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Multi-Way Conventional loudspeakers with crossovers

Synergy build with TF0410MR mids
Synergy build with TF0410MR mids
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Old 22nd June 2018, 08:04 AM   #11
birkinshawc is offline birkinshawc  United Kingdom
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What is interesting is that if I simulate a 6mm spacer in between the driver and the horn wall (~50cm3 per driver), thereby increasing the front volume, the response looks a lot better than the one with the lower volume.

FYI I calculated the driver's front volume as 33.3cm3 and didn't include the port volume (around 0.8cm2 per port right now). If I add the port volume it doesn't have much impact though.

Should I go with this approach, with the 6mm spacer and a steep drop-off after 1.2kHz? It makes life a lot easier not having to route a ring in the horn wall to avoid the driver impacting at Xmax

I also tried moving the driver up and down the horn but it did not really change the response (this calculation was very easy thanks to Bill's spreadsheet).
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File Type: png Screen Shot 2018-06-22 at 08.40.38.png (67.7 KB, 332 views)
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Old 22nd June 2018, 06:15 PM   #12
GM is offline GM  United States
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Grrr posted an in-depth response that disappeared, so only time to say neither is the goal! Design based on the flattest pass-band amplitude AND phase response.

GM
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Old 22nd June 2018, 07:54 PM   #13
nc535 is offline nc535
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Quote:
Originally Posted by birkinshawc View Post
Should I go with this approach, with the 6mm spacer and a steep drop-off after 1.2kHz? It makes life a lot easier not having to route a ring in the horn wall to avoid the driver impacting at Xmax
t).
the nice steep slope seems ideal until you think about the XO to the CD - it will need a complementary, steep slope, which of course is not hard to do with DSP.

Of course if you have reservations about using brick wall filters, (e.g. don't like the latency) then you should consider tweaking bandpass chamber and port parameters for the most gradual slope you can achieve. I've done this exercise a few times, making the reflection notch shrink to a small glitch in the middle of the gradual roll off response transition. When you have such a response you can equalize it to match an LR8 acoustic slope with IIR filters and the XO will be as high as or nearly as high as with the brick wall response, and you will have plenty of rejection for the HF response artifacts that get through the acoustic low pass filtering.

The steep response that you have is so steep that it may be hard to match to the CD you are crossing over to. When you add filtering to soften it up or for additional attenuation above the dropoff, you will likely pull the XO point lower.
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Old 22nd June 2018, 09:58 PM   #14
birkinshawc is offline birkinshawc  United Kingdom
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Here is the latest attempt, aiming for a flat passband and to get up towards 2kHz.

I don't think I can do much about the bottom end extension as it is a sealed back mid.
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File Type: png Screen Shot 2018-06-22 at 22.55.52.png (95.3 KB, 295 views)
File Type: png Screen Shot 2018-06-22 at 22.55.45.png (110.2 KB, 295 views)
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Old 24th June 2018, 02:08 PM   #15
nc535 is offline nc535
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quick advice
Vrc is unrealistically large try about 2 cc, not much difference but more accurate

S1 doesn't match CD exit. change to 5 cm2, again not much difference

Ap is too small, check particle velocity in port, should be less than 17 m/s at LF peak

L12 assumes sound bounces off apex of horn for reflection null when in fact it bounces off phase plug typically 3 cm or so deep inside the CD. Increase L12 to match CD.

Response shape is still too steep except for brick wall filter XO. Look at attached for alternative tuning. Green trace is 1250 Hz LR6 acoustic target. Grey is raw response. Red is response EQed to match target response using available PEQs in HR.

The ripples in the raw response are, I believe, due to mouth reflections which could be reduced with round overs instead of a secondary flare. Also, state of DIY art, is 3D printed throat matching exit angle of CD.

Good luck.
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File Type: jpg TF0410MR sim on conical.jpg (212.0 KB, 272 views)
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Old 24th June 2018, 05:11 PM   #16
bwaslo is offline bwaslo  United States
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Synergy build with TF0410MR mids
Depending on what parameters are being used for the driver, I think the huge Vrc is the right way to go. This is a sealed back driver, changing the back volume isn't going to do anything in the least since it's blocked from the back of the cone. The compliance Cms from the driver measurements already includes all the volume restriction that can ever happen, so don't want a Vrc entry that can affect the operational compliance.
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Old 25th June 2018, 09:08 PM   #17
birkinshawc is offline birkinshawc  United Kingdom
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I think I am getting somewhere now, thanks to all the tips. I have done the following:

- Implemented most of the suggested tweaks from nc535 in the simulation
- Moved the taps up towards the apex, now 2.5" down rather than 3.3"
- Changed the tap diameter to 20mm
- Got rid of the routed ring around the edge of the driver, since I can see that at xmax of 1mm it is not necessary
- Changed tap hole depth back to 12mm
- Added a 8mm layer of plywood with a 38mm diameter hole cut out over each tap. By playing with different sized holes the volume of the front chamber can be fairly precisely predicted. Much better than when routing out the frustum from the horn wall. Of course this only works well because these drivers perform better with some volume in front.

Pics attached... seems to be looking good now?
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File Type: jpg IMG_0819.jpg (288.6 KB, 70 views)
File Type: jpg IMG_0822.jpg (492.3 KB, 107 views)
File Type: png Screen Shot 2018-06-25 at 22.00.26.png (110.8 KB, 105 views)
File Type: png Screen Shot 2018-06-25 at 22.00.34.png (94.3 KB, 62 views)
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Old 25th June 2018, 09:11 PM   #18
birkinshawc is offline birkinshawc  United Kingdom
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Now with a little EQ and a LR12 slope on each end (250Hz and 1kHz). Will play around with this some more once I start integrating the tweeter.
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Old 8th July 2018, 09:35 PM   #19
RobWells is offline RobWells  United Kingdom
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Any updates ?

I spent the afternoon building a sled thingy for my tablesaw so just need to pick up some mdf and I'll start building some test boxes for my own project.

Rob.
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Old 28th July 2018, 06:54 PM   #20
birkinshawc is offline birkinshawc  United Kingdom
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I started integrating the bass, using a single B&C 10PS26 per side. The modelling showed this would work better with a long port length and the only way I could see of physically getting this integrated was by doing something like the Danley Jericho, where there is a secondary horn for the bass driver that joins the main horn close to the exit. I was not fully sure about how to model it in Hornresp and just did it as a conical horn with the driver at the apex (not offset driver) and 3 sections. So If you look at the schematic attached, the junction with the main horn is just right of the centre of the picture. I figured that once I had it looking ok in hornresp I would make a prototype and see how it turned out.

In actual fact the bass extension is much better, but I am measuring this indoors. There is a null at around 160Hz that moved from 190Hz when I moved the speaker in the room, so I am guessing it is a boundary cancellation? I still need to get this outside to measure it properly.

As others have noted, the sealing is really important. When I did not have it properly sealed everywhere there were some strange noises.

I've also attached the response of the full 3-way, again measure indoors. I have not really spent much time on tuning this yet, but it sounds awesome already and is very loud even with only one midrange driver connected (I will have 2 in the final version).
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File Type: jpg IMG_1494.jpg (448.8 KB, 79 views)
File Type: jpg IMG_1493.jpg (454.0 KB, 76 views)
File Type: jpg IMG_1496.jpg (299.3 KB, 67 views)
File Type: jpg IMG_1495.jpg (321.6 KB, 50 views)
File Type: png Screen Shot 2018-07-28 at 19.50.10.png (120.0 KB, 42 views)
File Type: png Screen Shot 2018-07-28 at 19.50.20.png (169.8 KB, 39 views)
File Type: png Screen Shot 2018-07-28 at 19.50.43.png (163.6 KB, 27 views)
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