whats the point in having more than 1 really good subwoofer? - Page 2

Search room modes. And read this, or similar works by Floyd Toole or Earl Geddes.

http://www.harman.com/EN-US/OurCompany/Innovation/Documents/White%20Papers/multsubs.pdf

One man's headroom is another man's overkill. But seeing overkill as obscene is making a value judgment. If you have something you'd like to spend your time and money on rather than subwoofers, go right ahead. I suggest getting to that immediately.

You could never get the most out of a BMW m3 legally on US public roads either, but people use them as commuter cars. And if I had the free cash, you can bet I would too. It would just be so delicious and effortless.

Sorry but I have to say bad comparison. The M3 is a much more complicated machine than a sub. And there is much more to the experience than top speed. The word "headroom" would likely be the only similarity if you were to compare the 2. And when youre comparing the M3 to having 10 subs it becomes completely invalid.
I would compare it to something more like hunting squirrel with an elephant gun.
Edited by Bond 007 - 3/16/13 at 6:38am

A 90dB machine is one thing, however 90dB playback of bass frequencies is entirely different.

Subwoofer range can easily require 60dB or more to equal the same perceived loudness of a machine.



Our hearing has a dynamic range. It's determined by the lower limit of the audibility threshold, and the upper limit the threshold of pain. Key to your issue here is the threshold of hearing is not the same SPL at all frequencies. This varying rate of sensitivity also changes with level. This is represented by the Equal Loudness Curves.

"Examination of these three curves makes it evident that there is considerable difference between the ear's response at different sound levels. The response to very loud sounds is much "flatter" or more uniform than the response to very soft sounds".

If we start with 1khz as a reference, then the audibility of 100hz requires 25dB more sound pressure merely to be just audible. However, the fascinating aspect is it changes, flattening out as levels increase.


If you set up your system balance to your liking at any given level, then subsequent listening at a lower level then the perception will be an anemic, reduced bass playback. This is how the old loudness button came to be, ... as it boosts the bass to compensate for your low level listening. Typically, playback generally sounds a bit better when somewhat louder. At higher levels, we possess a better balance to our hearing perception than when listening at lower levels.


Now specifically in the deep bass, our audibility to hear 20hz requires about 70dB. That's about 40dB or so greater than 100hz.

Way down into the deepest octaves of music and movie reproduction, we require even greater sound pressure levels to experience the effects.

As stated it takes about 70dB at 20hz for audibility, however audibility at 16hz requires about 90dB. So, as one can see, just because you say 90dB machine requires hearing protection, that doesn't mean that same SPL is offensively loud in the bass, and deep bass range.



I hope this helps.

Fun stuff on a Saturday

First, it seems to me that the title of this thread should have been: "I don't see a point in more than 1 good sub." instead of posing your opinions as a question for others to answer. Be that as it may, some simple facts:

You mentioned "... accurately reproduce...". Let's look at an example (one of thousands that exist in modern movie soundtracks with more being added every year), a scene from War Of The Worlds, chapter 9, the plane crash scene. This is a direct comparison of the digital feed from the player vs the subwoofers mic'd at the listening position:



Note that my multiple enclosure system "only" accurately reproduces the content to 3 Hz, whereas the actual content is substantial to below 1 Hz. The only subwoofer available for purchase on this planet that will accurately reproduce the low end of this scene is the Thigpen Rotary Woofer, but it can only handle up to around 20 Hz or so, which requires a multiple sub system.

IOW, if you know of a single "good" subwoofer that can "accurately" reproduce this scene, you're definitely holding out on me and it would be great if you'd share that information.

Also note that the digital capture of this scene shown above was taken from the FL/FR channels ONLY.

Also note that the requirement for lots of displacement (multiple subs vs a single 'good' one) is only a part of the equation. As I've said ad infinitum on these boards over the years; if it ain't goin' in, it ain't comin' out.

The signal that is fed to the subwoofer must first be read, decoded, processed, converted to analog, reconverted to digital, processed again, reconverted to analog and amplified. Every commercial subwoofer available today then adds further processing before the drivers, to 'protect' them from ever having even a chance to accurately reproduce scenes like the one captured and posted above.

That process from the player to the AVR to the outboard EQ to the amplifier to the driver rolls the original signal off so that it is down -15dB to -30dB or more by the time to gets anywhere near an accurate version of the original content in the bottom octaves. This is the result of circuitry built into every analog output stage of every piece of AV hardware that rolls the signal off to assure against DC offset, which causes bad things to happen. Most every one of them takes the safe route of affecting the signal with a roll off in the 5-10 Hz octave, and many even higher, making it impossible for the subwoofer (regardless of its touted prowess or size) because the subwoofer never sees the signal at all.

So, say you carefully hand pick and/or design and hand build every piece in the chain to assure a signal chain that's flat to 3 Hz (+/-) 3dB. And you search the world for an amplifier whose circuitry allows for amplification of complex signals that dwell in the underworld, where very strange things happen that don't happen >20 Hz. Excellent! You now have the potential to exist nearly alone in a unique and tiny niche. NOW you can focus on the accuracy of the reproduction of that signal containing the low end from any or all satellites and the LFE channel, all redirected to your subwoofer.

And...

A single subwoofer will not do the job at 0dBRL at your ears. I don't care who thinks otherwise, I'm not stating my opinion on the matter, so take that FWIW.

I would also like to comment on the comparison of momentary bursts at 120dB from your subwoofer vs industrial noise exposure. OSHA, and virtually every jurisdiction in the US, define all noise statutes and guidelines with A weighting. Please search that metric and you'll see that it excludes all frequencies in the subwoofer range. That's for good reason, which you can read all about with the click of a mouse.

It's interesting, you never ever see the OP in threads like this come back and say, "oh I get it now, I was wrong. Thanks for all the detailed information guys." Ha, I'd love to see that just once.

Multiple subs to single sub is just like employing 4 Arnold Schwartzneggers in their youth to lift PB13 Ultra. While one could very well lift it but could barely move, two could carry it easily but move slowly, 3 could walk with it but cannot run, 4 will just hold it high up on their heads and run.

Multiple subs IMO has nothing to do with playing at crazy loud levels above 120dB at home. You can stay within reference and enjoy the majic of multiple subs. They just increase dynamic range tremendously, reduce distortion, even out sub response accross wider listening area if not co-located, effortlessly reproduce power hungry bass frequencies with less cone movement, and the list doesn't finish here.

Another good read on multiple subwoofers, including real data on the reduction of frequency response variance with changes in listener position is the AES paper by Welti and Devantier (of Harman) called Low-Frequency Optimization Using Multiple Subwoofers.

Water brothers!

bb, what settings are you running the fft in spectrumlab?

Some pretty funny trolling. This forum has been pretty troll free lately. Remember the days of Vasay?

Word. I picked that up after the second response.

Hilarious. I love the unflinching response by Mr. Fitzmaurice in reference to Toole and Geddes. Well played, sir.

I'll give anyone the benefit of the doubt and assume they have a legitimate question. If that's the case he got his answer. But if he turns out to be a troll I'm not one who's going to feed him.

sometimes, other folks read along, but don't post. his was a good question troll or not.

i couldn't find the original source for the 115db lfe spec. does anybody have a link to that?

do we know when and by whom it was established?

The resolution for SL is accomplished through the Audio I/O and FFT in conjunction with the decimation numbers. I experimented with so many combinations that I don't recall the final without looking at my settings in the software. But, I put them in an ins file that anyone can upload them into SL and be done all at once.

They're on my site. scroll down the page to "download Spectrumlab" and the down load is a zipped folder with SL in one folder and my .ins settings file in another inside.

http://www.bossobass.com/Bossobass.com/Technical%20%28cont%29.html


THX after a movie George Lucas did called THX 1138. Lucas liked to reference it as a private joke. Harrison Ford's muscle car had THX on its license plate in Lucas' American Graffiti.

Tomlinson Holman, who designed an electronic crossover to accommodate bass management as part of his standard was noted as TH X-over. When one Lucasfilm guy (forget his name) who was considering a name for the whole affair, looked down at his notes, saw TH X-over which triggered his awareness of Lucas' fondness for the anagram and a light bulb went off. Thus, THX.

The patent for digital bass management to handle all 7 Dolby AC-3 Configurations actually belongs to Cirrus Logic, which patent I read many times 10 years ago to wrap my head around the bass management possibilities. When I was looking to put a measurement rig together and consulted some top names in the acousticians world, one of them, after asking me what it was I wanted to measure and I replied, said, "Hmmm, Tom Holman would be the guy to ask some of the Qs you have. He owes me a favor. Here's his cell #, call him and mention my name and see what he can tell ya." That was pretty cool and I unded up with a measurement rig I've never had any regrets forking the dough over for.

The patent can be found here:

http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=7&f=G&l=50&co1=AND&d=PTXT&s1=%22bass+management%22&s2=%22cirrus+logic%22&OS=%22bass+management%22+AND+%22cirrus+logic%22&RS=%22bass+management%22+AND+%22cirrus+logic%22

An excerpt follows. I always found it interesting and have asked about it to no avail over the years, but it clearly describes the LFE+10dB spec.

The techs hired by Lucasfilms to digitize the studios went on to form Pixar.

Holman's THX work was late 90s and the Cirrus Logic patent is 2002.

This is from what I recall, FWIW. A search of those names and players will unearth a wealth of history for anyone interested.

how about this answer.

cause I like bass.

I really did think he/she was asking out of a scientific demeaner. I said, " sniff sniff " smells like a troll..... Orange feet, feathers and a bill...... could be a duck...... Oh well, back under the bridge for whence you came.

But many are still crawling around on the the floor, looking for the spot that sounds the best using their ears, just like the guys at, say SVS who build them for a living. I mean all those wonderful subwoofers sitting in the wrong place because the owner decided to disregard the need to continue the science after their sub leaves the factory. Its just as bad as the original poster.

I hand the soapbox over to the next man/woman......

A very good friend was looking at my laptop, OmniMic system and MiniDSP software, and hard ware and said they had no idea the hobby was so technical.

I replyed that once you get measurement gear, you've put your poor system under a microscope and you mite as well throw away preconceived motions or romance about your systems performence, it will soon be very obvious what its doing and why.

Which leads me to my close, its a journey...... open your eye's wide enough to learn what went into developing a subwoofer, amp and EQ. Read, read, read....... dont look for a destination of sorts....

The OP's just trolling, any fool can read a few threads and understand why guys want multiples.

thanks bb. if i happen to find an original specification document, i'll post it.

Troll...possibly, looked at his profile, he likes to make a thread and see what happens.
His claim to AVS fame is the 2,000+ post thread Are audio companies all involved in a huge conspiracy? , he started it




and posted once more 4 days later....


Me....I just sealed my 3 cu ft sealed subwoofer interior seams, taking a break before putting the front 2 baffles on....so does that make me a troll for posting in this thread w/o any discussion point except the above

Measurement gear is the Pandora's Box of audio. You will never be the same, and cannot undo it. How many here remember the single sub days with a quasi-blissful ignorance, because Jesse Ventura's gun in Predator sounded so badass compared to through the TV speakers?

JSS