Class D Amplifier for Outdoor Theater?

Cranioclast

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I've been hosting an outdoor movie event for over 10 years now and have been slowly adding and upgrading equipment. There are usually around 30 people, pretty spread out and up to 50ft away from the speakers, so it needs to be fairly loud. I don't really know anything about speakers and amplifiers, so I could use some advice.

The current audio setup is:

JBL Control 28-1 8", 8ohm speakers
Denon AVR-3300 receiver (105wpc? Maybe 140?)

I finally bought a decent 1080p DLP projector instead of borrowing an XGA one from the school. So I want to justify my purchase by having more than one movie per year. It's just such a hassle to get the whole thing set up that it's hard get motivated to do so. To make things easier, I'm collecting all the parts into a single case that I can roll (or drag, at least) out onto the lawn. Then the case can double as the table where the laptop, projector and amp will sit.

theater-box-minus-ext-cable-and-projector.jpg

I think I'll keep the projector separate, since it's a little delicate to be crammed in there with all these heavy pieces. I'm going to probably add some foam blocks, but it's still going to get a bit rough in there. I also need to get another extension cord that can just live in there. I don't want to have to track anything down when I go to set this up.

Anyway, that old Denon is HEAVY. It's also just large, to the point where there will barely be enough room for it, the projector and a laptop on the case/projector table. I would really like to replace it with something smaller, which brings me to my reason for posting.

A Fosi Audio TB10D is under $70 after taxes on Amazon. Apparently, with the included power supply, it puts out around 70wpc. A step down from the 100+ of the Denon, but maybe enough? My first amplifier used for this setup was an old Sony 50wpc stereo receiver that I bought in high school. It was not powerful enough to elevate a mumbly Joe Namath above the peanut gallery. So I'm a little concerned about the TB10D providing the required watts.

So the TB10D is in impulse buy range, but feels like it might not be enough. I'm mad at myself for previously buying a cheap, no-name HD projector, thinking it would be a step up from the borrowed XGA one. It got used one year and was a disaster.

The Fosi V3 with a 48v power supply should do the job, but is more than double the price in the end. If it's not going to be an improve the sound, I don't know if I feel like spending that much just for ease of setup. Maybe, though. I'm torn.

So what are the odds the cheap Fosi will work for my needs?
If it won't, is there any reason to spend nearly $150 to replace my functional, but bulky receiver with the more expensive one?
Will it be an upgrade in any way, or just easier to move around?
Are there other options I should look at?
Will you just come to my house and hook all this up every couple of weeks so I don't need to worry about it?
 
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Drizzt321

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What about something like Pyle? In my lower end usage, they seem pretty decent, although it's been more for some general music with cheapish speakers than for movie listening.

Not sure if they make ones powerful enough to suit you, I dunno.

Also, might want to consider some kind of folding speaker stands. Don't cheap out, otherwise they'll wobble a lot, possibly including a 5lb sand bag for each stand. That's more room needed though, if you want it 100% in a single rolling case/bag thingie.
 

owdi

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The difference in output power is larger than you think, because the Fosi amp shows rated output at 1khz with 1% THD, while the Denon is rated at 20hz-20khz with .05% THD.

With the included 32V supply, the Fosi amp would make about 50 watts per channel at .05% THD into 8 ohms (per TPA3225 datasheet)

The Denon on the other hand is likely making more than rated power power while driving only 2 speakers, since it's power supply is designed to handle 9 channels of output. That Denon is likely pushing closer to 150 watts per channel at .05% THD.

If you're not already pushing the Denon to the limits, the Fosi should work.
 

Cool Modine

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Never heard of “Fosi.” Sounds like you’re just rolling your dice on a random AliExpress product. The specs are bullshit; can’t get 600W output from a 480W power supply, lol. And as small as it is, it’s not going to be able to output a ton of watts nonstop for a couple hours. Either the output is drastically lower than you think, or it’ll overheat quickly.

Now that Denon is 33 pounds. Impressive. In the realm of home stereo gear, this Yamaha is only 15 pounds and $200.

Another step up would be a pro audio amp, like a Crown XLS1002. 8.6 pounds, but more expensive. https://www.parts-express.com/Crown...mplifier-2-x-350W-at-4-Ohm-245-507?quantity=1

Keep in mind that doubling power only gets you +3 dB of volume. Halving power, likewise, -3 dB of volume. So after a point, power has rapidly diminishing value. But if that Fosi turns out to be 14 watt per channel, that’s a pretty big drop from 140 wpc.

There’s also a point where you would be better served with more efficient speakers than with more power.
 

Cool Modine

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Fosi amp would make
I think you mean, the Fosi amp “could” make 50W. There’s no guarantee that it has the chip the web site describes, or that it’s an authentic chip and not a fake with worse capabilities. And even if it was legit the design of the whole thing might still limit its performance.

I’d trust that amp as far as I could throw OP’s Denon.
 

macosandlinux

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Fosi Audio is a Chinese HiFi brand that has some very decent gear for insanely low prices (desktop sized units, cheap on shipping, plus would save you space when carrying). Don't care about Class D, meaningless here. Pyle (sold at BHPhoto) might also be a value buy and good enough for your usage.

Also consider active speakers (that have amplification built-in) and look for used units here! Your current passive ones are fine, so not sure if that would make sense. That might be a solution for a small, compact system.
 

Cranioclast

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Never heard of “Fosi.” Sounds like you’re just rolling your dice on a random AliExpress product. The specs are bullshit; can’t get 600W output from a 480W power supply, lol. And as small as it is, it’s not going to be able to output a ton of watts nonstop for a couple hours. Either the output is drastically lower than you think, or it’ll overheat quickly.
I hadn't heard of Fosi or class-D amplifiers until a few weeks ago. I had an old AudioSource amp in our whole-house wired setup die and they came up when searching for a replacement. I ended up with an updated version of the one I had, but it popped back into my head when I started putting together the theater kit.

Fosi has had at least one successful Kickstarter and seems to have a bit of a following. If they are just a label on shoddy, mass-produced junk, they've done a good job of hiding it. I don't know who's reputable among audio YouTubers or bloggers, so maybe I am just getting hoodwinked by some shills or just people who don't know what they're talking about. That's one reason why I asked here.

As for overheating, that's what the whole class-D/switching amplifiers are supposed to be good at. They're supposed to be so efficient that they barely give off heat.

But it's still a question of whether the claims are too good to be true. Even the big fans concede that you'll never see the theoretical output with the power supplies that ship with any of these things. I'm just wondering if it might be enough for what I need.
 

Cranioclast

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Also consider active speakers (that have amplification built-in) and look for used units here! Your current passive ones are fine, so not sure if that would make sense. That might be a solution for a small, compact system.
If I was starting from scratch, I might go that route.

I said I've got those JBL Control 28-1 speakers, but I didn't mention that I have eight of them. Plus four of their smaller siblings and a subwoofer. A friend's company moved to a new building and decided they weren't taking their conference/presentation room sound system with them. I also got their projector, but it's older, massive, not that bright, and won't work with HDCP sources. I'm kind of kicking myself for not taking the amps, but that wouldn't have helped me downsize, anyway.

So I've spent nothing on audio for this setup so far.
 

w00key

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There are usually around 30 people, pretty spread out and up to 50ft away from the speakers, so it needs to be fairly loud. I don't really know anything about speakers and amplifiers, so I could use some advice.
How loud do you turn it to? The JBLs you linked are 90dB/W @ 1m, or 70 dB at 10 meters in free field following the inverse square law. Feed it 10W and you have 100 dB @ 1m (ear protection recommended) and 80 dB, almost reference level, at 10 meters.

I think 50W with high efficiency amp should be plenty, especially if you wire it up with multiple, 2 series 2 parallel = still 8 ohm per channel, that increases sensitivity (that dB/W value). Wire 2 parallel and it drops to 4 ohm, your linked amp likes that and can output almost twice the power then.


What really needs power is bass, is that subwoofer powered? What you need is to high pass the L and R channel, the speakers then no longer need to bother with < 100-150 hz sound and need far less power. The powered sub can handle it with hundreds of watts of power, hundreds of W RMS and kW+ peak isn't unusual.

Subs also come with stereo input + output, where the output is stripped of low frequency sound. Otherwise maybe a mini mixer / DIY board / Mini DSP that does this?
 
I hadn't heard of Fosi or class-D amplifiers until a few weeks ago. I had an old AudioSource amp in our whole-house wired setup die and they came up when searching for a replacement. I ended up with an updated version of the one I had, but it popped back into my head when I started putting together the theater kit.

Fosi has had at least one successful Kickstarter and seems to have a bit of a following. If they are just a label on shoddy, mass-produced junk, they've done a good job of hiding it. I don't know who's reputable among audio YouTubers or bloggers, so maybe I am just getting hoodwinked by some shills or just people who don't know what they're talking about. That's one reason why I asked here.

As for overheating, that's what the whole class-D/switching amplifiers are supposed to be good at. They're supposed to be so efficient that they barely give off heat.

But it's still a question of whether the claims are too good to be true. Even the big fans concede that you'll never see the theoretical output with the power supplies that ship with any of these things. I'm just wondering if it might be enough for what I need.

Fosi Audio's products are not junk, they are a low-end HiFi (mostly headphone amps) out from China. If their specs work for you, their prices are rock bottom. Otherwise go with Pyle Audio (sold at B&H Photo) and receive their helpful (chat) support, returns etc.

And as you said above, with having the JBL's already, you just need a decent amp - for your usage that is more about power capabilities/portability and not about sound quality. B&H could advise you on the Pyle amp and match them to your speakers - if it does not work for you, send the amp back?


View: https://youtu.be/uLiah_4Od_g
 

Cranioclast

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How loud do you turn it to? The JBLs you linked are 90dB/W @ 1m, or 70 dB at 10 meters in free field following the inverse square law. Feed it 10W and you have 100 dB @ 1m (ear protection recommended) and 80 dB, almost reference level, at 10 meters.

I think 50W with high efficiency amp should be plenty, especially if you wire it up with multiple, 2 series 2 parallel = still 8 ohm per channel, that increases sensitivity (that dB/W value). Wire 2 parallel and it drops to 4 ohm, your linked amp likes that and can output almost twice the power then.
The main event is for a motorcycle club with a median age of about 70, so hearing loss has to be assumed. The films are generally from the 60s and 70s with poor audio quality and often non-American accents. On top of that, there are always people talking. The movies inspire MST3K-type commentary, so that's okay, but someone's always complaining that they can't hear the dialogue.

With my old 50wpc receiver and some cheap speakers my cousin was throwing out, I could only turn it up to about 60% before getting clipping during loud scenes (movies with motorcycles). I was always having to raise or lower it depending on the scene.

Two years ago, I tried the LG XBOOM speaker that I got free with my TV. Nobody really liked that. If I could have connected three of them and put them in the different areas where people were sitting, that might have worked. Just the one in the middle of the lawn wasn't enough.

Last year was the first try with the new JBLs. I couldn't find the 3.5mm to RCA cable I'd used in the past and had to use 25'(?)one that I had bought for a long run to an AppleTV Express I'd had once. I'm blaming that cable for why the big >100wpc Denon was even quieter than the old 50wpc Sony. I haven't tested it with a shorter adapter, so I can't say for sure that it wasn't due to the speakers or the amp, though.

Anyway, I'm not sure if I've ever had the audio right for this. It may have been good that last year before we skipped a couple due to COVID. I think that was the same Denon and my cousin's old dorm speakers, but with a pigtail 3.5mm to RCA adapter.

What really needs power is bass, is that subwoofer powered? What you need is to high pass the L and R channel, the speakers then no longer need to bother with < 100-150 hz sound and need far less power. The powered sub can handle it with hundreds of watts of power, hundreds of W RMS and kW+ peak isn't unusual.

Subs also come with stereo input + output, where the output is stripped of low frequency sound. Otherwise maybe a mini mixer / DIY board / Mini DSP that does this?
The subwoofer is a JBL AC115S, which is not powered and measures 16x20x24 inches. It does not fit in the box and would not fit with my intention to make this simple to set up on a whim.

However, if someone can tell me how to power it for when I want to put on a big show, I'd love to know. I've got another old Denon amp that I was wondering if I could use in some bi-amping arrangement if I wanted to. I've never dealt with an un-powered subwoofer before.
 
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AndrewZ

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You've been doing this for a while and you are learning that outdoor audio needs a lot more output power than indoor audio. What you really need to focus on is pure RMS output watts into speakers capable of handling a lot of watts. Nothing else really matters. You need a big amp, and big speakers. Like your last high school dance in the gymnasium.
 

Baenwort

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The best place I've found for reviews of amps at this price range is: https://www.audiosciencereview.com/forum/index.php?pages/Reviews/

I recently picked up a pair of amps (one for a pair of high eff [97db/W] speakers for the garage/backyard, one for a tactile transducer for the couch) with a low budget, high output need.

I ended up with a S.M.S.L. amp that could be put in bridge mode and actually came with a PSU that could meet it's peak rating for the transducer and a AIYIMA that I reused a old benchtop PSU to meet the speakers needs.

Works well enough for the cost. I've heard similar reports about Fosi, Pyle and Dayton Audio. You have to be careful and look for actual testing reviews as the specs are all theoretical numbers based upon component specs that marketing misuses.
 

Cool Modine

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"LG XBOOM speaker"
That's not a speaker. I mean, it is, but anything that's bluetooth and battery powered is meant to be portable and convenient above all other characteristics. It's the wrong tool for the job; it's a Smart Car when you need a dump truck.
"JBL AC115S"
That's not bad. The Behringer NX series amplifiers have been pretty popular for subwoofers in the DIY home theater crowd, and I've got a few amps from the older (but basically identical) NU series. The NX3000 is $300 right now, and would do a good job bridged into that sub. It's also class D and light.

What you really need to focus on is pure RMS output watts into speakers capable of handling a lot of watts. Nothing else really matters. You need a big amp, and big speakers. Like your last high school dance in the gymnasium.
Well, no, not exactly. Speaker sensitivity is a huge thing as well. Cranio could easily pick up 6-10 dB more volume with more sensitive speakers. Of course, higher sensitivity typically comes with having "bigger" speakers but the devil is in the details. If he needs more SPL then the first step is more sensitive speakers as his current JBLs can't take significantly more power than he has now. But when we're talking new speakers and high-powered amps, budgets are flying out the window.


Cranio, maybe we're all barking up the wrong tree here. What problem do you really need to solve? Is it just finding a more portable amplifier, as you mention in the OP. Does it solve your portability problem to just have a larger, easier to move case? This might be too small, but you get the idea, something with big honking wheels will be easier to drag around even with the heavy AVR: Gorilla Carts. Or do you actually need more performance too? How many audio channels are you using? Stereo, 3, 5.1, 7.1, whatever?
 

Kaiser Sosei

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Cranio, maybe we're all barking up the wrong tree here. What problem do you really need to solve? Is it just finding a more portable amplifier, as you mention in the OP. Does it solve your portability problem to just have a larger, easier to move case? This might be too small, but you get the idea, something with big honking wheels will be easier to drag around even with the heavy AVR: Gorilla Carts. Or do you actually need more performance too? How many audio channels are you using? Stereo, 3, 5.1, 7.1, whatever?
I read the goal as just something easier to lug around and move so Cranio can do more than one show a year and not make it a slog every time.

How much are you honestly ready to spend? Your links for sub $100 amps make me think that price may be an issue, which is fine, just need to be up front about it. Do you want something off the shelf or is building your own a possibility? You mention having 12 speakers, are you trying to run them all at once?

Ultimately it comes down to how much is it worth not lugging around a 35 pound amp.

If you are going to replace it, I'd stick with more PA type equipment than home theater.

Or get yourself a roadie.
 

w00key

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@Baenwort Awesome link, thank you!

@Cranioclast The audiosciencereview test shows this Fosi amp does 34 watts stereo into 8 ohms using the 32v supply. My previous estimate of 50 watts was a bit high. It does 89 watts with the larger 48v supply, so you definitely want the larger supply. Audiosciencereview Fosi Audio V3 Amplifier Review
That little thing can throw out 141W with the 48V PSU at 4 ohm. That's why I suggested using two of those 8 ohm speakers in parallel, making it 4 ohm electrically seen from the amp.

141W continuous and 190W peak measured is a ton of power, probably much more than the ancient Denon can actually send out. It's not too far from PA active speakers that are "rated" 200W but gets no where near that number without crackling.

It also isn't too underpowered for those JBLs, on the spec sheet they can handle 90W max of pink noise turning it into 118 dB. With 70Wpc divided by 2 parallel, that would be 35W into 113 dB each, x4 speakers = jesus that is loud.


My full size 2020-era Denon X3600H only does 167/250 on an audiosciencereview test and it was marketed as 9.2, 180W per channel, and 105W at low distortion. Well it achieves about 83W of them on the review.


I would just go for them with the bigger 48V PSU. Double it up if you need to, powering all 8 speakers that you have. This seems to be the best bang for bucks, getting a new AVR gets you about the same performance for much more money.

[edit]

Oh just saw this on the spec

Recommended Protective High-Pass
45 Hz high-pass (24 dB/oct) for 8Ω operation plus 15W and 7.5W taps; 55 Hz for 30W tap; 65 Hz for 60W tap.


So without any high pass you can't run these JBLs at super high power anyway, that ~30W per speaker of the Fosi is perfect, you don't want much more or risk blowing up the speakers.

With a 60hz high pass an a powered sub you could do more, but nope if you send the speakers a full range signal. If using a PC for playback you can high pass the output with Equalizer APO.
 
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