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 Sick of over priced extention speakers from the big three. 
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Post Sick of over priced extention speakers from the big three.
£200 for Kenwood's top of the line extension speaker!! Even the crappy tin box with a 5 watt speaker in it is £70!

Where do they get these prices? They're not even active speakers.... just passive.

Sod that.... we're amateurs.... Time to build!!

Requirements: Self contained and amplified (mains operated).. class A amp.... at least 5 watts RMS not the strangled 5 watts peak most radio manage to wheeze out.... decent 2 way driver system... Passive input mixer for 5 inputs... Looks cool, and sounds fab.

Like any self-respecting ham... it starts with a pen...

Attachment:
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As it will be amplified and mains operated, it starts with a quick sketch for a variable supply as a starting point.



Added over voltage protection when I took it into a CAD program.. nothing fancy... just a SCR crowbar and fuse (T1 and D3)... nothing digital/sensitive in this, so perfectly adequate. Designed using bits and pieces lying around the shack, hence some components well over specified... but that's only ever a good thing. Added a soft start circuit too (Q1)

Attachment:
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PCB designed in Eagle.

Attachment:
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v4 colour.jpg [ 207.65 KiB | Viewed 2909 times ]

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Last edited by G0SLV on Sun Jul 09, 2017 7:57 am, edited 2 times in total.



Sun Jul 09, 2017 7:45 am
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 Sick of over priced extention speakers from the big three. 
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Post Re: Sick of over priced extention speakers from the big thre
Artwork ready for toner transfer

Attachment:
psu v3.jpg
psu v3.jpg [ 138.6 KiB | Viewed 2908 times ]


Silk screen layer.

Attachment:
psu v3 silk.jpg
psu v3 silk.jpg [ 104.61 KiB | Viewed 2908 times ]


Keeping the PSU seperate, as if I decide to scrap the speaker at some later stage, I've already got a variable voltage PSU built for another project.


Will post up the amp circuit later... basically a 10 watt class A amp using a darlington pair... Yes, I know class A is wasteful, but so what.... I've got loads of heatsinks lying around :)


If anyone spots anything scary I've missed.. feel free to call me an idiot :)


Attachments:
psu v3 silk.jpg
psu v3 silk.jpg [ 104.61 KiB | Viewed 2908 times ]

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Sun Jul 09, 2017 7:49 am
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 Sick of over priced extention speakers from the big three. 
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Post Re: Sick of over priced extention speakers from the big thre
I agree on the prices.

Did something similar, but has a 10+10W stereo amp, and 6 inputs. The selected input goes through a DSP noise reduction unit to the one amp, with a 3 channel tone control. The 5 unselected channels go through a mixer to the other channel, with a rear mounted speaker. This means you can hear what is on the other rigs in the background, and switch to that rig if desired.

Used a cardboard carpet roll with the back baffle adjustable, and the outside covered in bitumen sound deadening then plywood.

The electronics are mounted in an aluminium enclosure that forms its base.

Uses a Wharfdale 4" mid-range driver

I will be getting it down at the beginning of next month, it was part of a system that switched speaker, mic, PTT and antennas from one box on the table. Decided I want it back in use again.

I want to add a DSP bandpass filter ahead of the DSP noise reduction unit, it makes a big difference to performance.


The whole thing won't have cost me £200, but the results make the £200 speaker sound like a £1 from poundland :)

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Sun Jul 09, 2017 8:52 am
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 Sick of over priced extention speakers from the big three. 
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Post Re: Sick of over priced extention speakers from the big thre
Here's the design for the amplifier.


Attachment:
45g44rtg4.jpg
45g44rtg4.jpg [ 90.86 KiB | Viewed 2846 times ]

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Sun Jul 09, 2017 2:08 pm
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 Sick of over priced extention speakers from the big three. 
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Post Re: Sick of over priced extention speakers from the big thre
Just finished making the printed circuit boards.

Amplifier copper side.

Attachment:
_DSC9606.jpg
_DSC9606.jpg [ 213.45 KiB | Viewed 2846 times ]


Amplifier top side.

Attachment:
_DSC9603.jpg
_DSC9603.jpg [ 208.13 KiB | Viewed 2846 times ]

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Sun Jul 09, 2017 2:10 pm
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 Sick of over priced extention speakers from the big three. 
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Post Re: Sick of over priced extention speakers from the big thre
PSU printed circuit.

Copper side.

Attachment:
_DSC9605.jpg
_DSC9605.jpg [ 185.2 KiB | Viewed 2846 times ]


Top side.

Attachment:
_DSC9604.jpg
_DSC9604.jpg [ 187.63 KiB | Viewed 2846 times ]

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Sun Jul 09, 2017 2:11 pm
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 Sick of over priced extention speakers from the big three. 
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Post Re: Sick of over priced extention speakers from the big thre
Nice work Dave, I like the DIY silkscreen too - did you use the toner transfer system for that?


Sun Jul 09, 2017 5:13 pm
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 Sick of over priced extention speakers from the big three. 
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Post Re: Sick of over priced extention speakers from the big thre
2E1IIP wrote:
Nice work Dave, I like the DIY silkscreen too - did you use the toner transfer system for that?



Yes... both sides using toner transfer. I use a modified laminator and Pulsar FX transfer paper and a TRF foil coating prior to etching to avoid pitting. You can also use the TRF foil to go over the silk screen to make it any colour you want... but I actually prefer to leave it bare toner black.

I also get better results with thinner materials, so 0.8mm boards are used here. Perfectly fine unless you want to make something really big... in which case it wouldn't fit through the laminator any way. For big stuff, I'd still use the traditional photo resist method. It's rare I make anything that requires a big board though.

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Mon Jul 10, 2017 6:46 am
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Post Re: Sick of over priced extention speakers from the big thre
Sangoma wrote:
I agree on the prices.

Did something similar, but has a 10+10W stereo amp, and 6 inputs. The selected input goes through a DSP noise reduction unit to the one amp, with a 3 channel tone control. The 5 unselected channels go through a mixer to the other channel, with a rear mounted speaker. This means you can hear what is on the other rigs in the background, and switch to that rig if desired.

Used a cardboard carpet roll with the back baffle adjustable, and the outside covered in bitumen sound deadening then plywood.

The electronics are mounted in an aluminium enclosure that forms its base.

Uses a Wharfdale 4" mid-range driver

I will be getting it down at the beginning of next month, it was part of a system that switched speaker, mic, PTT and antennas from one box on the table. Decided I want it back in use again.

I want to add a DSP bandpass filter ahead of the DSP noise reduction unit, it makes a big difference to performance.


The whole thing won't have cost me £200, but the results make the £200 speaker sound like a £1 from poundland :)



We need piccies :)

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Mon Jul 10, 2017 6:51 am
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 Sick of over priced extention speakers from the big three. 
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Post Re: Sick of over priced extention speakers from the big thre
Here are the drivers I'm using.

Celestion 4.5" bass/mid driver... and a Fane 1" dome tweeter. Both 8 Ohms.

Both are rated 60 watts RMS. Again, total overkill, but it's no cheaper buying lower rated speakers of this size, and it rules out a source of distortion. The amp will have extreme headroom in which to work.


While it may seem like over kill to have a 2 way system, I wanted it for listening to broadcast stations as well. I don't see the point in having speakers "tailored" for speech as there are plenty of options to do that on the radio if you want. Always best to have a wide, flat response speaker.. uncoloured and transparent in nature. These "filters" on some of the big three speakers are just a waste of time, and are nothing but switched in EQ settings using simple X-over components. Pointless.... much better to use the radio's controls to tailor the sound... plus... as this has multiple inputs (I decided on three inputs, not 5, as those eagle eyed amongst you may have noticed from the amp schematic), having the speaker change the sound will affect all the radios attached to it... which is terrible if you think about it. This will be more of an active studio monitor than a communications speaker.

Attachment:
19264542_872572986229002_1066375337163409948_o.jpg
19264542_872572986229002_1066375337163409948_o.jpg [ 152.83 KiB | Viewed 2773 times ]

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Mon Jul 10, 2017 7:07 am
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Post Re: Sick of over priced extention speakers from the big thre
I did not realise that you could get TRF foil, I was plagued with pitting after etching and wondered how you pulled that finish off.
Just ordered 15 feet of it for £11 delivered :thumbsup:
You can get the white foil too and use that for the silk screen, I will give that step a miss for now as I am happy enough following a silkscreen printout as a guide.

Thanks for the tips Dave.

Best

Rob.


Mon Jul 10, 2017 3:41 pm
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Post Re: Sick of over priced extention speakers from the big thre
2E1IIP wrote:
I did not realise that you could get TRF foil, I was plagued with pitting after etching and wondered how you pulled that finish off.
Just ordered 15 feet of it for £11 delivered :thumbsup:
You can get the white foil too and use that for the silk screen, I will give that step a miss for now as I am happy enough following a silkscreen printout as a guide.

Thanks for the tips Dave.

Best

Rob.



You're welcome Rob,

Can you give me a link to where you got your foil from? It was cheaper than mine!

[edit]

LOL.. forget that request... I actually didn't realise it was 15ft! For some reason I was only paying attention to the width.



Cheers

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Mon Jul 10, 2017 9:32 pm
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Post Re: Sick of over priced extention speakers from the big thre
Oh.. one thing Rob.... That foil always sticks to everything... not just the toner. Don't panic if you get a totally green board. Use a plastic pencil eraser (not a rubber one) and it rubs the TRF off the bare copper really easily. Watch you don't rub right through though. Showing a little black through it is OK, but be careful.

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Mon Jul 10, 2017 9:39 pm
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Post Re: Sick of over priced extention speakers from the big thre
Thanks for the tip on the rubber - I did not know you could get plastic erasers, just looked on Ebay and you can get them in a pack of 5 for a few quid so just ordered some.
I have a couple of boards to do at the weekend so will be good practice for me :)
Have you found a suitable case for your amplified speaker yet? Are you going to use a wood cabinet with some nice black carpet trim or a metal enclosure?


Tue Jul 11, 2017 8:19 am
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Post Re: Sick of over priced extention speakers from the big thre
2E1IIP wrote:
Thanks for the tip on the rubber - I did not know you could get plastic erasers, just looked on Ebay and you can get them in a pack of 5 for a few quid so just ordered some.
I have a couple of boards to do at the weekend so will be good practice for me :)
Have you found a suitable case for your amplified speaker yet? Are you going to use a wood cabinet with some nice black carpet trim or a metal enclosure?



I'm making it out of 6mm MDF... not sketched anything yet, but it will be essentially 12" wide, 6" high, and 10" deep... which gives me the correct internal volume for the bass driver using Theile-Small parameters. The top and bottom edge will be rolled. When built, sanded, etc... I'm going to practically encapsulate it in yacht varnish, then wet and dry it to a mirror smooth finish... prime it... flatten it... then it will be painted "Kenwood" grey. The speakers will be front mounted and left bare.. on show. A black anodised anti-vandal switch for on/off and a blue power LED will be the only other things. The back panel will have a connector plate for 3x mono phono connectors for input, and a standard 2 pin mains connector. As it will essentially be double insulated (It's wood) there's no need for an earth.

It will just look like a classy, minimalist studio monitor. :)

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Tue Jul 11, 2017 8:35 am
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