I thought those here might know the answer to this one ...
A small public body I am part of were recently involved with a couple of public events: a jubilee beacon lighting, and a mosaic unveiling. At
both of these, sterling efforts were made by those involved to speak
(address the crowd), but it became clear - to me, anyway - that some
sort of public PA was sorely needed. (The British public don't shut up
like they once did - and small children don't anyway [the unveiling was
of something the children at a school had made].)
A quick look at ebay gave me the impression that 55 to 120 pounds (if
bought new) should find us something suitable (basically a microphone
plus a box with a speaker/battery/amp in it, plus anti-howlround
circuitry), so I asked the other members of the body what they thought - including asking "have we got something already", as I've been caught
out that way before!
The RFO informs me that we _do_ have a "sound system", but it requires
power. I haven't seen it, so don't know if it's suitable, but if it is,
I wonder about providing power for it when used out of range of a socket
(the beacon lighting for example was more or less in a field).
My first thought was an inverter and battery - inverters of the capacity
I imagine would be needed are both small and cheap - but then I thought
we'd have problems ensuring it is charged. By the time inverter,
battery, and charger are considered, it's getting complicated - both
cost, portability, and storage (i. e. where we keep it all).
However, it occurs to me that maybe nowadays devices exist that combine
all three in a compact unit - i. e., inverter, battery, and charger -
and that those here would know. Do such combinations exist? I'm thinking "pro-sumer" level, if that's the right word - not ultra-cheap, but not
OB quality - it wouldn't be in regular use, only on special occasions.
Or would the cost of such a device approach that of a portable PA system anyway? (Might still be on: part-duplicating what we've already got
would likely cause some objections, even though it more than duplicates.)
I thought those here might know the answer to this one ...
A small public body I am part of were recently involved with a couple of public events: a jubilee beacon lighting, and a mosaic unveiling. At
both of these, sterling efforts were made by those involved to speak
(address the crowd), but it became clear - to me, anyway - that some
sort of public PA was sorely needed. (The British public don't shut up
like they once did - and small children don't anyway [the unveiling was
of something the children at a school had made].)
A quick look at ebay gave me the impression that 55 to 120 pounds (if
bought new) should find us something suitable (basically a microphone
plus a box with a speaker/battery/amp in it, plus anti-howlround
circuitry), so I asked the other members of the body what they thought - including asking "have we got something already", as I've been caught
out that way before!
The RFO informs me that we _do_ have a "sound system", but it requires
power. I haven't seen it, so don't know if it's suitable, but if it is,
I wonder about providing power for it when used out of range of a socket
(the beacon lighting for example was more or less in a field).
My first thought was an inverter and battery - inverters of the capacity
I imagine would be needed are both small and cheap - but then I thought
we'd have problems ensuring it is charged. By the time inverter,
battery, and charger are considered, it's getting complicated - both
cost, portability, and storage (i. e. where we keep it all).
However, it occurs to me that maybe nowadays devices exist that combine
all three in a compact unit - i. e., inverter, battery, and charger -
and that those here would know. Do such combinations exist? I'm thinking "pro-sumer" level, if that's the right word - not ultra-cheap, but not
OB quality - it wouldn't be in regular use, only on special occasions.
Or would the cost of such a device approach that of a portable PA system anyway? (Might still be on: part-duplicating what we've already got
would likely cause some objections, even though it more than
duplicates.)
However, it occurs to me that maybe nowadays devices exist that combine
all three in a compact unit - i. e., inverter, battery, and charger -
and that those here would know. Do such combinations exist? I'm thinking "pro-sumer" level, if that's the right word - not ultra-cheap, but not
OB quality - it wouldn't be in regular use, only on special occasions.
Or would the cost of such a device approach that of a portable PA system anyway? (Might still be on: part-duplicating what we've already got
would likely cause some objections, even though it more than duplicates.)
I thought those here might know the answer to this one ...
A small public body I am part of were recently involved with a couple of public events: a jubilee beacon lighting, and a mosaic unveiling. At
both of these, sterling efforts were made by those involved to speak
(address the crowd), but it became clear - to me, anyway - that some
sort of public PA was sorely needed. ...
At our Parish Beacon lighting event, someone brought a battery operated PA >sytem. It could be heard about 3 rows away - there were, I was told, over >800 people present.
A decent inverter is heavy - so is a battery. Not what I would call >'portable'.
I keep seeing annoying adverts on social media for portable "power >stations", which hold up to a kilowatt hour's worth of energy and have
an inverter built in, which can supply up to a kilowatt. Jackery comes
to mind, and can use a solar panel or mains charger. Bloomin'
expensive, though, at not far short of a quid per watt hour.
For more power and duration, I can buy an 1800VA portable generator for
a couple of hundred quid, or get a much quieter one for about five
hundred quid or fifty quid a day from the local hire shop.
I also keep hearing antisocially loud portable speakers with a claimed >battery life of a day's use, for a couple of hundred quid.
If you can use a soldering iron you can get 50W (or 50+50W) Class D amp
modules for silly cheap prices - like less than £20. The heat-sinking
on the chips keeps them cool enough - no need for great big chunks of
metal and/or cooling fans. You would need a couple of batteries -
Lithium modules to make up around 30V to work them, and a mic amp
module. You can avoid acoustic feedback simply by having a highly
directional mic (the type that fit on video cameras are quite good) and
set the mic gain so that you have to speak close to the mic.
Look around for PA speakers - hi-fi speakers are not suitable for PA work.
A good place to look for the speaker end of the business is the BHF
eBay site under Sound and Vision.
J. P. Gilliver (John) <G6JPG@255soft.uk> wrote:
I thought those here might know the answer to this one ...
A small public body I am part of were recently involved with a couple of
public events: a jubilee beacon lighting, and a mosaic unveiling. At
both of these, sterling efforts were made by those involved to speak
(address the crowd), but it became clear - to me, anyway - that some
sort of public PA was sorely needed. ...
One very important point is to mount the loudspeaker as high as
possible. It is no use putting the loudspeaker on the floor and
deafening the front two rows; those at the back still won't be able to
hear it.
This suggests that you need a loudspeaker that is separate from the
power supply and amplifier. Horn loudspeakers are vastly more efficient
than direct radiators and you quickly reach the size of installation
where they will save their initial cost and bulk by a reduction in the
size of the amplifier and power supply.
If the narrow coverage of a horn loudspeaker is unsuitable for the >distribution of the crowd, consider a vertical column loudspeaker, which
has a wide horizontal coverage but a narrow beam in the vertical
direction.
Both horns and columns appear to defy the 'inverse square' law to some
extent - which is useful if you need even coverage over a long distance. >[This point can be elaborated upon if anyone is interested.]
it occurs to me that maybe nowadays devices exist that combine all
three in a compact unit - i. e., inverter, battery, and charger
...I fear we're getting into too much complication: my initial
reason for posting here ("is there equipment that contains inverter,
battery, and charger in one box?") has mostly been cancelled by the revelation that the existing sound system probably can't be taken out of
the hall anyway, so anything we do get would be starting from scratch.
J. P. Gilliver (John) <G6JPG@255soft.uk> wrote:
...I fear we're getting into too much complication: my initial
reason for posting here ("is there equipment that contains inverter,
battery, and charger in one box?") has mostly been cancelled by the
revelation that the existing sound system probably can't be taken out of
the hall anyway, so anything we do get would be starting from scratch.
There are small 'busking' P.A. sets which meet your description, but you
really need a tripod or something to lift them up. There are often >slightly-damaged photographic or laser-level tripods going for a song at
car boot sales; with a bit of improvisation (and a piece of alloy tube),
you could probably make something that was adequate.
One very important point is to mount the loudspeaker as high as
possible.
On Wed, 22 Jun 2022 at 14:16:49, Liz Tuddenham
One very important point is to mount the loudspeaker as high as
possible. It is no use putting the loudspeaker on the floor and
deafening the front two rows; those at the back still won't be able to
hear it.
Indeed. The system that appeared at the village fete (_not_ provided by
the parish council; I don't know where it came from) had speakers on
poles. (I had a look at the kit, but I think it was considerably more elaborate than what I think the PC would sanction buying - if only on
storage grounds; it had two substantial speakers [and their poles], and
two moderately large equipment boxes.)
I think the small "indecent" inverters still put out about 70W, which
I'd have thought adequate for the purpose. But, as you say, the battery
would add to the weight (unless an expensive one like those for starting cars), and by the time you've added the charger as well, would be
hitting problems of cost, portability, and storage.
.. I certainly don't think the parish council would buy - or use - a generator.
I've since heard that the "sound system" we do have is locked in a
cabinet "so hall hirers can use it without changing the settings" - I
haven't seen it, but basically it sounds as if it's plumbed into the
hall, so not really portable at all, so if we do get something, it
_will_ be separate from that. So something self-contained - including
battery - seems likely. (Possibly with charger separate, though included
in the price.)
Do the things some people call bullhorns or loudhailers exist of a
quality that is comprehensible? The only ones I've seen used, although certainly loud enough, have usually been very distorted - suitable for political rallies where everyone knows what's being said anyway, but not really for "saying a few words" at a beacon lighting or mosaic unveiling
or similar. Not that I _particularly_ like that specific shape of
device, but it might be more acceptable for storage/asset-control
reasons than something in too many parts.
On Wed, 22 Jun 2022 at 14:16:49, Liz Tuddenham
One very important point is to mount the loudspeaker as high as
possible. It is no use putting the loudspeaker on the floor and
deafening the front two rows; those at the back still won't be able to
hear it.
Indeed. The system that appeared at the village fete (_not_ provided by
the parish council; I don't know where it came from) had speakers on
poles. (I had a look at the kit, but I think it was considerably more elaborate than what I think the PC would sanction buying - if only on
storage grounds; it had two substantial speakers [and their poles], and
two moderately large equipment boxes.)
On 22/06/2022 15:02, J. P. Gilliver (John) wrote:
On Wed, 22 Jun 2022 at 14:16:49, Liz Tuddenham
One very important point is to mount the loudspeaker as high as
possible. It is no use putting the loudspeaker on the floor and
deafening the front two rows; those at the back still won't be able to
hear it.
Indeed. The system that appeared at the village fete (_not_ provided by
the parish council; I don't know where it came from) had speakers on
poles. (I had a look at the kit, but I think it was considerably more elaborate than what I think the PC would sanction buying - if only on storage grounds; it had two substantial speakers [and their poles], and
two moderately large equipment boxes.)
There are still people round here happy to turn up with a caravan and a
few speakers on poles. I'm even tempted to set one up in my Land Rover.
On 22/06/2022 14:15, J. P. Gilliver (John) wrote:
I think the small "indecent" inverters still put out about 70W, which
I'd have thought adequate for the purpose. But, as you say, the battery
would add to the weight (unless an expensive one like those for starting
cars), and by the time you've added the charger as well, would be
hitting problems of cost, portability, and storage.
For light, portable power, people now use lithium batteries, which hold
a lot more energy per kilogramme and per cubic centimetre than lead
acid.
Even boaters on the canals in the UK are switching.
A car jump starter, which used to be a hefty lump, can now fit into a
jacket pocket. Okay, it's a wax jacket with poachers' pockets...
On 22/06/2022 14:39, J. P. Gilliver (John) wrote:
.. I certainly don't think the parish council would buy - or use - aFair enough. Too easy to steal, and really cheap ones are two stroke,
generator.
which give off some 'orrible fumes.
Mine was four stroke, and inaudible at 50 metres, though there was a
road nearby.
I've since heard that the "sound system" we do have is locked in aThey are available, but they tend to have the speaker in the box, which
cabinet "so hall hirers can use it without changing the settings" - I
haven't seen it, but basically it sounds as if it's plumbed into the
hall, so not really portable at all, so if we do get something, it
_will_ be separate from that. So something self-contained - including
battery - seems likely. (Possibly with charger separate, though included
in the price.)
isn't ideal. Be careful when buying as they have been known to claim a >hundred watts or more when powered by USB...
The loud portable speakers are actually not bad quality, though they
tend to be a bit bass heavy out of the box. Cut the bass back using EQ,
and the battery lasts even longer. I have a couple of (illegal here,
very cheap in France) radio mics, which will just plug in with no wire
to trip over. (One AA cell in the mic, one in the receiver, which looks >basically like a fat 1/4" plug, about 15 metres range.) Legal ones are,
of course available...
On Wed, 22 Jun 2022 at 18:35:51, John Williamson <johnwilliamson@btinternet.com> wrote (my responses usually FOLLOW):
On 22/06/2022 14:39, J. P. Gilliver (John) wrote:
.. I certainly don't think the parish council would buy - or use - aFair enough. Too easy to steal, and really cheap ones are two stroke,
generator.
which give off some 'orrible fumes.
I think storage would be a main problem.
Mine was four stroke, and inaudible at 50 metres, though there was a
road nearby.
(Seems odd you don't get Diesel ones in that sort of size.)
I think with these high-density batteries you have to be even more careful, too.
Still need to figure out charging - I think with these high-density
batteries you have to be even more careful, too.
Has become academic as it's fairly clear we're not going to try to make
the existing system portable after all - so anything we get will have
amp, speaker, and battery all in the one box - a "busker's unit" as
someone here put it.
Mine has a handle. ;-)Yes, I've seen them - even used one once (lent by a neighbour). Tempted
Even boaters on the canals in the UK are switching.
A car jump starter, which used to be a hefty lump, can now fit into a
jacket pocket. Okay, it's a wax jacket with poachers' pockets...
to get one. (For that sort of emergency-only requirement, trickle-charge
is OK.) [For the moment, I just keep the battery from my previous car -
J. P. Gilliver (John) <G6JPG@255soft.uk> wrote:<Generators>
On Wed, 22 Jun 2022 at 18:35:51, John Williamson
Mine was four stroke, and inaudible at 50 metres, though there was a
road nearby.
(Seems odd you don't get Diesel ones in that sort of size.)
Small diesel generators are *incredibly* noisy. If you added enough soundproofing, they would no longer be small.
On 23/06/2022 08:57, Liz Tuddenham wrote:
J. P. Gilliver (John) <G6JPG@255soft.uk> wrote:
<Generators>On Wed, 22 Jun 2022 at 18:35:51, John Williamson
Mine was four stroke, and inaudible at 50 metres, though there was a
road nearby.
(Seems odd you don't get Diesel ones in that sort of size.)
Small diesel generators are *incredibly* noisy. If you added enough soundproofing, they would no longer be small.
They are also amazingly expensive. Small diesel engines are difficult to make.
The smallest diesel generator I've seen is about 4 KVA, and that
was built in to a soundproof engine room on a boat.
J. P. Gilliver (John) <G6JPG@255soft.uk> wrote:
On Wed, 22 Jun 2022 at 18:35:51, John Williamson
<johnwilliamson@btinternet.com> wrote (my responses usually FOLLOW):
On 22/06/2022 14:39, J. P. Gilliver (John) wrote:
.. I certainly don't think the parish council would buy - or use - aFair enough. Too easy to steal, and really cheap ones are two stroke,
generator.
which give off some 'orrible fumes.
I think storage would be a main problem.
Mine was four stroke, and inaudible at 50 metres, though there was a
road nearby.
(Seems odd you don't get Diesel ones in that sort of size.)
Small diesel generators are *incredibly* noisy. If you added enough >soundproofing, they would no longer be small.
On 22/06/2022 15:02, J. P. Gilliver (John) wrote:
On Wed, 22 Jun 2022 at 14:16:49, Liz Tuddenham
One very important point is to mount the loudspeaker as high as
possible. It is no use putting the loudspeaker on the floor and
deafening the front two rows; those at the back still won't be able to
hear it.
Indeed. The system that appeared at the village fete (_not_ provided by
the parish council; I don't know where it came from) had speakers on
poles. (I had a look at the kit, but I think it was considerably more elaborate than what I think the PC would sanction buying - if only on storage grounds; it had two substantial speakers [and their poles], and
two moderately large equipment boxes.)
There are still people round here happy to turn up with a caravan and a
few speakers on poles. I'm even tempted to set one up in my Land Rover.
If you want a little project, try this:
http://www.poppyrecords.co.uk/other/250wAmp.gif
It will run 12 horns at 20 W each, all day on a pair of car batteries.,
I used it for Longleat Dog Show many years ago with the horns on the top
of a 30ft scaffolding tower. After we had been running for a while a
friend arrived and said "Do you want a reception report?" I asked what
he meant and he replied, "We could hear it in Frome High Street".
John Williamson <johnwilliamson@btinternet.com> wrote:
I used to build stuff like that, hardware and all, a few decades ago.
Then I discovered decent sounding modular stuff.
Most of the modules have low efficiency and a high quiescent current and there aren't many that can deliver 250W from a 24v supply. That was
why I decided to design my own. Some modules don't like driving an
output transformer with a load on the secondary that can vary from open-circuit to short-circuit and many shades of 'j' in between.
On 23/06/2022 14:36, Liz Tuddenham wrote:
If you want a little project, try this:
http://www.poppyrecords.co.uk/other/250wAmp.gif
I used to build stuff like that, hardware and all, a few decades ago.
Then I discovered decent sounding modular stuff.
On 23/06/2022 19:49, Liz Tuddenham wrote:
John Williamson <johnwilliamson@btinternet.com> wrote:
I used to build stuff like that, hardware and all, a few decades ago.
Then I discovered decent sounding modular stuff.
Most of the modules have low efficiency and a high quiescent current and there aren't many that can deliver 250W from a 24v supply. That was
why I decided to design my own. Some modules don't like driving an
output transformer with a load on the secondary that can vary from open-circuit to short-circuit and many shades of 'j' in between.
I'm not knocking it,...
(doesn't usually actually seem to need much charge, so I think it's
holding charge).]
John Williamson <johnwilliamson@btinternet.com> wrote:
On 23/06/2022 19:49, Liz Tuddenham wrote:
John Williamson <johnwilliamson@btinternet.com> wrote:I'm not knocking it,...
I used to build stuff like that, hardware and all, a few decades ago.
Then I discovered decent sounding modular stuff.
Most of the modules have low efficiency and a high quiescent current and >> > there aren't many that can deliver 250W from a 24v supply. That was
why I decided to design my own. Some modules don't like driving an
output transformer with a load on the secondary that can vary from
open-circuit to short-circuit and many shades of 'j' in between.
I didn't think you were - but several times I have heard people who
need a P.A. amplifier saying they are going to try making one the 'easy'
way by buying a module. They have always come unstuck and given up
after wasting a small amount of money and a large amount of time.
If you want a little project, try this:
http://www.poppyrecords.co.uk/other/250wAmp.gif
In article <1pu0xgo.1px6xk7loyzjgN%liz@poppyrecords.invalid.invalid>,
Liz Tuddenham <liz@poppyrecords.invalid.invalid> scribeth thus
John Williamson <johnwilliamson@btinternet.com> wrote:
On 23/06/2022 19:49, Liz Tuddenham wrote:
John Williamson <johnwilliamson@btinternet.com> wrote:I'm not knocking it,...
I used to build stuff like that, hardware and all, a few decades ago. >> >> Then I discovered decent sounding modular stuff.
Most of the modules have low efficiency and a high quiescent current and >> > there aren't many that can deliver 250W from a 24v supply. That was
why I decided to design my own. Some modules don't like driving an
output transformer with a load on the secondary that can vary from
open-circuit to short-circuit and many shades of 'j' in between.
I didn't think you were - but several times I have heard people who
need a P.A. amplifier saying they are going to try making one the 'easy' >way by buying a module. They have always come unstuck and given up
after wasting a small amount of money and a large amount of time.
Where would you get the output transformers then?..
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:
If you want a little project, try this:
http://www.poppyrecords.co.uk/other/250wAmp.gif
I don't want a little project, but just to say I appreciated the clear way the circuit is drawn. I'm guessing some kind of vintage drawing package,
eg on a classic Mac?
(although I have to say the unusual way electrolytics are drawn tripped me up - made me think of neons or spark gaps or something)
Did you wind the output transformer yourself, or is that a commercial part?
It's a pre-war German symbol. I could never remember which way around
the B.S. one was supposed to be
On Sat, 25 Jun 2022 18:55:04 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
<snip>
It's a pre-war German symbol. I could never remember which way around
the B.S. one was supposed to be
The thick, filled-in bar (the one that looks like a minus sign) is the negative.
Minus - negative.... and batteries are the same.
I've seen the same symbol used in pre-war French and some US diagrams,
so I'm not sure it was exclusively German.
I think my other comment would be that the two series chains of 22,000 microfard electrolytics across the supply input really ought to have equalising resistors associated with them.
J. P. Gilliver (John) <G6JPG@255soft.uk> wrote:
I thought those here might know the answer to this one ...
A small public body I am part of were recently involved with a couple of public events: a jubilee beacon lighting, and a mosaic unveiling. At
both of these, sterling efforts were made by those involved to speak (address the crowd), but it became clear - to me, anyway - that some
sort of public PA was sorely needed. ...
One very important point is to mount the loudspeaker as high as
possible. It is no use putting the loudspeaker on the floor and
deafening the front two rows; those at the back still won't be able to
hear it.
This suggests that you need a loudspeaker that is separate from the
power supply and amplifier. Horn loudspeakers are vastly more efficient
than direct radiators and you quickly reach the size of installation
where they will save their initial cost and bulk by a reduction in the
size of the amplifier and power supply.
If the narrow coverage of a horn loudspeaker is unsuitable for the distribution of the crowd, consider a vertical column loudspeaker, which
has a wide horizontal coverage but a narrow beam in the vertical
direction.
Both horns and columns appear to defy the 'inverse square' law to some
extent - which is useful if you need even coverage over a long distance. [This point can be elaborated upon if anyone is interested.]
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