Monkey see, monkey do... two RL-P18s for me too! - Page 4 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #31 of 151 Old 10-11-07, 02:34 PM
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Re: Monkey see, monkey do... two RL-P18s for me too!

I like that sketching program... nice...
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post #32 of 151 Old 10-11-07, 07:14 PM
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Re: Monkey see, monkey do... two RL-P18s for me too!

Ya those sketches look sweet! Does Sketchup calculate the volume?

Edit: Nevermind just read the last line of your post


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post #33 of 151 Old 10-11-07, 11:30 PM
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Re: Monkey see, monkey do... two RL-P18s for me too!

I'd have to believe window braces are the most efficient use of bracing if trying to minimize displaced volume. Braces with holes cut in them aren't efficient uses of space and add a lot of unnecessary work.

Not having at least 8" of clearance from the port opening is definitely a problem you should concern yourself with, as it can result in early onset of compression. How much clearance will you have as it is designed now?


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post #34 of 151 Old 10-12-07, 11:35 AM Thread Starter
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Re: Monkey see, monkey do... two RL-P18s for me too!

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I'd have to believe window braces are the most efficient use of bracing if trying to minimize displaced volume. Braces with holes cut in them aren't efficient uses of space and add a lot of unnecessary work.
Do you have a link or pic of what you would consider ideal/optimized window bracing? If I understand you correctly, I could draw up another model and compare the two. Either way, the large (and thin) port tube needs to be supported by the braces and that requires a significant amount of material.

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Not having at least 8" of clearance from the port opening is definitely a problem you should concern yourself with, as it can result in early onset of compression. How much clearance will you have as it is designed now?
The outer edge of the port tune is 5 inches from the interior rear wall. It's about the same distance from the back of the driver. There is 11.5 inches of space from the end of the port tube to the side wall that it "points" at.





On the whole, there is a lot of space around the end of the port tube. However, if you think I should move it closer to the driver and/or center it in the box (front-to-back), I will consider that.

Thanks.

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post #35 of 151 Old 10-12-07, 12:11 PM Thread Starter
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Re: Monkey see, monkey do... two RL-P18s for me too!

Steve,

I thought about for a while and finally came to the conclusion... CIRCLES RULE! Here's my latest design.

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post #36 of 151 Old 10-12-07, 03:13 PM Thread Starter
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Re: Monkey see, monkey do... two RL-P18s for me too!

The brace pictured below is within 1% of the volume of the "rib" style brace used in the current box design. The "border" of the brace is 2 inches wide. Also note the port tube has been moved 2 inches toward the front of the cabinet, closer to center.



If I add 2" wide horizontal supports from the circle to the edges, it would consume about 10% more space than the large-circle "rib" style brace currently employed. That would probably make for a stronger brace but I'm not sure it is worth the space penalty. Perhaps reducing the border or "stick" width to 1.75" would hit the right balance.

Last edited by Bradley; 10-12-07 at 03:23 PM.
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post #37 of 151 Old 10-12-07, 04:53 PM
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Re: Monkey see, monkey do... two RL-P18s for me too!

I have to agree that when tuning so low, a single 8" port/driver is more than sufficient on real program material. dual 6" ports will only add complexity in the design/construction while there will be no noticeable benefit. I have hit 125 db from a single driver at WOW and did not notice any bad thing from the port...

I would only advise to use the most power you can. I am powering my drivers with dual 2000 W RMS (4.5% THD) amps, and I really feel that these drivers are rated a very conservative 1000 W.

Congratulations for this project in advance...

ASME AI
Yamaha RX-V2500, Wharfedale Diamond 9.6 Fronts, Wharfedale Diamond CM Center, Diamond DFS Surround and rear, Behringer FBQ 2496, Dual RL-P18s 625L LLTs, Dual TA-2400 Pro (2 * 2000 W Amp), Samsung HD870 DVD player, Carada BW 16:9 106" screen, Epson TW-2000, 60 Gb PS3
Important HT proverbs:
- "You can never have too much headroom" (talking about bass)
- "you can never have too big a screen" (talking about still pictures)


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post #38 of 151 Old 10-12-07, 07:47 PM Thread Starter
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Re: Monkey see, monkey do... two RL-P18s for me too!

Thanks, Blaser.

Having spent many, many hours already on the design with a single 8" port, I really don't think dual six inch ports would be much more difficult. The two smaller ports would actually integrate better into the rear half of the enclosure space, remaining almost one port diameter away from any of the walls and the driver.

My only concern with using more power would be cone excursion, possibly bottoming out the driver, especially with the 14.5 Hz tune. I'm going to start out with 500-600 watts mostly because that's what the amplifiers I already have sitting here will do.

Hoping to finish up the design tonight and start cutting MDF tomorrow!
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post #39 of 151 Old 10-12-07, 08:50 PM
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Re: Monkey see, monkey do... two RL-P18s for me too!

Yes, move the port closer to the driver so that you can have 8" clearance from the side wall.


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post #40 of 151 Old 10-12-07, 09:02 PM
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Re: Monkey see, monkey do... two RL-P18s for me too!

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My only concern with using more power would be cone excursion, possibly bottoming out the driver, especially with the 14.5 Hz tune. I'm going to start out with 500-600 watts mostly because that's what the amplifiers I already have sitting here will do.
Be carefull if you're using less power than the drivers are rated to handle. Running a clipped signal into the drivers will burn them up very fast.


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