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post #1 of 79 Old 11-28-2013, 08:45 PM - Thread Starter
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Alright, so last year I built a new sub based on the new Datyon Reference 18''. The sub has been amazing! However, due to several factors it is not reaching as low as I would like. I have amazing bass response down to the mid 20's, but then it drops off quickly. I've been hankering to build a new sub and I need to learn how to make a good ported box. With the advent of the Ultimax 15'' I had to give it a crack.

I just have a host of questions that may seem very uneducated; i am a beginner at building and modeling.

According to this online calculator using the Thiele small parameters, a ported version of the Ulitmax 15'' could reach down to 18Hz with an 8 ft^3 box. Dayton actually released some guidelines saying the cabinet would need to be 11.1 ft^3 to reach down to 17Hz. I'm not sure exactly why they suggest a box so large. They also recommend two 4'' flared ports, which according to the first calculator should be 19.2''. Here starts my list of questions:

  • How exact does the port length need to be? Does an inch variance make a huge difference?
  • How would one position two ports on a box? Is it bad form to have them both venting on the front or should I split it between sides?
  • When calculating port length for two ports is the length for each port, meaning do I need two 19.2'' of 4'' diameter port, or do I need a total of 19.2'' of 4'' diameter port between the two?
  • Also, when calculating box volume, I assume that this is the volume of the box minus bracing, the driver, amp and port volume?

I think that is my list of questions for now, though I probably will have more later. I'm modeling some box designs that I would appreciate some feedback on when I get to that point.
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post #2 of 79 Old 11-28-2013, 09:05 PM
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" Dayton actually released some guidelines saying the cabinet would need to be 11.1 ft^3 to reach down to 17Hz. I'm not sure exactly why they suggest a box so large."

that's a martysub! :-)

there are several flavors of it, but the key idea is here:

http://www.avsforum.com/t/1489541/large-ported-dayton-ho18s#post_23711347

the um15 actually works quite well in it. here it is with 500 watts.


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post #3 of 79 Old 11-28-2013, 09:09 PM
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"•How exact does the port length need to be? Does an inch variance make a huge difference?"

thinking about it in terms of percentages is a little better. 1 inch on a 3 inch long port is a big deal. 1 inch on a 36 inch long port is nothing to worry about.

"•How would one position two ports on a box? Is it bad form to have them both venting on the front or should I split it between sides?"

both on front can be fine. or like the martysub, you could just do a slot port.

"•When calculating port length for two ports is the length for each port, meaning do I need two 19.2'' of 4'' diameter port, or do I need a total of 19.2'' of 4'' diameter port between the two?"

in the calculator, if you entered 2 ports, then the length is for each port.

"•Also, when calculating box volume, I assume that this is the volume of the box minus bracing, the driver, amp and port volume?"

yep. you've got it right.

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post #4 of 79 Old 11-28-2013, 09:10 PM
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btw, the 18ho works great in the martysub too. you will pick up something like 10db or so around the tuning frequency and that is quite a bit. since you already have that driver, might want to experiment with it.

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post #5 of 79 Old 11-28-2013, 09:23 PM - Thread Starter
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Awesome, thanks so much for your replies LTD02. That answers a lot of my questions. I curious why you modeled the 15'' with 500 watts. I was planning on driving the 15'' in a series (4ohm) using the Dayton SPA1000 given the Ultimax's RMS of 800. Would the extra power from the amp drive the response frequency any lower?

Also, space is somewhat of a concern. I'm in a huge room right now, but i'm planning on moving in the next year and i'm not sure exactly what i'll have. Is the 11 ft^3 box necessary to achieve some <20hz response, or would a less cool-ly named 8 ft^3 accomplish the job?
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post #6 of 79 Old 11-28-2013, 10:21 PM
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" I curious why you modeled the 15'' with 500 watts."

semi-random round number because in a large enclosure, it takes less power to move the driver to xmax. 500 watts moves it to about 19mm, so it could go a little further if you want. 1000 watts would be really pressing your luck.



"would a less cool-ly named 8 ft^3 accomplish the job?"

sure. just takes a little more power because a smaller box is a little less efficient. we can model it up and see how it does.

also, with a plate amp, there is going to be a high pass filter, typically around 20hz. some of them can be modified. some cannot. I'm not sure about the plate that you mention.

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post #7 of 79 Old 11-28-2013, 10:26 PM
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here is 8 vs 11 cubic feet



now the primary problem that starts to creep in the port grows in proportion to the decrease in cab size for a given tuning.

the port in the marty is 36" long iirc. dropping size to 8 cu ft and keeping same tuning and same size port, length must grow to about 53" or so. so that is something else that is going on "in the background" of the design.

I'm sure we can find something that works for you...

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post #8 of 79 Old 12-02-2013, 08:55 AM - Thread Starter
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Alright, I'm back from the Holiday weekend and I have some more information. After a lot of reading and also looking at my room, i decided that i'm going to go with a larger enclosure. However, I'm toying with the idea of putting the woofer on the 48''x24'' side, not the 24''x24'' side. This works a lot better with how my room is set up.

I was thinking of splitting the 48'' side into two logical 24'' parts, centering the woofer in one side and the ports in the other side. According to the dayton ultimax specs:

"The largest recommended cabinet is 10.5 cubic feet tuned to 16 Hz using two 4" diameter ports that are 21" long for an f3 of 19 Hz."

So, I have two options. I can tune the ports to 16Hz and go 21'' long, however, there will be <2'' between the port and the side of the enclosure since they are going in the 24'' deep part. Will that small of a space cause problems with port velocity? If so, i can tune it to 17Hz and go with 18.3'' long ports, though i'm sure i'd increase my f3 at that point.
Quote:
also, with a plate amp, there is going to be a high pass filter, typically around 20hz. some of them can be modified. some cannot. I'm not sure about the plate that you mention.

I could not find any definitive answer on the inter-webs for this so i email parts-express tech. Here's their response:
Quote:
Hello,
The Rumble filter is set ay 18 hz on this amplifier. For any use under 20 hz I would certainly go with a pro audio amplifier. They have a bit more headroom, and no filtering at all.

Regards,
Chris Frechette
Technical Advisor
Parts Express

So my plan now is to use a Crown XLS 1500 with the voice coils wired in series. That will give me 1550W @ 4ohm which is perfect since the driver peaks out at 1600W. If anyone is aware of issues with this pairing please speak up! With this driver being so new it's hard to find a lot of builds using it.
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post #9 of 79 Old 12-02-2013, 01:34 PM
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the risk with the high power is overshooting the excursion by too much.

I'm not sure what the limit is on that driver, but back in post 6, there is a rough estimate of what you are looking at.

shouldn't be a problem unless you are going crazy with the volume. just a heads up.

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post #10 of 79 Old 12-02-2013, 02:12 PM
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Dayton actually released some guidelines saying the cabinet would need to be 11.1 ft^3 to reach down to 17Hz. I'm not sure exactly why they suggest a box so large. .
Because the driver EBP is only 33, making it optimized for a sealed cab. Vented works best with EBP of 60 or higher.

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post #11 of 79 Old 03-10-2014, 08:47 PM
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Jeremy did you end up building a ported cab for the um15? I have the same sub and 1000 watt plate in a 4cuft sealed box and was thinking of building a ported cab also.
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post #12 of 79 Old 03-10-2014, 09:08 PM - Thread Starter
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I didn't, ended up with a dual passive radiator setup w/the tc sounds lms ultra 5400. With such a low ebp, the cabinet was just too large ported to get the freq extension I wanted with this project. I'd say unless you're willing to triple the volume of your enclosure, just keep it sealed and look to another driver for low freq extension

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post #13 of 79 Old 03-10-2014, 09:14 PM
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I was thinking about doing a full Marty enclosure. I could make room for it. Not sure if the Dayton 1000 watt plate amp would be too much though?
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post #14 of 79 Old 03-10-2014, 09:49 PM - Thread Starter
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Well, grab winisd and do some modeling! :-) maybe tomorrow night I could throw in some numbers for you, but it's a good exercise to figure out how to use it if you really want to get some good science behind your build. Regardless, you'll need some sort of high pass filter with the port or you could blow the driver at low freq. You can get some in line ones down to 20hz, if you want lower we can talk other options. If you can fit it, the Marty sub is a very straightforward build the doesn't require a lot of tools. Just depends on what you want from this build. Are you looking for more spl? Do you want lower freq extension? Typically you'd migrate from sealed to ported to get that nice sub bass, but how low do you want to push it, and at what spl? These questions should be the driving factor behind your design

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post #15 of 79 Old 03-10-2014, 11:08 PM
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Well, grab winisd and do some modeling! :-) maybe tomorrow night I could throw in some numbers for you, but it's a good exercise to figure out how to use it if you really want to get some good science behind your build.

+1 It's very good to look at the different options and see how they all correlate and interact when changes are made.

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post #16 of 79 Old 03-11-2014, 04:22 AM
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Sealed for me gets loud enough just want it to get down to 20 hz or so. I will try winisd again but haven't had any luck with it before.
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post #17 of 79 Old 03-13-2014, 06:17 AM - Thread Starter
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I will try winisd again but haven't had any luck with it before.

Haha, that was me a year ago. I completely understand, it has a pretty steep learning curve. I actually write software for a living and I have been tinkering with doing a much better version of winisd on the web so that everyone can use it, but it's still a long ways out. When working with winisd, i constantly go back to this forum post for help.

http://www.hometheatershack.com/forums/diy-subwoofers-general-discussion/6330-winisd-pro-tutorial-download-detailed-guide-how-use-winisd-pro.html

It tells you the order to enter the data from the specs in order to get a new driver into the program.

If you are only looking to go down to 20Hz, then an in-line, passive crossover is a pretty cost-effective HPF. You can look at these guys. I'm so busy lately I won't be able to get in and do any modeling for you, but from what I remember of the ultimax and the marty sub you should be able to hit 20Hz in an 11ft^3 enclosure with that amp. I'm not sure about excursion though... The ultimax is not a high-excursion sub and you usually need that when looking to push sub 30. Just make sure that you check the cone excursion in winisd. The typical option is to plan for manufacturer xmax + 10%, but I always stay at modeling against the xmax and hoping that I don't make more than 10% of a mistake wink.gif

Also, check your port air speed and try to keep it under 60ft/s.
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post #18 of 79 Old 03-13-2014, 07:25 AM
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I don't think I would have any problems figuring out how to use winisd if the program itself would stop giving error messages and locking up.
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post #19 of 79 Old 03-13-2014, 07:34 AM
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I don't think I would have any problems figuring out how to use winisd if the program itself would stop giving error messages and locking up.

I had that same problem and was advised to go to winisd properties and set compatibility to what windows program your running.

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post #20 of 79 Old 03-13-2014, 08:06 AM - Thread Starter
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I don't think I would have any problems figuring out how to use winisd if the program itself would stop giving error messages and locking up.

That's why i've been working on writing a new one. I mostly just need to carve out time from my schedule to do it.
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post #21 of 79 Old 03-13-2014, 05:48 PM
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I'm not seeing a properties tab. Where do i go to make sure winisd is set up correctly for my computer?
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post #22 of 79 Old 03-13-2014, 06:18 PM
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I'm not seeing a properties tab. Where do i go to make sure winisd is set up correctly for my computer?

The version of WinISD you're using is an obsolete one. One can tell by the color of the graph - a green grid on a black background. The WinISD developers have stopped maintaining their website, and as a result, it links to an obsolete version which crashes under Vista and later Windows versions. The latest version is 0.7.0.900 and can be found here: https://www.facebook.com/WinISD

The latest version needs no workarounds. It works fine as-is under Vista and Windows 7.

Edit: I provided more detail about it in a post to Steve nn a while back.
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post #23 of 79 Old 03-13-2014, 06:23 PM
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Thanks for the reply. Is there another way to get it? I don't have Facebook
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Thanks
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post #26 of 79 Old 03-13-2014, 07:03 PM
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Got driver parameters entered and made it to this screen. Not sure what to do now.
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post #27 of 79 Old 03-13-2014, 07:40 PM
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Choose "box" toward the lower left, then just experiment with different values of box volume and box tuning frequency. It might make sense to first pick a box tuning frequency of, say, 17 Hz, then play around with the box volume to see what you can get.
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post #28 of 79 Old 03-13-2014, 08:33 PM
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If I'm doing this right I probably should just keep it in the sealed box. 17 hz tune, 950 watt and 11 cuft


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post #29 of 79 Old 03-16-2014, 10:23 AM
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Did some more modeling on winisd. At 950 watts in 10 cuft net with a 2 inch tall, 21 inch wide and 30 inch deep slot port I'm hitting 24mm excursion. 5mm over the published spec of my driver. Was told by pe and someone on another forum to go for it. Not sure if I should chance it. Don't want to break anything. Is 5mm over xmax too much?
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post #30 of 79 Old 03-16-2014, 11:42 AM
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Originally Posted by swc11 View Post

Did some more modeling on winisd. At 950 watts in 10 cuft net with a 2 inch tall, 21 inch wide and 30 inch deep slot port I'm hitting 24mm excursion. 5mm over the published spec of my driver. Was told by pe and someone on another forum to go for it. Not sure if I should chance it. Don't want to break anything. Is 5mm over xmax too much?
What that tells you is don't run it at 950w. Since it's an 800w driver that's pretty much a given anyway. cool.gif

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