New DIY Mid High (90deg) - AKA PM90

First time really listening using the basic IIR filters Peter posted here

Sounds wonderful. Love the clarity on the high end and how the further away you get, the only thing that changes is volume, stays very sharp.

I'm on the very beginning of the learning curve when it comes to processing, so looking forward to making them sound even better.

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@Peter Morris - I pm'ed you about your latest FIR filters, but here is probably better. I read through this thread and the 60 degree thread again, but the only filters I am seeing are these.

1. Sounds like there are newer ones? Are they posted somewhere and I'm missing it?

2. For someone new like me, where should I be getting started when it comes to doing my own measurements? This thread has been super informative, enjoying learning from you all.
 
Leon JEDDi Lawrence said:
What are you housing for processing and amplification?
Click to expand...

Q-sys 110f to QSC cxd4.5Q network amps + speakerpower plate amps for my subs.

The q-sys can do full fir via coefficient csv / wav import.

It's pretty cool software, you build out your routing first, dropping in all the items you'd like into your process, then take that design and set it up.

HhDvad3.png

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I tried to do copying Peter's settings here, using RePhase to export the FIR crossovers and the raised cosine filters. Haven't gotten a chance to listen yet and they are probably wrong.

Also still trying to figure out how to phase align the subs.

I've been bugging Peter for help, but any other advice would be wonderful. Learning a lot!
 
Ti Liptak said:
Q-sys 110f to QSC cxd4.5Q network amps + speakerpower plate amps for my subs.

The q-sys can do full fir via coefficient csv / wav import.

It's pretty cool software, you build out your routing first, dropping in all the items you'd like into your process, then take that design and set it up.



I tried to do copying Peter's settings here, using RePhase to export the FIR crossovers and the raised cosine filters. Haven't gotten a chance to listen yet and they are probably wrong.

Also still trying to figure out how to phase align the subs.

I've been bugging Peter for help, but any other advice would be wonderful. Learning a lot!
Click to expand...


Hi Ti, Very nice work.

The q-sys looks very capable. How many taps, at what sample rates, can it handle?

One trick I've learned for aligning subs, when using linear-phase crossovers, is to find the sub's delay with everything in play other than the FIR filter. This usually gives a dead-on repeatable time. Then turn the FIR filter on, which has a known # of samples delay, add that delay to the previous measurement, and you get a specific delay that ties linear-phase together pretty perfectly. Delay finder times will group very closely around that total time, the more linear the phase of the sub and main through the crossover region, the tighter the grouping will be.

Of course, if you are using IIR between sub and the DIY you will have to go through the 'phase trace overlay method'. Which can be a little confusing at start because of inconsistent delay time readings for the sub.

I'd recommend to anyone who has the FIR capability to first learn to tie things together with linear-phase, because it becomes trivially easy with a little experience. It is also good preliminary training for moving to IIR and the phase trace overlay method , for when the FIR latency is too much for the application..

FWIW :)
 
Mark Wilkinson said:
Hi Ti, Very nice work.

The q-sys looks very capable. How many taps, at what sample rates, can it handle?

One trick I've learned for aligning subs, when using linear-phase crossovers, is to find the sub's delay with everything in play other than the FIR filter. This usually gives a dead-on repeatable time. Then turn the FIR filter on, which has a known # of samples delay, add that delay to the previous measurement, and you get a specific delay that ties linear-phase together pretty perfectly. Delay finder times will group very closely around that total time, the more linear the phase of the sub and main through the crossover region, the tighter the grouping will be.

Of course, if you are using IIR between sub and the DIY you will have to go through the 'phase trace overlay method'. Which can be a little confusing at start because of inconsistent delay time readings for the sub.

I'd recommend to anyone who has the FIR capability to first learn to tie things together with linear-phase, because it becomes trivially easy with a little experience. It is also good preliminary training for moving to IIR and the phase trace overlay method , for when the FIR latency is too much for the application..

FWIW :)
Click to expand...

Thanks Mark!

4096 taps @ 48khz.

I've watched some videos on the "phase trace overlay method". Went ahead and downloaded a trial of Smaart and can use the Q-sys as a USB soundcard. I've gotten that working, but haven't run measurements yet. Hopefully this evening.

With the mid hi's, Peter kindly sent over his latest FIR settings and I directly copied them from the Lake Controller. His approach of using FIR linear-phase filters for all the crossovers except the sub make sense to me. I will try to replicate that.

I'll post some measurements shortly and perhaps you can steer me in the right direction.

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As a promise to this thread, I'll also post some additional drawings of the mid-hi. Max get's most of the credit, since I will use his as a baseline, but with some modifications now that I've actually built two pairs.

Will do two versions, one for people building without a CNC with exact measurements of each part of the horn path so you can easily trace it out + part dimensions + cutsheets.

Then a second version for CNC users that you should be able to directly import into your CAM tool and define your toolpaths. Will color code it so it's super easy, EG: Red paths = outside throughcut ---- Green paths = 6mm deep pocket etc.
 
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Hi Ti,

What I have been doing for the sub crossover is to use an IIR to keep the latency acceptable for FOH application. I think typically you can get away with 10 ms (or more) as the loud backline instruments are usually at least this distance in time behind the FOH speakers.

I then use the ‘phase trace overlay method' to match the two phase traces often adding and additional all-pass filter to the sub to get every thing to match perfectly.

When adding all-pass filters to various pass bands you have be mindful of the resulting signal polarity, sometimes you may end up flipping it to get every thing to line up correctly.
 
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Peter Morris said:
Hi Jaroslav,

They look great, love your build quality - I hope you have great success with these boxes.

Best Regards

Peter
Click to expand...

Thank you for the positive feedback I've been using boxes since June 2018 and the listeners and musicians are happy and amazed how it is possible that such a small box so nicely and so loudly plays :-)
Once again thanks to Peter for this design.
Jarda Mike
 
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Hi peter, what do you think abou adding a brace to the back of the baffle? I calculate it will reduce the area effecting compression ratio(s2 or what ever it is) by about 4 percent..... The reason for this brace is the thinned down area of the baffle has a bit of flex in it that didnt seem ideal to me.baffle brace.jpg
 
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In the original design, there was a brace there. It should make nearly no difference within the driver's pass-band, as it's cross section and length are smaller than 1/2 wavelength at even 700Hz
 
Hello Peter and forum. I'm wondering if I should go for it. I'm a noobie, only have a couple of cabinets behind me but I'm kind of a quick learner and not harmfully bad at woodworking. I have 4 tham15s loaded with 15ps100(700w aes), and I am doing forest raves. This means restricted powerconsumption. I really want to impress the crowd with something more high end this summer, and then I came over this amazing build. I have a couple of questions.

1. How big of a difference are we talking about with the passive cross over? what characteristics can you notice in sound quality? Will it still turn heads?

2. Can I do without learning smaart or similar?

3. Will the BMS 4594ND work well enoug (without the phase plug)?

4. And the make or break question: Will I be able to do adequate IIR signal processing with something like a miniDSP2x4 or 2x4HD?

Best regards

Kristoffer
 
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As Janson said, yes its fine with a passive crossover for the HF/VHF and yes you can run it with a normal IIR digital crossover.

Perhaps some others who have the boxes built to the fineal design using standard processors like the DBX260 etc. can share their setting with you. For the settings to be compatible you will need to be using the same box dimensions and components.

Using a 3 way Lake crossover with FIR fliters, the BMS 4594ndHE just takes it to the next level, studio monitor quality, but is a lot of $$$
 
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