what can i make out of these 2 pairs of drivers?? - diyAudio
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Old 17th April 2004, 06:03 AM   #1
sqlkev is offline sqlkev  United States
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Default what can i make out of these 2 pairs of drivers??

Hi guys,
I'm very new to this speaking building business..
my background is only a few years of experience in car audio and most of my systems were built with an active xover..
enclosure building experience was also limited to sub boxes..
ive only tried to build a few mid enclosures for the mids and tweets...but all were based on manufacturers specs...
I'd like to build my first real and cheap "DIY" (with the help of u guys ) home towers..

right now i have a pair of dayton 1 1/8 silk dome tweeters
(http://www.partsexpress.com/pe/pshow...=275-070&DID=7)

i also have a pair of vifa 4.5" mids
(http://www.partsexpress.com/pe/pshow...number=299-495)

what would you recommend me to make out of those drivers?
I'm willing to buy an extra set of midbass to add into the mix for woofer-mid-tweet setup..but not sure

*note*
-keep in mind that i dont have any measuring equipments..so i cant measure the FRs of my own drivers...i would have to go with the given specs..
-im not a great carpenter by any means...but i can make nonleaking enclosures to specs..

any suggestions and comments are welcomed
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Old 17th April 2004, 09:21 AM   #2
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small sealed box...I'm thinking NHT SuperZero here.

In fact those premade boxes they sell at PartsExpress may be just the ticket for you.

with that 0.25CuFt box you could probably get down to about 150Hz or so....true SuperZero style!
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Old 17th April 2004, 11:52 AM   #3
sreten is offline sreten  United Kingdom
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http://www.speakerbuilder.net/web_files/default.htm

I suggest you ditch the very difficult to use Vifa /
JBL units and build one of the designs here.

The D3 can easily be converted into a "Tower" design.

sreten.
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Old 17th April 2004, 02:57 PM   #4
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The only difficulty I can see is the difference in level from the bass to the upper end, the 3/4 dB shelf.

As sreten has stated this is not an easy driver to work with and he is correct. I dont even think id bother trying to work with it cause it'll be such a pain to get right. I dont even know of a passive circuit availble to actually sort it out.

The only thing I can think of is that this is a custom driver for JBL, now they may have specified that kind of response.

The only reason I can think to do it like that is for baffle step reasons. The design they could have been working on could have needed 3/4 dB BSC and they knew how big the front baffle was going to be so got vifa to do that to the freq response. Its not a perfect explanation because the 3/4dB transition of the driver does not exactly mimick baffle step.

Now an active crossover thats a different matter entirely and if you are comfortable with them and have two stereo amps at your disposal the vifas are entirely usable. See pic below.

Using the active filters specified in the top two diagrams you will ahceive the third summed freqeuncy response. When the polarity is reversed you get a nice deep null showing accurate phase.

HOWEVER this is only half way there, it includes no offset whatsoever for the drivers in the Z axis, I included 150mm for the Y and zero for the X. Also this includes no baffle step compensation what so ever. I couldnt find a way of importing the woofers data into MLS to add baffle step.

Either way there you go.
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Old 17th April 2004, 03:00 PM   #5
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Oh yeah and I forgot to mention, obviously the xover freq is at 3.5khz and they are both 4th order linkwitz slopes acoustic. The tweeter will require a 2dB boost.
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Old 17th April 2004, 03:12 PM   #6
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I had a thought doesnt matter what it is, but add this filter to the mid/bass section and it will compensate fully for 6dB baffle step using a baffle width of 16cm.

If you are dead set on using the vifa and dayton and can use active xovers then you could do a lot worse then building my xover with a box of 16cm front width. It wont be perfect but it wont be that bad either.
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Old 17th April 2004, 03:17 PM   #7
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DOH! I cut off the component values!
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Old 17th April 2004, 03:20 PM   #8
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****** I also did it with the first filters Oh how daft i feel

OK...... didnt realise that would get **^%&$'ed
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Old 17th April 2004, 07:43 PM   #9
sqlkev is offline sqlkev  United States
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hybrid fourdoor..
wow...those tiny boxes are expensive
i think i can live with my plain mdf boxes since im just building this as my first project..
thanks for the link though

sreten..
the D3 looks promising..ill definitely look more into it

5th element..
my hats off to you sir..
ure such a great help...but i think baffle compensation and that many parts in xover kinda discourage me a bit...
due to its complexity and cost...(more like the cost...im willing to learn)
i dont really understand the part where u say its hard to work with though..
can u elaborate that please?
is it the midrange problem that wont blend with the silk tweeter??

i think i may just scratch this project and start with another..
do you have anything to recommend??
i could go either way...a huge tower in the living room..
or one of those horns with only 1 driver...

i really appreciate you guys helping me....thanks
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Old 17th April 2004, 11:37 PM   #10
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No problems we are all here to help

OK well the usual goal for a loudspeaker is to get a flat frequency response. The flatter the frequency response of the drivers in the first place makes it much easier to design a crossover for them especially if they are passive crossovers. With active crossovers you can do alot more of response shaping, mainly things with gain. If for instance you had a peak in the response you could use a notch filter to remove this peak. If there was a dip however there is nothing you can do with a passive crossover because it has no gain, ie it cannot apply any more watts at the dip to boost it. But an active crossover can, opamps are the heart of active crossovers and as you probably know are little amplifiers, so set up correctly can be used to apply some gain at the dip to boost it.

Now with the driver you have the fact that is has that transition of about 4dB from 700hz to 1250hz make it hard to work with. With a passive crossover there is nothing you can do to boost the bit from 1250hz+ to meet the bit below 700hz so its a rather tricky driver to work with.

The active crossover I suggest wouldnt be that diffucult to build if you have some experience with electronics. It may look as if there is alot there initially but its only a few resistors and capacitors, which are really cheap too.

With regards to baffle step this is a natural phenomenon that cannot really be avoided and ignor it at your own peril!

Basically what happens is due to the increasing wavelength of sound as it lowers in frequency, at high frequencies, because the wave length is short in comparison to the box, all the sound produced by the drivers radiates out from the front of the box and reaches the listener. But as the frequency lowers and the wavelength becomes around the same as the box size the sound no longer just radiates forwards of the box to the listener, but some "creeps" deffracts around the sides of the box, this causes a gradual drop of 6dB's from when baffle step (as it is known) begins and ends. See pic for example of what happens to a driver mounted in a box with a width of 16cm.
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