Does WinISD calculate Hz based upon manual entry of cubic footage of the enclosure? - AVS Forum
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post #1 of 14 Old 12-15-2014, 06:55 PM - Thread Starter
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Does WinISD calculate Hz based upon manual entry of cubic footage of the enclosure?

When tuning with WinISD, if I change the cubic footage of the box, is Hz supposed to change on its own? What if I change Hz? It doesn't. Yes, that answers me, but how do you tune? I mean there has to be a limit. If I put in 20Hz I get: the image attached.

The driver doesn't even go that low. I arbitrarily put those numbers in. Why doesn't it say it won't work?

What does that low dip before the rise mean?

How do I know if the box is "tuned" correctly?

Thanks.
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post #2 of 14 Old 12-15-2014, 07:25 PM
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Box size does not effect hz, and hz does not effect box size. Their interaction with each other changes the port size and how flat your response will be. As you're changing the box size or hz, switch over to the port info and see how that is changing. And as the port size changes the air velocity in that port is also changing. Tuning lower will reduce port velocity but the port itself starts to occupy more volume. You'll also need to account for amp power and excursion. It's a balancing act that has a good bit of wiggle room in just about any parameter.
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post #3 of 14 Old 12-15-2014, 08:04 PM - Thread Starter
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I am using this:

RSS315HO-4 High Output 12"

I put volume as 3ft^3 and 23Hz.
The slot is square and 21.75" x 2"
The rear port air velocity is right no 20
I have it at 1.0 W
Highpass Butterworth fc=20Hz

How can this be possible if Fs is 31.65 and the driver on Parts-Express shows the Frequency response is 26Hz+? I have read you can go down maybe 3Hz, but the Fs is high, so it didn't make sense.

Then I get to the vent with the numbers above and I get a vent length of 68"!

Is this part of the balancing act everyone talks about? All the numbers and graphs were good, but it would be pretty hard to build a 3ft^3 box, 23Hz with a 68" square vent (it's 612" round).
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post #4 of 14 Old 12-15-2014, 08:22 PM
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Yes, that is the balancing act. If you make the port smaller in HxW the L will also get shorter, but the air velocity will go up. You also need to enter the wattage you will be using. That will increase the velocity alot. 1 watt will not move the cone much so it wont move much air, thus low air velocity. More watts = more excursion = more air velocity.

The specs don't determine what frequency you can tune to, at least to a certain point. Tuning a tweeter to 10hz is probably impossible.

You can probably find some other ported builds around with that driver if you search. I usually use google to search this site.


https://www.google.com/?gws_rd=ssl#q...w.avsforum.com
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post #5 of 14 Old 12-15-2014, 08:31 PM
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Changing the box size doesn't affect the tuning because when you change the box size the program changes the port dimensions to maintain the tuning at the chosen value. By the same token changing the tuning frequency doesn't change the box size, as it also changes the port dimensions to maintain the same box size.
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The driver doesn't even go that low. I arbitrarily put those numbers in. Why doesn't it say it won't work?
It will work. You can run a driver well below Fs using an LLT alignment. The box has to be very large, but it will work. The RSS 315HO is maximally flat in 1.2 cu ft with a 31Hz Fb, giving a 30Hz f3, but it's quite capable of going to 20Hz with an18Hz f3 . You need to use a 6 cu ft (net) box, and it won't be flat, but it will work.
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post #6 of 14 Old 12-15-2014, 08:36 PM - Thread Starter
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What does it mean when everyone says "it won't be flat"? I read that a lot.

edit: Can you tell me what it means if it is not flat but bumps up in a peak? What would that mean for hearing/feeling the sound?

Samsung 51" PN51E450A, Pioneer VSX-918V, Polk Tsi300, Polk CS 2 series ii center, gonna get a sub...one day.

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post #7 of 14 Old 12-15-2014, 09:38 PM
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Quote:
Originally Posted by likemovies View Post
I am using this:


How can this be possible if Fs is 31.65 and the driver on Parts-Express shows the Frequency response is 26Hz+? I have read you can go down maybe 3Hz, but the Fs is high, so it didn't make sense.

Then I get to the vent with the numbers above and I get a vent length of 68"!

Is this part of the balancing act everyone talks about? All the numbers and graphs were good, but it would be pretty hard to build a 3ft^3 box, 23Hz with a 68" square vent (it's 612" round).
1. Fs is just what the natural resonance of that speaker is, the exact point where the speaker is the most efficient in free air. For example it may take 10 watts at 31.65Hz to get the same volume as 100 watts at 80Hz or 10Hz. <just making up #'s for an example but that's how it works. Look at the amplifier apparent load tab in winisd. Your speaker will play 5Hz, just at a low volume and with a lot of power...compared to at 31.65Hz. The 26Hz should be the point where the same power makes 3db less output than the rest. The -3db point.


2. Rule of thumb: Keep vent length for a sub that is crossed over at 80hz less than 40" (1st port resonance on the port tab). Keep port velocity less than 17meters/second.


3. a balancing act, definitely
When box volume goes up: port length gets shorter
When port area is reduced: port length gets shorter
When tuning is increased: port length gets shorter


works the other way around too


When port area is reduced: Air velocity goes up
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post #8 of 14 Old 12-15-2014, 09:58 PM
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Quote:
Originally Posted by likemovies View Post
What does it mean when everyone says "it won't be flat"? I read that a lot.

edit: Can you tell me what it means if it is not flat but bumps up in a peak? What would that mean for hearing/feeling the sound?

When you use an undersized ported box the graph will look like a big arch. With a larger box the graph will table-top and have a long flat section. You want the long flat section, but eq can fix alot if you have power and the driver can handle it. The room will ruin that nice graph anyhow, but it helps to start off with something kinda flat.
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post #9 of 14 Old 12-15-2014, 10:11 PM
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Quote:
Originally Posted by likemovies View Post
What does it mean when everyone says "it won't be flat"? I read that a lot.

edit: Can you tell me what it means if it is not flat but bumps up in a peak? What would that mean for hearing/feeling the sound?
Flat means all the frequencies are the same db level/volume till the point where it starts to roll off downward at the low frequencies.


Your ears are less sensitive to the low frequencies. So some people like having a rise in the lower frequencies.


If there is a BIG bump like 6db at 50hz it will sound like the "one note" car stereo box. Where one frequency is way louder than the others and all the bass seems to sound the same.
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post #10 of 14 Old Yesterday, 06:08 AM
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I love that you are trying to learn!

I'm not sure you need to though, given your budget I'm not sure you'll do better.

On the bottom end of price, the infinity 1260 tuned in a 24" cube @20hz reigns. And your next step up is the SI18" in the same Marty style box. There's tins of proven designs kicking around- just copy them. The Johnny cube with SI 18 it great too, I doubt you beat that for the $
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post #11 of 14 Old Yesterday, 05:24 PM - Thread Starter
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Originally Posted by Mfusick View Post
I love that you are trying to learn!

I'm not sure you need to though, given your budget I'm not sure you'll do better.

On the bottom end of price, the infinity 1260 tuned in a 24" cube @20hz reigns. And your next step up is the SI18" in the same Marty style box. There's tins of proven designs kicking around- just copy them. The Johnny cube with SI 18 it great too, I doubt you beat that for the $
I don't Think I'll do better. I just really like knowing why I'm doing things. I went back and read the things you said. Very helpful. Time to build and get on with it๐Ÿ˜ƒ

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post #12 of 14 Old Yesterday, 05:49 PM
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Quote:
Originally Posted by likemovies View Post
I don't Think I'll do better. I just really like knowing why I'm doing things. I went back and read the things you said. Very helpful. Time to build and get on with it๐Ÿ˜ƒ
I'm very new to DIY and WinISD myself. After playing with it for a few weeks I found that paying attention to SPL, Port Velocity and Cone Excursion are very important when changing the box parameters (ft^3, port size, etc.). I'm building a box based on the 24" cube with an Infinity 1260 as @Mfusick mentioned, but adjusted HWD to fit the spot I have.

If you have the time and materials, maybe think about building a test box. I put one together with some particle board I had down in the shop and an old plate amp I had lying around, just to make sure I wasn't building something that couldn't possibly work. Now that I'm getting the hang of WinISD the next build will be the final product, and I won't make the same mistakes (I hope!) that I made when building the test unit.
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post #13 of 14 Old Yesterday, 08:16 PM - Thread Starter
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Quote:
Originally Posted by smcmillan2 View Post
I'm very new to DIY and WinISD myself. After playing with it for a few weeks I found that paying attention to SPL, Port Velocity and Cone Excursion are very important when changing the box parameters (ft^3, port size, etc.). I'm building a box based on the 24" cube with an Infinity 1260 as @Mfusick mentioned, but adjusted HWD to fit the spot I have.

If you have the time and materials, maybe think about building a test box. I put one together with some particle board I had down in the shop and an old plate amp I had lying around, just to make sure I wasn't building something that couldn't possibly work. Now that I'm getting the hang of WinISD the next build will be the final product, and I won't make the same mistakes (I hope!) that I made when building the test unit.
Thanks. Make sure you post pictures when you're done.

Samsung 51" PN51E450A, Pioneer VSX-918V, Polk Tsi300, Polk CS 2 series ii center, gonna get a sub...one day.
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post #14 of 14 Old Today, 06:20 AM
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Quote:
Originally Posted by smcmillan2 View Post
I'm very new to DIY and WinISD myself. After playing with it for a few weeks I found that paying attention to SPL, Port Velocity and Cone Excursion are very important when changing the box parameters (ft^3, port size, etc.). I'm building a box based on the 24" cube with an Infinity 1260 as @Mfusick mentioned, but adjusted HWD to fit the spot I have.

If you have the time and materials, maybe think about building a test box. I put one together with some particle board I had down in the shop and an old plate amp I had lying around, just to make sure I wasn't building something that couldn't possibly work. Now that I'm getting the hang of WinISD the next build will be the final product, and I won't make the same mistakes (I hope!) that I made when building the test unit.
If you ask a manager at HD they will give you a discount on MDF with the damaged corners. If you have table saw, just rip it off. A tad more work but if your are on a budget can help.
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