Dear,

Here a question and a good tip the same time. Everyone that look for a affordable insane great sounding sub should listen to the Mackie HRS120.

What makes this sub so great is that it is lightning fast with real attack and impact (something that a lot of subs missing) and it have a straight frequency response down tot 19Hz. hence the Servo. This sub is not as boring sounding as some Servo subs can do, but it is also not as boomy as a lot of subs.

Link: http://www.mackie.com/products/hrs120/index.html

This sub can go real low and loud. Mebey not the last word in SPL but it will hit hard enough for most demanding situations and most important is that it is so much more tight and fast then so many other subs I ever hear.

My question is, does somebody else have experience with this subwoofer to share experiences?

Really I can not insist enough that if you search for a reall good sub give the Mackie HRS120 a listen.

Best regards,
Bas

Interesting, it has the +10db LFE boost that so many receivers don't provide these days, via HDMI or ext 6ch analog in.
What's the price on this?

Doesn't look too bad.

Although, if it is more than $600-$700 you would probably better served with a Rythmik Audio (http://www.rythmikaudio.com/) kit.

Just mount the kit in the enclosure of your choice...well known for excellent SQ and extension, bargain too.

Looks like $1,100 which isn't out of line considering it is a retail sub and not a DIY job. I didn't check but I wonder if they provide a certified FR graph with it like the do the HR monitors.

Looks like $1,100 which isn't out of line considering it is a retail sub and not a DIY job. I didn't check but I wonder if they provide a certified FR graph with it like the do the HR monitors.

Yes they have here on page 17

http://www.mackie.com/pdf/hrs120_om.pdf

This is also one of the not so many subwoofers with a real quality linear class A/B amplifier. It is really an incredible good subwoofer!

One other note is that it don't have an long throw woofer like JL-audio etc. But a PA driver with a "stiff" suspension and a big voicecoil of 4 inch. I don't know how they get it done but it is one of the fastest and tightest subwoofers I ever heard.

The FR look incredible as well hence the Servo ;)

Best regards,
Bas

.......and where is the Servo mentioned?

That sub looks very interesting. I have a pro sub with a very stiff suspension and a 4 inch voice coil and it is much faster than the SVS I just sold. I like the sound very much. I wonder how close the sound would be. Mine is a horn and very big. Much louder than the genelec according to the specs.

.......and where is the Servo mentioned?

"Built-in 400 watt FR Series low distortion, servo feedback amplifier"

And on page-15 from the owners manual you see the Servo in the block diagram. The feedback from the acclerometer tot the comperator.

Best regards,
Bas

I am also a sucker for THX. All my speakers and processor are THX. I was looking into an amp as well but I love mine. Now another THX sub. Interesting. I owned THX subs(Klipsch thx ultra 2) but settled on SVS and now 18 inch horn subs. Anyway, I have heard many good things about Mackie home theater systems.

Dear,

Here some more info.

http://www.zzounds.com/item--MACHRS120

Best regards,
Bas

AFAIK all their HR pro stuff is servo driven and uses PRs.

And on page-15 from the owners manual you see the Servo in the block diagram. The feedback from the acclerometer tot the comperator.

Best regards,
Bas

It is actually based on a positive feedback technology called "ACE" (which clearly shown on the block connected to the current sensing resistor), invented by Karl Stahl from Sweden, and subsequently patented. This technology was used by Audio Pro that the inventor was associated with. Now the patent has expired so everyone can use it. I still have the patent and the original technical paper written by Karl. He never mentioned it is a servo technique because there is no sensor involved. Several years after Karl published his technical paper on Journal of AES, another paper on J of AES showed how the frequency response "ACE" technique is more sensitive to voice coil temperature than conventional (non-ACE) speakers.

Brian

Rythmik Audio

That sub looks very interesting. I have a pro sub with a very stiff suspension and a 4 inch voice coil and it is much faster than the SVS I just sold. I like the sound very much. I wonder how close the sound would be. Mine is a horn and very big. Much louder than the genelec according to the specs.


Isn't a "fast" driver a tweeter? :D Seriously though, I've never understood how a subwoofer can be fast or slow. By definition, the notes that the sub produces forces the driver to move "slowly". I believe that people like the sound of certain subs (and maybe the Mackie sounds great), but should a well-designed sub that is working within its linear limits sound like the signal it is producing?
JP

Isn't a "fast" driver a tweeter? :D Seriously though, I've never understood how a subwoofer can be fast or slow. By definition, the notes that the sub produces forces the driver to move "slowly". I believe that people like the sound of certain subs (and maybe the Mackie sounds great), but should a well-designed sub that is working within its linear limits sound like the signal it is producing?
JP

JP,

It is interesting that you mentioned this. Isn't true that a "stiff" woofer has the problem producing low bass (that is, the fs is naturally high) and no bass is mistaken as fast bass???? :confused: Second which pro driver has stiff suspension? The only stiff suspension woofers are those for cars :D

Brian

Rythmik Audio

It is actually based on a positive feedback technology called "ACE" (which clearly shown on the block connected to the current sensing resistor), invented by Karl Stahl from Sweden, and subsequently patented. This technology was used by Audio Pro that the inventor was associated with. Now the patent has expired so everyone can use it. I still have the patent and the original technical paper written by Karl. He never mentioned it is a servo technique because there is no sensor involved. Several years after Karl published his technical paper on Journal of AES, another paper on J of AES showed how the frequency response "ACE" technique is more sensitive to voice coil temperature than conventional (non-ACE) speakers.

Brian

Rythmik Audio

Dear Brian,

Thanks for sharing this information. I thought you may call "ACE" servo because it involves (less or more) the driver output that get integrated in the feedbackloop of the amplifier.

Best regards,
Bas

JP,

It is interesting that you mentioned this. Isn't true that a "stiff" woofer has the problem producing low bass (that is, the fs is naturally high) and no bass is mistaken as fast bass???? :confused: Second which pro driver has stiff suspension? The only stiff suspension woofers are those for cars :D

Brian

Rythmik Audio

Dear Brian,

I think you judge to fast. The Mackie is capable to produce real bass, We can discuss if a woofer is fast or slow, I trust my ears ;) I'm an musician myself. There are 1000 ways how a kickdrum for example get reproduced by a (sub) woofer. There are also 100 ways how the attack of the bassguitar can get reproduced and seperated from the kickdrum. I define a "fast" subwoofer as an subwoofer that have no overhang, no blur and have and ligtning fast attack. I refer to my live gigs I playing in myself without reinforced drumkit. I don't say "fast" bass is impossible with big or longthrow woofers. I only comment on how the mackie sounds.

Almost all pro audio drivers from the big PA systems (meyer sound, EV, Dynacord, JBL etc.) have stiff suspensiondrivers. It is not impossible to get a decent low frequency response from such an units. Frankly most good PA systems with some good EQ-ing have far superiour bass in sense of attack and impact then most (if not all) home audio subwoofers ;) Those units have a different Q factor then drivers with a longthrow suspension. Nothing is perfect. And a stiff suspension woofer also have it's dissadvantages, but a stiff suspension woofer can be faster back into his zero position and equals systems with lower Q and high dampingsfactor amplifiers.

Stiff suspension woofers have an higher Fs. and need soem EQ or servo correction. (But if you take a good look at pro audio drivers with stiff suspension you will see that those days there are also types that have an lower Fs. then you might think ;)) But the same thing is the case for long throw woofers that get mounted in way to small enclosures. They also need Eq-ing or Servo to reach low. Longthrow woofers have high pwer handling because of there big peak to peak excursion. Stiff suspension woofers have high power handeling because of their big voicecoils.

The further the cone have to travle forwarts. The longer time it needs to get back into the zero position. It is all about timing, groupdelay and impuls response what makes a subwoofer sound fast or slow. Some of the commercial subwoofers have an terrible groupdely for example ;) and sounded terrible.

Before anyone make any judgement I can only say listen first to the Mackie. If you really like quality bass that also reach verry deep you won't be dissapointed ;) The mackie reproduce the low A of27,5Hz. with great effort and impact ;)

Best regards,
Bas

Dear Brian,

Thanks for sharing this information. I thought you may call "ACE" servo because it involves (less or more) the driver output that get integrated in the feedbackloop of the amplifier.

Best regards,
Bas

You can call it servo, but I am pretty sure Velodyne or Paradigm would disagree. Even if it is servo, but it is the least stable servo of any kind because it uses a "positive" feedback (all other sensor based servo uses "negative" feedback just in case you wonder). Under normal circumstance, a positive feedback will cause the circuit to oscillate. Even though in this particular case, it is the voice coil resistance keep it from oscillating, but over longer term, a lot of unexpected change can happen and stability is a problem.

My point is there is nothing new with the technology that Mackie uses. It is the old ACE technology.

Brian
Rythmik Audio

-

Dear Brian,

I think you judge to fast. The Mackie is capable to produce real bass, We can discuss if a woofer is fast or slow, I trust my ears ;) I'm an musician myself. Snip...


But, but... I am an engineer :D My comment has nothing to do with how Mackie sound. It may sound wonderful. It is addressed to two points: 1) there is no accelerometer in that manual, and 2) PA drivers are not stiff. There are a lot of reasons why Pro drivers do not have low Vas. Their Vas are relatively high because Vas affects efficiency. It is the last thing a pro driver designer would like to sacrifice. Let us go back to the physics fundamentals. Pro drivers are design for 4-10 cu ft enclousre. It is not like those enclosures in cars. Here is the number from JBL 2020H pro driver (a 12" pro driver with Vas of 65L). Is that considered as stiff? Another example, JBL 2227H pro driver, a 15" driver with Vas of 175L.



Brian

Rythmik Audio

Dear Brian,

Thanks for the input. I never knew about "ACE" but you are right and I found it.

http://www.audiopro.com/?id=180

Interesting though.. however you are right that it is a kind of tricky implementation since a loudpeakervoicecoil don't behave "static"
However as an pro audio manuafacter I can not imaging Macie want to take the risk and get a lot of units with oscilating or defective amplifiers return. I'm curious how they implement it. I will ask for schematics and share if someone is interested ;).

In this case I prefer then the Servo approach with a acclerometer.

Above don't change the fact that I find the HRS120 an outstanding sounding subwoofer. :D

Beste regards,
Bas

Dear Brian,

Thanks for the input. I never knew about "ACE" but you are right and I found it.

http://www.audiopro.com/?id=180



Bas,

You catch up quickly. Very soon you will learn more than I do ;) I really think we should give more credit to Karl Stahl for his contribution. At least people should know he invented ACE. Personally I think ACE is a milestone in audio. It is not so much of ACE itself, but the theory and framework he set up for putting ACE together. It is all part of the bigger scheme called control theory. It even finds its application into hard driver actuator control, and a lot wider applications without acutally knowing it.

Mackie is not the first company to claim a resistance cancellation scheme as servo. Infinity also did that to a car subwoofer they sell and people tear it apart and couldn't find any sensor on the woofer.

Brian
Rythmik Audio

I can't give you any advice on this sub specifically, however some general suggestions:

See if you can find a local pro shop to go hear it. One good thing about Mackie gear is that it is very popular in pro circles, so most pro shops carry a good lineup of it. Go audition thing thing for yourself, if it is practical.

In general Mackie gear is one I like, but don't tend to use a whole lot. I have an old 1402-VLZ mixer and the thing is just rock solid. It's been to hell and back and is still working. Mackie gear tends to be extremely well designed, very solidly built, and good on the features. Why am I not more of a fan then? Mostly price. You pay for all that, and you pay again for the name. Since I no longer use gear in anything but a home setting, Mackie stuff is a waste for the most part.

So I doubt you'd be disappointed with it, in my experience Mackie hasn't made a product that doesn't do what they say it'll do, however you might find your money better spent elsewhere. $1,100 (the going price on online discount shops for it) buys a whole lot of subwoofer from some other sources. You'll want to consider those other options as they may offer you a better sound, just less features and/or durability which aren't a concern in the home really.

Also the whole "servo" technology isn't something to get overly excited about. A servo is just a system with feedback, more or less. Most amps are designed this way these days, and most subs have an amp that exerts a great deal of control over the cone. You can test it through a simple tap test. Turn the sub off and tap the cone, then turn it on and do the same. You should notice that when it's on there's minimal noise since the amp holds the cone tightly in check with regards to the input signal.

Back to my original comment. I think you would be better served with Rythmik kit with better performance for far less money. You could almost use two of them for the same price.

The servo is important and can and often does make a very substantial difference though. Some subs and even companies are based on success of the servo, ala Velodyne, Paradigm, etc.

I don't like the term fast either but it was already used so I was replying to the person who used it. My sub does something different, It reacts faster, the signal dissapears quicker, I don't know what to use for terms. My sub was described as a stiff woofer, not my idea. BTW my sub has low bass, not no bass so I think it sounds fast. I have not eq'd my room yet but I can hit 100-102 db's at 10-15 hz, 110-115 db's at 16-20 hz. Not bad for a horn sub that has no bass.

I also agree with jpmst3 That DIY is a great way to get reference bass without the reference price, Not everyone can do this though. I wish I could, or one of the guys build it for me.

"Most amps are designed this way these days, and most subs have an amp that exerts a great deal of control over the cone. You can test it through a simple tap test. Turn the sub off and tap the cone, then turn it on and do the same. You should notice that when it's on there's minimal noise since the amp holds the cone tightly in check with regards to the input signal."

It would be interesting to to that test with the voice coil heated up a couple of hudred degrees.

A big benefit of servo is that it imposes linear behavior despite the T-S parameters changing wildly with temperature swings.

I own a Mackie HRS150, which is the 15" bigger brother to the 12" HRS120. It is now discontinued by Mackie (probably because it's a bit of overkill when matched with their mains) but it sounds great. It uses the same exact technology as the HRS120 but has more output across the spectrum. And yes, it's also THX rated and it included the factory spec'd frequency chart when I bought it NIB.

I use the sub with a set of Mackie HR824s and it makes for a killer 2.1 studio monitor setup for under $2500.

I run it pretty hard in my studio, almost every day, for a little over four years now. No issues at all with either the speakers or the built-in electronics. I'm very happy.

I also agree with jpmst3 That DIY is a great way to get reference bass without the reference price, Not everyone can do this though. I wish I could, or one of the guys build it for me.

MK, you can order pre-made boxes from Parts Express online or just have your local car audio shop build you a simple 3 cubic foot cube. Then just pick some textured paint and you are good to go...

PA drivers are not stiff.

Tell that to my B&C 12TBX100 driver. Its STIFF and a PA driver. ;)

Owned the Mackie too and paired it with HR626 monitors a couple of years ago. Great sub. The monitors, for the money, were something else though.

"Most amps are designed this way these days, and most subs have an amp that exerts a great deal of control over the cone. You can test it through a simple tap test. Turn the sub off and tap the cone, then turn it on and do the same. You should notice that when it's on there's minimal noise since the amp holds the cone tightly in check with regards to the input signal."

It would be interesting to to that test with the voice coil heated up a couple of hudred degrees.

A big benefit of servo is that it imposes linear behavior despite the T-S parameters changing wildly with temperature swings.

You both nailed the problem on the head. The cone control depends on the ratio of back EMF to the speaker impedance. If the ratio is high (say 1), it means whatever the amplifer provides, it goes to control that back EMF which is exactly the cone movement. The ratio is not a constant, so the control is very much frequency dependent. However, one thing is for sure, given the same driver, the voice coil resistance is the determining factor. If the resistance is high, we lose control over a larger bandwidth and sensor based servo is developed to address that problem. It has an equivalent effect of reducing that voice coil resistance from 3ohms to 1ohm or even lower and does not change over temperature (that is, it does not change even when the physical resistance goes to 10ohms). If you can feel the difference between completely open circuit (which is equivalent to having infinity voice coil resistance and therefore EMF ratio is 0) to say 4 ohms (where back EMF ratio is greater than 0), you should also appreciate the further change from 4ohms down to 1ohm (with back EMF to impedance ratio improves up to 4x). It goes beyond what your hand can feel ;) Nonservo systems can only do as much as what the physical voice coil resistance can do. It is the servo that can break that barrier. Of course, if one day superconductor becomes so cheap that it can be used for voice coil, I would argue there is no need for servo, until then.....

Brian

Rythmik Audio

Tell that to my B&C 12TBX100 driver. Its STIFF and a PA driver. ;)


I know. Not all engineers should keep their jobs. :D Come think about it, what is the purpose of having a low Vas? You get the same efficiency no matter you use a larger enclosure or smaller enclousure. Also there is no back pressure to linearize the spider distortion, which is a major source of distortion. I cannot think of one reason that a stiff drive is good for. The only excuse is the driver is not for "subwoofer", and instead is a midbass driver to work for frequency above 100hz.

Brian

Rythmik Audio

I do have a couple of usage questions on these subs: 1) how useful are the XLR inputs and outputs. In particular, it has XLR on both channels. I would have thought there is only channel needed, wouldn't those use these subs already have xover module? 2) is the master slave output/input very useful? Theoretically, we can have one master output controlling multiple slave units. But I wonder if a splitter at the master output would be better than daisy chain them.
Thanks in advance for the inputs.

Brian
Rythmik Audio

I do have a couple of usage questions on these subs: 1) how useful are the XLR inputs and outputs. In particular, it has XLR on both channels. I would have thought there is only channel needed, wouldn't those use these subs already have xover module? 2) is the master slave output/input very useful? Theoretically, we can have one master output controlling multiple slave units. But I wonder if a splitter at the master output would be better than daisy chain them.
Thanks in advance for the inputs.

Brian
Rythmik Audio

Brian,
XLR inputs are very useful becasue of the three wire system with forward and return paths for signal. Not to mention, it is just a more reliable connection and in general less noisy. Most high end equipment uses balanced I/Os for these reasons. Pro-amps and most equalizers...
Yes, generally most people already have the crossovers in their pre-amps and receivers. A crossover is continually becoming less useful, but there are always those rare situations.
Many larger HT installation make use of the master/slave sceanario. Most average users probably don't.

Brian,
XLR inputs are very useful becasue of the three wire system with forward and return paths for signal. Not to mention, it is just a more reliable connection and in general less noisy. Most high end equipment uses balanced I/Os for these reasons. Pro-amps and most equalizers...
Yes, generally most people already have the crossovers in their pre-amps and receivers. A crossover is continually becoming less useful, but there are always those rare situations.
Many larger HT installation make use of the master/slave sceanario. Most average users probably don't.

Joe,

Thanks for the input. If I only keep 3 XLR's: one single channel XLR input, one XLR output and one XLR slave input, would you say that covers most usage situation? The reason I would like to cut down on XLR number is really because the plate amp does not have a lot of space to work with. I am trying to get rid of binding posts and replace them with XLR and "others" more useful functions. But I definitely does not have space for 6 XLR's.

Thanks.

Brian

Joe,

Thanks for the input. If I only keep 3 XLR's: one single channel XLR input, one XLR output and one XLR slave input, would you say that covers most usage situation? The reason I would like to cut down on XLR number is really because the plate amp does not have a lot of space to work with. I am trying to get rid of binding posts and replace them with XLR and "others". But I definitely does not have space for 6 XLR's.

Thanks.

Brian

Yes Brian, I think 3 you mentioned would be plenty. It would be nice if you could offer two versions of the amps, one with speaker level in/out binding posts (limited quantities) and one with XLRS. The reason I say this is that some people have bookshelf type systems or other two-channel setups that might benefit.

Brian,

I'm just a mechanical engineer who understands Ohm's Law, but no circuit can actually lower the resistance of a hot voice coil, right?

You could draw a "black box" around it and additional (but let's leave ACE out of it, way over my head) circuitry and say it behaves as if the resistance were lower, but doesn't a servo simply increase the voltage drive to make the same current flow as if the VC were still cool?

IOW only the effect of the increased resistance is cancelled.

Brian,

I'm just a mechanical engineer who understands Ohm's Law, but no circuit can actually lower the resistance of a hot voice coil, right?

You could draw a "black box" around it and additional (but let's leave ACE out of it, way over my head) circuitry and say it behaves as if the resistance were lower, but doesn't a servo simply increase the voltage drive to make the same current flow as if the VC were still cool?

IOW only the effect of the increased resistance is cancelled.

Since you are a mechanical engineer, I can relate to you a news from EE times that a company developed a "negative" stiffness air bearing table (use for semiconductor fab for deep sub-micro technologies) It claim to reduce the resonance frequency by a lot (don't have the number so that the attenuation at 5 hz is 95%) or sort of like that. But how does it implement this negative stiffness system? It is a positive feedback system. So there is an equivalent circuit. This equivalent circuit simplifies the engineering view and description of what the system really does. It helps us understand how the elements of a system interact with each other. Does it really have an mechanical element exhibits "negative" stiffness? No. If it does, it would be a good source of energy because that negative stiffness can increase entropy and we know the natural law is the entropy always decrease, not increase (you will be a better judge of this statement).

Go back to the voice coil story, when the voice coil resistance increases, we are going to have reduced "max SPL", but the frequency response does not have to change. So there are two views here: physical view (plain passive system) and the equivalent system view under active system. But if the amp does not go into clipping, what is the proper way to describe what the system really does? The equivalent circuit. In addition, when you say there is cancellation, that means there is a negative resistance implemented in the system. It does not have to be that way. What if when I write down the close-form equation of the system, the voice coil resistance does not even exist in the equation? That is what happen when we have a negative feedback sensor-based system.


Brian

Rythmik Audio

Brian,

OK, I think I understand what you're saying.

BTW, entropy (disorder) always increases.

Thanks

Brian,

..Snip..

BTW, entropy (disorder) always increases.

Thanks

Thanks for the correction. I have forgotten that part of the physics.

Brian

Rythmik Audio