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post #1 of 7 Old 03-01-15, 11:23 AM Thread Starter
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Peter Stoffregen
 
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Home Built Cinema Subs

These are my version of the JBL theatre subs. Dimensions are the same but the cabinets are 1" mdf instead of 3/4" particle board, and more extensively braced (with oak). Drivers are 18" RCF, almost one quarter the cost, but unfortunately, 2.5 db less efficient.
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post #2 of 7 Old 03-01-15, 04:44 PM
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Re: Home Built Cinema Subs

What size is your port? And what tweeters are you using in your line array?

"Music is the space between the notes"
“[T]o talk well and eloquently is a very great art, but that an equally great one is to know the right moment to stop.”
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post #3 of 7 Old 03-02-15, 07:53 AM Thread Starter
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Re: Home Built Cinema Subs

The Port (duct) size is 12" L x 6 & 1/2" inside diameter. Lowest of the two resonance points is 19 Hz with the RCF LF18X401 driver. The duct protrudes 2" from front face for at least 2 reasons; to avoid choking it against the back of the cabinet, and to reduce static pressure changes in the cabinet with extended bass notes, caused by duct terminated in baffle at one end and free hanging at the other.
The tweeters are Dayton Audio PT2C-8 (planars). I am very pleased with the sound of these units, although they are made in China and still about $100 each (Canadian). With 8 units per side times 80 watts each, I have reduced the cross-over point to 2 kHz, and have no problems even with levels approaching 120 db peak at 10 feet.
I have over-laped the mid drivers two keep the centre to centre distance minimum, to allow the "line array" effect up to 2 kHz
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post #4 of 7 Old 03-02-15, 08:35 AM
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Thumbs up Re: Home Built Cinema Subs

Looks good Peter, how does it sound?
Do any testing?

Buying more cheap stuff to get better sound is like challenging a dragon with a pocket knife.
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post #5 of 7 Old 03-02-15, 10:17 AM Thread Starter
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Re: Home Built Cinema Subs

I have done considerable testing ( port tuning modes, REW, my cheap DOD RTA, efficiency, etc) before I painted them and made the grills from the safety mesh from the kid's trampoline, (sound before safety!). I am incredibly pleased. We watched a movie last night; ("Hereafter"), I thought I would be sweeping up my own window glass after the tsunami scene. I am still playing with cross-over points, both low/mid and mid/high, but those are other long stories. Frequency response is better than expected, for some reason, I could not get the lower resonance ABOVE 19 Hz, but it is great for blowing out candles and rearranging the furniture. My listening room has 2 x 12 floor joists, two layers of plywood sub floor, glued, and these speakers make it feel like rubber. Amazing solid bass without sounding boomy. I will post REW graphs etc., when I have more time to tinker.
My only concern is that my Phase Linear 700 is being driven a little too hard, IMHO, to get the levels I want on occasion. The drivers are rated at 1500 W 'program' and 3000 W peak, with a 50 mm max cone excursion (P to P). I am looking for a bigger amp for the LF's, but don't like the idea of class D amps in a HIFI system. I could go for class H, but any opinions on this would be welcome.
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post #6 of 7 Old 03-02-15, 04:57 PM
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Re: Home Built Cinema Subs

That's a beast...I think you need a matching 1!

Buying more cheap stuff to get better sound is like challenging a dragon with a pocket knife.
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post #7 of 7 Old 03-03-15, 08:43 AM
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Re: Home Built Cinema Subs

I like it. Great job. I would love to hear them. My opinion is that class D is just fine for subs. I do not think you would be able to tell the difference from class d to H
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