How to determine port diameter and length?

[Cpt.America]

Hey all. I plan on building a small and simple 8" powered sub for my computer setup, and as was hoping to build a basic square/rectangle ported enclosure for it. My question is, how the heck do I determine the tube size?

Just as an exmple, I was looking at this $80 woofer from PE

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=264-854

I was thining of building soemthing around 12x12x11 which would give me about .9 cubic feet.... but how do I determine the tube size for the port? I was planning on buying a simple press-in port tube from PE.

Thanks for any tips you can provide.

 

[Swerd]

Hey all. I plan on building a small and simple 8" powered sub for my computer setup, and as was hoping to build a basic square/rectangle ported enclosure for it. My question is, how the heck do I determine the tube size?

Just as an exmple, I was looking at this $80 woofer from PE

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=264-854

I was thining of building soemthing around 12x12x11 which would give me about .9 cubic feet.... but how do I determine the tube size for the port? I was planning on buying a simple press-in port tube from PE.

Thanks for any tips you can provide.

You must know three parameters of the woofer, the Fs, Qts, and Vas. Parts Express will have that info for each woofer.

With that info you can calculate the volume of the box and diameter and length of a port at this site.

 

[Cpt.America]

Thanks.. I do see a bunch of speaker specs listed on PE. Your link however, is no worko....

(edit: worko now.. thanks)

Another thing I don't get, is these calculators all ask for the tuning frequency. But this isn't a speaker spec, so how would you know what freq you are looking for?

 

[Cpt.America]

Not only do i not know what freq to tune it to, I also dont have other things the calculator wants either, like Driver Cone Area, Minimum Diameter, and Minimum Area?..... im lost

 

[Swerd]

Not only do i not know what freq to tune it to, I also dont have other things the calculator wants either, like Driver Cone Area, Minimum Diameter, and Minimum Area?..... im lost

You could call Parts Express Technical Advice 1-800-338-0531. They will have a suggestion.

When I searched The Parts Express Tech Talk forum, I found this thread:

http://techtalk.parts-express.com/showthread.php?t=202615&highlight=Tang+Band+inch+subwoofer

The OP had the same question as you. I haven't read the whole thread in detail, but there are some answers to your question in it.

 

[highfigh]

Not only do i not know what freq to tune it to, I also dont have other things the calculator wants either, like Driver Cone Area, Minimum Diameter, and Minimum Area?..... im lost

There are other programs that will do modeling for the results of the calculations and based on these, you can add a port. A speaker in a sealed box will have limited low frequency response and the port works like blowing across the mouth of a Coke bottle. It's one note with some energy above and below that note's frequency and it's tuning will extend the lowest usable frequencies from that speaker/box combination. The tuning of the port will also affect the speaker's power handling ability, so while one tuning may look great on a graph, the speaker may puke with 15W going into it, as if it was sitting on a shelf, connected to an amp that was cranked.

Most speaker data sheets will show piston area and you can use this to derive the average Max/Min diameters. It's part of the math most people assumed they would never need after high school.

 

[TLS Guy]

Hey all. I plan on building a small and simple 8" powered sub for my computer setup, and as was hoping to build a basic square/rectangle ported enclosure for it. My question is, how the heck do I determine the tube size?

Just as an exmple, I was looking at this $80 woofer from PE

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=264-854

I was thining of building soemthing around 12x12x11 which would give me about .9 cubic feet.... but how do I determine the tube size for the port? I was planning on buying a simple press-in port tube from PE.

Thanks for any tips you can provide.

Just hang on until after the holiday. I'm at our Eagan town home, not Benedict for the holiday. I have to do data recovery Friday on my laptop. If I get the hard drive changed and loaded, I will model your driver Friday or the weekend. I do not have my data and programs on the computer here.

I do have everything I need on my laptop. If all else fails everything is loaded on my big audio workstation at Benedict, and all data is backed up on that. I'm returning to Benedict, Monday or Tuesday.

Please be patient, and I will help you out.

 

[annunaki]

I just modeled this driver with WinIsd. The best compromise I could come up with for a smooth wide band frequency response was a 1.0ft^3 enclosure tuned to 30hz. This utilized a 3.0" port 18.53" long with two flanged ends. This still yields a port velocity at tuning of 25 m/s which is a bit high for my tastes but should be plenty acceptable. It would also require an infrasonic filter engaged around 25hz of at least a 12db/oct. slope. It will also require a lowpass filter at about 100hz of at least a 12db/oct. slope.

Group delay and excursion are well under control through the usable band width (30hz-100hz).

It should perform fairly well overall. Some rock wool should be utilized inside the enclosure as well as bracing as it can be utilized up to at least 120hz. Though going this high may cause some audible blooming in the frequencies above 80hz.

 

[annunaki]

For near this price the Dayton Reference series High fidelity drivers are available (10" & 12") which will provide superior performance.

The JL Audio 8W1v2-4 & 10W1v2-4 are also available at this price point which would more than likely yield superior performance from similar sized enclosures.

 

[TLS Guy]

I just modeled this driver with WinIsd. The best compromise I could come up with for a smooth wide band frequency response was a 1.0ft^3 enclosure tuned to 30hz. This utilized a 3.0" port 18.53" long with two flanged ends. This still yields a port velocity at tuning of 25 m/s which is a bit high for my tastes but should be plenty acceptable. It would also require an infrasonic filter engaged around 25hz of at least a 12db/oct. slope. It will also require a lowpass filter at about 100hz of at least a 12db/oct. slope.

Group delay and excursion are well under control through the usable band width (30hz-100hz)

It should perform fairly well overall. Some rock wool should be utilized inside the enclosure as well as bracing as it can be utilized up to at least 120hz. Though going this high may cause some audible blooming in the frequencies above 80hz.

Thanks you saved me a job!

 

[Cpt.America]

Yes, thank you... I was actually looking at the reference 8" from dayton too. For a 2.1 speaker setup for my computer listening, should I just as well build a sealed enclosure instead?

 

[TLS Guy]

Yes, thank you... I was actually looking at the reference 8" from dayton too. For a 2.1 speaker setup for my computer listening, should I just as well build a sealed enclosure instead?

I have modeled your Dayton driver. That driver is optimal for a sealed enclosure, of about one third cu. ft. It gives an F3 of 59 Hz. However the highest you can get Qtc is 0.38. a Qtc of less than 0.5 is over damped and will sound very dry.

That driver does not work well as a ported enclosure. the lowest ripple I can get is 9db. There really is no significant gain over sealed, as sealed and vented have the same output at 25 Hz, and the sealed is smoother. The vented enclosure is 0.5 cu. ft, but would require the construction of a slot vent.

I took a look at the Tang Band driver and that driver is a total waste of resources. Its parameters just do not stack up for anything promising, and any enclosure you design will not tune properly. You can not get two nice impedance peaks and QL is 7. Sealed the driver is hopeless with an F3 just below 80 Hz. I would scratch that driver straight off the list. It is not worth putting any effort into.

If I were you, I would look around for something more promising. If you are going to put sweat equity into a project, it is a pity if is hobbled right out of the starting gate. The fun of DIY is the creation of superior products.

The most promising design of your options is the Dayton driver sealed. However, as I stated I think you can do better.

If you want I can make you pdfs of the data, but I did not find those drivers promising enough to proceed further.

 

[annunaki]

I modeled the 10w1v2 & 8w1v2 they would work quite well. I did not model them sealed however.

 

[Cpt.America]

Wow. what can I say. I really appreciate all the help.. but i dont' want to make TOO big of a deal of it all. My MAIN goal, is really to be able to do something under budget. I know I can use a much better driver, but isn't the dayton $80? I understand I could run a 10w7 for $400, but that isn't what I am after. What I want, is something better than my $30 logitech sub/satalites that I am using now, that are currently starting to fail. What is in it for me, is just the challenge of finding the enclosure dimensions, buiding it out of wood (im no carpenter), and making it look as good as I can.

I guess however... that an 8w3v3 is only $120, and maybe I could even find it cheaper....

 

[annunaki]

The 8w3v3 is a nice option. I bet you can find the 10W1v2 for a lot cheaper. Put it in a 1.0ft^3* sealed enclosure and you should be set.


*Estimated, I would have to model it quick for best results.

 

[WmAx]

Wow. what can I say. I really appreciate all the help.. but i dont' want to make TOO big of a deal of it all. My MAIN goal, is really to be able to do something under budget. I know I can use a much better driver, but isn't the dayton $80? I understand I could run a 10w7 for $400, but that isn't what I am after. What I want, is something better than my $30 logitech sub/satalites that I am using now, that are currently starting to fail. What is in it for me, is just the challenge of finding the enclosure dimensions, buiding it out of wood (im no carpenter), and making it look as good as I can.

I guess however... that an 8w3v3 is only $120, and maybe I could even find it cheaper....

For a little more, you can get an Infinity Kappa Perfect 10VQ, which is a premium sound quality driver. If you wanted to compare it to JL Audio's line for example, it would be closest compared to the JL W6v2 subwoofer line. Same general level of linearity, excursion and power handling. The VQ Perfects are also very adapatable - they have a motor that can physically vary it's electro-mechanical properties to suit a very wide variety of cabinet systems. Though, this is really the class of subwoofer you use on a high end sound system, not typically for computer speakers.... lol. Ideally, you would use something like the O Audio 500 watt BASH plate amplifier with it, because the O Audio has features that make it very favorable for ideal performance (parameteric EQ band and adjustable subsonic filter) and it produces a real 400+ clean watts as measured by a credible 3rd party.

-Chris

 

[Cpt.America]

O audio???

 

[WmAx]

O audio???

http://www.oaudio.com/500W_SUBAMP.html

As for the Kappa Perfect driver: http://www.techronics.com/index.cfm?fuseaction=product.display&product_id=815&aff=45847

If you buy from Techronics, you must call and have them physically check the inventory before you pay/order. They offer one of the best prices on this product.

-Chris

 

[TLS Guy]

Wow. what can I say. I really appreciate all the help.. but i dont' want to make TOO big of a deal of it all. My MAIN goal, is really to be able to do something under budget. I know I can use a much better driver, but isn't the dayton $80? I understand I could run a 10w7 for $400, but that isn't what I am after. What I want, is something better than my $30 logitech sub/satalites that I am using now, that are currently starting to fail. What is in it for me, is just the challenge of finding the enclosure dimensions, buiding it out of wood (im no carpenter), and making it look as good as I can.

I guess however... that an 8w3v3 is only $120, and maybe I could even find it cheaper....

Here is a bunch of sub drivers, I have modeled.

Take your pick.