[keep_hope_alive]

Those delay values appear to be due to acoustic alignment with the sub. Do you have a bandpass on the sub or just lowpass? I typically see higher overall mb-mid-tw delays when the sub is low pass only due to phase rotation at the crossover. Adding a subsonic filter can bring the sub forward in time so the delays aren't as high.

This only tends to affect noise cancellation systems during calls, where the delays push the signal out of the BT echo cancellation timeframe.

[psteelejr8]

Originally Posted by SWRocket

Amazing, thank you!
I had a similar response. My XOs are at 70Hz-300Hz and 2600Hz all LR4 as well
I can post my raw measurements, just didn't want to highjack you thread...

Please do post! I took a look at your build log and your build is amazing. Almost went with the same AF mids and tweets you have (and the stealthbox, which I had briefly before deciding to go vert). I do a really bad job of logging and taking pics (always rushing due to my toddler)

[psteelejr8]

Originally Posted by SomeGeoffGuy

That is pretty awesome on how easily it blends those four speakers. Having not built a serious car stereo since the 1990's, I am pretty amazed at the technology available. It is expensive for sure, but if I was paying $400 for my first Nakamichi amp in 1986, the prices for that JL gear seem on par with that in today's dollars. And the tuning value with built-in DSP is definitely there!

Out of curiosity, what made you pick those Scanspeak components? I don't think I have ever even seen an aluminum cone car stereo speaker before (see them a lot in home audio). And it is not like those are a common brand.

Thank you for posting, great info.

-Geoff

Once I decided to go active, imo the best bang for your buck is with raw drivers. I chose the illuminator mids because they have the most measurable linear excursion of any other 6-7” midbass on the market. Other options were the Purifi 6.5’s, which were more expensive and better suited for a two way. The aluminum version is best as a dedicated midbass, and aluminum is a bit more robust to temperature and humidity changes than their paper cone variant.

The SB 2.5’s have a nice, flat, clean response and they actually fit in the stock location. I wish they had a bit more sensitivity, but that’s it. Also considered AF GS/GB25 and Morel CCWR254’s but these are substantially cheaper than both, offer similar linear excursion as the AF’s, and are more detailed than both.

My fav tweet (especially for a two way) is the SB Acosutics SB29BAC, but it’s a bit too big to fit in the a pillar firing off-axis as I have mine. The Scans look better and perform just as well for my application (>3500hz), so I opted for them. Also got both the midbass and tweets discounted, about 15% off.

[psteelejr8]

Originally Posted by keep_hope_alive

Those delay values appear to be due to acoustic alignment with the sub. Do you have a bandpass on the sub or just lowpass? I typically see higher overall mb-mid-tw delays when the sub is low pass only due to phase rotation at the crossover. Adding a subsonic filter can bring the sub forward in time so the delays aren't as high.

This only tends to affect noise cancellation systems during calls, where the delays push the signal out of the BT echo cancellation timeframe.

I have a bandpass on tunes with the top up, and low pass only on tunes with the top down. However, this didn’t affect the delays when measured via impulse response. Doing the distance method, the subs are very close in distance to the right midbass from the driver listening position, but there was some arrival polarity weirdness (I have all my drivers wired with the correct polarity). On the screen I posted with the crossovers, you’ll notice that all the drivers have the polarity flipped except for the sub. The Max is able measure arrival polarity so I just set the delays and polarity in TUn based off of its measurements. I used its signal generator as an input to the VXi hub (where the Nav-TV would typically be connected).

All of this was a bit of a surprise since all my crossovers are LR4, so electrically there should be phase coherence—but clearly it isn’t the case acoustically!

[keep_hope_alive]

Originally Posted by psteelejr8

I have a bandpass on tunes with the top up, and low pass only on tunes with the top down. However, this didn’t affect the delays when measured via impulse response. Doing the distance method, the subs are very close in distance to the right midbass from the driver listening position, but there was some arrival polarity weirdness (I have all my drivers wired with the correct polarity). On the screen I posted with the crossovers, you’ll notice that all the drivers have the polarity flipped except for the sub. The Max is able measure arrival polarity so I just set the delays and polarity in TUn based off of its measurements. I used its signal generator as an input to the VXi hub (where the Nav-TV would typically be connected).

All of this was a bit of a surprise since all my crossovers are LR4, so electrically there should be phase coherence—but clearly it isn’t the case acoustically!

Awesome information!

That's better, because I didn't think the VXi DSP had phase rotation since it uses IIR filters, but your delays made me wonder if that was the case.

Even with 24db LR filters (HPF have positive phase shifts, LPF have negative phase shifts, 45 deg of rotation for each 6dB/oct slope = 180deg at 24dB/oct - and if both drivers are 180 deg then they re-align in phase but a full cycle off in time). There is still phase rotation with some topologies - and while it's predictable with passives or op-amps, it's harder to know what exactly the active filter is doing when it's all DSP. This article does a good job explaining it: https://www.ranecommercial.com/legacy/note160.html.

I didn't notice the polarity flip. That makes sense given the other info.

[psteelejr8]

Originally Posted by keep_hope_alive

Awesome information!

That's better, because I didn't think the VXi DSP had phase rotation since it uses IIR filters, but your delays made me wonder if that was the case.

Even with 24db LR filters (HPF have positive phase shifts, LPF have negative phase shifts, 45 deg of rotation for each 6dB/oct slope = 180deg at 24dB/oct - and if both drivers are 180 deg then they re-align in phase but a full cycle off in time). There is still phase rotation with some topologies - and while it's predictable with passives or op-amps, it's harder to know what exactly the active filter is doing when it's all DSP. This article does a good job explaining it: https://www.ranecommercial.com/legacy/note160.html.

I didn't notice the polarity flip. That makes sense given the other info.

Ah! Now it all makes sense. I was still a bit freaked out by the actual measured arrival polarity being opposite of the (correct) wiring. But I am very happy with the results.

[psteelejr8]

Originally Posted by keep_hope_alive

Awesome information!

That's better, because I didn't think the VXi DSP had phase rotation since it uses IIR filters, but your delays made me wonder if that was the case.

Even with 24db LR filters (HPF have positive phase shifts, LPF have negative phase shifts, 45 deg of rotation for each 6dB/oct slope = 180deg at 24dB/oct - and if both drivers are 180 deg then they re-align in phase but a full cycle off in time). There is still phase rotation with some topologies - and while it's predictable with passives or op-amps, it's harder to know what exactly the active filter is doing when it's all DSP. This article does a good job explaining it: https://www.ranecommercial.com/legacy/note160.html.

I didn't notice the polarity flip. That makes sense given the other info.

Also forgot to mention, the drivers aren't labeled on my post that shows the delay times. The subs are technically not delayed at all, and they are on another amp that is interfaced to the primary by the Vxi-hub. So everything illustrated is only the delay for the midbass/mids/tweets. I think measured delay for the subs was 10.08ms, but since they are the furthest away they are the reference, and delay is added to all the other drivers except the subs.