[DannyBadorine]

Don’t forget to check both the horizontal and vertical off axis response.

Absolutely.  I have those tests, I just didn't put them on this graph.  It's all very telling and I'm having to decide what's more important to me.  Flat Frequency response, off axis consistency, how wide of a dispersion is important and all of the usual stuff.  There is a lot of data to contemplate, but it's definitely coming together.

[DannyBadorine]

It's frequency is dependant on if the signal coming from the driver is beaming or radiating, and smaller woofers will begin radiating before larger ones.  From there the width of the baffle, and how sharp the edge is will determine its frequency and dramatically it shifts.
 
The peak is caused by the sound waves reflecting off the baffle, and the dip is caused by the sound waves wrapping around and bouncing off the side of the cabinet instead.

The sharper that edge and the wider the baffle is compared to the woofer determines the frequency at which it is caused, and how dramatic the peak & dip are.

Rounding off that edge softens the transition. For the size of your baffle, i would recommend the larger 1/2 round over.

The reason it smooths out at 15° off axis is because those reflections from the baffle are arriving at different times, and their phases are misaligned, so they neither sum nor cancel one another.

This box got better with your roundover suggestion but I'm still not satisfied.  I'm hoping to get this frequency response even closer.

Would you say that using an M165 in place of the M130 would help the low mid range problems?  Would changing the shape of the box (putting a fin on one side of the rear of the box) help smooth this out by breaking up the frequencies that are wrapping around?  Would adding another M130 above the tweeter help these low mid range problems?  And last question, would a 1" roundover make things even better? 

[Norman Tracy]

Danny, clarifying a rather important detail here. I thought your speaker system being discussed here has a sealed bass box with a sealed midrange/high frequencies box on top in a tower architecture. Now you asked "changing the shape of the box (putting a fin on one side of the rear of the box) help smooth this out"? Is the midrange box open back? Or is the fin in question to lengthen the acoustic path around a sealed box?

[DannyBadorine]

Danny, clarifying a rather important detail here. I thought your speaker system being discussed here has a sealed bass box with a sealed midrange/high frequencies box on top in a tower architecture. Now you asked "changing the shape of the box (putting a fin on one side of the rear of the box) help smooth this out"? Is the midrange box open back? Or is the fin in question to lengthen the acoustic path around a sealed box?

You are correct.  The mid range is sealed.  The fin would be to vary the acoustic path of the low mid range frequencies that are wrapping around the box in an effort to reduce the specific frequencies that are phase cancelling in front.  Specifically 350Hz, 250Hz, 200Hz as seen on the graph.  Then, with the crossover, I can reduce the upper mid range 600Hz-1600Hz coming from the mid range driver and the entire mid range will fall within +/-2 or 3db.  It's close now, probably +/-4.5db but I'm trying to get that last 1.5-2db to come in line. 

[Danny Richie]

You have a phase (time arrival) issue.

Try measuring the response without the lower woofers, measure the lower woofers only and overlay that with the summed response. That will tell the tale.

[Norman Tracy]

Over the last couple of weeks I have built a couple of prototypes of the Version 2.0 Neo 3 Wave Guide that Danny B. has been testing in California. This pair is for my R&D efforts centered on systems using Purifi PTT6.5 woofers. These protos are cut into Balticbirch plywood and sized to match the Fi16 enclosure featured in my PTT6.5 work.



Version 2.0 Neo 3 Wave Guide CNC cutting begins.



Version 2.0 Neo 3 Wave Guide CNC cutting roughing pass completed.



Version 2.0 Neo 3 Wave Guide CNC cutting completed. BTW the large V-cut bit shown was only used for the edge chamfers. Wave guides were cut with ball end mill bit.



Version 2.0 Neo 3 Wave Guide Birchply prototype.



Version 2.0 Neo 3 Wave Guide Birchply prototype with Fi16 Purifi woofer.

The state shown in the last pictures was achieved at about 10 PM last night. Initial listening to uncalibrated bi-amp system with 2A3 SET amp driving the Neo 3 + wave guide and ACG 1000 Icepower on the woofers. Preliminary listening session at don’t-wake-up-household levels is WOW. If it sounds this good with the Neo 3s taped onto the baffles and levels guessed at it is quite exciting what is in store as mechanical, finishing, and acoustic refinements are brought to the prototypes.

[Tyson]

Those Purifi woofers look very interesting. 

[DannyBadorine]

You have a phase (time arrival) issue.

Try measuring the response without the lower woofers, measure the lower woofers only and overlay that with the summed response. That will tell the tale.

Alright, I measured this way.  The problem is not between the low speakers and mid speakers.  Those measure well and are in phase together.  The problem is a combination of the box design and my measuring environment.  There is a baffle problem around 380Hz-410Hz.  The waveform here is a product of wrapping around the box.  But the problems below that in the 150Hz-300Hz are mostly artifacts of where I was measuring.  I added a baffle step correction to the mid range to level out the low mids and high mids within the mid woofer and it was extremely helpful.  There are still 3 problems with the speaker that I am seeing. 
1) The problem I detailed above that is the result of the narrow baffle.
2) A dip around 2KHz which will hopefully be fixed by properly spacing the tweeter and mid-woofer
3) The dip near 7KHz which is a baffle diffraction that will hopefully be fixed by moving the tweeter to the top of the baffle and rounding the edges better



. 

Otherwise, the speaker has a pretty flat frequency response in my measuring environment which is not an anechoic chamber.  The response would likely be flatter in an anechoic chamber. 
I have attached a 1/12 smoothing frequency chart and a 1/3 smoothing chart.

Also no note that the tweeter is in the waveguide above made by Norman Tracy.  It's testing incredibly well and will be in the final design.  It looks amazing and sounds amazing.  It is recessing the tweeter and putting it into phase.  I listened to it compared to the B&G flush mount and the custom waveguide sounds better since it's in phase.  It's horizontal and vertical response is incredibly consistent.

[DannyBadorine]

With changes to the crossover, I have been able to achieve this frequency response.


It's still not perfect in the low mid range but it's much closer.  It measures really well off axis.  Most importantly, it sounds great.  The instrument separation is amazing.  Working with the GR drivers is awesome.  The M130 sounds really good as high as 3KHz and stays consistent off axis.  I'm excited to hear what 2 of these sound like!