line array build questions and pictures

[lolojr1]

this will be the first post at my first line array design / build

please comment and ask questions about anything

im not to concerned about total sound quality or maximum spl but to learn and experiment and have something really cool to show to friends would be nice too

my first major hurdle is how to mount my speakers, i have (36) 2.1"x3.7" rectangle speakers per side

http://s270.photobucket.com/albums/jj115/lolojr1/?action=view&current=100001.jpg

and (12) 4" round speakers per side no close up yet sorry

http://s270.photobucket.com/albums/jj115/lolojr1/?action=view&current=00004.jpg


the round speakers will be cake, a hole saw the right size has already been purchased and test fitted to be perfect

the rectangle speakers will be a pain,i have 2 ideas so far please tell me what you think

option 1

drill a hole at the depth of my drill pres's throat's depth, roughly 4.25"
36 times at a spacing of the width of the speakers shortest dimension 2.1" then rip the piece in 2 through the center of all of the holes to form 2 pieces of wood with 36 half round shapes cut out of them and then attach the speakers leaving a small opening at each end of the line to be filled in after assembly

option 2

make a jig and router out a template for each speaker individually

i have a problem with each option

option 1

the baffle is not going to be one piece of wood making it seriously weak and the speakers have a plastic basket so i don't want to break them with the stress.
i can then double face the baffle in witch i can then cut out a large rectangle and recess the speakers with a round over bit or a chamfer depending on my mood or just double the back up and laminate the front to make a smooth continuous look.

option 2

if my template is just slightly off in its dimensions they will compound and my center to center spacing will be off the farther down the line i work.

doing that much routering is going to be a pain. its going to make a huge amount of dust. its winter and its cold here my garage isn't heated and i store my custom car tons of tools ,electronics and stuff i generally wouldn't want to cover in mdf dust i can work with the door open for a while and do some work in the driveway or just move the car out until it snows


has anyone ever done this type of build ?

how did you cut the holes

 

[lolojr1]

oh i will be making these open baffle and i cant decide how wide to make the baffle

i had the graph with speaker size on one axis and low frequency on the other axis but i cant find it anymore anyone have this or know where to find it ?

and also all voice coils are 8 ohm so i am working on my wiring configuration now

 

[lolojr1]

well after wasting a whole sheet of 1" mdf i had a great idea

i was thinking on mounting the speakers to the front or rear of the baffle but i couldn't get a place to put a screw due to the odd shape

so i took the router and made a slot all along the length and made a channel to slide all of the speakers into


here area a few more pictures

the first attempt -failure

then the final roundover of the new and improved design

i just bought this circle/edge guide and im not impressed at all with it

although i do love my ripmaster

 

[auplater]

been there, done that

here's the 1" cherry (four boards biscuited together) to make a 6' h x 21" w baffle for my linesource using BG 75's, etc. from 3 years ago..

Note the clever glass template for cutting the mid woofer holes

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

finished speaker

An externally hosted image should be here but it was not working when we last tested it.

The long slot looks to be the way to go. looks like you need a little more shoulder to mount the screws. You might also run a cross brace every 3 or 4 speakers to strenghten the final baffle.

I bought a jasper jig for circle cutting after this project... wouldn't be without it for future projects

John L.:

 

[lolojr1]

hose are gorgeous cherry wow im using mdf haha

i am actually going to use a slot and just slip all of the drivers down it no screws at all

i think it might leak a bit but its a learning experiment what the hell right if its bad i can silicone or hot glue between the drivers

im running the woofertester 2 right now just to see what they have for specs

the first draft will be about 5" wide by 8" deep and the driers are going to be mounted about 3/4" back

i wanted the jasperjig but saw this and it was on sale i should have thought it out cheaper isn't always better !!

i will have a few more pics in a while

 

[lolojr1]

here they are installed just temporarily though

i have to do the wiring next week and cut the sides to length but its getting there

not much room for wiring is there?

 

[auplater]

lookin good!

That's a clever way to "stack" them... you might need to stuff some loose batting behind the drivers if you hear any cavity resonance... may sound alittle "one note boomy" without it.

Here's a close up of the cherry "figure"

An externally hosted image should be here but it was not working when we last tested it.

What drivers are those? The baffle width will determine the low frequency response (aka baffle step) which you can compensate for to some degree in the xover. Mine ended up @ 21" width, which, iir, works out to ~310 Hz where the radiation changes from 1/2 space to full space (baffle width = 1/2 wavelength).

I added the back swept wings to increase the width and also decrease the perceived footprint viewed from the front.

Here's where they live now...

An externally hosted image should be here but it was not working when we last tested it.

John L.

 

[lolojr1]

i dont know what manufacturer they are i got them on ebay about 2 years ago when everyone was doing the nsb line arrays

i can give a woofertester output if you like but its on my other computer that isn't connected to the net right now

they had a cup over the bucking magnet but i took it off due to it being bigger than the largest dimension of the basket now there is just the magnet and some glue i have to get off

i used to have all of the info to design these when i bought them then i converted from m$ xp to Linux Ubuntu

could you send me in the right direction to find the baffle step graphs and such i cant remember where to find them

i dont think they are going to go to low and that is why in the first post i have a dozen 5" drivers just in case they dont , i will ad another line to the side with those although i dont want to get into xovers just yet

they have an fs of 165 hz kinda high i think

well the wiring should be a cinch, 6ohm drivers at 36 each comes to a 6 ohm final impedance i will even be easy to wire up



do you have xp running on your TV? if so nice i like that i bet it would look really cool with the electric sheep screen saver (google it its really cool ) running on it and those beauties playing your favorite tunes

and what is the long driver on the right in the close up that is aluminum colored?

 

[sumacSK]

Hi,

Nice project.. It seems that upper freqv. limit for those square drivers will be around 6.4kHz (based on your dimensions). Are you going to use tweeter line too?
I think that those 4" drivers are not going to be enough for serious low end... If I were you I would rather use stereo subs instead of those 4" speakers array..

good luck
Martin

 

[lolojr1]

how do you know it will only reach up to 6.4k hz? and what affect will longer/shorter sides have on low frequency ? what should i expect the to go down to ?

i will be testing the results and will posting them here when i am done building (audiocontrol 3050)

the 4"rs were a really good deal so i bought them too if i need them i have um thats all or i might do another array all together

i do have 2 8" woofers i could add to thisn a small box in the base or something similar.

i currently use 2, 12" subs for low end in a somewhat large ported enclosure with about 400 watts each

and one other thing with the wiring
i have 36 drivers per side this gives me easy wiring
6 parallel sets of 6 series drivers to achieve a impedance of the same as one driver 6.4 ohms .

is there a better way to wire the paralleled sets series or the series sets paralleled ? the final impedance will be the same but will either way affect final outcome?

 

[sumacSK]

Hi,

I strongly recommend you read this white paper: http://www.audiodiycentral.com/resource/pdf/nflawp.pdf There you find all the answers you need..
It will reach up higher than 6.4KHz but comb effect will ocurr as the center-to-center distance of your drivers will be 2.1". I don't know parameters of your drivers (like xmax) but since you use this many of them I believe they will go down to they're Fs easily. You should really consider using tweeter array. (for example those 5$ dayton small domes)
As for wiring, consider power tappering-also explained in the white paper..

Good luck
Martin

 

[lolojr1]

thank you i couldn't find that info and forgot about that paper

i might add a super tweeter or an array of the onkyos if it is really bad ill have to assemble it and go from there

i have read pros and cons on power tapering i think i will go straight for now as i don't have any real good place for these yet and i believe that distance from the array affects the tapering configuration ? a i correct in that thought

anyways off to read

 

[lolojr1]

Ok, update i have read that pdf and brushed up on my memory a little, some of the math is a little to much for me but im going to read it again.

Still i have a few ?s

I can get tweeters very cheaply (pyle pro aluminum pro dj super tweeter stuff) that are a little bigger 2" od or slightly larger.
would they work , will i get the combing effect if i use 2 lines of the bigger tweeters and have them next to each other 1/2 of a diameter higher on one line?

or should i get some apex jr onkyo tweeters hoping he has the diy forum discount still ?

in that article it states that the output of the tweeter and mid lines will have a different level and power tapering will help that.
should/could i do a full lenght tweeter line and use an Lpad? or should i just keep adding tweeters till the output is equal and have a line of whatever length that matches up output wise?
or should i wire a full length line slightly higher impedance to make up for the imbalance?

 

[sumacSK]

Hi,

2" tweeters are too large... (actually its as large as your mids..)
Signal from the end of array have longer distance than signal from center. This means that these signals wil arrive in different times. To reduce this effect you can use power tapering (signals from the end of array become less noticable). Tweeter line depends on how low you want to cross them and how far you want to extend near field.
This is theory, but since you allready have array assembled, why you just don't try it as it is.....?

 

[lolojr1]

well i am going to see what i like dislike about this setup wired series parallel 6 by 6 no tapering.

it will take me all day to strip and crimp the wires but i want to hear the comb effect not just read about it.

then i want to add a horn for a tweeter to see if it can keep up,doubt it but i want to try.

i was asking if a 2" tweeter would work if i used double the number and have 2 lines splayed 1/2 a diameter apart vertically and as close as possible horizontally

like this but obviously closer together and minus the .'s
sorry i cant use any cad programs or sketchup to draw the design

o
.o
o
.o

 

[auplater]

combing

The staggering could help, but you'll also introduce horizontal combing and further muddy up the image. The staggered array should move the onset of combing up in frequency, and depending on your listening distance may or may not be too intrusive.

However, I believe that a second problem with combing in multi driver arrays besides the obvious nulling that occurs as you move your ear up and down at the combing frequency and position, is blurring of the imaging at any distance, since you have complex polar behavior blending with room reflections, etc.

This is one of the reasons I used planar drivers in my setup; avoids vertical combing altogether. I do get some horizontal combing between the 25" and 72" drivers, but the lobes are ~ 60 degrees off axis and have a narrow profile, so one has to hunt for them.

John L.

 

[lolojr1]

is there any cheaper planar drivers all the ones i have seen are quite expensive and this is just an experiment at this stage

what brand did you use and if you dont misn what was the cost of them ?
do they require any special x-over networks?

 

[auplater]

is there any cheaper planar drivers all the ones i have seen are quite expensive and this is just an experiment at this stage

what brand did you use and if you dont misn what was the cost of them ?
do they require any special x-over networks?

hard to say... if you're talking $10 - $20 speakers, I doubt it.

here's a build thread I started last year

http://www.diyaudio.com/forums/showthread.php?s=&threadid=95603&highlight=

Actually, the xover network is fairly simple, since the BG75's run free from ~ 600 Hz up to their rollof around 14 khz... as do the 25" neoplanars, which are good beyond 20 Khz

The midwoofers are low passed below the breakup modes, and most of the complexity is in the baffle step and notch filter for the RD 75's

Total cost per speaker ran around $800, with maybe 20 hours of work in each one.

The 25" neoplanars show up on the Seattle craigslist from time to time (they were made for Paul Allen's (Microsoft) mega-yacht) and sometimes on that auction site. I got the BG's for 1/2 price. I chose these after hearing some Genesis dipoles that used RD's

John L.

 

[lolojr1]

Update

i got one of my lines wired and hooked it up to the small bookshelf stereo in the garage for kicks, full range, with no tweeter......wow what a disappointment.

I figured it might have been the comb filtering and i was curious about what that was going to sound like anyways. it had a really big peak that seemed to be around 1-2khz and sounded about 20 db higher than the rest of the bandwidth.

Next i figured that i would get an old 3 way crossover that i had salvaged and throw a tweeter in just for fun it was the 10$ pioneer partsexpress Part Number 270-050 well needless to say i figured with the rise in efficiency of the line i would need a really sensitive tweeter how wrong i was, it made things worse.

at this point i go grab my rta and turn it on...its dead i take it apart it needs a battery (8v) custom order at 38$grrr. i get that back together and bring the line and rta to my room where my computer is hook it up to an older hitachi hma7500 amp with my computer as the source.

WHALA it sounds great with new amp and the xover in place using the line as the mid and no tweeter, i hook the tweeter back up wow it too bright have the lpad turned almost all the way down and its still to much cant tell if its just a honky horn tweeter or just to loud.

I take the tweeter out and jam out for a few hours it sounded really good just a little lacking in the top end .

so there are a few things i want to do now

rebuild the cabinet might build a sealed box not sure just yet the mounting of an oval driver is a bit of a pain so???

and i want to add a tweeter i figure there are 3 options

1: a top mount tweeter like the hivi tn-28......anyone have any opinions on this or any more of that type of tweeter or any like it,please keep in mind this is a budget and an experiment with my first real home speaker so none of the 300$ super tweeters.

2: make a small middle box for a 1 inch dome type and have an 18 driver line above and 18 below,actually saw this online in one of my many searches of linearray on google

3: get a small dome and mount it in front of the cones, kind of on a bridge over the mids