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Forum: Subwoofers, Bass, and Transducers   12-20-2014, 10:21 AM
Replies: 9
Views: 106
Posted By Bill Fitzmaurice
How do you match the power level when the input...

How do you match the power level when the input voltage is an unknown? And how do you account for amplifier headroom? Any well designed sub will have an amp with sufficient control over its input...
Forum: Subwoofers, Bass, and Transducers   12-19-2014, 08:56 PM
Replies: 9
Views: 106
Posted By Bill Fitzmaurice
Any sub will bottom out if it's driven beyond the...

Any sub will bottom out if it's driven beyond the driver's excursion capability.
However:

That probably indicates a bad volume pot. Instead of regulating the volume it may be either full off or...
Forum: DIY Speakers and Subs   12-19-2014, 05:22 PM
Replies: 64
Views: 703
Posted By Bill Fitzmaurice
+1. I've already posted how to do so, at least...

+1. I've already posted how to do so, at least twice. ;)
Forum: Subwoofers, Bass, and Transducers   12-19-2014, 03:21 PM
Replies: 3
Views: 49
Posted By Bill Fitzmaurice
There can't be a ground loop unless there are two...

There can't be a ground loop unless there are two or more connections to ground, typically via the AC cord and the interconnect. Since you have hum with only the AC plugged in the source of the noise...
Forum: Speakers   12-19-2014, 03:12 PM
Replies: 110
Views: 6,618
Posted By Bill Fitzmaurice
http://www.youtube.com/watch?v=FdghRwWfaOQ&feature...

http://www.youtube.com/watch?v=FdghRwWfaOQ&feature=related
Forum: DIY Speakers and Subs   12-19-2014, 01:29 PM
Replies: 64
Views: 703
Posted By Bill Fitzmaurice
Not much, you can get that same result with a...

Not much, you can get that same result with a variety of tunings, depending on the particular driver specs and cab size. For that matter you could see that result from a sealed alignment or horn. If...
Forum: DIY Speakers and Subs   12-19-2014, 10:17 AM
Replies: 19
Views: 338
Posted By Bill Fitzmaurice
So is the current draw of the amp. Simply...

So is the current draw of the amp. Simply plugging the amp into a circuit that you've verified is not on the same circuit would probably reveal if that's the problem.
Forum: DIY Speakers and Subs   12-19-2014, 10:13 AM
Replies: 439
Views: 10,107
Posted By Bill Fitzmaurice
What's incorrect? Dual opposed keeps subs from...

What's incorrect? Dual opposed keeps subs from dancing at high levels. It doesn't affect vibration of the cab panels, as suggested by some, but that's not what he wrote.
Cabinet leakage losses are...
Forum: DIY Speakers and Subs   12-19-2014, 10:03 AM
Replies: 64
Views: 703
Posted By Bill Fitzmaurice
With an impedance sweep. If you lack that...

With an impedance sweep. If you lack that capability do the old rice dance trick. Put the cab face up, put some rice on the cone, do a low frequency sine wave sweep. Cone excursion, and therefore the...
Forum: DIY Speakers and Subs   12-19-2014, 06:29 AM
Replies: 19
Views: 338
Posted By Bill Fitzmaurice
If you're going to power something on its own...

If you're going to power something on its own circuit it should be the power amp.
Forum: Audio Theory, Setup, and Chat   12-19-2014, 06:24 AM
Replies: 6
Views: 76
Posted By Bill Fitzmaurice
Based on what? If it's real world measured...

Based on what? If it's real world measured performance that's one thing, if it's advertising that's something else again. When digital first hit the scene 30 odd years ago there were substantial...
Forum: Audio Theory, Setup, and Chat   12-19-2014, 06:15 AM
Replies: 2
Views: 46
Posted By Bill Fitzmaurice
Don't. If you lack enough current capacity that's...

Don't. If you lack enough current capacity that's a matter of adding another branch circuit. The first thing I'd do is to plug all of the high current gear direct to the wall, gizmos like the Panamax...
Forum: DIY Speakers and Subs   12-18-2014, 07:59 PM
Replies: 64
Views: 703
Posted By Bill Fitzmaurice
Impedance is an electrical measurement, not an...

Impedance is an electrical measurement, not an acoustical measurement. It can be done with a sine wave generator, amp, DMM and a specialized resistor bridge. I use a WT 3. ...
Forum: DIY Speakers and Subs   12-18-2014, 07:54 PM
Replies: 19
Views: 338
Posted By Bill Fitzmaurice
I'm not experienced in whether or not that could...

I'm not experienced in whether or not that could be caused by the TV being voltage or current starved, but I'd say that's a more likely explanation than low frequency waves. If they could cause that...
Forum: Speakers   12-18-2014, 02:21 PM
Replies: 2
Views: 48
Posted By Bill Fitzmaurice
JBL Parts and accessories: 1-800-336-4525

JBL Parts and accessories: 1-800-336-4525
Forum: DIY Speakers and Subs   12-18-2014, 02:12 PM
Replies: 19
Views: 338
Posted By Bill Fitzmaurice
If the only change to the system is the amp then...

If the only change to the system is the amp then it's possible the amp is causing the TV to be current starved, especially if they're plugged into the same outlet. Even if they aren't they may still...
Forum: DIY Speakers and Subs   12-18-2014, 11:58 AM
Replies: 64
Views: 703
Posted By Bill Fitzmaurice
I don't have REW, but if it does measure...

I don't have REW, but if it does measure impedance then the frequency where it is the lowest value in between the two low frequency peaks is Fb.
Forum: DIY Speakers and Subs   12-18-2014, 06:14 AM
Replies: 9
Views: 142
Posted By Bill Fitzmaurice
Since they only go down to 180 Hz they'd need to...

Since they only go down to 180 Hz they'd need to be used with a midbass to reach 100Hz or lower to reach where the subs extend to.
Forum: Subwoofers, Bass, and Transducers   12-17-2014, 01:35 PM
Replies: 19
Views: 244
Posted By Bill Fitzmaurice
That's not true, and saying so does nothing to...

That's not true, and saying so does nothing to aid the OP. The only advantage to sealed is that they don't go as low as ported, with f3 of 35-40Hz being common. If the room is small enough, with a...
Forum: Subwoofers, Bass, and Transducers   12-17-2014, 12:22 PM
Replies: 19
Views: 244
Posted By Bill Fitzmaurice
Not necessarily. Once you introduce room...

Not necessarily. Once you introduce room interactions, including but not limited to boundary effects and cabin gain, you can end up with more low end than an anechoic measurement predicts, especially...
Forum: DIY Speakers and Subs   12-17-2014, 10:14 AM
Replies: 3
Views: 69
Posted By Bill Fitzmaurice
You can re-purpose PA cabs with subwoofer...

You can re-purpose PA cabs with subwoofer drivers, but only if you software model the driver/cab combination and make the necessary adjustments to the port size/box tuning. Since the PA cabs are...
Forum: DIY Speakers and Subs   12-17-2014, 10:09 AM
Replies: 64
Views: 703
Posted By Bill Fitzmaurice
That depends. At the edges of a port, within 1/4...

That depends. At the edges of a port, within 1/4 inch or so, there's a lot of friction between the air mass within the port and the port walls. That occurs with all port shapes and locations. What...
Forum: Subwoofers, Bass, and Transducers   12-17-2014, 06:40 AM
Replies: 19
Views: 244
Posted By Bill Fitzmaurice
You don't want to accentuate anything. What you...

You don't want to accentuate anything. What you want is for the system to accurately reproduce the sound track content.
Forum: DIY Speakers and Subs   12-17-2014, 06:35 AM
Replies: 64
Views: 703
Posted By Bill Fitzmaurice
These, and the subsequent questions, are why you...

These, and the subsequent questions, are why you should learn the nuts and bolts of speaker building by using a tried and tested design that already has these and all the other design and...
Forum: Speakers   12-16-2014, 08:32 PM
Replies: 11
Views: 190
Posted By Bill Fitzmaurice
Where are your subs? A major issue with respect...

Where are your subs?
A major issue with respect to placement is Allison Effect, a dip in response where the reflected wave off the wall behind the speakers meets the original wave 180 degrees out of...
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