Why are sealed box woofers out of fashion

[mark100]

@mark100, if you are talking about doing outdoor ground plane measurements of subs, then I agree with you. It is the best way to measure the frequency response of a sub.

Yes, that is by far the best sub measurement technique i know of,
unless maybe you have a big crane to hoist sub and mic up into the sky Lol

 

[mark100]

It's always interesting and remarkable to first read a very strong general statement, but the more we ask about things, the more and more specific it becomes.

I don't understand the strawman here, I think it's quite evident how coupling principles work.
Yes, to some extend that depends a bit on the type of wall obviously, but without any walls we know for sure there is zero coupling.

Honestly, all the sub room coupling possibilities, all the permutations, all the room construction details, are just a big cop-out....
when it comes to evaluating subs......or even speakers in general for that matter....imo.

Sure. rooms overlay their own sonic signature....any sub will respond to 1/4 space wall loading, or 1/8 space corner loading. Or create virtual subs with interior barrier reflections......big whoop.

I believe the vagaries in all those possibilities is why we must see thru rooms responses, to make meaningful sub (or speaker) comparisons/evaluations.

I mean heck, why are speaker measurements overwhelmingly anechoic?

 

[mark100]

I'm constantly coming across statements that the Linkwitz Transform for sealed enclosures is a good option because the energy levels in the lower registers of music recordings are lower, giving you headroom to apply the correction.

I believe this is completely wrong. I analyzed a track I was listening to at the time (Tape Five - Grand Central - Slow Motion) with an FFT analyzer and found the following:
The 25-100 Hz range had the highest levels for this particular recording. Even the 10-20 Hz range showed some very low-frequency rumble. If I deliberately select something electronic, the low-frequency register can be even higher in level and lower in frequency.

View attachment 1314666

Therefore, you need to pump a lot of watts to get those lower frequencies below Fb. For example, you might need over 50 watts for a 90 dB/W woofer to reach 96 dB SPL below Fb, and you'll reach Xmax very quickly. There is no headroom in the recording. If you operate your woofer close to Xmax, you'll negatively affect the rest of the reproduced range, as motor (force factor BL) and suspension nonlinearities are real and more noticeable than your typical harmonic distortion.

Yep, must agree. What you say reflects my experiences too...

 

[wchang]

Agree with most all of this, and about economics dominating, too.

What prevents me from doing the "double up on sealed" in the same size box though, is I've come to really prefer the sub cones face me.
I think they provide a better 'transient wave vector' or something, for lack of good terminology. I simply can't agree with the subs are omni line of thought, when it comes to bass transients.

So force cancellation doesn't work, as it doesn't let two drivers face me.
And getting two drivers to face me, makes the box get even bigger than a single driver ported.
For me and what I like, I see the economics as much about size, as cost.

You can use 45deg bouncers on the driver-pair or slot-load them. But I see this thread has become one for the beer lounge.

 

[diyuser2010]

It's your time to prove it.

Everyone here (with practical experience) tells that it is not airsealed enough for slow pressure changes. Everything you tell us is "I disagree" without any backing up. Now is your chance!

These boxes are air sealed enough for a perfect operation of a speaker, that's no question. But not enough for these lousy little atoms to not sneak in.

I don't have to prove anything to strawmen. Next you will say that balloons aren't sealed because ~ helium....

Look, squirrel!

You seem to insinuate that I do not have practical experience.

 

[Arthur Jackson]

Sheesh, you think wasps are bad, This little monster loved to make port entry at warp speed when she still fit.

Kitties are aperiodic damping.

 

[Juhazi]

In general vs. specific extreme exceptions...

---
Actuoally the topic of this thread is oxymoron, so polemic, even poetic "discussion" is what we get.

 

[nc535]

I'll bet we all can agree that side woofers are even less convincing than slot loaded woofers with the slot facing forward. "convincing" is the key word but the argument is aural as well as visual.

Sure, outdoors is the best place to measure subs but what matters is how they are placed and how they sound in the room. the room effects cloud the characterization of the sub when the characterization is done in room, but the room effects are what must be mitigated for one to best enjoy music.

 

[b_force]

I mean heck, why are speaker measurements overwhelmingly anechoic?

Because

• we need some reference to compare against
• it's impossible to figure out what the room exactly is doing*
• what directivity/power response/in room response is needed to combine the two
• it's the least bad approach we have.

*That being said, this is also why one should put time and effort in getting the room acoustics right. Instead of spending all that money in "better" drivers.
Because when that is done well, anechoic measurements correlate directly to the in-room performance

 

[b_force]

Yes, but indoor conditions can vary quite a bit too. Different reom constructions can be extremely sensitive to positioning. This was discussed in some detail at one time in another thread. Some speaker positioning techniques require moving speakers in half-inch steps. The question came up as to whether or not the claim was absurd. Turns out it depends on lot on floor construction and where speakers are located relative to support beams. It was found that half an inch could make a real difference in some cases.

Obviously, I don't follow your point?

But if you understand the principles behind dipole and cardioid systems, you should know that they loose all their value outdoors if the goal is to get an impression for indoor use.

At that point it's even beyond comparing apples with pears.

Btw, the claim that started this was listening to a specific subwoofer system to get a certain judgement for its performance.

Not measuring a subwoofer system.

 

[b_force]

I don't have to prove anything to strawmen. Next you will say that balloons aren't sealed because ~ helium....

Look, squirrel!

You seem to insinuate that I do not have practical experience.

Can we just stick to the technical subject and respond like mature men instead of throwing poop at each other?

We are not twelve anymore.

Don't understand all the emotion, we are just talking about the technicality around loudspeaker systems.

Emotions don't belong in that discussion.

 

[Lojzek]

Would a driver with specs:
Fs 80Hz
Qms 4.5
Qes 1.3
Qts 1.2
Vas 6.8 cubic foot
Spl 87db
(6 1/2 inch driver)
be any good in a sealed box, or terrible?
The fs of 80 seems too high to me, but I know little of such things.

Vas is likely a typo. It is a question of how much do you want it controlled and this means experimenting
with the sound you may get from this unit. There is no rule preventing you to use a drive unit in any conceivable
cabinet and loading type. In order to not overemphasize the spl around Fs, a worthy goal would be to increase the
mechanical damping (reduce Qmc) to practically as low as possible to counteract relatively high Qes, resulting in an
acceptable Qtc. This makes sense for as long as you plan to employ the unit down to its Fc, otherwise not (like high passed
somewhere high).

 

[Markw4]

...dipole and cardioid systems, you should know that they loose all their value outdoors if the goal is to get an impression for indoor use.

True.

 

[ctrlx]

I'm constantly coming across statements that the Linkwitz Transform for sealed enclosures is a good option because

if i use an ltx to move F3 from 50Hz to 25Hz, that equates to 3dB more output at 50Hz
your telling me that you cannot turn your bass knob up 3dB without destroying your amps and speakers?

 

[phase_accurate]

Just keep in mind that by doing this you now also increase the power at 25 Hz 16 fold and the excursion fourfold. Whether this is fine or not can't be generally decided and depends a lot on the program material, the speakers used and your expectations.

 

[Hörnli]

A speaker is never minimum phase.

Yes they are.

Or are you now gonna tell us that all these equivalent lumped circuits and fundamental rock solid theory behind is is all BS?

In that case I wonder why you're spending time on a forum and not write an AES paper?
Which must also result in a Nobel price, since it means that fundamental physics has to be rewritten.

Can we just stick to the technical subject and respond like mature men instead of throwing poop at each other?

No?

 

[phase_accurate]

It heavily depends on how you define "speaker".
If you are talking of bare drivers: Yes they are definitely minimum phase.
If you are talking of multiway speakers with allpass crossovers (like LR for instance): No they are definitely not minimum phase.
If you are talking of multiway speakers with transient perfect crossovers: Yes, they are also minimum phase.

Regards

Charles

 

[Hörnli]

If you are talking of bare drivers: Yes they are definitely minimum phase.

Is Barkhausen noise minimum phase?
https://en.wikipedia.org/wiki/Barkhausen_effect
https://de.wikipedia.org/wiki/Magnetischer_Barkhausen-Effekt

Best regards
Bernd

 

[hifijim]

@hornli, I understand what you are getting at... Real loudspeaker drivers produce various noises, distortions, and exhibit other non-linearities. For example, real drivers produce modulation distortion, and I doubt that an idealized analog filter with the same magnitude and phase response as that driver could be made to produce the same modulation distortion.

But please try to understand the point of engineering. In order to understand and design circuits, mechanisms, and processes, they are idealized so they can be modelled and explained mathematically. If we insisted that before a model or simulation could be useful, it had to explain or predict every response of a device, under every circumstance, then we would have very slow scientific and technological advancement.

So it is with loudspeaker drivers. They are assumed to be minimum phase devices. As long as they are operated in their linear range, they are close enough to minimum phase that we can make that assumption, and design high performance speaker systems. Yes, they do deviate from the minimum phase ideal, but not to the extent that it matters for design and analysis.

j.

 

[Tenson]

This thread has a great deal of positive sharing of knowledge. Let us not be distracted from the goal of helping each other arrive at a place of greater understanding. Being wrong or mistaken is not a shame, it is a badge of pride that we are growing We only need to accept it that way ourselves.