Building an enclosure this weekend

[bmccord]

Hello all. I am finally building my enclosure for my 10" Dayton Titanic this weekend. Basically, it is a .85 ft^3 box within another box concealing the port system. I want a big as possible port as to minimize any port noise. I designed the box in WinISD or whatever that program is called and came up with 2 - 3" ports at 44" long. Therefore, I just made a pho-box to hide the extra long port in atempt to maintain the lowest tune and lowest vent "mach". Do you think 3" is too big of a diameter? My other option is 2.5" diameter, but I think 3" will be fine. Oh yeah, the ports are just going to be PVC pipe with radiused pipe ends...

Here is the design thus far. Feel free to add your $.02

http://images6.theimagehosting.com/10-titanic.jpg (http://www.theimagehosting.com)

[WmAx]

3" is fine. But you may end up with some port chuffing at low frequency test tones at high amplitudes, due to the small edges of the pipe combined with the air velocity. You could drasticly reduce the chance of this by using the special flare ends sold on speaker DIY sites, or you could make some flare ends on a wood lathe. You could even do better than the small edges of the pipe by terminating the pipe to the back of a 3/4" board and using a roundover router bit to get a radius at least bigger than the radius possible on just the pipe wall end. Note: the chuffing is not likely to be audible with actual music and movie program material. Test tones make it much easier to hear such artifacts.


-Chris

[bmccord]

my thoughts exactly, i figured I would get a little with PVC, but I dont have much else to work with that doesn't cost an arm and a leg. I was going to round the pvc inlet and outlet ends to almost nothing and with 3", I was hoping there would be very little. It may be audible at a 25 Hz tone but in a movie or music, I would thing it would be far from noticable. Who knows... I hope this thing works out. The way it is layed out is supposedly tuned to 26 Hz so we'll see. Thanks.

Brett

[j_garcia]

It seems like you have room, why not larger diameter ports that aren't as long?

I don't understand your bracing? Is the driver in another enclosure or will that bracing be routed out so the driver is open to the whole volume?

[WmAx]

It seems like you have room, why not larger diameter ports that aren't as long?


If you increase port diameter, you have to increase the length to get the same tuning frequency as the smaller diamater port.

-Chris

[bmccord]

The sub is in the small box all by itself. However, it has a perpindicular brace within the small box because the top and bottom side is 19" long. The outer box does nothing but enclose the port system. It doesn't even need to be there and the sub would repond the same, just for looks. As for the port Diameter, according to the software, the larger the Dia, the longer the ports would have to be, as when I set it to 2.5" dia, the overall length was reduced by almost 10".

Brett

[j_garcia]

I've never designed a ported sub only sealed, so not familiar with the fact that larger diameter would need a longer tube. Interesting...seems like it would be the other way around. Anyway, how did you arrive at the 26Hz tune? Is there a "best" tune for that driver in a given box? That seems like a LOT of port length to arrive at a 26Hz tune. Definitely look at flaring the ports somehow, as I have at least read a little about port types (slot loading, port, transmission line, etc...) and it showed the ideal port has a strange, non-linear shape that is flared on both the inlet and outlet and compresses in diameter toward the middle of the length. It said that flared ends on a standard port will definitely help with port turbulence though.

[jonnythan]

40 inches seems awfully long.

Post some screenshots from WinISD.

edit: Just saw that the sub box is .85cf. It looks like you have a much larger box around that...

I don't get what you're trying to do. If you simply got rid of the inner box and made a 2cf box, you could probably get by with a single 4" flared port and avoid a lot of complication, right? Plus you'd get better low end..

[j_garcia]

The larger box is just to house the ports due to their length. Seems to have a nice look to it, but also looks like an overly complex design. Why are there TWO ports that long? I agree with jonnythan, if you're already building a larger box, why not just USE that volume?

[bmccord]

Well, not sure really. I just saw in the driver specs for the Dayton 10" Titanic that the optimum ported volume is .70 ft^3 and WinISD came up with .85 so I just stuck with it. Then came the porting. I wanted 2 - 3" ports so that port huffing would be at minimum. Then, per WinISD to use 2 - 3" ports, it said they need to be lik 43" long or something of that nature. Obviosly a larger box will net lower Hz but if I eliminate the smaller box, will it hurt the efficiancy of the system? ...not that 3 miles of porting helps or anything. The hole idea is to get as much beefyness out of this sub as humanly possible. Size is of no matter within reason. Thanks for all the help. I have not built a box in almost 10 years and kind of excited to do it again.

Brett

[annunaki]

With that driver, I would do a 1.25 ft^3 enclosure tuned to 27hz with a single 4" port (flared on both ends) 33.61" long. One could also do a 1.25 ft^3 enclosure with a 1.5" x 8-1/3" square vent (rounded on both ends) 33.61" long. The curve is not quite as linear (inaudibly) as the other enclosure (.85 ft^3), but will extend you deeper. Not to mention it would be much easier to construct. Either configuration (round or square port) would give you an anechoic F3 of 24.5hz. In room, this could be pushed down to 20hz or below!

[bmccord]

So you are saying a 1.25 ft^3 enclosue with a 4" dia port that is 34" long in a similar configuration would be better? I am not a fan of square ports. Not sure why, just had bad luck with them. Thanks.

Brett

[bmccord]

Does anyone know what the proper way to set up a slot vent? If I can make one that doesn't make any strange noises, I will just go with that...

[annunaki]

The biggest things to remember with slot vents is to make sure that there is an adequate opening, and round your edges. The more bends in the slot vent the more chance for noise as well. The advantage to slots vents is they brace the enclosure as well as vent it.

If you are afraid of using slot vents, simply go with the 4" port or dual 3" ports. You shouldn't have any noise issues using and aeroport. If you wanted you could still use two 3" ports, however, they would be 39.09" long. Doing two 3" ports figuring their displacement and the woofer's (.06?) you will need to make a 1.64 ft^3 enclosure, gross.

[annunaki]

I suggested a 4" port before because the length would be a little less, though you would give up some port area to dual 3" ports. Using an aeroport surely would help to alleviate any noise issues.

[MacManNM]

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.

[bmccord]

Indeed. The box the sub is currently in has a 4" port and watching War of the Worlds was rather dissapointing due to all the port noise. It was pretty rediculous at -15 dB levels. so....thats why I was thinking 2 - 3" ports. I did not know that you add the port volume into the box volume. i figured since it was hollow, it was part of the acoustic volume. I am taking the driver volume into consideration though and the amp doesn't matter due to it being in the secondary enclosure.

Thanks all.

Brett

[bmccord]

Also, what is aeroport?

[MacManNM]

Well If I were you, I wouldn't build a vented enclosure at all for that unit. I would build a sealed enclosure and use a linkiwitz transform circuit. This will increase the power requirements for the unit but will give you a nice response down to 20hz. If you really want a vented enclosure you are going to need at least 3-3" ports to keep the noise down. If you build ~4 ft^3 box and have 3-35" ports the response isn't too bad. But with room gain you might have some problems. the other thing you can do is decrease the port length to 22" and build a passive notch filter in the unit to flatten the response out.

[WmAx]

Well If I were you, I wouldn't build a vented enclosure at all for that unit. I would build a sealed enclosure and use a linkiwitz transform circuit. This will increase the power requirements for the unit but will give you a nice response down to 20hz. .

It should be noted for the original poster that a sealed box will substantially reduce the maximum output level at lower frequencies, and increase non-linear distortion, especially with use of a Linkwitz Transform circuit.

-Chris

[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...:confused: 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:D

[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:p 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:D


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