Fred Fliinstone end/coffee table SUB

[Kingo]

Before I present the Flinstone end/coffee table sub design I have to say I dont have woodworking ability and very few tools...so I decided to build this sub based on the little ability and 4 or 5 tools I have. Good thing is the sub goes tucked in between the corner wall and a sofa so details and posible flaws wont be that visible. Also the wife likes rustic stuff.

I was given a couple of Technics 2way speakers that I decided to siamese for this project. Will use the original 10 inch woofers which are in good shape and sound pretty good; aimed at about 6 inches from the the floor. Ports are 1 7/8" I.D. and 2.5 inches long. Havent decided yet if going sealed or ported. Overall table size is 17" high and 27.5 x 28.5 on the top.

Going to use a 120hz 2nd order passive crossover on each woof powered by 50 watt each channel...or maybe a 4ohm plate amp(80 watts) and wire woofs in parallel. Has 100 or 120 hz selectable xover, level and phase control. Will decide on that later.

The legs and top of table are made out of 2" x 6" wood(pine, I think) since I have a miter saw. Easy to cut and work with. I mocked the box up fastened with 2 1/2 inch wood screws just to see the fit and how it looks. Will dismantle, sand and glue everything up and retighten with screws. Screw holes will be filled with wood filler, then resanded and finished with Varathane wood tint(color Gunstock) which matches well with existing component table.

So here are a couple of pics of the Flinstone end table sub progress. Any comments or suggestions are welcome!

[hillbillydeluxe]

Re: Fred Fliinstone end/coffee table SUB

what sub /specs?looks very sturdy

[BusterIrvine]

Re: Fred Fliinstone end/coffee table SUB

I love it, no-one would suspect that is a sub. Camouflaged system = high wife approval = happy home.

[Kingo]

Re: Fred Fliinstone end/coffee table SUB

@Buster,,yep it will go tucked in a corner. Wife can put some flowers over it and everybody happy..lol

what sub /specs?looks very sturdy

Im gonna use the 10 inch woofers these Technics boxes(model SB-LV305) came with. According to specs here http://service.us.panasonic.com/OPERMANPDF/SBLV305.PDF they go down to 44hz. Ports are 1 7/8" I.D. and 2.5 inches long. Dont know if I could get these to go any lower since I dont have T/S params. for the drivers and changing port size arbitrarily will most probably worsen sound. I'll experiment sealing the port and see if results are better. Boxes are 1.4 sq/ft I.D. each

[michiganpat]

Re: Fred Fliinstone end/coffee table SUB

go active with a plate amp...to do stereo passive 2nd order crossovers, you'll have as much into inductors as this amp goes for: http://www.parts-express.com/pe/show...number=301-506

this amp also has 6db of boost at 35hz to help out on the low end.....

I have a pair of these buyout subs sitting on the shelf:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=299-106

which sealed, calculate out to a Qb of ~1.1, with a 1.9db bump at 63.66 hz, an F3 of 37 hz, and an F10 of about 26hz...heavily stuff with fiberglass, and you might get it down to a Qb of 1 or so, which drops the F3 and F10 a few hz, and knocks the 1.9 db peak nearly in half....drill holes between the 2 boxes and seal them to each other, yielding ~78L, this sub calculates out to a Qb of .9, with a F3 of 33hz, an F10 in the 22-23hz range, with a .65db peak at 65hz...

come to think of it, my friend around the corner bought a single sub, and I think the 70W dayton plate amp to make his own subwoofer, but never got around to it....he might be interested in selling....

[michiganpat]

Re: Fred Fliinstone end/coffee table SUB

or, IF you wanted to do totally passive, with that buyout sub I listed, you could attach the boxes baffle to baffle and cut a port in one, making a 4th order bandpass box....quick sim shows the sealed side at 1.25 cubic ft, the ported side at 1.17 cubic ft, tuned to 51hz with a 3" dia by 4.07" long port (could use polystyrene or bracing to reduce cabinet volume) yields an F3 of 30hz, a high end F3 rollof of 87hz

[Kingo]

Re: Fred Fliinstone end/coffee table SUB

Thanks michiganpat for your comments and suggestions. I have a plate amp but havent decided if I want to go active or passive. Ebayed a passive 2nd order subwoofer xover that crosses at 150hz. Looks pretty good for just $9.99; inductors alone are worth double the amount so if it doesnt work out will use for parts.

The 2 boxes are screwed together but are individual to each driver. Would there be an advantage to cut a hole between the 2 and use it as a bigger volume box with the subs wired in parallel??

[bkeane1259]

Re: Fred Fliinstone end/coffee table SUB

Go active. That 150Hz low pass filter most likely has really cheap inductors with thin wire and high DCR that will rob some of your bass. Additionally, crossing that high (150Hz) will easily localize your sub, meaning you will "hear" exactly where it is. Your table idea is awesome. If you can get a decent plate amp and cross it around 80Hz to minimize localization, it will be virtually impossible to tell where the bass is coming from. Then you can really wow your friends. WIN WIN. Listen to michiganpat. He's got a couple great ideas up there.

[Kingo]

Re: Fred Fliinstone end/coffee table SUB

Ok,,thats good info. The plate amp I already have crosses at 100hz. Will give it a try and compare with the passive at 150..

WOW,,,was looking at your projects,,they're amazing..specially the Wildeman 2.1!!!

[michiganpat]

Re: Fred Fliinstone end/coffee table SUB

Go active. That 150Hz low pass filter most likely has really cheap inductors with thin wire and high DCR that will rob some of your bass. Additionally, crossing that high (150Hz) will easily localize your sub, meaning you will "hear" exactly where it is. Your table idea is awesome. If you can get a decent plate amp and cross it around 80Hz to minimize localization, it will be virtually impossible to tell where the bass is coming from. Then you can really wow your friends. WIN WIN. Listen to michiganpat. He's got a couple great ideas up there.

yeah, bandpass is really the only way I can see doing a passive sub with reasonable cost, since the configuration has it's own natural high-pass roll-off....

[Kingo]

Re: Fred Fliinstone end/coffee table SUB

Ok,,I tested the passive xover and the plate amp. The passive @150hz was horrible; vocals bledthrough and bass quality was not good at all. The RCA plate amp on the other hand, was very good with both drivers wired in parallel(4ohm). Thumped real nice and solid at 100hz XO point(and no voices); switched to 200 and not so good but still better than the passive. So the passive is going to the parts bin and the plate is the way to go. Will also test with longer port length to see if I can squeeze a bit more bass out of the boxes. Right now, according to my math, they're tuned to ~36.5hz. Port dia. 1.81in.,, 2.25 in. long ,, 1.46 cu/ft each. Maybe a 4.5 in. long to get it down to 28hz(dont know if the drivers will cooperate..LOL). Need to open hole for plate amp.

Also sanded the whole thing with 120grit paper. Will dismantle(again), sand with 220 and finish with stain.

[bkeane1259]

Re: Fred Fliinstone end/coffee table SUB

Ok,,I tested the passive xover and the plate amp. The passive @150hz was horrible; vocals bledthrough and bass quality was not good at all. The RCA plate amp on the other hand, was very good with both drivers wired in parallel(4ohm). Thumped real nice and solid at 100hz XO point(and no voices)

I was fully expecting this outcome. Cheap inductors in passive low pass filters don't do you any favors at all in the bass department. Even if you mocked up a passive crossover at 50Hz, the "proper" heavy gauge inductors would have been so expensive, you could have purchased a new plate amp.

Glad it's working out for you. Show us pics of the completed project when you're done!!

[Kingo]

Re: Fred Fliinstone end/coffee table SUB

I was fully expecting this outcome. Cheap inductors in passive low pass filters don't do you any favors at all in the bass department. Even if you mocked up a passive crossover at 50Hz, the "proper" heavy gauge inductors would have been so expensive, you could have purchased a new plate amp.

Glad it's working out for you. Show us pics of the completed project when you're done!!

Yep,,I suspected strongly that you were right about that but I wanted to hear the difference...the port diameter is pretty small for a 10 incher(picture in post #1) even though the calculations and design are by Technics. Cant say it sounds bad; but would a larger diameter, say 3" or 4" tuned to a lower frequency enhance the low freq. output??

Thanks for your help and advice!

[bkeane1259]

Re: Fred Fliinstone end/coffee table SUB

Cant say it sounds bad; but would a larger diameter, say 3" or 4" tuned to a lower frequency enhance the low freq. output??

Thanks for your help and advice!

With a larger diameter port, you will reduce the chances of audible chuffing, but if you tune the box lower, there's no possible way to know what sort of effects it will have on the driver without knowing the T/S parms and doing a proper sim. There are too many unknown variables.

If you’re experiencing chuffing, you could use a larger and longer port, but I’d keep the box tuning where it’s at as that’s how they were designed by Technics in the first place. You could run the drivers into dangerous excursion territory by arbitrarily tuning the box lower. Does that make sense?

OTOH, I suppose you could experiment.

[bkeane1259]

Re: Fred Fliinstone end/coffee table SUB

Yup- I agree with your calculations. The boxes are tuned around 36.5Hz. If you increase the diameter of the port to 3" the new length would have to be 7 13/16" long. But the cabinets are only 10 19/32" deep, so you're gonne be getting very close to that back wall....too close. Tuning any lower would require an elbow in the port.