First Sub design. Sanity check please?

[gbissend]

Hi All:

I hope some more experienced Sub-Builders will take a look at my design and give me feedback before I get too deep in sawdust.

I an using a Dayton Audio RSS265HF-4 10" driver and have run the numbers through WinISD and UniBox they both come up with a port length of about 120 cm for my box - Link to design PDF below:

https://www.mediafire.com/?144wc3ht8rosbut

Here's a link to my WinISD file:

https://www.mediafire.com/?144wc3ht8rosbut

Or if you prefer UniBox: (For those with MS Excel.)

https://www.mediafire.com/?144wc3ht8rosbut

I have designed in a sliding exit port to allow me to adjust the length of the port, just in case...

Anyhow, what I need is to have someone take a look at this and tell me if my port length calculation is correct. I could shorten it up by moving the u-turn up a little if need be.

The port length I get is:

((2.1 + 2.945) * 2) + This is the inlet and outlet transitions.
6.953 + The straight below the outlet port.
15.503 + The U-turn at the bottom of the box.
15.080 The straight up to the inlet.

47.606" Total port length to middle of adjustment range

120/2.54 = 47.25 Design software port length for 14 cm round port equivalent (3.75" x 6.375")

I am going to be using a 3/4 inch round over router bit to make the inlet and outlet flanges.


Any takers???

Thanks

George

 

[fuzz092888]

Is it the Dayton 265 HO or HF?

 

[gbissend]

Thanks for the quick reply!

Oops - RSS265HF-4 is the right one.

 

[fuzz092888]

I can't guarantee the turn will work, but I'm getting a box size of 49.25 liters, with a port diameter of 4" and a length of 34.6". It will be tuned to ~22.5hz and have an F3 of 25hz. The only problem is that it won't handle a lot of power and it has to have a HPF on it or the sub will bottom out during any sort of HT content with stuff below 20hz. It should do ~110db from 30-100hz.

 

[gbissend]

The inner dimensions of the speaker chamber are 10 X 16.25 X 26.25 which gives 70 (69.9) liters less the bracing and speaker volume. All the port plumbing is in the next room.

The equivalent round port diameter is 14 cm (5.5 inches => 23.9 sq in vs 3.75 X 6.375 => 23.91 sq in) the port length I got from the programs was about 47 inches. I made the area large to keep the port air velocity down.

I spec'd it out at 100-125 watts. I saw that the excursion was getting big at around 20 Hz. I have a MiniDSP and was going to be careful about the power below about 22 Hz.

What is an HPF? I haven't run into that TLA before.

Thanks for your work. Hope the above gives you more useful info.

George

 

[fuzz092888]

HPF= high pass filter. A high pass filter will roll off the signal at whatever point you select and at the slope you select. It's basically what you're describing. If you didn't have a MiniDSP, I would go along with helping you port it, but since you have one already my advice would be to put it in a sealed cab and use the miniDSP to boost the low frequencies flat to 20hz, put a HPF on at about 15-20hz and you'll have a great sub. Since you already have the MiniDSP I would highly recommend this approach, as its more suited to the driver and will make the build pretty simple.

 

[TLS Guy]

In my view you have made a poor driver selection for home audio. That looks like a driver for a small half cu.ft sealed box for automobile use.

The driver is not suitable for ported loading. The Qts is too high, and suspension too loose. Your first clue is your long port length, which is so long you will have a nasty honky port resonance. So this driver can only be placed in a sealed enclosure. In an optimal sealed enclosure F3 is 65 Hz, and the xmax of that driver is only 12.3 mm. So you really have no room for Eq to 30 Hz or so at good spl.. The Fs of the driver is 26 Hz and that sets the practical limit of the low end response.

Now even before Eq the cone displacement at 30 Hz is 10 mm, so you have two mm to play with. Your HPF needs to be set around 26 HZ. Before roll off max db is 110. Now to flatten the frequency response requires Eq of 12 d per octave starting at 60 to 65 Hz, so you will have 12 db of boost by 30 Hz. This will give you a practical output of 98 db at 30 Hz. If this is in a small room, like a small office it will be fine. For a normal living room I think you will be disappointed.

The other issue is the Q of the whole system, which can never be lower than driver Qts, Sealed if just gets in below a total system Q of 0.7. For really tight bass I like a Q of 0.5. In a ported enclosure, in addition to the port resonance the bass will be highly resonant and boomy. You can not contemplate a ported design with this driver. If you want a ported sub, then the sweet spot for driver Qtc is in the 0.3 to 0.35 range.

 

[gbissend]

Hi again:

Thanks for the feedback!

Ok, I got sidetracked into ported because at the time I was not yet aware of the wonderfulness of the MiniDSP.

See below for an earlier sealed design.

Normal%20subwoofer%20measurements%2045L

Ignore the 45 liter indication in the file name. It is actually about 38 liters less the bracing and the driver. It comes down to about 1 cu ft all in.
This is an earlier sealed design that we came up with, prior to getting friendly with WinISD and UniBox. After trying to get it to work, un-boosted, it seemed like the low base was missing too much.

The shape comes from a liberal application of Phi.

Is this more along the lines of what you guys think would work with my driver? Or do I need to get even smaller?

Thanks again

George

 

[gbissend]

TLS - Upon closer reading of your post, re Qts better in the range of 0.30 to 0.35.

I checked the Qts of the 265 HF it is 0.441 /0.453. I also have on hand a 265HO driver, which has a considerably lower Qts of 0.367/0.377, not quite in the "sweet spot" but closer.

Looking back at the original ported design, would that driver work better? Or are there other factors that make it unacceptable?

Thanks

 

[TLS Guy]

TLS - Upon closer reading of your post, re Qts better in the range of 0.30 to 0.35.

I checked the Qts of the 265 HF it is 0.441 /0.453. I also have on hand a 265HO driver, which has a considerably lower Qts of 0.367/0.377, not quite in the "sweet spot" but closer.

Looking back at the original ported design, would that driver work better? Or are there other factors that make it unacceptable?

Thanks

That driver has a high Fs and will only perform down to around 40 Hz.

I don't know what your application is, but if you are trying to pressurize a large space, then neither driver fits the bill and you need to look at something else. Those will not be worth the blood sweat and tears.

 

[gbissend]

I found a possible replacement at the same outlet where I bought The Daytons. I might be able to return the Daytons and get a pair of these.

Please let me know what you think. BTW, what drivers do you use for sealed and ported boxes? I should have asked this earlier.

The resonant frequency is 22 Hz but the Qts might be too low: 0.23. How does the Qts value affect the system tuning?

It is a "Peerless 830452 10" XLS Subwoofer"

Specs:

Resonant Frequency (Fs)22 Hz
DC Resistance (Re)3.6 ohms
Voice Coil Inductance (Le)0.99 mH
Mechanical Q (Qms)3.86
Electromagnetic Q (Qes)0.24
Total Q (Qts)0.23
Compliance Equivalent Volume (Vas)2.36 ft.³
Mechanical Compliance of Suspension (Cms)0.39 mm/N
BL Product (BL)16.75 Tm
Diaphragm Mass Inc. Airload (Mms)136.6g
Maximum Linear Excursion (Xmax)12.5 mm
Surface Area of Cone (Sd)349.7 cm²


Thanks

 

[fuzz092888]

What is the size of your room (LXWXH). Is this sub going to be used for music only, or music and movies? If it's going to be used for movies all or part of the time and if the room is medium sized, one or even a pair of 10" drivers probably isn't going to cut it for low bass.

Out of curiosity, and you can PM me, what price did you find for the XLS woofers?

 

[gbissend]

Hi Again:

What do I use it for? Everything. Radio most days all day; Home theatre, yes: Music, Yes.

My room is large. 15' wide x 17' long x 8-9' H (vaulted) open concept with kitchen 9' opening and hallway out back.

A couple of months ago, my old PSB SubSeries 5i broke, again. I was simply looking to replace it with a more robust bass extender.

I have a tenant, living downstairs, so house shaking bass would be nice but probably overkill.

My mains, PSB VisionSound VS400, are a little anemic at low frequency nothing much below about 60-70 Hz.

I was originally going to simply replace the amp in the PSB box, but it turned out that the driver was open circuit. This led me to buy a RSS265HO, my first mistake.

Looking at all of the subwoofer design stuff on the internet, I thought, "This looks easy". My second mistake.

After that came WinISD, UniBox, Vectorworks, MiniDSP, etc... You know the drill.

I thought that I had a pretty good design, I had missed the "Include effect of port resonance" check box. my third mistake!

With that enabled, things got ugly real quick.

And here I am.

George

 

[gbissend]

OK - I'm thinking that I made the wrong choice for the driver, given my requirements.

I've got a 250 watt amp right now, and preferrably I'd like to keep that so I'm not adding more and more to the budget.

I can return the 2 drivers that I have for a full refund, so that would put me around $250.00 for a budget for getting a new driver.

As I have already cut the panels for it, I would like to stay with my original enclosure size (or smaller) of about 65 liters/2.25 cu/ft

The driver selection and ported vs sealed design decisions are now open.

The case seems to be capable of handling a 15" driver with some modifications.

What would fit in that (or something close to it) and would fit the needs for what I'm trying to do?

Thanks

 

[fuzz092888]

It's too bad you already cut the panels. For that budget and cabinet volume you could've gotten an 18" driver. In any case, an SI 15" should do the job, but I'll have to run it through BB pro to double check on the cabinet volume.

 

[gbissend]

Hi:

Yes, it is too bad, an 18" would have been stunning!

The specs on these speakers show that they are at a level well above the Daytons. Xmech is not even mentioned in the Dayton specs...

The manufacturer says that the 15" works with a 3 cu ft sealed box. I can get that volume by moving the inner back panel out from 10" to 12.125" plus the offset to make up for the speaker and bracing volume. Another thing I like is that they tell you what the driver volume is!

Do you still favor a sealed box? Or could I get this one to work ported? My copy of WinISD is choking on "floating point numbers" going to need a restart...

Computers - cant live with them....

I will need to re-do the bracing, but, I made a few errors on the last one will do them right this time.

Thanks again!

 

[fuzz092888]

Definitely not ported with the SI subs.

 

[gbissend]

Great! That simplifies the build enormously.

Resizing will be easy. I will be starting on the new bracing tomorrow.

Thanks for the course correction!!!
George

 

[TLS Guy]

I found a possible replacement at the same outlet where I bought The Daytons. I might be able to return the Daytons and get a pair of these.

Please let me know what you think. BTW, what drivers do you use for sealed and ported boxes? I should have asked this earlier.

The resonant frequency is 22 Hz but the Qts might be too low: 0.23. How does the Qts value affect the system tuning?

It is a "Peerless 830452 10" XLS Subwoofer"

Specs:

Resonant Frequency (Fs)22 Hz
DC Resistance (Re)3.6 ohms
Voice Coil Inductance (Le)0.99 mH
Mechanical Q (Qms)3.86
Electromagnetic Q (Qes)0.24
Total Q (Qts)0.23
Compliance Equivalent Volume (Vas)2.36 ft.³
Mechanical Compliance of Suspension (Cms)0.39 mm/N
BL Product (BL)16.75 Tm
Diaphragm Mass Inc. Airload (Mms)136.6g
Maximum Linear Excursion (Xmax)12.5 mm
Surface Area of Cone (Sd)349.7 cm²


Thanks

That driver is designed for a fairly small box and passive radiator. The driver can not be used sealed, and port dimensions are not practical. F3 is just above 30 Hz, so no deep bass. Sensitivity is low and power 150 watts. It will not drive your space.