4th Order Bandpass. 8" woofer

Jake321

CarAudio.com Recruit
Sep 27, 2022
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4th Order Bandpass.


8" Subwoofer.

Tunning (FS).

Port: 4" Port.

Chambers: (3:1)
.50 Cubic Feet (Sealed).
1.5 Cubic Feet ( Ported).

Internal Specs:
36" X 10" X 10"
Total Cubes: 2.0

(not including mdf chamber ¾" separation).


Would this design work?
 

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SlugButter

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Nov 5, 2019
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4th Order Bandpass.


8" Subwoofer.

Tunning (FS).

Port: 4" Port.

Chambers: (3:1)
.50 Cubic Feet (Sealed).
1.5 Cubic Feet ( Ported).

Internal Specs:
36" X 10" X 10"
Total Cubes: 2.0

(not including mdf chamber ¾" separation).


Would this design work?
It probably would work. I’m not sure about tuning right at the woofer FS though. What sub are you using?
 
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Jake321

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Sep 27, 2022
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It probably would work. I’m not sure about tuning right at the woofer FS though. What sub are you using?
A single: DD608. Or 508.

Amp Tuning to FS according to sealed chamber?

Port chamber lower or higher than FS?
 
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Jake321

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Sep 27, 2022
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Great 👍 I'm Using WinlSD Pro.

Now I know the Tuning for the "Front Chamber".

Hahaha volume is 🤣. But still trying to add a new driver (not going so easy).
 

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winkychevelle

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Jun 21, 2009
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Last one I had designed for a 506 ended up at a 1:1 ratio tuned at 47hz.

We were shooting for a flat response from 30hz to 60hz. Never built it though
 

winkychevelle

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Is this photo considered flat?
No not really that one has a big bump at the low end. That's not really an issue but with cabin gain the bump can turn into a hell of a spike. Again depending on use it's not a bad thing.

The problem is that 4th orders hide distortion pretty good so by the time you notice it it's usually too late and damage is done.

A more flat response means you aren't trying to boost the other frequencies that you really can't to match that huge bump in frequency response.

I typically tune to 36hz for my truck because I know the cabin gain allows me to play down into the mid 20s fairly well. Not that I play that low as I usually put my sub sonic filter at 28hz anyway. But this allows me to tun slightly higher to allow for a flatter response curve for a wide frequency range.

In my opinion without knowing you cabin gain which requires several measurements with calibrated mics you are best served tuning around 34-38hz for most ported boxes and bandpass I would want my bump to peak in the same range.

Lower if you listen to more decaf, and rebassed music, and higher for more rock. Country topically requires the sub stage to be turned down in my opinion less the bass guitar takes over everything.

If you want a wind monster tune low, most demo builds are tuned from 36-28hz in my experience because they move a crap load of air
 

SlugButter

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Nov 5, 2019
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Is this photo considered flat?
it isn’t the worst I’ve ever seen. peaky on the low end some. That will get even more peaky when you put it in your car. You have it set to meters also, and the box looks way too big. Click on that and change it to feet. Start with the recommended sealed box air space on the rear chamber and try doubling the front and see what it looks like. Maybe .5-.75 sealed and 1.5 tuned to 45 HZ and see how it looks. Subs that prefer a sealed box do better in a 4th, and ported box subs do better in a 6th order. The DD subs might be a little more geared towards a ported/6th order.
 

winkychevelle

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Jun 21, 2009
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it isn’t the worst I’ve ever seen. peaky on the low end some. That will get even more peaky when you put it in your car. You have it set to meters also, and the box looks way too big. Click on that and change it to feet. Start with the recommended sealed box air space on the rear chamber and try doubling the front and see what it looks like. Maybe .5-.75 sealed and 1.5 tuned to 45 HZ and see how it looks. Subs that prefer a sealed box do better in a 4th, and ported box subs do better in a 6th order. The DD subs might be a little more geared towards a ported/6th order.
Buck wanted to design me a 6th for my 506s but I didn't have the room under the back seats. He definitely didn't care for the 4th order arrangement as a designer. The response curves were similar to my straight up ported box with little variance but that didn't matter it was mainly just to protect the subs from feet since grills for high excursion subs are hard to come by. I don't really think most DD subs will work great in a 4th order and agree that a 6th or ported arrangement would be better.

This next box with 4 6.5s I'm just gonna countersink the subs like 2 inches and use stainless mesh to build my own grill. I'll lose available airspace thus the reason for 6.5s over 8s. No fancy boxes just pure ported bliss. I'm pretty good at building/designing those.
 

SlugButter

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Nov 5, 2019
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Buck wanted to design me a 6th for my 506s but I didn't have the room under the back seats. He definitely didn't care for the 4th order arrangement as a designer. The response curves were similar to my straight up ported box with little variance but that didn't matter it was mainly just to protect the subs from feet since grills for high excursion subs are hard to come by. I don't really think most DD subs will work great in a 4th order and agree that a 6th or ported arrangement would be better.

This next box with 4 6.5s I'm just gonna countersink the subs like 2 inches and use stainless mesh to build my own grill. I'll lose available airspace thus the reason for 6.5s over 8s. No fancy boxes just pure ported bliss. I'm pretty good at building/designing those.
I just made this box for a couple of 6,5s from the little strips of wood in my scrap pile. Those skinny little strips that are left over from big builds need to be used for something. I had an RDS 6.5 inch in a 6th order bandpass for awhile and it played really nice. I like 6.5 inch subs. If I had a truck that’s what I’d use.
27F7FA22-2FCA-4D6D-ABB0-3F9DD539827C.jpeg
1B07DA53-1B78-4CAE-B5DF-94C965E22928.jpeg
 

winkychevelle

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Jun 21, 2009
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I likedy 506 well enough I just got the bug to do a rebuild and went bigger since they were the wrong ohm load to ad 2 more. I really want to try the sundown u6.5 but who knows when they will release. The x6.5 doesn't interest me at all and the sa6.5 just seems anemic.

If not for rediculous cost I'd do 4 dd1506sc under the back seats. Might still do that but that's 1600 on 4 6.5s not exactly bang for your buck
 
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Jake321

CarAudio.com Recruit
Sep 27, 2022
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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??


43074
 

winkychevelle

CarAudio.com Veteran
10+ year member
Jun 21, 2009
4,439
387
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
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
 

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