Primus Mod

[Alex2507]

Now that everybody is over these, here's something that's been on my list for a while.

I yanked the drivers and everything else.











Then I cut the back off using a circular saw with a guide and a jig saw. I added a couple of former oak baseboards as braces on the baffle at the top and bottom of the woofers. The middle has an Infinity brace already. The hot glue on their braces was iffy at best and loose in one spot but that might have had something to do with the sledge.






The all-thread is being dry fitted. I need to figure out how to add braces and that roofing stuff without creating the death of a thousand cuts.





Here's the top and bottom braces.






I'll get around to trimming back the cans on the magnets and caulking them up. You can already see why they say I'm pretty good with the caulk.

 

[Adam]

Welcome back, man! Good to see you back on.

Opening a box, dry fitting, caulk...a worthy return, indeed.

 

[fuzz092888]

Its about time the monkey came back, and with a DIY project no less.

 

[Swerd]

Glad to see that you're back!

I wanted to find an appropriate DIY monkey picture , but the closest I found was someone building DIY monkey bars in his back yard. Not what I was looking for, but nice cross bracing.

 

[BoredSysAdmin]

Swerd, my Google-Fu mad skillz beat your google-fu skillz:

Here's a photo of DIY monkey:

p.s: DIY of Primus towers can't not to remind me of Chris's cement filled project. RIP Chris

 

[Swerd]

LOL . That's much better. I guess I was being too literal with my search terms.

 

[Rickster71]

Now that everybody is over these, here's something that's been on my list for a while.

I yanked the drivers and everything else.




Then I cut the back off using a circular saw with a guide and a jig saw. I added a couple of former oak baseboards as braces on the baffle at the top and bottom of the woofers. The middle has an Infinity brace already. The all-thread is being dry fitted. I need to figure out how to add braces and that roofing stuff without creating the death of a thous






I'll get around to trimming back the cans on the magnets and caulking them up. You can already see why they say I'm pretty good with the caulk.

Hey Alex it's good to see you back.
Where are the hockey pucks on the ends of the all thread?

 

[Alex2507]

Welcome back, man!

Its about time the monkey came back

Hey Alex it's good to see you back.

DIY of Primus towers can't not to remind me of Chris's cement filled project.

Thanks for the welcome.

The cement board lined business takes out enough volume to affect low frequency extension. I saw first hand what the results of that are on my first go round with my 360's. This time I'm planning on extending the rear of the cabinet by 3/4" to make up for the volume lost to bracing. My understanding is that insulation volume need only be factored in at like 10%.

I found that the 6" dimension of Peal & Seal fits on the side walls by the woofers. A length of 9" worked for me so I set up a little cutting jig and made up 24 pieces of that for double layering. I'll get some pic's of that later on.

BTW, this isn't about how anybody else should be doing this. This is about how much work is involved and how it's probably not worth it. I started making the cut to remove the back, inside the garage. About 6" into it I set up some horses outside and continued on. Nasty stuff. I remember Avaserfi talking about making cuts in a bathroom he had taped shut to contain the dust. A real f^%&in' trooper, that one.

What really led to this was cranking up some Metallica tune on the HPM-100's currently in Eddie's garage and thinking how much fun it was even with all the distortion. Then out of nowhere a pair of 362's popped up on CL. I snagged them for $175 ... plus I got his 606 Onk for another $50. I have a Panny BDP-60 that no longer plays BR and I had snagged a 27" tube TV from work a couple of years ago ... kind of like Adam's H/T from a few years ago but without a sub.

Anyway the point of this is to finally get this mod business done up the way I always wanted, get Eddie some better sound in the garage while he's still alive and to dissuade anybody else from ever saying that you can hammer out this project in a few hours. Yesterday the fofo got rotors, pads and rear shocks so no speaker love.

 

[Alex2507]

Here's how I cut up the roll of Peal&Seal.




Here's how I cut up the insulation.




These




got cut up with this:




Exposed rigid fiber glass got this:




Here's one that shows the xo reinstalled on the oak base.




Tight side:




Loose side (soon to be filled with caulk):




Kinda cool:




Way cool:

 

[Adam]

Loose side (soon to be filled with caulk)

Out of Context Man just ruptured something...

 

[Alex2507]

Next I'm cutting into my SongTowers.


... not.

I'm figuring out how to extend the cabinet and wondering if I should be allowing for more space due to the insulation. This piece is doubled up and at the bottom front of the cabinet. I guess that makes it 6-3/4"x3"x8". It was super tight going in ... Adam, no. The other two pieces directly behind the drivers are around 6-1/2"x10-1/2"x1-1/2".




A roll of Peal&Seal all cut up @ 9" gave me enough for three spots along the sides and the top all doubled up. The remnant was like 2"x6" and I split that to make 2"x3" pieces and stuck 'em to the bottom of the mid cup.
This is already a lot of work and the girl gets home tomorrow. She's been gone for a week and I had planned to drink and smoke cigarettes but thought I might have trouble dropping those habits upon her return. I been needin' a smoke real bad for a few days now. It's crazy but I have no idea how I managed to get out from under that.



The insulation came faced. I was going to use it for little sound panels around my center before I figured out to erase the YPAO curve assigned to it by the previous owner of my 663. The pieces behind the drivers got a very acoustically transparent fleece glued to it and that got turned to the inside of the cabinet. The doubled up stuff has their fabric on the outsides and I guess I have to treat that as acoustically transparent. I mean they were sound panels before sooooo .....

Ahhh ... to hell with it. I'm going to treat the insulation like it was almost nothing volume wise. I'll make a couple of oak frames to slip into the back of the cabinet and cap that, throw the drivers back in and then it's into Eddie's living room for a little A/B testing against Kurt's stock pair ... that part always scares me a little. What if they suck?

 

[Swerd]

… and then it's into Eddie's living room for a little A/B testing against Kurt's stock pair ... that part always scares me a little. What if they suck?

Or even worse, what if you can't hear any difference?

 

[Alex2507]

Or even worse, what if you can't hear any difference?

In which case I might just lie. I know that has happened untold times with a variety of tweaks but this ain't one a dem.

I actually tested out what my voice sounded like speaking into ... I'm terrible at this but here's the test. I had yanked the drivers in both cabinets. The speakers were laid out on their backs on that leveled out 4x8 sheet supported by the saw horses. So I removed the acoustical fluffy stuff from one speaker but not the other. I went back and forth speaking into a driver cut out "boom, boom, 1234, 1234". Their acoustical batting did bring down the echo some, not a lot but some. I found that I could adjust my voice to get some frequency resonating real good. If I weren't afraid of it being discovered that I didn't know what amplitude and decay time were, I would say that the amplitude and decay time were lower in the fluffy speaker. Plus I think the resonant frequency was lower in the fluffy speaker. Anyway Eddie conferred with everything I said because he just knows I'm smart as f^%&. Seriously, I went and got him to demonstrate what it was that I thought I was hearing. So ... science

Eddie and I both agreed with myself that the difference while noticeable was not huge. Infinity didn't waste their effort with that sound batting as has sometimes been suggested but the effort is minimal. After I had sealed up the back (as in all done ... mostly done) I tried that test again and it didn't sound at all like the former 362 box. The beauty of my own voice moved me to sing the Bosnian national anthem right then and there. My voice sounded more like my voice than let's say the way my voice would sound through one of those old Hollywood movie director megaphones. That's good right? That resonant frequency that was easily heard before seemed to be not only lower in amplitude and decay time but it seemed somehow further away. I didn't spend a lot of time monkeying around with that as I was tired, it was late and I wanted to get the drivers back in.

That's the bottoms turned toward each other. The bottom cleat is attached to floor at a fixed alignment point.



Here's how the frame slips in.



My cross braces line up with their cross braces.



I bought a 2-3/4" hole saw to make this part easy.

 

[Alex2507]

I said my braces liked up with their braces ...



The little notching action allowed me to reach further back into the existing cabinet for a better bite when screwing these together. Are there not teams of Primus owners across the country clearing their tables saws off? C'mon, you can do it. I could have done 90% of this mod with a chain saw. All you should need is that and a pair of pliers ... a couple of hours and bam, it'll sound better than an 802D.

 

[Swerd]

I actually tested out what my voice sounded like speaking into ... I'm terrible at this but here's the test. I had yanked the drivers in both cabinets. The speakers were laid out on their backs on that leveled out 4x8 sheet supported by the saw horses. So I removed the acoustical fluffy stuff from one speaker but not the other. I went back and forth speaking into a driver cut out "boom, boom, 1234, 1234". Their acoustical batting did bring down the echo some, not a lot but some. I found that I could adjust my voice to get some frequency resonating real good. If I weren't afraid of it being discovered that I didn't know what amplitude and decay time were, I would say that the amplitude and decay time were lower in the fluffy speaker. Plus I think the resonant frequency was lower in the fluffy speaker. Anyway Eddie conferred with everything I said because he just knows I'm smart as f^%&. Seriously, I went and got him to demonstrate what it was that I thought I was hearing. So ... science

Dennis Murphy says he does a similar voice test. On the Phil 3 cabinets he hollers something into the woofer hole and listens to how his voice sounds.

Of course all accomplished DIY builders know you can't just holler "boom, boom, 1234, 1234" and get good results . You have to yell "Thiele/Small" followed by "Linkwitz-Riley". Don't make the rookie mistake of saying "Thiele-Small" and "Linwitz/Riley". That's as bad as wiring the tweeter in opposite polarity.

Some claim that you have to say "Thiele/Small" followed by "Linkwitz-Riley" into the left speaker cabinet and "Linkwitz-Riley" followed by "Thiele/Small" into the right cabinet. But this hasn't been tested under double blind conditions and remains controversial. I leave that up to you .

Thanks for the photos of the oak bracing.

 

[Alex2507]

Dennis Murphy says he does a similar voice test. On the Phil 3 cabinets he hollers something into the woofer hole and listens to how his voice sounds.

Hmmm ... and I thought I had invented a new move.

I rethought my plan to trim those cans and caulk them up. I sort of ran out of gas on this. Besides, how much acoustical energy would it take to equal a good knuckle rap and just how much would one of those cans rattle? Enough to be heard over the music? After the drivers and crossover (which I'm not touching) I think the cabinet is the next big player in sound and I'm obviously done there since the drivers are back in.

The back will still have to come off. BTW, I painted the oak extension and screwed the back on. The back still has to come off for a final glue up. The back will get formica and the plywood end grain will get a trim piece that matches up esthetically with the stock Infinity round over. It'll look cool with a little reveal ... I promise. I didn't set out to destroy these things. Nor did I set out to have them looking unfinished.

Whole thing ...




Top ...





Middle ...





Bottom ...

 

[lsiberian]

This is coming along nicely.

 

[Alex2507]

Well I played 'em. Depending on the material they sounded great or dreadful. They could certainly take some wattage without coming apart. I cranked up the 606 until it said MAX and it sounded clean out in the yard. They're just too bright so instead of trying to figure out why and doing something about it I EQ'ed out the part I didn't like. It still sounded good in the yard cranked up to MAX. I have a couple of tricks up my sleeve to adjust the speaker later on but I feel like I got what I came for with this.

Walter, thanks for the EQ. It saved the day.

 

[Alex2507]

So I got this sort of set up to be able to do some listening tests. The player has analog going into an EQ before it hits the rec'r as DVD and it has fiber optic going into the rec'r as CD. I can go back and forth at will and if I hit l<< I guess it would replay what I just heard. Here's the set up:



The box that the rack is screwed to has the EQ in it. It's kinda cool that the front has a cover so the EQ settings don't get bumped. There's also a sorta dirty Carver amp (once again, thanks Walter) that I might try to drive that sub with. Eddie found it on a porch and the plate amp seems to be cooked but it's an A/D/S sub that's actually well put together.



I don't know what I was thinking but the middle section has some locked away Vb that I'll access by drilling a bunch of holes in the cross brace. That will allow for more bottom end on these things, right?



For the life of me I can't find the Infinity fluff from these speakers but I found some of the fluff from the first mod and a few other things that I want to stuff into the cabinet.

I'll get some pic's of this armoire I threw rack rails into. The microwave cart's days are numbered.

 

[Alex2507]

That chain is cemented into the slab. I think that's all that needs sayin'.