Yamaha powered speaker block diagram

[Multicore]

I may soon be in the market for a performance speaker and found myself looking at Yamaha's top-of-the-line DZR portable powered boxes and found this block diagram. I was quite impressed to find four stages of EQ plus delay in the crossover. But I guess that's just software once you've got a DSP platform in there.

Anyway, I figured some of you nerds here might enjoy looking at it and comparing it to other powered speaker units.

[Dante is Yamaha's digital interconnect protocol and you can buy these speakers with or without it, hence the dotted line.]

 

[AwesomeSauce2015]

Looking at it, it looks pretty standard for these kinds of powered speakers. I have attached a link to JBL's SRX812 manual. On page 3 it has a block diagram:
https://jblpro.com/en-US/site_elements/srx812p-spec-sheet
In my opinion, these are both their respective manufacturer's "high-end" portable powered point source speakers. Anything higher than these will be in line array territory, usually.
It is simplified compared to what Yamaha shows, but it is a similar setup. You have digital conversion after initial level adjustment, mixing, then user-adjustable EQ, the crossover section, and lastly the limiters.

One thing that is interesting is that Yamaha feels the need to specify that they use a FIR crossover between the woofer and mid/tweeter, and FIR EQ on the mid/tweeter, but not on the woofer. That is probably for delay reasons, though I can't be sure.
JBL, on the other hand, doesn't specify anything about their EQ or speaker processing, other than that it exists.

One other interesting thing is Yamaha's mention of dynamic EQ. Personally, I am not a huge fan of the idea of having dynamic EQ in a professional PA speaker. I want it to reproduce exactly what I send it, no matter what the level is. They could be using this as a way to get higher peak SPL numbers, if they are using it to band-limit the speaker at those SPL levels. IMO, that is kind of dishonest. If the speaker can't reproduce it's specified frequency range at the specified SPL level, than that is pretty sad.

Still, it is interesting to see these things, but I do agree, though this looks complicated, it's all just software once you're in the DSP.

 

[Multicore]

I was also curious about the Dynamic EQ and I feel that unless it is specified then it should be treated with some suspicion, as you did.

Another thing that interests me is to wonder how much you could improve a speaker like the KEF Amir reviewed today with this tech. I'm sure they are good speakers but why should the user have to do the active EQ and compensation when the manufacturer could do it properly as Yamaha shows here, per frequency band.

 

[Mnyb]

I was also curious about the Dynamic EQ and I feel that unless it is specified then it should be treated with some suspicion, as you did.

Another thing that interests me is to wonder how much you could improve a speaker like the KEF Amir reviewed today with this tech. I'm sure they are good speakers but why should the user have to do the active EQ and compensation when the manufacturer could do it properly as Yamaha shows here, per frequency band.

KEF has a bunch of actives for this very reason ..
But the market is conservative and they also sells a lot of passives .

 

[Multicore]

But the market is conservative and they also sells a lot of passives .

It's weird, innit. I bought my Meridian M30s when they were a new product on the market. (A friend is currently using them in his video editing suite.) But I guess that's a measure of how conservative the market is because when I replaced them as our living room boxes I ended up with passives.

 

[Multicore]

One other interesting thing is Yamaha's mention of dynamic EQ. Personally, I am not a huge fan of the idea of having dynamic EQ in a professional PA speaker. I want it to reproduce exactly what I send it, no matter what the level is. They could be using this as a way to get higher peak SPL numbers, if they are using it to band-limit the speaker at those SPL levels. IMO, that is kind of dishonest. If the speaker can't reproduce it's specified frequency range at the specified SPL level, than that is pretty sad.

Take a look at the reference manual pages 42 and 43.

I think you guessed right. Reminds me of VWs defeat devices from back when people could say the words "clean diesel" without getting laughed at.

 

[AwesomeSauce2015]

Yes indeed. Though I think that statement is referring to the limiters. Basically, what they are saying is that theoretically, the amplifier section can output 1000w to the LF driver, and 1000w to the mid/high driver. Therefore, they can say that the speakers are "2000W" speakers.

However, anyone who has done any research into speaker design would know that putting 1000w into a compression driver tweeter (of this size class) will fry it.
For example, the JBL PRX812, while not a direct competitor to this speaker (That would be the SRX800 series), uses the 2408h-2 compression driver, and the 272G 12" woofer.
It also claims that it uses a 1500W amplifier, but that it is a dual-750W amplifier.

While I don't doubt that the woofer could possibly handle a 750W amp, I know for a fact that the 2408H-2 cannot. A while back, I asked JBL for the power ratings for that tweeter, and the response was basically that it is a 25W RMS part. 25W-RMS means 50W "Program power" and 100W peak. Nowhere near 750W.
So realistically, the JBL PRX812 is a 750W+100W (peak) speaker, where the limiters keep the 1500W amp from frying the tweeter.

So yeah, nothing new here. It's just audio manufacturers overly inflating their specs, again. The truth of the matter that most people in the live sound community know is that within a certain class of speaker, you can expect similar performance in terms of SPL output, regardless of what the "power rating" is.

However, back to the Yamaha's "dynamic EQ". Generally, when I see this, it is referring to volume-dependent EQ, like a "loudness compensation" setting.
While this may be desirable in a consumer audio system, where volume levels do change and you want to always hear everything, in pro audio it is up to the "sound person" to handle this. In fact, given that this speaker has user-adjustable EQ, we could say that the user may tune the speaker to have a given target frequency response in a room. Suppose that I tune it at say, 90db output, and I run concerts at 100db in the same room. If the speaker uses dynamic EQ, then I could end up fighting it when I run my concert, as my system tuning was not done with that in mind.

Either way, it is interesting, but given that I am a bit of a JBL fanboy (And the venue I work at uses JBL/Harman stuff), I don't think I will be using Yamaha's PA speakers any time soon. (Though I do use their mixers, which are really good.)

 

[Multicore]

However, back to the Yamaha's "dynamic EQ". Generally, when I see this, it is referring to volume-dependent EQ, like a "loudness compensation" setting.

Idk. I got the idea Yamaha offers those features in the User Control section when they are available. The DZR line is their most pro and least party and even tries to make it look as plain as possible.

The DXL1K for example is aimed less at SR pros and has a sorta version of the classic Yamaha LOUDNESS knob. Here it is called MODE (6) and is flat in the middle at MUSIC, low bass rolled off at SPEECH, and loudness boosted at CLUB. (These mini portable SR systems with a sub and line array interest me. But the FR is no better than the DZR10 and SPL is lower.)

 

[kemmler3D]

The dynamic EQ jumped out at me too. It's actually become a lot more popular in music production over the past 10 years, I generally see it as an alternative to multiband compression. But like others I am a little surprised to see it in a pro speaker. Depending on how it's implemented, you could use it for a lot of things... shaving peaks in the bass, loudness compensation, squelching resonances, or even mitigating loudness effects from harmonic distortion.

 

[gnarly]

One thing that is interesting is that Yamaha feels the need to specify that they use a FIR crossover between the woofer and mid/tweeter, and FIR EQ on the mid/tweeter, but not on the woofer. That is probably for delay reasons, though I can't be sure.

Yep. It's for delay reasons....or rather avoiding the extra delay that would be needed to implement FIR EQ on the woofer.
The FIR lpf going to the woofer requires significantly less taps, than the number of taps that would be needed to give sufficient frequency resolution for EQ's in the sub's pass-band.

 

[AwesomeSauce2015]

Yep. It's for delay reasons....or rather avoiding the extra delay that would be needed to implement FIR EQ on the woofer.
The FIR lpf going to the woofer requires significantly less taps, than the number of taps that would be needed to give sufficient frequency resolution for EQ's in the sub's pass-band.

Bingo. That's exactly what I thought.

RE: The dynamic EQ discussion:
I did some research and, based on what other forums are saying, it seems like the "Dynamic EQ" in this case is to restrict the bandwidth as the system approaches maximum output. In other words, it would shelf down the bass as the woofer approaches its excursion limit. It seems like Yamaha isn't the only one doing this too, and I wish more manufacturers would actually disclose whether they are using this and how it is implemented.
Of course, one other option is to design speakers such that they don't require this, ie, instead of having the 12" speaker play 40hz at 80db and 80hz at 120, we design it to only go down to 80hz, and require the use of a subwoofer.

 

[gnarly]

RE: The dynamic EQ discussion:
I did some research and, based on what other forums are saying, it seems like the "Dynamic EQ" in this case is to restrict the bandwidth as the system approaches maximum output. In other words, it would shelf down the bass as the woofer approaches its excursion limit. It seems like Yamaha isn't the only one doing this too, and I wish more manufacturers would actually disclose whether they are using this and how it is implemented.

I like to call any kind of processing that restricts bandwidth, or selectively limits excursion over a range of frequencies...... "level & frequency dependent, limiting".
I know the term dynamic EQ gets used in a lot of ways.

Hey, here's a fun project I did on a DIY 18" ported sub. Interestingly, excessive excursion at higher SPL was far enough above the subs low f-3 corner, it felt like a waste to simply limit the entire lower end.
So I built a "level & frequency dependent, limiter" using an open architecture processor that you do about anything with.
Here's the various drive levels and result response curves as SPL is raised.
The chart on the right is the maximum peak voltage allowed by freq.
Hope this wasn't too far off topic...and of some interest....

 

[kemmler3D]

Of course, one other option is to design speakers such that they don't require this, ie, instead of having the 12" speaker play 40hz at 80db and 80hz at 120, we design it to only go down to 80hz, and require the use of a subwoofer.

Approaching it from the other direction, you could say "We can use this limiting function to enable more bass extension at lower SPL, so some people won't even need to buy a subwoofer" - it can be a very nice feature depending on the use case. I do agree that being explicit about when and where limiters kick in would be very helpful, but in cases like that, if your competitors aren't disclosing that info, then your speaker looks less powerful in comparison, so it's a tricky game to play from the marketing side.

 

[AwesomeSauce2015]

I like to call any kind of processing that restricts bandwidth, or selectively limits excursion over a range of frequencies...... "level & frequency dependent, limiting".
I know the term dynamic EQ gets used in a lot of ways.

Hey, here's a fun project I did on a DIY 18" ported sub. Interestingly, excessive excursion at higher SPL was far enough above the subs low f-3 corner, it felt like a waste to simply limit the entire lower end.
So I built a "level & frequency dependent, limiter" using an open architecture processor that you do about anything with.
Here's the various drive levels and result response curves as SPL is raised.
The chart on the right is the maximum peak voltage allowed by freq.
Hope this wasn't too far off topic...and of some interest....

Out of curiosity, which processor did you use?

 

[gnarly]

Out of curiosity, which processor did you use?

A Q-sys Core 110f.
I just went back to look at the schematic, to refresh my memory of what i did.
I see i put in both an excursion limiter for the 50-65Hz region, and a high-pass limiter. Each limiter has it's on trigger level, so it let the ported sub operate essentially operated without any electrical high-pass until needed.
Let's it behave closer to a sealed sub's phase/group delay when at normal listening. And still stay protected when cranking.

 

[Multicore]

RE: The dynamic EQ discussion:
I did some research and, based on what other forums are saying, it seems like the "Dynamic EQ" in this case is to restrict the bandwidth as the system approaches maximum output. In other words, it would shelf down the bass as the woofer approaches its excursion limit. It seems like Yamaha isn't the only one doing this too, and I wish more manufacturers would actually disclose whether they are using this and how it is implemented.
Of course, one other option is to design speakers such that they don't require this, ie, instead of having the 12" speaker play 40hz at 80db and 80hz at 120, we design it to only go down to 80hz, and require the use of a subwoofer.

I like to call any kind of processing that restricts bandwidth, or selectively limits excursion over a range of frequencies...... "level & frequency dependent, limiting".
I know the term dynamic EQ gets used in a lot of ways.

I think such processing could be appropriate if we understood it as a protection feature, akin to soft clipping but basically linear. Now, the way that Yamaha put it on the block diagram outside of a box controlled by PROTECTION LOGIC kinda gave me the idea that the Dynamic EQ is not protection but I see now that's not logical (sorry). And it could be especially appropriate for an integrated system like this in which the limiting can be carefully tailored to fit the drivers. But Yamaha really need to specify it a bit before we could judge if it is appropriate for our application. (I'm pretty sure it's appropriate for mine.)