85 db sensitive speakers for HT - questions and discussion

85db is reference level,with 20db dynamic headroom from each channel.

The LFE channel is 10db louder, so reference is 95db with 20dB headroom.

So basically, you need the capability for 105dB from speakers and 115dB from a subwoofer.

to hit 105dB with 85 dB sensitive speakers, you only need about 128 watts per channel, if you are sitting 3 feet away. Double distance, subtract 6 dB. So 128 watts can do 99 dB at 6 feet, 93 dB at 12 feet. etc.

So basically you can't hit reference level with 85dB speakers unless you have speakers with high power handling, and high powered amplifiers (like 500 watts/ speaker), which most people don't have. And you definitely can't hit reference level off an AVR in any room with <90 dB speakers, which is why people say don't go below 90 dB.

http://www.thx.com/consumer/thx-technology/thx-reference-level/
Edited by WagBoss - 8/20/12 at 11:28am

Any generalization will be wrong.

Here are a bunch of semi-random thoughts.

When I got back into this game a few years ago I looked up "reference" since everybody was using the term. IIRC, the THX site said "reference" was 105 dB/speaker at the LP, and the 75 dB everybody uses is actually a -30 dBr calibration level (not actually the "reference"). I believe the "pro" level is 85 dB (20 dB below reference). Hopefully somebody will correct me if I got that wrong.

75 (or 80) dB is pretty loud to me.

Verbiage aside, there are so many factors at play that there is no hard answer. Plenty of us have low-efficiency speakers in our HT systems and have no issues (I fall into that category). The problem arises when they also have limited output/power handling, which does apply to a lot of planar speakers like Magnepans and electrostats. They may distort and clip before you can reach 100+ dB peaks. My system using Magnepans hits 105 dB with a pair of speakers (not including the center, surrounds, and rears) and that is good enough for me.

Another drawback is that your AVR might not have enough power to drive them to clipping, so then you need external amps.

By the way, some small speakers are also inefficient; efficiency is traded for FR in the design, primarily to extend the 3 dB point for the bass a little lower.

Peaks are tricky: some are pretty broadband, but others are mostly just LF. The largest amount of power is generally in the LF where your sub takes over.

In a room, each additional pair of speakers adds 3 dB if they are well away from walls, then add another 3 dB if beside a wall, and _another_ 3 dB if in a corner. So, you get 6 dB increase by moving a speaker from out in the room into a corner. Of course now you have other FR issues to deal with...

Here is a pretty nice online SPL calculator you ca nplay with: http://myhometheater.homestead.com/splcalculator.html

The counter arguments most often seem to revolve around the power required and ability of inefficient speakers to handle the power (linear headroom).

HTH - Don

Any way you look at it, going from a speaker with 91 db/watt sensitivity to a speaker with 85 db/watt sensitivity is equivalent to reducing your amplifier power by a factor of 4.

to get the same performance as 91 db/watt speakers with an 80 watt amplifier, 85 db/watt speakers will need 320 watt amplifiers.

It is a lot cheaper to select some more efficient speakers than spend a fortune buying some very high-powered amplifiers.

85 dB is not reference. 85 dB is simply the measured target volume of a standardized -20 dB pink noise signal measured at the listening position using an SPL meter set to C-weighting slow . A "0" dB signal(not the "0" on your volume knob!) represents the absolute end of the dynamic range of the digital media, above which the signal will be truncated, or clipped. Each speaker is calibrated individually. This assures the amplifier gain, and hence volume, matches the volume the mixer used to mix the soundtrack. Then, when you set your master volume control to "0", you hear the soundtrack at the volume the engineer intended.

Consumer equipment is typically measured with a -30 dB pink noise to not upset our delicate ears . The resulting calibration is the same.

So reference in a calibrated system is whatever volume the mixer wants you to hear from 0 dB to 105 dB measured using C-weighting slow.


Often, at reference, normal movie dialogue is between 75-80 dB and I don't personally find that loud.

Each speaker is individually calibrated to the reference standard.


It is at one speaker.

Speaker sensitivity is typically measured with 1 watt of power at 3 ft. distance. Every doubling of distance causes a 6 dB reduction in volume. So at 18 ft. your 85 dB speaker would have an effective efficiency of 70 dB. Each 3dB increase in volume uses a doubling of power, so to go from 70 dB to a 105 dB peak you would need approximately 3000 watts.

See the problem with low sensitivity?

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I know this discussion is focused on home theater, but i'd like to add some input.

For strictly HT, I agree that it would be most effective to opt for higher sensitivity speakers first and foremost.

For music, there are a number of speakers that are tremendous performers, the only downfall being that their sensitivity is in the middle 80s.

For me, my intention was to strike a good balance for both HT and music. I ended up with 87.5dB speakers and a multi-channel amp that does 600wpc into 4 ohms. The amp, which is an Emotiva XPR-5, is a relatively inexpensive way to provide gobs of power to drive my speakers, probably much more than I need. I can tell you that my HT setup can get ear-shatteringly loud while still being extremely clear and maintaining it's poise. Crossed to 2 subs, it beats the hell out of any movie theater that i've been to. And for music, I can say that it easily bests many high-end, multi-thousand $ boutique set-ups i've heard.

What i'm trying to say is that you can definitely make lower sensitivity speakers work in an HT (provided that they can handle the power) and you don't have to necessarily spend a fortune doing so. It really depends on what your priorities are.

74dB SPL dialog is reference level. 85db is a test tone at -20dBFS.

I'm fine with the dialog at 75dB, but when the music and fx hit, it's ~100dB and that is loud for me. Sometimes I wonder, is this the way the movie is mixed? normal dialog volume but very loud music, and EXTREMELY LOUD effects?

Make no mistake, reference can be loud. But listening to a quality reference mix with a system that has low distortion and little to no compression of dynamic peaks does not sound uncomfortably loud. There are exceptions of course and some mixes are made to be loud on any system. However, listening to reference with a system that does not have these qualities is nearly always uncomfortable regardless of mix due to distortion and compression of dynamic peaks.

Very few systems have these attributes and therefore most make reference intolerable IME.

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