What happens if I switch from 98 db sensitivity to 88?

[gnorthern]

I found a great deal on used speakers. The catch is they only have 88 db sensitivity, and the center channel is 87. I have a Marantz SR6013 receiver rated at 110 watts per channel. I almost never turn up the volume past a sustained 80 db volume (I use a meter). My seat is about 11 feet from the center speaker.

I have read several times that with a receiver like mine I should be looking at speakers with around 92 db sensitivity. Is that true?

Thanks for your answers.

 

[TLS Guy]

I found a great deal on used speakers. The catch is they only have 88 db sensitivity, and the center channel is 87. I have a Marantz SR6013 receiver rated at 110 watts per channel. I almost never turn up the volume past a sustained 80 db volume (I use a meter). My seat is about 11 feet from the center speaker.

I have read several times that with a receiver like mine I should be looking at speakers with around 92 db sensitivity. Is that true?

Thanks for your answers.

The db scale is log. So your receiver would have to produce 10 times the power to get the same loudness with the 88 db sensitivity speakers as the 98 db sensitivity speakers.

Most decent speakers though are in that 88/89 db sensitivity range.

 

[gnorthern]

The db scale is log. So your receiver would have to produce 10 times the power to get the same loudness with the 88 db sensitivity speakers as the 90 db sensitivity speakers.

Most decent speakers though are in that 88/89 db sensitivity range.

First, double checking, did you mean 98 db speakers, not 90?

Does anything bad happen if I am pumping 10 times more power through receiver? I ran two power lines to my entertainment center, the first for the TV, Roku, blue ray, ethernet switch, and receiver, and the second separate one for a subwoofer (which after 9 years I got a subwoofer that needs its own circuit). I am not overloading the circuit.

I'm looking at the math. Several websites say doubling the distance drops decibels by 6. So 1 watt will produce 79 db where I sit. 10 watts 89 db, 100 watts 99db. So if I listening to a movie at 80 db, and jet flies over and it jumps up to 100 watts per channel. Is that bad?

 

[TLS Guy]

First, double checking, did you mean 98 db speakers, not 90?

Does anything bad happen if I am pumping 10 times more power through receiver? I ran two power lines to my entertainment center, the first for the TV, Roku, blue ray, ethernet switch, and receiver, and the second separate one for a subwoofer (which after 9 years I got a subwoofer that needs its own circuit). I am not overloading the circuit.

I'm looking at the math. Several websites say doubling the distance drops decibels by 6. So 1 watt will produce 79 db where I sit. 10 watts 89 db, 100 watts 99db. So if I listening to a movie at 80 db, and jet flies over and it jumps up to 100 watts per channel. Is that bad?

Unfortunately it is not that simple, as speakers are not resistive loads, but inductive loads. So the impedance curve of the speakers comes very much into play. You seldom have any idea what the true load actually is, unless a manufacturer quotes a minimal impedance or a third party reviewer has published the impedance curve and phase angles. A low impedance and a highly negative phase angle in the power band is a real amp and receiver killer if the volume is pushed. It is current that kills output devices, and that is hard to discern unless you have the equipment to make the measurements, like I have.

However, the general rule that high volumes kill applies. But even better keep and eye on how hot the receiver is getting. It is the heating effect of the current through the output devices that is the killer. If it is getting hot turn it down. An infrared laser temperature gun is a good investment. There are lots of these on the market, Home Depot and your local hardware store will have lots. An absolute maximum temperature of 89F (29C) is a good rule and cooler is better and try and keep it at 80 F or below if you can. Physics is even further against us on this as the heating goes up by the increase of the square of the current. It is not linear.

 

[TLS Guy]

First, double checking, did you mean 98 db speakers, not 90?

Does anything bad happen if I am pumping 10 times more power through receiver? I ran two power lines to my entertainment center, the first for the TV, Roku, blue ray, ethernet switch, and receiver, and the second separate one for a subwoofer (which after 9 years I got a subwoofer that needs its own circuit). I am not overloading the circuit.

I'm looking at the math. Several websites say doubling the distance drops decibels by 6. So 1 watt will produce 79 db where I sit. 10 watts 89 db, 100 watts 99db. So if I listening to a movie at 80 db, and jet flies over and it jumps up to 100 watts per channel. Is that bad?

It should be 98 db. I made a typo.

 

[ski2xblack]

What specific speakers did you previously have that claimed 98db sensitivity?

Not many brands boast such numbers, and the one brand that most commonly does, Klipsch, grossly exaggerates their sensitivity specs. They also have a tendency to inflate impedence ratings, suggesting an easier load than they really are.

So your concerns re powering your new, lower sensitivity speakers may be unfounded. Without knowing the specific models involved and their measured specs, it's all conjecture.

 

[gnorthern]

What specific speakers did you previously have that claimed 98db sensitivity?

Not many brands boast such numbers, and the one brand that most commonly does, Klipsch, grossly exaggerates their sensitivity specs. They also have a tendency to inflate impedence ratings, suggesting an easier load than they really are.

So your concerns re powering your new, lower sensitivity speakers may be unfounded. Without knowing the specific models involved and their measured specs, it's all conjecture.

I have Klipsch RF82 II. Yes I am using Klipsch's ratings.

I am paranoid since I did have a Denon Receiver, I forget the model but about $1500 or about the same as my current one, fail. I suspect I had less efficient speakers since they were acoustic suspension speakers, though I am not sure since it had a built-in powered subwoofer. I almost never drove it loud and it still produced a lot of heat. It was repaired under warranty. I don't think the 2" of clearance specified by Denon was enough, so I drilled a 5" hole above it and put an exhaust fan directly on top of it, and it never failed again. I just wanted a 9.2 receiver instead of 5.2 for our new house.

 

[TLS Guy]

I have Klipsch RF82 II. Yes I am using Klipsch's ratings.

I am paranoid since I did have a Denon Receiver, I forget the model but about $1500 or about the same as my current one, fail. I suspect I had less efficient speakers since they were acoustic suspension speakers, though I am not sure since it had a built-in powered subwoofer. I almost never drove it loud and it still produced a lot of heat. It was repaired under warranty. I don't think the 2" of clearance specified by Denon was enough, so I drilled a 5" hole above it and put an exhaust fan directly on top of it, and it never failed again. I just wanted a 9.2 receiver instead of 5.2 for our new house.

What is more relevant is the speakers you are contemplating to purchase.

Your speakers are pretty raucous beasts, so an upgrade would make a lot of sense, if it truly would be an upgrade. Klipsch sets the bar pretty low, especially during the period your speakers were produced.

 

[gnorthern]

Unfortunately it is not that simple, as speakers are not resistive loads, but inductive loads. So the impedance curve of the speakers comes very much into play. You seldom have any idea what the true load actually is, unless a manufacturer quotes a minimal impedance or a third party reviewer has published the impedance curve and phase angles. A low impedance and a highly negative phase angle in the power band is a real amp and receiver killer if the volume is pushed. It is current that kills output devices, and that is hard to discern unless you have the equipment to make the measurements, like I have.

However, the general rule that high volumes kill applies. But even better keep and eye on how hot the receiver is getting. It is the heating effect of the current through the output devices that is the killer. If it is getting hot turn it down. An infrared laser temperature gun is a good investment. There are lots of these on the market, Home Depot and your local hardware store will have lots. An absolute maximum temperature of 89F (29C) is a good rule and cooler is better and try and keep it at 80 F or below if you can. Physics is even further against us on this as the heating goes up by the increase of the square of the current. It is not linear.

Where do you measure temperature? If on top and the middle, my receiver is almost always above 89 degrees.

I am trying to understand what a negative phase is and will ask you when it is "highly" after I understand it.

 

[gnorthern]

What is more relevant is the speakers you are contemplating to purchase.

Your speakers are pretty raucous beasts, so an upgrade would make a lot of sense, if it truly would be an upgrade. Klipsch sets the bar pretty low, especially during the period your speakers were produced.

It is down to a Bowers & Wilkins 704 S3 and a Paradigm Premier 800f. I found a person with the BWs in storage and wants to get rid of them for the same price as the 800Fs. If the BWs won't destroy my receiver often running at 70 db and an occasional movie at 80 db, that is my choice. That is what I am trying to figure out.

 

[Antares]

Where do you measure temperature? If on top and the middle, my receiver is almost always above 89 degrees.

I am trying to understand what a negative phase is and will ask you when it is "highly" after I understand it.

I think what @TLS Guy means by negative phase is when the impedance load of a speaker to a receiver starts reaching 0 ohm (effectively frying the receiver), though most receivers will enter protection mode before that occurs.

 

[gnorthern]

I think what @TLS Guy means by negative phase is when the impedance load of a speaker to a receiver starts reaching 0 ohm (effectively frying the receiver), though most receivers will enter protection mode before that occurs.

SO basically, it's the steepness of the impedance curve as it approaches 0 and which one drops lower. I'm going to check.

 

[Antares]

And the end of the day what's important is that they sound good.

 

[ski2xblack]

Maybe others google-fu is better than mine, but I couldn't find any third party tests of the rf 82 II. Dollars to donuts, they're probably realistically 91-92 db/w, so only 3-4 db more sensitive than your new speakers. It's wise to keep an eye on the heat, as you're doing. Your AVR is probably ok with the added ventilation.

Worst case, you have a large room, like it loud, or both. If that's the case, external amps might be advisable, but only if there is a demonstrable need.

Regarding the phase angles, they can compound the load, effectively lowering the impedance. Speakers with low impedance and severe negative phase angles at the same frequencies will demand more current and thus generate more heat that your amp has to dissipate. Unsure if your new speakers are problematic, load wise. What are they? [I see they are B&W 704 S3...couldn't find an impedance/phase plot on those specifically, but B&W have a history of models with more challenging loads.]

 

[gnorthern]

Maybe others google-fu is better than mine, but I couldn't find any third party tests of the rf 82 II. Dollars to donuts, they're probably realistically 91-92 db/w, so only 3-4 db more sensitive than your new speakers. It's wise to keep an eye on the heat, as you're doing. Your AVR is probably ok with the added ventilation.

Worst case, you have a large room, like it loud, or both. If that's the case, external amps might be advisable, but only if there is a demonstrable need.

Regarding the phase angles, they can compound the load, effectively lowering the impedance. Speakers with low impedance and severe negative phase angles at the same frequencies will demand more current and thus generate more heat that your amp has to dissipate. Unsure if your new speakers are problematic, load wise. What are they?

I found somebody with Bower and Wilkins 704 s3 sitting in storage. The first price they threw out was almost half off.

 

[TLS Guy]

It is down to a Bowers & Wilkins 704 S3 and a Paradigm Premier 800f. I found a person with the BWs in storage and wants to get rid of them for the same price as the 800Fs. If the BWs won't destroy my receiver often running at 70 db and an occasional movie at 80 db, that is my choice. That is what I am trying to figure out.

Generally B & W speakers are not a good match for receivers. They tend to have impedance dips and adverse phase angles. I can not find an impedance curve or phase angles for those speakers.

The impedance curve is how the impedance of a speaker varies with frequency, the phase angles are show the variation of the phase angle between current and voltage.
In a resistor the current and voltage follow strict ohm's law, and the phase angle is zero. Speakers are inductive loads, so current and voltage are not in the same phase and this phase variation varies with frequency. When there is a high negative phase angle then the output transistors have to provide a high current, for what is known as the apparent power. This power is given back later in the cycle, but the power has to be provided transiently and amps tend not to like it.

Here are the impedance curve and phase angles of a B & W 802 D speaker.

The solid line is the impedance curve and the dotted line the phase angles plotted against frequency.

You can see that the impedance drops to around 3.6 ohms around 80 Hz, well in the power band and also at 700 Hz. Now the phase angle is about -60 degrees when the impedance is around 4 ohms. This is the type of situation that is an amp stress.

Here is the impedance curve of my 3 way speakers in our family room.

The red line is the phase angles with frequency and the blue the impedance curve. Those are essentially 6 ohm speakers. I designed these speakers and impedance compensated the crossover circuit. The only significantly negative phase angle is when the impedance is very high, as it is right over one of the tuning peaks.

So those speakers is an easy drive for an amplifier, whereas the B & W is a torture test.

So, I have to caution you about matching B & W speakers with receivers, as they are prone to be receiver busters.

I know this is complicated, but understanding all this helps keep you out of trouble.

 

[ryanosaur]

B&W 600 and 700 series speakers are a joke. Don’t do it.