Is this resistor ok for a dummy load? |
Post Reply |
Author | |
TMH Music
Young Croc Joined: 07 April 2011 Location: London Status: Offline Points: 635 |
Post Options
Thanks(0)
Posted: 14 June 2018 at 11:51pm |
So I’m contemplating building a dummy load to test my amps with. Starting off small scale first, I’m aware that the Re of most 8 ohm speakers can be anything between 5 and 7 ohms (ish), but a fixed resistor won’t necessarily behave in the same way as a speaker, when asked to dissipate the output from an amplifier!! I’m thinking in terms of a modular setup using a number of these resistors:
Starting initially with 2, then going to 4 then 8 as funds allow, so I will be able to patch them in series/parallel to adjust resistance/power handling. I chose 10 ohm as I thought it would be a bit easier on the amp when spanking the nuts off it!! Your thoughts/advice please folks.
|
|
Nothing is foolproof because fools are so ingenious
|
|
Elliot Thompson
Old Croc Joined: 02 April 2004 Location: United States Status: Offline Points: 5172 |
Post Options
Thanks(0)
|
I use 4 ohm resistors as it is easier to configure (2,4 or, 8 ohms) and reflects the load the manufacture uses to measure their amplifier(s). Best Regards, |
|
Elliot Thompson
|
|
odc04r
Old Croc Joined: 12 July 2006 Location: Sarfampton Status: Offline Points: 5483 |
Post Options
Thanks(0)
|
Sure, they'll work. Being wirewound they'll offer a slight inductance which slightly helps to mimic a voicecoil too. Mount them safely and away from your work area if you're doing high power testing is all I'd suggest. On something flameproof preferably.
|
|
Earplug
Old Croc Joined: 03 January 2012 Location: Europe Status: Offline Points: 7199 |
Post Options
Thanks(0)
|
And stick in a fan or two as well. They can get hot. |
|
Earplugs Are For Wimps!
|
|
fatfreddiescat
Young Croc Joined: 15 October 2010 Location: N.E.Wales Status: Offline Points: 1081 |
Post Options
Thanks(0)
|
or just buy some electric kettles, should be part way to a cuppa tea with decent amp when ur done.
|
|
studio45
Old Croc Joined: 16 October 2007 Location: United Kingdom Status: Offline Points: 3863 |
Post Options
Thanks(0)
|
I used to recommend electric kettles - buuuut, they change resistance quite a lot as they heat up. You'd want to have them hot before you start, and you'd have to measure their actual resistance at temperature to have any idea of how much power you are actually delivering.
There are some good looking 1kW "braking resistor" units on eBay for about £25, that come in 2, 4 and 8 ohm flavours, and are encased in an aluminium heatsink. I think they would work well, unless anyone wants to correct me?
|
|
Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
|
|
TMH Music
Young Croc Joined: 07 April 2011 Location: London Status: Offline Points: 635 |
Post Options
Thanks(0)
|
Thanks for the replies folks. @Studio45, did you mean these resistors on the bay:
They look quite the bargain, 1Kw wire wound, easy mounting for less than £25 a piece!!! Are the ones I linked to from RS that much better? Is it a case of you pays your money you takes your choice? Is it just that the eBay ones are the resistor equivalent of QTX? Am I asking too many questions?!! (Probably) Hmmm What are the collective’s thoughts??
|
|
Nothing is foolproof because fools are so ingenious
|
|
Pinyorouk
Young Croc Joined: 31 January 2011 Status: Offline Points: 550 |
Post Options
Thanks(0)
|
I used stove elements from ebay. Not exactly multiples of 4 ohms but sufficient for load testing amps.
|
|
ceharden
The 10,000 Points Club Joined: 05 June 2005 Location: Southampton Status: Offline Points: 11776 |
Post Options
Thanks(0)
|
I would go with the open wirewound style as per the original post. The advantage of those is that they have massive short term overload capability. You can pretty much run them glowing red hot!
Stick them in a case with some big fans.
|
|
mini-mad
Old Croc Joined: 13 July 2012 Location: london Status: Offline Points: 6903 |
Post Options
Thanks(0)
|
.... or a tub or oil(?) Used to do something similar Emersing motherboards with overcooked (pun intended) processors and would run warm enough to almost cook chips (2nd pun fully intended) |
|
If it sounds like a gorilla is trying to escape, turn it down.
|
|
ceharden
The 10,000 Points Club Joined: 05 June 2005 Location: Southampton Status: Offline Points: 11776 |
Post Options
Thanks(0)
|
Oil is messy but you could if you wanted.
Edited by ceharden - 16 June 2018 at 10:55pm |
|
gen0me
Young Croc Joined: 20 February 2016 Location: UK Status: Offline Points: 999 |
Post Options
Thanks(0)
|
You can just buy resistive wire. Find inductance calculator on web. Wire part of the wire to get the right inductance. Rest of the wire wound with half circles one direction half reverse so you wont get inductance like this.
|
|
I appreciate every like :)) https//www.facebook.com/genomesoundsystems
Mixes: https://www.mixcloud.com/gen-ome/ |
|
Post Reply | |
Tweet |
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |