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carlosdelondres View Drop Down
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    Posted: 06 January 2019 at 12:10pm
I got fed up with not having a system I could take pretty much anywhere, so put this together with drivers I had lying around.

Subs are dual 5" PPSL 6th order/reflex hybrid type thing (not really sure tbh). Mid tops are dual 3" plus dome tweeter - I wanted the whole thing to look a bit like a scaled down big rig...



and with grilles and amp box:



Amps and DSP are all Sure bits, a 4x100w amp for the mid tops, 2x400w for the subs (realistically more like 4x50 and 2x200). Bluetooth and line in, volume control and separate volume for the bass amp and 2 ADAU1701 handling crossover, delay, limiting.

Runs for about 4 hours at full pelt off a 31 Ah 16.6V li-ion battery, all weekend at more social levels.

Don't have a calibrated spl meter to get the sensitivity, but on paper the pair of subs top out at around 115dB at xmax. Gets loud enough for a campsite or BBQ for sure :)

Frequency response could be better but sounds quite nice - the subs have a really tight kick and go surprisingly low, mid tops are quite enjoyable as well.

A few build pics and graphs below
















unfiltered response:




crossed response:

combined response:

still fiddling with the DSP, the big peak in the sub response above 200Hz is the plenum chamber I think - not sure what the dip at 5.5kHz is but it's right in the middle of the mid/top crossover unfortunately...

Would welcome any input!

Cheers...


Edited by carlosdelondres - 06 January 2019 at 12:15pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 06 January 2019 at 1:42pm
Very neat. The peak at 200Hz obviously doesn´t matter if you cross over below. The dip is more difficult. It looks like the speaker rolls off very rapidly from 4kHz and the tweeter doesn´t reach there either, so apart from trying a different tweeter, or 3", it will be down to eq.

But if it sounds ok to you, don´t worry about it - I´ve seen worse on some commercial cabs!  Dead


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Post Options Post Options   Thanks (0) Thanks(0)   Quote concept-10 Quote  Post ReplyReply Direct Link To This Post Posted: 06 January 2019 at 3:11pm
I like this a lot, nice job.
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carlosdelondres View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote carlosdelondres Quote  Post ReplyReply Direct Link To This Post Posted: 06 January 2019 at 8:24pm
Originally posted by Earplug Earplug wrote:

Very neat. The peak at 200Hz obviously doesn´t matter if you cross over below. The dip is more difficult. It looks like the speaker rolls off very rapidly from 4kHz and the tweeter doesn´t reach there either, so apart from trying a different tweeter, or 3", it will be down to eq.

But if it sounds ok to you, don´t worry about it - I´ve seen worse on some commercial cabs!  Dead




Thanks very much - the 200Hz peak is somewhat audible, but getting the mid tops to go lower isn't really possible. Central plenum needs to be shallower to push it higher, and the inner port lengthened to compensate (I think)...live and learn.

The 5.5kHz drop off is more mysterious - the 3" drivers are monacor sph30x and the tweeter is a Dayton ND20, both should be farily flat through the range used. With the 3" I guess they might be at the uppper range in which they will couple, the tweeter, dunno - something to do with the baffle size/layout...? Just wanted to keep the frontal area low and the drivers as closely spaced as possible...
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carlosdelondres View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote carlosdelondres Quote  Post ReplyReply Direct Link To This Post Posted: 06 January 2019 at 8:27pm
Originally posted by concept-10 concept-10 wrote:

I like this a lot, nice job.


Cheers :)

The mid tops are wedges so the're reasonably audible when at knee height. Subs are 2 midtops long and one high, so can be stacked a few ways...



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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 07 January 2019 at 10:53am
Originally posted by carlosdelondres carlosdelondres wrote:

Originally posted by Earplug Earplug wrote:

Very neat. The peak at 200Hz obviously doesn´t matter if you cross over below. The dip is more difficult. It looks like the speaker rolls off very rapidly from 4kHz and the tweeter doesn´t reach there either, so apart from trying a different tweeter, or 3", it will be down to eq.

But if it sounds ok to you, don´t worry about it - I´ve seen worse on some commercial cabs!  Dead




Thanks very much - the 200Hz peak is somewhat audible, but getting the mid tops to go lower isn't really possible. Central plenum needs to be shallower to push it higher, and the inner port lengthened to compensate (I think)...live and learn.

The 5.5kHz drop off is more mysterious - the 3" drivers are monacor sph30x and the tweeter is a Dayton ND20, both should be farily flat through the range used. With the 3" I guess they might be at the uppper range in which they will couple, the tweeter, dunno - something to do with the baffle size/layout...? Just wanted to keep the frontal area low and the drivers as closely spaced as possible...



Ok - a bit of a long-shot, but have you tried flipping the polarity of the tweeter? Might help.



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carlosdelondres View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote carlosdelondres Quote  Post ReplyReply Direct Link To This Post Posted: 07 January 2019 at 11:21am
Not tried that - I thought because the dip is there on the standalone plots, and there is less of a dip with the combined response, there must be summation through the crossover region, so polarity flip wouldn't help...? Will give it a try, though will have to wait til evenings are a bit lighter!

Anything in the deisgn itself that stands out as potential cause of the issue would you say?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 07 January 2019 at 12:22pm
It might seem counter intuitive but there's a chance you've got a diffraction issue by recessing the HF driver, or a reflection coming back off the protruding box sides for mounting the grill. Have you tried measuring the HF driver in free air?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote carlosdelondres Quote  Post ReplyReply Direct Link To This Post Posted: 07 January 2019 at 12:46pm
Hmm, I don't have a free space measurement, but did do some indoor near field measurements - this was at 2cm. No dip...

*edit* with 1/12 smoothing...but even with 1/24 still no dip at 5.5kHz...



Edited by carlosdelondres - 07 January 2019 at 12:48pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 07 January 2019 at 1:45pm
Then it definitely looks like some phase/group delay issue around the crossover point. Try what I said and see if it makes any difference. Can you change the crossover points, etc. on the ADAU1701 you have?


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carlosdelondres View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote carlosdelondres Quote  Post ReplyReply Direct Link To This Post Posted: 07 January 2019 at 1:50pm
Yep, all fully programmable in Sigma Studio. Crossovers are all LR 24, at 40, 135 and 5.5 in the plots with filters on above. Though the no filter mid and top plots are suspiciously similar to the filtered ones so I may have failed to disable them there. Reprogramming the DSP is a bit of a fiddle!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 07 January 2019 at 1:53pm
Ok - LR24 should give the best phase response already. Try what I said and see what happens.  Smile


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