Recommended sealed box size for RSS390HF-4 15"

S

Sylar

Full Audioholic
I have obtained the Dayton RSS390HF-4 15", and require advice on the design.

After reading Ray Alden's speaker building book and having browsed through 100's of threads. The recommended ported box size is around 9 cu ft, which is not reasonable by any means. Going ported is completely ruled out. Same with other designs like isobaric. Which leaves me with a sealed design. For this driver with sealed, I understand I might have to compromise on the low end or something else to a certain degree. After much contemplation, the only design that I can do, is sealed. Hence this thread.

So, I have made three decisions to begin with.
  1. Driver is RSS390HF 15" (I already have it).
  2. Design is Sealed box.
  3. Amp is external - XLS 1500 or XLS 2002 (I have both). I also have a MiniDSP.
Next up is box size. Which is where I require advice.
Reading through numerous threads across different forums, I find the sealed box size for this driver vary widely from 2.5 to 6 cu ft.

So what is the best sealed box size for this driver and why?
 
Last edited:
TLS Guy

TLS Guy

Audioholic Slumlord
I have obtained the Dayton RSS390HF-4 15", and require advice on the design.

After reading Ray Alden's speaker building book and having browsed through 100's of threads. The recommended ported box size is around 9 cu ft, which is not reasonable by any means. Going ported is completely ruled out. Same with other designs like isobaric. Which leaves me with a sealed design. For this driver with sealed, I understand I might have to compromise on the low end or something else to a certain degree. After much contemplation, the only design that I can do, is sealed. Hence this thread.

So, I have made three decisions to begin with.
  1. Driver is RSS390HF 15" (I already have it).
  2. Design is Sealed box.
  3. Amp is external - XLS 1500 or XLS 2002 (I have both). I also have a MiniDSP.
Next up is box size. Which is where I require advice.
Reading through numerous threads across different forums, I find the sealed box size for this driver vary widely from 2.5 to 6 cu ft.

So what is the best sealed box size for this driver and why?
The optimal box size is 2.5Cu.ft. However you have to add driver displacement and bracing to that. So you final box volume will be something like 2.75 cu ft, when you add back the air volume displaced by those items. This box size will give you are very satisfactory Qts of 0.7, so the bass will be tight.

As will all sealed designs, you will have to add a boost of 12 db per octave starting at 40 Hz. The driver starts to get significantly power limited below 25Hz, so a 12 db per octave high pass filter should be placed at 25 Hz. All this is normal practice when designing a sealed sub. Sealed have simpler carpentry, but more complex electronics. However Mini DSP should get this job done for you.

This will be a good sounding sub, but output limited compared to a ported design. However, I think unless you space is huge you will be happy with it.
 
S

Sylar

Full Audioholic
The optimal box size is 2.5Cu.ft. However you have to add driver displacement and bracing to that. So you final box volume will be something like 2.75 cu ft, when you add back the air volume displaced by those items. This box size will give you are very satisfactory Qts of 0.7, so the bass will be tight.
Was stuck with work. Just got some time to get back to this.
Curious to know what happens when I increase box size (for example 2.5 to 3 Cu ft)? What do I gain and what do I lose?

Got 2 weeks off from work. Will try and build it during this period.
 
TLS Guy

TLS Guy

Audioholic Slumlord
Was stuck with work. Just got some time to get back to this.
Curious to know what happens when I increase box size (for example 2.5 to 3 Cu ft)? What do I gain and what do I lose?

Got 2 weeks off from work. Will try and build it during this period.
The program I used calculates the optimal box. That means what it says. So what it does, is find the optimal balance between bass extension, Q and power handling.

So you only have downsides from making variations away from the optimal box. So if you increase box size, then you will move away from optimal Q, and above all loose power handling, as the restoring force on the driver cone will be reduced. So that will limit your ability to apply the required Eq.

I have to say that you are calling to mind a well documented incident that involved Peter Walker founder of Quad Electroacoustics at an Audio Fair at the Russel Hotel.
A visitor kept asking him the same question repeatedly. Finally he got hold of the guy by his lapels, and said: "If you are not going to believe the bloody answer, then don't ask the bloody question!"
 
S

Sylar

Full Audioholic
The program I used calculates the optimal box. That means what it says. So what it does, is find the optimal balance between bass extension, Q and power handling.

So you only have downsides from making variations away from the optimal box. So if you increase box size, then you will move away from optimal Q, and above all loose power handling, as the restoring force on the driver cone will be reduced. So that will limit your ability to apply the required Eq.

I have to say that you are calling to mind a well documented incident that involved Peter Walker founder of Quad Electroacoustics at an Audio Fair at the Russel Hotel.
A visitor kept asking him the same question repeatedly. Finally he got hold of the guy by his lapels, and said: "If you are not going to believe the bloody answer, then don't ask the bloody question!"
Sorry, My bad.I was reading stuff and trying to understand effects of different box sizes. Attempting to use a subwoofer design tool with not much success.

I am currently drawing the box plans for this.
Dimensions look like this with target internal volume of 2.5cu ft. Following are the dimensions that I came up with for this.

Internal: 16.5 x 16.5 x 17 inch
External: 18 x 18 x 18.5 inch
Woofer and Bracing volume: 0.173 cu ft
Final box volume: 2.505 cu ft

A few quick questions:
  1. Should I double up the driver side panel? I do not intend to flush mount. Will be using 18/19mm wooden panels.
  2. How much should I fill up the sub with fiberglass?
  3. Which nuts do i use to mount the driver. While building my previous sub i had some trouble with the nuts.
  4. Should MDF be good enough? Or should I use Birch Plywood?
 
ryanosaur

ryanosaur

Audioholic Spartan
Sorry, My bad.I was reading stuff and trying to understand effects of different box sizes. Attempting to use a subwoofer design tool with not much success.

I am currently drawing the box plans for this.
Dimensions look like this with target internal volume of 2.5cu ft. Following are the dimensions that I came up with for this.

Internal: 16.5 x 16.5 x 17 inch
External: 18 x 18 x 18.5 inch
Woofer and Bracing volume: 0.173 cu ft
Final box volume: 2.505 cu ft

A few quick questions:
  1. Should I double up the driver side panel? I do not intend to flush mount. Will be using 18/19mm wooden panels.
  2. How much should I fill up the sub with fiberglass?
  3. Which nuts do i use to mount the driver. While building my previous sub i had some trouble with the nuts.
  4. Should MDF be good enough? Or should I use Birch Plywood?
Baltic Birch will be lighter and work great for Subs. I would recommend seeking that out as your option.

Doubling up the Front Baffle is is common, and for a 15" driver, not a bad plan.

Which nuts?
Deez Nuts GIF by imoji for iOS & Android | GIPHY
Sorry, couldn't help myself.
...
Low hanging fruit! :D

But seriously... are you thinking of installing T-Nuts or threaded inserts? Bolting through the layers or just some heavy wood screws?
 
S

Sylar

Full Audioholic
Baltic Birch will be lighter and work great for Subs. I would recommend seeking that out as your option.

Doubling up the Front Baffle is is common, and for a 15" driver, not a bad plan.

Which nuts?
Deez Nuts GIF by imoji for iOS & Android | GIPHY
Sorry, couldn't help myself.
...
Low hanging fruit! :D

But seriously... are you thinking of installing T-Nuts or threaded inserts? Bolting through the layers or just some heavy wood screws?
Was thinking of using T-Nuts. Do I have a better option?
 
TLS Guy

TLS Guy

Audioholic Slumlord
Sorry, My bad.I was reading stuff and trying to understand effects of different box sizes. Attempting to use a subwoofer design tool with not much success.

I am currently drawing the box plans for this.
Dimensions look like this with target internal volume of 2.5cu ft. Following are the dimensions that I came up with for this.

Internal: 16.5 x 16.5 x 17 inch
External: 18 x 18 x 18.5 inch
Woofer and Bracing volume: 0.173 cu ft
Final box volume: 2.505 cu ft

A few quick questions:
  1. Should I double up the driver side panel? I do not intend to flush mount. Will be using 18/19mm wooden panels.
  2. How much should I fill up the sub with fiberglass?
  3. Which nuts do i use to mount the driver. While building my previous sub i had some trouble with the nuts.
  4. Should MDF be good enough? Or should I use Birch Plywood?
For a driver that large I always double the front panel.

The box needs to be filled. Fiber glass is not optimal. The best and cheapest option is Polyfill used in cushions. Fill the box but do not compress it.

T-nuts are fine and a good option for a heavy driver.

MDF or Baltic Birch are good options for a sub.
 
S

Sylar

Full Audioholic
I'm not getting any decent rubber feet other than for spikes. (I'm in India) Any suggestions for subwoofer feet?

My PSB towers came with these rubber feet, 20mm in length. The ply board is 18mm. Would this work?
 

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TLS Guy

TLS Guy

Audioholic Slumlord
I'm not getting any decent rubber feet other than for spikes. (I'm in India) Any suggestions for subwoofer feet?

My PSB towers came with these rubber feet, 20mm in length. The ply board is 18mm. Would this work?
You can use any furniture feet from a hardware store. I'm sure any hardware store will give you lots of options. They do not have to be for speaker use specifically.
 

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