Dual RL-P18 LLT for my 2000 cu ft HT soon - Page 7 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #61 of 183 Old 06-03-07, 10:44 AM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

There are some studies that do objectively test panels... one good one is linked to in the thread below (which has some good waterfalls -- included in the thread below is an overlay of MDF & ply which shows why ply has an edge). Another is buried in an old AES article -- i have been tasked to try and find it (this one IIRC, clearly showed the superiority of particle board over MDF)

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What I would hope to find is if there are any differences.
Have a look at this thread so that you can refine your procedure to give it enuff resolution to detect the panel resonances at all... you will need to be able to isolate the front of the cab from the measured panels, and you will need to be able to display waterfalls at a minimum.

http://www.diyaudio.com/forums/showt...threadid=98834

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post #62 of 183 Old 06-03-07, 11:54 AM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

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you will need to be able to display waterfalls at a minimum.
Most people here use REW for mesurement software. It has waterfalls......

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post #63 of 183 Old 06-03-07, 01:30 PM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

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Most people here use REW for mesurement software. It has waterfalls......
Now that is cool... it will run on my Mac. I just got my Pismo fixed (it is a Frankenstien) and had planned on using Fuzzmeasure, but this is the 1st alternative to that that i have seen.

I'll have to dig into the help files, but can anyone tell me if in the waterfalls, you can specify msec or periods for the "time" axis?

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post #64 of 183 Old 06-03-07, 01:47 PM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

A waterfall plot will be useful, but before looking at it, I want to see which material will vibrate more, hence coupling the mic to the panel, and lets sound through, the reason for the close mic to the panel. I suspect if there is a difference in these tests, there will also be a difference in the waterfall plot.

I have not tried, but I have bought something for my next cabinets, and that is "Thick Grip" shelf liner, and HardiBacker tile backing board. The former is a foam waffle like shelf liner, the latter is a concrete like 1/4" board type material. My concept is to use contact cement to attach the shelf liner to the inside of the cabinet, and another coat of CC to attach the cement board to the shelf liner. this should add about 3/8" thickness to the cabinet wall. I think the best approach would be to not compress the foam by screwing, but I am not sure on this point.

At any rate we are drifting far afield from Blaser's intent to build a subwoofer.

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post #65 of 183 Old 06-03-07, 02:45 PM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

[/hijack on]

Quote:
but can anyone tell me if in the waterfalls, you can specify msec or periods for the "time" axis?
Yes - here's a pic showing the adjustments. All the screens are of course derived from the impulse response.

There are some issues with REW and MACs. JohnM (author) indicates he may have to supply a MAC-specific version eventually to get around the problems. The usual benefit of cross platform capability relies on the platform providers supporting it, but Apple has their own audio class library instead of using the existing JavaSound classes, and so some people report problems when using REW. Others are OK, so give it a try...... or come on over to Windows like the rest of us.............

Dual RL-P18 LLT for my 2000 cu ft HT soon-waterfall.jpg

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post #66 of 183 Old 06-03-07, 03:04 PM Thread Starter
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

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At any rate we are drifting far afield from Blaser's intent to build a subwoofer.

Paul
No Problem, feel free to have any constructive discussion. I only wish your tests were soon enough, I should be building these subs within 10 days approx.

By thye way I found 15mm plywood (7 ply BB I think), and it was not as expensive as I thought...If any benefit ever I would go with it.
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post #67 of 183 Old 06-03-07, 03:36 PM Thread Starter
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

I need your opinion Guys....would you go for a 16 Hz Tune with with a 10" port, no port compression ever and no need for a flare (a bit less wood also), or a 14 Hz tune but with only a practical 8" flared port? Is there any benefit on real material?

By the way, the use of a 10" port will not leave 10" everywhere around the port entrance and may probably lead to a lower tune. Any comments?

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post #68 of 183 Old 06-03-07, 03:51 PM Thread Starter
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

What's quite amazing is at time of thinking of going DYI, everything appeared to be very easy, and choices seemed obvious .... Now that I ordered and I am about to receive the equipments every small detail is very hard and time consuming to think about and I change my mind 5 times an hour

It is not as easy as I thought
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post #69 of 183 Old 06-03-07, 05:36 PM Thread Starter
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

By the way, here is a cross section photo of the 15 mm plywood I found here. Looks good enough?
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post #70 of 183 Old 06-03-07, 05:38 PM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

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[/hijack on]
...... or come on over to Windows like the rest of us.............
I am not going to downgrade to Windows, i have too much work to get done on my computer... I will thou be getting an Intel Mac sometime in the future and will be running either Parallels or Cross-over Mac (WINE) on it so that i can run Windows programs (that don't yet have Mac equivalents) and have as little as possible to do with Windows as i can...

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