The truth about subwoofers

[peterp1]

After passing through the second amplifier the theory falls completely apart, the sub driver is seeing a completely different signal.

It doesn't fall apart at all. You can only consider the variables you have control over. You can't avoid the sub amp -- it exists regardless -- the only thing you have control over is deciding the best way to drive the sub. You can't avoid the stereo amp -- it exists for the mains and colors the mains regardless. The most coherent signal to the sub amp will be the exact same one that is driving the mains. Whether that coherency makes a difference, versus less coherent line-level, can be argued (and will be dependent on equipment), but you can't just dismiss the (at least theoretical) advantage of that coherency.

The only thing this accomplishes is adding even more circuitry into the signal path, and THAT'S always a good thing eh?

Why is it a bad thing? What difference does adding 0.05% or 0.1% make for a subwoofer? You are ignoring the coherency advantage (at least theoretical) of driving the sub amp with the same signal as the mains.

The high level inputs are there for those that have lower tier equipment that have no other option, if that insults anyone it wasn't intentional. Not everyone finds it important to invest in separates, or upper tier receivers etc that offer pre outs, and that's fine. But that shouldn't exclude their using a subwoofer, or retailers offering an option so they can by including high level inputs. I'm sure their sales would be severely hurt if this option wasn't included, shrewd business move.

It's a false assumption that only-low end subs have speaker-level inputs. It's a false assumption that only low-end equipment doesn't have preamp outs -- most tube amps don't have preamp outputs. It's a false assumption that everyone wants preamp outs.

As for subwoofer distortion, have you looked at the astonishingly low distortion numbers generated by quality servo subs? Not all subs are created equal. I'll see if I can locate the specs for my sub, purchased more than a dozen moves ago and things get lost.

No matter how low the distortion, 0.1% or 0.05% isn't going to make a difference.

 

[musichal]

After constantly reading posts that claim sealed subs are better than ported, "fast" (no such thing) subs are better and the absolute drivel that using high level inputs is better when using a subwoofer, I felt I should post that link.

FWIW: AFAIK there is only one subwoofer manufacturer that advocates high level inputs. Their subs have only high level inputs.

When someone calls a woofer "fast" I understand that to mean highly compliant. I'm not sure how much that matters in a subwoofer down at the lower frequencies, though. A lightweight rigid cone has always been the goal in design - stops and starts more responsively than a heavier cone in the same basket. In other words, is more compliant. Like I said, that is my understanding, but I'm a fallible human using my own defective logic, and will gladly read what you guys think to see if you persuade me to rethink the issue, because that well may not be correct.

Meant to mention somewhere in this that my understanding is that sealed-box woofers have highly compliant drivers. [Later Edit}.

I did agree with most of what was written in the link.

 

[F1nut]

After passing through the second amplifier the theory falls completely apart, the sub driver is seeing a completely different signal. The only thing this accomplishes is adding even more circuitry into the signal path, and THAT'S always a good thing eh?

Based on your logic the line level and high level connections shouldn't be any different since as you put it, "the sub driver is seeing a completely different signal." Yet you stated you think the line level sounds better. Hmmmm!

The high level inputs are there for those that have lower tier equipment that have no other option, if that insults anyone it wasn't intentional. Not everyone finds it important to invest in separates, or upper tier receivers etc that offer pre outs, and that's fine. But that shouldn't exclude their using a subwoofer, or retailers offering an option so they can by including high level inputs. I'm sure their sales would be severely hurt if this option wasn't included, shrewd business move.

So, the only reason my two subs at $3300.00 each have high level connections is so I can use a $500.00 stereo receiver? Well gee, I guess wasted a lot of money on the rest of my gear.

 

[halkaloogie]

Read through the whole post so far and so far it has been one of the more interesting reads in a while, unfortunately filled with very few facts, but lots of emotion.

 

[rothwellaudio]

When someone calls a woofer "fast" I understand that to mean highly compliant.

When someone calls any kind of bass "fast" I wonder what they're talking about. Tweeters move fast - up to 20,000 times per second. Bass drivers move slowly, as low (or lower) than 20 times per second.
But maybe they're talking about the impulse response of the bass driver. Yes, after an impulse some bass drivers (and ports) continue to emit sound before settling back down to rest longer than others do. Sealed cabinets stop quicker than ported ones as far as I'm aware.

 

[halkaloogie]

Sealed cabinets stop quicker than ported ones as far as I'm aware.

I tend to like your point of view on a lot of things concerning audio, and was pretty happy to just let this argument run itself out, but I'm not so sure about this statement. What information are you taking from to form this opinion.

 

[rothwellaudio]

What information are you taking from to form this opinion.

The loudspeaker analysis software which people use to design cabinets using T/S parameters is usually capable of plotting the step response of the system. Try this page:
http://www.micka.de/en/index.php#ideal
Sorry, I can't take a screen shot and paste it here, but just put in a few parameters and let it do a plot. You don't have to put in all the parameters.
Try Fs = 40 Hz, Vas = 40L and Qts = 0.3. You don't have to enter anything else. Let it do the plots and look at the step response. You'll see three sine waves that quickly die down to zero. However, the closed box sine wave dies down the quickest. You can use parameters for "your own box" to look at oversized enclosures and odd tunings for the port to see how it's possible to get a big boost in bass but the step response takes much longer to settle down.
Btw, if I've misinterpreted the data or misunderstood something I'm happy to be corrected.

 

[Hobie1dog]

When someone calls a woofer "fast" I understand that to mean highly compliant. I'm not sure how much that matters in a subwoofer down at the lower frequencies, though. A lightweight rigid cone has always been the goal in design - stops and starts more responsively than a heavier cone in the same basket. In other words, is more compliant. [Later Edit}.

the definitive article on "woofer speed" by one of the worlds most accomplished speaker designers,

https://adireaudio.com/wp-content/uploads/2018/12/Adire-Audio-Woofer-Speed-by-Dan-Wiggins.pdf

 

[spark1]

Read through the whole post so far and so far it has been one of the more interesting reads in a while, unfortunately filled with very few facts, but lots of emotion.

I've seen a lot of snark, but also quite a bit of thoughtful, logical commentary.

It seems that one member is offended by the notion that a subwoofer using speaker-level connections can sound as good as one using line level connections.

Otherwise, a good discussion.

 

[onwardjames]

Good article. It uses logic and data to make its points. Thanks for sharing, I learned much today.

Now to get out there and fix my Miller and Kreisel sub, which apparently has a bad pot that De-Oxit won't fix.

 

[Grenadeslio]

Based on your logic the line level and high level connections shouldn't be any different since as you put it, "the sub driver is seeing a completely different signal." Yet you stated you think the line level sounds better. Hmmmm!



So, the only reason my two subs at $3300.00 each have high level connections is so I can use a $500.00 stereo receiver? Well gee, I guess wasted a lot of money on the rest of my gear.

Well just maybe it's so someone with a $500 receiver "can" use your sub eh? Makes good economic sense not to exclude buyers doesn't it? Never thought I would have to be an economics teacher on a music forum.

You people that think there's some kind of extra coherency by running the signal through a second amplifier need to get passive subs, then and only then will the sub see the "SAME" signal.

 

[Grenadeslio]

I've seen a lot of snark, but also quite a bit of thoughtful, logical commentary.

It seems that one member is offended by the notion that a subwoofer using speaker-level connections can sound as good as one using line level connections.

Otherwise, a good discussion.

Well i believe its more a couple of members grasping at straws attempting to hold onto a silly notion that somehow inserting a second amplifier into the chain is a good thing lol. Now that's about the funniest thing I've read here at AK. Otherwise some members here have good points.

I guess all the minimalist electronic designers have their collective heads up their asses as it seems it's a useless endeavor eh? What a joke.

If having the same signal is so important then get a passive sub, it's the "only way" to achieve this, otherwise you're just spouting drivel.

 

[Grenadeslio]

Good article. It uses logic and data to make its points. Thanks for sharing, I learned much today.

Now to get out there and fix my Miller and Kreisel sub, which apparently has a bad pot that De-Oxit won't fix.

"Logic" and data, we sure could use a dose of that around here eh? Logic just seems to fly out the window here at times, like thinking adding more unnecessary electronics into the signal path is a good thing lol.

Hell, many members here eschew the use of tone controls, manufacturers include the means to defeat many of the controls, even my DVD players include methods to turn off sections for this reason.

Here we have members so entrenched in their illogic that they're willing to argue that adding "all the circuitry in a SECOND amplifier" into the signal path is a good thing ROFLMAO.

Again, we could use some logic around here.

 

[spark1]

Well i believe its more a couple of members grasping at straws attempting to hold onto a silly notion that somehow inserting a second amplifier into the chain is a good thing lol. Now that's about the funniest thing I've read here at AK. Otherwise some members here have good points.

I guess all the minimalist electronic designers have their collective heads up their asses as it seems it's a useless endeavor eh? What a joke.

If having the same signal is so important then get a passive sub, it's the "only way" to achieve this, otherwise you're just spouting drivel.

The point made was that the type of connection matters very little, and that logical arguments can be made for either. This fact irritates you. So be it.

I don't know about the location of the designer's heads, but you have clearly demonstrated where yours is.

 

[onwardjames]

Aw, c'mon, everyone. It's Christmas time. Please, let's all play nice, because the fat man is watching, lol.

 

[peterp1]

You people that think there's some kind of extra coherency by running the signal through a second amplifier need to get passive subs, then and only then will the sub see the "SAME" signal.

Your argument makes no sense at all. An active subwoofer is holistically designed as a combined unit (amp and driver) that work together to provide as linear response as possible to match what happens with any mains being driven by any stereo amp. To drive a passive sub (as you suggest) with the stereo amp makes no sense at all -- it will be horribly unbalanced at different volume levels just based upon efficiency differences between the mains and the sub drivers, among many other things, like crossovers, gain, phase, etc.

You have to deal with what equipment exists and what you have control over. You have a stereo amp driving the mains and you have an active sub with an internal amp (not to say that niche passive subs don't exist, but that's not what the article is talking about). The only choice you have is how you drive the subwoofer.

There are plusses and minuses to both approaches, which I have already outlined clearly in at least 2 posts (in the interest of brevity I will not repeat here). I have not said one is better than the other because no such declaration can be made (it is 100% dependent upon the specific equipment involved). You are completely ignoring the "plus" side of speaker-level and are only focused on the theoretical "negative" (and it is theoretical only because the added amp distortion is totally irrelevant given the distortion levels of subs). There is no basis for your argument, which is why you are the only one making it -- you are drastically inflating the harm of the additional amp (that unavoidably exists for the mains anyway) and you are ignoring any coloration and non-linearity of the stereo amp that unavoidably affects the mains (and won't be reflected in the sub if you bypass the stereo amp with line-level). To what degree the stereo amp coloration and non-linearity is present and meaningful can certainly be debated, but not in the abstract as a definitive rule because it is 100% dependent on the equipment used.

Question: If you have a solid state preamp driving a tube power amp, will it sound better to drive the sub with the solid-state line-level signal from the preamp or to drive the sub with the speaker outputs, so that the sub picks up the same tube amp characteristics that are unavoidably reflected in the main speakers? (which the sub's only job is to seamlessly and linearly integrate with)

The definitive answer is -> it depends*


* on the specific equipment used, the type of music listened to (for example, jazz will be different than hiphop) , owner's sound priorities, ...

 

[JoeESP9]

Does anyone know of any higher end sub manufacturer that provides only high level inputs other than REL?

 

[F1nut]

Does anyone know of any higher end sub manufacturer that provides only high level inputs other than REL?

REL provides line level inputs for those that haven't been educated on the superior results of the high level method.

 

[waggs098]

Doesn't this all just really boil down to what a certain person thinks sounds better to their ears?

 

[jazzmans]

Doesn't this all just really boil down to what a certain person thinks sounds better to their ears?

Pretty much.

But there's a ton of useful information for the unknowing in the original article.

Turning this thread into a high is better, you suck; low is better, you suck, is a disservice.