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Triticum Agricolam

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Triticum Agricolam last won the day on May 18 2016

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About Triticum Agricolam

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    Eastern Washington State
  • Interests
    Speaker enclosure design & construction

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  1. Fi SSD Port Noise Question

    The port calculator on carstereo.com uses a formula that doesn't work well with the high excursion subs we have now. Since you have everything in WinISD I'd suggest increasing your port area until the peak port velocity get no higher than 72 feet/sec.
  2. 6th Order Port Area Experiment

    The in-vehicle testing was just a repeat of what I measured outside. I'm not going post the graphs showing each configuration at different power levels since it pretty much shows the same thing as the outdoor measurements just with cabin gain added in. If someone really wants to see it just say so and I'll post them up. Here is the graph showing the four combinations at max power: The yellow line is the large port config, the pink line is the 4th order config, the blue line is the small port config, and the green line is the low tuned small port config. Since cabin gain boosts low frequency output and the large port box performed better than the rest down low it is now the highest peak output config. As kind of a side note, here is a comparison between the outdoor measurement of the large port config and the in-vehicle measurement: You can see the cabin gain really has a big effect especially between 30-40 hz. Its boosting output around 15 dB!
  3. 6th Order Port Area Experiment

    Here is the impedance graph of the three styles at different power levels: What jumps out at me is how as power is increased into the small rear port config the impedance spike around 23 hz diminishes, and the impedance around the 32 hz tuning increases. The typical three spike impedance graph of a 6th order system begins to look like the two spike graph of a 4th order system.
  4. Three 8" subs vs two 10" subs

    How much depth do you have to work with? The problem with most shallow mount subs (and pretty much all 8" subs) is they have limited excursion capacity. With a sealed box output is directly related to cone displacement (cone area * Xmax) so you want to maximize that. I think going to two 10"s COULD get you improved performance, but they need to have pretty decent excursion capability to do so. Something like the Sundown SD-3 series jumps to mind.
  5. Three 8" subs vs two 10" subs

    Is the 1.2 cu ft the total internal volume you have to work with?
  6. Box Design Round 2 - P3D4 Sealed Enclosure

    Sounds good to me. Sealed boxes are really hard to screw up. They aren't very sensitive to changes in box volume. As long as they don't leak and aren't too big for the power you are running (and yours won't be) you are good to go.
  7. 6th Order Port Area Experiment

    How do those four configurations compare to each other? Here is the output of all four at the highest power level: The yellow line is the large port config, the pink line is the plugged port (4th order) config, the red line is the small port config, and the blue-green line is the small port lower tuned config. So the whole reason I performed this experiment was to see how a series-tuned box will small rear port area performs compared to one with large rear port area. Does the small rear port area config get louder? The answer is yes, and no. It depends on the situation. Between about 42 - 64 hz it does get louder, above and especially below the large rear port area config beats it though. What I find interesting is the config with the highest peak output is the plugged rear port (4th order) configuration. It has the highest peak output of everything by a fairly significant margin. You can also see that the large rear port config has the widest bandwidth (significantly). Based on what is shown here with the SPL measurements what I theorize is happening is at higher power levels the small rear port configuration gets so much port compression that it begins to perform somewhat like a 4th order bandpass. The peak output increases, but at the expense of higher & lower frequency output (and reduced bandwidth). Since the rear chamber still leaks into the front chamber, you don't get quite the peak in output of the 4th order config, overall the performance ends up being somewhere in between the large rear port config and the 4th order config. If you go back and look at the impedance plots, they show pretty much the same thing with the small rear port config measuring between the large rear port and plugged rear port configs. Next up will be the in-vehicle measurements. I'll try to get those up later tonight.
  8. 6th Order Port Area Experiment

    I got some time today to take some SPL/frequency response measurements. I was hoping to test everything all at one, but I screwed up when I was making the lower tuned, large port configuration so it wasn't included in today's testing. I'll get to it eventually. For today I tested the large and small rear port, higher tuned configuration, the sealed rear chamber config, and the lower tuned small rear port config. I was able to take measurements both outdoors and in-vehicle. Over all I tested 48 different port configurations and power levels. Its a lot of data but I'll try to organize it and present it as best as I can over several posts. So first off, here is my outdoor testing apparatus: Mic is one meter from the port opening. I measured at 38 volts (about 360 watts at 4 ohms) and then decreased the input signal in 4 dB increments down to -20 dB. This should show how the frequency response changes (if any) over different power levels. I picked 38 volts for my max power level since that's about all I dare put into my SA-12 at 15 Hz. That should be pushing it right up to Xmax. For the in-vehicle measurements is pretty much the same setup in my Durango. I put the box against the tailgate with the port firing up, mic was on the passenger side dash. So, on to the first test results. Here is the the plugged port configuration (effectively a 4th order): The frequency response looks pretty consistent across different power levels (which is what we want). To highlight differences, in the measurement software I can offset the measurements, so what I do is I offset the lower power levels so they are equal to the max output (-0 dB) measurement. Ideally the lines will then be all stacked on top of each other. If we are getting any compression (either port compression or power compression) that will show up as the higher power measurements being lower than the lower power ones. Here is what we get: All the lines are stacked up on top of each other well, this is good. Now the large rear port configuration: And here they are with the measurements offset: Overall this looks pretty good, we can start to see the effects of a little port compression between 30 - 40 Hz. You will notice the yellow line (higher power measurement) is a bit below the lower power lines. Probably loosing a little over a dB to port compression at that highest power level. Here is the small rear port config: The offset measurements: With the configuration we can see much more significant losses to port compression. Here is a more zoomed in view: Below 45 Hz you can see at each increasing power level there is a further reduced increase in output. Comparing the highest power level measurement (the red line) to the lowest (the yellow line) there is about 2.5 dB of output that is lost to compression between 30-40 hz. Here is the lower tuned, small port config: The results here are similar to the higher tuned small port config, the port compression doesn't become apparent until a lower frequency due to the lower tuning.
  9. Fi SSD Port Noise Question

    You might get a bit of port noise, but it probably won't be severe. If you are worried about it you could increase your port area a bit.
  10. Triticum's Improved Port Area Calculator

    Just the ported section.
  11. Ported or Sealed enclosure

    A ported box is going to have more output down low around its tuning frequency compared to a sealed box. Just how much more output depends on the parameters of the box, the install, and the sub being used. More output down low may or may not be something you want based on the specifics of your install and how you like your music to sound. Most people around here like the extra output. I try to avoid generalizations like "sealed boxes have better sound quality" or "ported boxes are more boomy". Both sealed and ported boxes can have excellent sound quality, and they both can sound terrible and have boomy, sloppy bass if done poorly. It all comes down to the equipment being used and how the box is designed and implemented. People can't just say "sealed boxes sound this way, and ported boxes sound that way". Its a lot more complicated than that. For my own tastes, I like ported boxes that are relatively small for the size of subs being used and are tuned pretty low. I also carefully pick subs that work well in this configuration. This usually gives a flatter frequency response and good low end extension, but it does come at the cost of some output potential. I am telling you this not because I think small ported boxes are "best", what's right for me may not be right for you. Its just an example of what can be done and how to approach the decision making process.
  12. Ascendant audio chaos 12s box help!!!

    How much power are you going to be running?
  13. So here is the issue. When you put those drivers in the recommended enclosure specs you get a big peak it output right around tuning and not much anywhere else. With a 6th order box you get two tuning frequencies, so you can spread those out and get some usable bandwidth, this comes at the cost of increased enclosure size. What looks decent is a parallel-tuned box with 1.8 cu ft tuned to 32 hz and .8 cu ft tuned to 60 hz, both with at least 20 sq in of port area. This makes for a pretty big box, and they are a pain to lay out.
  14. I played with the numbers a bit. There really isn't anything I can do to get those "subs" to perform as I'd like with the space you have available. If you had more space a 6th order bandpass might work well, but its too big. If you are determined to try a new box, I'd just build it to Skar's recommended specs. 1.8 cu ft tuned to 40 hz with 30 sq in of port area. Output is going to be peaky and will fall off fast below 40 hz, but that's just how its going to be.
  15. I'll play with the numbers and see if I can come up with something. I know you want to use what you have but understand you are asking "how do I make this screwdriver into a good hammer" and the answer for the most part is "you can't". Between the high Fs, low Vas, and low Xmax those aren't really subs, regardless of what Skar wants to call them. It's a shame Skar markets them as such.