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Budget Directiva Project

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Rick Sykora

Rick Sykora

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Got the SIG180 in and did a quick check of fequency response. The driver is more sensitive than the Purifi and so gave the tweeter a bit more gain. There was also a midrange dip but dropped the tweeter crossover a bit and it filled in. A quick listening test suggests there is more work to be done. I had checked the bass tuning in VCAD but suspect I need to revisit. The bass is not awful, but something is off. Need to reassemble the other r1 to use as a baseline.
 
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Rick Sykora

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Have an original r1 on deck for the test but found a major configuration problem that affected the sound of the SIG180 variant...

As a quick check of my crossover mods, had inverted the tweeter to check for a reverse null. When I switched over to music, forgot to reset the null. :oops:

Not too surprisingly, it sounds much better now.!
 
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Rick Sykora

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So here is a quick fr check comparing Directiva r1 to the budget version (r.5 for now).

1708011899031.png


Before I discuss, note these are ungated, psycho-acoustically smoothed, and in-room. I did not change anything except the speaker between measurements. After I measured, I adjusted the r1 trace to overlap the r.5 one. There are a couple of prominent differences. First, the droop in r1 response between 2-3 kHz. I adjusted the r.5 crossover to eliminate this. So am going to assume this is measurement anomaly and ignore for now. Am using my Umik-1 and will be switching to a balanced mic for better phase measurements soon.

The other difference is in the low bass. This is likely mainly due to the higher sensitivity and the higher fS of the SIG180. In sims, the PR tuning does not play a major role here so likely will redo the level matching. The higher fS should be somewhat offset by overall diffs in the SIG180 TSP results. Will revisit this later after I update the VCAD sim with the new driver. Will also run an impedance check to see how the box tuning differs.

You may have noticed; I have not shown any off-axis measures yet. The reason for this is twofold. One, for these initial checks, I did not put the turntable in place. Two, without the SIG180 driver measurements, my crossover design is non-optimal and so the results will not be useful until I complete.
 
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Rick Sykora

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No design progress yesterday as was fixing a member’s amp. This weekend‘s project is to repair cracked ceramic tile in our foyer. However, did manage to find someone qualified and willing to help with precut baffles. I do plan to put my better measurement rig in place and test it out.
 
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Rick Sykora

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My weekend ceramic tile repair has turned in to a rip and replace project. Did manage to redo some earlier measurements that confirmed my suspicion about the 3-4 kHz dip. It is related to my measurement rig. Have not had to time to determine root cause as yet.
 
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Rick Sykora

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Before I changed the measurement rig, thought I might try the WaverCor woofer but found is another 2mm larger than the other woofers. I really like the ability to use the same baffle for different woofers. The additional space would also likely mean that it would contact the tweeter edge. So am going to set aside the WaveCor for now. The leaves the RS180 which while respectable, seems rather dated compared to the others. Given the SIG180 profile is more comparable to the Purifi, it is the primary candidate as it is likely to need fewer crossover modifications.
 
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Rick Sykora

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Here are some initial measurements for one version of the crossover (a slight variation of the r1 active design)...

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This is still my UMIK-1 and so have not taken individual driver measurements to use in VCAD as yet. There is some apparent brightness in the 10-14 kHz range. This is mainly due to the particular DXT tweeter I am using and will try another tweeter as I continue to refine the crossover. Checking with others and against the r1 proto, it appears to be a more extreme variant of known DXT behavior.
 
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Rick Sykora

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Realized that might be nice to share a pic. Not surprisingly, looks a lot like r1 with a different woofer!

IMG_0769.jpeg


p.s. My placeholder designation for this one is r.5; not my most creative but it is less than r1 in a few ways, so works for now.
 
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Vance Dickason has reviewed the SiG180 in the latest issue of voice coil magazine. He likes it a lot, especially for the price. The only real quibble would be that distortion, while lacking any severe resonances, does bump around the 1% mark for a while. Still, very good for the price.
 
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Rick Sykora

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Vance Dickason has reviewed the SiG180 in the latest issue of voice coil magazine. He likes it a lot, especially for the price. The only real quibble would be that distortion, while lacking any severe resonances, does bump around the 1% mark for a while. Still, very good for the price.

I saw Vance’s review and the distortion is in line for its class. At about a tenth of the price of the Purifi, did not expect it to be near as good. Still would consider something in between but may need to cut another baffle.:cool:
 
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Rick Sykora

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As have played more with the SIG-180, it is not a great fit for even a budget Directiva. It needs a bit more volume to get f3 in the 40s vented. It would likely do better in the minitower. Does not help that the fS is considerably higher than specified. Going to try the WaveCor as it looks more promising albeit around 3 times the price. SB Acoustics has decent options too, but as I mentioned, their cutout is quite different so will take some extra work before I could try.
 
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