Information on the Physics of Bass Reflex Enclosures

[Loren42]

Originally Posted by planet10

Looks more like a start from scratch using the same basic set of drivers.

dave

Not sure, but I thought it was built around the Thor design. I can't find the link where he discusses it, so I may be wrong.

[Frankie Carbone]

Originally Posted by planet10

It is a good project if you want to know about how things go wrong.

Despite Joe being considered a master speaker design and having literaly written the book on testing, he blew the design of the TL and compounded it by making a stupid measuring mistake.

Clarity on Seas Thor Kit

This is a design i would never personally consider, unless it was part of an article to support the thesis of the above thread,

It breaks 2 guidlines that i hold dear: 1/ it puts an XO right where the ear is most sensitive, and 2/ the centre-to-centre distance of the drivers is greater than 1/4 wavelength at the XO point.

It is also a lot of money to spend on a 1st effort.

I'd suggest getting a pair of these: You can learn a lot.

The Madisound Speaker Store (also available with copper cones)

They may well save you of much of the "conventional" wisdom, and even if not, make a 1st class midrange.

dave

Thanks! See, this is invaluable stuff. I was blown away when I found this joint. With respect to the THORs, I guess I fell for the old Appeal to Authority logical fallacy.

D' Appolito designed these so they must be good.

My first thought of this place was: "Holy cow, this is a gold mine!"

As I see it, my being an engineer gives me only the advantage of having a head start on the general physics. It's the experience and how to apply those tools that I lack, and hopefully I can get the "how to" from reading the members thoughts here and the experience from just plain trying.

Edison was once asked how frustrating it felt to attempt to invent the incandescent light a 1000 times and fail.

His answer was: "I didn't fail! I found a thousand ways on how NOT to design an incandescent light".

Maybe with a little help I won't have to attempt this a thousand times.

[Frankie Carbone]

Originally Posted by sreten

Hi,

The "theory" of small signal TS parameters bass analysis is well known and
built into many simulation programs, e.g. Basta! goes into the the details :
Basta! technical documentation

Large signal analysis is a completely different kettle of fish and Home is
probably the best resource available to learn about the ins and outs of this.

FWIW designing the bass end of speakers hardly ever involves
the use of anechoic chambers, they are inaccurate in the bass.

rgds, sreten.

If the problem between small and large signal analysis is analogous to the use of S-parameters in large signal RF amplifier design then I am assuming that you are implying that the TS parameters provide for an accurate estimate of small signal operation but fall apart at large signal due to the inherent non-linearities associated with large signal systems? Is that a correct inference?

In other words, is it safe to view TS parameters as small signal only? In RF design, we use something called S-parameters to measure the behavior of large signal amplifiers.

They really don't work too well at high power (because they assume a linear system) but they are used as the ideal starting point and then we deviate from there at large signal and start identifying and characterizing the non linear aspects of the model. The approach basically makes it easier to get a handle on a complex, non-linear system.

[planet10]

Originally Posted by Frankie Carbone

In other words, is it safe to view TS parameters as small signal only?

Sort of. But if you look around you'll see lots of "i measured the parameters of the drivers and they are way differerent than the specs. manufacturers put out garbage data". Part of that could be unit-to-unit variation (which with quality kit can be +/-10% but often reachs much much higher), but most of the time it is that they are measuring on a different part of the curves.

Even a change of the weather can cause significant changes in T/S numbers.

It is likely more the case that if your measures are close to the factories, your drivers have closer to horizontal curves.

dave

[sreten]

Originally Posted by Frankie Carbone

I am assuming that you are implying that the TS parameters provide for
an accurate estimate of small signal operation but fall apart at large signal
due to the inherent non-linearities associated with large signal systems?
Is that a correct inference?

Yes

In other words, is it safe to view TS parameters as small signal only?

Yes/No, what does your question mean ?
Of course its safe, that doesn't mean its right.
Define what is small signal and what is large ....
What is safe ? and what isn't ....

In RF design, we use something called S-parameters
to measure the behavior of large signal amplifiers.

It doesn't seem relevant at all to me, as your slinging about terms that
might seem clever to you but have nothing to do with speaker design.

Hi,

I doubt you'll learn sod all about real speaker design airing your opinions
here, you certainly won't learn much in this thread, given that nearly all
information given in threads is contradictory, or is sadly more consistent
marketing speak that really doesn't tell you anything useful or rigourous.

rgds, sreten.

[planet10]

Originally Posted by sreten

It doesn't seem relevant at all to me, as your slinging about terms that
might seem clever to you but have nothing to do with speaker design.

I have seen S used in transfer functions... whether it is the same S, i do't know.

dave

[Pano]

Originally Posted by Frankie Carbone

The Boynton Beach facility closed years ago. 2,000 or so, especially after the selloff of our mobile phone division to Google.

Boyton, sorry - I should have remembered. I used to live there, ages ago.
George is a cool guy, but mostly does amps (at least in public). You can find him here: Tubelab - diyAudio

[planet10]

Originally Posted by sreten

I doubt you'll learn sod all about real speaker design airing your opinions
here, you certainly won't learn much in this thread, given that nearly all
information given in threads is contradictory, or is sadly more consistent
marketing speak that really doesn't tell you anything useful or rigourous.

There goes sreten the pessimist. He thinks some of the stuff i do can't possibly work, and that opinion based on no experience.

You will find lots of opinions, different approaches, differing experiences. And some people, who if the opion, approach, or experience does not align with theirs it has to be wrong (check out the ongoing active vrs passive thread)

So you need to read, sift, make judgements, but most important you need to get your feet wet, to establish a personal experiential reference, and figure out what makes the most sense for you, your room, your kit, your tastes, and your budget.

dave

[Frankie Carbone]

Originally Posted by sreten

Hi,

I doubt you'll learn sod all about real speaker design airing your opinions
here, you certainly won't learn much in this thread, given that nearly all
information given in threads is contradictory, or is sadly more consistent
marketing speak that really doesn't tell you anything useful or rigourous.

rgds, sreten.

I disagree. I have already downloaded a few papers that folks here posted for me, as well as ordered two books to help get me started.

[Keriwena]

Originally Posted by Frankie Carbone

They really don't work too well at high power (because they assume a linear system) but they are used as the ideal starting point and then we deviate from there at large signal and start identifying and characterizing the non linear aspects of the model. The approach basically makes it easier to get a handle on a complex, non-linear system.

Yep, you got the idea.

Hifi speakers are assumed to be linear, but in the real world, as they reach their limits they go off track. Then there are guitar speakers and some pro audio speakers, which are designed to be non-linear. They deliberately compress as they are driven louder, which provides better performance in a "live" venue, given the way our ears work. Nor are cabinets linear, once you get beyond mini-monitors driven to merely polite volumes. We also can't get away from our listening rooms, and "linear" means something very different to a carpenter.

The Klippel site sreten mentioned earlier is the current state-of-the-art for chasing down false assumptions. But, hey, we had to simplify things to see the basic pattern before complexicating it with all the stuff that really matters. In the '50s, we were so lost....