60 Degree DIY Mid Hi - AKA PM60

[Peter Morris]

Re: 60 Degree DIY Mid Hi

Hi & thank you Art !

Hi Peter, I've been reading about processing variations in various articles/threads, and really wonder if there is any substitute for learning to measure and know what is being measured.
I'm thinking truly learning dual FFT is what I need more than any particular processor..
That said, could you comment on how well you think the testing setup works, that i tried to elaborate on my most recent post to Don? See any issues?
I'll also post complete IIR setting being used on the 60 deg, just for double check if you have time ...
Thank ya Peter !

A lot of the people I see using Smaart don’t really understand exactly what they are measuring.

If you use an FFT with a time window that’s big enough to capture the low frequencies you are usually capturing other stuff you don’t want that mucks up your measurement.

There are basically two solutions – measure it in an anechoic chamber – or measure it a long way away from any boundary’s (12ft in the air or more) where the mic is relatively close (6 ft) to the speaker.

Note: this is a mid-Hi box operating from 100Hz up (100Hz wave length = 11.15ft, 10ms per cycle). For low frequency you can place the mic on the ground.

As a practical solution your setup with the ground sloping away looks great.

 

[Peter Morris]

Re: 60 Degree DIY Mid Hi

Man, I would look into the horn in that 3-7kHz region. Would you mind sending me the impulse responses, and the sampling rate? I'd be pretty interested in taking a look at them.

Hi Mark - you were absolutely correct! Thank you, not many people would have picked that up!

I ended up gluing some rubber to the horn to dampen some minor resonances; it improved the impulse response and directivity, and to my ear it sounds smoother, and the sound field is even more detailed.

I will post some plots & pictures when have a couple of minutes spare.

 

[Don J Davis]

Re: 60 Degree DIY Mid Hi

Hi Mark - you were absolutely correct! Thank you, not many people would have picked that up!

I ended up gluing some rubber to the horn to dampen some minor resonances; it improved the impulse response and directivity, and to my ear it sounds smoother, and the sound field is even more detailed.

I will post some plots & pictures when have a couple of minutes spare.

Peter, Mark D.
So if I'm understanding this correctly, the deviations in the mag response on the off axis measurements in this small clip of Peter's plot are what you guys are talking about?
I'm trying to learn more of how to understand what I'm seeing in traces. I don't have the chops to know what caused those, what would have you expected there, a smoother more linear tapering off in the HF range?
I see the bump in the coherence trace as well. This was indicating reflections in the HF horn?
To me the phase trace didn't see to be telling me anything there but again I'm not sure.
Looking for a learning moment here, thanks for your patience!

Don

 

[Mark DeArman]

Re: 60 Degree DIY Mid Hi

So if I'm understanding this correctly, the deviations in the mag response on the off axis measurements in this small clip of Peter's plot are what you guys are talking about?

Yes sir.

I'm trying to learn more of how to understand what I'm seeing in traces.. ...what would have you expected there, a smoother more linear tapering off in the HF range?

Yep, and that was an especially broad bandwidth. I see this a lot of prototype products which come into my shop.

I see the bump in the coherence trace as well. This was indicating reflections in the HF horn?

Unknown, I don't use that type of measurement system, so I don't have a lot of experience. I know that random noise will tend to average out of the measurement, and that signals correlated with stimulus which are not part of the ideal LTI system model will reduce the coherence. I was really asking questions, trying to learn myself.

To me the phase trace didn't see to be telling me anything there but again I'm not sure.
Looking for a learning moment here, thanks for your patience!

It wasn't really telling me anything either, except that there was a problem. Why I thought it would be interesting to measure, is that I thought it would be neat to see in the T-F plane, what was going on with those frequencies. Whether it was problem, with modes in the horn throat, constricting the throat, and widening the pattern, the horn its self resonating, or reflections. It sounds like Peter did some experimenting and is on to something.

 

[Peter Morris]

Re: 60 Degree DIY Mid Hi

Hi Mark - you were absolutely correct! Thank you, not many people would have picked that up!

I ended up gluing some rubber to the horn to dampen some minor resonances; it improved the impulse response and directivity, and to my ear it sounds smoother, and the sound field is even more detailed.

I will post some plots & pictures when have a couple of minutes spare.

Here are some plots - unfortunately it was raining, so they were done inside my workshop - as a result there are a few extra lumps and bumps that are not normally there. (ignore the red plot)

The angles are my best guess ... +/- 5 or more degrees.

Before I modified the horn, there was a second small spike in the impulse response plot. Forgot to save it :-(

 

[Mark DeArman]

Re: 60 Degree DIY Mid Hi

Peter, I wouldn't be to worried about your loopback measurement there. Any good measurement system which is band-limited, will produce a loopback impulse response which looks like that of an FIR filter (symmetric and asymptotically decreasing side-lobes). That is because it is band-limited and has some finite delay.

On some systems I've used, this will be the IR of the envelope function applied to the stimulus. Some systems, do their delay correction by just doing a circular move on the IR back to zero.

The only time I calibrate that out in my system, is if I need to do absolute delay (phase) measurements. Once calibrated, you end up with a loopback response which looks more like you would expect, flat line with one sample at unity ( ie. exact delta function ). If you don't care about really low frequency, reaally high frequency (near Fs/2), or absolute group delay then it doesn't really matter.

Mark.

 

[Peter Morris]

Re: 60 Degree DIY Mid Hi

Peter, I wouldn't be to worried about your loopback measurement there. Any good measurement system which is band-limited, will produce a loopback impulse response which looks like that of an FIR filter (symmetric and asymptotically decreasing side-lobes). That is because it is band-limited and has some finite delay.

On some systems I've used, this will be the IR of the envelope function applied to the stimulus. Some systems, do their delay correction by just doing a circular move on the IR back to zero.

The only time I calibrate that out in my system, is if I need to do absolute delay (phase) measurements. Once calibrated, you end up with a loopback response which looks more like you would expect, flat line with one sample at unity ( ie. exact delta function ). If you don't care about really low frequency, really high frequency (near Fs/2), or absolute group delay then it doesn't really matter.

Mark.

Thanks Mark,

I wasn’t worried – I did a quick check of the loop back impulse just to make sure the ringing I was seeing in the impulse measurement was in fact being mostly being generated by the FIR filters within the measurement system. It is a textbook response. The “need a better system” was just a throwaway line ~~:smile:

The VHF section of the HF driver is extremely efficiency. To do that it has a very high resonate frequency. I was checking to make sure there were no issues hidden in the measurement.

If you make allowance for measurement systems pre and post ringing, the impulse response of this PA speaker is quite stunning.


Thanks again.

 

[Don J Davis]

Re: 60 Degree DIY Mid Hi

I was really asking questions, trying to learn myself.

Thanks for your answers Mark. I'm always interested in learning from guys with a lot more experience than me.

 

[Peter Morris]

Re: 60 Degree DIY Mid Hi

Update - I have done a bit more work with settings. It’s difficult with Smaart / Systune to determine good settings; you really need something better, and a controlled environment.

To determine the best time alignment and correct gain between the LF and MF you need to be about 4m from the box. At this distance reflections start to impact on the measurement if your window time is long enough for the low frequency measurement.

I have used this point, (4m back and 3 to 4m high) to set the gain and time alignment, but something a little closer to adjust the PEQ, typically about 2m. Even then I’m not 100% happy with what I was measuring … so you still need to use your ears.

Last week I did a quick comparison out against a large world class, state of the art Commercial Cinema 4-Way THX system (no X curve applied) which is manufactured locally and sold worldwide including into the USA.

After a little bit of tweaking with the help of the factories engineers, the DIY’s compared very well, although my subs did not go quite as low. As a result it’s planned to do a shootout as part of a local AES meeting in front of all the golden ears. Wish me luck 

 

[Neale Watson]

Re: 60 Degree DIY Mid Hi

Last week I did a quick comparison out against a large world class, state of the art Commercial Cinema 4-Way THX system (no X curve applied) which is manufactured locally and sold worldwide including into the USA.

Peter,

I'm guessing who this manufacturer is ... looking at the physical size of their large 4-way, I'm curious how they manage achieving the perception of a 'point-source'? Also, there's little info in their specs re frequency response accuracy, filtering approach, crossover management and phase alignment. Obviously such a business has IP to protect, but are you able to tell us any more about their approach? I'm interested in the synergies / learnings between the two different markets.

Neale

 

[Ivan Beaver]

Re: 60 Degree DIY Mid Hi

Update - I have done a bit more work with settings. It’s difficult with Smaart / Systune to determine good settings; you really need something better, and a controlled environment.

To determine the best time alignment and correct gain between the LF and MF you need to be about 4m from the box. At this distance reflections start to impact on the measurement if your window time is long enough for the low frequency measurement.

I have used this point, (4m back and 3 to 4m high) to set the gain and time alignment, but something a little closer to adjust the PEQ, typically about 2m. Even then I’m not 100% happy with what I was measuring … so you still need to use your ears.



Yeah-that is part of the problem with loudspeakers. Not only determining proper settings, but providing accurate data for specs.

What happens up close can be different than even a few M away-due to the physical size of the device.

The "correct" answers (and even then are not 100% correct), are a combination of several different mic positions, and "balancing" what our ears hear and what the mic reads.

And as one "digs deeper" it should be quickly realized that there are NO simple answers-especially for multiple listening/mic positions

 

[Peter Morris]

Re: 60 Degree DIY Mid Hi

Peter,

I'm guessing who this manufacturer is ... looking at the physical size of their large 4-way, I'm curious how they manage achieving the perception of a 'point-source'? Also, there's little info in their specs re frequency response accuracy, filtering approach, crossover management and phase alignment. Obviously such a business has IP to protect, but are you able to tell us any more about their approach? I'm interested in the synergies / learnings between the two different markets.

Neale

As I understand they use standard 4th order LR filters. The system is 4 way with all the transducers operating in their piston range like the DIY. They design their own horns and there are patents and PhD’s associated with their horns. I'm sure the crossovers, time & phase alignment etc. are as good as it gets.

I have tested one of their horns and I just wish it would fit into the DIY.

The 4 way design sounds spectacular and has a great stereo image. If you have been to a cinema in Australia you would have heard one, but unfortunately shooting through a screen with the X curve applied

 

[David Chrapla]

Re: 60 Degree DIY Mid Hi

Peter when will the shootout happen?

Curious if the Othorns would help on in the sub department. I know you have some spare 21's laying around.

 

[Peter Morris]

Re: 60 Degree DIY Mid Hi

Peter when will the shootout happen?

Curious if the Othorns would help on in the sub department. I know you have some spare 21's laying around.

Its on the 15-9-2015. I think my subs will be Ok, but thank you very much for the offer, they are designed for music as apposed to special effects (movies) so they don't go as low as a cinema sub. Luckily for me the shootout will be music.

Have you finished making your Othorns? I need to check them out.~~:smile:

 

[David Chrapla]

Re: 60 Degree DIY Mid Hi

Hahah I need to still build my othorns. I have a Hybrid design that is bigger that I want to A/B it against. I will have to wait until I have another 21 and then build both. So far my single 21" has been just sitting on my shelf in the shed.

I also just saw the post on DIYaudio forum for the shootout. So I will be there. Its only 8mins away from me so I look forward to it.

I was also interested in your smaller PA speakers you had. Wanted to come visit again but always seem to be busy. I always go by your place on Thursdays when I mow a tennis court in Erindale. So I keep thinking about it. Anyways will be fun to see your 12's in a larger area with some real volumes.

 

[Max Warasila]

Re: 60 Degree DIY Mid Hi

Last night I made some progress with my CNC version. It works great... if your gantries are square and calibrated. Otherwise, I'd rather use a table saw.

 

[Don J Davis]

Re: 60 Degree DIY Mid Hi

Last night I made some progress with my CNC version. It works great... if your gantries are square and calibrated. Otherwise, I'd rather use a table saw.

Max, can you take some pics? I'd love to see the progress.

 

[David Chrapla]

Re: 60 Degree DIY Mid Hi

Just heard these the other day against the Krix cinema speaker. And for my own opinion these did almost everything the cinema speaker did but in a much smaller package. And when it comes to transients and dynamics Peter's speakers rocked. I like when a kick drum feels like a kick drum. When the track calls for sudden impact bursts Peter's combo delivered better than the cinema speaker. If I had the money I would be building these for my next L/R mains and PA.

Thanks again Peter for having them on display and showcasing them. Glad to finally hear them above 80db.


Sorry for the dark picture.

 

[Peter Morris]

Re: 60 Degree DIY Mid Hi

Just heard these the other day against the Krix cinema speaker. And for my own opinion these did almost everything the cinema speaker did but in a much smaller package. And when it comes to transients and dynamics Peter's speakers rocked. I like when a kick drum feels like a kick drum. When the track calls for sudden impact bursts Peter's combo delivered better than the cinema speaker. If I had the money I would be building these for my next L/R mains and PA.

Thanks again Peter for having them on display and showcasing them. Glad to finally hear them above 80db.

View attachment 13313View attachment 13314
Sorry for the dark picture.

Hi David,

Thanks for your comments.

The two systems are designed with different compromises.

A Cinema system is designed to reproduce the special effects– car crashes and explosions as well as vocals and music, accordingly it has a lot of low frequency extension. It has to be THX approved and fit in the space behind the screen except for the subs. What you heard was EQ-ed to be flat and there was no X-curve applied.
http://www.thx.com/professional/sound-engineer/approved-equipment-lists/

Krix make a wonderful range of award winning Hi Fi and Cinema systems that are exported and sold worldwide. While they have been commercially successful they are ultimately driven by a passion for audio and invest heavily in R&D. For example, the horns you were listening to were a patented design arising out of a PhD project. http://www.google.com/patents/US20110153282

If you’re in the market for some Hi Fi speakers I would recommend checking out their range.
http://www.avhub.com.au/product-reviews/hi-fi/krix-neuphonix-ae40-loudspeakers-review-and-test-397793

In comparison my system was designed for music. It was designed to offer a solid response to 40Hz and still be usable on a 5 string bass guitar (open “b”). It was designed to offer very high SPL for its size and weight and truck pack well.

In short, the competition was of the highest quality and theDIYs held their own. I think everyone was impressed with both systems.

The Krix system comprised of a 1 inch VHF, 1.5” HF, dual 6”mid, quad 15” low and a double 18” sub. In other words, the DIY (excluding the sub) was trying to do almost as much as the Krix system in your first picture including the quad 15!

 

[David Chrapla]

Re: 60 Degree DIY Mid Hi

Ya I understood that. I was just amazed at what it COULD do. If I had the money these would be my next build. Instead for my much lower budget I am actually going to build something like this:
http://www.krix.com.au/kx-5205.html

I definitely look forward to Dave's future designs And the next bigger design frm you Peter. Haha not that I can afford it.