Dimensional dilemmas

kinku · « **on:** 21 Mar 2013, 12:48 pm »

I have some vague plans about making a SDFR in Bass reflex enclosure. So far came up with two Brands Fostex and Mark audio. I have a plan to use Dayton audio cabinet with fixed volumes as enclosure.The volumes might match but not the height, width and depth recommendations. I am trying to find out how much those parameters affect the result. How much variation in volume and other dimensional parameters is allowed in a speaker design. I also read Fostex provided parameters are not accurate anyway since people get better results from increasing volumes. Hope I can hear from some experts.

planet10 · « **Reply #1 on:** 21 Mar 2013, 05:19 pm »

In a BR, as long as the aspect ratio does not become too extreme, LxWxD has only secondary effects.

dave

FullRangeMan · « **Reply #2 on:** 21 Mar 2013, 06:41 pm »

Seems to me Fostex usually supply small litrage projects to the jap market, where the average room is small.
You can not go wrong if use the max litrage allow for the driver.
Litrage is a range, with a minimum amd a max value, bigger boxes favor the bass performance.
Various manufacturers dont inform this value though.

kinku · « **Reply #3 on:** 21 Mar 2013, 08:36 pm »

Dave,what will you consider as too extreme from from aspect ratio.Which aspect is important H X W vs H X D or WXD ?
How can I find out the maximum literage allowed for the driver?

planet10 · « **Reply #4 on:** 21 Mar 2013, 08:51 pm »

Quote from: kinku on 21 Mar 2013, 08:36 pm

Dave,what will you consider as too extreme from from aspect ratio.Which aspect is important H X W vs H X D or WXD ?
How can I find out the maximum literage allowed for the driver?

There is no fixed ratio, as you lengthen one dimension the enclosure morphs from a BR to a ML-TL. Say one dimension 3 or 4 times the others.

When i calced this one out for my alignment box sized maxed out at about 6.5 litre,

dave

kinku · « **Reply #5 on:** 21 Mar 2013, 09:18 pm »

Quote from: planet10 on 21 Mar 2013, 08:51 pm

When i calced this one out for my alignment box sized maxed out at about 6.5 litre,

dave

Thanks Dave.Sorry for being so Dumb. I did not get it at all.How did you get the 6.5 Litter?

JLM · « **Reply #6 on:** 22 Mar 2013, 07:24 pm »

Go with a bigger cabinet volume and add blocking of some sort to reduce down to the "perfect" number.

planet10 · « **Reply #7 on:** 23 Mar 2013, 03:10 am »

Quote from: kinku on 21 Mar 2013, 09:18 pm

How did you get the 6.5 Litter?

Simulations.

dave

FullRangeMan · « **Reply #8 on:** 23 Mar 2013, 03:45 am »

Quote from: kinku on 21 Mar 2013, 08:36 pm

Dave,what will you consider as too extreme from from aspect ratio.Which aspect is important H X W vs H X D or WXD ?
How can I find out the maximum literage allowed for the driver?

Look on famous book Loudspeaker Design Cookbook(Vance Dickason) page 37/38 had the formula and some tables.

kinku · « **Reply #9 on:** 25 Mar 2013, 10:40 am »

Upto 10 % change is allowed it seems.

FullRangeMan · « **Reply #10 on:** 25 Mar 2013, 12:57 pm »

Quote from: kinku on 25 Mar 2013, 10:40 am

Upto 10 % change is allowed it seems.

For Golden Ratio dimensions also is said is allowed 10% change with similar resuts.

kinku · « **Reply #11 on:** 25 Mar 2013, 01:31 pm »

What is golden ratio dimensions, may I ask?

planet10 · « **Reply #12 on:** 25 Mar 2013, 06:40 pm »

Quote from: kinku on 25 Mar 2013, 01:31 pm

What is golden ratio dimensions, may I ask?

A set of dimensions that yield a ratio of sides that is ~1.618:1:0.618

dave

FullRangeMan · « **Reply #13 on:** 26 Mar 2013, 02:50 am »

Quote from: kinku on 25 Mar 2013, 01:31 pm

What is golden ratio dimensions, may I ask?

This a is topic about how treat the inside of a enclousure for a FR driver.
Please note post #18.
http://www.audiocircle.com/index.php?topic=100689.0

JohnR · « **Reply #14 on:** 26 Mar 2013, 10:38 am »

I'm very curious whether anyone has ever actually verified that the "golden ratio" has a meaningful use in speaker design. Without going to look it up, I do recall that e.g. Toole shows graphs that show ranges of optimum ratios for room size, and the golden ratio seems to have very little to do with it.

So as far as the speaker box itself is concerned, are any there studies that have shown any benefit?

FullRangeMan · « **Reply #15 on:** 26 Mar 2013, 12:57 pm »

It is said golden ratio proportions had less resonances than others sizes.

JohnR · « **Reply #16 on:** 26 Mar 2013, 01:07 pm »

Quote from: FULLRANGEMAN on 26 Mar 2013, 12:57 pm

It is said golden ratio proportions had less resonances than others sizes.

Yes, it is said, but if you look at the charts it's not shown.

Sorry but I would really like to see evidence to support that golden ratio is meaningful for audio. I'm not saying it's not, as I don't have anything to prove BUT is there more than just assertions...?

FullRangeMan · « **Reply #17 on:** 26 Mar 2013, 01:12 pm »

The only mention I see in audio are in that book Loudspeaker Cookbook, it recommend if not use auric number use bracing inside the box.

Many old churches were made with this system, unfortunately some music halls dont use it to favor a more ample space to bigger audience.

JohnR · « **Reply #18 on:** 26 Mar 2013, 01:28 pm »

Quote from: FULLRANGEMAN on 26 Mar 2013, 01:12 pm

The only mention I see in audio are in that book Loudspeaker Cookbook

Hi Gustavo, the copy I have is the 6th ed - what section number/title is the mention in yours?

FullRangeMan · « **Reply #19 on:** 26 Mar 2013, 03:49 pm »

I look in this book now but was not able to find it, I remember had to read it somewhere.