Sensitivity Question

**BleedingStar** · **02-06-08, 06:08 PM**

Though I've been an audioholic for years, there are many little things I've never really looked into very deep. Therefore I just want to make sure I am understanding this concept.

My old pair of speakers was was rated at 93 db / 1w / 1m. My new pair of speakers are rated at at 84 db / 1w / 1m. Therefore to get the same volume out of this pair I will need to crank up the adjustment on them 9 db?

After tweaking with the speakers for some time now, I had basically discovered that turning it up 9 db did actually give the sound volume that I am used to... but until I really sat and thought why I didn't realize this simple explanation.

And reading in to it even deeper that means I am actually having to send them 8 times the wattage that I had to give my old ones? (Double wattage for every 3 db- 2x2x2)

Also, on my receiver: when I turn the volume up 3 db notches, am I actually sending twice the wattage out to my speakers? I am sure it is a bit more complicated than that in actuality, but is that the jist of it? And if so, does that mean on my 100 watt per channel rated amp, at -30 db I am giving the speakers like basically no wattage? That one kinda throws me off?

**Dionyz** · **02-07-08, 09:08 AM**

Sensitivity calculation is really straight forward. See the following table

dB Watt/ch
84 1
87 2
90 4
93 8
96 16
99 32
102 64
105 128
108 256
111 512
114 1,024
117 2,048
120 4,096
123 8,192
126 16,384

What you have been suspecting and what the above table confirms, is that you created a problem for yourself in selecting such low efficiency speakers.
You really need an external amplifier to drive these speakers and a massive one at that, especially if you also use these in a home theater.

THX reference level is 105 dB, which requires 128 watt/ch amp to reach.
Your receiver just cant get there.
Further, dynamic peak content in films and certain music require another 20 to 30 dB.
Thus for 125 dB peak to be reproduced without amplifier clipping, your speakers would require about 16,000 watt/ch.

Obviously you have a problem.
First of all I do not know of any consumer amps delivering this type of power.
And second, even if there was one, at that power level it would melt your speakers.

I feel sorry for you and others that insist on making the mistake of buying these low sensitivity speakers.

If anyone want true music and theater reproduction, they really need to focus on speakers with high sensitivity.

Your old speakers with 93 dB/watt would be the lowest efficiency speakers I would even consider.

I have Klipsch RF-83 with 100 sensitivity which I am driving with a Onkyo 905, which is 140 watts/channel. Even with this high sensitivity, I will be upgrading to an external amp with 500 watts/ch to get the most realistic home theater reproduction (with no clipping). The Onkyo can get the RF-83s to reasonable loudness. However, these spekers love power. The more you give them, the better they sound - not just louder, but bass and percussion gets tighter and more controlled.

**jackfish** · **02-07-08, 09:48 AM**

First, BleedingStar only selected these speakers because he got a deal he could not pass up. Second, if I were to listen to music or movies in my space at 105 dB with peaks of 125 dB I would likely go deaf, my wife would leave me, and the cops would be knocking at the door. I don't know how large his listening area is, but I doubt it is large enough to require 16,000 watts for satisfying audio levels. I typically listen to music at 85 dB (perhaps rare 105 dB peaks) and it is plenty loud as two people next to each other would have to raise their voices significantly to have a conversation. And remember there are two speakers not one. Then there is room gain. Finally, I think BleedingStar will find satisfaction with his new electrostats when paired with a power amplifier such as the Tapco Juice J-2500 for $400. I agree it is unfortunate he has such inefficient loudspeakers but it is not the end of the world.

With two speakers and room gain it is going to look more like:
dB Watt/ch
91 1
94 2
97 4
100 8
103 16
106 32
109 64
112 128
115 256
118 512
121 1,024

Of course no one would be sitting one meter from the speakers either.

So, 32 watts/channel for THX standard (who actually listens at this level) and 1,024 watts/channel for peaks of 15 dB. Even if there is brief clipping at these peaks I contend few people listen at home to THX reference levels.

Brian Florian says, "Simply stated, Reference Level is a standard, known, predictable and reproducible playback volume level. When movie sound tracks are crafted, they are done so on systems which are locked at this level. The sound artist does not play around with a big volume knob when doing his/her work. If the sound artist wants something to be loud, they make that sound loud within the sound track. When they want something to be soft, they make that element soft within the sound track. Movie theaters set their playback level by the exact same rules, so when the movie is shown, you hear EXACTLY what the sound artist heard when they were making the piece. Loud, soft, in-between, it's all there, and no one touches the master volume knob over the course of a two-hour movie.

To achieve THX certification, components must play at this reference level without breaking, distorting, buzzing, rattling or any other distracting effects.

Reference level is by any definition, objective or subjective, quite loud. It basically mirrors the dynamic range of the studio system, which in the case of all movie sound tracks, is 105 dB. Any single channel of the system is calibrated to play 0 dB FSD (the loudest sound the sound track can contain) at 105 dB (115 dB for the LFE channel). While that is really, REALLY loud, its important to remember that there is 105 dB of dynamic range and the artist can put a sound at any level they want. So while a system's volume may be set to reference level, dialogue within the sound track can, and most often is, at a normal, natural level. Reference level, with the dynamic range available, permits a movie to have that normal, natural dialogue, and then suddenly a spectacular, loud car chase without anyone touching the volume control. Every element in the sound track comes out as it should."

So, my current understanding of the THX reference is that the peaks are likely to be 105 dB, not 125 or 135 dB.

So, at BleedingStar's hypothetical listening position 12 feet from the loudspeakers here is how it might look:
dB Watt/ch
79 1
82 2
85 4
88 8
91 16
94 32
97 64
100 128
103 256
106 512

So, with a 500+ wpc power amp it is likely that THX reference levels indeed can be approximated.

Sorry for all the edits, stream of polemics I guess.

**Bob_99** · **02-07-08, 09:50 AM**

I believe it is common for most speakers to have an efficiency in the high 80s or low 90s. While the Kipsch may have a very high sensitivity, I believe that they are uncommonly high and far from the norm.

Correct me if I'm wrong.

Bob

I would also second Jay's comments.

**avaserfi** · **02-07-08, 10:23 AM**

Quote:

Dionyz wrote:

THX reference level is 105 dB, which requires 128 watt/ch amp to reach.
Your receiver just cant get there.
Further, dynamic peak content in films and certain music require another 20 to 30 dB.
Thus for 125 dB peak to be reproduced without amplifier clipping, your speakers would require about 16,000 watt/ch.

THX reference level is 75dB in home 85dB in theaters with the 20-30dB peaks. I am not sure where you got 105dB reference levels, but SPLs of those amount in midrange and treble frequencies would cause hearing damage from extended use.

Quote:

Dionyz wrote:

If anyone want true music and theater reproduction, they really need to focus on speakers with high sensitivity.

Your old speakers with 93 dB/watt would be the lowest efficiency speakers I would even consider.

While sensitivity is important 93dB/W/M is over doing it. Generally shooting for a sensitivity of 89dB/W/M is more than sufficient, but with a properly designed driver lower sensitivities are okay if coupled with proper amplification.

As far as realistic production goes there are far more important things than sensitivity such as on/off-axis response, cabinet resonance, etc...This is of course assuming sound reproduction without any degradation at all and maximum pleasure as shown by perceptual research - something few to no commercial speakers are capable of.

Quote:

Dionyz wrote:

I have Klipsch RF-83 with 100 sensitivity which I am driving with a Onkyo 905, which is 140 watts/channel. Even with this high sensitivity, I will be upgrading to an external amp with 500 watts/ch to get the most realistic home theater reproduction (with no clipping). The Onkyo can get the RF-83s to reasonable loudness. However, these spekers love power. The more you give them, the better they sound - not just louder, but bass and percussion gets tighter and more controlled.

Yes, louder is generally perceived as better, but the Onkyo 905 can easily power those Klipsch speakers to deafening levels. That 500W amp is simply overkill with those speakers 50W is more then enough for typical usage within THX reference levels.

**WmAx** · **02-07-08, 10:47 AM**

Quote:

BleedingStar wrote:

My old pair of speakers was was rated at 93 db / 1w / 1m. My new pair of speakers are rated at at 84 db / 1w / 1m. Therefore to get the same volume out of this pair I will need to crank up the adjustment on them 9 db?

Yes.

Quote:

And reading in to it even deeper that means I am actually having to send them 8 times the wattage that I had to give my old ones? (Double wattage for every 3 db- 2x2x2)

Yes.

Quote:

Also, on my receiver: when I turn the volume up 3 db notches, am I actually sending twice the wattage out to my speakers?

Yes.

Quote:

I am sure it is a bit more complicated than that in actuality, but is that the jist of it?

Actually, it is as simple as that.

Quote:

And if so, does that mean on my 100 watt per channel rated amp, at -30 db I am giving the speakers like basically no wattage? That one kinda throws me off?

The 'dB' increments on amp volume controls are relative - don't read much into that.

Since I doubt you have the hardware to analyze your amplifier wave forms under the conditions you play music; I recommend that you play some music that you find important to play at 'louder' volumes when you do listen to it.Now, play it at low volume, then turn it up to your 'reference' level.

Do you hear any changes that could be defined as 'brittle/harsh/squashed' sound when you go from soft to loud volume? ([i]Do not count simple treble/bass tonal difference; the human hearing system is more sensitive to high and low frequencies as the SPLs increase, as a natural function of how our brains are wired.)

If you do hear a difference fitting that rough description, it is likely you are clipping the amplifier output, as that is the typical sound signature that starts to occur when running a common solid state amplifier just over the edge of clipping. The solution would be to add on a high power amplifier; a pro sound amp would be the most cost effective solution if this is needed.

-Chris

**Dionyz** · **02-07-08, 01:32 PM**

To a certain degree you are all correct.

A lot will come down to the normal listening level in the home and the degree of clipping (inaccurate reproduction) you are willing to accept.

1 - I would be extremely unsatisfied with 84 sensitivity speaker output in my home theater. These just have no way of performing satisfactorily in my home theater, especially with a 100 w/ch receiver.

2 - The Klipsch RF-83s, despite their very high sensitivity, have impedance dips to around 3 ohms in certain frequencies. As I said these speakers love power. When watching movies with the Onkyo 905, I have the volume at around -3 to 0 dB. I do not turn it up more as I do not want any clipping during the peaks. And this is in a temporary location with no sound treatment. When I move my system into my HT with sound treatment, when it is finished, the Onkyo will not have sufficient power.

3 - Dynamic peaks are what drive the need for power, not average loudness. The 20 dB dynamic peak is an average. Certain sounds require well above this level, pushing 40 and up to 60 dB. If you don't care about clipping and the associated distortion and missing reproduction, then you may well be satisfied with low efficiency speakers with an average receiver.
However, if you care about faithful, undistorted sound reproduction - if you know what it sounds like with high quality and efficient speakers, then you want the most power you can afford. That is why even the RF-83 speakers NEED more than 140 watts/channel for pure and unclipped dynamic peak reproduction.

Bottom line is that it all depends on what your listening habits are, combined with your expectations.

YOU, not I, or anyone else should be the judge.
I only offer my OPINION and attempting to raise awareness.
I am definitely not telling what others should do.

**tonyvdb** · **02-07-08, 04:47 PM**

I agree with Andrew, Just an added point:
You have to remember that actual db readings will vary from space to space. In a dead room with lots of absorbing surfaces a speaker will need to output higher levels to "fill" the space with a certain db level where as a bright room with bare walls will require less. If you place your speakers in a large living room they simply wont get the db out of them to fill the space compared to a small room.
Also with the new digital surround systems you have all 7 channels outputting volume levels that will add to the db levels in the space meaning that your main speakers don't work as hard.
If I was to run my system at a constant 105db (and it would have no problem doing so) my whole family would leave as thats way louder than any movie theater runs at.

**BleedingStar** · **02-07-08, 04:51 PM**

Yeah, I don't think i've ever watched a movie at 105 db, that sounds like a little much to me. I don't have the proper tools to measure what I actually do listen to it at, but its nothing extreme. Considering I live in a apt complex, I would most definitely be kicked out if i listened out 105 db, not to mention probably be deaf within 5 years since i watch movies every night. I've never watched a THX certified Dolby Digital movie with volume on my receiver higher than -20 db. So i'm not too concerned about any clipping effects just at this point.

Thank you a ton for all the answers, great things to know.

**tonyvdb** · **02-07-08, 05:00 PM**

My curent main speakers have similar ratings as your old ones did:
2 way reflex
38-20,000hz
4ohm
sensitivity 93db
Max SPL 113db
continuous 200watts
crossover 2.3khz
Efective volume 57 litres

But in my room they really need to work when in two channel Pure mode as the room is fairly dead so I know where your coming from.

**WmAx** · **02-07-08, 07:30 PM**

Quote:

Dionyz wrote:

3 - Dynamic peaks are what drive the need for power, not average loudness. The 20 dB dynamic peak is an average. Certain sounds require well above this level, pushing 40 and up to 60 dB.

Please provide reference to 40 and 60 dB peak material. The most dynamic music, which is extremely dynamic, is in the range of just over 30dB over average RMS levels. This is very rare. Typical modern music has about 10-13 dB peak values compared to the average RMS levels. THX certified movie standards require a peak 105 dB SPL on the main channels, and 115dB SPL on the LFE. 85dB is the reference value use for calibration, though actual movies may average 10dB lower in actual playback.

Quote:

That is why even the RF-83 speakers NEED more than 140 watts/channel for pure and unclipped dynamic peak reproduction.

If it's really 140 watts, and able to handle the current increase required by the impedance dips of the speaker, then the amplifier will do fine with that speaker system in any circumstance, assuming it's sensitivity is rated accurately. I have not seen credible 3rd party testing of the amplifier/receiver that you mention(Onkyo 905) under the appropriate test conditions, so I don't know if it can really deliver it's rated power to that particular speaker system.

-Chris

**Dionyz** · **02-08-08, 09:29 AM**

[quote=WmAx;79651]

Quote:

1) You are correct in relation to dynamic peaks for musical material. There is no musical material with 40 to 60 db dynamic peaks. These exist in home theater applications. I have seen references that gun shots and explosions are in this range (I can't find the reference at the moment). However, when you are watching a movie and the gun shut or explosion just does not sound, with the impact you expect, you can be certain that the receive/amp is clipping.

I don't doubt there are 60 db peaks, but not relative to the average dB level. A scene can reduce to quiet levels (-20 below average, for example) for a short time period, and the dynamic can rise from this point.

Quote:

In term of loudness, I know of no movie theater that has playback at 85 dB that you imply (other than quiet passages). I have not been to movies with a sPL meter, but I would guess, they are about 95 dB. When watching films at home, I try to replicate movie theater levels.

THX certified cinemas all must conform to this reference level of 85dB. Non-certified cinemas can use whatever level they see fit to use, that is, they have no standard.

-Chris

**WmAx** · **02-08-08, 10:13 AM**

I am sorry Dionyz, I think I must have used an incorrect button intended for moderation( I suspect I accidentally clicked 'EDIT' instead of 'QUOTE' since they are side by side.).

Please edit your post to restore the original (as close as you remember) statements. I don't know how to restore it, as I did not quote all of your text - so only part is left. I was just made a moderator, so I'm afraid I am not yet familiar with all of the functions.

-Chris

**hyghwayman** · **02-13-08, 08:41 AM**

Quote:

WmAx wrote:

I am sorry Dionyz, I think I must have used an incorrect button intended for moderation( I suspect I accidentally clicked 'EDIT' instead of 'QUOTE' since they are side by side.).

Please edit your post to restore the original (as close as you remember) statements. I don't know how to restore it, as I did not quote all of your text - so only part is left. I was just made a moderator, so I'm afraid I am not yet familiar with all of the functions.

-Chris

, things happen!

hyghwayman - Thanks for the edit

**hyghwayman** · **02-13-08, 09:24 AM**

I am getting ready to buy the SBS-01 5.1 speaker system from SVSound.com which have these specs..

Specifications

Model NameSBS-01SCS-01
Frequency Response (Anechoic)68Hz - 20kHz ± 3dB - mains, rears and center
Nominal Impedance - 8 ohms
Sensitivity - 85dB fronts and rears, 87dB center
Power Handling - 20w to 120w
Sub - +/- 3dB from 20-100 Hz

I will be using my Pioneer VSX-816 to push these speakers, which is rated @
110w (20 to 20k Hz, THD 0.7%, 8ohms) stereo
Will my receiver work ok with the SVS speaker

?
Also should I worry about the sensitivity of these speaker?

Thanks,
hyghwayman

**jackfish** · **02-13-08, 09:32 AM**

Quote:

Will my receiver work ok with the SVS speaker

?

Yes.

**MatrixDweller** · **02-14-08, 08:55 AM**

It was my understanding that the THX certified peak level is 105dB. That would be the loudest anything will go in a THX certified theater. Maybe dialog and normal volume scenes might be at 85dB as people have stated.

Also most good amplifiers (including integrated A/V receivers) have some dynamic headroom. The watt rating given is usually for 2 channel continuous at a given distortion level. Most reputable manufacturers rate their amps at a non-clipped distortion level and the better ones try to rate the lowest THDs. A cheap HTIB however (like many Sony's) may rate their watts at super high or peak levels with high THDs of 10%. 140W/channel at 10% THD would probably be more like 15W/channel at 1% THD. Likewise a receiver rated at 120W/channel at .05% THD may have a dynamic output of over 380W at 1% THD. Good receivers may even alter a clipped output to protect your speakers during periods of high dynamic output (soft clipping).

Highwayman your Pioneer rated at 110W @ .7% THD would probably start clipping at higher volumes. It probably won't sound great much past -40dB on it's volume scale.

Q: Have you gone deaf yet Dionyz? I think your assumption of 105dB +20-30dB headroom is a little high. 130dB will cause your ears to hurt (damage), 135dB will make you go deaf in no time flat even if just in short peaks.

**justin.kerr** · **02-14-08, 07:16 PM**

Quote:

MatrixDweller wrote:

130dB will cause your ears to hurt (damage), 135dB will make you go deaf in no time flat even if just in short peaks.

135 will not cause hearing loss, in low frequencies. In fact very low frequencies are just starting to be heard/felt at 110db.

I hit peaks of around 130db in most movies, with the average/delta db of 85db, A-weighted, with A-weighted peaks around the 105-115db, at listening position.

**MatrixDweller** · **02-14-08, 09:55 PM**

True ultra low frequencies below 30Hz take a lot more sound pressure to be heard and to damage your ears but the sub and speakers are going to produce a lot of low-mid and mid bass also.

The hair cells in your ear do not have the capacity to heal themselves. 80dB or higher over prolonged periods will cause hearing damage. So even though each time you watch a movie you only loose 1/10,000 of your hearing capacity, do it enough times over your life span you'll be hard of hearing.

http://www.nidcd.nih.gov/health/hearing/noise.asp

Who knows though with medical technology they might be able to grow you a new ear or use nanotechnology to repair it in the future.

**justin.kerr** · **02-14-08, 10:20 PM**

A-weighted spl, not C-weighted though? correct? because 130db of 5hz signal A-weighted would be pretty hard to accomplish.

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