Twin Sundown SA6.5 SW D2 32Hz Ported 0.6ft3 in Ford Escape Box Build

[THATpurpleKUSH 5,000+ posts]

According to bass box pro a pair of those 6.5s only need about .38-.4cf tuned around 40hz to model pretty flat. You'll have decent extension into the mid 30s, don't expect anything below about 35hz. The higher you go above .4cf the more under damped the design will be and the more peaky the response will be. So smaller is better in this instance which is good because of the limited space. The hard part will be adapting a port. I still think a passive radiator would work best.

 

[imsickofweed]

Got most of the cabinet built, need to cut the slot port and install the port board and baffle, but its coming together pretty good.

 

[imsickofweed]

According to bass box pro a pair of those 6.5s only need about .38-.4cf tuned around 40hz to model pretty flat. You'll have decent extension into the mid 30s, don't expect anything below about 35hz. The higher you go above .4cf the more under damped the design will be and the more peaky the response will be. So smaller is better in this instance which is good because of the limited space. The hard part will be adapting a port. I still think a passive radiator would work best.

Ive never had a box with a passive radiator, Im really unfamiliar with it. As far as box volume goes, my first try will be around 0.6cuft net and I can move the baffle in and see where that gets me. 0.4cuft is really small for anything including 6.5s, Id love to see a graph of that modeled output vs a 0.6 or 0.7cuft box.

 

[THATpurpleKUSH 5,000+ posts]

Ive never had a box with a passive radiator, Im really unfamiliar with it. As far as box volume goes, my first try will be around 0.6cuft net and I can move the baffle in and see where that gets me. 0.4cuft is really small for anything including 6.5s, Id love to see a graph of that modeled output vs a 0.6 or 0.7cuft box.

Passive radiators are very easy to work with. Its basically the top half of a subwoofer with no magnet. All you do is add weight to tune them. You get the benefits of a ported box and the space saving of a sealed box. A 10inch pr would be perfect for your build. I can post graphs of the .4 ported when I get home from work this evening.

 

[imsickofweed]

Passive radiators are very easy to work with. Its basically the top half of a subwoofer with no magnet. All you do is add weight to tune them. You get the benefits of a ported box and the space saving of a sealed box. A 10inch pr would be perfect for your build. I can post graphs of the .4 ported when I get home from work this evening.

Ive seen a kicker setup with a prebuilt box like this and actually considered it because it fit in my space. I decided to go this route because I could fit 2 drivers instead of one. If that graph of the 0.4cuft box looks good, maybe Ill save space in the baffle to add a 3rd 6.5 in the line up. Itll be easy to add physically, but Im not 100% sure how Id wire them to get between a 2-4ohm load at the amp.

 

[k5james 10+ year member]

I went with a Tline for a pair of these. I haven't installed yet so I can't give you impression at the moment.

 

[imsickofweed]

Just got the shipping notification from sundown, subs should be here 5/29. I can almost hear them now...

 

[THATpurpleKUSH 5,000+ posts]

Ive never had a box with a passive radiator, Im really unfamiliar with it. As far as box volume goes, my first try will be around 0.6cuft net and I can move the baffle in and see where that gets me. 0.4cuft is really small for anything including 6.5s, Id love to see a graph of that modeled output vs a 0.6 or 0.7cuft box.

Blue Line is .6cf @ 32hz - Sundown Recommended

Red Line is .4cf @ 40hz

Yellow Line is .3cf @ 38hz

450w of power

A 2 inch round port was used and when you see the vent velocity you will see that it's not enough, ideal vent velocity should be below 35 m/s. You'll notice the lines darken when they go beyond this point. Going up to a larger port size will need a crazy long length like at least 2 feet most likely. This is why I was suggesting a passive radiator.

Group delay on the blue line peaks at 28ms at ~28hz. Higher group delay = more sloppy and boomy sounding

Yellow line is the most SQ friendly imo

Red is a compromise of sacrificing what little low end there is to gain more SPL in the 40-60hz area and would sound the loudest in car.

https://imgur.com/uEWmP9A

 

[Buck 5,000+ posts]

Passive radiators are fairly easy and cab be tuned if they offer that. It's still largely the same as ported, it's a delay radiating surface that's shifts the phase of the rear wave of the woofer like a regular port does. I know in high power applications, PR's fade out because of mechanical limits. Just check the linearity of the cone movement when it moves and look at the Sd and xmax for total air moved in a stroke.

I've had situations where guys just keep adding PR's and keep gaining because their woofers are so powerful. 6.5's should be fine, though. You could probably make it sound pretty good.

I think you should consider a series 6th order bandpass.

 

[imsickofweed]

Blue Line is .6cf @ 32hz - Sundown RecommendedRed Line is .4cf @ 40hz

Yellow Line is .3cf @ 38hz

450w of power

A 2 inch round port was used and when you see the vent velocity you will see that it's not enough, ideal vent velocity should be below 35 m/s. You'll notice the lines darken when they go beyond this point. Going up to a larger port size will need a crazy long length like at least 2 feet most likely. This is why I was suggesting a passive radiator.

Group delay on the blue line peaks at 28ms at ~28hz. Higher group delay = more sloppy and boomy sounding

Yellow line is the most SQ friendly imo

Red is a compromise of sacrificing what little low end there is to gain more SPL in the 40-60hz area and would sound the loudest in car.

https://imgur.com/uEWmP9A

Thank you for doing those graphs. Is it possible to see 0.6 and 0.7cuft at 40Hz?

I already finished most of the cabinet and I dont think I could move the baffle up high enough to make it 0.3 or 0.4cuft. It narrows towards the top so I run out of room for the driver before I get down to 0.3 or 0.4cuft. Also I was planning on my slot vent being 1”x8” which is 4cuin per driver. I think the 2” round port is too small so thats probably why the velocity is super high.

 

[THATpurpleKUSH 5,000+ posts]

Thank you for doing those graphs. Is it possible to see 0.6 and 0.7cuft at 40Hz?
I already finished most of the cabinet and I dont think I could move the baffle up high enough to make it 0.3 or 0.4cuft. It narrows towards the top so I run out of room for the driver before I get down to 0.3 or 0.4cuft.

Red line is .6 with 2 1.5 inch ports, slightly more port area than a single 2 inch, but still not enough

Green line is .7 with a 3 inch port- note the much lower port velocity. This is the size I would recommend using, the length should be doable with the .7 box.

https://imgur.com/EyIX3vI

 

[imsickofweed]

Passive radiators are fairly easy and cab be tuned if they offer that. It's still largely the same as ported, it's a delay radiating surface that's shifts the phase of the rear wave of the woofer like a regular port does. I know in high power applications, PR's fade out because of mechanical limits. Just check the linearity of the cone movement when it moves and look at the Sd and xmax for total air moved in a stroke.
I've had situations where guys just keep adding PR's and keep gaining because their woofers are so powerful. 6.5's should be fine, though. You could probably make it sound pretty good.

I think you should consider a series 6th order bandpass.

I did a little research on the passive radiators, seems like I need a 10” to match the twin 6.5s. Theres 2 places to put it, one is in the way of the larger seat folding down and the other end of the box is close to the door. I might have enough room on that side if I mount it on the inside of the cabinet facing out, not sure how much excursion they will have, but I have an inch or two before it hits the door.

 

[THATpurpleKUSH 5,000+ posts]

The 10s are out of stock until July

https://www.parts-express.com/dayton-audio-sd270-pr-10-designer-series-passive-radiator--295-494

8s are due in stock by the end of this month, you could do 2 8s

https://www.parts-express.com/dayton-audio-sd215-pr-8-designer-series-passive-radiator--295-492

 

[imsickofweed]

Thanks so much for those, I really appreciate it.

 

[imsickofweed]

New video part 3



I sanded the box and got rid of a lot of rough edges, screwed it pretty good, but I think its still going to need some internal support on th long pieces with angled edges.

I was reading about passive radiators and I saw that PRs are recommended for drivers with a Qts below 4, this one is slightly above 4. Is there any danger of using the PR with these?