[Focused4door]

That should get, um, interesting. It would be wild to do a car with no subwoofer, and an array of Aurasound NS3 midbasses. That would be a serious skullfuck. These woofers punch way above their size.

You should model the Tang Band neo subwoofers, they have a 3" and 5" that look impressive at least on paper. Not cheap because they are neo magnets, but small boxes and pretty impressive looking. I looked at using one for a sub in a DYI boom box and ended up buying a set of the JBL Control X wireless instead.

 

[SubOptimal]

Question about bandpass midbass.
I'm looking to try something similar with the Dayton ND91-4s.
They model fine until I add in the port resonance.
If I bandpass with the DSP too, will that dampen the port noise?

 

[Patrick Bateman]

Looks impressive, disto seems a little high but did you measure max spl?

I couldn't agree more. I came pretty close to throwing these in the trash before I even hooked them up. Because the distortion IS rather high.

But WOW do they sound fantastic.

I'm really starting to think that reducing distortion may be a fool's errand.

Dunno.

 

[Patrick Bateman]

Question about bandpass midbass.
I'm looking to try something similar with the Dayton ND91-4s.
They model fine until I add in the port resonance.
If I bandpass with the DSP too, will that dampen the port noise?

I can post the STL file if you'd like. The Dayton ND91s are basically a drop-in for this box. I used the AuraSound NS3s largely because they're a couple bucks cheaper. The Dayton ND91 is a shameless clone, and the only real difference is a lower QES and lower LE, which isn't really important for a midbass.

Don Keele tweaked the ND90 and called it the "ND91" for his CBT speakers. But they're both AuraSound NS3 clones.

I have both onhand, they're nearly indistinguishable.

As far as the port noise, check out my measurement, the port noise is fairly well behaved. You could put a little polyfill in the chamber to reduce it if you wanted to. Another option would be to wire an inductor in series.

 

[SubOptimal]

Thanks for the offer Patrick.
Prices here are much the same, but the ND91 better fits my requirements.
It's a touch more efficient, and models as if it will give a bit more usable bandwidth.
It also requires a smaller enclosure, which allows me to use a longer port.
Reason being, I'm attempting to have the enclosure located where the OEM 6.5" would normally be, and route a long port (~45cm) up to the sail panel area.
The easy part is then mating that with an efficient 2-2.5" mid and probably an ND16 tweeter.

Was there any electrical filtering applied when you took those measurements?

This would be ideal...

This would be hopeless

 

[Patrick Bateman]

I think I had a high pass set at 40hz, but that was all the filtering

Note that there's no real need to put the midbasses near the midranges. The frequencies are so long, it's difficult to perceive where they're coming from.

For instance, 200hz is 1.3 meters long.

What WILL affect your perception of the location are the harmonics.

For instance, the 3rd harmonic of 200hz is 600hz. That harmonic is well into the range of frequencies that are easy to localize.

That's one of the beauties of bandpass boxes; they filter out harmonic distortion. At 600hz, the harmonic distortion of my bandpass midbass is well under the noise floor.

Subjectively, my midbass sounds like it's at the firewall, even though it's under my seat. The mid-range is located near the firewall and it 'anchors' the stage.

 

[Patrick Bateman]

Here's a video of the construction.

It's 3D printed, with mortite and fiberglass for constrained layer damping:

https://youtu.be/Ng0M3s0yqcY

 

[Whiterabbit]

Interesting topic, and timely for my pre-planning.

Can you share the volumes and port geometry you elected to use for this project? I would like to duplicate your work in Q4 of this year for a center channel. I've predicted for years this kind of application would be excellent for excessive midbass routed up the door sills into the kickpanel area, however for a compact active center channel located inside the dashboard, I believe a bandpass solution like this represents an excellent solution for low frequency challenges given to us by modern OEM dashboard designs.

 

[thechainrule]

Patrick, I’d love to try out your 3d printed design in my install, would you mind sharing your stl file?

 

[Patrick Bateman]

I probably don't have the file any longer. I can take a look on my NAS, but it's been about three years and two laptops ago. I'll make myself a note to check this week.

 

[Patrick Bateman]

Here's some pics of my new bandpass midbass enclosures for my car. They use an AuraSound NS3 woofer, which is currently on sale at Madisound.

The 'gap' in the enclosure is just there so that I can assemble it. Basically i screw the driver in, I cover the entire enclosure in mortite, and then I wrap it in fiberglass. This is to create a constrained layer damping enclosure.

If you'd like to print this, I uploaded the STL files here:

A Collection of 3D Printed Things - diyAudio

I've noticed that people have been printing out some of my waveguides, even though I never managed to actually finish a project. I've probably made fi

www.diyaudio.com

 

[EricP72]

If you'd like to print this, I uploaded the STL files here:

A Collection of 3D Printed Things - diyAudio

I've noticed that people have been printing out some of my waveguides, even though I never managed to actually finish a project. I've probably made fi

www.diyaudio.com

I know this is an older thread, but I'm looking at doing an under the midbass. Have you come across any passive or powered under the seat subwoofer setups that work perfectly for midbass say 80hz-200hz and doesn't give away its location by excessive vibrations through the seats? I was thinking about the focal Isub twin or the JBL FUSE.

 

[Focused4door]

On paper the JBL looks better

I am curious if the JBL fuse can be tuned higher by removing weight from the passive radiator if you are only using it as a midbass.

It may not have added mass, or it may not be removable though. Lots of products are hard to even take apart depending on the design as well.

 

[EricP72]

On paper the JBL looks better

I am curious if the JBL fuse can be tuned higher by removing weight from the passive radiator if you are only using it as a midbass.

It may not have added mass, or it may not be removable though. Lots of products are hard to even take apart depending on the design as well.

Now that would make it the front runner if the PR can be tuned

 

[Patrick Bateman]

JBL Fuse looks like a no-brainer:

JBL Fuse compact 8" Under seat subwoofers -...

I just came across these compact 8" enclosed subwoofers from JBL/Harmon and was so entrigued I bought a pair for under seat midbass. They are "subwoofers" not a true midbass/midwoofer like I was looking to put under my seats but basically I can only fit shallow 6.5" mids in my doors so while my...

www.diymobileaudio.com

The key to the setup that's described in this thread, is that the use of multiple midbasses fixes the fundamental problem of midbass in the car.

At home, we can put a 7" woofer into a vented enclosure and we can get bass that's quite good. I recently measured my Behringer two-ways, and they play down to 30Hz in my living room! And they sell for about $300 a pair. That's just ridiculously good performance for the money.

In a car, it's a struggle to get a 7" woofer to play down to 60 or 70hz.

Basically, the sound from the RIGHT speaker is nullifying the sound from the LEFT speaker, and vice versa. This is because the interior of your car is about five feet wide.

112Hz is ten feet long.

56Hz is twenty feet long.

So when your left speaker plays 112Hz,when it arrives at the RIGHT speaker it's 180 degrees out of phase, creating a null. When you left speaker plays 56Hz, when it arrives at the RIGHT speaker, it's 90 degrees out of phase, creating a dip.

So you have this range from 56Hz to 112Hz, where your left and your right midbass are fighting each other.

That's the entire point of this thread: If you spread your midbasses out, you can get away with midbasses that are much MUCH smaller.

No exaggeration: when I was using this scheme in my car, I was using two 3.5" woofer per side, and it sounded "punchier" and "smoother" than using a single eight.

So the JBL Fuse looks like a no brainer. But DO NOT do this experiment with one midbass per side, that defeats the entire purpose. Use two per side, or more. I had one midbass under my seat, and one under the dash, per side. If you want to get fancy, you can align their outputs using DSP.

Even without DSP, it will sound better than you can imagine, because the fundamental issue with midbass playback in a car is that the geometry is all wrong. Best way to fix that would be to get a car that's ten feet wide, but that's impossible. Second best way to fix it is to distribute the wavefronts by adding a second midbass per side.

Also, please note that you DO NOT want them side by side.

I know that it seems like that would be a good idea; that you'd want them close because it will "sound better."

But it won't. The entire problem here, is that the left speaker is fighting the right speaker, and vice versa. If you put two midbasses side by side, they simply act like one giant midbass. You want them at least one quarter wavelength apart, at the upper limit of their output.

IE, if you have two midbasses per side, and each midbass is playing up to 250Hz, you would want them about 13.5" - 18" apart.

One midbass in the door, and one midbass under the seat is a good combo. Or one midbass in the door, and one under the dash. When I did it, I used the same midbasses for my pair, per side. But you could probably mix midbasses without a lot of downisdes. Such as having one JBL Fuse under the seat, and something different in the door, and they're wired so that they get the same signal.

If you REALLY want to go crazy, there's also a lot of good reasons to have one playing louder than the other.

This is about to get confusing, so I apologize in advance:

As noted earlier in the post, the reason it's hard to make midbass in a car is because of geometry. Basically, your right speaker is between 90 and 180 degrees out of phase with your left speaker in the octave between 60 and 120Hz. The exact frequency depends on the width of your car, but 60-120Hz is a safe bet, give or take about 15%.

Andy from AudioFrog published this measurement of cabin gain in various cars, and you can see a consistent dip at about 60Hz. The dip due to cabin gain isn't the same dip that midbasses experience, but the idea is similar.

At about 110-130Hz, you get a really deep null, as much as 10dB. To put that in perspective, a TEN INCH WOOFER is about 10dB more efficient than a typical THREE INCH WOOFER. So that dip is REALLY bad. It's the reason that 7" woofers sound anemic in a car, and dynamic in a home.

If you are going to put two midbasses on one side of your car, and two on the other, ideally they should have the exact same frequency response and they should be carefully delayed so that they arrive at the same time, despite their disparate locations.

But if you're like me, and you like to tinker...

Keep in mind that it doesn't take a lot to fill in that trough from 60-120Hz. If you want to go gung ho, put a midbass under your seat, and put one in the door and tune the heck out of them. That is ideal.

But if you want to tinker, you may find that even a SMALL additional midbass can offer a lot of bang for the buck. Because the fundamental problem here is geometric. So an additional midbass, located about 13.5"-18" apart, will go a long way even if it's not playing 100% as loud.

Here's the math:

Let's say we have a woofer in your left door, and it's playing 100dB at 60Hz. We have a woofer in your right door, and it's playing 100dB at 60Hz. The cabin is 4.7feet wide. This means that at 60Hz to 120Hz, your left and your right woofer are between 90 and 180 degrees out-of-phase with each other. This means you're losing between 6 and 94dB of your output at these frequencies, making the midbass sound very anemic. If you add an additional midbass, playing at 94dB, it will significantly boost the levels even though it's "only" playing 94dB. It's getting a small fraction of the power, but it's reinforcing these frequencies significantly, because there's a frequency where your left and your right are perfectly out-of-phase.

Besides making the midbass sound "punchier", it also sounds subjectively "smoother" to me. This is only logical; in the three octaves from 60 to 500Hz, there's a tremendous amount of reflections in our car. It's a really ugly range where the wavelengths are long enough that they're completely omni. (IE, there's no reason to "aim" a midbass.) But the wavelengths are ALSO short enough that the geometry of the car is wreaking havoc. (If the cabin of a car was 4X as big, what I describe wouldn't be nearly as much as a problem. Jon Whitledge famously used a Sprinter Van, due to these issues I describe.)

IE, if you're limited on space, or you just have a 4" or a 5" woofer laying around in the garage, you might get good results by just fabricating a sealed enclosure and sticking that under your seat, playing in unison with what's already playing in your car doors. Or put it under the dash.

And you can get a 4ohm resistor and wire it in series, to reduce the voltage that's going to the additional midbass. The idea being that you'll reduce how much power it gets. (This assumes that your existing midbasses can handle about twice as much power.)

The idea here, is that you can tinker with this, without making the commitment to tearing up your car to figure out where two midbasses would be located, ideally. If you use a resistor to drop the input voltage to the second midbass, be sure to to get a decent one off of eBay or Parts Express. Or get a couple of 10W resistors and wire them in parallel.

 

[Jheitt142]

ok. So I find this post very relevant to me right now. I'm in the stages of just getting my wiring runs together and while i have my sub, and my widebands i have three potential midbass candidates sitting here.

2 - 6.5" 2ohm CDT drivers
2 - 6.5" 4ohm silver flutes
2 - Dayton audio dual 8ohm 8" subs, but having used them sealed i think they'd be great for mid bass duty Dayton audio 8" subwoofer

I have been mulling over my choice here endlessly, even considering things like mixed mono.

the CDT's are spec'd so that a box would be a pain to fit. the silver flutes however would be great in a small enclosure. I've also modeled the 8" in as little a 0.22 and the response in the 80 and up range is great. im pretty low on power in this install. but at 2ohms i do have a rated 80RMS from my good old sounstream. so i could run the flutes and the 8's together on the same channels. just put one set in the doors and the other on the floor

From what im reading here i could achieve much greater output splitting up that power with 4 drivers vs feeding it all to the 2 CDT drivers.

 

[Focused4door]

I have wondered if the next step to this is to add a band stop filter to the wider midbass at the null frequency, and play the narrower located midbass full range of the midbass passband. No point pouring power into a null.

 

[EricP72]

So then by Bateman suggestion, I could purchase 2 JBL Fuse and run 1 set under the front seats, 1 set under the dash, and keep the door midbass drivers as is. The doors would be the main output with the others being used to supplement the output and nullify any voids or dips thus not really needing more than say 100watts per "box". So I guess the next part is finding a 4 channel amplifier that has a bass knob that way I can level match on the fly without using a dsp channel. Am I correct or am I over thinking the process?

 

[Bikey]

What frequencies would you send to the Fuses and which would you send to the door speakers? Depending on what they are playing, you may no longer need the door speakers.
If your DSP has no unused channels, you could use something like a Mini-DSP, to handle the 4 Fuses.

 

[Patrick Bateman]

So then by Bateman suggestion, I could purchase 2 JBL Fuse and run 1 set under the front seats, 1 set under the dash, and keep the door midbass drivers as is. The doors would be the main output with the others being used to supplement the output and nullify any voids or dips thus not really needing more than say 100watts per "box". So I guess the next part is finding a 4 channel amplifier that has a bass knob that way I can level match on the fly without using a dsp channel. Am I correct or am I over thinking the process?

Three 8" midbasses will be way more than anyone would need.

I used 3.5" midbasses and it worked great.

Keep in mind that the null that's created by the left and right speaker being out of phase is REALLY deep - as much as 10dB.

That's basically the difference between a ten inch woofer and a three inch woofer!

The null basically takes your 6" midbass in the door and makes it sound like a puny little 2" driver.

You can demonstrate this by going to any Best Buy - there are computer speakers with 3" and 4" woofers that have punchier midbass than what a lot of people have in their cars.

If it were me, I wouldn't use three midbasses to start with, I would use two. Certainly nothing wrong with using three, but I'd start out by just experimenting with a single additional midbass.

When I first started messing around with this, I just bought a set of Cambridge Soundworks computer speakers off of Craigslist. It was basically a way for me to experiment and see what locations worked well, and what didn't. And you can get the entire set for about $20. These cubes measure ridiculously well, they're basically flat from 100Hz to 20khz. They can't handle a lot of power, so you'll want to put a resistor inline to reduce how much voltage they're getting. 4ohms is a good start.

Or wire them in parallel with your midbass and just be careful not to do overdo it. Ten watts will get you about 95dB.