I've just finished my first TL but...

mashypie

Member
2010-11-03 10:37 pm
Im a bit confused with the response

Bearing in mind I have no test equipment, this is purely though listening

Some tracks sound fantastic, suprisingly low considering its a 3" driver, you kind of look at them in suprise that they are generating it when you are used to having a 10" sub boost your bass!

Yet others seem to have no bass whatsoever

Would this indicate that I need to spend more time tuning them? Or I've got something wrong along the way?

I've added and removed foam until I've got what I consider to be a good sound (too much foam meant no bass, to little sounded a little sloppy/flappy)

And I would like them to end up as a 2 way system as I think the treble is a little harsh at the moment. But I'm just confused that some tracks seem to have no bass on them.....

Does anyone have any experience with them?
 

mashypie

Member
2010-11-03 10:37 pm
Driver is a B3N from IPL Acoustics, do you need the specs? Fs is 77, Qts 8.6, I didn't take anything else into consideration, but since making I've learnt a bit more about Qts and the BL too

TL is small, tried to upload a pic but they are about 3meg in size, tuned to 77Hz which is the drivers Fs, line length 1.05m folded into 4

Amp is a Teac, just a standard all in one, I dont go for seperates or anything fancy at the moment

Room is approx 14x12 foot, all hard surfaces, one sofa
 
Are you sure those track have much bass? Listen to them on another system. To me, most music, that is not heavy in the bass, sounds just full and good on a FR, the bass blends in so well it is part of the music and does not stand out.
Also make sure you are in the EXACT same place when you listen. Even a small difference might put you in a node in that blank room.
 

bobica

Member
2009-01-21 10:56 pm
I had similar experience with my no measurement and simulation project :D
I suspecct that it is issue with high second imp. peak of TL !
With some more damping attempts you may change behavior od your TL and get more defined upper bass sound! I meant to increase damping of the cabinet, or change the density versus different areas
P.S. sorry for my english :(
 

mashypie

Member
2010-11-03 10:37 pm

Yeah thats the one, xsection goes from 39.2cm2 to 14.7cm2

I messed up a bit with the xsection as I read from the speaker above on the chart, and I used my own measurement of the speaker area and put the area at 19.c when it should have been 30cm2, though I dunno how they come to that number, it doesnt curve that much.

Got some pics now

do all posts have to go through a mod?

fordiyaudio02.jpg

fordiyaudio01.jpg
 
Ah! I don't believe there's nearly enough stuffing in there, and of the wrong density too, I'd imagine. I have larger TLs, and note the same thing as you - I'm going to go into them next week with some (more) old pillows and see what's afoot, measurement mic will arrive also soon and so I'll see if the over-powered low end is coming from a) the TLs themselves or b) just a room resonance.

You might try to stuff it more like this :
[IMGDEAD]http://blog.liammartin.com/EI6GXBlog/Home/Entries/2010/5/4_Done_and...dusty%21_files/IMG_7528.jpg[/IMGDEAD]

I have that driver as my mids, yikes! I must try a wee TL with its larger brother (B4) soon.

L
 
Yeah thats the one, xsection goes from 39.2cm2 to 14.7cm2

The line is too long even un-stuffed for a 77 Hz tuning, it needs to be around 87 cm long, so once damped it basically has a large sealed cab's response.

That said, its Qts is high enough that a ~89.5 Hz tuning yields the widest ~flat BW, so you may want to consider building new cabs.

GM
 

mashypie

Member
2010-11-03 10:37 pm
The line is too long even un-stuffed for a 77 Hz tuning, it needs to be around 87 cm long, so once damped it basically has a large sealed cab's response.

That said, its Qts is high enough that a ~89.5 Hz tuning yields the widest ~flat BW, so you may want to consider building new cabs.

GM

How do you come to this conclusion?

I've gone off the usual 1/4 length and lopped off a 5% that I read somewhere to do with the way the port interacts with the room?

87cm to me seems very short, My next project was with some Fs 90Hz speakers and I worked that out to be a 90cm line, though I've not started buillding them yet.

How does the Qts affect the tuning?

I may have another play around with the stuffing, though it seemed to be a bit flat with more stuffing in, there wasnt the big drop in bass I get at the moment. I want to keep asmuch of the bass as poss!! :)
 
I've gone off the usual 1/4 length and lopped off a 5% that I read somewhere to do with the way the port interacts with the room?

Tapering the line as you have means that it needs to get shorter to maintain tuning, and to get max bass you need to tune a bit higher than Fs, and then there is end correction (the 5% would be a simplification of getting that).

You could always cut the top off the box (the end that the last fold is in) and see if it gets better.

dave
 

mashypie

Member
2010-11-03 10:37 pm
Tapering the line as you have means that it needs to get shorter to maintain tuning, and to get max bass you need to tune a bit higher than Fs, and then there is end correction (the 5% would be a simplification of getting that).

You could always cut the top off the box (the end that the last fold is in) and see if it gets better.

dave

Is there any science behind it? Such as if its tapered by x amount then it needs to be shortened by x amount? Or is it through trial and error?

Same goes for the 5%, I merely came across that in one article but there was no reasoning behind it

Sorry I'm a bit of a do-er then a thinker, rather than a thinker then a do-er. I'm not guna learn anything if I keep it all theory based!

Thanks so far, I'm really enjoying the sound I get with this set up....

diya01.jpg

diya02.jpg

Changing the stuffing seems to work well!!
 
Is there any science behind it? Such as if its tapered by x amount then it needs to be shortened by x amount? Or is it through trial and error?

About ~2000 (fall 1999) MJK (& Auspurger) presented 2 different TL models which matched in results & with actual builds. MJK has been continuously improved.

Classic TL design -- which it sounds like you used -- rarely gets an optimum line, and most of the time produces something not all that good.

dave
 

mashypie

Member
2010-11-03 10:37 pm
The line is too long even un-stuffed for a 77 Hz tuning, it needs to be around 87 cm long, so once damped it basically has a large sealed cab's response.

That said, its Qts is high enough that a ~89.5 Hz tuning yields the widest ~flat BW, so you may want to consider building new cabs.

GM

Fair play, I will give you that one, taken from the AlphaTL I take it?

This has a much better sound, straight tube, tuned to 89Hz ish, about 91cm long, 2x Sd all the way, PMC type design

Almost prefer this to the RTL3s

Not such a big fan of the height though, I dont like speakers that are 75% cabinet

DSCF9973a.jpg
 
Actually, I took it from an early '70s Altec Tech Bulletin that I use for my own offset driver designs, but it's a well known alignment, so no surprise Rick uses it in his Alpha TL paper. Indeed, when I post all the details of such a design I use his with reference since it's a known, proven one. I didn't take the time to see what CSA mine/his math calculated though, so is 2x Sd it?

Interesting, most folks like a 'FR' driver up around ear height due to HF beaming.............

GM
 

mashypie

Member
2010-11-03 10:37 pm
I just took a random guess with the Sd. I figured I didn't know the effect of the taper and Ricks paper suggested a fatter tube for less attenuated bass, so I thought a fixed and fairly large CSA would be easier and better for the time being.

I'm still only beginning with this, this wasn't supposed to be a FR project but as I know nothing about crossovers and I do quite like the sound it will have to stay as it is until I've learned a bit more!!

Re the ear level thing, or beaming, I hadn't taken it into consideration, and its something I've only recently come across. Though I'm not much of a fan of tall speakers with tiny drivers, was trying to avoid buiding something like that!