Why the fuss with subwoofer specs and brands?

[krabapple]

Even with a bare instrument into a DI box you have the FR of the pickups themselves - any device that depends on a conductor moving through a magnetic field needs AC input (literally, movement) and will have low frequency rolloff. Popular transformer-coupled DI boxes also have a low frequency rolloff - again, DC doesn't go through a magnetically coupled coil.

Well, yes, there's what I noted...if there's rolloff without a cabinet, it's built in to the pickups (plus whatever might be added in the downstream signal chain)

Now, tell me what bass rolloff I can typically expect, from, say, a stock Fender Jazz neck pickup.

 

[sarumbear]

[edit: I've done this to some Center channels too. Typically I'm talking about old quad releases that were 'repurposed' for releases a 5.1 without actually going back to the multis for a remix]

They are like stereo versions of early the Beatles albums.

 

[witwald]

That was what I meant when I talked about bass player misconceptions. A rational person thinks "Low E is 41hz, if I pluck a low E, I will get a 41hz sine wave." You very much don't, what you get is a lot of 2nd harmonic with a spray of higher harmonics changing as the note decays.

Measurements of music recordings actually do show very strong peaks at 41 Hz at the bass end of the frequency spectrum. They can be much higher in amplitude than the content around 82 Hz.

For instance, compare a 41hz test tone here with the low E sound here - you can tell there's a lot of higher frequency tonal content and it is likely difficult to impossible to hear any of the fundamental.

But won't the result depend on the frequency response of the reproduction equipment? A simple measurement will show what's really there, irrespective of the performance capabilities of the reproduction chain.

 

[witwald]

Now, tell me what bass rolloff I can typically expect, from, say, a stock Fender Jazz neck pickup.

That would be interesting to know. I wonder if anyone can connect a vibration shaker to a string on a bass guitar and measure the output of the pickup as a function of frequency?

 

[ryanosaur]

So, to be clear, you turn off all your speakers, put your sub on the floor at your MLP. Play some bassy content while you crawl until you find a nice sounding spot. Then put the sub there. Then put an Audyssey mic at the MLP (ear height), run Audyssey, and examine the 'before' measurement when it's done? (Is Audyssey OK with only having the sub on, no other channels?)

Then rinse and repeat all that as needed to find the best 'before' measurement?

Ah, I do love this hobby.

More or less...
When you run Audyssey it will want to do the full protocol, which I think you can stop after one full set of sweeps.
And of course, you are limited to how many discreet Sub Outs you have, as anything more would require REW and an external hub like mDSP2x4.

Again... it's crude.
But functional.


As far as what I was working with, my front corners were inaccessible, but also super boomy and muddy. The only spot on my back wall that could take a sub was a null. I didn't check IN the closet. The side walls were super clean for several feet and so I had a good range of placement opportunities. I think I moved one of them a few inches after initial setup.

 

[poxymoron]

So while we're discussing subwoofers, and I know this has been dealt with countless times elsewhere on ASR, does subwoofer corner placement only add output (on all the sub's frequencies) or will it add add/aid low frequency extension? I suspect that the answer will not be black and white. Thanks.

 

[witwald]

...does subwoofer corner placement only add output (on all the sub's frequencies) or will it add add/aid low frequency extension?

Subwoofer corner placement will essentially add output at all the subwoofer's operating frequencies.

If we take the LFE channel, it is usually working with frequencies up to about 120Hz. At 120Hz the wavelength of sound is 2.8 meters or so. If the distance of the subwoofer radiator from the walls and floor surfaces is less than 1/10 of a wavelength, the the full room gain effect from corner placement will be obtained. At 120Hz, 1/10 of a wavelength is 0.28 meters. Hence, this indicates that a corner-placed subwoofer will be able to achieve full room gain boost across its entire operating frequency range.

 

[poxymoron]

Subwoofer corner placement will essentially add output at all the subwoofer's operating frequencies.

If we take the LFE channel, it is usually working with frequencies up to about 120Hz. At 120Hz the wavelength of sound is 2.8 meters or so. If the distance of the subwoofer radiator from the wall and floor surfaces is less than 1/10 of a wavelength, the the full room gain effect from corner placement will be obtained. At 120Hz, 1/10 of a wavelength is 0.28 meters. Hence, this indicates that a corner-placed subwoofer will be able to achieve full room gain boost across its entire operating frequency range.

Thanks for the reply. I read recently on ASR (cannot remember where exactly) that it helps the subwoofer play lower, but I wasn't convinced.

 

[Chrispy]

Thanks for the reply. I read recently on ASR (cannot remember where exactly) that it helps the subwoofer play lower, but I wasn't convinced.

Would be nice to review what you are referring to. Sub output is what it is, the room can either help or not....but can't actually increase lower extension.

 

[poxymoron]

Would be nice to review what you are referring to. Sub output is what it is, the room can either help or not....but can't actually increase lower extension.

I'll see if I can find the post.

 

[Chrispy]

I'll see if I can find the post.

I may have been to brief, just that the sub has limits....your room can enhance/detract as placed but just not particularly improve extension otherwise.

 

[ryanosaur]

Would be nice to review what you are referring to. Sub output is what it is, the room can either help or not....but can't actually increase lower extension.

But cabin/pressure vessel gain can benefit extension in some cases...

So while we're discussing subwoofers, and I know this has been dealt with countless times elsewhere on ASR, does subwoofer corner placement only add output (on all the sub's frequencies) or will it add add/aid low frequency extension? I suspect that the answer will not be black and white. Thanks.

Smaller closed rooms, say 3000cu.ft and below will begin boosting at a frequency [wavelength] equal to twice the rooms longest measurement (up to around 20'). This is mostly associated with Sealed Subwoofer performance and should not be confused with Boundary Gain. Corner Loading is Boundary Gain.
Perhaps this is what you are thinking of?

 

[rcstevensonaz]

But cabin/pressure vessel gain can benefit extension in some cases...


Smaller closed rooms, say 3000cu.ft and below will begin boosting at a frequency [wavelength] equal to twice the rooms longest measurement (up to around 20'). This is mostly associated with Sealed Subwoofer performance and should not be confused with Boundary Gain. Corner Loading is Boundary Gain.
Perhaps this is what you are thinking of?

Could you expand on this — there is something here that I am clearly missing. I thought both of those ("begin boosting frequency based on length of room" & "boundary gain") were essentially the same thing, with the boost being greater when in a corner. And I thought it applied equally to sealed and ported subs.

 

[ryanosaur]

Could you expand on this — there is something here that I am clearly missing. I thought both of those ("begin boosting frequency based on length of room" & "boundary gain") were essentially the same thing, with the boost being greater when in a corner. And I thought it applied equally to sealed and ported subs.

I could but I'd be pretending much beyond the very basic understanding I think I have.
What I can say (perhaps even safely) is that boundary reinforcement (gain) happens anywhere and is not frequency dependent. You can experience it in your own home, a park, a stadium...
Cabin or Pressure Vessel Gain is trickier. I agree with some of what you said to the extent that my understanding here is only rudimentary. But I do think Ported Speakers and Subs will benefit from some aspect of this... but to what extent?
While I lean toward the school that doesn't like using the phrase "pressurize" when describing Subwoofers and how they behave throughout their output, there is an element of this that can also not be escaped. Whatever the mechanism, as the Soundwave cannot fully propagate in the room, its reverberation(?) begins to compound the output SPL.
With a Sealed Cabinet, the rolloff is more shallow than Ported and perhaps this is why it is more noticeable on Sealed Cabinets.
*shrugs
Please understand, this is me trying to work this out a bit. Any guidance or knowledge from the more experienced friends is absolutely welcome!

Regardless, the key difference is in the relation to the room dimensions and the propagation of the soundwave rather than simply how many boundaries are next to the output source.

 

[Dal1as]

Have you tried this test:

The Subwoofer Kick Drum Test

Give your subwoofer a kick (or two... or six).

www.audiocheck.net

If I understand correctly then if all those test tunes play at same level with the chosen volume then you have enough SPL available.

Cool test just remember it is perceived loudness not matched spl. With a correct bass curve lower frequencies will be at higher spl.

As for the sub crawl. My subs are too big so I found studying model mapping of a room to be beneficial and I got lucky with subs placed in front corner, 1/4 left side placement, 2/3 right side placement. This gave me even coverage through most of the room.

 

[dshreter]

What I can say (perhaps even safely) is that boundary reinforcement (gain) happens anywhere and is not frequency dependent.

It absolutely is frequency dependent in the real world. High frequencies are more directional while low frequencies are reinforced more strongly by front and side walls especially. High frequencies are also more easily absorbed.

So boundary reinforcement does impact bass the most.

 

[Dal1as]

It absolutely is frequency dependent in the real world. High frequencies are more directional while low frequencies are reinforced more strongly by front and side walls especially. High frequencies are also more easily absorbed.

So boundary reinforcement does impact bass the most.

To be fair. Horns and waveguides are a form of boundary reinforcement. Not to mention the directivity of the speaker and closeness to boundaries matters at high frequencies. But we are talking subwoofers.

 

[bluefuzz]

I just figure they're of the music camp that doesn't care to spend for the deeper extension subs as they "don't need it". We need different things.

That is precisely my point. What deeper extension? What different things? A large pipe organ can go down to 16 Hz which is as low as any meaningful sound reproduction need be. There are several threads here of bass heavy music of many genres with content as deep. So whence the different requirements?

Of course there will always be people who will argue they need to reproduce a 3 Hz blue whale call at 120 dB but then we're outside the realms of reason ...

 

[jsilvela]

That is precisely my point. What deeper extension? What different things? A large pipe organ can go down to 16 Hz which is as low as any meaningful sound reproduction need be. There are several threads here of bass heavy music of many genres with content as deep. So whence the different requirements?

Of course there will always be people who will argue they need to reproduce a 3 Hz blue whale call at 120 dB but then we're outside the realms of reason ...

Agreed.
I think that is also down to marketing: the different way subs are marketed for "movie people" or gamers vs. audiophiles.
I've seen comments of the type "in such movie/game, my whole house was shaking. Goosebumps. Awesome!!"
For those people, perhaps there really is a quantitative difference in their goals.
But I cannot agree more with you: faithful reproduction of low frequencies, please, in music AND movies.

 

[Dal1as]

Agreed.
I think that is also down to marketing: the different way subs are marketed for "movie people" or gamers vs. audiophiles.
I've seen comments of the type "in such movie/game, my whole house was shaking. Goosebumps. Awesome!!"
For those people, perhaps there really is a quantitative difference in their goals.
But I cannot agree more with you: faithful reproduction of low frequencies, please, in music AND movies.

What's faithful to you may not be the same for someone else especially among different music genres. Some people like near field. Some people are fine with a lack of sub bass. Myself I can't stand either. After experiencing systems with a large sweet spot and easilly able to handle high spl in the lower octaves anything less is a compromise to me.

Basically if I put on SRV and the system can not sound like a small club down in Austin it's not faithful to me as that is what I want.