4th Order Bandpass. 8" woofer

[Bobbytwonames 5,000+ posts]

My friend wants a good sounding system.
He wants an 8".

I choose:
DD608. 1800 wats peak. FS 38 HZ.

I have plans for a Bass Reflex. I don't have plans for a 4th order. But at the worst I could buy plans, $100.

I have Winisd-
But having issues with adding a new driver: DD608.

Anyone think the end comparison is not enough to go through the growth of building a 4th-Order?

I really want to grow as a DIY builder into Bandpass.

Any opinions??


View attachment 43074

Run it with one 3" aeroport and see what happens. That tune is a little high.

 

[Jake321]

Don't use a 2 inch aero for an 8 especially not a high excursion 8. 3inch minimum. You'll end up with a lot of port noise. Aeros should be 7-14in² per cube of airspace.

In 1.3cubes you nearly require a 4inch port.

And no I don't think shoving a 608 will gain you anything unless you know the cabin gain and couple with it to make a massive spike or move tuning of the box to extend the response curve

Do you think a 4" Port single would work?

I'm going to be shoving because I like the way it hits. (Polar-inverted).
Not sure if it's bad for the Sub?

It's been a year of it with my personal 712 shoving.

 

[Jake321]

Run it with one 3" aeroport and see what happens. That tune is a little high.

Can I use a 4" Port?

Any of these designs look better? With a single 3" or 4" Port?

Picture:
1, 2, 3?

 

[winkychevelle 10+ year member]

Can I use a 4" Port?

Any of these designs look better? With a single 3" or 4" Port?

Picture:
1, 2, 3?

And yes you can use a 4inch port in 1.3cubes at 16 1/8" it'll be tuned to 38hz

I mean any of those will work. You ideally want the port exit to be some distance from the sub. I'd look toward #3 if you want to do external port and inverted sub. I don't like doing external and inverted because it limits the direction I can turn the box. You may find the the sub box may sound better pointing a specific direction or at a certain distance from the hatch or trunk wall

 

[Jake321]

And yes you can use a 4inch port in 1.3cubes at 16 1/8" it'll be tuned to 38hz

I mean any of those will work. You ideally want the port exit to be some distance from the sub. I'd look toward #3 if you want to do external port and inverted sub. I don't like doing external and inverted because it limits the direction I can turn the box. You may find the the sub box may sound better pointing a specific direction or at a certain distance from the hatch or trunk wall

And yes you can use a 4inch port in 1.3cubes at 16 1/8" it'll be tuned to 38hz

I mean any of those will work. You ideally want the port exit to be some distance from the sub. I'd look toward #3 if you want to do external port and inverted sub. I don't like doing external and inverted because it limits the direction I can turn the box. You may find the the sub box may sound better pointing a specific direction or at a certain distance from the hatch or trunk wall

Thanks!!

Thinking 3" is half the length of 4", and lower: 35HZ.
35HZ

 

[Jake321]

Here's the (End Result) of the (design process).

I think it'll work really good for lows!

But having issues adding a new driver (608) to the software... Eye Balling.

 

[winkychevelle 10+ year member]

I would do a 4inch aero personally vent air speeds far exceed the 40m/s max with the 3inch port. They even exceed it with the 4inch port once your exceed 1000w.

At 1000w and a 4inch port flared on both sides you are sitting just below 40m/s so you shouldn't get port noise it's only 16-17inches or port length for 38hz

 

[Bobbytwonames 5,000+ posts]

I would do a 4inch aero personally vent air speeds far exceed the 40m/s max with the 3inch port. They even exceed it with the 4inch port once your exceed 1000w.

At 1000w and a 4inch port flared on both sides you are sitting just below 40m/s so you shouldn't get port noise it's only 16-17inches or port length for 38hz

I've talked about port speed to multiple people and they look at me like I just ran their dog over. How do you figure port speed when every song is different and most likely at different volumes and power levels?

 

[winkychevelle 10+ year member]

I've talked about port speed to multiple people and they look at me like I just ran their dog over. How do you figure port speed when every song is different and most likely at different volumes and power levels?

Well you calculate on worst case scenario max power across the whole bandwidth.

This is the 608d2 with both a 4inch port (tall peak) and 6inch port on 1800w which the power is unrealistic but lowering the power only lowers the peaks.

This would be at the more reasonable 1000w and the colors swapped because I'm an idiot and didn't start from scratch

 

[Bobbytwonames 5,000+ posts]

Well you calculate on worst case scenario max power across the whole bandwidth.

This is the 6.8 with both a 4inch port tall peak and 6inch port on 1800w which the power is unrealistic but lowering the power only lowers the peaks.View attachment 43110
This would be at the more reasonable 1000w and the colors swapped because I'm an idiot and didn't start from scratch
View attachment 43111

What velocity is the best? Why not just go 12 sq. inches per cubes net and move on. I bet I have a shitt load of port velocity. 43-¾" of port with 3.69 cubes net on a Sundown SIA3500.

 

[winkychevelle 10+ year member]

What velocity is the best? Why not just go 12 sq. inches per cubes net and move on. I bet I have a shitt load of port velocity. 43-¾" of port with 3.69 cubes net on a Sundown SIA3500.

You might, and you might hear it or you might not. 12in² per cube in a slot port is on the small side and is best kept for low xmax subs. The higher the xmax the more port area you need. It varies subs to sub and by different power levels.

all of this can me calculated. Generally 40m/s is what you want to stay under. My last 3.31 at 36hz with 2 4inch aeros was at like 45m/s and I didn't hear the ports.

In a trunk port noise might not be heard. Behind the seat of your truck it might be muffled enough that you don't care. Or you vehicle might just me loud enough with road noise you don't hear it. Alot of really big builds you would hear the car flexing louder than the port noise.

And like you said we don't all roll around with our systems maxed out

 

[Bobbytwonames 5,000+ posts]

You might, and you might hear it or you might not. 12in² per cube in a slot port is on the small side and is best kept for low xmax subs. The higher the xmax the more port area you need. It varies subs to sub and by different power levels.

all of this can me calculated. Generally 40m/s is what you want to stay under. My last 3.31 at 36hz with 2 4inch aeros was at like 45m/s and I didn't hear the ports.

In a trunk port noise might not be heard. Behind the seat of your truck it might be muffled enough that you don't care. Or you vehicle might just me loud enough with road noise you don't hear it. Alot of really big builds you would hear the car flexing louder than the port noise.

And like you said we don't all roll around with our systems maxed out

The only thing I hear is one sub bottoming out during demo's sometimes. Usually on stuff under 30hz.

 

[winkychevelle 10+ year member]

The only thing I hear is one sub bottoming out during demo's sometimes. Usually on stuff under 30hz.

That is probably a port loading issue if it's just 1 sub. Probably isn't severe though

 

[Bobbytwonames 5,000+ posts]

That is probably a port loading issue if it's just 1 sub. Probably isn't severe though

4 - 8's. It sounds like only one bottoms out. The port loads against the passenger side wall. I've been told it's because I'm playing too low or overpowering them.

 

[winkychevelle 10+ year member]

4 - 8's. It sounds like only one bottoms out. The port loads against the passenger side wall. I've been told it's because I'm playing too low or overpowering them.

If it's only one of them it's likely to one closest to the port opening inside the box. Since it has the shortest path it unloads first. Ideally you want the subs to be equal distance from the internal port opening but that can't happen in every case for obvious reasons.

On moderate power systems you can get away with alotmof things but once you start throwing a lot of power these small issues start to show up. In your case you are probably already close to the others bottoming out at the same time. That one is just an early warning lol