Building an enclosure this weekend

[WmAx]

The 4" port is not going to be big enough. You need to use 2 3" or larger ports, if you dont, it's going to chuff like crazy.

This depends on the specific execution. With a moderate SPL woofer such as the one dicussed here, one can use a 4" port with router flanged termination plates on both port ends, and use a port with no bends or abrubt points for air to be disturbed, and chuffing is not a problem. One can get up to one bend(main problem with bends is the rough transistion edges when you use the elbow connector) and have minimal chuffing(only audible with test tones). Of course, on very long ports with multiple bends, the problem is vastly more likely to occur(as has already been outlined in this thread).

-Chris

 

[MacManNM]

This depends on the specific execution. With a moderate SPL woofer such as the one dicussed here, one can use a 4" port with router flanged termination plates on both port ends, and use a port with no bends or abrubt points for air to be disturbed, and chuffing is not a problem. One can get up to one bend(main problem with bends is the rough transistion edges when you use the elbow connector) and have minimal chuffing(only audible with test tones). Of course, on very long ports with multiple bends, the problem is vastly more likely to occur(as has already been outlined in this thread).

-Chris

You are correct if you assume he is building a small box ~1cu ft, and using external vents. I hardly see him building a 1ft^3 with a 40" tube sticking out the top. The logical thing to do is increase the box size and decrease the port length. When this happens he will have to use a larger diameter of port. If you have some magical way to keep the port velocity down to a reasonable number, then I would love to hear it. The EBP of this woofer is 67 which lends itself to a sealed enclosure. This is why the transform circuit is probably the best choice for high fidelity sound. Or a 1 ft^3 box with a 4" pipe sticking out the top. I guess you could paint it to look like a woodstove, that might help out the WAF.

 

[bmccord]

HAHA, that made me laugh pretty hard. I could put a cast-iron door on the front of it...Any who, didn't build a box yet. Too much other stuff going on. What is a passive notch filter? My primary goal is to get a slow as possible while maintaining flat SPL's. Thanks a bunch.

Brett

 

[MacManNM]

HAHA, that made me laugh pretty hard. I could put a cast-iron door on the front of it...Any who, didn't build a box yet. Too much other stuff going on. What is a passive notch filter? My primary goal is to get a slow as possible while maintaining flat SPL's. Thanks a bunch.

Brett

If you aren't looking for a ton of spl, and just a pretty flat response, Id go sealed with one of these:
http://www.rythmikaudio.com/nonservo_product.htm

This will flatten out the response, and as long as you aren't pushing it really hard will keep distortion pretty low.

 

[bmccord]

Yeah, the primary goal of this project was max. shear SPL but still have a flat of a curve as possible. Hense the funny sized box. Also, I read that the "optimum" sealed volume for this driver is .7 cu.ft. but if a larger box always sounds better, why did they spec it that small. Would I be better off building a 2-3 ft^3 box and working in 3 - 3" ports at optimum lengths?
Thanks

Brett

 

[MacManNM]

Yeah, the primary goal of this project was max. shear SPL but still have a flat of a curve as possible. Hense the funny sized box. Also, I read that the "optimum" sealed volume for this driver is .7 cu.ft. but if a larger box always sounds better, why did they spec it that small. Would I be better off building a 2-3 ft^3 box and working in 3 - 3" ports at optimum lengths?
Thanks

Brett

It's not all about box size. It's a balance between woofer characteristics, box size and vent size/length. I'm still not sure what you are trying to accomplish here. You can't have it all, if you want more SPL you are going to have to sacrifice something. Do you have any numbers in mind (SPL levels)? What do you want the 3dB point of the box to be?

 

[bmccord]

Well, as far as the 3dB point goes, nothing rediculously low. Maybe 24-26 would be super but I gather I will have to sacrafice some overall SPL to achieve that low Hz. SO, basically, the idea here is to make a house shaker. This is more or less a temp sub until I spend the money on 2 - 12's and a 1000w amp to make my beast that I have been working on. So, to recap, the overall goal is to shake the house with music (not very low Hz demanding) as well as with movies. That is were thr 24-26 Hz comes in. I listen to jazz, classical, rock and movies at reference level on a regular basis to it needs to be able to hold its own with the rest of my system.

Brett

 

[jonnythan]

Do you already have the Titanic driver? According to WinISD it's almost impossible to put into a vented enclosure and get the response you want.. the Dayton 10" High Fidelity driver would get you way more SPL at even lower frequencies than the Titanic. A box that's 1.9cf with 1 3" vent 18.23" long will get you an F3 of 22Hz with a flat response curve and 3dB more nominal output.

In any case I suggest you download and learn to use WinISD.

 

[bmccord]

Yes, I already have the 10" Titanic and the Dayton 240w plate amp. I bought the driver before I really knew what the specs meant... Oops. For my next project, I am using 2 - 12" High Fidelity's but for now, I just want to maximize what I have...

 

[bmccord]

OK, I was just thinking about this some more. This project I feel should be geared more towards maximum musical output. I am building a much bigger sub in a few months with the sole purpose off maximum depth...(movies). So, new goal. Max SPL for music. I am guessing that shifts the tune to the low 30's. Now, with that as the primary goal...medium box size and lots of porting? It almost seems like my original box design with 3 3" ports at around 35" would be a pretty good layout. Maybe just making it 1.25-1.5 ft^3 may be better. Please correct me if I am wrong.

Brett

 

[MacManNM]

I have modeled this woofer in a bunch of different configurations, and in reality, it works best with a 4" diameter 40" long port with a 1.5ft^3 enclosure. In this configuration you are only using about 1/3 of the drivers excursion capabilities at 30hz, while producing 104dB SPL with 200 watts into it. The response model is very clean. I would try building the box and putting the port on the outside, just use a piece of PCV. I bet it will sound awesome. See if the design works and then figure out a way to do it better aesthetically, or if there is something you are willing to sacrifice.

 

[bmccord]

What about 3 3" ports and a 1.5 ft^3 enclosure at whatever length needed. I only say this because with the enclosure it is in now, it has a 4" port and it huffs like an emphasemic marathon runner

 

[Mr. Lamb Fries]

what about using a sonos tube for it? I think it would look better than the wood stove sub (LOL by the way). It might be able to keep the port inside the enclosure!??

I am very interested in your second project- 2X12" & 1000 watt amp...Keep us posted!

 

[bmccord]

I don't like the looks of a tube and as for the port being almost 4 feet long, it would be a "U" shaped piece and within a sencondary box to hide it. As for the 2- 12" project...haha, it's more or less a poor mans version of the PB12 plus/2 using 2 dayton 12" high fidelity's and the dayton 1000w plate amp all in a 7.4 ft^3 enclosure. Now thats a dog house.

Brett

 

[MacManNM]

What about 3 3" ports and a 1.5 ft^3 enclosure at whatever length needed. I only say this because with the enclosure it is in now, it has a 4" port and it huffs like an emphasemic marathon runner

This is because you have it in a bandpass box, this is causing the woofer to have an incredible amount of gain, thus it is pumping more air in a smaller (narrow) band.

To do 3- 3" ports you are looking at 50" of length, with a 1 ft^3 box. Making the box larger increases the gain @~40hz.

I would still go wit a 1 ft^3 box with a 4" 40" long port. At 200w, the air velocity is 18 m/s not enough to make any noise. Like Chris said, you can treat the ends of the ports and then you will have no worries about port noise.

 

[bmccord]

That is also very true. I sat down for a couple hours last night and came up with a box that is 1.65 gross interior volume, and with 3 3" ports @ 36" and has a pretty decent curve. It has a 1.6 dB crest at 31 Hz but then is flat after that. After you take the volume of the ports, amp and sub out, you ar left with 1.2ish ft^3. I think this will work and cut the amount of wood in half because i just used i divider plate in the middle to seperate the ports from the main enclosure space. Thanks

 

[jonnythan]

I think that 3 ports are pretty excessive for what you're doing.

 

[annunaki]

I think that 3 ports are pretty excessive for what you're doing.

I completely agree.

 

[bmccord]

True, however when I was speaking of using 2 3" ports, everyone was saying that it would make all kinds of noise. I also do not want to have to use a 40" long piece of 4". So...whats the plan. Will 2 3" ports be ok then?

 

[bmccord]

bump...loving the feedback