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Class D Switching Power Amplifiers and Power D/A conversion

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Old 16th April 2010, 03:17 PM   #511
Havoc08 is offline Havoc08  Denmark
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Quote:
Originally Posted by ThokN View Post
1. I still haven't been able to understand how we should wire up the Amp9 to the speakers. My problem is that it has 4-channels, while the 4 speakers of the boominator serves as only 2 channels since they are paralleled. And I think I've understood that if you bridge the 4 outputs into 2 outputs, it will double the resistance from 4Ω to 8Ω on each of the two resulting channels. But since the 4x8Ω speakers are paralleled, they will act as 2x4Ω speakers, which the amplifier wouldn't like when bridged. So...how do we wire the outputs to get the full power from the amplifier into the paralleled speakers?

You can either go for PLLXO and use the 4 channels the best way possible or you can "just" wire it up as you say with the 3 units per channel equaling 4 ohms?

You need to know some things about the amp9. At 24v it can run 4ohm speakers and generate up to 100watts per channel. at 12-14,4v it can run 2ohm speakers with no problem.
You can even parallel the inputs and outputs 4->2 channels to run 2ohm sources at 24v for 200watts per channel.

2. I've seen you mention the Sure 4x100W amplifier on the Roskilde-forum, and we are very tempted to go with that instead because of the more power and cheaper price, but do you know if it has any significant drawbacks compared to the Amp9? Sound-quality is not important. Our main concern is power consumption(efficiency and idle), heat, and if we will be able to use all 400W into the 2 (2x2) speakers.

The sure is worse at powerconsumption than the 41hz amp. It gets hotter and sounds worse (although not bad, just not as good).
With this high effeciency design that saturnus has made, the idea is actually not to use power and money on high wattage amps as the speaker design generates high SPL at low power levels (high power also equals more aH batteries). Maybe you should try the ta2024 T amps first as they idle much lower than the taa4100 and sure 2050 amp.
Alternatively you could go for something like the amp4 or sure 2050 2x100watt which sits in between the 2024 amps and amp9.


3. Will 2x 12V SLA's delivering a max of 2.1A each, wired to 24V even be able to drive any of these amps? Tried with an online calculator which says that 24V and 400W will draw 16.67 Amps, which sound like an awful lot to me.

The amp9 peaks at 11A as far as I remember but you will likely never see it happen as music signal does not contain all frequences at once. Does your SLAs really only deliver 2.1 amps? I use 12v 7aH gel lead batteries which are rated much much higher in short term power delivery (as engines crank). 2.1A is not enough and you might destroy the amp fairly quickly
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Old 16th April 2010, 03:41 PM   #512
teamacc is offline teamacc  Netherlands
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Quote:
Originally Posted by ThokN View Post
Wow thanks for the quick reply!

My guess is that heat will be a concern since it will be put inside a small box within the boominator. Do you think the 2-channel version will be cool enough without a fan?

And when you say that we shouldn't bridge the 4-channel, does that include the Amp9? Cause the 41hz website says:
"Outputs can be paralleled for even higher outputs into very low impedance loads"

If the Amp9 is capable of that, this amp would be the one to go for if we want a louder boominator, right?
The sure cant be bridged, it is already internally bridged.
I dont know for the 41hz amps.
You might take a look at the amp 11, as it can power 4 ohm loads, but its a mono amp. You will need 2, and it seems it is a hard amp to solder.

DO NOT put the sure 4 channel amp in a case. It needs at least a fan when powered above... well... almost any working voltage

If you want really high power, there also is an amp 11 HV version, up to 200w output/channel. Again, it is a mono amp...
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Old 16th April 2010, 03:47 PM   #513
dododoo is offline dododoo  United Kingdom
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excuse my incomplete info but i'm pretty sure ( enough to risk posting ! ) that bridging and parralleling are different.

see here for a thread on paralleling the amp 9 as i don't know it well enough to explain it! :-)

Anyone with experience paralleling Amp9 outputs?

hope that helps a bit...
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Old 16th April 2010, 04:25 PM   #514
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Alrighty, I'm not building any of this stuff but the projects are interesting and I pretty much scanned the whole thread. I saw almost no circuit drawings. Lots of talk about box alignment and tweeter crossovers, but didn't see anything about woofer crossovers.

Folks will want to be sure they have not omitted a high pass filter for the woofer. If your port frequency is at 70Hz, for example, you might want to use a 24db rolloff below that, maybe 60 at the lowest. Where to crossover would be a compromise between sound quality and energy efficiency, and filtering right at the tuning frequency might not be a bad idea, but ignoring a high pass on the woofer when you're losing response in truckloads below 60-90Hz might cost you half the running time in waste heat in the woofers (and lots of dynamic headroom as well, depending on the signal.) Of course you want this to be a signal level crossover of some kind to keep low end that can't be converted into sound pressure out of the amplifiers altogether. Please excuse if this consideration has already been addressed across the board and I missed it.

Last edited by Andrew Eckhardt; 16th April 2010 at 04:29 PM.
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Old 16th April 2010, 04:44 PM   #515
Havoc08 is offline Havoc08  Denmark
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AMP-1B is also a cheap high power solution, but test first if it is needed.

Bridging and paralleling are NOT the same thing. The amp9 is also bridged internally so only way to increase power is to parallel and half the resistance of the speakers.

@ andrew
Do you mean a bandpass filter for the woofer? I didn't quite follow this "but ignoring a high pass on the woofer when you're losing response in truckloads below 60-90Hz might cost you half the running time in waste heat in the woofers"
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Old 16th April 2010, 05:09 PM   #516
ThokN is offline ThokN  Denmark
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Quote:
Originally Posted by teamacc
You can either go for PLLXO and use the 4 channels the best way possible or you can "just" wire it up as you say with the 3 units per channel equaling 4 ohms?
I've tried to look at PLLXO, but it seems a bit complicated. I guess the point is to have tweeters on two channels, and woofers on the other two? Anyway, I hope we can just go with the original design where tweeters and woofers are on the same channel to simplify it for us noobs, hehe.

Quote:
Originally Posted by teamacc
You need to know some things about the amp9. At 24v it can run 4ohm speakers and generate up to 100watts per channel. at 12-14,4v it can run 2ohm speakers with no problem.
You can even parallel the inputs and outputs 4->2 channels to run 2ohm sources at 24v for 200watts per channel.
.
Sounds like there are quite a lot of possibilities with the Amp9! That's good to hear. Does this mean that we can parallel the ins/outs getting 2x200W into 2x 4ohm speakers?

If we could get hold of 4 of the HP10W 4ohm version we could even get them down to 2ohms/channel by paralleling the speakers AND channels, without destroying the Amp9? I imagine that would get pretty loud .

Wow...this is quite advanced for us, concidering that all we want is to make a boominator that just plays louder than the current one with an Amp6-B (which was still a bit advanced for us, ).

I'm SO glad you guys are helping us with this!
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Old 16th April 2010, 05:09 PM   #517
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Good point on the high-pass filter for the woofers.

That is fairly easy to accomplish by adjusting the value of the input caps on the amp, since they're there anyway. I think most people are doing it that way rather than doing something with post-amplification crossover components.

Not sure what the numbers say, but I think you start seeing roll-off in the bass somewhere around 1uf or so. Anybody done the calculations/measurements?

--Buckapound
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Old 16th April 2010, 05:14 PM   #518
ThokN is offline ThokN  Denmark
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Quote:
Originally Posted by teamacc View Post
The sure cant be bridged, it is already internally bridged.
I dont know for the 41hz amps.
You might take a look at the amp 11, as it can power 4 ohm loads, but its a mono amp. You will need 2, and it seems it is a hard amp to solder.
Okay thank you! I think we will try to avoid the Sure ones. I think I read that the 2x100W also gets quite hot.

The 2x Amp11 is an option yes, but it is a bit more expensive in total, and even more stuff for us to break
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Old 16th April 2010, 05:29 PM   #519
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Yes, it would optimally be a bandpass.
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Old 16th April 2010, 05:30 PM   #520
ThokN is offline ThokN  Denmark
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Quote:
Originally Posted by Havoc08 View Post
Bridging and paralleling are NOT the same thing. The amp9 is also bridged internally so only way to increase power is to parallel and half the resistance of the speakers.
Sorry if this is a stupid question, but bridging is where you solder some components together on the board, and parallel is just when you use two output-channels as a single output?

If so, we can parallel the outputs and leave it there, I think. We are not able to lower the speaker resistance, since they are already paralleled in pairs. (4x8ohm into 2x2 @4ohm).
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