[bballer123]

Hello there,

I am new to the shack, but just browsing around it seems to be a GREAT place with LOTS of resources. Hope you guys could help me out a little bit. I have an RLP-12 D2 that I want to put to good use. I was originally thinking of a sealed enclosure (but am open to other ideas) that would not exceed a couple cubic feet. My goal is to have it primarily for home audio and have a solid output down into the 20/25hz range. Anything below that is just fun! I will be using bookshelves/monitors (whatever you want to call them) that provide solid output to about 45 hertz. My room is 16x14x8.

For an amp, I am also open for suggestions. I was originally thinking of bridging an EP2500 (seems popular and reliable) in order to get a good 4 ohm output. My budget is about $100-150 excluding materials and the amp. I think that is pretty feasible. Looking forward to some feedback/guidance. Thanks you guys!

-Matt

 

[Mike P.]

A RLP-12 D2 with solid output down into the 20/25hz range in a a couple cubic feet is doable with the new Creative Sound Solutions Passive Radiators. The sub models well in 2 cu.ft. tuned to 21 hz. With 1000 watts input SpL is 109 db at 20 hz, plus room gain.

If you go with the EP2500 you would need a high pass filter to protect the sub and PR's from over excursion. The Rechhorn B1 is about $100 and can also boost the input voltage of the Ep2500 id that is an issue with your receiver. The modeling is with a HPF at 16 hz.

a 17.5 inch cube would be the size needed for the sub. The PR's are $67 each plus shipping.

http://www.creativesound.ca/details.php?model=APR12

The advantage of these PR's is you can change the tuning externally by removing the center cap and adding the supplied washers. It doesn't get any easier. Post #16 of my build thread shows how.

http://www.hometheatershack.com/for...1-creative-sound-solutions-sdx10-sub-kit.html

 

[bballer123]

Thanks Mike! I knew joining this board would be great. I just have a few questions.

The internal volume would be a 17.5 cube, correct?
How many grams would need to be added to each passive radiator? Would it possible to use one PR to cut down on costs?

For a HPF, as well as crossover, (integrated amp is all analogue and just has a straight pre-out, no filtering) are there are viable options that are computer based? I assume a lot more options would be available with a software based instead of hardware based solution. Any time I will be listening with the sub, I will be running music from my computer. I have a mac, so I'm sure that limits it also. Thanks again!

-Matt

 

[Mike P.]

The 17.5" cube is external measurement. The added mass is 765 grams to each PR which is 17 washers. The Pr excursion graph shows both PR's are at their limits with 1000 watts, one PR is not an option.
I'm not familiar with computer audio software, you'll have to do some research. It would be great if there was a software solution for you application, I assume it would be a lot cheaper. Hmmm. Now you're giving me ideas!

 

[bballer123]

OK. That is making some more sense conceptually as well as on paper. For the Reckhorn, it shows the B1 is 230v but in the manual it shows it can function on both 230/110v. Things might be different for you up in Canada...I don't know. That sounds really good though.

Mike, remind me again what the benefits of the PR are vs. ported. I am just strugging with cost because When added up: Reckhorn $100, EP2500 $300, PRs $150, Materials $50. $600 for a build that involves using a nice driver I already have. Am I being unrealistic, or is there another viable option? I noticed your kit you built and that seems nice. That was a bit cheaper. Thanks.

-Matt

 

[Mike P.]

PR's allow you to tune small enclosures to a low frequency. In small enclosures ports can get long. Doing a cheaper build with the RL-p12 is doable with a little more work. In a 18.5 inch (external measurement) cube tuned to 22 hz with a slot port that you build yourself. The slot port would be 3" high by 5" wide and 38 inches long. Since the internal dimensions are 17 inches, the port would go along the bottom of the cabinet, up the back wall and part way across the top for a final length of 38 inches. Power could be a Dayton 540 watt amp that has a HPF built in at 18 hz and you'd get 105 db at 20 hz, plus room gain. The amp is on sale for $250.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-806

If you can build a box you can build a slot port for a final price that's a whole lot cheaper. It all depends what you want to do.

 

[brandonnash]

A ported box will reduce your overall cost, but it would increase the size of the enclosure, probably by a good amount. I don't have the specs of the SS 12 that you have in front of me, but I would imagine it would take a box of at least 8 cubic feet internally. You would still need a HPF.

 

[bballer123]

Hey guys. I was messing around with winisd on my older PC but did not have enough time to really get into things. Hopefully that will come over the weekend. Browsing around, wondering about port noise, I stumbled upon a nice excel program called Unibox. Has anybody used this? Seems like a decent program but it (and I) could be way off. It is saying that I could achieve 109db @ 20hz. The enclosure is 2.3 ft3 tuned to 21.5hz with a 29" long, 4" diameter flared port. The power is 560w. The overall FS looks pretty smooth.

This would be awesome if this is true. I would be willing to sacrifice the output if it meant better sound quality at this point. I am throwing ideas out there hoping they do not sound ridiculous. Again, thanks to everyone.

-Matt

 

[Mike P.]

The box size and tuning is about the same as what I was referring to in post #6, but your air speed is off. One 4 inch port would have an air speed of 42 m/s, if you use the Dayton 540 watt plate amp with a HPF at 18 hz the air speed drops to 34 m/s which is still high and the reason I suggested a slot port.

 

[bballer123]

OK. That makes sense. Bracing? Should I model it after your build? Is that a safe bet? If I do add it, I would obviously need to take that displacement into consideration. Thanks

-Matt

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