View Full Version : Help with first ported box
01-27-2012, 01:46 AM
I've always run sealed subs and never had a complaint but I want to get a ported box going. I'm going to be running 2 different setups. One will be between 1-1.5 cubes sealed for when the wife wants the trunk and the other will be the ported. I'm thinking 3 cubes tuned really low.
The sub is a Shiva X2(best sub ever) and I plan on feeding it 1000 watts. I have 2 3" precisionports from partsxpress that I can use and winisd says they need to be 10.36" long for 24hz if I use one, or 23" long for 2. My question is, is this right? Will I have port noise with just one?
01-27-2012, 03:03 AM
For this driver, if you were to wire it parallel or series, the best option for ported would be 2.23 cubic ft and a 38Hz tuning on 26.58 V. But, you will get a better transient response with only a small loss in output(3-5B from 35-50Hz), then tune to 30Hz.
You can do this by using a port of a little over 60 square inches.
BUT, for 2-3" precision's, you will get port noise, yes. On this voltage anyhow. Also, with 2-3" ports, your response will only be best at 45-63Hz anechoically.
And if you tune them to 30Hz, your best output will be from 28Hz-43Hz anechoically.
I recommend using 60 square inches, or at least 2-6" ports.
Hope that helps a little. :D
01-27-2012, 03:17 AM
A 2.23 cube box with 2 6" ports tuned to 30 shows it needing 71.23" in winisd. That's too long for my plans. http://www.diycable.com/main/pdf/Shiva-X2%20App-note.pdf has some guidelines for designs and has one for 3 cubes with one 4" port if you keep it under 500 watts tuned to 22hz. Why would there be such a difference with going to 1000 watts?
01-27-2012, 03:37 AM
Yes, the port can get long if you want to keep response smooth. A smaller chamber, with a longer port is ideal for this application, but if you were to go larger, the recommended size I have for 30Hz is around 3.61 cubic ft and for 2-6" round ports, you can get a smaller length. Larger volume with a constant port will lead to smaller lengths. I would not recommend any other volumes than those two. So, for 38Hz, use 2.24 cubic ft, and for 30Hz, use 3.61 cubic ft. Those are optimal for this driver regardless of port length.
With all of the limitations listed, I could get more detailed, but that would require a design purchase. This would allow me to further utilize the limited port length to accommodate it with volume and placement for achieving the proper tuning and response. But if you want to use other recommendations, fill free.
I just figured I would help as much as I could without getting involved in the design process. :D
I would not tune to 22Hz though. that is not a personal preference, but based on proper parameters. personal preference can obviously be used though, just giving my recommendations.
The difference, by the way, is with mechanical limitations. By increasing voltage, you increase the possibility of over-excursion. And with a design that utilizes a round port and being that it is conventional, below tuning and a bit above, excursion is increased quite quickly. So, basically, the applied voltage is taken place by efficiency. Less needed power means less excursion limits reached, and more efficiency means less needed power.
01-27-2012, 03:52 AM
I do appreciate the help, it just seems some of your measurements go against the sub designer's. Are you sure you have the specs for the X2 and not the original?
01-27-2012, 04:23 AM
Parameter Single Coil Parallel Series
Re: 1.9 Ohm 0.95 Ohm 3.8 Ohm
Le: 0.475mH 0.238mH .95mH
Fs: 21.3Hz 21.3Hz 21.3Hz
Qms: 3.09 3.09 3.09
Qes: .9 .45 .45
Qts: .7 .39 .39
Mms: 206g 206g 206g
Cms: 0.27 mm/N 0.27mm/N 0.27mm/N
Sd: 506 cm^2 506 cm^2 506 cm^2
Vas: 97L 97L 97L
BL: 7.65 7.65 15.3
X-Max: 30% down point on BL Curve 26mm 26mm 26mm
Pmax: (Read our notes on power
1000W 1000W 1000W
SPL: 85.1 dB 1W/1M (in series)
Volume Occupied by Driver .13 cubic feet
This is the x2. If these are incorrect from what you are using, then I understand the confusion. otherwise if they are correct.read on...........
quote: " it just seems some of your measurements go against the sub designer's" And hence the reason why no one on here will find another designer like myself. If you want to be stereotypical, that's fine. Take it from someone who is an acoustical engineer and with military sound experience as well as college training in electronics. Take my advice or not. Either way, I can say I still attempted.
I think others on this forum can easily vouch for my degree of acoustic knowledge.
I do not mind if you do not use the help, that is at your discretion. So, I am not upset if you do or not.
And yes, my requirements do go against the designer of the subwoofer for a very good and logical reason. Because they do not take into a lot of factors that I figure for. They base their responses on an anehcoic .707Q response curve, which I can guarantee will not look the same when loaded. Nor will it act the same. They do not take into consideration driver limitations by purposely limiting them so they can guarantee that their specs will not damage the drivers. but they do not calcualte for the given leeway of efficiency that they are fully capable of. The designer/manufacturer of the drivers give them a safe zone, not realizing that with proper application parameters, the safe zone is too much of a limit. They worry too much about excursion not taking into consideration the full capabilities and differences between linear and non linear response.
Trust me. I know what I am doing.
I am not in a quarrel about your comment, but I do hope to begin to realize that manufacturer specifications are far from ideal in most cases of audio because they want to make sure that if you design a box they recommend, that you get a stereotypical response and that you do not have to return a damaged item that falls within their return policy, by either overpowering them, or by defect of the design or driver.
So, they make sure that the driver has compression limitations, as well as tuning and control limits over what they are really capable of and pay no attention to efficiency and loading effects of even some more non conventional styles.
Is that helpful to your concern?
01-27-2012, 04:36 AM
Yes, thank you for your time and I will take it all into consideration.
01-27-2012, 04:39 AM
You are very welcome! I hope you get it figured out and get yourself a great design going! Have a great weekend. :D