Driving speakers in series and/or parallel

Archived from groups: rec.audio.tech (More info?)

This general issue has probably been discussed ad nauseum, but I want
to make sure my specific idea isn't going to blow up the Earth.

I have a small PA amp driving a single 8 ohm speaker that I use for
security monitoring in my retail store (mic in store, speaker in
office). I want to expand the system by adding 2 more speakers in
other areas.

If I go out and buy 2 cheap 4 ohm speakers, can I connect all three ( 8
+ 4 + 4 ) in series to my amps 16 ohm terminals?

Quality is not a big concern here (as long as it's not ridiculous). I
just want to avoid damaging the amp (or as stated above, destroying the
planet).

BTW the amp as terminals for 4 ohm, 8 ohm, 16 ohm and 70V connections.
Is there a better solution than what I'm suggesting?

Thanks in advance for all wisdom and advice.
David

Archived from groups: rec.audio.tech (More info?)

On 25 Apr 2005 13:48:40 -0700, "David Jennings" <davjen@cableone.net>
wrote:

>This general issue has probably been discussed ad nauseum, but I want
>to make sure my specific idea isn't going to blow up the Earth.
>
>I have a small PA amp driving a single 8 ohm speaker that I use for
>security monitoring in my retail store (mic in store, speaker in
>office). I want to expand the system by adding 2 more speakers in
>other areas.
>
>If I go out and buy 2 cheap 4 ohm speakers, can I connect all three ( 8
>+ 4 + 4 ) in series to my amps 16 ohm terminals?
>
>Quality is not a big concern here (as long as it's not ridiculous). I
>just want to avoid damaging the amp (or as stated above, destroying the
>planet).
>
>BTW the amp as terminals for 4 ohm, 8 ohm, 16 ohm and 70V connections.
>Is there a better solution than what I'm suggesting?
>
>Thanks in advance for all wisdom and advice.
>David
Well you might have speaker efficiency (loudness) issues either way.
Another issue in series is power HANDLING capacity of the 8 ohm vs the
2 @ 4 ohm (in series, 4 ohm w+ 4 ohm w = 8ohm W). If they are
different, I woul series the 4's and parallel the with 8, connected to
the 4 ohm tap.

The 70V output has lots of potential (ok, good pun also) for level
adjustment but needs a 70.7 V to Speaker transformer at each speaker.

, _
, | \ MKA: Steve Urbach
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, / / / Running United Devices "Cure For Cancer" Project 24/7 Have you helped? http://www.grid.org

Archived from groups: rec.audio.tech (More info?)

Laurence
70 Volts LINE busbar, not 70 Ohms!

David
I suggest you keep the 8 Ohm unit as is. If you go this extra route, you'll
need 2 PA loudspeaker stations, usually 4 or 8 Ohms, 5 Watts, but fitted
with a 70/100V line xformer - and a volume control is advised for zone
loudness adjustments.
You may even find them 2nd-hand. These high-Z devices can be daisy-chained
with cheapo telephone pair wire. You might want to add more one day.

"Laurence Payne" <lp@laurenceNOSPAMpayne.freeserve.co.uk> wrote in message
news:v21s615b0cdmtupg105uo8icq8ke1kmrpk@4ax.com...
> On 25 Apr 2005 13:48:40 -0700, "David Jennings" <davjen@cableone.net>
> wrote:
>
>>This general issue has probably been discussed ad nauseum, but I want
>>to make sure my specific idea isn't going to blow up the Earth.
>>
>>I have a small PA amp driving a single 8 ohm speaker that I use for
>>security monitoring in my retail store (mic in store, speaker in
>>office). I want to expand the system by adding 2 more speakers in
>>other areas.
>>
>>If I go out and buy 2 cheap 4 ohm speakers, can I connect all three ( 8
>>+ 4 + 4 ) in series to my amps 16 ohm terminals?
>
> You can try that. Or, if you connect the two new 4 ohm speakers in
> series they will present 8 ohms. Parallel the existing 8 ohm speaker
> to that, the amp will see 4 ohms.
>
> Your amp probably won't care much what you connect. Your problem
> will arise in the differing volumes you are likely to get from each
> speaker.
>
> The real answer to this is to use the 70 ohm line. Get a price on
> three 70 ohm speakers, maybe with included volume controls. If you
> can do this at an acceptable price, fine.
>
>>
>>Quality is not a big concern here (as long as it's not ridiculous). I
>>just want to avoid damaging the amp (or as stated above, destroying the
>>planet).
>>
>>BTW the amp as terminals for 4 ohm, 8 ohm, 16 ohm and 70V connections.
>>Is there a better solution than what I'm suggesting?
>>
>>Thanks in advance for all wisdom and advice.
>>David
>