on Sale - $55/pr (drivers & XO)

[XtremeRevolution]

Re: on Sale - $55/pr (drivers & XO)

XtremeRevolution,

Looking good! how thick is that mdf and how tall are your cabinets?

JustinL42

MDF is 3/4". Cabinets are 28" tall. I will be building stands for these as well. Right now #1 priority is getting the cabinets themselves done since I only have till the 23rd of the month to finish them.

Oh, and front baffles are removable.

[JustinL42]

Re: on Sale - $55/pr (drivers & XO)

Couple daylight pics

[MLS]

Re: on Sale - $55/pr (drivers & XO)

Looking good Justin.

I just tried priming mine and it turned into a disaster. The primer spit globs of paint. I am also seeing dry spots like I did not seal the mdf well enough. I put three coats of 50/50 on them.

I think I am going to have to end up with a hammered finish because of these issues.

MLS

[JustinL42]

Re: on Sale - $55/pr (drivers & XO)

I only used one coat of 50/50 titebond on mine but my primer experience was less than ideal also. I used a valspar rattle can primer and waited forever for it to dry properly and it was still semi tacky and soft. Can said dries fast but had literally no other info on dry time recoat or sanding time. Ended up sanding by hand with extremely light pressure and then sprayed the valspar flat black which dried much faster. The few visible imperfections I can see are due to the primer being a pain to deal with.

JustinL42

[MLS]

Re: on Sale - $55/pr (drivers & XO)

Justin, What size is your port. Mine is 1 1/2".

[JustinL42]

Re: on Sale - $55/pr (drivers & XO)

It is 2" PVC by 8" long

Actually I take that back I followed Chris formers plan exactly so it is 1.5" diameter. Will remeasure to be sure. Was posting fromwork earlier and going from memory. I went to three office supply stores who all listed having 1.5 diameter packing tube and none had it in stock so I ended up at lowes with the PVC. Just checked it is 1.5id. The roundover on the port makes it look larger than it is.

[XtremeRevolution]

Re: on Sale - $55/pr (drivers & XO)

Had a bit of a problem today. My internal depth is 8" since I'm using the floorstanding mini tower design. I picked up this port:

http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=268-348

Apparently, the distance is measured not at the end of the flare, but at the point where the tube is 2". This causes the port to be an additional 1" long. A bit of a problem when I only have 8.75" to work with and I need 8.09 inches of port with flares included.

I decided that the only way to make it work would be to have a bottom firing port. I'm going to build stands into the cabinet that will allow the entire under side to be open as well.

[JustinL42]

Re: on Sale - $55/pr (drivers & XO)

I was going to say the instructions state the central tube can be cut to any length, but you are stating that tube needs to be the full port length which does make sense as it is the one that is actually the port diameter. Those flares are huge! hopefully my small roundover doesn't throw mine off as I didn't account for it in my port length. It seems pretty miner compared to those flares.

JustinL42

[Chris Roemer]

Re: on Sale - $55/pr (drivers & XO)

Had a bit of a problem today. My internal depth is 8" since I'm using the floorstanding mini tower design. I picked up this port:

http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=268-348

Apparently, the distance is measured not at the end of the flare, but at the point where the tube is 2". This causes the port to be an additional 1" long. A bit of a problem when I only have 8.75" to work with and I need 8.09 inches of port with flares included.

I decided that the only way to make it work would be to have a bottom firing port. I'm going to build stands into the cabinet that will allow the entire under side to be open as well.

Hey X,

You CAN bottom vent, but if you can shorten the PPort by 1" (to 7") and get at least 1" of internal clearance between the inside wall and the end of the flair, you'll be OK.

Chris

[XtremeRevolution]

Re: on Sale - $55/pr (drivers & XO)

I have a concern here. I plugged these numbers into WinISD and a .55 cubic foot box tuned to 39 hz requires a 2"D x 8.46" port length. Any idea why that is so? A 7.09" port length tunes to 42hz...

Hey X,

You CAN bottom vent, but if you can shorten the PPort by 1" (to 7") and get at least 1" of internal clearance between the inside wall and the end of the flair, you'll be OK.

Chris

Please see the above quote. I was told at first that the recommended port length was 7.09. Even at that port length, my clearance is insufficient. that, and I've already cut the hole as I realized these will be placed quite close to the wall. That, and the flares take up 1" on their own. so at minimum I'd have an 8" total port length, which would bring me 0.75" away from the front baffle. That's cutting it way too close for me.

What then is the ideal port length for these?

[fastbike1]

Re: on Sale - $55/pr (drivers & XO)

Short answer: there is no "ideal" port length.

The design port length depends on the response you're trying to achieve. Also requires consideration of the response curve (i.e. flat or with a hump), driver excursion, and port velocity.

You can bend the port if your required length is too long for the box. Or you can shorten the port and live with (potentially) higher tuning. This may bring the port velocity too high. Then you can make the port larger in diameter, which raises the tuning, and around you go.

Please see the above quote. I was told at first that the recommended port length was 7.09. Even at that port length, my clearance is insufficient. that, and I've already cut the hole as I realized these will be placed quite close to the wall. That, and the flares take up 1" on their own. so at minimum I'd have an 8" total port length, which would bring me 0.75" away from the front baffle. That's cutting it way too close for me.

What then is the ideal port length for these?

[XtremeRevolution]

Re: on Sale - $55/pr (drivers & XO)

Short answer: there is no "ideal" port length.

The design port length depends on the response you're trying to achieve. Also requires consideration of the response curve (i.e. flat or with a hump), driver excursion, and port velocity.

You can bend the port if your required length is too long for the box. Or you can shorten the port and live with (potentially) higher tuning. This may bring the port velocity too high. Then you can make the port larger in diameter, which raises the tuning, and around you go.

This I understand perfectly. I've built numerous subwoofer boxes before and played with WinISD till I was blue in the face, but I was more referring to what is recommended as the ideal port length for this specific application; the NTN cabinets. I don't want to tune them too low or too high, and I believe the 39hz tune was the ideal, but when I run those numbers I come up with a 8.46" port, while the recommended port size on page 2 that Chris came up with was 7.09 for that same frequency. I'm just trying to figure out which one to use.

[ericJ]

Re: on Sale - $55/pr (drivers & XO)

I picked up a 2 foot scrap piece of 1.5" PVC from Home Depot for 50 cents. After measuring, the ID is actually like 1 5/8".

For those using PVC on the tradional NT design; any comments? Is this normal?

[Drew_V]

Re: on Sale - $55/pr (drivers & XO)

I got the same deal at HD (did you buy yours based on my recommendation or was it just a coincidence?). I'm guessing the difference in diameter isn't critical, especially for the fidelity of these little speakers.

As for the port length, Chris calls for a total port length of 8" in the original plans, which for a wall thickness of 3/4" makes it a 7.25" long tube. A 1/4" here or there won't make a difference, really, so whoever is using a 7" tube should be fine.

[XtremeRevolution]

Re: on Sale - $55/pr (drivers & XO)

I got the same deal at HD (did you buy yours based on my recommendation or was it just a coincidence?). I'm guessing the difference in diameter isn't critical, especially for the fidelity of these little speakers.

As for the port length, Chris calls for a total port length of 8" in the original plans, which for a wall thickness of 3/4" makes it a 7.25" long tube. A 1/4" here or there won't make a difference, really, so whoever is using a 7" tube should be fine.

Thanks for clarifying that. That makes sense now. Alright, I'll cut them to 8" length.