Ha! Guess that base is well covered! Maybe a different amp is what you need. Not necessarily more power though. |
I seriously doubt it's a power issue seeing as how I'm powering much bigger, much more challenging Focals with a 32 watt amp. |
My 936’s dip down to 2.8 ohm at 108Hz with a modest -20 degree phase angle and stay below 4 ohm out to 500Hz. The F5 has no problems at all producing plentiful bass throughout the range. I’m certain the 807V’s aren’t anywhere near that bad. Beyond that, cranking more volume usually wouldn’t fix a problem like you’re having. It would make it worse if it’s a current delivery issue. I’m using 11 foot runs of 11g equivalent speaker cables.
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That means those speakers don't challenge that amp very much. I'd start looking at placement and room issues. A nicer amp isn't going to hurt your sound, but I'm not seeing an amp related technical problem here. |
Focal 936's and a First Watt F5. |
Try moving each one in 8 inches. |
Gochurchgo,
40 watts best described the class A envelope prior to me ratcheting up the bias of the amp quite a bit. It's currently a nominal 32 watts with a 64 watt class A envelope. Class A amps, especially push-pull, require behemoth power supplies because the amp is drawing full output power from the supply 100% of the time. You never see anything like that in class AB or class D amps. I also removed all of the output current limiting in the amp.
I say these speakers need that quality of power because they're pretty reactive. There's a big difference between 4.1 ohm and 2.8. You can readily crunch the numbers and see what kind of wattage you're speakers are calling for at a given volume and distance. We know they're something like 91dB/2.83V/M. So you figure out the actual listening distance and the required voltage is a square of that number. Then you plug that voltage and the speakers impedance low point into an ohm calculator like you can find online, and it'll tell you the current draw and watts. As long as that wattage is below what the amp will push, you're fine, and that wattage isn't going to be all that high given your speakers.
Hopefully I explained all that right. If I didn't, or it can be explained better, please somebody do so.
I agree with Czbbcl. These folks suggesting triple digit power for those speakers are out of their minds. |
No.... You're not understanding this problem right at all. Stop thinking about this as a wattage problem. Wattage is an abstraction and those calculators you linked to are not at all telling you what you need to know. Focal speakers are designed to be driven by a voltage source. That's how their sensitivity is described. Efficiency per watt is a very useless measure except for very, very benign loads. For the purpose of this discussion ignore watts completely. We're talking voltage source amps for voltage driven speakers so let's talk voltage and sort out the current next. Once you understand your voltage demands based on the speaker's sensitivity, then we can plug in it's impedance and determine the current demand. Only after we know the voltage and current requirements can we calculate the wattage, which may or may not make any difference based on the class and topology of the amp. |
Let me run you through the math and explain why a 30 watt class A amp would destroy your hearing with those speakers.
Here's how the math breaks down. 2.83V through an 8 ohm load draws .353 amp and 1 watt. If the speaker only ever presented an 8 ohm load with no reactance, calculating by the watt would work. But we know that speaker doesn't do that. We can calculate for that though.
Let's round the low point to 4 ohms for simplicity. Now we put the 2.83V through it at it's low point frequency. At a meter it's still making 92dB but because of the halved impedance it's drawing twice the current, .706 amp. That's 2 watts. The speaker doesn't respond flatly to power (watts) input. It responds flatly to voltage. That's why the amp needs to deliver current. If the amp doesn't deliver the current to support the voltage, the voltage will sag.
Now let's figure the distance. For each doubling of distance you square the power. So, at 8 ohm at 6 feet you need 4 watts. At 12 feet you need 16 watts. Halve the impedance and you need 32 watts to get your 92 dB. But, you're not listening in half sphere free space, nor to just one speaker. Each of those factors buys you about 3dB of reinforcement so now you're 32 watts is getting you more like 98dB. That's very, very loud. Hearing damaging loud. And that's assuming the music material is that loud consistently, which virtually no real music actually is.
A good class A 30 watt push-pull amp usually has an envelope of twice that power. I depend on that with my F5. It will belt out 64 watts into that 2.8 ohm load without a hiccup. And if I do happen to drive it even harder, the amp just transitions to class AB and keeps driving current. That nominally rated 32 watt amp has more than enough power to damage my hearing in minutes sitting 12 feet away. It's not going to do it at 110Hz, but nobody listens to test tones. That amp effortlessly vibrates my chair and rattles the walls.
I hope that math makes some sense. |
Awesome!
All of that said, class D and AB amps have nowhere near the headroom most class A amps have. A class AB or D amp's rating is usually a pretty hard limit produced by the limit of the power supply to drive voltage, current, or both. The reason your Marantz peters out at 45 watts is that's the limit of the voltage it can reliably push into 8 ohm.. It reaches up 70 watts at 4 ohm because the power supply has some reserve capability, but not much. The power supply in my F5 will swing 150 watts reliably before it melts the outputs or pops the fuse. You rarely see class AB or D amps built like that. And there are guys building out Aleph J's and F5's with dual power supplies and making real monsters out of them for less than you're looking to spend.
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I'm not going to say you NEED good class A amp. I highly recommend them though. I built my amp and tweaked that thing for months until it sounded just the way I wanted. I don't have the best speakers on Earth, nor the best amp, but they're probably better matched to each other than most speakers and and amps out there and that makes up for a lot. |
I would say it's not related. That's not even a tough load for an AV receiver. Maybe that's the voice of the amp, a lump in the damping factor, or some odd convergence of interactions. |
I really don't think that's it. My F5 is connected to the wall through an 18g power cable I obtained from Good Will for precisely 1 American dollar. Authoritative bass is not a problem. |
