better use a low quality woofer that will come very cheap(it costs less than 1/3 of $ here in INDIA)
one thing that u must take care of is that the speaker resistance changes dynamically with the signal applied and only under those conditions can the amp paint the true picture in front of u about its performance.
so i will advice u to apply low freq. signal to amp i/p n drive up a cheapo woofer from it and do whatever tests u wanna do.its the best method ,using power resistors is like playing with amp in the name of testing.
but if still u prefer resistance then use heater coils(4 or 5 of them in series) to get the desired load. resistance will change with temp[change in r= r(at room temp)*a(coeffecient)*t(change in temp)]
with power applied by amp the resistance will change dynamically and will most appropriatlly represent a speaker.
i think u got my point here.
---------------------------------------------------------------
long live diyaudio for its existence
one thing that u must take care of is that the speaker resistance changes dynamically with the signal applied and only under those conditions can the amp paint the true picture in front of u about its performance.
so i will advice u to apply low freq. signal to amp i/p n drive up a cheapo woofer from it and do whatever tests u wanna do.its the best method ,using power resistors is like playing with amp in the name of testing.
but if still u prefer resistance then use heater coils(4 or 5 of them in series) to get the desired load. resistance will change with temp[change in r= r(at room temp)*a(coeffecient)*t(change in temp)]
with power applied by amp the resistance will change dynamically and will most appropriatlly represent a speaker.
i think u got my point here.
---------------------------------------------------------------
long live diyaudio for its existence
Hi sagarverma,
I understand where you are coming from, but only if everyone is using the same speaker is that testing valid. When the speaker ages, things will change so you have no reference. So "real world" means nothing. It's more, amp response on THIS speaker only.
The dummy load will provide measurements that can be compared over time and all over the world. That's why we use them.
-Chris
I understand where you are coming from, but only if everyone is using the same speaker is that testing valid. When the speaker ages, things will change so you have no reference. So "real world" means nothing. It's more, amp response on THIS speaker only.
The dummy load will provide measurements that can be compared over time and all over the world. That's why we use them.
-Chris
anatech
i use power oscilloscopesand signal generators to measure the response of any amp that i build. using power resistance is an ineffecient way of testing an amp(if u have read my post carefully)
its the reason y i adviced him to use a woofer and that too cheappo or second hand or so(y use a new and expensive one for testing) bec these,even if they sound horrible,will present the actual load that the amp will experience in day to day use and not the constant resistance that "WE" use.
use woofer bec:
1)will present "TRUE" load.
2)can tollerate high power surge unlike other drivers.
use heater coils bec
1)resistance changes with temp as rapidly as the res. of a speaker changes during reproduction of sound
2)cheap
avoid power resistance bec:
1)faux load for amp
2)can go dead leaving u stunned😱
3)costly
best method :get access to oscilloscopes etc and do pro like testing
-------------------------------------------------------------
the great divide,continues.
i use power oscilloscopesand signal generators to measure the response of any amp that i build. using power resistance is an ineffecient way of testing an amp(if u have read my post carefully)
its the reason y i adviced him to use a woofer and that too cheappo or second hand or so(y use a new and expensive one for testing) bec these,even if they sound horrible,will present the actual load that the amp will experience in day to day use and not the constant resistance that "WE" use.
use woofer bec:
1)will present "TRUE" load.
2)can tollerate high power surge unlike other drivers.
use heater coils bec
1)resistance changes with temp as rapidly as the res. of a speaker changes during reproduction of sound
2)cheap
avoid power resistance bec:
1)faux load for amp
2)can go dead leaving u stunned😱
3)costly
best method :get access to oscilloscopes etc and do pro like testing
-------------------------------------------------------------
the great divide,continues.
What about using a 4 ohm speaker coil from an old speaker, inside tupperware container, immersed in water?
I would think that would be the closest thing to a real speaker for testing.
I would think that would be the closest thing to a real speaker for testing.
water(bec of the impurities in it) will conduct current.speaker coils are isulated wires.y put them in water .let them outside
*I make sure that the water does not make contact, but even if it did, water is a few KOhms, I doubt it would even make much difference.
But the real point was, what about using a speaker coil to simulate a speaker electrically?
But the real point was, what about using a speaker coil to simulate a speaker electrically?
hi eworkshop
i was not talking about the resistance of water but that it will short the
coil and it can look very impressive if u see it go off.
to know if the coil can be used as a load u have to know that how does the speaker resistance change dynamically.for that search on google about workin of speakers so u will know that this is not an ideal solution
i was not talking about the resistance of water but that it will short the
coil and it can look very impressive if u see it go off.
to know if the coil can be used as a load u have to know that how does the speaker resistance change dynamically.for that search on google about workin of speakers so u will know that this is not an ideal solution
Hi sagarverma,
All due respect, but .... I've been working in the "Pro" end for over 20 years. Any more reference to this and I'll throw up on my computer.
In the (Arrrrgh
) "Pro" market, as well as the high end audio market, and the volume market the 8 and 4 ohm dummy load is the recognised standard. PERIOD. If you wish to test with something else, that is fine. When you report your specs to others, it will be in reference to a 4 and 8 ohm standard dummy load. You may use a 2 ohm standard, but that's not as common.
I can't help but notice that a few people in your country are hung up on the use of the "Pro" word as a way of lifting your experiences above others. You are showing some contempt and lack of understanding to others in the field. An amp is an amp is an amp. If your practice is to horribly abuse them - fine. You are setting up special circumstances that are beyond good engineering practices. Don't belittle designers who follow accepted norms.
Now, I take your point about amplifier testing. There are published dummy loads that include inductance and capacitance to throw the phase angles around. Use one of those instead of an unknown. To add, I think we are intelligent enough to know when a dummy load is overheating. That happens before it fails.
So let us talk about amplifiers, not some special magically infused creations that can only come to be in your particular country. Remember to there is much more experience across the globe than can exist in one contry. Don't insult them - please.
-Chris
All due respect, but .... I've been working in the "Pro" end for over 20 years. Any more reference to this and I'll throw up on my computer.
In the (Arrrrgh
) "Pro" market, as well as the high end audio market, and the volume market the 8 and 4 ohm dummy load is the recognised standard. PERIOD. If you wish to test with something else, that is fine. When you report your specs to others, it will be in reference to a 4 and 8 ohm standard dummy load. You may use a 2 ohm standard, but that's not as common.I can't help but notice that a few people in your country are hung up on the use of the "Pro" word as a way of lifting your experiences above others. You are showing some contempt and lack of understanding to others in the field. An amp is an amp is an amp. If your practice is to horribly abuse them - fine. You are setting up special circumstances that are beyond good engineering practices. Don't belittle designers who follow accepted norms.
Now, I take your point about amplifier testing. There are published dummy loads that include inductance and capacitance to throw the phase angles around. Use one of those instead of an unknown. To add, I think we are intelligent enough to know when a dummy load is overheating. That happens before it fails.
So let us talk about amplifiers, not some special magically infused creations that can only come to be in your particular country. Remember to there is much more experience across the globe than can exist in one contry. Don't insult them - please.
-Chris
sense of dejavu
Hmmmm I seem to recall I've been down this path before 😉 ---> http://www.diyaudio.com/forums/showthread.php?s=&threadid=27364&highlight=
I ended up getting some 100W 8 Ohm non-inductive dummy loads from WES for about $18 each (the 4 Ohm ones are $14 each). They work nicely and didn't break the bank 🙂
Tony.
Hmmmm I seem to recall I've been down this path before 😉 ---> http://www.diyaudio.com/forums/showthread.php?s=&threadid=27364&highlight=
I ended up getting some 100W 8 Ohm non-inductive dummy loads from WES for about $18 each (the 4 Ohm ones are $14 each). They work nicely and didn't break the bank 🙂
Tony.
Electrical shower resistance is made with thick wire, i use it coiled over ceramic RF
Insulator....or high voltage ceramic insulator.
I use it coiled, but inductance is smaller than 0.5 micro henries
It is cheap, can hold enormous power without melt or change resistance.
The problem is that this wire do not accept common solder...have to attach it into the amplifier output wiring using screw and nut. (nut beeing the screw counterpart, complement or the part to attach).
regards,
Carlos
Insulator....or high voltage ceramic insulator.
I use it coiled, but inductance is smaller than 0.5 micro henries
It is cheap, can hold enormous power without melt or change resistance.
The problem is that this wire do not accept common solder...have to attach it into the amplifier output wiring using screw and nut. (nut beeing the screw counterpart, complement or the part to attach).
regards,
Carlos
hello anatech
great respect 4 u
u r a pro.u have been in professional bussiness(not pro).u use dummy loads.i use cheap thingies that r specific to my country.our country's diy'rs use pro word to elliviate there level above others.and all the other things that u say we the people of this country do.
grave misconceptions stemming out of misplaced attention from discussing the topics out here in this great forum (that has helped spread the great subject of electronics) to engaging in country specific mud slinging.
b4 saying or writing anything please read the posts carefully.from your messages it seems u have totally ignored the written material and started your unwarranted barrage.i m rewritting summary for u expecting that u read it atleast.................................
the initiater of this topic asked for a load to test his amp.i advised him to u use power oscilloscope to test his amp(no use of 'pro' here) which i use for testing(i think thats not abuse of an amp if u please{u must be knowing it bec u had been in this bussiness for 20 years!}).
anticipating he didnt have one i advised him to go for something that can replicate true load to an amp closely like a woofer or a network.
my suggestions were directed to help him out and not to show off myself(as u say we all do)
when u r in this feild then spread the knowledge that u have .y get involved in filthy mud slinging that deviates the attention away from main topic.
plz dont repeat this kind of behaviour in any other forum
great respect 4 u
u r a pro.u have been in professional bussiness(not pro).u use dummy loads.i use cheap thingies that r specific to my country.our country's diy'rs use pro word to elliviate there level above others.and all the other things that u say we the people of this country do.
grave misconceptions stemming out of misplaced attention from discussing the topics out here in this great forum (that has helped spread the great subject of electronics) to engaging in country specific mud slinging.
b4 saying or writing anything please read the posts carefully.from your messages it seems u have totally ignored the written material and started your unwarranted barrage.i m rewritting summary for u expecting that u read it atleast.................................
the initiater of this topic asked for a load to test his amp.i advised him to u use power oscilloscope to test his amp(no use of 'pro' here) which i use for testing(i think thats not abuse of an amp if u please{u must be knowing it bec u had been in this bussiness for 20 years!}).
anticipating he didnt have one i advised him to go for something that can replicate true load to an amp closely like a woofer or a network.
my suggestions were directed to help him out and not to show off myself(as u say we all do)
when u r in this feild then spread the knowledge that u have .y get involved in filthy mud slinging that deviates the attention away from main topic.
plz dont repeat this kind of behaviour in any other forum
Hi sagarverma,
Please accept my appologies if I took your comments the wrong way. I'm sensitive to this from another forum member's comments.
In particular, this set me off ...
"Pro" testing does in fact use dummy loads, which may be in conjunction with inductors and capacitors. The key is that the load must be reproducible to be of any value to anyone. There seemed to be some acceptable, inexpensive options presented already.
I disagree with all of your points in this context. 'Scopes are expensive too, making your point #3 rather pointless to bring up. Proper dummy loads being the cheapest part of the process.
I do accept your load comments when it comes to doing a listening test. I feel that's important in any development work.
-Chris
Please accept my appologies if I took your comments the wrong way. I'm sensitive to this from another forum member's comments.
In particular, this set me off ...
"Pro" testing does in fact use dummy loads, which may be in conjunction with inductors and capacitors. The key is that the load must be reproducible to be of any value to anyone. There seemed to be some acceptable, inexpensive options presented already.
I disagree with all of your points in this context. 'Scopes are expensive too, making your point #3 rather pointless to bring up. Proper dummy loads being the cheapest part of the process.
I do accept your load comments when it comes to doing a listening test. I feel that's important in any development work.
-Chris
Actually there is no reason not to submerge a dummy load in de-ionized distilled water but thats the only kind of water than can be used. Many parts of high powered transmitters are cooled this way and de-ionized distilled water will not conduct electricity no matter what, some transmitters actually have entire circuits submerged!! Oil is more efficient and there is not an as big of an evaporation problem(but it still does evaporate) but at home the water thing will work just fine. Another reason oil is frequently used is for insulation purposes in high voltage power supplies. The oil has to be ultra pure though.
Mark
Of course, if you use oil, when you drain the fluid the connections will not corrode. With water you may want to dry your load as soon as you pull it out.
-Chris
-Chris
I use (4) EBG Brand, 4 ohm, series UXP 600 power resistors mounted on a heat sink. The four 600 watt resistors provide the flexibility of either (2) 8 ohm loads or (2) 4 ohm loads at the flip of a switch.
For large amplifiers I have a larger heat sink that holds (8) of these 600 watt resistors and is cooled by (3) 5 1/4" 85 cfm rack fans. I have never had a situation where the heatsink got hot enough that the fans couldn't handle it.
For a cost of $5 each for the resistors I didn't feel I could go wrong.
For large amplifiers I have a larger heat sink that holds (8) of these 600 watt resistors and is cooled by (3) 5 1/4" 85 cfm rack fans. I have never had a situation where the heatsink got hot enough that the fans couldn't handle it.
For a cost of $5 each for the resistors I didn't feel I could go wrong.
Actually birned fingers load is very similar to one that I used all the time at Midwest hi-Fi and similar to one that I am presently building. Only difference is mine has surplus Dale 8 ohm non-inductive resistors on it.
As for the oil, you'd also better wipe off any excess oil because it too will evaporate and leave a film of goo thats difficult to get off with out a tough solvent. The distilled water doesn'r effect ANY corosive action at all unless there be impurities in the striped wire itself that are released and mix with the water. Just another reason that its important to use silver plated teflon covered hook up wire. Or just seal up the connections!
Mark
As for the oil, you'd also better wipe off any excess oil because it too will evaporate and leave a film of goo thats difficult to get off with out a tough solvent. The distilled water doesn'r effect ANY corosive action at all unless there be impurities in the striped wire itself that are released and mix with the water. Just another reason that its important to use silver plated teflon covered hook up wire. Or just seal up the connections!
Mark
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