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Multi-Way Conventional loudspeakers with crossovers

OmniDirectional - work in progress
OmniDirectional - work in progress
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Old 13th September 2017, 09:27 PM   #171
BYRTT is online now BYRTT  Denmark
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OmniDirectional - work in progress
Takes 30 seconds to create target overlay into Rephase and import to REW : )
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Old 13th September 2017, 09:53 PM   #172
DonVK is offline DonVK  Canada
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Is that overlay just for the visuals, or is there another use for it?
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Old 13th September 2017, 10:19 PM   #173
BYRTT is online now BYRTT  Denmark
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would mean there is other use down the road but if you don't agree lets say its just for the visuals.
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Old 13th September 2017, 10:49 PM   #174
wesayso is offline wesayso  Netherlands
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The ease of use makes it attractive to check your acoustical slopes, right?
It's like having a textbook generator handy that shows us how it "should" look acoustically. I find good use for these theoretical models. Too easy not to use it.
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Old 14th September 2017, 12:25 AM   #175
DonVK is offline DonVK  Canada
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@Byrtt & @Wesayso I'm OK with a visual aid "template" to check the plots, but the word "target" implies another use, like there is an adjustment stage involved to achieve the target. I'd be happy to try them once I confirm (adjust) the HF section of the speaker.
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Old 14th September 2017, 03:22 AM   #176
fluid is offline fluid  Australia
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If your speaker was active you could use EQ to get the final acoustical slope of the crossover to match more closely to the slope you are aiming for which would make the summation flatter.

Hard to do that in a passive as the EQ would be applied to both legs. Could be useful to check how close the passive components you used got to the slope you were after.

If you get to go active with your Pi project it might be more useful to you.
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Old 14th September 2017, 05:02 AM   #177
DonVK is offline DonVK  Canada
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I'm OK with the passive filter slopes and they're close enough to design intent. There is just a little more slope than planned, probably from the woofer fading.

An active system definitely has advantages and it would mesh well with the RPI project. That being said, I would still have all the physical issues to sort out which have been mostly separate from the XO and EQ.
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Old 15th September 2017, 04:36 AM   #178
DonVK is offline DonVK  Canada
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Default HF section tests

The cone is basically the same profile as the inside of the waveguide with extended slopes to the edge of the disc. I can replicate the approximate shape in polystyrene. Adjustments were made to the initial cone diameter (tip) and the slope contour.

The baseline waveguide and compression driver, in open air (no cone) are shown in graph#1. Its not a very flat response and I'm not sure if its the WG or the CD or possibly interaction with the XO. I don't have other horns or compression drivers to compare to.

Various cone shapes with moderate different slopes and curvatures were tried to reproduce the baseline open air response at the disc edge with the cone in place. Graph#2 shows that below 5Khz the response is not that sensitive to the cone shape adjustments. Above 5Khz, small changes in the slope or the gap can make a significant difference. I think this will be an ABEC exercise eventually.

Even with the cone improvements there is still significant bump at 2.5KHz which is reduced using a series RLC notch filter. Graph#3 compares the V4 and V5 performance at 1m and its much flatter. Graph#4 compares the open air response to the V5 with notch filter at disc edge. We have the open air response at the disc edge.
Attached Images
File Type: jpg baseline waveguide + driver open.jpg (74.1 KB, 168 views)
File Type: jpg DSCN2083 reduced.jpg (441.8 KB, 167 views)
File Type: jpg DSCN2089 reduced.jpg (455.0 KB, 163 views)
File Type: jpg compare various HF shapes.jpg (96.9 KB, 159 views)
File Type: jpg DSCN2088 reduced.jpg (397.4 KB, 70 views)
File Type: jpg compare flatness v4 to v5.jpg (76.8 KB, 60 views)
File Type: jpg compare open WG to final cone.jpg (87.6 KB, 36 views)

Last edited by DonVK; 15th September 2017 at 04:37 AM. Reason: clarify test
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Old 15th September 2017, 06:06 AM   #179
graaf is offline graaf  Poland
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Quote:
Originally Posted by DonVK View Post
Compared to V4, the V5 cones and discs have changed dimensions and now have a 16L sealed chamber. I'll measure the response again to see what tuning is required. Only the woofer and XO are connected.

The V5 has a peak at 630Hz, from the chamber length behind the woofer. Graph#1 is the woofer off axis, no cones, at the disc edge 7 cm up (mid disc height). I've also suspected there may be interaction between the cone and the woofer setting up a resonance at this freq. So I check a few other cone shapes [none, flat disc, V4 LF + HF, plus V5 LF + HF] to see if I could reduce it. Turns out there is interaction and its centered around the 630Hz =(344/(2*0.27m) or 1/2 lambda as shown in graph#2. Different shapes have different issues and the final cone shape mimics the response of "no cone" as shown in graph#3. This sounds odd, but it seems to be the least "interference" and allows me to add the HF section above without creating more issues like a flat top above the woofer. In most cases the response below 430 ( 1/4 woofer diameter) is the same regardless of cone shape until the woofer starts getting directional at 1/4 lambda 344/(0.2m*4)= 430Hz

The final cone shape still allows some resonance, so a series RLC notch filter was added in parallel to the woofer to suppress it. There is still some residual bumpiness that will be EQ'd out later, or maybe with damping using different chamber fill. In either case I'm happy with it and HF testing is next.
It looks You have a lot of problems with those cones - so why such a cone at all?

I understand that You'd like to put the tweeter above the woofer but in that case why not just aim a compact neodymium tweeter up and the "cone" required in such configuration (to mount the tweeter in) would be much smaller and creating less problems. Actually it could be in a shape and material minimizing reflections which are utterly undesirable.

Perhaps it wouldn't look so cool like a Duevel clone but definitely less problems.
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Old 15th September 2017, 06:48 AM   #180
fluid is offline fluid  Australia
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Quote:
Originally Posted by DonVK View Post
Its not a very flat response and I'm not sure if its the WG or the CD or possibly interaction with the XO. I don't have other horns or compression drivers to compare to.
Up to 10K the response is just like most waveguides/horns you get a greater efficiency as you go down in frequency until the waveguide loses pattern control. The bump at 15K is not quite so normal but could well be breakup. Is it there in the manufacturers data?

The shape of the tip will be acting as a phase plug so different shapes there might be worth looking at.
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