What is the Reason For This Driver Design (Large Dust Cap)

[thewas]

TSP parameter based design gives a good basis for a relatively flat response which is a good thing as high magnitude or slope filters can introduce several problems like high driver excursion, high group delay and even ringing. Of course if enclosure size is limited a lot be can gained with such extreme filters as it can be observed with many modern compact BT loudspeakers which make surprising bass (and we know from the studies of Toole that bass can be 30% in the rating of a loudspeaker) but their previously mentioned limitations also can be audible when analytically listened.

 

[Heinrich]

TSP parameter based design gives a good basis for a relatively flat response which is a good thing as high magnitude or slope filters can introduce several problems like high driver excursion, high group delay and even ringing. Of course if enclosure size is limited a lot be can gained with such extreme filters as it can be observed with many modern compact BT loudspeakers which make surprising bass (and we know from the studies of Toole that bass can be 30% in the rating of a loudspeaker) but their previously mentioned limitations also can be audible when analytically listened.

For sake of science, or better to say, as Sir Karl Popper understood it, see:

GRIMM Audio LS1c & SB1 DSP Speaker Review

This is a review, listening tests and detailed measurements of the GRIMM Audio LS1c active DSP speaker and its companion SB1 subwoofer. It was sent to me by the company. Speakers cost US $26,500 in the tested finish (pair). Companion SB1 sub costs US $12,750 for the set, brining the total to...

www.audiosciencereview.com

The subwoofer of that assembly is proving the above and elsewhere formulated 'rule' wrong. The DIY scene has to acknowledge that there was a shift in paradigm. Even Siegfried Linkwitz, the DIY's ol' buddy suggested his Linkwitz transform aka biquad in the 1970s(?). Now you say, huh, not that extreme please. But what is extreme, actually?

In actuality the extreme is where desirable properties are sacrificed for no good reason. The weighing of different properties can be done using the T/S parameters, subsequently performing calculations of expectable diphragm movement, power consumption and all. But it is *not* that the T/S parameters define a reasonable design (aka 'Butterworth, Q=0,7, etc), but the designer does, taking the results of T/S parameter based calculations into critical account.

In short, there is a subtle difference in saying, T/S parameters 'give a good basis' - which is an utterly erroneous take, and saying, T/S parameters allow me to predict properties and I freely pick the ones I need. The calculatory tool of T/S parameters is not a design schema, even if in rancid old books for newbies such is suggested.

Not to say, that the T/S parameters do, explicitely, *not* take into account anything of relevance regarding the actual limitations of a design: excursion limits, gradually approached with more or less distortion, power consumption and dissipation, the human hearing (sic!) and what have you. Hence is is less wise to argue in favour of T/S standard alignments by stating limitations ...

 

[teashea]

The Thiele/Small parameters describe the speaker and enclosure combined as a filter. In this theory the whole doesn't have mechanical or other limitations. Instead, it just follows the math, theoretically.

Filters of whatever design can be concatenated with other filters. The sequence and mutual association doesn't matter. That is what contemporary drivers (in p/a and studio) are made for since the 1990s. The need to be supported by electronic/digital, additional filters. E/g a subsonic filter to prevent overexcursion below the bassreflex tuning, and to combine this with a bit of a peaking just a above the cut-off, which is ironed-out by the subsonic, in total having the very exact, best extension down low.

One might argue that extreme designs hit the limitations earlier, e/g too much power needed to drive the enclosure, but that is decidedly not (no, no) something originating in the T/S parameters. The latter only allow to calculate, theoretically, the filter's properties, any filter! What people do is to mess up the means to describe something, with what is described.

One might argue (properly) that the results are what count. Neumann KH150's, for example, set a new standard for accurate reproduction.

 

[mhardy6647]

Big woofer.
Big voice coil.
Big dust cap.

 

[teashea]

Big woofer.
Big voice coil.
Big dust cap.

It is the results that count.

 

[mhardy6647]

It is the results that count.

absolutely.
The 515B... counts.

 

[thewas]

For sake of science, or better to say, as Sir Karl Popper understood it, see:

GRIMM Audio LS1c & SB1 DSP Speaker Review

This is a review, listening tests and detailed measurements of the GRIMM Audio LS1c active DSP speaker and its companion SB1 subwoofer. It was sent to me by the company. Speakers cost US $26,500 in the tested finish (pair). Companion SB1 sub costs US $12,750 for the set, brining the total to...

www.audiosciencereview.com

The subwoofer of that assembly is proving the above and elsewhere formulated 'rule' wrong. The DIY scene has to acknowledge that there was a shift in paradigm. Even Siegfried Linkwitz, the DIY's ol' buddy suggested his Linkwitz transform aka biquad in the 1970s(?). Now you say, huh, not that extreme please. But what is extreme, actually?

In actuality the extreme is where desirable properties are sacrificed for no good reason. The weighing of different properties can be done using the T/S parameters, subsequently performing calculations of expectable diphragm movement, power consumption and all. But it is *not* that the T/S parameters define a reasonable design (aka 'Butterworth, Q=0,7, etc), but the designer does, taking the results of T/S parameter based calculations into critical account.

In short, there is a subtle difference in saying, T/S parameters 'give a good basis' - which is an utterly erroneous take, and saying, T/S parameters allow me to predict properties and I freely pick the ones I need. The calculatory tool of T/S parameters is not a design schema, even if in rancid old books for newbies such is suggested.

Not to say, that the T/S parameters do, explicitely, *not* take into account anything of relevance regarding the actual limitations of a design: excursion limits, gradually approached with more or less distortion, power consumption and dissipation, the human hearing (sic!) and what have you. Hence is is less wise to argue in favour of T/S standard alignments by stating limitations ...

It seems you clearly misunderstood and misinterpreted my post, what I meant is a reasonable tuning of the bass which can be done via T/S parameters or simulation etc so the woofer response doesn't need extreme equalisation due to the problems connected with it that I wrote.
Since you mention the LS1c, do you have a simulation for its woofer enclosure since you state its far off such?
And I would recommend doing yourself a favour, don't use the term "science" so often for trivial engineering stuff, this doesn't make anyone being superior.

 

[Heinrich]

... yourself a favour, don't use the term "science" so often for trivial engineering stuff, this doesn't make anyone being superior.

Exactly, but sometimes it is science, that comes with a different attitude: doubt, not assurance.

On the secondary topic of "how important is a big motor, if it is indicated by the size of the dust cap" (really, that was a question), can't see how I could argue otherwise. Seems the topic needs more time to settle.

 

[MAB]

Exactly, but sometimes it is science, that comes with a different attitude: doubt, not assurance.

Naw, you just misinterpreted.

 

[Heinrich]

Naw, you just misinterpreted.

I'm not an engineer, actually. But I can imagine, how strong the rules are regrading standards and so forth. That tight suit may suggest that "we" know, but science, as far as I know that little mouse remotely, won't ever confirm.

I think my strongest argument is, that the T/S parameters don't acknowledge limitations (e/g, again in power consumption and digestion, Xmax ...), so you cannot argue in favour of sticking to, presumably, inherently T/S prescribed designs, with that limitations. It's, with all due respect, an unreasonable argument, no connection. As I said, maybe the topic needs more time to sink in, the ocean of our ancesters wisdom is that deep.

 

[MAB]

I'm not an engineer, actually. But I can imagine, how strong the rules are regrading standards and so forth. That tight suit may suggest that "we" know, but science, as far as I know that little mouse remotely, won't ever confirm.

I think my strongest argument is, that the T/S parameters don't acknowledge limitations (e/g, again in power consumption and digestion, Xmax ...), so you cannot argue in favour of sticking to, presumably, inherently T/S prescribed designs, with that limitations. It's, with all due respect, an unreasonable argument, no connection. As I said, maybe the topic needs more time to sink in, the ocean of our ancesters wisdom is that deep.

Do you have large signal measurements to share?
Otherwise, why so many words and no info? It's hard to follow so much speculation and long winded verbiage. Also, nobody was arguing in favor of small vs. large parameters until you turned it into an argument.

Would be nice to see exactly what point you are trying to make. Are you here just to argue in circles, put arguments into people's mouths and run with it? Or will you share some of this knowledge that you are alleging?

 

[Heinrich]

Do you have large signal measurements to share?
Otherwise, why so many words and no info? It's hard to follow so much speculation and long winded verbiage. Also, nobody was arguing in favor of small vs. large parameters until you turned it into an argument.

Would be nice to see exactly what point you are trying to make. Are you here just to argue in circles, put arguments into people's mouths and run with it? Or will you share some of this knowledge that you are alleging?

Hi @MAB, no bad feelings. You got 'likes', that's fine ;-)

Yes, I do measurements, but not to prove my "claims". I prove my concept(s) with measurements. They are not made to be presentable to third parties. I only give hints for - DIY. In case people don't pick it up, fair enough.

In this case I wonder about the argument. People say: "There is some kind of a proven basic design guideline. It is described by the T/S parameters. In case one departs from those guideline too far, that will give undesirable results."

Do I get it right? In case, the argument is not connected to large signal behavior, because the T/S parameters do not consider mechanical or electrical limits, e/g xmax/distortion, power consumption/digestion.

Only to give an example for my ways of thinking: human hearing is limited as described by the Fletcher/Munson curves. It doesn't make sense to reproduce low frequency content, that cannot be heard. It cannot be heard, if the available SPL at a given frequency doesn't push it above the frequency dependend threshold of hearing. Clearly, such isn't reflected in the T/S parameters, but could be considered when designing a bass alignment. I'm not too much enclined to follow down this (off?) topic further.

 

[thewas]

I am not MAB but I have to reply here.

Yes, I do measurements, but not to prove my "claims". I prove my concept(s) with measurements. They are not made to be presentable to third parties. I only give hints for - DIY. In case people don't pick it up, fair enough.

We peasants thank you Prophet

In this case I wonder about the argument. People say: "There is some kind of a proven basic design guideline. It is described by the T/S parameters. In case one departs from those guideline too far, that will give undesirable results."

Do I get it right? In case, the argument is not connected to large signal behavior, because the T/S parameters do not consider mechanical or electrical limits, e/g xmax/distortion, power consumption/digestion.

You still seem to ignore that with T/S compatible tuning is meant that the response of the bass driver gives a relatively close desired response in the enclosure without the need of excessive equalisation, that has nothing to do with the small vs large signal properties of T/S.

Let me ask you one simple question, do you agree that just slapping a bass driver in box and using high amplitude EQ to correct can have significant disadvantages when high SPL and/or high fidelity is desired?

 

[Heinrich]

We peasants thank you Prophet


You still seem to ignore that with T/S compatible tuning is meant that the response of the bass driver gives a relatively close desired response in the enclosure without the need of excessive equalisation, ...

Tl;Dr - think we had enough of an argument about undefined terms as "excessive". You know, your argumentation relies on that term, you only use it so, but still you do not define what it should mean, leaving it to the reader to imagine something.

I leave this discussion with a slightly bitter taste because of sarcasm. Not bad, but ..

 

[Penelinfi]

So is it a rule that bigger dust caps mean bigger voice coil? And are bigger voice coils always advantageous?

Not necessarily. Some cones have no dust cap or it's inverted and can hide the size.

You can also have large dust cap with "normal" voice coil :

Such designs are usually some form of strengthening for the cone, or just looks.

However it can be more of an occurrence that big coil = big dust cap

 

[thewas]

Tl;Dr - think we had enough of an argument about undefined terms as "excessive". You know, your argumentation relies on that term, you only use it so, but still you do not define what it should mean, leaving it to the reader to imagine something.

Boundaries are not sharp of course, but experience shows that for example positive filters over approximately 5 dB and Q higher than 1.4 can be problematic.

 

[MAB]

In this case I wonder about the argument. People say: "There is some kind of a proven basic design guideline. It is described by the T/S parameters. In case one departs from those guideline too far, that will give undesirable results."

Do I get it right?

No, you didn't get it right. Your arguments are unserious. And are just that, arguments.

In case, the argument is not connected to large signal behavior, because the T/S parameters do not consider mechanical or electrical limits, e/g xmax/distortion, power consumption/digestion.

You went in a 360 degree circle in one sentence. Like I said, completely unserious nonsense.

 

[Heinrich]

No, you didn't get it right. Your arguments are unserious. And are just that, arguments.

You went in a 360 degree circle in one sentence. Like I said, completely unserious nonsense.

As I said, please, I'm not into this anymore. Especially as it belongs, clearly, to DIY, which is covered on another board.