Question about using voltage regulators (Furman SPR-20i) with subwoofers (JL Gothams) - AVS Forum
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post #1 of 9 Old 07-21-2014, 02:23 PM - Thread Starter
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Question about using voltage regulators (Furman SPR-20i) with subwoofers (JL Gothams)

Neither JLA nor Furman answered this specific question when I emailed their tech support, so I'm asking it on our forums. Would it be beneficial/safe to connect each Gotham to its own voltage regulator? Some people have mentioned that it's best to connect a sub directly to a wall outlet, and that's the part that confuses me. Now I'm struggling to understand how having a power source of exactly 120v (± 1.0V) fed to each sub with a 20 amp RMS power reserve + the highest level of AC/surge protection possible would be drawbacks.

My plan was this for each Gotham:
Dedicated 20 amp circuit --> Furman SPR-20i --> JL Gotham g213
Dedicated 20 amp circuit --> Furman SPR-20i --> JL Gotham g213

And, would it be OK to just leave the Gothams on Auto for its power setting and then cut power to them by powering off the voltage regulators (Furman SPR-20i) instead of manually setting the Gothams to off after each use?

Alternatively, Furman recommended leaving the voltage regulators on at all times, but would the same hold true for the JL Gothams? Is it best to leave them on at all times even when not in use all year round?

Disclosure:
I ordered 3 units of SPR-20i STABLE POWER AC VOLTAGE REGULATORs (one dedicated for each JL Gotham g213s, another for everything else).

Also ordered 1 unit of Furman IT-REFERENCE 20i DISCRETE SYMMETRICAL AC POWER SOURCE.

They look pretty cool when stacked:


The plan is to have one 20 amp circuit + one SPR-20i dedicated per Gotham, and a 3rd 20 amp circuit for everything else powered by SPR-20i + IT-REFERENCE 20i. I’ve already tested my circuit breaker to confirm that everything is 20 amp and on its own circuit (the electrician added another breaker box to make this possible). So what's best? With or without these voltage regulators? I still have time to decide whether to keep or sell any of this gear since they won't be delivered until early August (the REF 20i is back-ordered until July 25th), and all will be new and factory sealed, so easier to sell as NIB than used.

Last edited by Neo-Geo; 07-21-2014 at 02:27 PM.
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post #2 of 9 Old 07-21-2014, 03:10 PM
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Originally Posted by Neo-Geo View Post
I'm struggling to understand how having a power source of exactly 120v (± 1.0V) fed to each sub with a 20 amp RMS power reserve + the highest level of AC/surge protection possible would be drawbacks.
The main drawback is the drain on your wallet. Subwoofer amplifiers don't require precise voltage regulation. That's why not a single amp manufacturer that I'm aware of recommends their use, while more than a few specifically recommend that they not be used.

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post #3 of 9 Old 07-21-2014, 03:45 PM - Thread Starter
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I understand the drain on the wallet and not necessary argument, the same is often said for the JL Gothams. What I still don't understand is why you wouldn't want exactly 120v provided to equipment designed to operate on 120v, why you wouldn't want the highest level of surge protection, and why you wouldn't want an abundant amperage of perfect 120v power should your device require it. So besides the cost, what are the drawbacks/risks? I assume drawbacks must exist or people (and apparently even manufacturers) wouldn't specifically suggest to avoid voltage regulation, but oddly, no one seems to say what those drawbacks are.

I realize that most people don't give our power sources much if any concern, as doing so is on par with discerning the quality of air and water for our bodies, i.e., generally considered to be unnecessary and a waste of time/energy/resources. My logic was to achieve the highest level of protection for my gear while also insuring optimal power related performance, and if this is best achieved by NOT investing in the Furman SPR-20i x3 and simply relying on a standard wall outlet and nothing else, then I'd like to understand why that is. Without voltage regulation, my ht room outlets average 115v and can dip to 110v, but I struggle to see how that's beneficial over a steady stream of 120v.

If the opposite really is true (that precision level voltage and abundant amperage is bad), then shouldn't there be a strong market for irregular and unreliable power generators? If so, an audiophile's utopia would be ungrounded outlets in North Korean cities that suffer from frequent spikes and brownouts (essentially what car audio enthusiasts struggle with).

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post #4 of 9 Old 07-21-2014, 04:47 PM
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Without voltage regulation, my ht room outlets average 115v and can dip to 110v, but I struggle to see how that's beneficial over a steady stream of 120v.
Because amplifier designers figured out how to make their products perfectly comfortable running with voltages anywhere between 100v and 130v fifty odd years before the invention of voltage regulation. There are some electronic devices that benefit from voltage regulation, but very few amplifiers do.

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post #5 of 9 Old 07-21-2014, 06:28 PM - Thread Starter
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As it stands, we don't even have any remote theories of the alleged drawbacks of having precision voltage, abundant amperage, noise free power, and surge protection. With that established, would it be OK to just leave the Gothams on Auto for its power setting and then cut power to them by powering off the voltage regulators (Furman SPR-20i) instead of manually setting the Gothams to off after each use?

Alternatively, Furman recommended leaving the voltage regulators on at all times, but would the same hold true for the JL Gothams? Is it best to leave subs on at all times even when not in use all year round?
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post #6 of 9 Old 07-30-2014, 05:55 PM
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We don't have a theory, we have good engineering practice. Many of your points, started life in a marketing brochure. By the way, you don't get 'abundant amperage' unless you have a battery and even then it's more likely to get less amperage.

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post #7 of 9 Old 07-30-2014, 07:21 PM - Thread Starter
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When asked for any downsides of a voltage regulator, Barry Ober of JL Audio recommended that I NOT use a voltage regulator, citing that the surge protection of most devices is a sacrificial process, meaning that the component is sacrificed/destroyed upon a high voltage surge. He also pointed out the high cost and how voltage regulation wasn't necessary unless the power was off by a very wide margin, as in 200+ volts. He promoted buying and using the SA-15/20-AR SurgeX as a standalone surge protector for the Gotham. He also suggested changing out standard power outlets to hospital grade for tighter connections.

However any benefit from the SurgeX is negated according to the manual of the Furman SPR-20i, for it states, "Another critical feature is our exclusive Series Multi-Stage Protection. This virtually maintenance-free surge suppression assures the highest level of AC protection possible, without sacrificing itself when the offending surge is severe – no damaged equipment, no service calls, no down time."

Further, the manual specifically mentions amps/subwoofers: "With today’s chaotic demands on many municipal power facilities, AC voltage is often reduced so that it can be stretched to fulfill excess demand. This creates a substantial negative impact on your system’s performance. Power amplifiers and powered subwoofers cannot perform to their full potential. Even a relatively modest reduction in AC voltage can obliterate the sonic impact of an otherwise superior system. Just as problematic are excessively high line voltages. Excess voltage can overheat sensitive circuits; lower the life and reliability of projector lamps, and cause many circuits to shut down.

With the SPR-20i’s exclusive Stable Power AC Voltage Regulation Technology, voltage-starved power amplifiers and powered subwoofers perform at their full potential. With the SPR-20i, home theaters are supplied with constant, virtually unwavering AC voltage. This assures trouble-free service for any environment suffering from unstable power."


Perhaps the Furman manual is what you are referring to as pure marketing. Yet big budget studios believe in Furman's alleged snake oil products, so some merit must exist. I'm still leaning towards keeping the SPR-20i x 3 since we still don't have any proposed drawbacks for their use, only potential benefits that may or may not be readily realized. If everything runs perfectly for long-term, then the user will remain oblivious to the transparent benefits, but that's good enough for me. This is like arguing no name spaghetti wire vs Transparent Opus, term life vs whole-life insurance, tar based asphalt shingle vs a slate roof, aluminum vs copper gutters, or Masonite vs HardiePlank since the vast majority will consider the latter to be unnecessary, a waste of money, and with subjective benefits.

Last edited by Neo-Geo; 08-03-2014 at 11:17 PM.
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post #8 of 9 Old 08-01-2014, 05:55 PM
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As I wrote:
"started life in a marketing brochure"

and that's marketing at it's finest!

Kevin
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post #9 of 9 Old 08-01-2014, 06:16 PM
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This is not to say that Furman does not make good problem solving products. The reason the pros use them in some situations is because they solve the problem at hand. But most audiophiles (and pros) don't have these problems.

Kevin
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g213 , jl gotham , ref 20i , spr-20i
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