup of this?
> Could someone point me to an impedance
> matching transformer that would do the job?
> or a set of 6 ohm patio speakers? (If I have
> 2 sets of 6 ohms, I can wire in parallel and
> use a transformer to double that) I want to
> keep each load balanced, so the indoor
> speakers don't have to be blaring loud to
> hear the outdoor speakers.

> Thoughts...??

No matching necessary. The 8 ohm speakers will be just a little easier load for the system. -Unless Sony makes a tube powered bookshelf system I don't know of...

C

[wesw]

I'm a bit confused, or maybe I didn't make my intentions clear. I want to drive the pair of 6 ohms with the 8 ohms. My two options without impedance matching would be 3.43 ohms and 14 ohms...

> No matching necessary. The 8 ohm speakers
> will be just a little easier load for the
> system. -Unless Sony makes a tube powered
> bookshelf system I don't know of...

> C

[curt_c]

> I'm a bit confused, or maybe I didn't make
> my intentions clear. I want to drive the
> pair of 6 ohms with the 8 ohms. My two
> options without impedance matching would be
> 3.43 ohms and 14 ohms...

Hmmm,
Wiring speakers in series is generally not an acceptable option even if they are the identical part. Won’t harm the amp, but the speakers interact with each other, and may cause response irregularities.

If the Sony cannot handle 4 ohm loads, you may not have too many alternatives except to replace both sets of speakers with 16 ohm designs, -or perhaps just buy another amp…

C

[wesw]

I may have to propose that, but through previous talks, he doesn't want to do that if we don't have to. Using a transformer like the one below, I could wire 2 6 ohm sets in parallel and double the impedance with the transformer, but I'd have to find a set of 6ohm patio speakers, and I'm at a loss there...

Thanks for your comments, though! You've confirmed what I've been thinking...

<A HREF="http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=302-304">http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=302-304</A>

[curt_c]

OK, use that xfmr, hook up an additional 8 ohm speaker, use the x2 tap. Your combined impedance will appear at the amp to be 6.8 ohms, assuming both speakers present a resistive load of exactly 6 and 8 ohms, -which they assuredly will not. That’s another story, but perhaps one germane to
this discussion.

A solid state amp output is not like an RF transmitter, and does not need to drive a tuned circuit to operate properly. For all practical purposes, it is a constant voltage source and will supply whatever current is demanded by the speaker load, up until the point the protection circuits activate, -or the output drivers go up in smoke.

Amps are rated with minimum impedance specs, not maximum, so any load above 6 ohms will be fine. -Realize there is no free lunch here and by using the xfmr, you double the impedance at the expense of reducing the speaker voltage by half.

C

[damkor]

Before you go buying more speakers or another amp, why not see if your amp can handle the pair in parallel. You never know.

Connect the left and right speaker together in parallel to one channel and slowly turn up the volume. How loud does it get before the system shuts down temporarily, or explodes? HaHa. It probably won't hurt the amp.

[wesw]

I've thought about just trying the 4 ohm, as he doesn't listen to music that loud and the amp might be able to "tolerate" it at low levels, but I'm not very comfortable with that. I don't need any magic smoke...

The other slight problem is that no money has been spent yet, so I don't have the transformers or the speakers yet, but I'm thinking this is the best option. I'm hoping the amp has enough headroom to allow for the decreased voltage at the speakers to still get listening volume levels out of them...

[donparsons]

Provided Link: Speaker selector (http://http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=300-610)


A more expensive solution, but one that allows lots of flexibility is this...