Iowa DIY project

Tom_S

It's been a very busy few months at work, but quieting down a little now. So I've been working hard the past week to get my speakers built for this year's big party in Ankeny.

Made quite a few holes today! 

That made a pile of shavings!


We're getting closer to making some noise, but still some cutting & drilling to be done before I can start measuring. Hopefully that will happen this weekend. I'm not all that confident about the RST28F being up to task, but you never know until you try. 

4thtry

Cool project.  Look forward to hearing these in a few weeks. 

Tom_S

I'm looking forward to seeing you Bill! These may be naked and might not sound all that great, but they'll be there even if they're held together with clamps & duct tape!

Tom_S

More progress this weekend - the baffles are 1.5" thick. I'm hoping this will be enough breathing room for the woofer. 


I wanted to radius the tops of the baffles, so I had to make a quick jig - 



The tweeter cutout with the toggle clamp delaminated, so I had to improvise for the second baffle.



I have to decide soon - roundover or chamfer?

Tom_S

And the old adage is true - you can never have enough clamps! I picked up a bunch of the cheap Harbor Freight 18" clamps Saturday morning. They are the blue ones. Not the strongest or smoothest operating, but if you don't need a ton of clamps force you can't go wrong for less than $6.00 each.

6thplanet

Any reason for the space between the tweeter and woofer? I always put them as close together as possible.

hifiside

Tom_S said:

And the old adage is true - you can never have enough clamps! I picked up a bunch of the cheap Harbor Freight 18" clamps Saturday morning. They are the blue ones. Not the strongest or smoothest operating, but if you don't need a ton of clamps force you can't go wrong for less than $6.00 each.

I’d rather have 20 “ok” clamps over 1 great one.😁

PWRRYD

I have about 40 "ok" clamps 

jhollander

PWRRYD said:

I have about 40 "ok" clamps 

OK=Harbor Freight

Tom_S

6thplanet said:

Any reason for the space between the tweeter and woofer? I always put them as close together as possible.

I wouldn't normally have this much room between them. But I need to be sure there is a good flat area above the woofer since the tweeter is going to be hanging out above the top of the cabinet on this one. 

Tom_S

PWRRYD said:

I have about 40 "ok" clamps 

I have a stash of super cheap Chinese 36 inchers that I bought decades ago at some five and dime store. I don't use them unless I need longer clamps. They leave a lot to be desired - not milled flat and really bow when any pressure is applied. But they did the job (just barely) when I was doing more traditional wood working in a previous life.

6thplanet

Oh, so the woofer is in the box and the tweeter is above, "open baffle". Pic makes more sense now, thought the baffle was just sitting that way for picture purposes. I dig it !

Tom_S

I'm a bit behind schedule, too many other things going on. But I think I'll still make it by the 19th. I installed the binding posts & wire, then lined the box with Noico and some blue fluffy stuff before gluing the front on.




The front is sloped at 5 degrees. I used the cutoffs from the side panels to make a quick angle jig for my crosscut sled. That made trimming and sanding the top & bottom of the face pretty easy.



I routed a 6" hole in the top of the face so I could hot glue some temporary wedges underneath in the corners. Zipped the router around the inside edge and I now have ledges for T-nuts to hold the baffle on. That hot glue is strong stuff. It took some effort with a chisel and hammer to pry two of those wedges loose.



I just need to pick up some dowel centers from Menards tomorrow (thanks for that idea Javad!), drill all the holes, and hopefully I can start measuring soon. 

Tom_S

As many of you know, I did get these hacked together in raw mdf for Ankeny. These sound good enough to warrant some veneer & paint - maybe even a nice hardwood baffle. I will build something to get them up 16 inches off the floor - still pondering that.

Thanks to Craig & Scott for allowing me to use their speakers as stands on Friday & Saturday. They sounded much better at that height. The cap switch mid-stream on Sat was an experiment. Simulation showed flatter response that way, but that was only using the on-axis measurements I had to work with. Now I have another aspect to study up on for the next design.

I'm quite pleased with these Rival 7" woofers, especially at the sale price I paid. My original plan was to use an SB tweeter, but Javad had his Rival/SB combo for the 5 part challenge that I thought would be at Iowa, so I grabbed the Dayton RST28F off my shelf just to be different. I never worked with the original RS tweeters, but these had a rising response that needed tamped down. A simple shunt RC worked pretty well. I didn't try a small series inductor - I have more caps than coils in my stash. I was originally shooting for an LR4 at 1400Hz...but it ended up being at 1250Hz in the final design. I have not heard the tweeter complain, but I have not pushed these to the Rival's x-max and probably never will.

Things I learned on this project - I made the mistake taking my driver measurements with these up on 16" stands. That sure changed the response when they are sitting on the floor. The 5 degree tilt of the baffles really does nothing to help in that area. It's just too shallow at a typical home listening distance. That and the baffle shape were an aesthetic choice. But I did wonder if the truncation of the baffle may help reduce some diffraction irregularities. This project was so rushed that I didn't even have time to round over the baffle edges. I'll have to take them apart, run them through the router table and measure again to see if that smooths things even further. I do have a 3k valley that I couldn't seem to fill in. I'll have to play around in The Edge to see if moving the tweeter fills that in.

I'll post the schematic & squiggly lines tonight or tomorrow.