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Old 4th June 2010, 03:42 PM   #1
calypso is offline calypso  Italy
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Lightbulb calypso's poor man solution

hi all, i will build a boombox out of 4 coax 4 ohm 6x9 speakers attached to two arjen's mkiii ta2020. their housing will be, as most as i can, pvc pipe. From time to time i'll update this thread with progress in designing and realization.

i'm a noob, i did a lot fo fails! i did a lot of efforts! but now i have a challenge... building a boombox that can be easily turned to a tls with two or three moves...

my best inspiration came from Saturnus and ArjenShenzen. a lot of respect and kudos to them. for what they know, fow how they give it to us.

weak point of this: what i can't realize by myself... the speakers.
i start by attaching a winisd pro file of them.
vendor's pdf may be seen at http://www.hertzaudiovideo.com/Doc/pdf_ecx690.pdf

being this a thread: your help and any kind of feedback is warmly welcome.
Attached Files
File Type: zip Hertz Energy ecx 690.zip (750 Bytes, 34 views)
 
Old 8th June 2010, 01:56 AM   #2
calypso is offline calypso  Italy
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looks like transmission lines are very hard to design... but i'll try with a 1/4 wavelength design, in the easiest and most unpredictable way.

so 67hz shall be the fs of my speaker. 5.1194 meters the wavelength of the fs. a 0.9 coefficient (don't remember where i saw it) for the stuffing gives me 4.60746, and a fourth of it is 1.151865 meters. so i have to build a pipe whose length is 1.151865m + 7.8cm speaker inside (=1.229865 = 1.20meters) speaker length. then i will stuff the last half of the pipe until i'm satisfied.

the shape will be a U: a 180° curve with two elbows will join two equally long sections of the pipe. my driver is a 6x9, so i should use a 25 cm pipe: no way, too expensive. 20 cm pipe is cheaper, and i will stick with it. i will buy a 20 cm x 1 meter pipe, a 20 to 12.5 cm reduction to taper the line before the 180° turn. the 180° turn will be realized with two 12.5 cm 90° elbows (not really circular, but cheaper than three of 33°). then after the turn a 12.5 pipe will complete the total length of the tube, and will be stuffed with old pillow wool (this is the 0.9 coefficient). yes, i will use car damping sheets for the first half of the line.

so this will be:
1) speaker will be housed in a 40cm long, 20cm large pipe.
2) a reduction from 20cm to 12.5 cm, and two 12.5cm large 90° elbows will create a 40cm long, 12.5cm large joint pipe of 40 cm.
3) a pipe 40cm long, 12.5cm large will complete the transmission line.

speaker will be hooked to a 20cm large cap, cutted to fit it. cap, pipe, and reduction will be glued together.
the two elbows and the 12.5 cm x 40 cm long pipe will be glued together.

this transmission line will be composed of two pieces: the speaker pipe, large 20 cm, and the reduction to 12.5 cm. and the 180° turn and line end pipe 12.5 cm.
so 40cmx20cm plus 80cmx12.5cm

the speaker pipe will have a 19 cm diameter (subtracting pvc and car damping material) and a 40 cm length. the glued reduction will match driver volume. volume will be 10 liters
the 180° turn and transmission end glued together will create a pipe 80cm long, 9.4 cm large: 5.5 liters.
total volume of the transmission line will be 15.5 liters. vas of my speaker is declared as 25.2 liters.

so what are the poor man solutions/deceptions:
1) my driver has a low qts. seems like it's not suggested for transmission line. i'll try anyway.
2) tapering should be realized progressively. my tapering will be a reduction from 20 cm to 12.5 cm. in the half of the line
3) the tls end area shall be at least the same of the cone, but mine will be something like half. in detail: my cone area is 229 cm², like a pipe of 17 cm. but the pipe i'lluse will have a 12cm inside diameter, having an area of 113 cm². "bice catastrofa"
4) not a really circular 180° turn - two 90° elbows.
5) the transmission line will have a 15.5 liter volume, instead of the proposed 25.2l vas.
6) a custom glue/silicone/pvc/dunno adaptation will be created to fit a 237cm large 6x9 speaker in a 20 cm large pipe.

being this a thread: your help and any kind of feedback is warmly welcome.
 
Old 8th June 2010, 08:31 PM   #3
r0b is offline r0b  Germany
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Hi,

so I don't have a clue about TMLs, and I am probably not the only one. You have my assurance, that I'll keep reading this thread though, just don't have anything to say

The frequency response of the speaker looks quite wobbly. 10 db between 500Hz and 2 kHz. Let's hope the cabinet somehow fill in in that range. Keep us posted!

good luck

rob
 
Old 9th June 2010, 12:43 AM   #4
calypso is offline calypso  Italy
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thanks r0b...
about speaker response... i see. maybe manufacture putted in the same graph the cone and the tweeter's response. and 500hz is the lowpass filter for tweeters. (maybe).

first mod from my ideas is the end of the tube. the speaker pipe will remain the same. but i will build two different ends, to evaluate best result. the first is, as previously described, 12.5 cm large. the other will be 16 cm large, realizing an area of 188 cm².
the 12.5cm end pipe will have half of the cone area.
the 16 cm end pipe will have the 82% of the cone area.

another variation may be reducing tl to 1/3 wavelength. them say gives a more present bass enhance. sincerely dunno.

today i modeled the pipe caps to fit the driver in them. as already wittten, they are 225cm large, and the pipe is 20 cm large. succeded! but i have two rectangulare holes (5x40mm) on the outer side of the driver, where the pipe reaches the border. shall equip with a cam to show. anyway, i'm thinking on two solution for this:
1) use silicone - easy (will it glue to pvc?)
2) apply a pvc ribbon - hard

i give t/s parameters of drivers

fs 67hz
qms 3,23
vas 25,2 liters
cms 0,337 mm/N
mms 16,79 g
rms 2,179 kg/s
xmax 3,5 mm
xmech 5,25 mm
dia 171 mm
sd 229,3 cm²
vd 0,0803 liters <- this is strange, i suppose should be 0,803
qes 0,77
re 3,2 ohms
le 0,62 mH @1khz
le 0,07 mH @10khz
z 3,84 ohms
bl 5,4 Tm
qts 0,62
no 0,949%
1-w spl 91,92 dB
2.8-v spl 95,9 dB

and more:
some simulation for the speaker pipe without the transmission line end (only the 40x20 cm pipe)
2 examples:
1) with 12.5 cm reduction - has a port large 12 cm and long 5 cm - coloured blue - tuning frequency 156,68 hz - eq highpass butterworth n=2 fc=100hz
2) with 16 cm reduction - has a port large 15.5 cm and long 5 cm - coloured white - tuning frequency 185.84 hz - eq highpass butterworth n=2 fc=100hz
- scale is up to 15db, from 100hz to 600 hz
Click the image to open in full size.

lot of questions:
1) [eq highpass butterworth n=2 fc=100hz] is this the correct way to simulate a 100hz basscut via input capacitor on winisd?
2) how to interpret those results as saturnus did for his boominator?
3) how do i apply a q of 1.2 to winisd simulations?
4) what else should i do to revise those results for an outdoor use?
5) is the 16 cm x 5 cm port affordable in terms of bass response?

- returning to tls -
6) what transmission line *length* would you suggest to achieve the best bass response?
7) what transmission line *length* would you suggest to achieve the best midrange response?


a lot of thanks goes to the willing goodman who will share with us his valuable knowledge.
in the meantime i'll ask google to borrow me ancestors' wisdom

Last edited by calypso; 9th June 2010 at 12:47 AM. Reason: i don't know how to put images in my post. maybe mod can give help, thanks
 
Old 9th June 2010, 02:19 AM   #5
calypso is offline calypso  Italy
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things messed up! mjk suggest to tune 10hz lower for high qts drivers. and mine is 0.62.
i will adopt 1/3 wavelength, for better bass response.
resulting length is 1.80meters, ouch!
so speaker pipe will become 60 cm long. and 120cm will remain for turn and end.
 
Old 9th June 2010, 02:53 AM   #6
calypso is offline calypso  Italy
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once for all, the pipe diameters.
20 cm pipe has an inner diameter of 192mm, car damping foil is 1mm thick = 190 mm
16 cm pipe has an inner diameter of 154mm = 154 mm (car damping foil is not necessary)

speaker pipe will be 190x600mm = 17.011724
will have a vent 154mmx5cm
tuning frequency will be 141.89hz (given volume and vent, winisd doesn't allow to modify tuning frequency)
Click the image to open in full size.

questions again:
1) [eq highpass butterworth n=2 fc=100hz] is this the correct way to simulate a 100hz basscut via input capacitor on winisd?
2) how to interpret those results as saturnus did for his boominator?
3) how do i apply a q of 1.2 to winisd simulations?
4) what else should i do to revise those results for an outdoor use?
 
Old 9th June 2010, 09:37 AM   #7
Eva is offline Eva  Spain
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This is the class D forum, and people with experience in transmission lines is not likely to read your posts. I suggest posting in the loudspeaker forum, maybe here: Full Range - diyAudio
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Old 10th June 2010, 04:04 AM   #8
calypso is offline calypso  Italy
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than you eva, but further i will discuss the ap section. the amps will be two arjen's ta2020 mkiii, with some additional wiring. i would like to add an input caps switcher to enable a bass cut, and furthermore a panel mount mp3 player will be mounted to it.
at that time i would like to ask help for matching player and amp impedances, and some additional info on grounding.
do you think i can move this discussion in the full range driver section, and then make it return back here?
 
Old 11th June 2010, 03:09 AM   #9
calypso is offline calypso  Italy
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as eva suggested, moved thread to ful range driver.

new address
calypso pvc boombox
 
Old 11th June 2010, 04:27 AM   #10
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I moved this over here. Tell us if you want the two threads merged into one. Please do this by reporting the post rather than PM'ing me as I will be away from the computer for the next few hours.

Thx.
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