Bob, Those are probably worth building from wood.
Guys, I am wondering if we are wandering away from sound reasoning. Foam core is not a good material to build speakers from but it has allowed us to build designs that would otherwise be beyond our abilities or at least are fast enough to build to determine if we then want to use wood.
Guys, I am wondering if we are wandering away from sound reasoning. Foam core is not a good material to build speakers from but it has allowed us to build designs that would otherwise be beyond our abilities or at least are fast enough to build to determine if we then want to use wood.
I agree, but I've still got the idea of doing some sort of horn using thicker FC material in the back of my head. It doesn't have the nice smooth curves you like, but a mini Klisphorn would be fun to try with a combo of wood and foam. There would be a lot of conversion math involved, but that's why I pay you the big salary you get in the mail every week.
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Cal, that is exactly what I was getting to. I even said as much in my response that it is a wonderful tool for modeling, it just did not work in this particular instance.
I also respectfully disagree with the assumption that 1354's are "thin" in the lower end. I have built many designs that will play into the 40Hz range with authority. Sure, one needs a subwoofer for the last octave or so, but not many 5" drivers can get away without a sub anyhow. I used a set of voigt pipes with 1354's like you for television for years. I also took a pair of bi-poles to DIY Dayton 2002 and blew folks away with how low they would play. They are really fun drivers to play with.
Regarding thicker material, I would LOVE to pick up a few sheets of the 2" pink foam board from Home Depot, load it to the floor, from the ceiling, with a compression/all-thread clamps, and see what a 12" in an 8' MLTL would do.
I also respectfully disagree with the assumption that 1354's are "thin" in the lower end. I have built many designs that will play into the 40Hz range with authority. Sure, one needs a subwoofer for the last octave or so, but not many 5" drivers can get away without a sub anyhow. I used a set of voigt pipes with 1354's like you for television for years. I also took a pair of bi-poles to DIY Dayton 2002 and blew folks away with how low they would play. They are really fun drivers to play with.
Regarding thicker material, I would LOVE to pick up a few sheets of the 2" pink foam board from Home Depot, load it to the floor, from the ceiling, with a compression/all-thread clamps, and see what a 12" in an 8' MLTL would do.
Tell me the 12 in driver specs and I will see if I can get you a design. I can get AkAbak to sim MLTL's now. The AMLTL technique has still proven to be pretty effective so far mid to higher Qts drivers. I agree wood makes nice speakers but try to move your 8 ft tall MLTL around if it was made of 3/4 in ply
I think IG made a crazy long 3 m TL with double wall FC. KenBird made a Tunnel TL with a FR10. Someone made a bass reflex for an Alpair 7. All appear to be 4 in class. The 5 in class have been cornu foam core. You may be right about the size of the 1354 it is in the 5.5 in class and shakes the cabinet. You are right about my stuff, all Tc9 projects or smaller. I am looking forward to moving up to the next size driver. Maybe an 8 incher is what I am thinking. A Visaton BG20 or a BetsyK. Oh I do remember somone made a Karlson with a 8 in driver, they said the K aperture flexed like mad under the sound pressure. Definitely want to double or triple thick layer there.
The 1354 uses a generic 5.25" EG stamped steel pincushion frame that was popular in it's day. It was a plain jane automotive driver but held it's own against the 'boutique' drivers, better than some 2-ways that sold for much more. You just had to be creative about how it was used as it was just a raw driver.
I wanted to. It will be light, but I figured I could use 2-3 5/16" allthread to make a "compression" load on the top of it, forcing it to the floor. Line the thing every six inches with window braces all the way down. I have a 4" and 6" flare port on the racks here already. It would not be practical for much of anything but would be fun in the garage.
For vented, maybe so. However, for any TL speaker, a higher Q is desireable.
From MJK spreadsheets via Bjorn Johanssen
Qts -- I use a Qts value of 0.35 to distinguish between high and low Qts. You might have another definition. Drivers with a high Qts perform better than driver with low Qts in a quarter wave design. On the other hand, the lower Qts driver seems to require less volume, thereby resulting in a smaller enclosure. Low Qts drivers have a roll off that starts earlier than high Qts drivers, and drivers with a moderate or high Qts will often result in the best low end performance. But this is also a matter of taste and preferences. "Good sound" is defined by you only. The output from the opening is broader with high Qts drivers, compared to low Qts drivers that have a narrower output from the opening. Drivers with a Qts lower than 0.30 seem to be difficult to control in a TL.
From MJK spreadsheets via Bjorn Johanssen
Qts -- I use a Qts value of 0.35 to distinguish between high and low Qts. You might have another definition. Drivers with a high Qts perform better than driver with low Qts in a quarter wave design. On the other hand, the lower Qts driver seems to require less volume, thereby resulting in a smaller enclosure. Low Qts drivers have a roll off that starts earlier than high Qts drivers, and drivers with a moderate or high Qts will often result in the best low end performance. But this is also a matter of taste and preferences. "Good sound" is defined by you only. The output from the opening is broader with high Qts drivers, compared to low Qts drivers that have a narrower output from the opening. Drivers with a Qts lower than 0.30 seem to be difficult to control in a TL.
The Qts is not too big for a MLTL, it will let you reach a frequency lower than the fs of the driver which is already low. The recommended vol is 12.4 cu ft for vented enclosure. If you make a 96 in tall box that is 14 in wide x 8 in deep x with a single fold (total depth of 16 in) for a TL of 192 inches, that should give a pretty low fb of 17.5 Hz. Now calculate the vent using WinISD based on the diameters you have on hand with recommended tuning freq, and it will drive actual MLTL tuning freq down into 12 to 15 Hz range. Be careful with driver excursion. You can also just make a shelf vent and save your flared tubes. You will have a theater style sub that can reach 12 Hz at 101 dB with 4 watts of power! What does a sub at 12 Hz sound like? Whamp whamp whamp whamp whamp like a helicopter.
If 12 Hz is too low for your taste, don't fold and you have a nice 20 Hz capable sub.
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That looks like it might be an awesome little project!! Would be very cool to run it off of a small chip-amp I have (I think it is 14W). That would just blow some neighbors minds...and probably make my wife very happy...heh...
I am on my way to The Depot to check and see how much this styrofoam is and hope I can fit full sheets in my Suburban.
I am on my way to The Depot to check and see how much this styrofoam is and hope I can fit full sheets in my Suburban.
Motownman,
Very cool, glad to see you are excited. I will calculate vent and box dimensions. Are you interested in the 10 Hz or 20 Hz version? I may give this a go with AkAbak and do a real MLTL sim rather than just a AMLTL estimate. It will be something if this thing can indeed pump out 101 dB at 10 or 20 Hz with little more than a flea amp. A suburban can hold full size 4x8 ft sheets of ply or foam no problem. You need to fold/remove rear seats?
Very cool, glad to see you are excited. I will calculate vent and box dimensions. Are you interested in the 10 Hz or 20 Hz version? I may give this a go with AkAbak and do a real MLTL sim rather than just a AMLTL estimate. It will be something if this thing can indeed pump out 101 dB at 10 or 20 Hz with little more than a flea amp.
A suburban can hold full size 4x8 ft sheets of ply or foam no problem. You need to fold/remove rear seats?
X,
The problem is I have my three kids with me (three car seats). I just measured and if it were not for my four year old, it would fit....ugh... She would not be cool with having a sheet of styrofoam over her head and I don't think I could listen to it all the way home. Might be able to pick it up next week (weekend won't work because it is Lone Star Audio Fest!!!)
I think I would rather try the 20Hz version, because it will still have some gain for the lower frequencies....but don't know what xmax will be there. Regardless, I don't think I have any FLAC's that have infrasonic information to them. I am betting that the 25-35Hz info will be rather impressive though...and it will have to be corner-loaded too (the only place I can put it in my garage). With it there, it will be between two racks of industrial type shelving, so it will be hidden. My neighbors know I have been working on these Radio Shack speakers, so I will just wait until I get this sub built and then invite them over to listen to the Radio Shacks. I bet I can make them shart themselves...
The problem is I have my three kids with me (three car seats). I just measured and if it were not for my four year old, it would fit....ugh... She would not be cool with having a sheet of styrofoam over her head and I don't think I could listen to it all the way home. Might be able to pick it up next week (weekend won't work because it is Lone Star Audio Fest!!!)
I think I would rather try the 20Hz version, because it will still have some gain for the lower frequencies....but don't know what xmax will be there. Regardless, I don't think I have any FLAC's that have infrasonic information to them. I am betting that the 25-35Hz info will be rather impressive though...and it will have to be corner-loaded too (the only place I can put it in my garage). With it there, it will be between two racks of industrial type shelving, so it will be hidden. My neighbors know I have been working on these Radio Shack speakers, so I will just wait until I get this sub built and then invite them over to listen to the Radio Shacks. I bet I can make them shart themselves...
Goldwood GW-412D Monster FC Sub MLTL
I just ran an AkAbak sim for the Goldwood monster foam core sub as a MLTL.
Design: 14 in wide baffle x 16 in deep cabinet x 96 in tall, with a 14 in wide x 4 in tall x 11 in deep "shelf vent" at the bottom. Use COPIOUS bracing with additional foam strips in both directions to reduce foam wall flex. In AkAbak, I optimized the driver location which appeared to give the best response with good efficiency when driver is mounted at 53 inches from the top (3.58 ft from floor - about seated ear level). The simulation doesn't yet account for stuffing so there are peaks that really shouldn't be there with proper damping. I would recommend starting with using stuffing at about 0.5 lb/ft^3 of pillow stuffing or polyfill in the top 64 inches of the speaker cabinet. Adjust to taste. I have also calculated speaker cone displacement at 4 watts - you will not want to exceed 4 watts if you have musical content below 20 Hz. Most amps crap out below 20 Hz anyway and you have a built in high pass based on low-end of amp. But the speaker max displacement is 3.5 mm so you should be under this if you stay below 4 watts at 20 Hz. Above 20 Hz, you can put more juice to it.
The frequency response chart is attached below and shows indeed 96 dB of SPL at 20 Hz driven by 1 watt at 1 meter with speaker back placed against the wall to minimize baffle step losses. And at 4 watts (5.66 volts) the speaker should produce 103 dB at 1 meter! Whamp, whamp, whamp, whamp, whamp !!!
Let me know if this design sounds OK, and if you need more info.
Sounds like a boat load of FC fun!
X
I just ran an AkAbak sim for the Goldwood monster foam core sub as a MLTL.
Design: 14 in wide baffle x 16 in deep cabinet x 96 in tall, with a 14 in wide x 4 in tall x 11 in deep "shelf vent" at the bottom. Use COPIOUS bracing with additional foam strips in both directions to reduce foam wall flex. In AkAbak, I optimized the driver location which appeared to give the best response with good efficiency when driver is mounted at 53 inches from the top (3.58 ft from floor - about seated ear level). The simulation doesn't yet account for stuffing so there are peaks that really shouldn't be there with proper damping. I would recommend starting with using stuffing at about 0.5 lb/ft^3 of pillow stuffing or polyfill in the top 64 inches of the speaker cabinet. Adjust to taste. I have also calculated speaker cone displacement at 4 watts - you will not want to exceed 4 watts if you have musical content below 20 Hz. Most amps crap out below 20 Hz anyway and you have a built in high pass based on low-end of amp. But the speaker max displacement is 3.5 mm so you should be under this if you stay below 4 watts at 20 Hz. Above 20 Hz, you can put more juice to it.
The frequency response chart is attached below and shows indeed 96 dB of SPL at 20 Hz driven by 1 watt at 1 meter with speaker back placed against the wall to minimize baffle step losses. And at 4 watts (5.66 volts) the speaker should produce 103 dB at 1 meter! Whamp, whamp, whamp, whamp, whamp !!!
Let me know if this design sounds OK, and if you need more info.
Sounds like a boat load of FC fun!
X
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The calculation above is for one of the voice coils in the DVC driver. With both coils firing and driven by a stereo amp, add 3 dB to the calcs above! 106 dB at 20 Hz with 4 watts per channel!!!! Yahhh baby!
Edit: you may be able to get away with tossing entire pillows with their factory covers still on inside the cabinet rather than remove the sacks with bare stuffing. Go to Bed Bath and Beyond and buy four of the 4 ft long "body" pillows at $5 ea. Throw them in en masse... Although you will have to work them around the bracing somehow... may require gutting pillows after all ?
Edit: you may be able to get away with tossing entire pillows with their factory covers still on inside the cabinet rather than remove the sacks with bare stuffing. Go to Bed Bath and Beyond and buy four of the 4 ft long "body" pillows at $5 ea. Throw them in en masse...
Although you will have to work them around the bracing somehow... may require gutting pillows after all ?
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