Change ohms setting? (1 Viewer)

[JaykohZ51]

Hey guys. New member here.

I have a Marantz 7012 with ML motion 40s, 30 and FX on their way to me. All the speakers are 4ohms. I was reading thru the 7012 manual...the default setting is 8ohms. The manual says to manually change the setting if a speaker is 6ohms or below. 8, 6, and 4ohms settings are available.

Is this something that you guys recommend? Does it matter?

I have a 5010 running ML motion 4s and a motion 8 center but never changed the ohms. Seems to be running fine.

Thanks in advance.

Jake

 

[JohnRice]

Lowering the Ohm setting will reduce the power, but protect the receiver from overheating and extend its life. I'd probably set it to 6 Ohm, but when you play it loud, see if it gets hot. If it does, then I'd set it to 4 Ohm. If you want maximum life from the receiver, then you might just want to set it to 4 Ohm to begin with, but it will reduce how loud you can play it.

You can always use an external amp that can handle 4 Ohm with no problem, but it's not necessary. It would just eliminate any doubt and risk of shortening the life of the receiver.

 

[JaykohZ51]

I don’t go crazy loud...enough to feel it tho. But, these are all brand new items to me. I’ll have to play with the settings.

I was concerned with damaging the speakers. Lol. Didn’t think about the receiver’s temps. It’ll be well ventilated. Open rack.

Will sound quality be affected at all with each setting? Max volume I do is usually around 60 on my old Marantz 5010. I’m sure the volume threshold on the 7012 will be similar.

 

[JohnRice]

I suppose it might protect the speakers in some way, but it's mainly to protect the receiver. I don't know if it will affect the sound quality. It shouldn't, but it's actually possible it could improve it by using the correct Ohm setting. I would probably turn it down to at least 6 Ohm, just to protect the receiver.

 

[JohnRice]

Think of low impedance speakers like driving down a steep hill with bad brakes. Speakers resist the signal coming in. Most are 8 Ohm, but 4 Ohm gives less resistance which makes the amps in the receiver heat up. Lowering the setting on the receiver protects it by figuratively applying the brakes a little, all the time. to make sure it doesn't "lose control", which with an amp, means overheating. Higher operating temperatures shorten the life of electronics.

 

[JaykohZ51]

Definitely makes sense. Once I have it all hooked up, I’ll play with the settings to see if I hear a difference. But I like the “middle of the road” idea of 6ohms.

I can’t wait. Hopefully by the end of next week. All one shipment.

 

[gadgtfreek]

All lowering the ohm setting does is reduce rail voltage, leave it at the higher setting so you get full power. It is a BS move by AVR manufacturers.

The reduction in power, as proven in testing, by using the lower ohm settings is terrible. Audioholics have already written on this.

 

[JohnRice]

I think Jason is right. I'd forgotten what it does when you change the setting, which really doesn't address the problem. You still have 4 Ohm speakers and the amps just aren't intended to work with them. You could always use an external amp that is designed for 4 Ohm speakers, but you probably don't want to bother with that.

 

[gadgtfreek]

Yeah, their article is a good read and I had no idea about it until they wrote it. Your AVR will have thermal protection if you overdrive, but when you lower the rail voltage now you can present yourself with clipping and damage speakers.

https://www.audioholics.com/audio-amplifier/impedance-selector-switch-1

 

[JohnRice]

There's a lot of marketing BS in audio. Just like using multiple channels to "bi-amp" your speakers with a multi channel receiver. Say, for example, you're running 7 speakers and your receiver has 9 channels of amplification, sometimes you have the option of getting "more power" by bi-amping the main speakers. The problem is, if you're running out of power running 7 speakers, you're actually running out of power supply. Once you run out of power supply, there's no more power to be had from the receiver. If it does steer more power to the mains, it's only by taking it from the others. Most receivers can only drive two channels to the maximum the amps are capable of, and some can only drive one.

 

[gadgtfreek]

Yep, AVR's are bad about power ratings. I bought monitors from PSA that are a true 98dB sensitivity, my A3060 has no problem with them loud and clean.

If you have a power hog setup of speakers, just get a decent AVR with preamp outs, and get an Outlaw or Emotiva amp. Just my 0.02.

 

[JaykohZ51]

Gentlemen. Thank you for the intel. I’ll leave the ohm setting alone.

 

[Luke Cool]

I am an electronics technician. Almost all multi channel theater receivers are made (and set up) to drive a set of smaller type 8 ohm speakers. They are not power house amps that are drastically over made. Driving large, or 4ohm speakers on mid to high volumes will cause it to run hot. Heat is not your friend. Follow the instructions in your receiver's op manual, they are there for many good reasons.

I have a $1400 Onkyo receiver and a set of 6 ohm HPM 1100 Front speakers. It can not drive them correctly, along with the other 7 smaller type speakers I have connected to it. The bass is weak. I gave the HPMs their own separate amp, and they came alive. They now generate some bass that competes with some of the better subwoofers. Correctly managing your power will give you better sound. A couple of very small 4 ohm speakers will run fine on an 8 ohm amp, medium size ones will not. Look at the size, impedance, and number of speakers, and be smart about what you are asking your amp to do. Put 7 large 4-way, low impedance speakers on a receiver, it will sound like crap, and its heat sinks will glow in the dark.

 

[JohnRice]

I just want to point out the fact that just because a speaker is physically large does not in any way indicate it is difficult to drive. Actually, in very general terms, larger speakers tend to be easier to drive. I want to repeat, that is a generalization, but tends toward being true. Look at two speakers from the same line, with the same design, where one is a bookshelf and the other is floorstanding, the floorstanding one will almost always have higher sensitivity, at least a little bit. Small speakers almost always have lower sensitivity, which along with impedance, are the primary indicators of how difficult a speaker is to drive.

Having said that, it definitely is true that amps in receivers generally just aren't designed and built to the same level as most external amps. The interaction between a speaker and amp is a complex one, that goes far beyond just power output. The amp also controls the movement of the drivers, and better ones will have better control.

EDIT: So, back to the original question. Driving 4 Ohm speakers with receivers is a problem. Changing the Ohm setting in the setup menu will reduce or eliminate the possibility of the receiver overheating and can extend the life of the receiver. The problem is, it's a poor workaround and doesn't really address the actual problem, which is that receivers are rarely designed to drive 4 Ohm speakers. If you have 4 Ohm speakers, the only real solution is to use an external amp that's designed to drive them.

 

[Luke Cool]

I just want to point out the fact that just because a speaker is physically large does not in any way indicate it is difficult to drive.

Yes way! Normally, "larger" moves more air, does more work, and takes more power to do so. I do admit, what I said was a generalization, like generally, a 4 inch speaker is easier to drive than an 18 inch one. And most small cabinets with 2 speakers in them are easier to drive than a larger cabinet with 6 speakers. But I do agree that none of this is always true. The driver's coil size and composition, driver size weight suspension and design, servo controlled or not, magnet size and type, the crossover, number of drivers, cabinet size and design, and even how hard it is driven and what it is driven by, all play a part in how difficult the unit is to drive. If you want to really get technical, throw in each driver's reaction to the air's humidity and density, and room acoustics; generally, the environment they are used in.

It definitely is true that amps in receivers generally just aren't designed and built to the same level as most external amps. The interaction between a speaker and amp is a complex one, that goes far beyond just power output. The amp also controls the movement of the drivers, and better ones will have better control. Driving 4 Ohm speakers with receivers is a problem. Changing the Ohm setting in the setup menu will reduce or eliminate the possibility of the receiver overheating and can extend the life of the receiver. The problem is, it's a poor workaround and doesn't really address the actual problem, which is that receivers are rarely designed to drive 4 Ohm speakers. If you have 4 Ohm speakers, the only real solution is to use an external amp that's designed to drive them.

Well said. A theater receivers, being designed to be switched to drive 4 ohm speakers, is indeed a compromise. The problem is, driver loads are variable, fixed loads are not. The amplifier's feed-back, balancing, and filter circuits, are optimized for an 8 ohm driver load. I know how amps work, the switch has to somehow bring balance to the last stage of amplification. The switch probably adds 4 ohms (a fixed load) in line with the 4 ohm speaker to make it an 8 ohm load. This is not a best case scenario, and is something that I would advise trying to avoided.

I recently needed a better center speaker. Some speakers I looked at, had rave reviews, but when I found out that they were "4 Ohm", that was a deal breaker. Powered by the same receiver, when using 4 and 8 ohm speakers in a system, finding ones with a tonal and volume match is unlikely. I have some large vintage 4-way, 6 ohm front speakers with 15 inch graphite woofers. They have to be driven by a dedicated amp.

 

[JohnRice]

The switch probably adds 4 ohms (a fixed load) in line with the 4 ohm speaker to make it an 8 ohm load.

That would be a decent solution, except that's not what they do. They just reduce the rail voltage, thereby reducing the potential output and reducing the potential for overheating. Here's one problem with that solution. With a "perfect" amp, the available output at 4 Ohm would be double what it is with 8 Ohm. Such amps do exist. However, the amps in receivers are far from this idea of "perfect". So, let's say it can provide 100 watts at 8 Ohm, but being that it's not designed to drive 4 Ohm, it can only provide 120 watts at 4 Ohm. Then to protect from overheating with a 4 Ohm speaker, it cuts the rail voltage to where it only can provide half that. Now, with a 4 Ohm speaker, you've actually dropped your potential output to 60 watts, which protects the receiver from overheating, but increases the risk of damaging the speaker with distorted output. Add into the mix that low impedance speakers tend to also have lower sensitivity, and you're really screwed for power.

As far as the claim about large speakers, you're just wrong. It's not an absolute, because nothing is, but larger drivers, especially woofers, and larger cabinets with more internal volume tend to produce a more efficient speaker. Klipsch is the perfect example. Their Klipschorns are as big as a house, have enormous 15" woofers and are just about the most efficient speaker ever made. A very easy 8 Ohm and 105dB sensitivity. There's a reason so many people who own them use 10 watt tube amps to drive them. Look at the picture of them on the Klipsch site. Tube amp. 10 watts is more than enough. I'll just grab a random speaker out of the blue and make a direct comparison between different speakers in the same line. The ELAC Debut B4, a very small bookshelf speaker with a single 4" woofer. 84.5 dB sensitivity. Now to put that into real world numbers, the BigAsAHouse Klipschorns are over 100x more sensitive than the B4s. Meaning that 1 watt with the Klipsch = 100 watts with the B4s. Then go up to the biggest Debut speaker, the Debut F6, which has three 6" woofers vs one 4" woofer (same tweeter) in the B4. Now the sensitivity is 87dB. Impedance is the same. That might not sound like much, but it's almost twice as sensitive. 100 watts with the B4 is about the same as 60 watts with the F6. And that is how it is. Plain and simple.

 

[Luke Cool]

Thanks for the reply. Amplification takes several steps, each step uses a different voltage. To do a 50% steep down, you'd need to do a trick with transformer, like tap the windings midway. OR for the rail solution, two transformers would be needed, one to supply for the two rails. Both are a poor solutions. The reason amplification takes several steps is, it is an effort to keep each transistor in its most efficient range. Cutting their voltage in half changes this. The problem here is deeper than just half output.

And the power usage thing is not purely sensitivity. My HPM 1100s are 92.5dB/W, and believe me, they're power hungry. A dedicated amp makes a big difference in the way they sound. 125 watts is recommended. The interaction between a speaker and amp is complex, It goes far beyond just sensitivity. Not all 92.5dB speakers use the same amount of power, it's not at all that simple.

And "tube amps" are different than transistors, the force backing that signal is very powerful. That 10 watt tube amp can probably justly drive my HPMs.

 

[JohnRice]

I feel like I'm caught in a hamster wheel.

Did you ever consider that those speakers sound better with a better amp, because it's a better amp and it would make any speaker sound better?

Anyway, this discussion has already played itself out. I think I'll let the dizziness pass and move on.

 

[Luke Cool]

I feel your pain. I've put a fair amount of thought lately into what was said in this discussion, and here's what I've came up with.

The half power thing is a poor solution. Unless I see a schematic, I'll have to rely on your word. I think that the best solution is a switch that changes the circuitry to one that is balanced for that load on the last stage of amplification on whatever load is selected. Two separate last stages may be necessary for this. I also thought of over building the last stage to be bullet proof, but that would have distortion issues. For our purposes, we do both agree that it is to our advantage to stick with the load that our receiver is designed work best with.

Power used is a product of work done vs opposition. What you said does make some since, larger speakers should move air more efficiently. But I don't believe that it is to the extent that you purpose. Lower frequencies on larger speakers take more power to drive verses the same volume as higher frequencies on smaller speakers. A three way cross over gives the tweeter the least amount of power, and the woofer the most. Wire gauge usage and circuitry make this obvious. High wattage 5 inch speakers are called woofers, the lower wattage ones are called mid ranges. On the lower frequencies, when you can feel the air move, this takes a lot of power to do. This is why all great powered subwoofers have extremely powerful amps. If someone could make a great subwoofer with a ten watt amp, you'd see them everywhere.

I'm a military trained electrical technician. I worked on navigation and radar systems in jets, all the way down to repairing the circuit boards. I have a lot more than just a good feel for this type of stuff. I'm professionally trained with many years of experience.

 

[Luke Cool]

peace