[dobias]

Gentlemen,
Would someone explain the reason a sub-woofer can have the "plate" amplifier mounted in the enclosure? I've been led to believe that vibration of amplifier's capacitors would cause distortion of the sound & that amplifiers should be isolated from feedback.
dobias

[Rob Babcock]

You're right, Dobias.  It's not the optimal place to mount an amp.  I guess modern Class D amps must be pretty durable, but examine the warranty of a typical sub- the driver is often warrented for 5-7 years while the amp is normally only covered for a year or two.  Tells you something, doesn't it?

[JohnR]

I've always wondered about this too 

[DSK]

Perhaps the distortion is more audible in the mid/high frequencies .... not a problem in subwoofers 

[Wayner]

Most warranties for speakers are 5 years, electronics 2 to 3 years..with almost every company.

Wayner

[twitch54]

You're right, Dobias.  It's not the optimal place to mount an amp.  I guess modern Class D amps must be pretty durable, but examine the warranty of a typical sub- the driver is often warrented for 5-7 years while the amp is normally only covered for a year or two.  Tells you something, doesn't it?

While I agree....food for thought , here's another take....Velodyne "DD" series of subs Warranty their drivers for five years and the electronics for three.

The other point to be made is put your hand or for that matter a glass of water on the cabinet of a well made sub while it is playing, guess what ??? .....still, is the word that comes to mind. Any sub that you can 'feel' the freq being generated is a poor sub, IMO.

[rockadanny]

All the more reason to get one from ACI - 5 year warranty ALL PARTS:

ACI Warranty:
For five years from receipt, Audio Concepts, Inc. will, at its option, repair or replace factory defective components. This warranty excludes products that have been abused, modified, or disassembled in any way. This warranty does not apply to products, which have been damaged in shipping. Audio Concepts, Inc. liability is limited only to the replacement of defective parts. No other liabilities or obligations are expressed or implied.

[denjo]

My CIAudio was 1 year warranty when about 16 days past its 1st anniversary one of the monos failed!! Really sucked!

What is more, the toroids hum like a motor boat!

[SET Man]

Gentlemen,
Would someone explain the reason a sub-woofer can have the "plate" amplifier mounted in the enclosure? I've been led to believe that vibration of amplifier's capacitors would cause distortion of the sound & that amplifiers should be isolated from feedback.
dobias

Hey!

   Why? Well, I guess it is mostly about cost and space. Strangely very expensive subs most also have amp built in.

Take care,
Buddy

[markC]

I think that the distortion heard from capacitors being vibrated would be subtle and @ low frequencies such as in a sub pretty much inaudible. That's why sub amp distortion specs are usually much higher than full range amps.

[JimJ]

The biggest source of distortion is still going to be the woofer itself...you'd have to have something really wrong with the amplifier to pass that

[ricmon]

I have been using the same sub-woofer for 10 years and it functions just fine.  One thing to keep in mind or at least has been my experience is that my sub is used to enhance my mains.  Thus they are not the sole source of the bass info but just support it so it never gets turn up much past it's 3rd notch.  It mostly stays at the second notch. So if it's going to be a music only sub that will be used to enhance the bass then it should last a life time.

[JLM]

Active speakers typically have this issue, but are still the primary choice of professionals.  OTOH VMPS subs are passive because of this concern (and so that Brian doesn't have to sell/deal with plate amps.  Note that most plate amps are pretty low quality compared to freestanding/full range audiophile grade amps.

[awe-d-o-file]

Most often the Sub maker buys an amp from another company or has one made to spec for them. Therefore they can't control the warranty on electronics.....or would have to pay more for a longer warranty. It's a money thing.

                                                                     ET

[darrenyeats]

A few points.

First I agree that it's best to not have the amp attached to the subwoofer. Some active subwoofer designs e.g. Linkwitz Thor have physically separate amps which I think is good.

Second, I agree that the feedback effects of vibrations are probably more audible in higher frequencies. But that doesn't mean they're inaudible in the bass. IME my integrated amp seems to benefit in the bass area from isolation treatment, for example.

Third, not every subwoofer I've heard has impressed me for music. The problem is group delay or in everyday parlance 'timing'. A well-executed active subwoofer is fine. But deep, even bass is not enough...it has to arrive on time...and some subwoofers get this last bit wrong.
Darren

[AmpDesigner333]

I was encouraged to contribute to this thread, and I have been designing amplifiers (analog and digital) for about 20 years.  I founded Digital Amplifier Company (www.DigitalAmp.com).  There are some good points in the posts here, and the contributions of all involved are greatly appreciated.  Mechanical vibration can have an effect on amplifier performance.  It is good practice to isolate amplifiers from vibration, but an amplifier can be designed to resist mechanical influence in several ways.

First, the quality of the circuit board construction must be top notch.  This reduces the possibility of failure due to solder joint breakdown.

Second, the chassis construction much be capable of withstanding vibration long term without any part coming loose.

Third, connectors and associated wiring must be made to take abuse over the years.  The punishment of use and countermeasures for combating the associated effects can be found in professional audio equipment.  I designed pro amps for several years.  The build quality of pro equipment comes from decades of experience with field failures.  After seeing what can happen in the worst of situations (concert applications, for instance), you get accustomed to building amps that address typical vibration related "mistakes" with construction.  This goes for Class-AB to Class-D to any other amp topology.

If the design is fragile, you're better off isolating it from the sources of failure.  Now, as far as the sound in a vibration-rich environment...  I personally believe that amplifiers can be deigned to have complete resistance to vibration related output differences.  This means that vibration should not change the output waveform of an amplifier.  Before you dispute this, think of equipment used in vibration rich environments, like boats, airplanes, and spacecraft.  This type of equipment is build to withstand vibration, and nothing more than durability is any different than something meant for consumer use.  To summarize, I don't think that vibration should change the sound unless there is an inherent problem with the design.

Let me say, also, that with components that are sensitive to vibration (tubes, for instance), this should be taken into account.  Solid state devices are pretty stable under intense mechanical vibration and this is reflected in their discrete component specifications.  You should be able to place a good quality amp on top of your subwoofer and have no problems.  If you have problems with the sound or experience a failure, the quality of the equipment is in question.  This makes me think the question is 99% reliability and not sound quality.  Thanks for reading.

Best Regards,
Tommy / DAC