Help with box design

[mdillon 10+ year member]

I haven't been on this forum in over a decade...

Im looking for someone to help me with a box design for a classic car, preferably bandpass. It is for 2 15s. The ported box currently in the car does not perform well with the trunk lid closed. If anyone can help, it would be appreciated.

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[Jimi77 Premium Member]

I haven't been on this forum in over a decade...

Im looking for someone to help me with a box design for a classic car, preferably bandpass. It is for 2 15s. The ported box currently in the car does not perform well with the trunk lid closed. If anyone can help, it would be appreciated.

Sounds like cancelation, in which case a bandpass won't help unless you vent it directly i to the cabin.. Have you tried turning the enclosure around? Pics if trunk with enclosure in it. What car? Does it have holes venting from the trunk into the cabin?

 

[huberoy123 10+ year member]

I haven't been on this forum in over a decade...

Im looking for someone to help me with a box design for a classic car, preferably bandpass. It is for 2 15s. The ported box currently in the car does not perform well with the trunk lid closed. If anyone can help, it would be appreciated.

What kind of car?? Sounds like have another issue. I have fold-down rear seats so I am able to fold them so the sound can enter the cabin. If yours don't fold down, you may be able to modify your rear shelf to accomplish this.

 

[mdillon 10+ year member]

Sounds like cancelation, in which case a bandpass won't help unless you vent it directly i to the cabin.. Have you tried turning the enclosure around? Pics if trunk with enclosure in it. What car? Does it have holes venting from the trunk into the cabin?

65 deville. The port is vented into the cabin, the subs face the rear. There is about 48x16 open space between the rear seat and trunk to vent.

I was talking with other classic car owners that have ran into the same issue and they recommended bandpass vented directly into the cabin.

 

[mdillon 10+ year member]

Here are pictures of the car and trunk

 

[shredder1 10+ year member]

The whole way you have the current enclosure is your problem, cones in the trunk with ports in the cabin... I've seen this type of issue happen a lot. Some people actually advise this is a good way to install an enclosure... haha.

Yep... the 4th vented into the cabin is the way to go but realize a pair of 15's (AB?) are going to need a far bigger enclosure than you currently have and probably somewhere around 100in2 of port to do it right.

This a 4th for 2 Resilient Sounds Gold 15's, I am fairly certain its a little bigger than something ported would be. What works for your particular subs may be different but I hope this gives you an idea of the size difference.

Fyi... even having a different ported enclosure done all in the trunk with cones and port into the trunk would be an improvement over what you currently have.

 

[huberoy123 10+ year member]

Here are pictures of the car and trunk

Beautiful car.

 

[Jimi77 Premium Member]

Here are pictures of the car and trunk

Cool car. 4th order bandpass vented into the cabin is the way to go. You current design looks cool, but you've walled off the subs from the cabin.

 

[Buck 5,000+ posts]

Your box may be so tall and wide the bass can't get into the cabin.

 

[Buck 5,000+ posts]

I used to install on a decent amount of old schools, they can be tough despite their large trunks. You might want a really short box with subs firing up, like a box that takes up entire lower half of the trunk instead of front half, you can make a port firing up too.

 

[shredder1 10+ year member]

Your box may be so tall and wide the bass can't get into the cabin.

Ya' think?

Plus the trim panels separate the subs from the cabin and to make it worse the ports are like 1/4-1/8 wavelength away from the cones with the configuration and delay. Even a normal ported setup would perform better if the trim panels were fighting a set of 15s /w/ the ports on the baffle. Cancellation comes to mind. A complaint of "with the trunk closed" means he's reaching. Been there... simple fix actually even without going 4th order. Install and acoustics over beauty panels.

 

[Buck 5,000+ posts]

Ya' think?

Plus the trim panels separate the subs from the cabin and to make it worse the ports are like 1/4-1/8 wavelength away from the cones with the configuration and delay. Even a normal ported setup would perform better if the trim panels were fighting a set of 15s /w/ the ports on the baffle. Cancellation comes to mind. A complaint of "with the trunk closed" means he's reaching. Been there... simple fix actually even without going 4th order. Install and acoustics over beauty panels.

That box is ported? Ah my bad I just looked at the pics, got lazy.

Yeah you never want to fire your port and subs into different airspaces because distance is tuning. Basically the bass from the subs in the back is changing phase too much before it meets back with the port in the front because of the extra long distance, but also because the trunk itself is going to act like an enclosure and the small airspace pathway the subs have around the box to reach the cabin air is like a port itself. It's like a parallel 6th order basically but tuned badly or not tuned specifically. The big trunk is a ported chamber and the smaller cross sectional area where the trunk air has to pass into the cabin acts as a port itself, basically, so you're getting an untuned resonance (causing cancellation) there in between the sub cones in the trunk and the port air in the cabin.

Really you want the subs and the port to be as close to each other as possible to eliminate cancellation from my understanding. Just a general statement. You never ever ever want to put the port and subs firing into different air spaces, you always want them firing into the same airspace, like you want them all firing into the trunk or all firing into the cabin.

 

[Buck 5,000+ posts]

I mean idk how open the trunk pathway is into the cabin, just saying a lot of times the trunk pathway (how waves flow through the trunk and cabin, front to back inside of vehicle) is a lot more surface area than the surface area of how it connects to the cabin and those subs being in the trunk means when they compress the air and the cross sectional area shrinks before the trunk sub air enters the cabin then that's a like restriction that'll cause resonance itself.

 

[shredder1 10+ year member]

That box is ported? Ah my bad I just looked at the pics, got lazy.

Yeah you never want to fire your port and subs into different airspaces because distance is tuning. Basically the bass from the subs in the back is changing phase too much before it meets back with the port in the front because of the extra long distance, but also because the trunk itself is going to act like an enclosure and the small airspace pathway the subs have around the box to reach the cabin air is like a port itself. It's like a parallel 6th order basically but tuned badly or not tuned specifically. The big trunk is a ported chamber and the smaller cross sectional area where the trunk air has to pass into the cabin acts as a port itself, basically, so you're getting an untuned resonance there in between the sub cones in the trunk and the port air in the cabin.

Really you want the subs and the port to be as close to each other as possible to eliminate cancellation from my understanding. Just a general statement. You never ever ever want to put the port and subs firing into different air spaces, you always want them firing into the same airspace, like you want them all firing into the trunk or all firing into the cabin.

Its really the absolute worst way to do a ported in a trunk, cones in the trunk all trimmed in /w/ ports firing into the cabin. One local expert tried to get creative for looks and did something similar /w/ 2 Zv5-10's in a Camaro. After he threw some more bux and time at it hands got thrown up in the air. Mind you this was Zv5-10s on a Sundown 6K so tensions were apparent over the install once I weighed in.
Simple fix...

Some parcel shelf work where he originally tried to port it into the cabin really let it open up. But make NO mistake it was a gorilla back there. Before it was mildly interesting without lows. I was unimpressed. We fired the thing up after the change and his garage door piledrived the roof and rear window. He was so happy he didn't care
Baltic Birch and some compromise actually put a set of Zv5-10's in a newer model Camaro once upon a time. On 6K no less... it was epic

 

[Buck 5,000+ posts]

Its really the absolute worst way to do a ported in a trunk, cones in the trunk all trimmed in /w/ ports firing into the cabin. One local expert tried to get creative for looks and did something similar /w/ 2 Zv5-10's in a Camaro. After he threw some more bux and time at it hands got thrown up in the air. Mind you this was Zv5-10s on a Sundown 6K so tensions were apparent over the install once I weighed in.
Simple fix...

Some parcel shelf work where he originally tried to port it into the cabin really let it open up. But make NO mistake it was a gorilla back there. Before it was mildly interesting without lows. I was unimpressed. We fired the thing up after the change and his garage door piledrived the roof and rear window. He was so happy he didn't care
Baltic Birch and some compromise actually put a set of Zv5-10's in a newer mosel Camaro once upon a time. On 6K no less... it was epic

I've seen this exact mistake before in person on an old school Chevelle when I was younger, I didn't design it. I was just checking it out. I was just there to actually measure my SPL. I couldn't explain it then why it was bad but I just knew that I shouldn't do that. Really if anyone studies tapped horns and gets into that type of mind state it makes understanding these things easier. People really have to remember that a subwoofer is just an oscillator. The enclosure itself is actually the musical instrument, much more so than the subwoofer is. Basically, when you're doing boxes, you just want an adequate enough subwoofer oscillator to energize your wind instrument which is the enclosure. I think people kinda look at it from a backwards perspective sometimes. I mean it's easy because sound's not always intuitive. You gotta study it for a little while. I definitely didn't know this stuff when I started.