transmission line - is this ok?

[gafhenderson]

so - 1520cm2
sl - 520cm2
sl/so - 0.34
L - 275.18cm
approx unstuffed tune - 25hz.

i always wanted to make t-line speakers so i'm going to stick with that fantasy instead of messing with ported boxes.

my question is can i use the clamshell isobaric with a t-line in this fashion?

is there a problem having the port so close to the drivers, interference comb filtering etc? would it be better to turn it once more and fire side/floor through the bottom side? tried to use the port/opening to offer some protection to the outside driver.

are less folds, more simple mazes better than highly complicated rat mazes? in my ignorance i decided simple would be better by reducing possible reflected sound?

i've tried to use hornresp but its incredibly complicated for the uneducated and i can't for the life of me figure out how to put this in, so i have no idea what the frequency response would be. any pointers or links for using hornresp to model a simple Tline like this?

bjorno modelled an ofset driver transmission line with one of the drivers i am going to be using and it gives the best design (see bottom) i have bundled over so i want to stick with the Tlines. just trying to learn by playing with my own designs instead of relying on other people's work, give a man a fish and that all proverb.

thanks for your time

[NEO Dan]

If the intent is to learn build the design bjorno provided.

[gafhenderson]

Originally Posted by NEO Dan

If the intent is to learn build the design bjorno provided.

i don't know how to build it! that's a page of lots of complicated info and i only understand 1/10th of it fully, without having any working reference. i need some point of common reference to learn from, being given something like that isn't a point of common reference as its completely surpasses my level of understanding. what i've done is to my level of understanding, from there i can take another step forward etc if a discussion over the design i have understanding of commences.

also there's questions in there that are applicable regardless of bjorno's design that can be answered.

[bjorno]

OOps!

[bjorno]

..my question is can i use the clamshell isobaric with a t-line in this fashion?..is there a problem having the port so close to the drivers, interference comb filtering etc? would it be better to turn it once more and fire side/floor through the bottom side? tried to use the port/opening to offer some protection to the outside driver...

Hi,

I'm on my way to the bed...but: Yes a clamshell is easy to model and a port located close is at far-field summation an asset that is what usually is the case when modeling a to an TL an evolved T-TQWT/TQWP too.I will tomorrow post a model of your first TL line-out and give an example for a clamshell single folded enclosure...

b

PS: You can test with HR using my first suggestion as a template but in the main screen invoke ND instead of OD.

[bjorno]

FYI, Why not?:

b

[gafhenderson]

Originally Posted by bjorno

FYI, Why not?:

b

you tell me, you're the expect ha!

does this not turn it into some kind of bandpass(?) design? i have literally been copying the basic ideas of everything i can find as a beginning point to learn. if enclosing the outer driver like that can be done without making the system perform oddly or poorly then it would be favourable to an open driver (pets in the home are very curious and chew things).

like i've said before i'm very much at the mercy of this boards knowledge in directing my learning and research in order to start my journey into DIY audio. my end intention will be to make single unit full range transmission line or horn speakers before i then venture into the realms of amplifier construction.

[tb46]

Hi gafhenderson,

Post #1: "...give a man a fish and that all proverb."

Post #7: "... i'm very much at the mercy of this boards knowledge in directing my learning and research in order to start my journey into DIY audio."

While I think you are at nobody's mercy than your own:

When arranging two speakers in an isobaric configuration you are basically creating a new driver; don't think of it as two drivers, one inside the box, and one outside. Think of it as one speaker. Once you do that it becomes apparent that your design is a basic transmission line with about a 3:1 taper ratio. Nothing basically wrong with that, but what would the optimum dimensions be? Are there other similar designs that perform better? Should the driver be at the very end of the duct, or would it help to move it to a different point? Should the duct be 1/4 wavelength, or 1/3 wavelength, and wavelength of what?

Lucky for you there are today a number of wonderful simulation tools that allow you to design such an enclosure without having to go through numerous iterations in wood (build - test - rebuild.....). Take the time to work through the basic help file in Hornresp, print it out, read it one item at a time. Don't go past anything you don't understand. It'll be a lot less daunting piece by piece, just like bjorno's complex designs; once you take them apart, it all makes sense. Hornresp is not an endpoint. From there you can go on to AkAbak.....

Otherwise, please, take another look at my suggestion in Post #23 of your ealier thread: 'isobaric' schooling help please.

Regards,

[planet10]

To adjust for using the compound, isobarik driver, halve the cross-section, and leave everything else the same.

You want to try to retain the offset -- it reduces the ripple.

dave

[planet10]

I did a little bit of sketching. An isobarik driver will not physically fit into the Bjorno line. Unless you are size constrained it makes a lot more sense to do a push-push line, take full advantage of the volume displacement, and active vibration cancelation.

A question that comes up is how come bjorno's line is tuned as low as it seems

dave