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In Reply to: RE: Error in your logic posted by 3db on November 08, 2016 at 02:12:21
Personally, I would never opt to feed the mains "through" the subwoofer. The cheap crossovers used in many subs are not always transparent enough, at least not to my ears.I have always found it preferable to run the mains full range, as long as they are not teeny, tiny mains such as NHT Superzeros (for example) and maybe even if they are. I simply wouldn't trust the crossovers in most subs to divide the signal accurately.
Patiently going by ear (one speaker at a time if using two subs) while feeding the sub it's own dedicated line level signal, I blend in the subwoofer(s) using the lowest possible crossover point and the highest possible volume setting. As long as I keep the crossover setting below 60 hz or so (usually, it's closer to 40 hz!), I never have problems with the subwoofer(s) calling attention to themselves.
Also, I think that subwoofers sometimes create their own harmonics. Cabinet and/or driver resonances, mostly. Once again, keeping the crossover point as low as possible helps with this.
Edits: 11/08/16 11/08/16 11/08/16 11/08/16Follow Ups:
You guys are both generally on the right track. However, the focus on single-sub versus left and right subs, and crossover frequency/slope is misguided. For high fidelity sound reproduction, it is clear that the low frequency performance of the main speakers is critical. It's one thing to say that it's best to cross to a sub at 40-60 Hz, but if the mains crap out at 100 Hz, you're still going to have so-so low end. And, crossing at up to 60 Hz depends on the crossover slope. A single sub crossed at 60 Hz with a 12 dB/octave slope will still have localization problems, whereas one with a slope of 24 dB/octave will be less noticable. Also, this depends on the size and furnishings of the room.
The real important issue is to cross to the sub(s) at a frequency and with a slope which blends well with the main speakers. This is no different than crossing from the midrange to the tweeter - except for the wavelengths involved and the psychoacoustics - but the goal is the same: seamless integration of the drivers.
So, the concept/question of buying a "sub" or "subs" and where to cross over to it/them is secondary to the question of the capabilities of the mains. The mains will dictate the crossover and the one-or-two sub decision for you.
Put another way, the frequency at which it is crossed, and the crossover slope, is almost totally dependent on the performance of the main speakers in the low frequency range.
All too often, people think of subwoofers as an add-on. They're not.
:)
... that this was understood: When a crossover point around 60 hz or lower is used, the pair of mains must also have substantial bass output to 80 hz or below.For instance, early on in this discussion I suggested that tiny or bass-deficient main speakers might be best served by a crossover point higher than 60 hz and/or the use of two front-firing subs rather than one in order to fill in the missing bass and/or preserve stereo imaging, as needed...
No one I know would recommend the type of foolish "blanket approach" to subwoofer use that you describe. Not me, at least.
Edits: 11/08/16
The reason for two subs is to even out in room response, not for stereo effect.
Using measurements, I get the most linear response setting the subs to low pass at 70 hz - which allows for considerable output above 100 hz using a 12 db/octave slope.
The pair is used to eliminate localization.
What's that got to do with evening out in room response preventing or reducing peaks and nulls when walking around the room.
What's that got to do with evening out in room response preventing or reducing peaks and nulls when walking around the room.
I use a stereo pair to eliminate localization - that most annoying aspect of using a single sub since the most linear measurable response in my room dictates using a highish 70 hz 12 db/octave low pass - with audible output another octave above that.
Is eliminated by your crossover setting being below the threshold of localization, and not because you have 2 subs. The 2nd sub is there to smooth out the bass response in your room. Based on your pic, your only smoothing out the bass for a very small listening area at not for the whwhole room. That being said, I don't have a picture of the entire room so it may be working for you. Have you tried moving the second sub to another location to see if you could broaden the sweet spot for bass?
Edits: 11/10/16 11/10/16
In my living room, I tried placing a single sub in the available locations around the perimeter of the room but didn't get a satisfactorily flat response. The only good locations for a sub in my room which aren't in the way of foot traffic are at either end of the sofa. With the sub placed at one end of the sofa, and while sitting on the sofa next to it, it was still somewhat localizable even with a 40 Hz crossover point (mostly with HT effects, not so much with music). I solved this by placing a second sub at the other end of the sofa and balancing their levels by ear at the sweet spot. Now they completely disappear unless you put your head within 2 feet or so.
So I think using multiple subs can help with localization as well as evening out the response.
Hey 3db (which I would write as 3dB, but that's another topic), you're on the right track, but missing the all-important details.
Crossing below about 80 Hz, which is generally where we can start to perceive the source direction of a sound, does not mean that the "sub" does not produce output above that frequency. The "slope" of the crossover is just as important as the x-over frequency. For example, say the x-over is 60 Hz, with a slope of 12 dB/octave. This means the sub output is down 3 dB at 60 Hz, and is down 15 dB at 120 Hz. Without a calculator and the formula handy, let's say the sub output is down about 8-10 dB at 90 Hz. That is readily audible. That is one reason why two subs are often necessary, placed near each of the main speakers.
As I've written multiple times, buy "Why You Hear What You Hear".
:)
I use the AVR'S digital filters set at 80 Hz which I believe to be 2nd order filters with a 24 dB per octave roll off. Maybe that's the reason for not hearing any localization.
you don't understand how crossovers work or don't share my hearing acuity. I'll repeat my observation:
"...using a highish 70 hz 12 db/octave low pass - with audible output another octave above that."
Simple test Sparky - turn off the main amplifier and one sub while playing bass content. I just did that again to validate my earlier experience.
Perhaps you cannot localize sound an octave above that crossover point, but I can assure you that I can.
from you is nothing new especially when you feel challenged. I didn't mean to kivk your delicate but insanely large ego. Later sparkey.
Does your simplistic evaluation hold true in your room using a 12 db/octave slope?
I prefer the accuracy of digital filters to achieve my end results. Your so called tests are filled with sight bias. Your apparent lack of localization due to stereo subs has eliminated localization to one sub. However, the localization is now set to a pair of subs sitting in front beside your speakers. If I were to walk around your room, I would hear uneven bass response depending where I am standing.
Your so called tests are filled with sight bias.
How little your assumptions about me are accurate! I always close my eyes to evaluate audio gear.
In fact, one thing that annoys me about my Polk center speaker is that it is a two and a half way design. Which generally is a good thing and works fine in a vertical position. Although the cabinet is truly centered, I am aware that the origin of most of the sound is slightly to the right where the "midrange" driver is located. It would block the screen if I stood it up and it's as wide as the rack so I really cannot shift its lateral location nor the rack itself.
Your apparent lack of localization due to stereo subs has eliminated localization to one sub.
This is what I'm saying.
If I were to walk around your room, I would hear uneven bass response depending where I am standing.
Not only do I agree, I've measured it! Unlike my dedicated music room, the HT is in the family room where my options for placement are limited. On the other hand, I don't walk around the room while enjoying the HT. :)
Ideally, I would like to have a set of The Swarm designed by fellow inmate Duke LeJeune.
Congrats. That's great.
As I have always said, everyone should do whatever works best in their own system. For me and my stereo systems, lower crossover points have always sounded best.
If you are able to cross a single sub low enough to avoid localization, you most likely don't need one!
My standmounted mains go flat on their own to only 70 hz or so. Running the mains flat with separate line level to sub, a crossover setting of 40 hz, a 12 db sub slope, plus room gain, I get flat or slightly recessed bass response in the blended crossover region with beefy bass response starting down low at around 30 hz.Sounds about perfect to my ears, others might come up with different solutions.
Edits: 11/09/16 11/09/16
I think that most people here would avoid speakers so small that they output little or no bass below 100 hz (NHT Superzeros, etc...), but two subwoofers ARE sometimes necessary to preserve stereo effects with such speakers.Because stereo exists in at least some modern recordings from about 80 hz on up, using a single sub for a pair of very tiny mains like the Superzeros could cause you to lose that stereo info in the region of 80 - 100 hz. Unless you smoothly fill in the gap in response, that is. Granted, we're talking about a relatively miniscule loss of stereo info here but when listing to a recording of a solo male bass singer (for example), you probably wouldn't want to hear imaging cues toggling between two stereo speakers and a single subwoofer near the bottom of the bass singer's vocal range...
The way to fill in stereo the gap in such cases is to use two subwoofers, one for each speaker. Each subwoofer should be as close to the tiny main speakers "midrange/bass" driver as possible, in order to maintain maximum preservation of stereo info in the upper bass range.
However, if you listen exclusively to vinyl (or bad modern digital recordings) on a pair of Superzeros (or something similar) you should probably not worry about preserving stereo info in the 80 - 100 hz region, as recordings from the vinyl era typically had summed or mono bass from 100 hz on down. With vinyl, you can use only one subwoofer with a pair of of speakers like the Superzeros, if you are so inclined.
All that said, I would agree that two (or more) subs can also help smooth out bass response, at least in some cases. So two or more subs are almost always a bonus IMO.
Edits: 11/09/16
Given the number of threads and related questions about incorporating subwoofers (which I've always thought of as "woofers"), it would seem that your assumption is incorrect.
Otherwise, this wouldn't even be a topic.
:)
"Also, if your main speakers are small enough to warrant a high subwoofer crossover points (80 hz or higher) you might want the option of pointing subwoofer drivers toward the listening position (after you've placed each of two individual subs as close to the main speakers as possible). The goal being the best possible driver integration between mains and subs when higher subwoofer crossover settings make your subs produce some amount of uni-directional bass."
Although it's not "uni-drectional", I understand what you mean, and your understanding is basically correct.
:)
Yes. When I wrote "...*some amount of* uni-directional bass..." I figured What we understand stereo to be would be understood.
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