25 volt system questions.

[Dale Farmer]

Hi folks.
I've been dragged into agreeing to help my brother upgrade his
church's PA system. It is a 25 volt speaker system, which I had
not previously run into. Is this pretty much the same as a 70 volt
system at lower voltage, or something fundamentally different that
I am missing?
Also if someone can point me to a good resource for how to
select new speakers for such a system, and the methods of selecting
which transformer taps on them, I would be appreciative.

Thanks.

--Dale

[Scott Dorsey]

Dale Farmer > wrote:
> I've been dragged into agreeing to help my brother upgrade his
>church's PA system. It is a 25 volt speaker system, which I had
>not previously run into. Is this pretty much the same as a 70 volt
>system at lower voltage, or something fundamentally different that
>I am missing?

It's the same general constant current system, just at a lower voltage
(and therefore requiring heavier gauge cable). This is done because in
some locations, 70V wiring has to be treated as Class I and put in conduit.
The NEC doesn't require this, but local code does in some places.

> Also if someone can point me to a good resource for how to
>select new speakers for such a system, and the methods of selecting
>which transformer taps on them, I would be appreciative.

You want new distributed speakers?

Basically, set the thing with the amp at the right level, and select the
tap that gives you the right perceived volume with the amp that way. You
probably want higher levels at the back of the room than at the front, for
instance, if it's a distributed system in an auditorium.

Or is this just for the hallways and narthex?

The Yamaha book has some info on these things.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Dale Farmer]

Scott Dorsey wrote:

> Dale Farmer > wrote:
> > I've been dragged into agreeing to help my brother upgrade his
> >church's PA system. It is a 25 volt speaker system, which I had
> >not previously run into. Is this pretty much the same as a 70 volt
> >system at lower voltage, or something fundamentally different that
> >I am missing?
>
> It's the same general constant current system, just at a lower voltage
> (and therefore requiring heavier gauge cable). This is done because in
> some locations, 70V wiring has to be treated as Class I and put in conduit.
> The NEC doesn't require this, but local code does in some places.
>
> > Also if someone can point me to a good resource for how to
> >select new speakers for such a system, and the methods of selecting
> >which transformer taps on them, I would be appreciative.
>
> You want new distributed speakers?
>
> Basically, set the thing with the amp at the right level, and select the
> tap that gives you the right perceived volume with the amp that way. You
> probably want higher levels at the back of the room than at the front, for
> instance, if it's a distributed system in an auditorium.
>
> Or is this just for the hallways and narthex?
>
> The Yamaha book has some info on these things.
> --scott
> --
> "C'est un Nagra. C'est suisse, et tres, tres precis."

OKay thanks. Probably won't put in new speakers, but I want to relocate
the existing speakers. The place is all hard walls and tile floor, and the
speakers are placed halfway down on the side walls aiming to bounce off the
inside of the roof, and another set at the rear firing forward. No delays
anywhere. This causes a lot of intelligibility problems, and some folks
respond
to this by stepping in to the little closet where the amp lives and turning it
up,
making the problems worse as it overdrives the speakers
I'm figuring on just moving them all to the front wall, on the same plane
as
the pulpits, and aiming them appropriately. I may need to get some more
powerful and more directional speakers so that the folks in the back pews
will be able to hear. the current speakers are just repackaged ceiling paging
speakers, not very directional.
I'll have to go find my Yamaha book now. haven't seen it since my last
move. Probably still in a box someplace.
I need to research also inductive loop and assisted hearing systems as
well.

--Dale

[Scott Dorsey]

Dale Farmer > wrote:
>
> OKay thanks. Probably won't put in new speakers, but I want to relocate
>the existing speakers. The place is all hard walls and tile floor, and the
>speakers are placed halfway down on the side walls aiming to bounce off the
>inside of the roof, and another set at the rear firing forward. No delays
>anywhere. This causes a lot of intelligibility problems, and some folks
>respond
>to this by stepping in to the little closet where the amp lives and turning it
>up,
>making the problems worse as it overdrives the speakers

Are these the usual crappy 8" full-range speakers with whizzer cones that
get used in cheap distributed systems? if so, you might get some benefit
by replacing them with better speakers, maybe with narrower radiation speakers.

> I'm figuring on just moving them all to the front wall, on the same plane
>as
>the pulpits, and aiming them appropriately. I may need to get some more
>powerful and more directional speakers so that the folks in the back pews
>will be able to hear. the current speakers are just repackaged ceiling paging
>speakers, not very directional.

I bet they are very directional at high frequencies even if they aren't very
directional below 5 KC or so... which is why they sound so weird when you
walk around.

The idea with distributed systems is that you always have the speakers near
the listener, so the direct to reflected ratio is very high even in a very
reflective room. But if they aren't pointed at the people listening, that
doesn't do much good.

> I need to research also inductive loop and assisted hearing systems as
>well.

Not many folks still do inductive loop... I think about everyone these days
is either running little RF systems or they are running infrared rigs like
the Sennheisers. Movie theatres like the infrared systems since you can
walk into any auditorium and you don't have to select the right channel for
the right movie or worry about interference between rooms, so I mostly know
about the IR stuff.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Richard Crowley]

Dale Farmer > wrote:
>
> OKay thanks. Probably won't put in new speakers,
> but I want to relocate the existing speakers. The place
> is all hard walls and tile floor, and the speakers are placed
> halfway down on the side walls aiming to bounce off the
>inside of the roof, and another set at the rear firing forward.
> No delays anywhere. This causes a lot of intelligibility
> problems, and some folks respond to this by stepping in to
> the little closet where the amp lives and turning it up,
> making the problems worse as it overdrives the speakers
> I'm figuring on just moving them all to the front wall,
> on the same plane as the pulpits, and aiming them appropriately.
> I may need to get some more powerful and more directional
> speakers so that the folks in the back pews will be able to hear.
> the current speakers are just repackaged ceiling paging
> speakers, not very directional.

In a room THAT reflective, you'll need a more directional speaker
system. That will allow you to direct the sound to the audience area,
avoiding hitting the reflective surfaces to uselessly bounce around
the room.

news:alt.audio.pro-live-sound is the newsgroup that specializes
in live reinforcement topics.

[Dale Farmer]

Scott Dorsey wrote:

> Dale Farmer > wrote:
> >
> > OKay thanks. Probably won't put in new speakers, but I want to relocate
> >the existing speakers. The place is all hard walls and tile floor, and the
> >speakers are placed halfway down on the side walls aiming to bounce off the
> >inside of the roof, and another set at the rear firing forward. No delays
> >anywhere. This causes a lot of intelligibility problems, and some folks
> >respond
> >to this by stepping in to the little closet where the amp lives and turning it
> >up,
> >making the problems worse as it overdrives the speakers
>
> Are these the usual crappy 8" full-range speakers with whizzer cones that
> get used in cheap distributed systems? if so, you might get some benefit
> by replacing them with better speakers, maybe with narrower radiation speakers.
>

Probably, but the day I was there, I didn't have an extension ladder with
me to go up and look.

>
> > I'm figuring on just moving them all to the front wall, on the same plane
> >as
> >the pulpits, and aiming them appropriately. I may need to get some more
> >powerful and more directional speakers so that the folks in the back pews
> >will be able to hear. the current speakers are just repackaged ceiling paging
> >speakers, not very directional.
>
> I bet they are very directional at high frequencies even if they aren't very
> directional below 5 KC or so... which is why they sound so weird when you
> walk around.
>
> The idea with distributed systems is that you always have the speakers near
> the listener, so the direct to reflected ratio is very high even in a very
> reflective room. But if they aren't pointed at the people listening, that
> doesn't do much good.
>
> > I need to research also inductive loop and assisted hearing systems as
> >well.
>
> Not many folks still do inductive loop... I think about everyone these days
> is either running little RF systems or they are running infrared rigs like
> the Sennheisers. Movie theatres like the infrared systems since you can
> walk into any auditorium and you don't have to select the right channel for
> the right movie or worry about interference between rooms, so I mostly know
> about the IR stuff.

My understanding is that most of the hearing aids nowadays are fitted with
inductive pickup coils. Do those pick up inductive loop installations?
An IR system was my second choice, but they were worried about the cost
of the receivers from theft and loss. Was also considering just installing
headphone jacks in various places and buying a separate headphone
amplifier for them. Walkman type headsets are inexpensive, and when they
disappear, they can go buy replacements at the walgreens across the street
for a buck or two.

--Dale