How to prove someone an 8" subwoofer isn't "tighter" than a 15"???

[fjhuerta]

I was talking on another forum about my room needing some bass treatments, since there were too many bass modes. Someone asked me what size my sub was. I told him it was a sealed 15". He said the problem was my sub, since 15" were "loose", and I'd be better off with 3 or 4 8" drivers.

I was like... ahem... "loose"?

I thought about how to answer him. Didn't, because it seemed to me he wasn't really a DIY person.

But, would the correct answer have been "there are no "loose" subs, just badly designed ones. Group delay and Qts define how "tight" a sub sounds. A sub with low group delay and Qts lower than 0.707 will be "tight"".

Would that have been the correct answer?

Or, are 15" subs "loose" and 8" "tight"?

[the kid]

Re: How to prove someone an 8" subwoofer isn't "tighter" than a 15"???

I can't answer the ins & outs about science of what makes a speaker what it is, but I do know from experience that 2 subs vs. 1 sub can improve what I call "fill-in" of bass in a room. They claim low bass (subs) are non-directional and if loud should be plenty, however, I could spot the sub source point in my room from 1 15" sub. I replaced this with 2 12" subs. Now things are more encompasing and I think better quality.

Tighter?...Looser?...not sure if I notice. Just definitely better.

p.s...I can sell my 15" if interested...;)

[johnnyrichards]

Re: How to prove someone an 8" subwoofer isn't "tighter" than a 15"???

You cannot, that notion is extremely ingrained in the audiophile population. Along with several dozen other audiophile myths they hold dear.

He is right about one thing, multiple subs are the answer to good bass.

[hipcheck]

Re: How to prove someone an 8" subwoofer isn't "tighter" than a 15"???

This is not a battle that can be won....however I really get annoyed when dealing with those who buy subwoofers based on "it is a 1000W sub". A dubious pickle trying to explain the facts of making a purchase based that fact.



Steve

[billfitzmaurice]

Re: How to prove someone an 8" subwoofer isn't "tighter" than a 15"???

But, would the correct answer have been "there are no "loose" subs, just badly designed ones. Group delay and Qts define how "tight" a sub sounds. A sub with low group delay and Qts lower than 0.707 will be "tight"".

Those terms are used by laypersons who don't know how to describe what they're hearing in engineering terms, so each person will have their own definition of what 'loose' and 'tight' actually mean. That being the case your answer is as good as any, though group delay in subs is inaudible. In any event when the responder can't provide any objective engineering facts to substantiate their subjective opinions don't bother to respond, you're wasting your time.

I do know from experience that 2 subs vs. 1 sub can improve what I call "fill-in" of bass in a room.

+1, it does so by smoothing room modes.

They claim low bass (subs) are non-directional

That's not a claim, it's a fact.

I could spot the sub source point in my room from 1 15" sub

If you did it was by hearing above bandwidth harmonics, indicating that either your crossover was set too high, had insufficient slope or your sub had a lot of THD, or a combination of the three.

[cjd]

Re: How to prove someone an 8" subwoofer isn't "tighter" than a 15"???

You could always offer to shove it where the sun don't shine (as the saying goes...)

I bet the 15 will be tighter...

Smaller drivers probably don't go as low and a lot of people perceive subsonics as "loose" - probably because they're even more likely to excite room issues. My HT loads spectacularly at 22hz for example. Walls flex and stuff. Quad opposed mounted (manifold) IB with the tempest-x ...

[Face]

Re: How to prove someone an 8" subwoofer isn't "tighter" than a 15"???

Smaller drivers probably don't go as low and a lot of people perceive subsonics as "loose" - probably because they're even more likely to excite room issues.

Add in the tall upward slope of room gain at lower frequencies and this is exactly why some come to this conclusion.

[Tin_Ears]

Re: How to prove someone an 8" subwoofer isn't "tighter" than a 15"???

My answer would be, "Oh, yeah. Eight inch drivers are great for mid-bass. I'm asking about subwoofers. Thanks for your input. (grin-smiley)"

[the kid]

Re: How to prove someone an 8" subwoofer isn't "tighter" than a 15"???

"He said the problem was my sub, since 15" were "loose", and I'd be better off with 3 or 4 8" drivers."

Should have told him that was impossible as your 15 is a Bose! The best there is!:rolleyes:

[Sydney]

Re: How to prove someone an 8" subwoofer isn't "tighter" than a 15"???

They claim low bass (subs) are non-directional..

There are ways to control bass directivity. The core issue is that bass frequencies are larger than 11' in length below 100Hz.
Much larger than the devices that generate the sound. This is not a concern in a small area but is important in Live Sound in large area.
Those lucky enough to not have room mode and node issues can take advantage of clustering multiple subs for mutual coupling gain.

[fbov]

Re: How to prove someone an 8" subwoofer isn't "tighter" than a 15"???

I've always been drawn to Steve Callas explanation of the LLT:

http://www.hometheatershack.com/forums/diy-subwoofers-general-discussion/1820-llt-explained.html#axzz2C7UOREFe

"A logical goal is to make the driver solely responsible for output down to at least ~30hz, as the frequencies above that are where the bulk of musical bass lies and where accuracy is most critical. ... The more capable the driver, the better the accuracy will be."

While the LLT discussion doesn't apply to a sealed box, I see no fault in his logic regarding accuracy of frequencies being directly radiated from a driver - the better the driver, the better the sound quality.

The one flaw is addressed by the crossover to main speakers. Subwoofers have heavy cones - high Mms - and mass resists acceleration, so there's a logic to the arguement that smaller drivers respond better. That logic is refuted by the proper choice of frequency range - at 30Hz, the little sub will be at resonance, struggling to move air while the bigger one willl still be in the linear response range. At 300Hz, the situation is reversed, as expected, but question's rendered moot by the crossover roll-off.

I also have a sealed 15, and I have no issue hearing differences in pedal drum set-ups, the kind of fine detail I would expect to lose if the bass were "loose." And having seen pictures of your room +1 on the acoustic treatment path!

HAve fun,
Frank

[the kid]

Re: How to prove someone an 8" subwoofer isn't "tighter" than a 15"???

It is possible, well more like highly probable, that since I knew it was 'there', that is where I heard it from. I am learning that things affect the sounds such as harmonics, reflections, crossover point...but regardless (due to my lack of education/experience) I registered 'back corner bass' during movies and it really bugged me. So, for my part, 2 12's seems to have fixed the issue. I am sure things can be tweaked to make it better, however simply making 1 into 2 subs is working.

[Sydney]

Re: How to prove someone an 8" subwoofer isn't "tighter" than a 15"???

... I registered 'back corner bass' during movies and it really bugged me. ....

I don't like that either - but i do appreciate that for some it is not an issue and for others part of their goal.

[billfitzmaurice]

Re: How to prove someone an 8" subwoofer isn't "tighter" than a 15"???

ISubwoofers have heavy cones - high Mms - and mass resists acceleration, so there's a logic to the arguement that smaller drivers respond better.

Logical, yes, until you know the facts. The electromagnetic force of the motor so totally dwarfs the effect of inertia as to make it irrelevant; inertia only comes into play when the signal ceases. A good thing too, otherwise moving coil drivers simply would not be capable of accurate sound reproduction. It comes down to the driver cone having to cope with operating within the realm of the speed of sound, while electromagnetic forces operate within the realm of the speed of current in the voice coil, about 0.7 the speed of light.

[curt_c]

Re: How to prove someone an 8" subwoofer isn't "tighter" than a 15"???

Driver induced distortion products aside, the driver frequency response completely describes its behavior. If two different drivers, say an 8” and a 15”, have identical passband transfer functions, they will sound identical, regardless of any T/S parameter differences, as their impulse response will also be identical.

More telling, as others have suggested, is that below the Schroeder frequency the relative sparsity of modal behavior results in the increased audibility of individual modes. Since subwoofers passband is generally entirely below the Schroider frequency, the position and number of sources will affect the number of modes excited and their relative levels.

C