New DIY Mid High (90deg) - AKA PM90

Re: New DIY Mid High

Bandpass low-mid with adjustable port? So, the new 10" will use this as well? :)

Iguess you could describe as 4[SUP]th[/SUP] order band-pass. The exit ports are positioned to control thevertical directivity and its tuned very high. The double 10 version may be the same, but I may make it an 6th order to get more bass, more less reflex with a small chamber to control directivity.
 
Re: New DIY Mid High

Hi all...just ordering drivers and I'm not sure if it's the 16 or 8ohm version of the BMS I'm after??
Thanks

Hi Toby, I think most guys have been going with the 16 ohm version. I did, to be able to copy Peter's IIR settings, ....and I knew from his postings that the 16ohm is fairly close without a pad.
I've heard the 16ohm version might have less audible hiss, but it seems to me you'll surely have to pad down the 8 ohm, .....and that should get you to the same hiss point....dunno though.

Are you going passive or active with the BMS?
 
Re: New DIY Mid High

Hi Toby, I think most guys have been going with the 16 ohm version. I did, to be able to copy Peter's IIR settings, ....and I knew from his postings that the 16ohm is fairly close without a pad.
I've heard the 16ohm version might have less audible hiss, but it seems to me you'll surely have to pad down the 8 ohm, .....and that should get you to the same hiss point....dunno though.

Are you going passive or active with the BMS?
Thanks Mark...I've 16ohm units ordered.
A shortage in Amps dictates that I'm gonna start out Passive and see how it sounds.
I have a 2in 8out dsp so I've the option later.
I'd be very interested in what settings folks are using, I'll be using a dbMark XCA28 processor so I'll have to adapt to suit.
I've a current plan to construct a lot of the cab in GRP.
I'm hatching an idea to make the 12" horn paths and Coax horn in a curved one piece moulding that sits in a Ply outer.
I can then make it without Grills which should look pretty special.
Watch this space.
 
Re: New DIY Mid High

Thanks Mark...I've 16ohm units ordered.
A shortage in Amps dictates that I'm gonna start out Passive and see how it sounds.
I have a 2in 8out dsp so I've the option later.
I'd be very interested in what settings folks are using, I'll be using a dbMark XCA28 processor so I'll have to adapt to suit.
I've a current plan to construct a lot of the cab in GRP.
I'm hatching an idea to make the 12" horn paths and Coax horn in a curved one piece moulding that sits in a Ply outer.
I can then make it without Grills which should look pretty special.
Watch this space.

Very interesting...good luck !
 
Excellent!

Got to try out the just completed 90 deg versions on Friday. Was a small gig so didn't get a chance to let them run but they sounded fantastic.

Sounds great Peter !

Don, glad to see the 90's running.
I'll be very interested in hearing how often you find the 90's provide ample level and coverage, vs when you find you need pairs of splayed 60's
 
Its getting very close to my build of these now, just about to order the components.

Re processing. Peter or anybody else. Do you have experience with XTA processors. IE will it be possible to get Peters Lake fir settings and somehow transfer/translate them over to an XTA processor?



Looking good van Gils
 
Its getting very close to my build of these now, just about to order the components.

Re processing. Peter or anybody else. Do you have experience with XTA processors. IE will it be possible to get Peters Lake fir settings and somehow transfer/translate them over to an XTA processor?



Looking good van Gils

Yes I have previously used XTA processors. – They do not have FIR capability, but you could adopt the IIR settings that I have published or the settings other DIY builders are using.

You must remember that my boxes / drivers maybe slightly different to some of the other boxes, accordingly the EQ needed will also be slightly different for the low section.

You may need to use this converter to get the correct settings-

http://www.google.com.au/url?sa=t&rc...CBAreqqopPmAeQ

Perhaps some people could post what they are using to help everyone (?)

Peter
 
I will say, after several different attempts at tuning the box that there are a couple of things that *must* be done to get the box to line up correctly.

The easiest thing to screw up on these are the crossovers between the different drivers. Get the timing as close as possible and live with the phrase wrap. If you don't have FIR, it's better that everything lines up with what's next to it than making each band generally start at the same time.

The coaxial drivers benefit greatly from some out of band boost to flatten the response before applying the 6.5kHz crossover between them, as well as between the HF and the 12" mids. You'll find that some small variations in the delay between the two coaxial drivers are extremely beneficial. The 9kHz region will need some love, and I find a small amount of boost around 12kHz and above can help out. You'll find a dip in response somewhere above 2.75kHz that never quite evens back on the lower coaxial component - fiddling with a couple different combinations of filters yields a good result that interacts with the VHF nicely. I don't have mine up at the moment, but Peter's from page 11 of the 60 degree thread give you the general idea. As I have the 60 degree horn, I do not know if this applies to the 90 degree horn much. I will say that I wholly disagree with Peter's choice to reverse polarity on the VHF component. I think it sounds like absolute garbage, but maybe there's some secret I don't understand.

As far as the 12" mid section goes, I have yet to come up with great settings. I do not have a place to test them where they don't have reflections from several things, and you really have to move your measurement mic around the pattern to get an idea of what the mids are *actually* doing. Mine aren't anywhere near as directional as the horn, and integrating the two patterns has been difficult. I'll be honest, I haven't had too much success yet, but getting the crossover alignment right is the difference between the box sounding meh and sounding really clean.

Oh, yeah - one more thought. I'm using an iNuke NU4-6000 and a DCX2496. The only problem here is that the iNuke has a voltage gain of above 70x and the particular DCX unit I have seems particularly noisy. With a cabinet this sensitive, I suggest you are more careful than I am in choosing your amplification and processing sources. I get very audible noise from the system at the moment, and it's all my fault (I'm cheap -sue me).
 
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Oh, yeah - one more thought. I'm using an iNuke NU4-6000 and a DCX2496. The only problem here is that the iNuke has a voltage gain of above 70x and the particular DCX unit I have seems particularly noisy.
Did you check the ribbon cable from the mainboard to the IO board in the DCX? This ribbon cable carries the audio signals with some DC voltage: they are known to have bad connectors. (Connection between cable and connector is bad.) It starts with noise/his and eventually drop outs on channels. I have 3 of these units, all with the same problem. I soldered the ribbon cable to the IO board and replaced the connector on the cable at the main board side. No issues since then...

 
I'll give my tuning experiences and try to help build on Max's comments, which i thought were very much on target.
I should start by saying for me the DIY has been as much about learning as it has been trying to get great, loud sound....so I'm perpetually starting over with tuning, as i progress with learning...


The mid section has also been the hardest for me. Mainly because as Max and Peter have pointed out, it needs to be measured reflection free, and at a distance of a least 2-3 meters IMO. I think the dipole nature of the mid needs a little distance to get timing right with the coax. (BTW, my goal in tuning is amplitude and phase traces overlying (or simply flat with FIR), in a reflection free environment. So any taste preferences after that simplify down to using system shelving filters.)

I'll attach raw measurements of my box's mid, HF, and VHF sections....in case they help.
I'm using the rcf 12's and the 60 degree horn.
Biggest eq's on my mid are cut at 380hz and boost at 140hz. I expect all our mids will vary a bit.

I've gone through several hardware platforms. First, like Max, I was using a dcx2496, but found I ran out of filters pretty quick.
Then I added in a x-32 and used the matrix outputs for xover and eq. The x-32 has 6 filters per output, but a xover filter chews up 2, so it was pretty limited too.
Then I added pld processing amps. This worked well. Only one gotcha (same as x-32), and that is processing is 48 khz. This matters in tuning the coax's two sections together. At 48khz the minimum delay time increment is 0.02ms. I thought this is surely quick enough, but at 6300khz crossover freq, 0.02ms equals 47 degrees of phase. So one click makes alot of difference in how pink noise sounds, and how phase traces align...surprisingly so.

I think maybe the difference in folks polarity settings is dependent on how crucial the minute timing is here, and whatever exact x-over freq and topologies they are using. The dcx2496 runs at 96k and this helps imo. I've used polarites this way and that depending successfully...but if the polarity/timing is wrong between HF and VHF, the coax sounds like it's spitting.

Last and current platform is minidsp, the 4x8 DA8, with FIR capability. I'm going to sound like an advertisement, but this $350 unit has been one of my best all time learning investments. I've learned that the driver by driver tuning eq we would normally do without FIR (IIR) stays non-FIR, because when you fix magnitude with IIR, phase gets fixed too.
Then IMO the real value of FIR after that IIR tuning is accomplished is then threefold.
First, the phase wrap that x-over filters bring goes away.
Second, with that gone, it becomes very easy to get smooth amplitude and flat phase matching throughout x-over,...
and third, the IIR eqs first used can be embedded into the FIR file which means you can have as many eqs as you want and all in one package..
Both Miichael's FirDesigner and rePhase work super...
​​​​​​​Hope this helps...Mark
 

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Hi all,

I believe a friend is having four of the 60 degree version built currently to go with his all dark stained reggae roots sound - his aim is a much more HiFi sound than the traditional reggae 'hi fi' so they seemed like a great fit!

Anyway, when they're ready, they're going to be run with Powersoft K or X series DSP amps with all the FIR and Raised Cosine goodness that brings. And well, I want to use Peter's FIR as a starting point but since I also do work for a university with a full anechoic chamber and a FourAudio ELF system that happen to owe me some favours, I could maybe get some EASE GLL and CLF data generated for the box once filters are set. I can likely only wangle a single day when it's quiet though so it may be worth trying to keep in touch and get some input before and perhaps during the work if people think that would be of interest?


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