In car performance of my sub.

[Deer Killer]

Infinity Kappa 10.1d at 2 ohms on a sony xm-400p5 400/800Watts. 3/4 MDF sealed enclosure (.75 cu ft) with a good amount of polyester fiberfill. Mounted facing rearward in the trunk.

 

I got rid of my bandpass boxes to get a smoother curve... but this is one-note bass.. I guess it's great if you like hip-hop, because that 40-50Hz is really loud!

 

Edit - fixed with Best Buy LOC and Audiocontrol EQT, look on page 2.

[agctr]

Hmm just make sure there are not rattles as there is nothing worse when a car passes you and u hear the boot rattle, sounds wrong. Adam.

[Th3Franz]

You sure your box is well-sealed? That's a really weird response curve for a sealed box...

[Deer Killer]

Yeah.. I'm pretty sure the cabin response has a lot to do with it. It mellows out a bit if I have the doors open. (not much) Just the carpeting made a very tight seal on the sub, I don't feel any leaks. Are you sure a leak would cause this type of response anyway? It's possible that I have a really high low-cut on the stock head unit, but I haven't heard that from anyone else. I guess it would make sense if the stock head had a low cut around 35Hz, and added to the amp's infrasonic filter it could make for a fast roll-off. According to infinity's plots that hump should extend down another 20Hz or so :)

[John M]

I wouldn't be surprised to find that the stock head unit's response tapers off the bass to keep the stock speakers from launching out of their baskets. I assume that graph is an in-car measurement. What about putting that box in another car and see if you get the same results, or perhaps run another source into your amp via long RCA cables and run the test again.

[AreEyeSeeKay]

[quote name='Th3Franz']You sure your box is well-sealed? That's a really weird response curve for a sealed box...[/quote] That would be a wierd response curve for a sealed box in an anechoic chamber, but in-car its normal.

[Th3Franz]

[quote name='AreEyeSeeKay'][quote name='Th3Franz']You sure your box is well-sealed? That's a really weird response curve for a sealed box...[/quote] That would be a wierd response curve for a sealed box in an anechoic chamber, but in-car its normal.[/quote] True I forgot to account for the resonant frequency of the car itself.

[Th3Franz]

Hm, looks like the SPL peaks at around 45 Hz, give or take a couple. Well now I now where I want to tune to.

[Deer Killer]

[quote name='Th3Franz']Hm, looks like the SPL peaks at around 45 Hz, give or take a couple. Well now I now where I want to tune to.[/quote] Yeah, the excel chart didn't come out quite right. The peak data point is 50Hz. (it is probably not good to assume it's a fit curve between 40 and 50Hz) Btw I ordered a Navone Engineering NE-8V special order with no bass/treble boost, and a AudioControl EQT 1/3 octave 30 band mono equalizer. It has an adjustment for every sample point on that graph except 20. I hope to get a flat response to 25Hz, we'll see what happens at 20, the LOC has a 20Hz subsonic filter as well, that can't help much :) I am curious about the HU so I will probably run another source to it, with my oscilloscope as well because who knows if my tone generator (dell laptop :D) can actually reproduce that anyway. But if the new toys fix it, I'm good :)

[Th3Franz]

A linear response to 25 Hz should be plenty, I think. I don't think there would be much of a difference between 20 Hz and 25 Hz, unless your sub-woofer is huge.

[John M]

Just remember - a flat response plot rarely results in the best sound to the ear. Judging by your choice of gear, you probably already know that :)

[mcchicken]

Can you post the T/S parameters for that sub?

[Deer Killer]

[quote name='mcchicken']Can you post the T/S parameters for that sub?[/quote] [url]http://manuals.harman.com/INF/CAR/Boxes%20and%20Parameters/P10.1d_f.pdf[/url]

[Boostjunkie]

I modeled a box on WinISD, and for the flatest response it came up with a box right about 1 cu.ft. You mentioned that your box is stuffed with fiberfill so it should have the dampening of a slightly larger box, but obviously you are experiencing a sizeable resonance. If you are after flatter response, and can sacrifice a little output and efficiency, you might want to look into building a new, larger box, maybe even a little bigger than 1 cu.ft.

[Deer Killer]

[quote name='Boostjunkie']I modeled a box on WinISD, and for the flatest response it came up with a box right about 1 cu.ft. You mentioned that your box is stuffed with fiberfill so it should have the dampening of a slightly larger box, but obviously you are experiencing a sizeable resonance. If you are after flatter response, and can sacrifice a little output and efficiency, you might want to look into building a new, larger box, maybe even a little bigger than 1 cu.ft.[/quote] eh? I did the same and I got ~17.5 liters = ~ .62 cu ft. It already contains parameters for the sub though they slightly disagree with the pdf, it only made a few percent difference in the size of the box.

[Boostjunkie]

Sorry. I picked the wrong model sub. I actually plugged in the T/S parameters off the PDF and it came back with 12.6L, which is .44 cu.ft. :o Honestly, you are currently running a box that is more than large enough and by itself should not be giving you the response that you are seeing. I guess the Legacy just exhibits a strong resonance in the 40-50 hz area. My only other thought might be your filtering for your front and rear stage speakers. If they are playing full bandwidth, that might be part of it. You might want to try reversing the phase of the sub. If that bump turns into a dip, then you know you need to run a low cut on your satelites.

[Deer Killer]

The saga continues... The EQT works as promised. The new weakest link the the NE-8V from David Navone. He was really nice and removed the 2db bass and treble boost (40Hz, ouch) for free. But the high-pass filter is just too much. High pass in HU, high pass in EQT, high pass in amp, and high pass in the LOC.. Check out the response curve just going through the NE-8V alone!! the EQT compensates. 25 and 31.5 set to max +12dB, 40 to ~-8dB, 50 -12dB, 63 to -12dB. Didn't tweak the upper end to much (i.e. 100Hz, my least favorite frequency )

 

It's better (listenable) because the huge drop right after 40Hz is gone, but it's really not what is optimal with the EQT.

 

Now what? Open up the NE-8V and see if I can remove the high-pass? I really don't want to mess with it outof the box though. It may be for sale soon.

[Deer Killer]

Problem solved! I'm going to recommend against using the NE-8V for a subwoofer, look at the response compared to the crappy $23 line out converter I picked up at best buy! I had to turn down 25/31.5Hz because the response was so good!

 

Now the biggest problem is getting rid of the rattles 25Hz @110dB really lets you know what isn't securely fastened

 

After a rough adjustment this is what I get:

(edit) slight error, corrected.

[BoxerGT2.5]

[quote name='Deer Killer']Problem solved! I'm going to recommend against using the NE-8V for a subwoofer, look at the response compared to the crappy $23 line out converter I picked up at best buy! I had to turn down 25/31.5Hz because the response was so good! Now the biggest problem is getting rid of the rattles :D 25Hz @110dB really lets you know what isn't securely fastened :) After a rough adjustment this is what I get:[/quote] 110 dB....oh your gonna be seein me in comming years.. hehehe..j/k. Good to see you solved the prob. Nothin better than enjoying good sound in you ride.

[Th3Franz]

I got the best Stinger LOC for about $35 online to use with a sub amp. I won't get around to installing everything for awhile, though.