dual mid bass

[preston]

I run dual 7" in my truck in a sealed box, but they are very close together, the flanges are only about 2" apart ( so center to center would be ~9"). Either way it sounds great and I have very little nulls in my midbass response.

I'm thinking of doign the same thing in my car but in this case the two 7" center to center would be more like 16" apart.

I think I have read, and from what I know of theory, that I risk getting some weird modes/cancellation. I would be playing 80-250, no higher.
And no I don't have the channels to run them independently they would be wired in parallel and on the same phase/timing.

Its easy to say just try it, but we are talking 8-10 hours of having to redo fabrication if it doesn't work out, so just trying to think it through.
I imagine there is some "math" that tells me where this might become a problem. Advantages are cone area without the required depth of a big speaker, and possibly rmoving the standard mid bass null most cars have. No need to touch base on ohms or power I have that figured out.

The other option is a single 9.5" driver which I guess by all considerations would be superior. Except for the "giant speaker exploding out of the door and hitting your leg" part.

[chithead]

Very interesting. I'm wondering about dual mid bass, but with more space between the woofers.

[preston]

Here is my truck box. The Dayton woofers I'm using are actually quite nice - Only 2.9" deep and recommended enclosure is only 0.2 ft3. https://www.parts-express.com/dayton...8-ohm--295-398
Every spec on them looks good even the excursion is pretty good for a small woofer and they are cheap, but of course you have to buy 4 of them so not so cheap after all.
I cheated and put two of them in a 0.23 box, so Q is very high but still sounds good althoug hthey roll off pretty good after 80Hz. This Winter I would like to go back and put in a small aperiodic port I think that would make a big difference. Everytime I've put a membrane in a "too small" box it always sounded better.

Main reason I did it was because those giant truck doors sounded like ass with a normal IB woofer no matter how many tons of dynamat you applied. Now I will never put a woofer in bare door again.
(Box was painted with undercoating spray before final install)

[chithead]

Not bad at all! So you added a piece to the panel next to the factory grille, into the pocket, so now there are two grilles? Very creative!

[preston]

Yup. Biggest problem with door boxes is making them look nice. I consider it a win that no one has ever noticed or mentioned them they blend in pretty well.
You see how tortured the back of that box is though in order to fit as tight as possilbe against the various window rails and stuff. Also the weird "foot" extension, all were efforts to grab as much airspace as possible.
If I had been willing to get ride of my door storage pockets I could have made a plenty big box.

[geolemon]

If you are concerned about midbass nulls and breaking them up... the further apart, the better.

If you are cutting them off pretty low, not using them for midrange, they really won't screw with your imaging. You'll have unequal pathlength distances to your ears (even factoring in all the reflections that occur in the car that cause the midbass nulls to begin with) to break up the midbass nulls for sure. I suppose it's possible to get them at too much of an offset from one another that you could have them cancelling with each other - that would be something to be concerned with, but we're still talking about reasonably long wavelengths here. You could always lock into the front door locations, then - what's the other location? Under the front seats? You shouldn't have any issues, just more bass. "Try it before you buy it" as they say. Mock them up temporarily and listen.

In my Civic Hatchback, I have front and rear door locations - I'm going to use those for midbass. They are pretty close to equal in direct pathlength distance to my ears, but should help break up/fill in any cancellation nodes.
Even with the factory speakers, it has decent bass response, so I have the easy way out on trying it first.

[preston]

Interesting.

IN this case I was just concerned about 2 drivers in a door box in the same door, so only 18" apart center to center (dual 7" woofers). And i never run my woofers past 300 anyway.
In this case it would also have been impossible to just "try it" because of the fab effort involved. In the end I just finished it with a single 9.5" woofer. The dual 7" was a backup plan as I thought the 4.75" deep woofer might protrude ridiculously from the panel/door box. Thankfully it came out pretty good. Initial testing was very positive too, with only one real null all the way up at 320, above my xover point. We'll see what happens with the passenger side and when they play together.

I actually haven't had much problem with mid-bass nulls even though I've read that almost all cars have problems around 180. Perhaps because my truck has dual mid-bass drivers or because its a truck, and my Cadillac had no center console whatsoever. But the new car is more typical and has a big tunnel and console yet so far measures well, left side anyway. Now just another quick 40 hours of work to copy the box and build it on the passenger side.