What makes a sub musical? (1 Viewer)

[frank manrique]

quote:
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Nothing......if that's what you think is important. I mean this and I'm not trying to be a smart-ass.
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Worry not 'cuz no one will ever, ever accuse you of being an smart-ass, least of all 'lil moi!
By the way...what prompted you to even think of that? :wink:

Anyway...do you happen to know what the speed of sound is at sea level? Neither do I but will bet is just a little faster than 65 MPH or whatever speed you chose for your automobile analogy!

Cheers...

-THTS

"...hi, my name is Frank...and am an SVS bassaholic..."

 

[Chu Gai]

I asked my girlfriend what she felt about 12" or 8". She told me not to worry because I didn't have either.

Now just how far does an 8" woofer (subwoofer?) have to move to give you 110 dB if you're 3 meters from it?

 

[frank manrique]

quote:
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I asked my girlfriend what she felt about 12" or 8". She told me not to worry because I didn't have either.
__________________________________________________ _______

Stop it already...you're killing me!...

-THTS

"...hi, my name is Frank...and am an SVS bassaholic..."

 

[MingL]

Can someone actually measure the freq response and time decay of a "fast" sub and a "slow" one in the same room?

If someone can do both, then at least this discussion can actually be informative. Without these, there's really isn't much to discuss at all.

 

[Edward J M]

DavidLW - if a driver can play a given frequency without FR attenuation or break-up, it is "fast enough" on what you refer to as the starting side. How quickly a driver stops moving after the signal terminates is really what you need to focus on. This is the impulse response of the driver (in a given alignment).

A sealed true 2nd order alignment with a Q = 0.5 will exhibit the best impulse reponse. Note that the application of EQ will alter the impulse reponse, and many sealed subwoofers employ the same. The question (what Dave Alan and I were discussing above) is: Are differences in impulse response (all other factors being held equal) audible under normal listening conditions?

The amount of energy in the signal itself, and (by assoiation) the energy decay signature of the room, may very well overshadow (by orders of magnitude) the decay signature of the woofer. Like Dave Alan, I don't know the answer, but it would be nice to see some controlled studies that addressed this issue. Again, the challenge is holding all other variables equal while only altering impulse reponse.


The same potential for damage exists for both the 25 Hz tuned sub, and the 16 Hz tuned sub. Tom is simply saying that there is very little source content on DVDs/music below 16 Hz that could otherwise bottom out the woof of a 16 Hz tuned subwoofer. But there is plenty of strong stuff in the 18-22 Hz region that could damage a 25 Hz tuned sub, were it not for the presence of the steep slope HPF.

This isn't to say a HPF isn't a bad idea on a 16 Hz tuned sub; it's just not as critical of an issue.

 

[Jack Gilvey]

This can help clear up some of the confusion above on "woofer speed":

http://www.adireaudio.com/Files/Tech...ooferSpeed.pdf

Fwiw, if you haven't heard a dipole sub...you have no idea what a "fast" sub can sound like. Or, just take your sub outside.


Not quite, as Ed points out. The higher you tune, the more potential for overexcursion below Fb as the driver unloads.

http://www.hometheaterhifi.com/volum...ayporting.html

All else equal, the lower tune will offer more protection below Fb, but will increase the excursion above Fb.

 

[Manuel Delaflor]

It is interesting to see how fast this discussions about "fast bass" degenerate in extreme conceptual attempts to explain what everybody have in their heads.

Strange is that, like what happens with cable discussions, everybody is stubborn and thinks the only correct answer is the one he have.

IMHO, unless one have the opportunity to make its own tests, in the REAL WORLD, with a well developed methodology, all we are doing is wasting our time.

I know for sure that, if a sub is well designed, the only thing between us and its "musicality" is THE ROOM. Furthermore, most people I know wants to put their sub in a predeterminated location, instead of putting it when it interacts better with the particular room.

And we have the ones who try to tune it by ear!, when it is impossible to do it right unless one have the correct tools, at minimum an RTA with MLS capabilities and a calibrated mic.

Anyway, one is certainly free to think whatever he wants...

 

[Max F]

Thanks Ed for keeping things on the question that i was really asking. The whole fast woofer argument was settled long ago in my mind. A fast woofer is an oxymoron (sp?)

I'm asking about Group Delay. The whole room effect on sound decay is a very interesting and valid point.

What i'm worried about is if i buy an expensive subwoofer will i still end up with fat bass because of my room. What factors of a driver influences how it sounds (i.e., incorporates with my main speakers)? Is there real benefits to having a sealed subwoofer for music? Are there ported sub designs that result in minimal Group Delay (i.e., not audible)?

CAN A SVS SUB REALLY DO IT ALL!!!! Play great music and shake the foundations at sub audible levels... or is the idea of having a sub for music and one for HT a good one.

 

[Jack Gilvey]

This is, of course, the main question. A (monopole) sub will sound as "fast" or "musical" as the room allows.

 

[Manuel Delaflor]

Exactly, it is as simple as that. The room is far more important than the sub regarding its "musicality" or if it is "fast" or "slow"!

 

[dave alan]

I'll go on record here with a 'couldn't disagree more'.

Any serious designer or reviewer is gonna use the Govenment Standards anechoic chamber in DC or conduct ground plane measurements tests using known methodology and with repeatable results because it's the sub's ability to reproduce low frequencies that's at the top of the list...period.

The questions here are which test results will indicate, with the greatest degree of certainty, which subwoofer model will satisfy [MaxF's] personal listening/system criteria.

TV has said that 'tweako fast' jargon (which I am guilty of, I think) usually results from a preference for critically or overdamped response with a roll off corner that begins between 30-50 Hz. I agree with that statement, generally.

Edward has mostly indicated that he discounts group delay for various reasons and is currently exploring the possibilty that late release stored energy of various alignments may be audible.

Mark Seaton posted that the sub's integration with LCR, or, more specifically, the LCR speaker's ability to properly fill it's part of the transition from one band to the next should always be considered.

I've said that I believe the answer is to have 1 discrete redirected bass sub system and a separate discrete .1 sub system because it's much easier to implement than asking any sus system to do both at the same time.

Jack Gilvey has mentioned dipole subs and provided a very cool link on the basics of sealed vs ported.

Of course the room is a factor. But, it's a factor that can fairly easily be dealt with, vs purchasing, placing, calibrating and auditioning various expensive subwoofers.

 

[Edward J M]

Pretty much already been covered - the vented design will typically exhibit more GD than the sealed design. Until a more thorough study is done (instead of scientific extrapolation), keeping GD below 25 ms at 50 Hz and 50 ms at 20 Hz should keep that variable inaudible. Adire's recommendation of around 25 ms at 20 Hz is probably a fine design goal.

A vented design will exhibit a larger/longer impulse response than will a sealed subwoofer (up to Q about 1.5 IIRC). Whether this difference in IR is audible under actual use is up for debate; I'm keeping an open mind and hoping for some decent white paper on the subject. Certainly the change in FR when Q is altered (say from 0.5 to 2.0) in a sealed sub IS audible, but that's not the same thing, and the two variables shouldn't be confused.

I do think in the overall scheme of things, you will find your subjective impressions of a subwoofer's performance affected more by its in-room frequency response, room acoustics, and audible compression/distortion artifacts than by GD or IR. No matter what subwoofer you buy, make sure to get an in-house evaluation period to ensure its a good match for your room and your personal preferences.

Ed

 

[Manuel Delaflor]

Hey Edward, those are nice reviews. Have you encounter a room that was "boomy" even with a nice, expensive subwoofer? I have, and also rooms in which even a so called "slow" subwoofer would play "tight and fast". That is how I reached some of my conclusions, testing several subs in several rooms, with the help of some tools (ETF5, RS SPL meter and a laptop).

 

[frank manrique]

quote:
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I've said that I believe the answer is to have 1 discrete redirected bass sub system and a separate discrete .1 sub system because it's much easier to implement than asking any sus system to do both at the same time.
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You mean fully independent subs ("discrete redirected bass") and a separate discrete LFE (.1) sub system?

I strongly agree with that notion (if it is what I think it means) as I don't believe pre/pros or receivers that provide only one subwoofer output allows the necessary flexibility to really address this rather complex matter. However, whether that would satisfy those who insist on believing there is such a thing as "fast" and "slow" bass reproduction (yes...I do know that the ROOM plays a tremendous important role in the overall scheme of things, and doubly yes...I also do know sealed systems with Qs of .5 are nearly transient reponse perfect, blah, blah, blah...but will high-enders really care one way or another? Me thinks not!) or not still remains to be decided, hopefully with further serious scientifical research and tests ran by people who has good grasp of the laws of physics involved (btw, no boodoo pseudo-science practitioners allowed!)...

-THTS

"...hi, my name is Frank...and am an SVS bassaholic..."

 

[Mark Seaton]

Oh boy... Where to even start!


Sorry if this isn't overly gentle David, but I'm a bit tired and it's been a hectic week...

Please, if you want to attempt an explaination of what ideas you have, head over to the local library and check out a few texts on how loudspeakers operate.

For any conventional driver, your argument is baseless and has no relation to a driver's reproduction of sound. Acceleration is actually related to the resulting magnitude, not any sort of change. Making a given woofer, with a given motor heavier only makes it less loud/efficient in its passband. Likewise, when only reproducing low frequencies, all signals which make it through the low pass are slower changing. Anything with a sharp spike in the signal MUST contain high frequencies... Basic Fourier Transform stuff.

I had made too many posts over on AVS Forum in describing how woofers operate so far as motion, drive voltage, and acceleration. I will see if I can find them.

Cheers,

PS-dave alan: You should be able to acheive any benefits you might have in your dual re-directed bass scheme electronically with intelligent routing or settings and a common subwoofer output. If you think about the problem more realistically, few systems have more bass than they can put to use, so why split that capability in half when you have no way of knowing if the bass content is recorded in that way. With a common subwoofer setup you always have maximum headroom and the same known response no matter how the bass content was recorded.

 

[ScottCHI]

lmao


"Dropping science like when Galileo dropped the orange"

 

[dave alan]

Mark,

"...with intelligent routing or settings and a common subwoofer output."

That's a bit vague. I'd have to see a specific example to understand the benefit.

Low Frequency Effects and musical low frequencies are always inharmonic. However many subs with any amount of headroom can't play them summed as cleanly as 2 discrete systems.

A sealed, low 'Q' sub that begins to roll off @ 30 Hz can't handle the summed signal, but it sure does the music thing well for me (and apparently I'm not alone).

With simple signal/clip indicators you always know what content is where with discrete systems. It's when the signals are summed that you never know if and when there is signal in the .1 channel.

Splitting the signal adds headroom. If the LFE sub is only asked to play 115 dB peaks vs 121 dB (a rather dubious number that's floated around for years, nevertheless, it is the number used) peaks in the case of a summed signal, you have headroom. Or, in most cases, the option for a smaller sub.

Filters/slopes/level/EQ, etc. tweaks are mostly about reintegration of redirected bass and have much less to do with LFE. The LFE sub can be run 'stupid hot' with no effect on music reproduction, as the .1 channel is used very sparingly in the vast majority of MC audio discs and isn't utilized at all with the stereo CD format.

A simple flip of a switch sums the signals, making the discrete systems scheme backwards compatible. The summed signal scheme is what it is and offers no other option.

Most importantly, no more 'I love my sub for music, but it sucks with movies', or, the opposite, 'I love my sub for movies, but I have to tweak it for music playback' types of comments. Or maybe it's only me who feels these sorts of 'music vs movies' comments are rife. Actually, this thread is exactly the subject I'm referring to.

Just some not so random thoughts, FWIW.

 

[frank manrique]

quote:
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CAN A SVS SUB REALLY DO IT ALL!!!! Play great music and shake the foundations at sub audible levels... or is the idea of having a sub for music and one for HT a good one.
__________________________________________________ ________

Sure they can do it all...and how (yes...am quite biased 'cuz I own SVS products, but for good reasons, and no...I ain't appologizing for choosing them, so there )!

Mind you, with the exception of two VMPS subs, which were slot-loaded with a 12" active bass driver and a 15" passive radiator, all of my previous subbass systems, including some really, really "fast" and "musical"...ahem, I mean...WOOFER systems I built my self, were of the SEALED persuasion.
That also included the subbass system I used prior to doing the SVS move: a custom-built sealed Isobarik-loaded design that was engineered by Ryan Acoustics exclusively for me and which utilized two 15" drivers per coffin-sized, 350 Lbs. cabinets, so have a darn good idea of what am talking about in practical terms as opposed to just theorical.

You know, I've heard a good variety of subwoofer systems throughout my many years of involvement with consumer level (and a itsy-bitsy bit of professional level too :b ) audio reproduction, including the subbass section of earlier Infinity IRS models plus the V speakers as well, Wilson WAMMs and large newer ultra-mega bucks system--can't remember the model but looks like a stooping, wounded Robo-cop to me --a huge Fried-engineered (remember him?!) double transmission line monster that used two KEF B-139 bass drivers per channel (it was a Stereo subwoofer system built in a single cabinet--I still have the DIY building plans for it somewhere around here), an 18" version of the 1976 Audio magazine's vented subwoofer DIY project, a huge transmission line sub that used the 24" Hartley bass driver and which was a DIY project that appeared first in the Audio Amateur magazine than later on in The Speaker Builder journal (sorely missed!), an IB system that also used the then quite ubiquitous Hartley 24" bass driver that was mounted on a wall and loaded by the outside world (!), a prototype 18" bass driver-based subwoofer system engineered and built by Albert Von Swchiekert for one of his local adoring fans when he lived in the Riverside area here in sunny So. Cal. back in the 80s, and very large bandpass subs designed and built by Ryan Acoustics (a local speaker company long, long gone)...plus a myriad of other subs from companies such as M&K, Vandersteen, VMPS, Legacy, Thiel, Revel, Sumo (!), Klipch, Infinity, MacIntosh, et al.
Having done so has helped me to better understand the nature of the beast, as it were.

Even though am still contemplating doing a very large IB DIY project when I retire from work in a few years, the SVS subbass systems will remain the infrabass reproducing mainstay of my audio/video/film set ups for a long time to come.
And even though I have yet to tap their full potential (EQ'ing, more thorough calibration, etc.), am still enjoying the fruits of utilizing multiple SVS subwoofers, subwoofers that serve MUSIC as well as MOVIES extremely well and with equal quality.

I just got through viewing a concert by Chick Correa and The Acoustic Trio (John Pattucinni on upright bass and Dave Weckel on drums) on a high-definition taping from HDNet in Dolby 5.1 channel sound and you know what...the big B4-Plus allowed me to hear every single note that Patticinni played without exagerating the tonal nature of the acoustic upright bass instrument no matter how faint and delicate the playing...nor how ballsy it got. In other words...spite of being a vented system with group delays to contend with and all that is imputed to such designs, the mighty B-4+s allowed a tremendous degree of "musical" accuracy to emerge unscathed from the fray. No booms or one-note bass heard here...

Oh, yes...I also checked a High-Def taping of "The Fifth Element" sci-fi flick from an HBO airing and let me tell 'ya......them B-4+s sure shook the hell out of the floor, the rabbit on his cage, my dog Tonto, my daughter's birds (I think one of the parakeets keeled over because of fright! )...the whole damed house as a matter of fact so, yes...them SVS subs can do it all. Cheers!...

-THTS

"...hi, my name is Frank...and am an SVS bassaholic..."

 

[ChrisBee]

"One of the parakeets keeled over because of fright!"


They used to take cage birds down in mines to warn of impending danger frank!

Regards
ChrisBee

 

[Edward J M]

Actually, for a 5.1 system, if you add 105, 105, 105, 105, 105, and 115, you get about 117 dB. This assumes every channel contains a maximum bass hit at the same time. Of course DVD mastering levels seem to run loosey-goosey, and people tend to run the sub a little on the hot side for HT, so 120 dB seems reasonable as a requirement for the clean dynamic output of the subwoofer for handing both RB and LFE at/near Reference Level.

This of course is measured at the seating position; a tough challenge for any single subwoofer. Lesser subs will simply limit out and/or exhibit audible compression and distortion artifacts. Some people (like brick and mortar "sales associates") remain blissfully ignorant of these warning signs, and simply keep cranking the volume (gee doesn't it sound great?) until the sub starts bottoming and/or self destructs. True uncompressed, undistorted bass peaks in the 115 dB region, with average dialogue and playback levels in the comfortable and natural 85 dB region is both thrilling and safe.