Originally Posted by Adamg (Ret-Navy)
Enjoy reading your discussion with @darthray
. Very instructive.
However, as I was reading your further refinement of what you mean about the Front Speakers ability to play with authority @ 80Hz, I began to ask "How does a person go about testing this ?" My thinking was that maybe adding a link to, or adding descriptions and/or procedures on how to test individual Speakers to determine their natural rolloff of lower HZ capability.
I venture a bet that many readers, go by what the Manufacturer States is the Low end capability of their Speakers. We know that this information can be considerably "Overstated" by the OEM's and it does not take into consideration the actual "Room Mode" reinforcement that may or may not be improving/impairing each specific Speaker. Cascading Crossovers do work, as I can attest.
But one needs to know the actual rolloff frequency of each individual speaker. For instance, I have two similar front speakers as my L&R. My AVR only allows me to set the Crossover for "Both" Front Speakers. There is no individual Speaker Crossover setting. Some may assume these Speakers will roll off at the same FR. This could be an incorrect assumption based on room reinforcement effects. Therefore I need to know exactly where each (FR&FL) speaker rolls off. Then I should take the Highest number of the two to use as my basis for setting the Front L&R crossover setting.
Do I have anything incorrect in the above? Always happy to be corrected if so.
Again, I wish to commend your work. You constantly strive and achieve a remarkably high level, of communicating the extremely technically complicated, in terms we "Knuckle Draggers" can clearly comprehend. Bravo Zulu Sir!
Here are a few links that may be useful and could be referenced to provide Users with additional info on how to test their speakers:
It's nice to hear from you, and those links should be helpful to people. Speaking as a fellow knuckle-dragger, I appreciate the compliment!
I agree with your post, but I also think it is important to distinguish between setting crossovers in general, and using cascading crossovers. Nothing about rolling-off bass frequencies faster above a crossover should jeopardize the speakers. So, the real question is how should we set crossovers to begin with? Ideally readers of the Guide will read the subsections of Section III consecutively, starting with Section III-A: Crossovers From Speakers to Subwoofers
In that first subsection, I recommend a somewhat conservative approach to setting crossovers. Most (nearly all) modern AVR's are going to measure the frequency response of the speakers in an HT system, and set crossovers accordingly, even if they don't necessarily have advanced programs for automated room EQ. Where the auto-calibration programs are measuring a speaker or speaker pair, they are doing so based on the specific speaker location in relation to the MLP. (And, they always round crossovers up, based on the capability of the weaker speaker in a pair.)
My typical advice, for crossovers set below 80Hz, is to raise the crossovers to at least about 80Hz. (Section III-A goes into some detail on this.) Ideally, I would like to have about an extra half-octave above whatever frequency my AVR set my crossover at. But, FWIW, I think that extra half-octave of headroom becomes a little less important above about 80Hz. So, if a speaker is right at 80Hz, post-calibration, I might or might not increase the crossover post-calibration.
A lot would probably depend on my listening levels. If I rarely listened above about -15 MV, I might leave the crossover set at 80Hz, where the calibration process put it. If I listened louder than that, I would probably raise the crossover to 90 or 100Hz in order to let the subwoofer(s) carry more of the load. So, I see some degree of judgment involved in this question.
Should the average listener measure his speakers separately if he doesn't have an auto calibration program, or should he do it in addition to relying on the auto calibration process? The second part of that question is tougher than the first part. I agree that we can't just rely on manufacture's specs for a couple of reasons, including speaker placement in a room and spec reliability. But, we usually can rely on auto-calibration routines, if we are also exercising some individual judgment as noted in the last couple of paragraphs.
If someone needs to measure his speakers independently, or just wants to do it for his own information, there are some different ways to do it. He can start with some test tones and a Radio Shack SPL meter, and he can continue with REW tests for frequency response, distortion, and compression, at various volume levels.
I think that for most people reading this thread, a combination of auto-calibration and some common sense will probably be sufficient. Most of us will hear our speakers start to strain a little if we push them with too much volume. And if we do hear that, setting a higher crossover may help, since it will increase the speaker's overall headroom. (Reducing the volume will help, too.)
That straining sound, which characterizes distortion, would be the opposite of the clarity that cascading crossovers are designed to provide. But, nothing about cascading the crossovers to increase the subwoofer roll-off, above the selected crossover, should have any negative impact on the speakers. They are still playing exactly the same frequencies, at exactly the same volumes, that they would be even if the subs weren't rolling-off faster.
It's an interesting discussion, and I hope that my answer helps for others who may be reading along. (I will go back and see if I need to beef-up anything in Section III-A.)