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The guy at work is wrong, you don't need a ported box to get the chest hit out of a sub.

I think if you flatten out the low end, and then boost the sub in it's entirety to restore the dB level across the sub range, you'll get the chest punch you're looking for.

It looks like your current tune has a peak at 60Hz. So if you crank up the sub to try and feel the chest hit in the 80-100Hz range, then 60Hz will be distorting. Maybe you're reaching excursion limits? BTW: If you went to a ported box, you'd probably hit excursion limits sooner due to less cone control.

What type of music are you listening to?
 

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Discussion Starter · #22 ·
The guy at work is wrong, you don't need a ported box to get the chest hit out of a sub.

I think if you flatten out the low end, and then boost the sub in it's entirety to restore the dB level across the sub range, you'll get the chest punch you're looking for.

It looks like your current tune has a peak at 60Hz. So if you crank up the sub to try and feel the chest hit in the 80-100Hz range, then 60Hz will be distorting. Maybe you're reaching excursion limits? BTW: If you went to a ported box, you'd probably hit excursion limits sooner due to less cone control.

What type of music are you listening to?
Iiiiiiiinteresting. Guy at work said that the sealed box is keeping the sub from "breathing" and limiting its cooling. He also said I can make a port by just cutting a hole and shoving a carboard roll into it, so I take what he says with a grain of salt.

I listen to a mix, but I do like low bass. Massive Attack, Dennis Lloyd. Nine Inch Nails, some rap, a lot of techno with hard beats, classic rock. A fair mix.

I'll change my PEQ here in a minute and test it out.
 

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What does your eq look like for your subwoofer? Hopefully you arent trying to EQ out a null and causing clipping at those frequencies. Also would double check that your subwoofer coils are wired in phase, I'm sure you already checked that though.
 

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Discussion Starter · #25 ·
🤦‍♂️ Ya, I wouldn't put much faith in the guy from work LOL.

Have you read this yet?

Designed for sealed or ported...explained!

Looking at the T/S specs of the woofer, I think it should do very well in that 0.80cu/ft sealed box you have it in.
Ooooo, interesting read! I'll finish that in a bit.

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I did a cut at 60 Hz, Q 2, -3 dB, then
60 Hz, Q2, -6 dB, then
55 Hz, Q1, -9.1 dB.

I did this on my break so I didn't have time to raise the gain. I'll take a lunch shortly and try.

I thought the specs for the box matched up. To be fair, it is a very big sub and I'm sure the displacement is pretty high. I had to glue an MDF 3/4 spacer ring just so the sub would fit. I'm working with sub-optimal vehicle dimensions for a sub box.
 

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Discussion Starter · #26 ·
What does your eq look like for your subwoofer? Hopefully you arent trying to EQ out a null and causing clipping at those frequencies. Also would double check that your subwoofer coils are wired in phase, I'm sure you already checked that though.
Coils wired in phase? I'm not 100% sure on what you mean. I wired two 4 ohm coils down to 2 ohms....
 

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If your distances are correct, there shouldn't be a need to reverse the polarity on the sub. Any particular reason you did that?

Also, your LPF on the sub looks to be 71.3Hz with a 12dB slope and the mids are set to 108Hz HPF with a 24dB slope. I assume you're following the "Set the HP on the mids above the fs, and then set the LP on the sub 1/2 octave below the HP on the mids" approach?

In addition to flattening out the curve, I'd also try 80Hz, 24dB LR low pass on the sub, and set the polarity back to positive instead of reverse.
 

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Oh, and you shouldn't need the HP filter on the sub with the sealed enclosure ... so you can try disable those as well.
 

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Discussion Starter · #29 ·
As far as EQ'ing out a null, I tried a very small EQ on the mids to get the 180 Hz nul
If your distances are correct, there shouldn't be a need to reverse the polarity on the sub. Any particular reason you did that?

Also, your LPF on the sub looks to be 71.3Hz with a 12dB slope and the mids are set to 108Hz HPF with a 12dB slope. I assume you're following the "Set the HP on the mids above the fs, and then set the LP on the sub 1/2 octave below the HP on the mids" approach?

In addition to flattening out the curve, I'd also try 80Hz, 24dB LR low pass on the sub, and set the polarity back to positive instead of reverse.
It was on the recommendation of another member on here. It was during the course of my initial tune. I'll try it without the polarity flipped momentarily.

Yes. The fs on these speakers I think is exaggerated (they're not good speakers, it's the weak point in my system) at 87. But the 1/2 octave rule of thumb is what I was going for in that setting. The slope was changed from -24 to -12 just in the course of me trying to stop that distortion/overexcursion.

Okay, let's try those settings.

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I'll load this tune and see what happens.
 

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Discussion Starter · #30 ·

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The fs on these speakers I think is exaggerated (they're not good speakers, it's the weak point in my system) at 87. But the 1/2 octave rule of thumb is what I was going for in that setting.
Is the fs 87, or is that the sensitivity rating? What speakers are they?

If it's the 5.25" coax listed in your sig, you might try 100Hz low pass on the sub and ~150Hz or so high pass on the mids if the tune you've outlined above doesn't get you there (after increasing the sub level).
 

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Discussion Starter · #32 ·
Okay, played with some of the EQ (both the in sub range and to smooth out the bumps at 360 and 700), here's what I have:

Joint Light Black Slope Rectangle
 

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Discussion Starter · #33 ·
This is after adjusting the gain up on the sub amp. This is actually about 40% up on the gain now, up from 25%.
 

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Discussion Starter · #34 ·
Is the fs 87, or is that the sensitivity rating? What speakers are they?

If it's the 5.25" coax listed in your sig, you might try 100Hz low pass on the sub and ~150Hz or so high pass on the mids if the tune you've outlined above doesn't get you there (after increasing the sub level).
The fs is 87. My original 4 channel amp was defective and popped my component 5.25s, so they gave me some "loaners" that are NVX NSP525. Entry level coax, definitely not helping anything. Getting those replaced is my next purchase.

Tried shifting the crossovers up to 100 and 150, but it pulled the bass all to the rear, so I'm back to the 80 / 120.
 

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Hmm, it almost looks like the gains are not set correctly on the amps in that last graph. I know you have a null at 180, but that's quite the dip. It looks like the mid/highs amp gain is set much too high when compared to the sub, but you didn't change the gains (except increase the sub), correct?

This was your original graph:

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Which looks pretty good, except for that 180 dip and the sub bass area (peak at 55Hz or so, and overall level too low).

How did you go about setting the gains on the two amps? If you do the multi-meter method, without speakers connected, the sub amp should hit around 38vAC to get 750w @ 2Ohm.

The amp pushing the coax should be around 17vAC for 80w @ 4Ohm.

In terms of the bass pulling to the rear, it may be something you have to live with until you can get some better/bigger mid range speakers in there. If you have to rely on the sub to handle the midbass response area, it's going to localize it a bit.

Curious: When you play just one side (right or left), do you still get the 180Hz dip, or is it only when you play both sides?

And are you using pink noise to generate these graphs, or a frequency sweep?
 

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Discussion Starter · #36 · (Edited)
My editor on here is behaving strangely, sorry for any errors.

There was no gain setting on the 4 channel amp. It just has the "Input Sensitivity" which I set at 4 V to match the RCS output levels of the HU.

As for the sub amp gain I set it by ear, and I don't pretend I did it well. I'm still figuring a lot of this stuff out. I've only briefly read about setting amps using a MM, but I could look for a tutorial and try that with my sub amp on lunch.

I do have my previous tuning saved in TuN, so if I've just gone in reverse I can do undo what I've done so far.

The null exists if I measure where I'm seated, whether I'm playing my mids, my subs, or any combination of mid + sub. I'm using pink uncorr noise using the RTA feature taking a minimum of 12 samples (until the graph stops moving), me sitting the driver's position with the microphone slowly sweeping from ear to ear. If I measure directly at the driver there is no null.

I had the suggestion of hooking my overhead speaker bar (currently disconnected) to a third amp and bandpassing 80 to 200 through them for midbass to counter the null. Interesting idea, though I dislike the loss of localization, but it might be the best way for me to fix that unless I figure out whatever cabin mode demon is the source of it.
 

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Gotcha.

If you look at your last graph:

Colorfulness Rectangle Slope Font Plot


It's not that bad, except everything from 180 down is too low. If you picture everything from 180 below being bumped up 15dB or so, the curve would look great:

Product Rectangle Purple Textile Violet


The changes you made definitely made the sub bass area look better (IMO), as the peak is gone on it and it's left with a nice increasing curve. Now it seems it's just a matter of getting the balance between the two amps correct, and then trying to address that 180Hz null.

Flipping the polarity on one (not both) of the 5.25" speakers may be worth trying. Just play pink noise, and watch the RTA in real time as you flip the polarity on one of them and see what happens. The 180 null may go away, but another may appear somewhere else. In REW, you can reset the averaging as the measurement is being taken, to see the impact of changes.
 

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I just looked at your near field measurements in the other thread, and it seems those 5.25" mids just can't play much below 300Hz with how they are installed.

Colorfulness Purple Slope Font Plot


You can still get the amp gains set correctly for a better balance, but to close that gap from 300Hz to where the sub picks up, I think you have 3 feasible options:

  1. Create some sort of enclosures (or modify the existing enclosures if you already have some) for the 5.25" drivers to extend their lower range
  2. Add some mid-bass drivers to cover this area (like in the sound bar or kick panels)
  3. Raise the sub's LP filter so it plays higher (and live with the localization)
So get the amp gains adjusted for a better balance, and see where you are then. My guess is the curve will be better, with a dip still in the mid-bass region. Then you'll need to make a decision on how you want to address it.
 

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My editor on here is behaving strangely, sorry for any errors.

There was no gain setting on the 4 channel amp. It just has the "Input Sensitivity" which I set at 4 V to match the RCS output levels of the HU.
So on that amp.....

Font Electronic component Musical instrument accessory Audio equipment Electronic device


The "SENS" knobs are the gain settings. You're running from the HU, to the TwK-88, then from the TwK-88 to the amps ... correct? So the gain/sensitivity of the amp should be set to align with the TwK-88's RCA output, not the headunits.

The amp is rated for 75wpc @ 4 Ohm, so you'd want to set the gains on it to hit around 17vAC. (75w x 4Ohm = 300 ... sq/rt of 300 = 17.32). You would do this with the speakers disconnected, playing a test tone with the headunit volume up around 75-80% (or whatever the max level is without causing clipping), and then using a multi meter with it set to AC voltage.

The rest of the amp settings should be set to 4CH input config, and both X-OVER switches set to "FULL".

If the X-OVER switch for the channels driving the 5.25" speakers is set to HPF, this could also explain them not playing much below 300Hz.


As for the sub amp gain I set it by ear, and I don't pretend I did it well. I'm still figuring a lot of this stuff out. I've only briefly read about setting amps using a MM, but I could look for a tutorial and try that with my sub amp on lunch.
If it were me, I'd definitely set the gain on the sub amp using a multi meter. The sub is rated for 750w, and that amp is rated for 760w @ 2-Ohm. So it's a great match up. 750w would be around 38vAC with a 2Ohm load (750w x 2Ohm = 1500 ... sq/rt of 1500 = 38.72)
 

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Discussion Starter · #40 ·
That makes sense, and I feel the sub output is way below what it should be for the power levels I'm working with. It just occurred to me that the trim levels of the sub are turned way higher than the rest of my drivers:

Font Audio equipment Screenshot Rectangle Number


I don't feel like I'm getting any real output in that range, at least not what I should be getting. I didn't think about the trim levels before I started playing with the gain, should I match those closer to the drivers and then try to set the sub amp gain again?


I just looked at your near field measurements in the other thread, and it seems those 5.25" mids just can't play much below 300Hz with how they are installed.

You can still get the amp gains set correctly for a better balance, but to close that gap from 300Hz to where the sub picks up, I think you have 3 feasible options:

  1. Create some sort of enclosures (or modify the existing enclosures if you already have some) for the 5.25" drivers to extend their lower range
  2. Add some mid-bass drivers to cover this area (like in the sound bar or kick panels)
  3. Raise the sub's LP filter so it plays higher (and live with the localization)
So get the amp gains adjusted for a better balance, and see where you are then. My guess is the curve will be better, with a dip still in the mid-bass region. Then you'll need to make a decision on how you want to address it.
The problem with the current 5.25 enclosures is that I'm really limited on options due to Jeep's current design. I'm using these: Amazon.com: Select Increments DPE97025 Dash-Pods (Without Speakers) : Electronics Before this the mids were just floating without any sort of enclosure. Now, these aren't sealed where the wires feed through the enclosures, would adding a grommet and caulk help at all?
 
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