Need Help for DIY Sub (Dayton Audio HO Reference 18") - Page 3 - AVS Forum
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post #61 of 75 Old 04-17-2013, 10:41 AM
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Originally Posted by fbov View Post

You're calculating for the 2nd harmonic directly as the onset of HD-driven standing waves. As you said: "The highest one. 1/4 wavelength at 80Hz is 3.5 feet..."

I was thinking along siimilar lines, but discounted 2nd in favor of 3rd, thinking it's easier to fit a higher harmonic. The problem I had, looking at Ricci's distortion data, was the low level of 3rd harmonic... below 1% by 40Hz in both sealed and tuned alignments and 120Hz still too low. There is no shortage of 2nd harmonic... both alignments are ~5% well past a normal sub LP cut-off.
(Note this is all at a 113dB output level from a TC Sounds LMSR-12, save for the horn, which has less distortion at 6dB higher SPL.)

5% is -30dB, and it's quite possible for a standing wave resonance to build that high... talk about a localizable sub!

Thanks for the inisight, Bill.

HAve fun,
Frank
A good idea before mounting the driver is to stick your head inside the cab and hum. Sweep the pitch of your hum and you will hear resonance. Chances are that resonance is way above the sub passband, but not so high above it that it won't get excited by harmonic content. You won't want to hear that resonance, and it's so easy to kill it with some damping that there's no logic behind not damping it. I've only found one instance where damping isn't a good idea, and that's with a folded horn, because the horn filters out above bandwidth content so well. But even a tapped horn benefits from some damping. Danley does it with the DTS, and I'm sure that decision wasn't come at without a good reason.

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post #62 of 75 Old 04-18-2013, 08:29 AM - Thread Starter
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What gauge wire for feeding 850 watts from amp to sub? Should I use speakon panel mount on the sub and internally wire the sub to the panel mount and then through spekon plug to amp OR speakon on the amp and bare wire directly to the sub by drilling a hole in the cab?

I have had better results with the direct feed. Anyone having any experience with feeding the power both ways to the sub, pls chime in. Thanx

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post #63 of 75 Old 04-18-2013, 10:02 AM - Thread Starter
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anyone??

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post #64 of 75 Old 04-18-2013, 10:10 AM
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10 (overkill) or 12 gauge. The other question is really personal preference. I've just used normal speaker terminals on my subs. Speakon on the amp to normal terminals on the subs.
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post #65 of 75 Old 04-18-2013, 10:26 AM - Thread Starter
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and how much power are you feeding your sub using speaker terminals?

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post #66 of 75 Old 04-18-2013, 10:47 AM
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Depends how long your cable is, but 12 gauge should suffice.

10' of 12 gauge = 0.016 ohms
Or, with a 4 ohm load, that would consume 3.4 watts, not a huge deal.
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post #67 of 75 Old 04-18-2013, 11:15 AM - Thread Starter
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Well the straight line distance is 10 feet from the amp to the sub, but cable comes in the way. So, I have to run it along the wall, then it climbs up the door goes around it and then snakes around a couple of bends around the wall. This length comes up to 30 feet.

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post #68 of 75 Old 04-18-2013, 11:25 AM
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I stole this link from Bill Fitzmaurice , but it will show what your db loss would be. youll be surprised how small of wire you can get away with

http://www.bcae1.com/images/swfs/speakerwireselectorassistant.swf

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post #69 of 75 Old 04-18-2013, 11:36 AM - Thread Starter
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That calculator is for car audio. Does the same apply for home audio as well?

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post #70 of 75 Old 04-18-2013, 11:43 AM
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Quote:
Originally Posted by braveheart123 View Post

That calculator is for car audio. Does the same apply for home audio as well?

is there a difference between car wire and home wire ? wink.gif

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post #71 of 75 Old 04-18-2013, 11:55 AM - Thread Starter
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Quote:
is there a difference between car wire and home wire ?

Got it, thanx.....smile.gif

One more thing....while you were busy replying to my post, I was checking my 30 feet long XLR cable between BFD and iNuke through digital multimeter set to the lowest 200 ohms setting. Here are the results;

+ = 33 ohms eek.gif
- = 33 ohms eek.gif
ground = 36 ohms eek.gif

Got this cable locally made and i was hearing a loud hum from the sub even when there was no signal. I think it should be no resistance coz it's a balanced cable. is the cable bad??

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post #72 of 75 Old 04-18-2013, 12:59 PM
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Quote:
Originally Posted by braveheart123 View Post

and how much power are you feeding your sub using speaker terminals?


I use these terminals: Dayton Audio BPA-38G HD , which are solid metal and state that they can handle up to 8 gauge wire. To answer your question directly: 500-800 watts. But to go a little further: your wire will melt before these terminals fail. They can realistically handle just about anything.
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post #73 of 75 Old 04-19-2013, 07:52 AM
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Quote:
Originally Posted by braveheart123 View Post

Got it, thanx.....smile.gif

One more thing....while you were busy replying to my post, I was checking my 30 feet long XLR cable ...I think it should be no resistance coz it's a balanced cable. is the cable bad??
Perhaps, but not likely. The XLR cable is not a speaker cable...
- it carries millivolts, not volts, and microamps, not amps
- it connects high-iimpedence devices, like 10K, not 4 ohm
- it's designed for noise resistance, separating ground from shield, not power transmission

Hum is what it should be better at than a normal unbalanced RCA-terminated cable... but not all hum is from the cable.

HAve fun,
Frank
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post #74 of 75 Old 04-19-2013, 10:39 AM - Thread Starter
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Quote:
but not all hum is from the cable.
I resoldered all three connections of xlr connectors on either ends and it reduced the hum by at least 50%. But the web interface of iNuke 6000 DSP still shows -52dB on both the input and output signal level meters even when there is no signal. I switched off the AVR but BFD was on. Then I checked the BFD to isolate the source of noise. I accidentally touched the body and felt the shock. Do u think this is the source of noise and hum?? I think BFD body is no grounded.

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The best EQ is no EQ ...

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Dual Dayton RSS390HO-4 Reference 15 Build For HT

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post #75 of 75 Old 04-23-2013, 10:44 AM - Thread Starter
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Starting new thread........"Dual Ported Dayton Audio RSS390HO-4 Reference 15 Build for HT".........This thread took a u turn on HO 18 coz of unavailability, hence the thought to start new one with its own title.

History is written by those who have hanged heroes ...

The best EQ is no EQ ...

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Dual Dayton RSS390HO-4 Reference 15 Build For HT

Main System: Klipsch RF-82 II, Klipsch RC-62 II, RS-52 II, Onkyo 5010, Rythmik FV15HP, PSB S300
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