Yamaha PX series ??

Is this amp OK?
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Paddlsonic
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Yamaha PX series ??

#1 Post by Paddlsonic » Mon Oct 19, 2020 5:23 am

Any thoughts on the yamaha pX series power amps?

I'm looking at maybe two PX5's to get 4 channels of 500watts at 8ohms

I guess in particular running the LAB12 6 ohm drivers.
I've noticed if your running generic speakers not yamaha's etc you only have a choice to run at 8 or 4 ohms. Not quite sure how that affects performance in terms of the LAB12's

As always , any thoughts much appreciated.

Cheers

Grant Bunter
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Re: Yamaha PX series ??

#2 Post by Grant Bunter » Mon Oct 19, 2020 2:03 pm

Yamaha have made good quality electronics for decades now, never heard anything but good from those who own or use them.
My only beef is I have always thought RRP for new seems somewhat excessive. If you can get 10% off it’s still 2K for 2 amps here.
It’s a class D amp with DSP. If you decide to go that way, you need a DSP amp for tops as well.
Or look for amps with no DSP and get a driverack.

As long as the load is above the minimum load an amp can do, it doesn’t care at all what the impedance is. Most companies use 8 and 4 ohms figures because everyone else does, apples to apples, but the amp just sees whatever impedance is thrown at it.
Having 8 and 4 ohms figures also allows some assessment of linearity in output.
Valve amps care about impedance...
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SethRocksYou
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Re: Yamaha PX series ??

#3 Post by SethRocksYou » Mon Oct 19, 2020 2:33 pm

Yamaha PX Series Specs

The way they rate their power output is interesting to me. At least they state how they achieved the figure (20 msec burst at 1kHz). But, it's difficult to calculate what they're able to put out continuously. 500 watts at 8 ohms is 63volts (SqRt of watts x ohms), which is sufficient given your 50volt limit... but there's not enough information to say whether it would provide 50 volts continuously. Probably would be close enough.

The DSP looks to be okay. Wasn't able to get a real clear idea of it's limiter settings from the manual and was a little confused by what they mean by "PX series models come with flexible onboard crossover, filters, delay, limiter and PEQ (fixed preset) functions as standard..." Is the PEQ fixed or flexible???

I'm sure a little internet digging or an email to their sales dept would answer all the questions though. If it's a fixed PEQ and/or does not have a configurable brick wall limiter, pass on it.
Last edited by SethRocksYou on Mon Oct 19, 2020 2:41 pm, edited 1 time in total.
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Bruce Weldy
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Re: Yamaha PX series ??

#4 Post by Bruce Weldy » Mon Oct 19, 2020 2:40 pm

SethRocksYou wrote:
Mon Oct 19, 2020 2:33 pm

The way they rate their power output is interesting to me. At least they state how they achieved the figure (20 msec burst at 1kHz). But, it's difficult to calculate what they're able to put out continuously.
Problem I've found (especially in Behringer and other lower end amps) is that the stated specs can only be reached by pushing the amp all the way into clipping. I did a video of a Behringer powered mixer a couple of years ago while trying to confirm its stated power. The only way I could get it to the stated voltage was to drive the channel volume into the red and the main output into the red....and I mean all the way. When I took the controls down to just below clipping, it was about half the stated voltage as I recall.

That's not usually a problem for tops.....but for subs, it is.

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Re: Yamaha PX series ??

#5 Post by SethRocksYou » Mon Oct 19, 2020 2:57 pm

Bruce Weldy wrote:
Mon Oct 19, 2020 2:40 pm
SethRocksYou wrote:
Mon Oct 19, 2020 2:33 pm

The way they rate their power output is interesting to me. At least they state how they achieved the figure (20 msec burst at 1kHz). But, it's difficult to calculate what they're able to put out continuously.
Problem I've found (especially in Behringer and other lower end amps) is that the stated specs can only be reached by pushing the amp all the way into clipping. I did a video of a Behringer powered mixer a couple of years ago while trying to confirm its stated power. The only way I could get it to the stated voltage was to drive the channel volume into the red and the main output into the red....and I mean all the way. When I took the controls down to just below clipping, it was about half the stated voltage as I recall.

That's not usually a problem for tops.....but for subs, it is.
I can't say for all, but I think the majority of amps actually indicate level and clipping based on input voltage and not necessarily a clipped signal. I noticed in a firmware update readme file for one of the Ashly amps I have, that there was a fix for a clipping light that was coming on too soon. This is one reason I'd love to get an oscilloscope on the output of some of these amps sometime and really take a look at when they indicate clip vs. when they actually clip. One amp I have from them is rated 200 continuous, yet the clip indicator comes on right around 35v without any load. I suspect the light isn't indicating accurately, but wouldn't be able to say without a means to test it.

Needless to say, it's a fools errand to try to get "rated" power out of any prosumer product now-a-days.
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Re: Yamaha PX series ??

#6 Post by Bruce Weldy » Mon Oct 19, 2020 3:28 pm

SethRocksYou wrote:
Mon Oct 19, 2020 2:57 pm


Needless to say, it's a fools errand to try to get "rated" power out of any prosumer product now-a-days.
Yep, that's why I always suggest more stated wattage for subs. If you want to run a sub at 55-60 volts, don't trust a 500 watt rating at 8 ohms to handle it without clipping the input. Add about 50 percent to stay safe, then lock it down with the limiter.

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

Paddlsonic
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Re: Yamaha PX series ??

#7 Post by Paddlsonic » Tue Oct 20, 2020 3:57 am

yes, i thought amps just reacted to what was plugged into it rather than it trying to set an impedance.

I am still trying to get my head around the voltage part and so understanding the limiter side of these products. It'd be great to be able to play with one with my intended load to see what it can do.

From the comments, would it be better to limit a PX8 (800 at 8ohms) for the subs and then a PX5 for the tops?? Or just try the PX5 for the subs also??

obviously i don't want to blow the LAB12's by pushing them too hard...

Yep prices here Grant are brutal....Not sure yet a way around it as shipping from the US just about brings things even and then there's the voltage conversion unless a unit has a switch.

cheers fellas

Bruce Weldy
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Re: Yamaha PX series ??

#8 Post by Bruce Weldy » Tue Oct 20, 2020 8:09 am

I don't see in this thread which sub you have the Lab 12s in. The voltage you should limit to is different for different cabs. So, let's start there.

As far as understanding the voltage vs. impedance.......

Voltage is constant in the amp. The impedance of the speaker determines the eventual wattage. The reason that wattage is always advertised in terms of 4 or 8 ohms is because most speakers are built at either 4 or 8 ohms so it's easier to match up that way. If speakers were predominantly 6 ohms, that would be the advertised wattage.

The impedance ratings just give us a way to figure out how much voltage the amp puts out. Use this online calculator - put in the stated wattage of an amp and the impedance at which it's stated and the calculator will give you the voltage.

http://www.sengpielaudio.com/calculator-ohm.htm

Once you have the voltage number - it's easy to figure out which amp is needed based on the voltage limits in the plans for the sub you have.

Now, that said - we have to deal with the lying SOBs that market the amps - they often give out bad info. So, that's why it's good to build in some headroom. So, the two variables you really need to worry about are:

1. How much voltage will the amp put out before clipping
2. What voltage should the sub be limited to based on the design - that's in the plans.

The only reason you need to bring impedance into the equation is for matching a certain number of cabs to a single channel. You don't want to over-stress the amp by going lower than it's rating. If an amp is 4 ohm capable per channel, then 2- 8ohm speakers is all you should put on it in parallel.

There's a whole lot more to learn about impedance and speakers, but at this point - just wrap your head around voltage. The key is that we really only care about impedance as it's a number we use to determine the voltage of an amp and how many speakers we can hang on one channel.

So, you may ask....."Why don't they just give voltage ratings on the amps?" Well, they used to. Go look at spec sheets for amps made in the 70s and even the 80s....it's there on most of 'em. But, voltage is a low number and wattage is a high number.....so guess which one has been chosen for marketing purposes.

Hope all this will make a little sense.....

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

Paddlsonic
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Location: Australia

Re: Yamaha PX series ??

#9 Post by Paddlsonic » Wed Oct 21, 2020 4:17 am

That's all great Bruce, thanks for taking the time to explain it all to me.

I'll follow all that through and once that has sunk in, your right, it should make amp choice alot easier since i know what i'm actually looking for.
Thanks for the calculator too, invaluable.
The Lab12's are going in Tuba30's. Single in each.
I'm not sure at this point whether i will put more than one cab on a channel. Although i would like to look into the future and have the capacity to run cabs in parallel.

You wonder who they are marketing to, since surely most people looking for such type of amps would be interested in more than just the big numbers.
Sounds like the normal world to me......

Cheers

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