DIY Folded-Horn Speaker Design from 1955

[maxhifi]

I built these beautiful speakers in mdf and I put a fostex 126, they really sound great, I love them, they have an impressive quality and depth
View attachment 1045867

What thickness of mdf did you use? The plans call for very thin material.

This is a very appealing project, yours look really nice too. Hard to believe this was conceived in the mono era.

I wonder what the specs of the jensen P5TX actually are, and if it's possible to find a pair somehow

 

[OMGCat!]

Those speakers look really nice centinela! I sometimes wish I had any woodworking ability at all but then again I'd probably have even more stuff around my house so maybe it's a good thing that I don't.

 

[centinela]

I was really looking for 19 mm mdf, but I could not find it, so I used for my project 15 mm mdf, I built two speakers for stereo sound, the most complicated was to work with angles and with few tools, mostly manuals, I am even thinking of replicating them and making some adjustments, but I think that they were very good and the fostex gives them a great sound. Finally, in addition to felt and poliestre in some walls use cork, in the empty spaces as I commented previously I will fill with sand not only gives greater firmness to the speaker but also is an excellent audio insulator.

 

[maxhifi]

I was really looking for 19 mm mdf, but I could not find it, so I used for my project 15 mm mdf, I built two speakers for stereo sound, the most complicated was to work with angles and with few tools, mostly manuals, I am even thinking of replicating them and making some adjustments, but I think that they were very good and the fostex gives them a great sound. Finally, in addition to felt and poliestre in some walls use cork, in the empty spaces as I commented previously I will fill with sand not only gives greater firmness to the speaker but also is an excellent audio insulator.

Where are you located?

 

[maxhifi]

After reading the article last week, and thinking about it, I'm building a pair, as per original plans. I'm a sucker for those old articles. Have a pair of new old stock Quam 5" drivers from the fifties, similar to the Jensens in the original plans.

Got most of the wood cut today, will finish tomorrow, and glue them together. I'm only using particle board so will just paint them black.

Only investment is a sheet of particle board and a bit of time, will be interesting to see how they sound!

 

[centinela]

I live in Bogota, Colombia, I bought my fostex online, I have two projects in mind, one is to build a Fonken speaker and another is to buy old speakers and modify them, build a new box in mdf and place a Linkwitz-Riley Crossover electronic instead of the passive crossover, these are crazy things that I like to do.

 

[maxhifi]

I live in Bogota, Colombia, I bought my fostex online, I have two projects in mind, one is to build a Fonken speaker and another is to buy old speakers and modify them, build a new box in mdf and place a Linkwitz-Riley Crossover electronic instead of the passive crossover, these are crazy things that I like to do.

Cool! I couldn't figure it out from the photo, didn't really look like North America, and didn't really look like Europe.

I'm not sure I will get fostex but they look like a great choice for this type of speaker. What attracted you to this design?

 

[centinela]

I had some QSC AD52 speakers, which sounded really bad, I decided to modify the cabinet, but the QSC people did not want to give me the woofer or the tweeter data, I did not have money to buy others, so I found the linear transmission speakers in Frugal, I began to search and investigate much more, I found by mistake the popular mechanics article,, most of the speakers seemed very complicated for my limited knowledge of carpentry, and when I analyzed them, I determined that these were viable for the unknown woofer of qsc ( a huge computer woofer to be honest), with them lasted almost two years, until I could save and buy the fostex, and stayed as a glove as we say here in my country. I still have not wanted to surrender with the QSC and I changed the tweeter for a vifa and improved by much in the high, I built another box, but lost completely in the low, and there I go, stubborn very stubborn, to want to recover my investment with Those qsc, but in no way I have managed to sound good those horrible woofer. However, with my popular mechanic speakers I am more than satisfied, I really do not need anything else, it was worth the investment, the sweat and the tears. A great sound definitely.

 

[maxhifi]

I've got everything cut out now except the pieces with angles. I didn't have enough time to do it all yesterday. Luckily I have a table saw to work with, and although it's a pretty bad one, I've learned to compensate for its flaws. I should be able to get them all glued together tonight. You put sand in the empty cavities? How did you keep it from making a mess? I was thinking maybe to add some cement to it, or just put some small rocks instead of sand. I think a bag of lead weights would be perfect, but I don't really know where to get lead weights in that quantity for a cheap price.

 

[centinela]

https://www.pcpaudio.com/pcpfiles/doc_altavoces/materiales/materiales.html
look at this link although it is in Spanish about sand say
"Excellent material, cheap and easy to find, although it has the disadvantages of not being solid and non-deformable.

There is nothing that absorbs the vibrations better. It also adds mass to the speaker, which provides a different sound, more solid and with deep bass.

To apply it, usually a double wall is made, with the fewer points of union better, and this is usually difficult to build."
I also place an image pointing to the places where I will place the sand

 

[maxhifi]

Makes sense to me! I am mostly worried about sand leaking out, over time. Maybe if it's sealed very well. Also, to be sure to get sand without any insects in it. I think that a bit of sand should damp the enclosure quite well, and it's definitely cheap.

 

[centinela]

sand in tannoy speakers

 

[maxhifi]

Did you notice something strange about these plans? For example piece 3 is the wrong length, and needs two angles.

As is, it's not going to work - I'm going to redraw it with proper measurements and the correct angles before I waste anymore wood. And check all the other parts.

 

[45rpmspinner]

I'm going to redraw it with proper measurements and the correct angles before I waste anymore wood. And check all the other parts.

If you could post a revised plan...that would be fantastic. I'm thinking of making a pair myself.

 

[centinela]

I drew it in Autocad, but I do not have the blueprints in this software anymore because I changed my computer, I did not have any problems with the angles, only when I was cutting them, because I had to work with my nails.

 

[centinela]

.Another way to do it is to cut all the pieces except the 3, mount inside out, then once you have all armed you measure and cut the 3, is the fastest and avoid wasting material, Look, I put in green the two that you have to mount and then measure the 3 (orange)

 

[maxhifi]

If you look at the bill of parts, 3 is shown as having only one angle on it, but from the diagram it needs two. Also, it's too short by a small amount. I know I could fit it by cutting until it fits, but I hate working like that, I want to cut all the boards exactly, and then just assemble it

I was thinking about CAD too, but maybe I will do it by hand. I think 3 may be the only piece with mistakes, but still I want to calculate some things, for example how far from the front the bottom of 5 should be.

A measured drawing would be really useful, all we know about the placement of 5 is the angles, for example.

Cutting the sharp angles (<45) is a small challenge, even with decent tools! This is a good project

 

[centinela]

look at one possibility is to do the calculation by Pythagoras, so things have two sides one 10 3/4 "( 273mm) and another 12" (304 mm), which would give us 16 7/64 " (409,33 mm) approximately, with two angles of 41,8 and 48,17 approximately. that's why I preferred to mount, measure and cut.
PD By the way, it is better to recalculate all the angles if you had a problem with one

 

[centinela]

because remembering, I had spaces left that I had to fill in, in table 3, in table 9 and table 10, there is not even that space between table 9 and table 10 that appears in the chart.

 

[maxhifi]

look at one possibility is to do the calculation by Pythagoras, so things have two sides one 10 3/4 "( 273mm) and another 12" (304 mm), which would give us 16 7/64 " (409,33 mm) approximately, with two angles of 41,8 and 48,17 approximately. that's why I preferred to mount, measure and cut.
PD By the way, it is better to recalculate all the angles if you had a problem with one

View attachment 1050389

You said it. As soon as one board didn't fit, I decided it's time to take a step back, and check the whole drawing. I'm pretty bad at AutoCAD for dimensioned stuff, I'm more used to doing "not to scale" electrical drawings. I can see why this gave you some trouble, the design is not exactly perfect. I wonder how many of these old designs have errors like this. My wife suggested I write a letter to Popular Mechanics and tell them about the mistake