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Why 4 Ohm Loads Stress Your Amplifier

To people looking for cooling solutions: try frozencpu.com
It's a site for computer cooling. For fans, I would look for a 120mm fan (big and quiet) with a db rating around 20. For heatsinks, you could use memory heatsinks (AKA ramsinks) or a northbridge / southbridge heatsink for more intense applications. Pick up some thermal epoxy and you're all set!

Heatsinks: http://www.frozencpu.com/cat/l3/g40...Coolers-FanlessPassive-Page1.html?o=price_asc

Fans (12v / 5v DC, 115v AC): http://www.frozencpu.com/cat/l1/g36/Fans.html

If they can cool my computer, they can cool your amp!
 
Speaker Impedance

Great thread! This confirmed what I knew about my SX-1250 and answered any grey areas I had. I am sure for many other AKer's also. Many a time I seen posts on "Can I run 2 sets of 4 ohms....". Wish they would stop by here first and their question would be answered. Thanks much!:tresbon:
 
I have run a pair of 8 ohm speakers in parallel, thus making a 4 ohm load, as the center channel on my pioneer VSX-517 HT receiver. I definitely noticed a heating issue after extended use or even a relatively small period of high volume.

This thread certainly explains why this happens, I should be fine as long as I keep an eye on the heating, yes?.

Thanks for the info :scratch2:
 
Harmonica said:
....

This thread certainly explains why this happens, I should be fine as long as I keep an eye on the heating, yes?.

Thanks for the info :scratch2:
Click to expand...

Which speakers for your mains/surrounds/centers? Remember that nominal Ohm rating is not always so helpful. All speakers I know of vary, it's a range not a simple static measurement. (never seen a totally flat impedence curve either.)

Not familiar with that receiver's specs, don't have those, current draw can give a little insight, amperes on the fuses too... some HT receivers grant smaller allocations to the non-mains, so...

Using only one center channel and boosting its volume instead of using 2 has another benefit. Less smearing of the 3-D image.
 
Pioneer vsx 517 specs:

110 Watt - 8 Ohm - THD 0.9 % - 2 channel(s) ( Front )
110 Watt - 8 Ohm - THD 0.9 % - 2 channel(s) ( Surround )
110 Watt - 8 Ohm - THD 0.9 % - 1 channel(s) ( Center )

speakers as follows:
Fronts: Cerwin vega d-5's, 5/150 watts (min/max) 32hz-20khz 8ohm

Center: 2 3-way Optimus sts-100's in parallel, 5/100watts (min/max) 60hz-20khz 8ohm

Surrounds: Pioneer S-H152B, pretty much same specs as the optimus (but sound better :D) and are 2 way

So, one speaker as the center would be better for image and probably better for my receiver...I have a set of old 3 way floor standing fishers with its 12in woofer replaced by a Onkyo driver, I dont know the specs on them but they are rated at 8ohms. I used to run them as fronts until I got my D-5's, perhaps one of these would be a better option for a center, it would come closer to matching the fronts at least.
This issue has been irking me for a while I just never asked about it, thanks for any input :thmbsp:
 
I believe I read (here) that my NAD 2400 THX power amp is a rare exception in that it's not expensive and can handle loads down to even 2 ohms.

I also just read here in this thread:

"If the amp is rated for 8 ohm's min, when using a and b you must use 16 ohm speakers. Some amps/receivers series (for the lack of a better term) the out puts. You can tell by switching your selector to a+b with speakers only connected to a. If you lose audio they are seriesed. If you do not, parallel.
If rated for 4 ohm on a parallel a+b must be 8 ohm. =4 ohms."


I have yet to determine if my NAD runs series or parallel--I'll go home and perform the "test" by disconnecting the "B" side of speaker cables and then select "A" and see if I still have sound.

If I understand correctly, if I in fact have a series connection, then it doesn't matter about mixing/matching speaker ohms?

I really need to find out because I am running a large 4 ohm tower set And a small unknown ohm rating set across the room--I always thought this freakish NAD could handle it, but this morning for the first time in over 10 years the red Overload light came on and stayed on. The unit performed fine and after a few seconds the light went out, but I wonder if this is a warning sign of bad things to come?
This has been said before.
 
Down-to-Earth Real 4 AMP Question! How Do I Make It Work

Wow. What a bunch o' propeller heads! Cool. You guys should be able to whip up an answer for me!

I love the old vintage stuff. I collect all sorts of crap from bygone days. I've got an old panasonic/techniques receiver (someone has a picture of it down the replies) that just sa-mokes! up at my cottage.

A buddy gave me a Nikko Alpha 130 pre-amp with a Nikko Beta 30 amp and then I found another more better version at the Goodwill (for about $15!) a Nikko Alpha 220. It's a bout 90 better than the 130, eh? Just kidding, but that's about the limit of my stereo expertise.

Problemo Numero Uno

My Alpha 130 has a built in fuse that pops all the time, until the unit heats up. Any suggestions/worth fixing?

Problemo Number Duo

Another friend gave me a nice sub-woofer, (He used to work in a stereo shop) from his car, that is obviously, 4 Ohm.

How do I run it on my 220? Id est, hook it up?


(I tried combining A + Right side/leftside and A - Rightside/leftside to the proper terminals to the sub in order to share the sound from either side to the sub woofer (since it was stereo) and it worked for a while, then the fuse clicked in to stop whatever I was doing. It's why I'm looking to you fellers!)



On the back of the 130, this is written

A or B 4 Ohm-6 Ohm 8 Ohm- 16 Ohm per speaker

A and B 8 Ohm- 16 Ohm per speaker

And a little push button on the back to select either 4-8 Ohm or 8 -16 Ohm

On the Alpha 220, there is no switch but same written instruction.

I obviously bobbled the instructions. Big surprise there, eh!

How do I hook up the sub-woofer, or should I just quite being so cheap, and go and buy a nice thumpy one (Any recommendations?)

Thanks guys.

Oh, and one more thing. The guy who gave me the Alpha, gave me a set of JBL TLX8 speakers. They sound good. One of them has no treble sound. The crossover is shot? Fixable? Can I just buy a new one somewhere? They look cheap.

Again, many thanks,

SweetDoug
 
DSB123 said:
To people looking for cooling solutions: try frozencpu.com
It's a site for computer cooling. For fans, I would look for a 120mm fan (big and quiet) with a db rating around 20. For heatsinks, you could use memory heatsinks (AKA ramsinks) or a northbridge / southbridge heatsink for more intense applications. Pick up some thermal epoxy and you're all set!

Heatsinks: http://www.frozencpu.com/cat/l3/g40...Coolers-FanlessPassive-Page1.html?o=price_asc

Fans (12v / 5v DC, 115v AC): http://www.frozencpu.com/cat/l1/g36/Fans.html

If they can cool my computer, they can cool your amp!
Click to expand...

I second the use of computer 12V DC fans for cooling. From PC experience I can say that you should ignore manufacturer specs for sound and somewhat for CFM, there are no standards in those measurements and some makers like SilenX basically lie about their fan ratings. In my experience with 120mmx25mm fans an 800RPM one will be virtually inaudible from a few feet and a 500RPM one silent even closer. Most can be downvolted too, just watch out because some refuse to start when downvolted too much and sometimes the motors make odd and annoying sounds. Sleeve bearings are more likely to wear out sooner although they can run for years but are cheaper. Noctua and Scythe S-Flex are good long-duration bearing units, the Scythe Slip Streams move more air at a given RPM = more air per dB, and Yate Loons are good if you just want something cheap but decent. Silentpcreview.com is a good place to read up on various fans if you're worried about the noise.
 
okay...all very interesting..how about adding a 4-ohm resistor to a 4 ohm speaker,. wont that allow safe use with a decent amp/receiver made for an 8 ohm load? doesnt matter which side of the connect the resistor is placed in line does it?
 
You'll need a high power noninductive resistor, and while it will solve the impedance problem, it will do it at the expense of turning half your amplifier's power into heat (hence the need for a high power resistor), and it wil screw up the damping of the amplifier/speaker system.
A complicated way of making a system less efficient and boomier.
 
ok I think I get it but, still not sure, is it ok or will it hurt my Setton 220 to drive my JBL 12" sub. It has dual voicecoils @ 4 ohms each. It sounds pretty good but would hate to hurt such a nice receiver.
 
If you'll be running the sub alone with no other speakers attached, it will be too low of an overall impedance. If using speakers in addition, you're asking for disaster.
 
rabbit said:
For a better understanding of the relationship between the load impedance and the amplifier please read the following article that appeared in Stereophile.

http://www.stereophile.com/reference/707heavy/index.html
Click to expand...

Thanks for the link rabbit, very interesting article. You would think that loudspeaker manufacturers would take more account of the load their products impose on amplifiers, especially if an easy to drive load resulted in the amplifier (and therefore the speakers) sounding better.

- Richard B.
 
You would think that, but speakers are awkward things, and in the quest for the best sound, its very possible to create a load that is so difficult for an amp to handle that only specific amps can drive them successfully. These amps are often monsters that are so overbuilt (and expensive) that they are not bothered by close to a dead short at certain frequencies -- one thinks of the combination of Wilsons and Krells or Madrigals and so on. This is part of the reason for one of the annoying features of the real high end, which is how system dependent everything is, and how speakers go from being the greatest in the world to being not very good, depending on what they are being driven with. No wonder the world thinks we're nuts. For thousands of dollars, most people would expect a speaker or an amp that was good in all situations.

But to a specific application -- why would a 4 ohm driver be a disaster for the Setton? I don't know if he is running the two voice coils in parallel off on channel (and that's a bad idea) but the Setton ought to be able to handle a 4 ohm load no problem
 
Thank you for all the input. I am running each voice coil to sepperate channels, i.e. one to the right and one to the left. The setton does get warm but not overly hot,and let me tell you I drive it pretty hard, that JBL just thumps like crazy!
 
Does anybody have a procedure for measuring the reactive component of a speaker load as a percentage of the resistive component? That could make the graphs here a lot more practical and reliable to use as a standard. ?
 
Keperkara said:
Does anybody have a procedure for measuring the reactive component of a speaker load as a percentage of the resistive component? That could make the graphs here a lot more practical and reliable to use as a standard. ?
Click to expand...

CLick on 117 (speaker parameter calculations) on the right side of the site below. The various resistor voltage readings will help you establish the reactance of your speaker at various freqs.

http://www.bcae1.com/
 
Good job 240. I believe you are spot on. I have had problems with my onkyo running infinity qb's. They are 4ohms. It has always produced alot of heat. With two breakdwns. Now I am trying to find a preamp board.
 
EchoWars said:
...also consider that, although at half-power, that's only 3db down from full output, and still way beyond a 'normal' listening level for most.

Most amps don't have a problem with 4 ohms at reasonable listening levels, 'reasonable' meaning 10W and under. At the highest listening levels the culprit is current (with high dissipation being a byproduct of that). Continuous listening at high levels with a low impedance load should be done with an amplifier designed to do just that (and if you have to ask 'can my amp do this?', then the answer is probably 'no'), but for normal listening it likely isn't a problem.

You're on the right track and I see no reason to pick your argument apart. Nice work.
Click to expand...


This is a little confusing to me if I may...if I am running a pair of AR3a 4 ohm speakers, will my SX 1980 have an issue pushing this load? Am I running a risk of damaging the amp?

m
 
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