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Sam Bond
 
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Default Battery powered amplifier from car speakers and booster amp?

I want to build a portable amplifier for a musical instruments used indoors and
outside for incest (or morris dancing). As far as I can find, commercial ones
are rather expensive and wouldn't stand the odd shower of rain.

I've come across a couple of 40watt Pioneer 3 cones speakers and a "booster"
amplifier (2 * 100w, might be a bit dodgy if I'm not careful with the levels).
The amp actually has a couple of 600mv inputs so until it's working I shan't
bother with a preamp.

The question, really, is how to box the speakers. All I can find by Googling
seems to be hi-fi, large-ish adn not designed for out use.

I was thinking of shelf type chipboard (it seems rigid and comes foc from the
garage) as MDF is rather too heavy. The odd thing about most of the guitar
amplifiers I've seen are open backed, but most but not all of the bass
amplifiers are closed! I don't want a big box I have to carry it, the
instruments and the battery! The speakers are only 5" in diameter, so how small
a box can I get away with? Do I fill it with furry stuff? Do I stick a hole or
even a "port" in it?

Any help gratefully received!

Sam

--
601
  #2   Report Post  
BigWallop
 
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Default Battery powered amplifier from car speakers and booster amp?


"Sam Bond" wrote in message
...
I want to build a portable amplifier for a musical instruments used

indoors and
outside for incest (or morris dancing). As far as I can find, commercial

ones
are rather expensive and wouldn't stand the odd shower of rain.

I've come across a couple of 40watt Pioneer 3 cones speakers and a

"booster"
amplifier (2 * 100w, might be a bit dodgy if I'm not careful with the

levels).
The amp actually has a couple of 600mv inputs so until it's working I

shan't
bother with a preamp.

The question, really, is how to box the speakers. All I can find by

Googling
seems to be hi-fi, large-ish adn not designed for out use.

I was thinking of shelf type chipboard (it seems rigid and comes foc from

the
garage) as MDF is rather too heavy. The odd thing about most of the guitar
amplifiers I've seen are open backed, but most but not all of the bass
amplifiers are closed! I don't want a big box I have to carry it, the
instruments and the battery! The speakers are only 5" in diameter, so how

small
a box can I get away with? Do I fill it with furry stuff? Do I stick a

hole or
even a "port" in it?

Any help gratefully received!

Sam


What type of power supply are you going to use ?

Fibre-glass cases would be your best bet for the speakers being used
outside. Even covering the front with a water-proof membrane would be best
suited to this type of use. The skeleton could be made from timber or board
and then skinned in fibre to give it total water resistance. If they're big
enough they could be used a boats when your done with them as speaker
housings.


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The Natural Philosopher
 
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Default Battery powered amplifier from car speakers and booster amp?

Sam Bond wrote:

I want to build a portable amplifier for a musical instruments used indoors and
outside for incest (or morris dancing). As far as I can find, commercial ones
are rather expensive and wouldn't stand the odd shower of rain.

I've come across a couple of 40watt Pioneer 3 cones speakers and a "booster"
amplifier (2 * 100w, might be a bit dodgy if I'm not careful with the levels).
The amp actually has a couple of 600mv inputs so until it's working I shan't
bother with a preamp.

The question, really, is how to box the speakers. All I can find by Googling
seems to be hi-fi, large-ish adn not designed for out use.

I was thinking of shelf type chipboard (it seems rigid and comes foc from the
garage) as MDF is rather too heavy. The odd thing about most of the guitar
amplifiers I've seen are open backed, but most but not all of the bass
amplifiers are closed! I don't want a big box I have to carry it, the
instruments and the battery! The speakers are only 5" in diameter, so how small
a box can I get away with? Do I fill it with furry stuff? Do I stick a hole or
even a "port" in it?

Any help gratefully received!

Sam



First of all, what are you amplifying?

If its an electricguitar the amplifier is more specailsied than you
think, being anything but 'flat' response wise, needing about 10mV
sensitivity, 2mV is better, and an input impedance of 2M ohm ususally.

None of these will be available on teh car booster.

In addition, the loudspeakers that are used for cars are usually totally
inappriopiate for guitar use. They will blow.

You need something like a celestion 10".

On the other hand, if you are miking up acoutsic stuff, its a different
strory, but again 2mV sensitivity is required.

Give me some more details and I'll advise. I used to design this stuff.



  #4   Report Post  
Dave Plowman
 
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Default Battery powered amplifier from car speakers and booster amp?

In article ,
Sam Bond wrote:
I want to build a portable amplifier for a musical instruments used
indoors and outside for incest (or morris dancing). As far as I can
find, commercial ones are rather expensive and wouldn't stand the odd
shower of rain.


I've come across a couple of 40watt Pioneer 3 cones speakers and a
"booster" amplifier (2 * 100w, might be a bit dodgy if I'm not careful
with the levels). The amp actually has a couple of 600mv inputs so until
it's working I shan't bother with a preamp.


This sounds like car 'ICE' stuff. ICE booster amps are designed to run off
about 14.4 volts - ie with the engine running - to achieve their maximum
output - which in any case is likely to be rather optimistic. Using it off
a 'static' car battery is likely to drop that maximum output considerably.
Depending on how 'generous' they've been with the words, it might equate
more to a *real* 25 watts or so per channel. Also check what impedance of
loudspeaker it gives its maximum output to - some state 2 ohms, ie two 4
ohm speakers in parallel.
To build an amp which really does give its rated output off a car battery
which isn't on charge (11-12.volts approx) requires the use of a suitable
SMPS or a transformer coupled output. Both of which are costly.

The question, really, is how to box the speakers. All I can find by
Googling seems to be hi-fi, large-ish adn not designed for out use.


I was thinking of shelf type chipboard (it seems rigid and comes foc
from the garage) as MDF is rather too heavy. The odd thing about most of
the guitar amplifiers I've seen are open backed, but most but not all of
the bass amplifiers are closed! I don't want a big box I have to carry
it, the instruments and the battery! The speakers are only 5" in
diameter, so how small a box can I get away with? Do I fill it with
furry stuff? Do I stick a hole or even a "port" in it?


It depends on the type of speaker you're using. Car types will often be ok
with an open back box - think rear parcel shelf mounting. They should also
survive damp conditions.

I'd make the cabinet out of something waterproof if you expect it to get
soaked - fibreglass as BW says is the normal choice, and lighter than
things like chipboard.

Any help gratefully received!


--
*If you try to fail and succeed, which have you done? *

Dave Plowman London SW 12
RIP Acorn
  #5   Report Post  
Sam Bond
 
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Default Battery powered amplifier from car speakers and booster amp?

On Wed, 21 Jan 2004 08:47:03 +0000, The Natural Philosopher wrote:


First of all, what are you amplifying?


First, a fiddle. It has a piezo bridge pickup but has its own preamp, both made
by Fishman. Only needs amplifying outdoors.

Second, a traditional Japanese WX7 and VL70m pair. Yhe WX7 is a midi keyboard
that looks and plays like a clarinet, the VL70m is a "Virtual Acoustic Tone
Gnerator" that produces, apart from others, passable bassoon and bass clarinet
sounds. Runs off 12v.


If its an electricguitar the amplifier is more specailsied than you
think, being anything but 'flat' response wise, needing about 10mV
sensitivity, 2mV is better, and an input impedance of 2M ohm ususally.

None of these will be available on teh car booster.

In addition, the loudspeakers that are used for cars are usually totally
inappriopiate for guitar use. They will blow.

You need something like a celestion 10".


Yes. I understand that these, along with other percussion instruments, produce
quite a lot of peak energy.

I've been using someone else's "Pignose" 20 watt amp. It has a single 6.5" cone
that clearly doesn't manage some of the higher harmonics. Playing the
instruments through the home hi-fi (ish), they sound very much like the real
thing. Played through the Pignose, except in the octave around middle C, they
both sound like ....... The upper ranges of the clarinet and bassoon sounding
very electronic and similar. Mind you, it still sounds better than a Yamaha
"portable pa" box.

The advantage, I thought, of the car speakers was their relatively wide
frequency response and compactness.


Give me some more details and I'll advise. I used to design this stuff.


Thanks very much!

Sam

--
601


  #6   Report Post  
Sam Bond
 
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Default Battery powered amplifier from car speakers and booster amp?

On Wed, 21 Jan 2004 03:22:40 GMT, "BigWallop" wrote:



What type of power supply are you going to use ?


12v 7ah SLA.

Fibre-glass cases would be your best bet for the speakers being used
outside. Even covering the front with a water-proof membrane would be best
suited to this type of use. The skeleton could be made from timber or board
and then skinned in fibre to give it total water resistance. If they're big
enough they could be used a boats when your done with them as speaker
housings.


I should have said the speakers are actually only the drivers. I don't think
fibreglass would work very well for a cabinet unless it was very thick.

I don't want to play under water, the dancers get a bit soggy and rebelious. I
just want to be able the resist the odd shower without wrecking the cones.

Sam



--
601
  #7   Report Post  
Dave Plowman
 
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Default Battery powered amplifier from car speakers and booster amp?

In article ,
Sam Bond wrote:
What type of power supply are you going to use ?


12v 7ah SLA.


Is that a type of battery? I assume it is by the 'ah' description. A 100%
efficient 200 watt amp running at full power would flatten it in minutes.
And car booster amps are anything but 100% efficient.
For a reasonable portable outdoor system which will run for a couple of
hours reliably, you're looking at a decent sized car battery - say about
45 Ah. You don't want to flatten the battery if it's a lead acid type as
this will shorten its life.

--
*Gravity is a myth, the earth sucks *

Dave Plowman London SW 12
RIP Acorn
  #8   Report Post  
PJO
 
Posts: n/a
Default Battery powered amplifier from car speakers and booster amp?


"Dave Plowman" wrote in message
...
In article ,
Sam Bond wrote:
What type of power supply are you going to use ?


12v 7ah SLA.


Is that a type of battery? I assume it is by the 'ah' description. A 100%
efficient 200 watt amp running at full power would flatten it in minutes.
And car booster amps are anything but 100% efficient.
For a reasonable portable outdoor system which will run for a couple of
hours reliably, you're looking at a decent sized car battery - say about
45 Ah. You don't want to flatten the battery if it's a lead acid type as
this will shorten its life.


And they're also no good for connecting to pressure pads!


  #9   Report Post  
Fergal
 
Posts: n/a
Default Battery powered amplifier from car speakers and booster amp?

Depending on how much time & effort you want to expend, you could make
optimised enclosures for the speakers by measuring (or obtaining from
Pioneer) their Thiele-Small parameters which are used to calculate the
optimum box size and type for a particular speaker. Once you have these
parameters there are various programs available to work out box dimensions &
port sizes etc.

If that sounds like too much bother, just knock up a box of approx 0.5 cubic
foot internal volume and mount the speaker in it and see what it sounds
like. If there's not enough bass cut a hole in the front of the box and add
a length of 1.5-2 inch diameter tube and experiment with the length of the
tube until it sounds better, or you might not need the tube at all just the
hole. You can also experiment with modifying the volume of the box by
bunging in bits of expanded polystyrene to reduce it. BTW don't make the box
a cube or it will sound terrible due to standing wave cancellation etc. Try
to make each dimension of the box different. Golden ratios are a good start.

As BW suggests a timber frame covered in fibreglass would be
strong/light/weather resistant with the addition of some bitumen sheet stuck
to the inside of the panels to make them a bit less resonant. If the
speakers have plastic cones they should be fairly weather resistant as well,
so all you'd need on the front would be a grille to protect them in transit.

"Sam Bond" wrote in message
...
I want to build a portable amplifier for a musical instruments used

indoors and
outside for incest (or morris dancing). As far as I can find, commercial

ones
are rather expensive and wouldn't stand the odd shower of rain.

I've come across a couple of 40watt Pioneer 3 cones speakers and a

"booster"
amplifier (2 * 100w, might be a bit dodgy if I'm not careful with the

levels).
The amp actually has a couple of 600mv inputs so until it's working I

shan't
bother with a preamp.

The question, really, is how to box the speakers. All I can find by

Googling
seems to be hi-fi, large-ish adn not designed for out use.

I was thinking of shelf type chipboard (it seems rigid and comes foc from

the
garage) as MDF is rather too heavy. The odd thing about most of the guitar
amplifiers I've seen are open backed, but most but not all of the bass
amplifiers are closed! I don't want a big box I have to carry it, the
instruments and the battery! The speakers are only 5" in diameter, so how

small
a box can I get away with? Do I fill it with furry stuff? Do I stick a

hole or
even a "port" in it?

Any help gratefully received!

Sam

--
601



  #10   Report Post  
Sam Bond
 
Posts: n/a
Default Battery powered amplifier from car speakers and booster amp?

On Wed, 21 Jan 2004 10:27:48 +0000 (GMT), Dave Plowman
wrote:

In article ,
Sam Bond wrote:

12v 7ah SLA.


Is that a type of battery? I assume it is by the 'ah' description.


Sealed Lead Acid
A 100%

efficient 200 watt amp running at full power would flatten it in minutes.
And car booster amps are anything but 100% efficient.


Indeed, I don't expect to need much more than 10-15 watts. It's just all I have
at the moment is 100 watts. If all works well I may well change it, but not
unless I have to.

For a reasonable portable outdoor system which will run for a couple of
hours reliably, you're looking at a decent sized car battery - say about
45 Ah. You don't want to flatten the battery if it's a lead acid type as
this will shorten its life.


This is not "continuous" music like playing a record but a single instrument. It
makes a lot of difference to the power consumption. I've run a 20watt amplifier
for 4 sessions of 2 hours on an old 4ah SLA.

Sam

--
601


  #11   Report Post  
Sam Bond
 
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Default Battery powered amplifier from car speakers and booster amp?

On Wed, 21 Jan 2004 14:03:33 -0000, "Fergal" wrote:

Depending on how much time & effort you want to expend, you could make
optimised enclosures for the speakers by measuring (or obtaining from
Pioneer) their Thiele-Small parameters which are used to calculate the
optimum box size and type for a particular speaker. Once you have these
parameters there are various programs available to work out box dimensions &
port sizes etc.


Sadly car speakers don't come with proper specs, the best I've found show
"frequency response" and "sensitivity". I would hope that they are designed for
fairly small enclosures but I've seen a frequency response quoted of 30Hz -
32kHz.


If that sounds like too much bother, just knock up a box of approx 0.5 cubic
foot internal volume and mount the speaker in it and see what it sounds
like. If there's not enough bass cut a hole in the front of the box and add
a length of 1.5-2 inch diameter tube and experiment with the length of the
tube until it sounds better, or you might not need the tube at all just the
hole. You can also experiment with modifying the volume of the box by
bunging in bits of expanded polystyrene to reduce it. BTW don't make the box
a cube or it will sound terrible due to standing wave cancellation etc. Try
to make each dimension of the box different. Golden ratios are a good start.


That's just what I wanted to know.

As BW suggests a timber frame covered in fibreglass would be
strong/light/weather resistant with the addition of some bitumen sheet stuck
to the inside of the panels to make them a bit less resonant. If the
speakers have plastic cones they should be fairly weather resistant as well,
so all you'd need on the front would be a grille to protect them in transit.


The one's I've got have an add on grille, presumably to protect them from foot
damage in a car door.

Thanks Fergal.

Sam
--
601
  #12   Report Post  
Dave Liquorice
 
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Default Battery powered amplifier from car speakers and booster amp?

On Wed, 21 Jan 2004 10:27:48 +0000 (GMT), Dave Plowman wrote:

12v 7ah SLA.


Is that a type of battery?


Yes, a "Sealed Lead Acid" type. Commonly found in alarms systems for
backup power and in small UPSs.

A 100% efficient 200 watt amp running at full power would flatten it
in minutes.


Quite, my commercial UPS has two 12v 7A/Hr batteries in series. It's
currently telling me I have an uptime of 4 minets at 82% load or about
575W.

You don't want to flatten the battery if it's a lead acid type as
this will shorten its life.


Unless it's in your homebrew standby power system. B-)

A proper "leisure" battery will survive deep discharge and are
available in SLA format. You do need to take care with charging
compared to an open wet battery.

--
Cheers
Dave. pam is missing e-mail



  #13   Report Post  
Dave Plowman
 
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Default Battery powered amplifier from car speakers and booster amp?

In article ,
Dave Liquorice wrote:
You don't want to flatten the battery if it's a lead acid type as
this will shorten its life.


Unless it's in your homebrew standby power system. B-)


I hope it never gets used. But a PA system surely would?

Latest mod is to the invertor so I can set the dropout voltage to choice.

--
*Dance like nobody's watching.

Dave Plowman London SW 12
RIP Acorn
  #14   Report Post  
Fergal
 
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Default Battery powered amplifier from car speakers and booster amp?


"Sam Bond" wrote in message
...
On Wed, 21 Jan 2004 14:03:33 -0000, "Fergal"

wrote:

Depending on how much time & effort you want to expend, you could make
optimised enclosures for the speakers by measuring (or obtaining from
Pioneer) their Thiele-Small parameters which are used to calculate the
optimum box size and type for a particular speaker. Once you have these
parameters there are various programs available to work out box

dimensions &
port sizes etc.


Sadly car speakers don't come with proper specs, the best I've found show
"frequency response" and "sensitivity". I would hope that they are

designed for
fairly small enclosures but I've seen a frequency response quoted of

30Hz -
32kHz.


If that sounds like too much bother, just knock up a box of approx 0.5

cubic
foot internal volume and mount the speaker in it and see what it sounds
like. If there's not enough bass cut a hole in the front of the box and

add
a length of 1.5-2 inch diameter tube and experiment with the length of

the
tube until it sounds better, or you might not need the tube at all just

the
hole. You can also experiment with modifying the volume of the box by
bunging in bits of expanded polystyrene to reduce it. BTW don't make the

box
a cube or it will sound terrible due to standing wave cancellation etc.

Try
to make each dimension of the box different. Golden ratios are a good

start.

That's just what I wanted to know.

As BW suggests a timber frame covered in fibreglass would be
strong/light/weather resistant with the addition of some bitumen sheet

stuck
to the inside of the panels to make them a bit less resonant. If the
speakers have plastic cones they should be fairly weather resistant as

well,
so all you'd need on the front would be a grille to protect them in

transit.


The one's I've got have an add on grille, presumably to protect them from

foot
damage in a car door.

Thanks Fergal.

Sam
--
601


I found some useful stuff on making fibreglass speaker enclosures and other
aspects of car hifi which would be applicable to you he

http://www.jlaudio.com/tutorials/index.html


  #15   Report Post  
Sam Bond
 
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Default Battery powered amplifier from car speakers and booster amp?

On Fri, 23 Jan 2004 13:43:14 -0000, "Fergal" wrote:


I found some useful stuff on making fibreglass speaker enclosures and other
aspects of car hifi which would be applicable to you he

http://www.jlaudio.com/tutorials/index.html


Yes, thanks. I'd looked at it some time ago but had forgotten. The port bit is
certainly interesting.

Sam

--
601


  #16   Report Post  
Sam Bond
 
Posts: n/a
Default Battery powered amplifier from car speakers and booster amp?

On Fri, 23 Jan 2004 13:43:14 -0000, "Fergal" wrote:


I found some useful stuff on making fibreglass speaker enclosures and other
aspects of car hifi which would be applicable to you he

http://www.jlaudio.com/tutorials/index.html


Yes, thanks. I'd looked at it some time ago but had forgotten. The port bit is
certainly interesting.

Sam

--
601
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