Speaker damage from running

I wrote

>it takes a program material level of 111dB to bottom it which isn't a problem, 105dB @ 10Hz which is getting more likely to be an issue, and 93dB @ 5 Hz which will cause problems on some sound tracks. With a full 6dB of baffle step compensation the numbers would be 105dB, 99dB, and 87dB

and the astute reader will note that 0.5-10 Watts can be enough to be a problem.

Markhyams writes:
>Will running the main L/R speakers in "full-range" and no .1 LFE channel damage the speakers?

With sealed speakers you should be fine (SPL drops 12dB/octave and excursion remains constant with decreasing frequency after dropping below their lowest high-pass pole). With ported and open baffle speakers you may be saved by receivers/processor makers heeding the Dolby recommendation to discard the LFE channel when down-mixing for setups not including a sub-woofer. If you actually mix LFE into some such drivers you can cause mechanical damage on some sound tracks.

There are several things working against you:

1. The LFE channel is decoded 10dB hotter allowing for 111-115dB SPL peaks at Dolby reference level where you have dialog at 74dB SPL.

2. Many engineers include very low frequencies (< 10Hz).

3. Speaker excursion quadruples for a given SPL for each octave you drop. When you put a driver in a sealed box the stiff air spring keeps SPL from rising so SPL drops 12dB/octave below the lowest high-pass pole and excursion remains constant so you'll be fine if you don't have the power to exceed the speaker's mechanical limits. A ported box does even better in its pass-band because the system gets stiffer approaching the port resonance so driver excursion drops with most of the output coming from the port but below that the system unloads and the driver does whatever it would without a box.

The Seas W22EX001 8" mid-bass reaches its mechanical limits at 101dB (in half space as when floor mounted) at 20Hz, 89dB @ 10Hz, and 77dB @ 5Hz. With resonance at 25 Hz and Q about .35 there are real poles around 10 Hz and 60 Hz once it's not controlled by a port so output is 9.5dB down at 20Hz and it takes a program material level of 111dB to bottom it which isn't a problem, 105dB @ 10Hz which is getting more likely to be an issue, and 93dB @ 5 Hz which will cause problems on some sound tracks. With a full 6dB of baffle step compensation the numbers would be 105dB, 99dB, and 87dB.

Some drivers reach their mechanical limits with the voice coils running into their motor back plate and eventually breaking.

Commercial active sub-woofers do OK because they include subsonic high-pass filters to avoid issues.

>That is, will routing the .1 LFE channel to the main L/R speakers cause damage?

Unacceptable distortion may be more likely although you really need to figure out what your receiver/processor does using a test disk with LFE signals. With no main speaker output when the sub-woofer is disabled you'll be fine in more (but not all cases - some idiots also mix single digit frequencies into the screen channel outputs. four 10" woofers bottoming in unison make a very loud cracking noise that sounds expensive when the $800 driver cost is considered).

A big part of the answer to this would be, what the listener does with the volume. A lot of us get by doing this all the time. With movies, it's riskier. In my one system for TV, if I switch my sub on, I hear a lot of deep bass that's there (some movies) that my speakers won't reproduce. There may be deep bass moving your woofers a lot, eating a ton of power that you may not realize, since they won't reproduce the sound (although the woofers are moving), and you can't hear it.

It's important to have plenty of power, and important to recognize when something no matter how small, doesn't sound right. You need to lower the volume quickly, and keep it low enough to make sure that distortion never appears again. If you have a good ear, and are careful, you should be OK. Running an underpowered amp out of power can cause damage quickly.

I use 2 channel for my video system and the main speakers always see full range signals. Currently using B&W 805s; have used Spendor SP-2s and the smallest Epos [12?] Driving them with Meridian 605 power amps [150 watts per channel]. Never had any problem. I use subs but in parallel to main speakers. IMHO the only way you will damage your main speakers is by clipping your amp, not by putting too much power or too low a frequency into them.