My Dads homebrew uni speakers, need to build cabinets

[pingu_turbo]

i like that idea and you might just find some nice gutted cabs like that for cheap.

Yeah, that would be nice. But for some reason the Wxx series of speakers are quite rare over here. I would love a pair of w60/70/90's.

I would like them to look like these but obviously twice the height and maybe a different colour.

So when it comes around to actually building these cabinets, If I create the large cabinet and have a movable floor and ceiling so that they can be initially tuned. What I don't want to be doing is building these twice or more.

See what you think below. The areas are workings of the dimensions I currently know that the EMI 315 driver was working in and also the Goodmans were taken from the PDF that I was given the link for earlier.

Another thing, would one build the cabinet to the specs as seen below and then add the dampening material or would one have to account for the dampening material thickness when measuring up for cubic footage?

And as for dampening material would this egg box foam type stuff be ok? Would this be adequate for preventing bounce back from the back wall of the cabinet?

Any hints and tips would be helpful, I really am a blank canvas for speaker building. I was wondering to make the back walls of the cabinet angled to deflect away from the driver.

As mentioned earlier does anyone think it be beneficial to include another driver to compliment that horn, maybe a 6/8 inch or a dome tweeter to cover the ranges between the 12" and the horn?

I could also do with knowing what to do with the cabinet being ported or not?

On one last note I am going to start another thread requesting information on this EMI driver, see if that brings up anything. See thread here.

 

[kfa888]

I'd put the horn to the top so it is ear level. Then the 10 and then the 15. you still need all the parameters of the drivers before any plans can be made.

 

[nick12345]

There is always the Woofer Tester if you really want to get exact specs...

 

[audiobiker]

There is always the Woofer Tester if you really want to get exact specs...

yup, PE has them for just over a 100 bucks. a worthwhile investment for sure. that egg carton foam would work perfect :yes: although i would probably put more of it in the cabinet. that is just me though...

 

[pingu_turbo]

yup, PE has them for just over a 100 bucks. a worthwhile investment for sure. that egg carton foam would work perfect :yes: although i would probably put more of it in the cabinet. that is just me though...

I personally would put more in too, I just stole the pic from google as I found it. It was a good example of what I wanted to use.

I'd put the horn to the top so it is ear level. Then the 10 and then the 15. you still need all the parameters of the drivers before any plans can be made.

Where the horn is in the drawing is ear level when sat down, see photo on previous page. Would your suggestion to swap them still apply?

As for the driver specifications, I have got the two goodmans ones but my search for the EMI one keeps taking me to a dead end. If I can't find them on google, what chance do I have, or even other ak'ers? It looks like I'll have to get a speaker tester and find out. I really wanted to know what the specs were supposed to be.

 

[tensleep]

One thing you can do is build a box around the back of the horn - that way, the woofer can take full advantage of the enclosure volume. This would allow you to build a smaller cabinet. The midrange can also be covered by a box or some use a bowl - seriously. The horn doesn't really need to be covered at all. What you are trying to do is isolate the other drivers from the backwave of the woofer - if you think about it, the compression driver on the horn is already sealed.

When you calculate the volume, you must subract the volume of the drivers, and any bracing and damping as well. The math doesn't have to be exact, probably to the first decimal place in terms of the volume. I use a simple formula for calculating the volume of a cone for the two drivers. All you need is the radius and a good estimate of the depth.

 

[pingu_turbo]

Yesterday Dad came over and we had a serious man chat about these speakers. My first question was, what do you know about these emi drivers and the first thing he said was they are 50 watts rms. Great! His idea behind them was to have three equally powered drivers, which they are all 50 watts rms, in one cabinet. His other idea as to use the most efficient drivers he could find because he didn't have the money for a powerful amplifier, the goodmans audom 12p is 96db at 1 watt at 1 meter ffs!

He used to run them from a leak delta 70 amplifier rated at 30 watts ( which he still has ) and said that a big powerful amplifier would be wasted on these speakers because they were just too loud. The old leak was more than powerful enough at upper volumes.

Then I came to ask why build them? He said he wanted something with (his words) 'decent bass' none of the other speakers he had bought and tried and sold gave the feeling, punch and control over the lower tones that he wanted so he built these. They were not built from a kit or even plans, he sourced, planned and made them himself. Credit where it's due, he is a clever sod with stuff like this. Maths really isn't my thing!

I then moved onto the frequency response. Apparently somewhere he has the leaflet/manual that came with these drivers. I also showed him the PDF I had of the goodmans range of that time. He said from memory the emi 315 would go down to the very early 20hz. and with the right cabinet even lower. How true that is, it remains to be seen. But that is exactly what I want! I threatened to test them once the cabinets were made, he just smiled and said I would like them.

As it turns out the cabinet dimensions were spot on for the emi driver. The total for the old cabinet was 7cu'. Exactly what it should be. Dad had the goodmans audiom over cabineted because he didn't feel that 50 litres was enough. Lets be honest here 50litres is not a lot! Measuring the old cabinet he had them at 83 litres.

We both came to the conclusion that I could build in a false movable rear to the goodmans audiom chamber to try the 50 litre capacity and others.

Amazingly he chose his drivers so he could ' build each cabinet out of 1 sheet of 8x4 board '. Uni budget thinking I guess!

My other point was about the crossover, I said I felt that they were giving too much midrange to the goodmans audiom, he said that the three way crossover was hard enough to find at the time that would handle 50 watts per driver. Component stores were few and far between for building the correct crossover. Something I want to do.

I did mention about fitting in a smaller 6-8 inch driver for between the horn and goodmans audiom, he just smiled and said 'that's my boy'.

I know some of you may find this boring, but for me the whole story of how these speakers emerged was amazing. The logic behind them was so simple and worked. I feel even more inspired to get them going now!

 

[leesonic]

If you can find the Thiele-small parameters for these drivers, I'd gladly run them through my bass box software for you. This will tell you the optimum volume for the driver, and whether or not they should be ported or not. I'd hazard a guess you'd need some pretty big boxes for these.

Lee