AK Design Collaborative - Insignia-Class Economy Speakers (a.k.a Indignia)
- Thread starter Zilch
- Start date
greenmark59
Can ya' hear that?
I'm a newbie DIY speaker builder and want to use some Baby Advent II speaker cabinets that I have laying around. They have about a 0.40 cubic ft volume and I think they would work reasonably well for building some Indignas. My question is because they are only about 6 inches deep, could I put a "curved" port tube made of one section of 5 inch PVC pipe and another section of 6 inch pipe connected with a right angle elbow (total of 11 inches as recommended). I would have the port vent come out the front and the inside tube would be near the woofer.
Would this be a decent port design or should I just go closed cabinet?
Would this be a decent port design or should I just go closed cabinet?
jackgiff
Well-Known Member
Film positives are done.
Rick finally solved the problem of making film positives (or negatives) by scanning my artworks and entering them into his computer. The computer can then generate the films by whatever process it uses. I have film positives at home, and will etch another board for Zilch, so he has a pair. The films look very nice, with the emulsion on the down side, so exposing sensitized pc boards will be easier than using the artworks, as I usually do.
I have ordered some supplies from a company which uses spray on sensitizer and negative image exposure. That will proably be better than using the presensitized boards from Parts Express, cause if you screw up the developing, you simply clean the board and start over. There is no way to start over with a presensitized board, other than using this negative process. And raw boards are much cheaper than the presensitized ones.
Another possibility is buying boards from someone like the China PC house that advertises on AK. Their prices for finished boards in lots of 30 or so is pretty reasonable. If someone ordered 30 boards and distributed them in pairs, it would cost about the same for a pair as what it would cost to buy supplies and etch your own. Plus, they would have solder resist on the back, and silk screen parts location info on the front. We need Gerber files, or equivalents, to order from them, and I have a CAD PC layout program which will take a few days to learn. If their is any interest in buying PC boards rather than etching them yourself, please let us know.
Rick finally solved the problem of making film positives (or negatives) by scanning my artworks and entering them into his computer. The computer can then generate the films by whatever process it uses. I have film positives at home, and will etch another board for Zilch, so he has a pair. The films look very nice, with the emulsion on the down side, so exposing sensitized pc boards will be easier than using the artworks, as I usually do.
I have ordered some supplies from a company which uses spray on sensitizer and negative image exposure. That will proably be better than using the presensitized boards from Parts Express, cause if you screw up the developing, you simply clean the board and start over. There is no way to start over with a presensitized board, other than using this negative process. And raw boards are much cheaper than the presensitized ones.
Another possibility is buying boards from someone like the China PC house that advertises on AK. Their prices for finished boards in lots of 30 or so is pretty reasonable. If someone ordered 30 boards and distributed them in pairs, it would cost about the same for a pair as what it would cost to buy supplies and etch your own. Plus, they would have solder resist on the back, and silk screen parts location info on the front. We need Gerber files, or equivalents, to order from them, and I have a CAD PC layout program which will take a few days to learn. If their is any interest in buying PC boards rather than etching them yourself, please let us know.
Great job on the boards Jack. Just beautiful work. I was hanging out at the Zilchlab yesterday while he was soldering it up and it went together with ease and sounded excellent right 'out of the box'. I didn't hear any audible differences from Zilch's adhoc wirenutted crossover and your more elegant circuit board solution.
Way to go!:thmbsp:
Way to go!:thmbsp:
You can do a bent vent. PE has kits for it, although I don't know if they have them in 1.5". And per the design, the port length is 8". If you want to try something else, let us know how it works out!
Ray
Closed-box works fine, also. The power-handling is less, and the bass somewhat "muted."
I recommend putting in the port so that you have both options available according to taste and room positioning. If you use Indignias with boundary reinforcement (against the wall,) closed-box may be preferred. [Or not.
]
As you can see from my final curves, they're ~2 dB "brighter" above 10 kHz on axis, so you can tune the VHF to your pleasure by the amount of toe-in you give them, as well. :yes:
I recommend putting in the port so that you have both options available according to taste and room positioning. If you use Indignias with boundary reinforcement (against the wall,) closed-box may be preferred. [Or not.
]As you can see from my final curves, they're ~2 dB "brighter" above 10 kHz on axis, so you can tune the VHF to your pleasure by the amount of toe-in you give them, as well. :yes:
Cool beans, Beans!
There are as many ways to build Indignia crossovers as there are clever AKers to make them happen.... :thmbsp:
beans
Got arth-a-ritis
Pix promised earlier:
My first crossover. The one I made last night is much better.
Here's the "test" unit. The front baffle needs to be redone which is why it's not attached.
Hot damn! Makes ya wanna pick up a guitar!
Here's one for all you Bose bashers... look at what the Indignia is replacing!
My first crossover. The one I made last night is much better.
Here's the "test" unit. The front baffle needs to be redone which is why it's not attached.
Hot damn! Makes ya wanna pick up a guitar!
Here's one for all you Bose bashers... look at what the Indignia is replacing!
On some speakers I prefer the port open, on others I prefer it stuffed with a rag (I keep forgetting to buy "Zilchplugz" when I'm at Home Depot). As Zilch said above, that's the beauty of ports, you can listen to them either way.
Nice work, Beans.
One more thing. You may want to consider a horizontal brace inside the cabinet. Just glue a 3" or so horizontal piece of the same material used on the cabinet walls. I used "Gorilla Glue" to attach mine and it expanded to make a really tight fit. Screws and dowels would probably have been better though.
Based on my simple "knuckle rap" test (knocking on the cabinet at various locations), the brace makes the cabinet and much stiffer and hopefully more immune to resonance. I wrapped the brace with fabric to reduce its reflectivity from the drivers nearby.
beans
Got arth-a-ritis
I'll do it! Anyway, I need something to take up more space to get it closer to .4 cuFt. That's also why the terminal pad in back is so big. In fact the edge of that thing gets very close to the end of the duct. Does that matter?
Nice woofer.
Define "very close". In general you want about a port diameter between the end of the port and a wall. You can get by with less though.
Ray
beans
Got arth-a-ritis
Ray, I think it's OK. There's at least 1 1/2" clearance to the back panel. What I'm wondering is whether or not the top edge of the other piece I glued in to mount the terminals to will have any effect if it reaches to within a diameter of the duct, but I think you've answered it. I haven't measured to see just how close it is but i will this evening to make sure.
This is why I was calling it a "test unit"... the dimensions I used came from the dimensions of the front baffle in Zilch's drawing and making the cab deep enough to allow at least 1 1/2" from the padding along the back wall and the end of the duct. But compared to .4 cuFt it came out about 100 cuIn too big so I started to shrink the width & height to bring it down. Then thought I'd just tweak it by sticking pieces of MDF inside to reduce the volume... hence the oversize rear apron, but even so it's over .4 cuFt.
As soon as I get the padding and the brace installed I'll begin tinkering with it. Tell ya what though... it sounds pretty nice right now with only a towel in there!
ONE MORE QUESTION: That reminds me, how much effect does the padding have on the volume measurements we're making?
Just one, huh?
Depends on what you're doing with it. If you're just lining the walls like Z and I did then it has very minimal effect on the volume. If you're actually putting stuffing into the box then it will add some apparent volume. Usually for ported boxes I just line the walls to keep midrange reflections down.
That crossbrace will take up some of your volume too. Also, if you do a crossbrace the put it under tension. Meaning, make it tight enough that you have to wedge it in. That will push up the resonance of the wall more than just putting something in that just fits. Or if you really want to take up some volume put side panels inside to stiffen the side walls (that's a lot of 'sides', isn't it?). That might be too much volume though.
Ray
beans
Got arth-a-ritis
Just one, huh?
Good point, but I got to thinking if I build 2 test/tinker speakers and decide to start over with the cabs, then I'd want to start over with the both of them. But now I'm pretty convinced we're at least on the right track and it's time to slap together the other one. Need to sit the boy down and make a plan... he's the one who'll paint and "decorate".
Putting an elbow on the end of the duct will allow you to shorten it and reduce the cabinet depth.
Aiming it diagonally upward behind the tweeter will circumvent many of these issues.... :yes:
beans
Got arth-a-ritis
NO, I just assumed that was part of it. Thanks for asking... I'll re-run my figures tonight.
I'm doing everything in cubic inches to make it easier. .4 cuFt = 692 cuIn
Well, hang on now, we designed around a fixed gross internal volume of 0.4 cuft, not net of driver and/or duct displacement.
I have no clue what the net volume is, but it doesn't matter, since we're all using the same drivers and duct.
Fact is, there is some leeway in cabinet volume; it does not have to be precise. But the duct volume is significant, and would likely exceed that limit.... :yes:
I have no clue what the net volume is, but it doesn't matter, since we're all using the same drivers and duct.
Fact is, there is some leeway in cabinet volume; it does not have to be precise. But the duct volume is significant, and would likely exceed that limit.... :yes:
beans
Got arth-a-ritis
I think my cab is 9 1/2" deep on the inside. That gives it sort of an odd shape, but it sounds good!.:yes: Tonight I want to tinker with the volume by just dropping in pieces of MDF to reduce the volume just to see how it affects the bass.
Good point, Z. My bad. We've been working with a known enclosure volume and leaving the woofer and port out of the equation because we're all using the same ones.
I tend to leave that out because BassBox6 (which I usually use for the first step) takes it into account so I don't have to.
Ray
I tend to leave that out because BassBox6 (which I usually use for the first step) takes it into account so I don't have to.
Ray