New build for shop system

AngrySailor

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Yeah I’m still home. I guess she realized 20hr notice wasn’t going to work. Had to gear up the tractor for grass cutting, remove the snow attachments (of course it’s snowing rn). Also had to empty out the fridge, gave all my milk and stuff away now looks like I’ll be home a few more days damn it! Also there’s no leaving the ship once I arrive so I need to bring everything I’ll need/want for the duration of the trip. Stupid stuff like phone charger cords, toiletries, all the little stuff you think you might want in two months...

Checked the post office today. The WOPL parts are still in transit. Getting closer though, they’re in NB. Probably be here Monday they figure. I might have pissed off crewing by politely declining to travel so rushed, I might have time to work on them now... best part is they wanted me there as an extra Engineer, they’re not even short handed and couldn’t arrange this with a couple days notice! Wtf!
 

J!m

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Actually, it sounds an awful lot like where I work...

“Jim can you run this sample for me?”

“sure; why?”

“They fired Julio and I have to run his job so I can’t do the development sample.”

“ah, sounds like a Wednesday to me. “

“Thanks, Jim!”
 

nakdoc

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Does he sound like an angry sailor to you?
They may have had someone else cancel at the last minute. Here in the states I know some folks who are struggling with decisions whether to work or not. The cruise ships get all the press, but there must be ships asea right now with partially infected crew members. I've had to go without my office staff which causes me to run around like a stuck chicken when I get two customers and a phone call all at once. Losing trained people like Julio or my Helene shifts big burdens on those of us holding the fort.
 

AngrySailor

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Nah, not TOO angry about going to work really... Sure wish I didn't HAVE to though! Travel ALWAYS sucks no matter how smooth it goes, always a little depressing as the time to leave home gets closer too, especially when the nice weather is almost here. CoronAIDS is messing with crew schedules and travel also. The airports were empty, one of my flights had 5 passengers, the next less than 10. I do have to say that this company is one of the more organized outfits I've worked for but the others were complete cluster F*&ks so...

nak, we have been fortunate that there are no cases of coronAIDS in the fleet. There is no shore leave, provisions are handled with gloves and wiped down with cleaner as they come aboard, access to the ship by shore personnel is limited also. I have a couple weeks to go then heading home, short trip this time. Going to get them big azz cabinets put in place and wired, finish the 18" cabinets for the house then start into putting the WOPL goodies into Linda and Tim!
 

AngrySailor

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After building those big cabinets this should be a breeze. The house 18’s just need a sand and final coat of paint. The big cabinets are ready to install. I’ll use my friends forklift to put them on the shelf. To me, the WOPL pprojects will require the most work as I’m a n00b...
 

AngrySailor

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And could also provide the most frustration..
Of that, I have no doubt. I received all the documents/instructions and printed them out. Looking forward to tackling the projects. Probably build the driver board for Tim first as it’s a working amp rn just has DC offset a touch high.
 

AngrySailor

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That’s the plan. The stuff looks mint, über high quality. I can’t wait to get into assembly and hopefully I do them justice.
 

roccus

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Just landed home. Where to start... so far I’m impressed with these el-cheapo speakers. Opened one up, looks pretty good for $79 USD delivered. 3” voice coils, decent finish. They don’t “look” cheap and if they perform like the 12” I used for car subs for a friend they should do well. They’re only running 20~100/150hz. There’s still two more in the house... couch was full I guess...
I am getting ready to start building my subs... I was considering the 18" drivers you used here..... how are they working out? Do you have a model number for the ones you used??
 

AngrySailor

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I’ve been away at work and only thrashed on them a week maybe? I had no problems in that time and was happy with things over all.

Model RVW1800P*
* is either 4 or 8 depending on VC resistance you want. 6BC3C565-51CA-4F5C-B1CB-8D11D10679BC.png
 
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AngrySailor

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I’ve only run mine on one of my big amps so far which gave me 400w/driver. I pushed the amp till clip lights were just blinking for hours. You could just feel the dust caps were above ambient room temp. Magnets were negligible for heat. With both amps wired in, I will have 600w/driver available. I don’t see that this will be a problem but their 1800w program rating is probably on the “optimistic” side. What will you be driving them with?

Oh, keep in mind that the dust caps are not oriented to the mounting holes so you have to skew the pattern individually if you want the lettering level!
 

roccus

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Right now I am running a Crown CL1 275W per channerl @ 8ohm for my subs but thinking I will eventually replace that amp with a Carver pm 1.5 that is 450W per channel @ 8ohm.... You used 3/4 mfd for your cabs?? I was looking at best way to do the circle cut out for the speaker. I read that the problem with a router bit on thick mfd is the bit dulls real fast. I plan to cut one so the woofer will mount to it then cut another one a bit larger glue it to the the panel with the smaller hole so the woofer will look recessed so that will be 4 large holes all together for the 2 cabs. Not sure the cost of a router bit to do this but I assume up near $30 so it could get pricey if I have to buy 3 or 4 bits....
 

AngrySailor

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Right now I am running a Crown CL1 275W per channerl @ 8ohm for my subs but thinking I will eventually replace that amp with a Carver pm 1.5 that is 450W per channel @ 8ohm.... You used 3/4 mfd for your cabs?? I was looking at best way to do the circle cut out for the speaker. I read that the problem with a router bit on thick mfd is the bit dulls real fast. I plan to cut one so the woofer will mount to it then cut another one a bit larger glue it to the the panel with the smaller hole so the woofer will look recessed so that will be 4 large holes all together for the 2 cabs. Not sure the cost of a router bit to do this but I assume up near $30 so it could get pricey if I have to buy 3 or 4 bits....
Yes 3/4” MDF.

I used a router for these cabinets although I did use a jig saw for the previous 18” build. I cut all the driver holes (8) and all the port holes (16) with one carbide tipped bit. I used the protective 1/4” sheet that came with my lift of MDF (ask the hardware store for a piece from scrap maybe?) and made a template out of it. It had a hole that was large enough that the router sat inside and the body of the router ran around the inside of that hole, cutting the required diameter for the speaker. For the ports I used a circle cutting attachment. You can make one from that piece of 1/4” scrap. If you make your own circle cutter, you can make it big enough to do the 18” holes. I did it this way as I also used that template for my screw holes.

I clamped the face boards to an old wooden door as a sacrificial work bench, then screwed the soon to be cut out circle down so it wouldn’t move when separated, run the router around plunging about 1/4” deep each time. Then I removed the two screws holding the off cut and was Left with a nice hole.

The jig saw worked ok, not as nice of a circle but I’m covering that with trim rings... I did the low-max build as you plan to with the double face boards with a jig saw. Used a couple blades and took a couple hours including breaks for “refreshments” which might be why the holes weren’t as round as the router/jig method.

The hardest part of the double face boards (I was a dummy) was the port holes. I used a hole saw through both layers. Had to peck at it and blow the cut clear with air. If I did it again I would cut an oversized hole in the inner board then cut the hole in the face board before laminating them. Use lots of glue and spread it around so you have no voids. Use lots of screws on the lamination at least until it dries.

I used plain old cardboard sono tube for port material on the big build, and 4” sewer pipe (PVC) for the low max. Either works fine. Use a fine hacksaw to cut the sono tube or you’ll fray the cardboard. That’s no big deal though just rub some wood glue with a rag around he cuts to fix that then sand or 1/4 round the edge at the face board.

You probably want a 6” ID port if you can swing it. Usually 1/3 of the speaker diameter is a good rule of thumb to keep port air velocity low enough to not chuff but not so big it has unwanted resonances. A larger port has to be longer in length for the same tuning so you might run into trouble if rhenpirt wont fit in the box. Remember that the driver displacement, bracing and the volume occupied by the port all come off your Vb for calculations.

These speakers are fairly stiff and I found it hard to visually see resonance when testing the cabinets, pick up a shunt resistor and use your MM to check resonance frequency before you glue the ports in for good.

Good luck!
 

AngrySailor

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Put approximately 5 to 10 ohm resistor in series with the speaker. DMM across the resistor set to voltage AC. Use a signal generator connected to your amplifier and turn the gain up until you have a few volts across the resistor (watch the wattage rating of your resistor).

As you sweep the frequency the voltage will be at its LOWEST for resonance of a SEALED box

And it’s HIGHEST voltage for the resonance of a PORTED box.

Ported boxes will have multiple resonant frequencies which are harmonics or octaves of the tuning frequency. The speaker cone should visually travel its minimal amount at resonance as confirmation though this is hard to see with higher power/stiffly suspended drivers which is why I used the DMM.
 
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