Itkixx New Upper-mid cabs. - diyAudio
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Old 21st December 2013, 09:37 AM   #1
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Default Itkixx New Upper-mid cabs.

Hi peeps. Ive pulled apart my old bass reflex cabs and im going from an Eminence Delta12a + Selenium D220ti to 5x LG 3inch drivers in an upright stacked horn to take upper mid duties off the Delta.

The Delta will be getting a pair of MT130 horns built for them to live in after this is finished.

Date required to be done is this NYE!! yes, ive short changed myself on time for sure... stupid doesnt even cover it...

so, from the start.

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this was my XO for the delta/d220. ill ask a question on it shortly.

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new layout

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depth at which the tweeter will sit in relation to the woofers.. i think im going to experience a small amount of delay between tweet and mids...

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fuzzy shot of the driver.

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the baffle and its wings

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inside the throat.

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now, my questions are such,

i have 5x 8ohm drivers. if i wire them all in parallel ill get around 1ohm. which isnt good right, even if its filtered via a passive XO ? so then the logical choice is to combine parallel/series arrangement to balance out impedance, but which way? should i run three in series/two parallel, or two pairs of parallel with the single in series??

also, will running them in offset combos affect individual driver handling at all??

third, theyre only 30w. i was hoping that if i filter them at 1.2khz @6db/oct would be sufficient for the whole 150w worth to handle a 400w amp channel that will also be drivng the Delta on the lower 1/3 of the XO.

lastly, back to the impedance, the Delta is 8ohm. my D220 is 16ohm. will it really matter much if any as to what the actual resulting impedance is on the mid combo as far as teh amp is concerned, as in, will it be the woofer that ends up providing the overal impedance as its the one drawing the power?


thanks in advance for any info you guys can share.
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Old 22nd December 2013, 04:28 PM   #2
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5x 8ohm is an awkward number to work with: unless you wire them all in parallel, or all in series, some will be working harder than others.

It'd be difficult to compensate for this: adding a series resistor means the resistor itself will soak up a lot of power, so it'll have to be big, and will probably need a heatsink.
Putting all the drivers in series will probably mean you run out of voltage swing well before your drivers get warm. In other words, you'll be clipping at very little power. Two groups, one of 3 series, one of two, would share the work most evenly, but the group with 2 drivers in will each be taking twice the power of one of the drivers in the group of 3. Those two would likely fail if the system was pushed.

I'd go steeper than 6dB/octave for crossing over - you want to make sure those little drivers encounter as little LF as possible.


What will be driving this?

I'd recommend using anything with output current limiting. You're looking at the new switching amps, or maybe something like a Crown 2400VZ.
If your amp is anything like the ones I use (big old class AB thing with very little in terms of protection), I'd be very very careful at first, and do plenty of "worst-case" experiments to see what happens when its really pushed, before using the system for gigs.

Chris

PS - a 100v line amplifier will drive the group of 5 in series without much trouble, and opens up options for active crossovers.
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Old 22nd December 2013, 11:40 PM   #3
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Thanks Chris.

ill be running on a Behringer EPQ1200 using the 5x 3inch horn as midrange in a passive three way setup. which is fed via a MiniDSP to run top box duties.

i wired them up and checked them on a multimeter, they measure a tad over 2ohm in full parallel and even at that level seem to struggle to compete with the 16ohm D220ti horn using the stock XO that came with the 3inch drivers. (tested on a 30w amp) im hoping that a bit of eq will have them sounding just that little bit sweeter.

my test rig VV lol

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i want to run a 12db/oct XO on the bass cut and probably around 600hz.

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Old 23rd December 2013, 12:45 AM   #4
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they look cool let us know how they turn out and how they sound.
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Old 23rd December 2013, 10:55 AM   #5
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The Behringer is probably intelligent enough to cope with the 2ohm load, but, as I said earlier, test, test, and test again. Make sure it won't shut down after running flat out for a few hours.
With the crossover in place, and on reasonably "normal" music (ie, not clipping sine waves in the middle of the 3"ers' band), I'd expect the amp to run out of headroom before the 3"ers burn.

Sounds like eq would be the way to get the HF in-line. Certainly better than padding with big resistors.

Bet those cabs are a lot lighter now!

Chris
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Old 23rd December 2013, 10:08 PM   #6
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Where'd the drivers come from?
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Old 28th December 2013, 10:39 AM   #7
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Hi bitSmasher, The drivers are from an LG home theater system. After reading some specs on them, theyre rated to 130w amazingly, with the amp being 130Wrms/channel. the woofers have 30w printed on them so Im fairly sure theyre not powerhouses, but I am sure that between 5 of them, hipassed at ~600hz they should be able to handle the 320w that the amp spits out with the 8ohm load of the Delta.
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Old 28th December 2013, 10:09 PM   #8
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OT , k I like your tracks on soundcloud. Alright now back to topic.
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Old 28th December 2013, 10:12 PM   #9
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Thanks TopShelf.
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Old 29th December 2013, 02:08 PM   #10
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Quote:
Originally Posted by klampykixx View Post
Hi bitSmasher, The drivers are from an LG home theater system. After reading some specs on them, theyre rated to 130w amazingly, with the amp being 130Wrms/channel. the woofers have 30w printed on them so Im fairly sure theyre not powerhouses, but I am sure that between 5 of them, hipassed at ~600hz they should be able to handle the 320w that the amp spits out with the 8ohm load of the Delta.
Yeah, they rate them at 130w/ch, but...

That's usually at 10% THD (ie, basically unlistenable), and one or two channels driven. The power supply won't stand all 5 going at once.

Driving all 5 channels at not-clipping, you're probably looking at a clean 35w/ch, which is somewhere near what each driver will stand.

I don't buy much "consumer" equipment these days - Pro stuff has specs that hold up in reality, and will stand being thrown around a bit.
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