So I had been looking for a pair of Altec 420's to work into an open baffle design, but I got a great deal on the Altec (for Heathkit) 416 8A's that are a match for my Heathkit 811 horns, so they're on the way here now. So the OB idea is on the back burner for now.
In looking around for what other folks have done, I've been seeing some really nice things, and some really BIG things, A lot of folks sing praises of the Onken type enclosures, but man are they big and kind of ugly. I've been kicking around ways to make them less visually offensive to me, and I just can't do it. The size is prohibitive for me right now as well.
Altec published some port size curves on an enclosure volume calculator, which I've been going by.
I've come up with an enclosure that is not so large and boxy (still boxy, but a taller, slightly narrower design. My total internal volume is about 5.2 cubic ft and the port size is 25 square inches. The front baffle will be 1.25" thick and I may do that for the sides as well, but I'm curious if I should put an internal baffle below the 416 and above the port to sort of separate the upper chamber from the port area a bit as is done in the Onken design. Would this be beneficial? I know I can always cut a couple out and try them both in and out and see - probably what I'll end up doing...
A few renders to get the idea.
(yes, I know the cone isn't right for the 416 driver, but I wasn't patient enough to model a pleated surround)
In looking around for what other folks have done, I've been seeing some really nice things, and some really BIG things, A lot of folks sing praises of the Onken type enclosures, but man are they big and kind of ugly. I've been kicking around ways to make them less visually offensive to me, and I just can't do it. The size is prohibitive for me right now as well.
Altec published some port size curves on an enclosure volume calculator, which I've been going by.
I've come up with an enclosure that is not so large and boxy (still boxy, but a taller, slightly narrower design. My total internal volume is about 5.2 cubic ft and the port size is 25 square inches. The front baffle will be 1.25" thick and I may do that for the sides as well, but I'm curious if I should put an internal baffle below the 416 and above the port to sort of separate the upper chamber from the port area a bit as is done in the Onken design. Would this be beneficial? I know I can always cut a couple out and try them both in and out and see - probably what I'll end up doing...
A few renders to get the idea.
(yes, I know the cone isn't right for the 416 driver, but I wasn't patient enough to model a pleated surround)
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Looks good. Move the 416 to the top to help integrate into the horn, otherwise listening distance under 12' and you can hear the seperation. Put some port length on it to allow for tuning. The back unscrews? I used 4x 5/16" threaded rods front to back with wing nuts to make for quick adjustments and extra bracing. It doesn't pertrude out the front as I thread into a metal bracket that is screwed to the backside of the front baffle. Use wool or downe as filler. An old wool blanket or downe pillow behind the 416 is your friend. Better than polyfill. Try to find grannite slabs for under your box if going on a hard floor. That mod litterally doubled my bass.
Hmm... the renders all look squashed now.
I thought about moving the 416 toward the top a bit more. Makes sense. Yes, the rear will bolt on and have some sort of gasket material and perhaps a brace to the front like I've seen in some of the other Altec cabinets. I've seen the hint about old wool blankets before as well, but unsure about how to implement that... double them up and staple to the inside? Thanks!
I thought about moving the 416 toward the top a bit more. Makes sense. Yes, the rear will bolt on and have some sort of gasket material and perhaps a brace to the front like I've seen in some of the other Altec cabinets. I've seen the hint about old wool blankets before as well, but unsure about how to implement that... double them up and staple to the inside? Thanks!
The Altec port graph assumes a 3/4" depth, adding length will tune lower than the nominal value.
As you can see, smaller ports tune lower, but small ports will be "blown out" with little power.
Using (large) ducted ports will reduce port velocity, and also reduce the amount of out of phase mid range output from the port, probably the purpose of the internal baffle above the port in the Onken design.
I wouldn't try to mimic the onken design. The slot ports being varying distances from the driver cause phase ripple issues. I also wouldn't do a port with no length either. A large single flared port at the bottom will be the best at getting bass gain, and also be the best at reducing midrange getting out of the box acting as a low pass filter. The only benefit of a large onken is efficiency in low freq. but if you're bi amping, its not a big deal. And even better if your DSP'ing the low freq. if youcan do that, then tune the port very low, like 30hz, then dsp it back up to be flat extension down to that. Takes some power to do it properly, but worth it.
Thanks - I hadn't thought about the change in the baffle thickness effecting anything other than helping stiffness. Will the extra 3/8" make a huge difference in tuning? Should I make the port larger to compensate (if I'm looking at that correctly)?
I've moved the driver up by ~2 inches - that's all I have before running into the internal brace for mounting/support of the front baffle. My listening chair is on the low side, so my ear height is probably around 30 or 32" and should fall between the 416 and the 811 - the horn will not be as high as it is in the first render set either. I'm going to play with this set up with the Eminence crossovers, but I think I'll look for either a set of original Altec crossovers to rebuild or build one from scratch. This is what I've got for now. The top is set down about a 1/16th and the front baffle is inset about a 16th for interest and for veneering ease. I think I'm going to go with a horizontal veneer as in the most recent set of renders below.
ARGH! This is frustrating! I'm still getting vertical compression of my images!
I like sappy veneers with a lot of contrast. I was thinking American red gum, but it's spendy for the effect I'm after. I've got my eye on some really nice black walnut that I think would look great on these - the cathedral, pointed, more sappy side wrapping around the outside with the cathedrals pointed toward the back; sap decreasing across the front with the inside of the pair being the darker, less sappy darker heartwood.
I've moved the driver up by ~2 inches - that's all I have before running into the internal brace for mounting/support of the front baffle. My listening chair is on the low side, so my ear height is probably around 30 or 32" and should fall between the 416 and the 811 - the horn will not be as high as it is in the first render set either. I'm going to play with this set up with the Eminence crossovers, but I think I'll look for either a set of original Altec crossovers to rebuild or build one from scratch. This is what I've got for now. The top is set down about a 1/16th and the front baffle is inset about a 16th for interest and for veneering ease. I think I'm going to go with a horizontal veneer as in the most recent set of renders below.
ARGH! This is frustrating! I'm still getting vertical compression of my images!
I like sappy veneers with a lot of contrast. I was thinking American red gum, but it's spendy for the effect I'm after. I've got my eye on some really nice black walnut that I think would look great on these - the cathedral, pointed, more sappy side wrapping around the outside with the cathedrals pointed toward the back; sap decreasing across the front with the inside of the pair being the darker, less sappy darker heartwood.
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Ah - this is perfect! Discussion and advice are exactly what I need!
Okay - so as long as my port is ~25 square inches in surface area - that's what I'm after... the shape of the port does seem to matter, though. So if I went with a single round port, the diameter and length would need to be such that the there is 25 square inches of port surface. Got it.
Well, it does seem that the plastic round ports will make tuning easier. How do you calculate the internal area on flared ports - or are these just listed by the manufacturer (or parts express)? Hadn't looked into this option - please excuse my ignorance!
WinISD free software is your friend. You punch in you speaker driver parameters (or if its a common driver like the 416-8a, you simply select it from a drop down list!) pick your box dimensions, and tuning freq, and it spits out port dimensions. It will even plot a SPL response graph. You can also set your port diameter and adjust the legth to see the effect on bass extension. The goal is to get as flat as possible curve to a realistic low freq. You will find out quickly that the 416 really likes a big box, when say compared to a JBL.
Thanks for the suggestion!
Alright - after playing with WinISD for awhile, using parameters for the 416 8B (the 8A is not available - lack of published data), using my volume of 5 cubic feet, I get a port diameter of 4" and a port length of ~2". Doing a little 2πrL gets me just over 25.1 square inches - so seems the Altec chart was right on.
The cabinet tuning looks best around 37Hz. The simulated response is flat out to around 70Hz and then starts a gradual falloff: 50Hz is at -3dB and 40 is at -7; 30 is down to -13dB. I can try putzing around with EQ in the crossover circuit to extend this a bit. But making the enclosures much bigger can't happen and adding a cubic foot doesn't do too much, so this looks like where it's at right now.
Alright - after playing with WinISD for awhile, using parameters for the 416 8B (the 8A is not available - lack of published data), using my volume of 5 cubic feet, I get a port diameter of 4" and a port length of ~2". Doing a little 2πrL gets me just over 25.1 square inches - so seems the Altec chart was right on.
The cabinet tuning looks best around 37Hz. The simulated response is flat out to around 70Hz and then starts a gradual falloff: 50Hz is at -3dB and 40 is at -7; 30 is down to -13dB. I can try putzing around with EQ in the crossover circuit to extend this a bit. But making the enclosures much bigger can't happen and adding a cubic foot doesn't do too much, so this looks like where it's at right now.
Cabinets Built!
Have had a chance to get these built over the winter break. Construction is butt-joints, glue, and pocket screws. As cabinet builders will tell you, this joinery is solid. My table saw is in storage right now, and I wanted to keep the joinery simple, yet build something rock solid. I think those goals have been accomplished. The front baffle is a 3/4" baltic birch panel that I glue laminated to another 1/2" baltic birch panel for a good solid 1 1/4" front panel. I did all of the cuts with a 7 1/4" circular saw (with a *good* thin kerf plywood blade), a compact router (with carbide spiral up bit), and a jigsaw. LOTS of clamps were used.
I find that I can get great results by using straight edge clamps and my old Black and Decker circular saw - I miss my cast iron table saw though... no room right now. The exploded view below shows how the carcass goes together. There is tremendous glue surface area, and all connections are clamped and pocket and/or face screwed.
The top, bottom, sides, and back panels are all 3/4" birch cabinet grade plywood. Took about 2 full sheets in addition to the front baffle material that I got from Rockler. The driver cutout and rear recess were done with a router and a circle cutting jig with a carbide spiral cutter. Very clean cuts that will only need minimal sanding when I get to finishing later this summer.
Cutting that many panels took awhile - so the build took about a week on and off. A couple of actual build photos.
They came out nice and square, and are very heavy and solid. I still need to install a few bracing pieces on the carcass sides, but am quite happy thus far.
Have had a chance to get these built over the winter break. Construction is butt-joints, glue, and pocket screws. As cabinet builders will tell you, this joinery is solid. My table saw is in storage right now, and I wanted to keep the joinery simple, yet build something rock solid. I think those goals have been accomplished. The front baffle is a 3/4" baltic birch panel that I glue laminated to another 1/2" baltic birch panel for a good solid 1 1/4" front panel. I did all of the cuts with a 7 1/4" circular saw (with a *good* thin kerf plywood blade), a compact router (with carbide spiral up bit), and a jigsaw. LOTS of clamps were used.
I find that I can get great results by using straight edge clamps and my old Black and Decker circular saw - I miss my cast iron table saw though... no room right now. The exploded view below shows how the carcass goes together. There is tremendous glue surface area, and all connections are clamped and pocket and/or face screwed.
The top, bottom, sides, and back panels are all 3/4" birch cabinet grade plywood. Took about 2 full sheets in addition to the front baffle material that I got from Rockler. The driver cutout and rear recess were done with a router and a circle cutting jig with a carbide spiral cutter. Very clean cuts that will only need minimal sanding when I get to finishing later this summer.
Cutting that many panels took awhile - so the build took about a week on and off. A couple of actual build photos.
They came out nice and square, and are very heavy and solid. I still need to install a few bracing pieces on the carcass sides, but am quite happy thus far.
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I've installed the crossovers and have the wiring temporarily connected with crimp-on connectors for now. I used a speaker terminal block for bi-amping with the top pair for the horn. The l-pad is on the rear panel.
My port tubes are coming in on Thursday, and so I've been giving them a listen with no internal damping and zero port length. WinISD tells me that with my 145 liter box, that corresponds to a tuning freq. of around 70 Hz - which gives a rather large bass hump at 80-100 Hz. Even with this, they sound quite good. But this brings me to some question for y'all.
1. What material do you all use for sealing the hole where the ports come through the cabinet front? I've thought about foam gasket material or 1" wide weatherstripping, but curious what everyone else uses.
2. I'm leaning toward 3/8" cotton felt for internal damping - on one side wall and one piece hung from the cabinet top draping down to just past the bottom of the driver. This stuff is what is used for padding under area rugs. It's natural, has a high recycled content, and seems like it would work quite well. Three questions here - 2) is it necessary to use this on both side walls? 3) has anyone hung material like this before? 4) has anyone used this material before?
3. Tuning the ports. I plan on tuning to around 30Hz - but I've heard that porous damping material actually increases effective internal volume. If that's the case, I may be able to tune to a lower frequency with the same tube length? I've seen a lot of folks saying 'tune by ear' - but, that would require cutting the port tubes and they're expensive! 5) Is there another way to do this?
Many thanks in advance!
EDIT: Oh, and here's one of the flitches I got for the veneer work. Really nice red gum - the grain will run just like the renders - vertical bookmatched up the front; horizontal across the sides with the horizontal wrapping around the front edge of the side panels. I have something sweet planned for the horn cradles!
My port tubes are coming in on Thursday, and so I've been giving them a listen with no internal damping and zero port length. WinISD tells me that with my 145 liter box, that corresponds to a tuning freq. of around 70 Hz - which gives a rather large bass hump at 80-100 Hz. Even with this, they sound quite good. But this brings me to some question for y'all.
1. What material do you all use for sealing the hole where the ports come through the cabinet front? I've thought about foam gasket material or 1" wide weatherstripping, but curious what everyone else uses.
2. I'm leaning toward 3/8" cotton felt for internal damping - on one side wall and one piece hung from the cabinet top draping down to just past the bottom of the driver. This stuff is what is used for padding under area rugs. It's natural, has a high recycled content, and seems like it would work quite well. Three questions here - 2) is it necessary to use this on both side walls? 3) has anyone hung material like this before? 4) has anyone used this material before?
3. Tuning the ports. I plan on tuning to around 30Hz - but I've heard that porous damping material actually increases effective internal volume. If that's the case, I may be able to tune to a lower frequency with the same tube length? I've seen a lot of folks saying 'tune by ear' - but, that would require cutting the port tubes and they're expensive! 5) Is there another way to do this?
Many thanks in advance!
EDIT: Oh, and here's one of the flitches I got for the veneer work. Really nice red gum - the grain will run just like the renders - vertical bookmatched up the front; horizontal across the sides with the horizontal wrapping around the front edge of the side panels. I have something sweet planned for the horn cradles!
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No need to seal the port tubes as there's little to no internal pressure in a ported alignment.
The purpose of lining the enclosure is for dampening of resonances and in your case, 3/8" thick material is basically useless. I'd line all internal surfaces with Roxul batting which is roughly 3" thick. I'd also wrap the port tubes with it.
The purpose of lining the enclosure is for dampening of resonances and in your case, 3/8" thick material is basically useless. I'd line all internal surfaces with Roxul batting which is roughly 3" thick. I'd also wrap the port tubes with it.
There's enough pressue to stop the cone moving almost entirely at port tuning. Lots and lots of pressure there.
Above Fb, the cone is moving and the air in the port is near-stationary. Some pressure there, too.
Chris
You should apply the damping material to the back, one side and either the top or bottom. You're trying to reduce releflections. Roxul is an OK choice but any loose insulation should have a thin cloth covering to prevent it from getting dislodged or blowing particles out of the port. Altec did this with scrim. It's like the cloth on the bottom of a couch or chair, porous but good enough to hold things in place. If you see a picture of a Model 19, it appears to have a black interior but it's just the cloth covering the fibreglass insulation they used. 2 or 3" Roxul is better.
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Thanks for all of the suggestions! I'm a bit leery of fiberglass, so I ordered a 6-pack of the Ultra Touch recycled denim insulation in the R6.5 rating from home dumpster. According to the online in-stock tool, my local Menard's said they had the R13 in stock, but at $65 bucks it's a bit pricey, looks to be very thick (3.5"?), and is WAAAYYY more than I'll ever use. The R6.5 stuff should be plenty for the top, one side, and the back, and if I find I need to double it up, I should have enough to do so. My OCD on the fiberglass particles is also put at ease by the recycled cotton, and the data I've seen online suggest that this stuff is at least as good as other materials out there.
Here's another question - for you folks with the crossover mounted to the rear panel, do you just cover the crossover with insulation, or do you hang the insulation from the cabinet top? Any harm in the insulation directly contacting the crossover?
Here's another question - for you folks with the crossover mounted to the rear panel, do you just cover the crossover with insulation, or do you hang the insulation from the cabinet top? Any harm in the insulation directly contacting the crossover?
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Well, I've installed the ST material on one side, the bottom, and hung one piece from the top of the cabinet about 2-3" from the cabinet back so that there is a bit of space for the crossover. Have also fashioned some supports for the port tubes and covered those with the same ST insulation. I've cut my port tubes to 8". According to WinISD that gives me a tuning of right around 27Hz - which I think is pretty close to optimum for the driver. Been listening to them for a bit over a week.
They sound good. Really, very good. They don't have the top end of my Focals, but what is there is fantastic! I am thrilled with how these came out, and couldn't be happier with the sound. But... being the tinkerer that I am, I've ordered parts and have been putting together a pair of Z-19 crossovers. I'm using 1/4" birch ply and Soren caps - everything else is pretty much from the list that Zilch put together years ago from Parts-Express. My layout is very slightly different, but I've heard amazing things about this crossover, and what the heck, it can't hurt, right?
Need to get a few more small screws and bolts to get this all secured, but this is what I've done so far. It's all nicely sanded and finished with a couple coats of water-based poly.
What do y'all use to stick caps and resistors onto things? I was thinking either hot glue or silicone, but it may be hard to find high temp silicone around here. How warm do the wire wound resistors get? Would I be good using just plain 'ol hot glue? I've seen a lot of folks stick caps on with that... Many thanks!
They sound good. Really, very good. They don't have the top end of my Focals, but what is there is fantastic! I am thrilled with how these came out, and couldn't be happier with the sound. But... being the tinkerer that I am, I've ordered parts and have been putting together a pair of Z-19 crossovers. I'm using 1/4" birch ply and Soren caps - everything else is pretty much from the list that Zilch put together years ago from Parts-Express. My layout is very slightly different, but I've heard amazing things about this crossover, and what the heck, it can't hurt, right?
Need to get a few more small screws and bolts to get this all secured, but this is what I've done so far. It's all nicely sanded and finished with a couple coats of water-based poly.
What do y'all use to stick caps and resistors onto things? I was thinking either hot glue or silicone, but it may be hard to find high temp silicone around here. How warm do the wire wound resistors get? Would I be good using just plain 'ol hot glue? I've seen a lot of folks stick caps on with that... Many thanks!
I think ,,, a hot glue gun will work fine.... and if you play them loud enough to get the
crossovers even warm to the touch... you have to be hard of hearing or want to be..!!
I just had bought in DEC. 2015 ..the whole Altec 19 parts set from Great Plains Audio.. except the 2 811B horns I had to buy used...I bought the Altec 19 crossover because it has a Midrange and Treble control...that crossover uses a by pass circuit for the treble to extend the upper frequency...
I am still waiting on my model 19 clone..cabinets getting finished..(had the Amish build them.)
I knew it would take a while but they will look perfect !
I had measured the voltage at the horn when playing some pretty darn loud horn music and the peaks were .65v it was way way to loud. !!
So I dont think your ever going to heat up the crossovers...
I like to listen to some things loud.. but the Altecs can do that with under 20 watts !..
maybe a little more power with some kick bass but the horns...they dont take much to get really loud... My room is 16.5 x 24 and it fills it up fast.....
I wish the cabinets were done......... SOON.,,;;
ohhhh i see you built the crossover to !. awesome... it looks great...
everything has space..I dont think you will ever have trouble from that...
Just hot glue everything... and the coils have wire ties...
It should last a lifetime.....
crossovers even warm to the touch... you have to be hard of hearing or want to be..!!
I just had bought in DEC. 2015 ..the whole Altec 19 parts set from Great Plains Audio.. except the 2 811B horns I had to buy used...I bought the Altec 19 crossover because it has a Midrange and Treble control...that crossover uses a by pass circuit for the treble to extend the upper frequency...
I am still waiting on my model 19 clone..cabinets getting finished..(had the Amish build them.)
I knew it would take a while but they will look perfect !
I had measured the voltage at the horn when playing some pretty darn loud horn music and the peaks were .65v it was way way to loud. !!
So I dont think your ever going to heat up the crossovers...
I like to listen to some things loud.. but the Altecs can do that with under 20 watts !..
maybe a little more power with some kick bass but the horns...they dont take much to get really loud... My room is 16.5 x 24 and it fills it up fast.....
I wish the cabinets were done......... SOON.,,;;
ohhhh i see you built the crossover to !. awesome... it looks great...
everything has space..I dont think you will ever have trouble from that...
Just hot glue everything... and the coils have wire ties...
It should last a lifetime.....
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