A padawan needs guidance here

Madmike2

Member
2005-04-24 11:55 pm
Toronto
HI again. I just had another idea. Feel free to rip this apart. Keep in mind that i will have active EQ and 6 channels of amplification. Ok what i propose is and correct anything i say wrong i can go back and read all the data again till i understand it exquisitly. here is a cheesy picture to clarify my written description.

http://i4.photobucket.com/albums/y121/madmike2/Basic.jpg

i want to take Surgical packing foam, it comes in a grayish black colour and flat sheets of 5/8's thick and sandwich it. Front baffle will be 1/2 inch white pine and the rear support and baffle will be 1 inch mdf that i have. each panel will be 4 x 8 inch woofers wired series paralell to a single channel. In the middle of these sitting side by side will be a 4 inch mid and cd5 fountek ribbon tweeter either wired together to one channel with a simple 12 db crossover since there will be an active x-over removing 400 Hz and lower. Or i can run the tweet on a channel the mid on a channel and the 4 x 8 array on the 100 watt channel with the Dbx doing crossover duty. The front baffle will be in the range of 90 % decoupled from rear as i will use 2.5 inch black mushroom bolts and polyurethane donuts on the back side with wingnuts to cinch the speakers to the front baffle. Almost all the transmission of energy that does make it to the back will be through the poly as the medical foam is CDC certified for vibration absorbtion.

So from what i understood part of the problem with an open baffle IS the baffle. Will taking its effects out or shrinking its footprint in the reproduction picture help ?
Just so you know i just backspaced a whole freaking book back to here, just to ask it in a way i SHOULD have asked it. WIll this design affect or lesson the baffle effect in this design assuming that this array would be valid? Or will it just destroy the point of the open baffle.

I will be reading SL page while i wait for the flaming to begin :)

Michael
 

adason

Member
Paid Member
2004-11-10 8:31 pm
Maryland
how about this arrangement /use any amount of woofers, i just did not wanted to redraw whole pic/
that should reduce the hight considerably
 

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well in the above situation there will be some source shifting continually due to different horizontal positions,how bad,I duno.

Id go vertical if possible. Why 4 x 8"s?Wont 2 do?

Bear in mind that the 8"s if reproducing the same frequency range will comb filter when the wavelength approaches the driver to driver spacing[midrange]
 
What drivers?

Nothing wrong with the design. MJKs Focal TLs worked better with side-by-side driver mounting -- showing that conventional wisdom always has to be considered with a grain of salt.

The wider the baffle the lower the bass.... as drawn you will need lots of EQ to get any bass, and 4 8s probably will run out of excursion... making the baffle wider means you won't have to work them as hard.

dave
 
Hi Dave, i just talked to you in the other forum :) Man i am a little tipsy right now on a brilliant california red.

The current dilemma floating in my head purculating its math around is a series of SIX 6.5 inch Vifa's LCY tweeter 6 inches north of center on a 19.5 in wide baffle 54 inches tall.

I have EQ and multi amps covered to play with i am just trying to imagine the sound. Its a lot of money for me. I am the cheapest guy around unless it involves something that entertains me :D
 
On a side note, you are something of a TL guru. How stupid would a MtM 10 - LCY110 - 10 alignment be. Hell i might not even need to go with 2 10's. SIngle 10 and the LCY . its Fs is like 1100 and the Peerless 10 starts falling apart at 1800 there abouts.

I did like the few TL's i have heard they all sound small though.


I am going to stop talking till i SOber up a bit. Reading i will continue to do. No more talking though.
 
Madmike2 said:
The current dilemma floating in my head purculating its math around is a series of SIX 6.5 inch Vifa's LCY tweeter 6 inches north of center on a 19.5 in wide baffle 54 inches tall.

A baffle that wide is not going to go really low, and the 6 165mm drivers are not going to have enuff volume displacement to compensate much. What you might consider here is an MTM open baffle mid-tweeter (XOed just above where the baffle starts to roll off naturally) coupled to a box with the other 4 midwoofers in it.

I got a box of 20 PSB 165mm drivers OEMed for PSB and have been noodling for sometime on how to best use them, and an arrangement similar to what i suggested is where i've gotten too (i actually have 1 pair of the midrange version of the P13 to use as a mid, and i'll use as many of the larger woofers as i can find in the bottom -- probably 4 or 6/side)

dave
 
jdybnis said:
What order crossover are you using on that tweeter to cross at 1k?

Dynaco used a 1st order XO... and on the A50 actually put a low pass on the woofer.

below is the impedance curve of the tweeter & the tweeter + XO (with all 5 level settings)

dave
 

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planet10 said:
Big budget those. I think if madmike is really interested in being frugal he should forget about those....

I'll retract that... the e-speakers site is one of those poorly written ones that blows up in my primary browser... when i clicked LCY i got to a page with ribbons costing 1000s of dollars.

Went in again with the backup and see these are 200 USD/each ... still pricey thou. The Aurum Cantus G2si is more approachable (& ironically for tweeter use the smaller/less expensive ribbons are actually better suited to the job)

dave
 
See thats what i wanted to hear Dave :) go cheaper.

I just sat down and did a rough recalculation of the lower frequency wave propogation off a resonant baffle arrangement from the 6.5 inch and i get nearly 35 inches wide for the 6.5 inch. Its probably not right but i am assuming a set frequency times the speed of sound times the drivers SD for a length. Then picturing a 'launch' off the baffle and working on TL theory except i am not aiming for 1/4 i am aiming for 1/16. My brain hurts. I need something to hit.

Anyway, the narrow baffle cant launch low frequency waves so they just wrap around the baffle and meet the back waves for NF cancelation. Is this correct? Is that why i need a wider baffle ?

I got the money there to spend. Tell me what you think would work in detail and ill do it. Think of it as your experiment that you dont have to pay for :D .... BIg sound great sound stage 1300 dollars available and your own personal lab assistant who comes with a side of Woodworker downstairs.