Enclosure Volume

[Ron E]

Beranek and Novak solved the equivalent circuit and made some general theoretical comments.

I believe Thiele was one of the first to apply many "alignments" to the circuit theory (Novak mentions Butterworth) and he established methods for measuring combination parameters useful for design. Neville Thiele and those who follow (Benson, Small, Fincham, Geddes....) provide the information most useful to hobbyists. Vance Dickason in his loudspeaker Cookbook boils it down to a level high school kids can understand, and Weems brings it down to a level that junior high kids can probably manage

Beranek and Olson are useful books to have on the shelf if you are delving deeply into the theory and are at an undergraduate-graduate level of engineering and know complex math and circuit analysis. Benson's book is probably far more valuable as a start because it has an extensive bibliography that lets you know what he is getting from the eaarlier authors. He duplicates their results with his general theory and so proves it useful and comprehensive. Little of this is practical to the hobbyist, unless s/he be quite advanced, which rs_dhar does not seem to be.

[planet10]

Originally posted by Ron E
Beranek and Olson are useful books to have on the shelf if you are delving deeply into the theory and are at an undergraduate-graduate level of engineering and know complex math and circuit analysis.

Olson's book is worth having just to look at the pictures.

The math in these 2 books is somewhat intimidating and i say that having an honours BSc in math (although i have forgotten most of it).

dave

[roddyama]

Beranek and Novak solved the equivalent circuit and made some general theoretical comments.

Beranek, in his section on closed box loudspeakers, solved and graphed the normalized response of a closed box loudspeaker for Qt = 0.1 to 10 in 7 steps for normalized frequencies from 0.1f3 to 10f3. Can you imagine how long that took with a slide-rule back in the early 50's. It boggles the mind.

Rodd Yamas***a

[r_s_dhar]

All Elders and Peers,

Thanks for your remarks. I have actually completed TS tests on my woofers and midranges and shall put the results on this string to ask you whether the figures look acceptable. In the Meanwhile I have problems with the formula to arrive at Vb. Actually there are two different formulae and they give me results varying the volume by almost 1 cubic feet. The first formula is:

Vas = Vb((Fb/Fs)2-1)

found in http://sound.westhost.com/tsp.htm

The second one is:

Fc*Qec
Vas = Vb [ -------- - 1 ]
Fs*Qes

found in http://www.crackinguniversity2000.it...rameters.html.

Phase_Accurate,

I have quite a few freeware programmes to simulate. But the one I feel at home with is PET149, DOS based.

A part of my original question hasn't been still answered. Are there programmes which can correct the frequency response characteristics of the amp chip on the soundcard and provide as flat as possible signal from 20Hz onwards?

Thanks again.

[Ron E]

The first equation is for designing boxes, the second is for measuring parameters.

As for correcting the response of your soundcard, there is nothing you can do. If you recalibrate your T/S setup for each frequency in that range, you will cancel out the effects of the soundcard and/or your meter (many meters roll off below ~40 and above 1kHz).

[r_s_dhar]

Ron,

You are right. I am not advanced, but I want to go as far as I can. I am basically a university teacher with a PhD in English Literature. My interest in classical music has (mis)led me into electronics. There was a time when I thought all I had to do was to buy one of those Japanese HiFi Decks. I got an opportunity to play my collections on a pricey music set -- the result was disappointing. It was then that an engineer friend of mine told me that I should build my own set if I wanted dedicated performance. I have covered a considerable distance since then, but then I have "miles to go before I sleep."

I am not satisfied in just filling in blanks and getting results from computer programmes. I want to know what and why I am doing something. At present I am building a dedicated millivoltmeter to do my TS tests. My present problem is that although I understand the TS equations in general, I do not see how inidividual Q elements determine the Vb and SPL. I have tried one simple method of varying these factors in simulations to see how the curve comes out. But that is a blind method.

Thanks.

[roddyama]

r_s_dhar,

The various Q factors are numbers that represent the relationships between various physical parameters of the driver, the box, or the driver in the box. It's the physical parameters that determine the value of the various Q factors.
If you have a given driver, all of your driver Q's are set. You can only alter the parameters of the box and in that way the total Q of the system.
You need to obtain some of the papers from the 70's to get clearer understanding of how the relationships between the parameters form the various Q factors.
Try back tomorrow, I might be able to set something up to get some more substantial information to you. In the interim, try some web searches on the Thiele and Small parameters.

Rodd Yamas***a