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DIY speakers

Tube Radio

Tube Radio

Super Member
I started a thread awhile back about these speakers, but I thought I would clear things up by just describing the way the speakers are now as IMHO the original thread was quite confusing.

I have a couple of speakers that came from a Magnavox Astro-Sonic console. Each styrofoam speaker box consists of one 12 inch woofer and a horn tweeter. I removed the speakers from the styrofoam boxes and mounted the woofers in a pair of 12 inch subwoofer boxes bought at Wall-Mart. I then set the horns on top of the boxes with one Pyramid TW 18BK tweeter mounted on each horn. I will post a schematic of the crossover I designed. It's not professional, but works quite well. The crossover components are mounted in two Radio Shack project boxes using solid copper enameled wire for the ground connections as it just looked better than stranded wire and was easier to work with as I could thread it through all ground connections before soldering anything without having to cut and strip individual wires.

feel free to make any corrections and or improvements to the crossover as I'm a newbie at crossover design. Given how good these speakers sound I may want to experiment with building more speakers in the future. Overall I am very pleased at how these speakers turned out. This would be a good time for me to buy a digital camera so I can post some pics.
 

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Are the boxes you have the drivers mounted in approximately the same size as the original boxes?

Were the original boxes ported or sealed? The new Walmart boxes, ported or sealed?

And it looks like you are doing well so far.
 
Thanks. I think the boxes are slightly larger which isn't a problem as it helped the bass out. The original styrofoam boxes were sealed. These boxes are also sealed. I used plumbers putty for the seal between the speaker and box. I had to replace the dust caps on the 12 inch woofers as I had to remove them to see why the voice coil in both speakers was rubbing after I drilled eight holes in each speaker for the mounting screws which it had provisions for, but since it was in a styrofoam box mounting holes were not needed. I'm currently using these speakers with a Yamaha Natural Sound Stereo Receiver R-300 (soon to be replaced by a pair of ASL Wave 20 monoblocks once they are shipped to me) which is driven through its tape input by a Sony TAE 5450 stereo preamplifier. Overall these speakers are pleasing to listen to although I do wish the Magnavox horns went lower. Shortly after I got these speakers I added the bullet horn tweeters per the advice of GordonW to add a little energy above 13KHz which dramatically improved the sound.
 
I'm replacing the Magnavox horns with these hornshttp://www.partsexpress.com/pe/psho...elenium HL14-25 1&CFID=29759&CFTOKEN=56551613. The drivers are here http://www.partsexpress.com/pe/psho...2&FTR= DT150-OEM &CFID=29759&CFTOKEN=56551613. I just figured I would try a new horn and see if the sound improves any. I do believe I have grown quite fond of building my own speakers. I'm almost tempted to find another pair of 12 inch 8 ohm Magnavox Astro-Sonic speakers or other 12 inch 8 ohm speaker capable of going down to 20 Hz and cross them over at some frequency under 100 Hz. Not sure if I will do that though unless I stumble across some speakers cheap.
 
I was thinking of using them as a passive subwoofer which would save the Magnavox speakers since I already had to patch one up where the surround meets the frame. I'm not sure I want to get any more speakers right now. Maybe I will do that in the near future. Those Magnavox speakers soud good down to 20Hz. I like to experiment with things like this and se what works and what does not. Ioike a basically flat sound,but on some songs the Scott sounds like it is lacking in bass whereas on other songs it sounds just right.
 
I would have expected a smallish sealed box with a high efficiency drivers to have essentially no output at 20hz. Have you confirmed this with test tones? Ive had some similar maggie speakers and haven't noticed any significant bass extenion.
 
Paul C said:
Dayton, from Parts Express, has an excellent 12" 8 ohm speaker that works in 2-3 cft cabinets. http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=295-320

I think macaltec has these in some Santana cabinets.

But why do you need to cross them so low (under 100 hz?)
Click to expand...

The Dayton Classic 12" woofer is pretty impressive for the money and response extends down into the high 20's quite easily and still remains fairly efficient. The top end of the response also lends itself quite well to use in a 2 way design.
 
In their original styrofoam boxes they lacked in the low bass, but putting them in their current boxes helped the bass out a bit. I increased the value of one coupling cap in each channel of the cott amp as that cap served to limit the bass response to 20 Hz. I tested the speakers again and got better output at 20Hz and one song I use to test the bass response of speakers and amps which has some frequencies below 20 Hz in it sounded better. The new horns came in today. After adjusting the Lpad ro set their levels properly they sound quite nice. The Magnavox horns sounded nice except at certain frequencies the horns sounded like they were breaking up. I plan to build a mounting board to arrach the horns to so they will be level and I plan on mounting the super tweeters immediately above the horns. I may try these horns 8 inch http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=270-308 10 inch http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=270-310 or 12 inch http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=270-312 for the drivers and see how that sounds. Which ones do you think will work best in my system?
 
I was suggesting the Dayton Classics as replacements for your present 12's, rather than use as a subwoofer.
 
Check my first post. I updated the schematic to reflect that I am now using an 8 ohm driver for the horn. I never thoight DIY speakers could sound so wonderful. I find myself actually enjoying listening to music :music: again. A lot of it has to do with the Scott amp, but changing the horns did the most good. I still have not received the new 8 inch round horns to try the drivers on yet. I figured those would give me about the same dispertion as a regular cone speaker. Besides the horns I have now are really meant for a long throw application not up close listening. Like I've said before these horns don't seem to break up as easily as the Magnavox ones did. Had I extra money I would re-designe the crossover and use a horn capable of a lower crossover point. I have a good thing going right now so I'll leave it as is.
 
I installed the 8 inch horn lenses and tweeters in a pair of Realistic MC-1000 speakers about two weeks ago. I made mirror images of the drivers with the speakers sitting on their side. I put the drivers as close as I could to the bottom of the speaker boxes which are placed horizontal instead of vertical like the boxes originally were. I cut the holes in the rear of the speaker boxes and the wires come out the front through the speaker grille. That has the added benefit of making it easy to get to the speaker connections and also to the horn driver should it ever need to be replaced or should I decide to roll in different drivers. These speakers sound wonderful. I believe that I will keep the Magnavox woofers for the time being as they sound good enough for my ears. The main problem was two coupling caps in the Scott amp. I had to increase their value somewhat as the original caps were selected to provide a roll off at 20 Hz. I replaced them with .22uF caps and the bass response improved nicely.
 
In the near future I may try and replace the Magnavox woofers with some new ones and see how that sounds. If I do that what should I make the cabinets out of?
 
Two primary materials are used in cabinets. MDF and high grade plywood. The two schools of thought are use MDF and make the enclosure very dead, or use plywood for a more lively enclosure. For me, I like bass drivers in very stiff (braced plywood) cabinets and mids in very heavy well damped enclosures.
 
I may try plywood.
I do want a new woofer as those Magnavox speakers will not last forever, besides I want some decent looking speaker cabinets :D.
I've got some measurements here.
For this woofer http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-118 the box should be
29 inches length
18 inches width
40 inches heigth
equals
12.08 Cubic Feet

That's the only one I could find that goes down to 20 Hz. That would work great if I wanted some floor standing speaker cabinets.

It's becoming increasingly difficult to find speakers that go down to 20 Hz without the cabinets becoming furniture due to their shear size.
I may use this midrange http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-402 with a suitable subwoofer.
 
I may build the boxes.
My dimentions will be
21 inches length
24 inches width
41 inches height
equals
11.96 Cubic Feet
Closest as I can get to the recommended 11.91 cubic feet.
If built with 1/2 inch plywood with 1/2 inch taken off the measurements which will be the inside dimentions of the box I get 11.29 Cubic Feet.

How should I go about placing the drivers in the cabinets? My current configuration has the woofer on bottom the midrange about three inches from the woofer and the tweeter about 1/2 inch from the midrange and about three inches from the woofer. Would that work for the new boxes or not. Also where exactly should I put the drivers since the boxes will be kind of tall?
 
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