05-19-2024, 08:31 AM | #67 |
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You set the EQ with all channels running and the channel gains set. If it takes a lot of EQ boost to get to the target, which would be more likely with the underseats, increase the gain on those channels rather than using more than 6dB of EQ. If it takes a lot of EQ cut, which would be more likely on the door speaker channels, reduce the gain on those. After adjusting the gains do the EQ again.
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05-19-2024, 12:57 PM | #68 | |
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Redid the whole thing, following CAT-BUG to the best of my ability. Below are my new results. EQ/gain adjustments are need to bring the 40-150 hz range up relatively? I'm a bit confused here, would it not take great compensations to hit the target curve? I feel it already sounds quite beefy too, but perhaps that is because I am used to weaker sauce. Should it not sum better than this since the individual channels follow the curve quite well? |
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05-19-2024, 01:07 PM | #69 |
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Keep in mind that summation is both additive as well as subtractive, so unless all your sources are perfectly timed to arrive simultaneously (a very difficult thing to do with a car audio system), there will be some cancellation to contend with.
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05-20-2024, 02:59 AM | #70 |
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That left and right bass sweep is odd compared to summation on the full speaker sweep. Just odd
Did you try reverse polarity / 180 flip phase on one side to see if better or worse ? Here’s how bass looks like on HK and Morel woofers for a compassion to yours ( smaller cabin in f80 though) with no eq or phase alignment |
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05-20-2024, 10:52 AM | #71 | ||
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Listened to some bass heavy music on my daily commute. I listened at a comfortable volume but kept getting this weird feeling in my ears, similar to the pressure buildup when you're on an airplane. I don't know what this indicates but clearly there is some underlying issue. |
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05-21-2024, 12:10 PM | #73 |
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On the one underseat woofer channel try it with Polarity Invert and then see what it does to the bass response.
Holy moly what a difference that made! Finally reached a point of basic satisfaction with this project. Looking forward to improving it incrementally over time, but so happy to have a somewhat functional system meanwhile. I've learned so much! Can't thank you and Billfitz enough. Cheers. |
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05-21-2024, 12:49 PM | #74 |
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One more test. Invert both of them and see if that gets rid of the dip from 90-160Hz. It may not, as that could be a boundary reflection issue, but it's worth a try.
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05-22-2024, 12:56 AM | #76 | ||
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This is obviously not the culprit. So what else? Perhaps the second pic can provide some additional clues. Since I was utterly confused as I did the original tune I spent some time to redo electric/acoustic crossover matching and equalizing. Something in the do-over caused a slight improvement of that deep valley around 120-160hz. Am I looking at phase shift in the crossover area? From what I gathered phase issues should be eliminated when you use LW4 for all crossovers(?) So could it be that my response does not adhere to the LW4 slope well enough to reap the benefits? In accordance with this line of thinking, should I revisit my crossovers once more? And on this topic - is LW4 optimal for all drivers, even the under seats? Perhaps play with inverting other drivers? |
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05-22-2024, 02:56 AM | #77 |
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Great result on EQing to target curve.
Let the speakers settle / run in over 20 hrs or so. You may get changes in mid and treble as they free up. Then revisit the EQ. |
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05-22-2024, 05:11 AM | #78 | |
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1. Right sub inverted (current setup, as measured before) 2. Both subs inverted 3. Both subs + Front L inverted Can this sum + phase tool be trusted? Third pic is the best looking, no? I know that this is just the sum of the EQ but perhaps it could still be useful? I will play with different setups when I have the time. |
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05-22-2024, 07:47 AM | #79 |
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Move your mic a few inches in any direction to see if the problem remains the same. If you are using only one measurement position, then you'll be fighting an endless battle of tweaking position dependent anomalies in the low frequency range. You'll need to find the compromise and take action accordingly. This the the fine art of measurement, you're constantly asking yourself what is actionable data, simulations only take you so far....
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05-22-2024, 09:37 AM | #80 | |
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05-22-2024, 05:07 PM | #81 |
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Just echoing the previous two posts.
I think the next stage of tuning evolution would now be REW and using the waving mic technique. It emulates what is heard at both ears and gets around the Comb filtering issue with single fixed mic position to a certain extent. In the higher end tuning shops they will use array mics with six or so mics and take the average of those mics. It more closely mimics head position. An example of fixed mic position was phase alignment my underseat woofers. I’d time alignment the door mids and then phase aligned the underseats woofers Left and right. I had a 3 db dip around 130hz . To get this flat would have been a 0.11 millisecond offset. 38 mm in real terms. Realistically my ears are further apart from that and no doubt my head position will be moving around. Another example was a huge dip in response around 2 kHz. More than -10 db At that wave length it’s roughly the distance the door speaker to centre console/ transmission tunnel. Basically the reflection of the sound wave causing a null. It’s not something that can be sorted in DSP just a fact of the environment. Car audio is complex to tune. So many unequal paths with setting position and speaker placement. Once you get a nice front image where it appears to sit above the dash with good width your there. Just needs a bit of leeway on the frequency response but also tune to how you like your sound once the basics are done. |
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05-23-2024, 04:27 AM | #82 |
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I did use the moving mic method. I think my next step should be revisiting time alignment. Did a very half assed job with that when I first installed the dsp, many changes have been made since that point. Hopefully proper time alignment will prove impactful.
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05-24-2024, 12:39 AM | #84 |
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Getting TA and level matching makes a huge difference for driver seat tune. It’s night and day difference to the front image. Especially in vocal frequencies. Image gets centred and sits above Dashboard.
Multi seat tune is a compromise , I put the mic on a camera stand sitting at ear height in center console. Main aim to to keep bass sounding upfront . Othewise slight offset on door mids and tweeters ( mine are active ) Trunk sub aligned to 1/4 wave is where I’ve had best results. But remember, this is simplified base audio ( 3 way front / rear ) plus trunk sub. So no centre speaker. |
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05-24-2024, 01:50 AM | #85 | ||
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Played around with inverting phase. When I inverted L underseat instead of R underseat I saw a dramatic change! This phase stuff is very mysterious to me. Some additional experiments gave slightly different results, for example inverting underseat R + indoor L gave a similar response, but I figured just inverting underseat L looked marginally better. Any comments on my frequency response as per latest changes? Looks like I might have to play with gains/level matching drivers again to bring the underseats up a little bit? What do I make of the peaks and valleys, does it look okay or should I look to redo the process in the future with my newfound knowledge? |
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05-24-2024, 02:00 AM | #86 |
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Also, in case I do revisit the whole process. Looking at this raw measurement of both eartquakes and in door drivers, can you confirm that 125hz is indeed the optimal crossover point? Cut the earthquakes at 30 or 35 hz?
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05-24-2024, 02:55 AM | #87 |
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Ok . So TA is more about influencing the sound of the front stage image. Eg are vocals from the centre of the car. Does the front image sit above the bonnet. Does the stage width go beyond the location of left and right speaker locations. To a certain extent it can change the frequency response. But not as much as eq.
Eq is more about following a target curve and flattening off the peaks , and addressing drops to a certain extent. If I time align only and level match speakers this makes the biggest difference to the front stage. Especially lower frequencies at the point where they are directional and vocal range . Treble not so much. Audifrog website explains TA well. To an extent it does point out Bills view on TAing in a small space . Check out the triangle section . https://www.audiofrog.com/time-alignment-part-1/ On the crossover point between eq and door speakers , the doors don’t go quite low enough so should be 20 hz higher based on the sweep. The earthquakes drop off before getting to that point. But in graph 2 with the phase experiment your hitting the target curve nicely. I’d stay were you are unless your hearing distortion from the door speakers on its lower frequencies. I’m a bit surprised by the Earthquake dropping quickly from that 40hz peak. So for low pass 30-35 could be a good region to try. |
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05-24-2024, 10:51 AM | #88 |
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The small peaks and valleys are the result of reflections and having multiple sources. For the most part you can't hear them. The best you can hear is with 1/6 octave resolution, so that's what you should be measuring with. There's no need to highpass the Earthquakes in terms of power handling or excursion, but there's also no point in sending them content below 35 Hz that you can't hear.
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