Hi all-
First post in this forum, I usually post in the Tube Amp forum.
Now I'm working on the parts that my tube amp plugs into
I'm just finishing a pair of the BD pipes, found here:
BD pipes
My question is in regards to the port diameter and material.
Is the 68mm the inside diameter of the port tube?
If anyone has built these, I'd like to know what they used for material for the port? I've used PVC tubing before on other speakers, but I can only get 2" (50.8mm) ID PVC tubing. If I was to use this, would the length get shorter? I can't find anywhere in the article what the port is tuned for. From using a few port calculators on the web, it looks like the enclosure is tuned for around 48Hz.
Any suggestions would be appreciated from anyone who has built a pair of these speakers.
Thanks
Glenn
First post in this forum, I usually post in the Tube Amp forum.
Now I'm working on the parts that my tube amp plugs into
I'm just finishing a pair of the BD pipes, found here:
BD pipes
My question is in regards to the port diameter and material.
Is the 68mm the inside diameter of the port tube?
If anyone has built these, I'd like to know what they used for material for the port? I've used PVC tubing before on other speakers, but I can only get 2" (50.8mm) ID PVC tubing. If I was to use this, would the length get shorter? I can't find anywhere in the article what the port is tuned for. From using a few port calculators on the web, it looks like the enclosure is tuned for around 48Hz.
Any suggestions would be appreciated from anyone who has built a pair of these speakers.
Thanks
Glenn
Hi Giovanni, thanks for the reply.
Yes, I assumed the ID to be 2.5"also, I was more interested in what people were using for the actual tube material. PVC tubing comes in even sizes around here. I know 2.5" is manufactured, it's just not readily available.
I actually wound up using 2" ID, and adjusted the length accordingly. I just hope the port isn't too noisy as the velocity of the air moving through it will be higher. I did epoxy the tube to the inside of the cabinet and routed a nice radius to smooth the airflow. We'll see how it works.
I'm planning on using a Tang Band W4-616SA driver as a start.
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=264-818
I really can't afford four Fostex drivers right now, so we'll see how these work.
How do you like these cabinets? What drivers are you using?
I'm looking for more efficient speakers for my SE KT88 amp, that's what started me on this project.
Glenn
Yes, I assumed the ID to be 2.5"also, I was more interested in what people were using for the actual tube material. PVC tubing comes in even sizes around here. I know 2.5" is manufactured, it's just not readily available.
I actually wound up using 2" ID, and adjusted the length accordingly. I just hope the port isn't too noisy as the velocity of the air moving through it will be higher. I did epoxy the tube to the inside of the cabinet and routed a nice radius to smooth the airflow. We'll see how it works.
I'm planning on using a Tang Band W4-616SA driver as a start.
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=264-818
I really can't afford four Fostex drivers right now, so we'll see how these work.
How do you like these cabinets? What drivers are you using?
I'm looking for more efficient speakers for my SE KT88 amp, that's what started me on this project.
Glenn
ABS pipe might be available in more size choices. I don't imagine 2" diam will cause port noise with these small drivers.
Those TB drivers params seems close enough. IMO, they look better than the fostex drivers. Trying a 4" woofer on the rear might be fun.
I used the RS 40-1197. This was my first FR speaker and I was immediately impressed. The box tuning is low, so you can't get much SPL, but they sound nice at low volume.
Post some pictures when you are done.
Cheers
Those TB drivers params seems close enough. IMO, they look better than the fostex drivers. Trying a 4" woofer on the rear might be fun.
I used the RS 40-1197. This was my first FR speaker and I was immediately impressed. The box tuning is low, so you can't get much SPL, but they sound nice at low volume.
Post some pictures when you are done.
Cheers
After I posted, I ran across a web site that gives some calculations for max velocity to avoid port noise. I ran the numbers, and as you said, the velocity was well below the recommended max. value to avoid port noise.
I did wind-up using the 2"ID PVC with the length suggested by the software. http://www.linearteam.dk/default.aspx?pageid=ventcalculator
I'm actually thinking of upgrading at some point to the Tang Band with the coaxial tweeter for the front, and a woofer as you mentioned for the back.
Tang Band coaxial 4"
Tang Band 4" woofer
I've got to remember to take some pictures before I glue the sides on
Glenn
I did wind-up using the 2"ID PVC with the length suggested by the software. http://www.linearteam.dk/default.aspx?pageid=ventcalculator
I'm actually thinking of upgrading at some point to the Tang Band with the coaxial tweeter for the front, and a woofer as you mentioned for the back.
Tang Band coaxial 4"
Tang Band 4" woofer
I've got to remember to take some pictures before I glue the sides on
Glenn
Yeah, that's what I figured. My real issue was finding something the right diameter locally. I saw that cardboard shipping tubes were available in 2.5"ID, but everyone around here (Staples, etc.) only carried even sizes, 2", 3", etc.
I think the 2" PVC I used will work fine with the length re-calculated accordingly.
I'll keep everyone posted.
Thanks
I think the 2" PVC I used will work fine with the length re-calculated accordingly.
I'll keep everyone posted.
Thanks
FYI you can make a square tube with the same cross sectional area (CSA) and length from scrap for oddball sizes or just use Ron E's math to scale it up to the next readily available diameter:
GM
square inch is a measurement of area
a circle with an area of 25 square inches is :
Area = pi*diameter^2/4
rearrange:
sqrt(4*Area/pi) = diameter
For your area of 25 square inches, the diameter is 5.64 inches, or 14.3 cm.
It is hard to make a round port a specific size, so you can scale your length, based on available port diameters.
L1/L2 = A1/A2, where L1, A1 are the original length and area, and L2,A2 are the new length and area...
rearranging again, and Realizing that area is proportional to diameter squared:
L2 = L1*(D2^2/D1^2), where D2 is new diameter and D1 is the original diameter.
You input the diameter of the ports you can get, and from that you can get the new length.....
GM
square inch is a measurement of area
a circle with an area of 25 square inches is :
Area = pi*diameter^2/4
rearrange:
sqrt(4*Area/pi) = diameter
For your area of 25 square inches, the diameter is 5.64 inches, or 14.3 cm.
It is hard to make a round port a specific size, so you can scale your length, based on available port diameters.
L1/L2 = A1/A2, where L1, A1 are the original length and area, and L2,A2 are the new length and area...
rearranging again, and Realizing that area is proportional to diameter squared:
L2 = L1*(D2^2/D1^2), where D2 is new diameter and D1 is the original diameter.
You input the diameter of the ports you can get, and from that you can get the new length.....
Okay, now we're talking my language!
Using the formula L2 = L1*(D2^2/D1^2), and the following port dimensions:
L1=131mm (old port length)
D1=68mm (old port diameter)
D2=50.8mm (2") (new port diameter)
I get a new port length of 73.11mm (2.878").
That's a good check, because using the online port calculators I got a new port length of 2.86", pretty close.
Thanks very much for the ratio formula!
Glenn
Using the formula L2 = L1*(D2^2/D1^2), and the following port dimensions:
L1=131mm (old port length)
D1=68mm (old port diameter)
D2=50.8mm (2") (new port diameter)
I get a new port length of 73.11mm (2.878").
That's a good check, because using the online port calculators I got a new port length of 2.86", pretty close.
Thanks very much for the ratio formula!
Glenn
porkchop61 said:
I thought you couldn't afford the FE103E!
BTW - Peter Millet employed a woofer on the rear.
http://www.pmillett.com/tqwp.htm
You know, for some reason I thought the Fostex drivers were really expensive. I see that Madisound has them for $38.20 ea. , that's a good deal! Maybe I was thinking of the FE108E Sigma drivers before.
Just finished gluing the sides on each cabinet last night after installing the stuffing. Now I just have to finish these things! I built these out of Birch plywood, and I'm going to paint them. What do people use to seal the end grain of the plywood? Is it necessary, or are two coats of primer enough to keep the topcoat from soaking in? What do people use for filling finish nail holes and any imperfections? I was thinking joint compound would probably be okay, it sands really nice
Thanks for all the help!
Glenn
Just finished gluing the sides on each cabinet last night after installing the stuffing. Now I just have to finish these things! I built these out of Birch plywood, and I'm going to paint them. What do people use to seal the end grain of the plywood? Is it necessary, or are two coats of primer enough to keep the topcoat from soaking in? What do people use for filling finish nail holes and any imperfections? I was thinking joint compound would probably be okay, it sands really nice
Thanks for all the help!
Glenn
Stainable wood filler. I stain first, then apply the stained-to-match filler, seal, smooth, finish with at least two coats. If you fill first it will be obvious where you applied it. For exposed edges, covering them with the thin, pre-cut veneer sold for this purpose is the easy way to 'fill' them (my preference).
If by 'paint' you mean an opaque color, then seal, apply plain wood filler, smooth, paint with at least two coats.
My experience with using joint compound on any wood short of petrified hasn't been a good one long term, so can't recommend it.
GM
If by 'paint' you mean an opaque color, then seal, apply plain wood filler, smooth, paint with at least two coats.
My experience with using joint compound on any wood short of petrified hasn't been a good one long term, so can't recommend it.
GM
Thanks GM.
Yes, I mean a solid enamel colored spray paint.
When you say "seal", do you mean primer, or some sort of sanding sealer?
I was going to do two coats of enamel spray primer, and then two coats of a gloss enamel topcoat.
Good to know about the joint compound, I'll try the wood filler.
Thanks!
Yes, I mean a solid enamel colored spray paint.
When you say "seal", do you mean primer, or some sort of sanding sealer?
I was going to do two coats of enamel spray primer, and then two coats of a gloss enamel topcoat.
Good to know about the joint compound, I'll try the wood filler.
Thanks!
I have never gotten a truly good paint job out of rattle cans. Rattle cans are good for lawn furniture and picture frames, but you can always see the over-spray and lap lines on large flat pieces.
If you are able to accept light orange peeling, try this:
Apply as many coats of an oil based primer, such as Zinsser's or Kilz, as you need with a foam roller. Once it is sanded down to at least 220 grit (which can be a b....., you might want to wet sand), apply oil based enamel with a foam roller. I think that the results are better than rattle cans.
Bob
If you are able to accept light orange peeling, try this:
Apply as many coats of an oil based primer, such as Zinsser's or Kilz, as you need with a foam roller. Once it is sanded down to at least 220 grit (which can be a b....., you might want to wet sand), apply oil based enamel with a foam roller. I think that the results are better than rattle cans.
Bob
FWIW I've gotten excellent results with spray cans on large appliances, cycles, surprisingly even on a tan finished '36 FORD pick-up work truck, but in each case it was with Krylon brand and we inadvertently learned from painting the truck that you have to heat it up a bit (Atlanta sun in July) to ensure good run-out. Their epoxy is especially good, or at least was the last time I used it to refinish a ceiling fan plus blades in gloss white and change the colors on the dishwasher panels to black.
With all the recent EPA changes though, it may just be a 'pipe dream' now.
Hmm, I was trained to use steel wool to 'sand' oil based coatings and it has served me well, but out of curiosity I did a bit of Googling and it seems that sanding sponges is now the preferred choice.
GM
With all the recent EPA changes though, it may just be a 'pipe dream' now.
Hmm, I was trained to use steel wool to 'sand' oil based coatings and it has served me well, but out of curiosity I did a bit of Googling and it seems that sanding sponges is now the preferred choice.
GM
Thanks all for the suggestions!
My other hobby is antique radios, so I'm more familiar with using lacquer. I really didn't want to do these speakers in lacquer, although the thought crossed my mind about how lovely a piano black finish would be. It's just too time consuming to put on 10-12 coats of lacquer with a rub out in between coats
I'm going to see how enamel works out.
Glenn
My other hobby is antique radios, so I'm more familiar with using lacquer. I really didn't want to do these speakers in lacquer, although the thought crossed my mind about how lovely a piano black finish would be. It's just too time consuming to put on 10-12 coats of lacquer with a rub out in between coats
I'm going to see how enamel works out.
Glenn
Okay, finished these speakers last weekend.
Here's some pictures as promised (sorry no thumbnails)
Glenn's BD pipes
Just ignore the Kenwood drivers that are in there now. I don't have the Fostex 103's yet. The Kenwoods are full range drivers from some home surround speakers. They don't actually sound too bad, but I'm sure the Fostex will be a huge improvement. I'm sure the Kenwoods are super inefficient The bookshelf speakers are JBL's that I was using (two-way w/8" drivers).
They are driven with my stereo build of Mikael's SE KT88 over on the tubes area of this forum. Those are KT66's running at the moment
Note the Morgan Jones book on the right of the amp
Glenn
Here's some pictures as promised (sorry no thumbnails)
Glenn's BD pipes
Just ignore the Kenwood drivers that are in there now. I don't have the Fostex 103's yet. The Kenwoods are full range drivers from some home surround speakers. They don't actually sound too bad, but I'm sure the Fostex will be a huge improvement. I'm sure the Kenwoods are super inefficient
The bookshelf speakers are JBL's that I was using (two-way w/8" drivers).They are driven with my stereo build of Mikael's SE KT88 over on the tubes area of this forum. Those are KT66's running at the moment
Note the Morgan Jones book on the right of the amp
Glenn
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