What is the consensus on servo subs?

[KEW]

I have read that these are audibly faster subs. By fast I mean start and stop.
I know Paradigm has some on their high end and Rythmik makes some <$1000.
Serious feature or snake oil?
Thanks!

 

[skers_54]

My impression was that servos use feedback to reduce distortion, especially at high output. This makes them sound cleaner, which some people probably interpret as "faster". The "speed" of a sub is related to its Q, which is a function of the driver characteristics and enclosure design. High Q subs generally sound sloppy (aka slow) because the bass notes tend to ring out longer while lower Q subs are "faster". I think that well-implemented servos do provide audible improvement when distortion is present in moderate or more amounts but a non-servo sub can sound just as good when operated responsibly.

 

[mtrycrafts]

I have read that these are audibly faster subs. By fast I mean start and stop.
I know Paradigm has some on their high end and Rythmik makes some <$1000.
Serious feature or snake oil?
Thanks!

Read the Sub Myth thread at the top or here
http://www.audiopulse.com/know-how/subwoofer-driver-guide/myths-about-subwoofers/

especially #3

 

[mtrycrafts]

My impression was that servos use feedback to reduce distortion, especially at high output. This makes them sound cleaner, which some people probably interpret as "faster". The "speed" of a sub is related to its Q, which is a function of the driver characteristics and enclosure design. High Q subs generally sound sloppy (aka slow) because the bass notes tend to ring out longer while lower Q subs are "faster". I think that well-implemented servos do provide audible improvement when distortion is present in moderate or more amounts but a non-servo sub can sound just as good when operated responsibly.

Yes, servo subs control the THD but being a sub, THD is hard to detect, hence the 10% used to test them. Even above that some cannot hear it, and a some cannot hear 100% in a sub. Midband and highs is another story

 

[KEW]

Technically, fast is the wrong term.
When I said fast, it wasn't a matter of ultimate speed, but of responsiveness - the ability to stop and start quickly.
We generally consider a car that does 0 to 60mph in 4 seconds fast, but 60mph is not considered fast.
I think one of the arguments being made for servo is good acceleration and deceleration, to use the truly proper terminology.
Rythmik claims an "effective" Q of 0.3 whatever that means.
The question is has anyone listened to a servo sub alongside a normal, decent sub to see if there was a realizable difference.
Thanks,
Kurt

 

[j_garcia]

I haven't listened to them side by side, but I can say that I've heard 2 different 15" servo subs and when pushed hard they do sound noticeably more accurate than mine, however neither of them had as much authority at the bottom end as mine even though both claim extension as good.

I've heard a home build Rythmik 12" of a member her (Darien87) and it is a very good sounding sub. I use their A350 amp for my Tempest.

 

[ParadigmDawg]

I can't remember why but Chris and Andrew both told me that a "servo" is a bandaide for a bigger issue. Maybe one of them will jump in and reminds us why.

I always thought my Servo15 did a good job. It was an impressive sub.

 

[lsiberian]

Servo is essentially a way to prevent distortion in subs that are pushed toward their limits. It's not necessary on high quality drivers like PDawg's
and is a marketing gimmick on many subs. It benefits bad drivers the most. With a sub like PDawg's you get a lot more linear response than you'll ever use.

 

[jostenmeat]

I have read that these are audibly faster subs. By fast I mean start and stop.
I know Paradigm has some on their high end and Rythmik makes some <$1000.
Serious feature or snake oil?
Thanks!

As noted, there isn't faster or it would be playing a different freq, but there can be faster decay, and that should be easily noticeable.

Every sealed sub I think I've ever seen at the Rhythmik's price and up has servo. Whether JL Audio, Velodyne, Martin Logan, Paradigm, you name it.

A sealed sub has poorer efficiency, and so they might push the driver like mad with a very beefy amp, and then they try to control the distortions with servo.

 

[lsiberian]

As noted, there isn't faster or it would be playing a different freq, but there can be faster decay, and that should be easily noticeable.

Every sealed sub I think I've ever seen at the Rhythmik's price and up has servo. Whether JL Audio, Velodyne, Martin Logan, Paradigm, you name it.

A sealed sub has poorer efficiency, and so they might push the driver like mad with a very beefy amp, and then they try to control the distortions with servo.

What JL Audio design employs Servo? Trying to find more information on this.
I'd think with their new drivers it would be unnecessary.

FYI good reading on the subject can be had by searching for posts and wmax username using our advanced search feature. He addresses it in several posts.

 

[jostenmeat]

What JL Audio design employs Servo? Trying to find more information on this.
I'd think with their new drivers it would be unnecessary.

I think you're right. My bad. I incorrectly thought they did employ one. I guess just lots of EQing. Thanks.

 

[WmAx]

Servos are more useful with drivers that have poor linearity. Note that the best measurably performing drivers in the world actually are not servo controlled (TC Sounds LMS series). JL Audio, also, does not use servo technology. These drivers are so incredibly linear in respect to high excursion vs. low excursion behavior(s), that a servo would be of very little benefit. However, an average quality driver will have large increase in performance using a servo system due to the driver's mediocre linearity at moderate to high excursion levels.

-Chris

 

[djreef]

So riddle me this WmAx, since I have your attention, and maybe Lsiberian can also weigh in on this. Would there b a benefit to replacing a less linear driver in a sub that does employ a servo. I'm considering upgrading my old Velodyne FSR 1800 18" with something a little more efficient. I know these drivers are 'tuned' to their servos so I'm doubting it, but thought I'd ask before I did something costly. Oh BTW, congrats on breaking 5000 posts Lsiberian - do you like get a button or something for that?

DJ

 

[lsiberian]

So riddle me this WmAx, since I have your attention, and maybe Lsiberian can also weigh in on this. Would there b a benefit to replacing a less linear driver in a sub that does employ a servo. I'm considering upgrading my old Velodyne FSR 1800 18" with something a little more efficient. I know these drivers are 'tuned' to their servos so I'm doubting it, but thought I'd ask before I did something costly. Oh BTW, congrats on breaking 5000 posts Lsiberian - do you like get a button or something for that?

DJ

Your idea is fraught with difficulties. No experienced speaker designer is going to go backwards with a design.

You build a box for a sub not a sub for a box. So replacing your driver is a really bad idea.

You can sell your sub and pay someone to build a box. This wouldn't be a bad idea. A single kappa build would cost less than the sell.

Until you factored in Police costs and foundation repairs.

I hadn't even noticed. But I became a Spartan today! Woohoo!

 

[djreef]

Your idea is fraught with difficulties. No experienced speaker designer is going to go backwards with a design.

You build a box for a sub not a sub for a box. So replacing your driver is a really bad idea.

You can sell your sub and pay someone to build a box. This wouldn't be a bad idea. A single kappa build would cost less than the sell.

Until you factored in Police costs and foundation repairs.

I hadn't even noticed. But I became a Spartan today! Woohoo!

So, are they going to send you a red cape and an awesome set of abs?

DJ

 

[lsiberian]

So, are they going to send you a red cape and an awesome set of abs?

DJ

6-packs are old news. Here at AH we aim for KEGs

J/k. My body isn't made for abs. And I don't wear hats unless I have too.

 

[WmAx]

So riddle me this WmAx, since I have your attention, and maybe Lsiberian can also weigh in on this. Would there b a benefit to replacing a less linear driver in a sub that does employ a servo. I'm considering upgrading my old Velodyne FSR 1800 18" with something a little more efficient. I know these drivers are 'tuned' to their servos so I'm doubting it, but thought I'd ask before I did something costly. Oh BTW, congrats on breaking 5000 posts Lsiberian - do you like get a button or something for that?

DJ

It's a waste of time.

Design from the ground up; design the cabinet and amplification to work best with the driver chosen. At best, if it's a sealed cabinet, you can salvage the cabinet itself and use a better driver - but you will still likely have to use new amplification. Most built in amps on commercial subs, besides being underpowered, have specific hardwired EQ curves designed to work with the stock driver only.

-Chris