Subwoofer Tests: SVS, Paradigm, Velodyne and more.

[Brian Tatnall]

Hey guys,

I stumbled upon this resources the other day. I thought it is definitely worth sharing.. It is best collection of home audio subwoofer tests I have come across so far. If someone is trying to find how to properly test a subwoofer, this is how you do it.

SVS: PC Ultra
Paradigm: Servo 15
Velodyne: DD-18


More HERE

My apologies if you've seen this before. If there is a better resource, please post a link, since I'm always looking for testing done by people other than the manufacturers.

 

[mike.e]

Also 'way down deep' Article

http://audioroundtable.com/HomeTheater/messages/78.html

In this multi-part review, home theater designer Keith Yates gets down and dirty with some of the most ambitious subwoofers on the planet. Six months, 5000 measurements, four dozen batteries, three sore backs, and two big bare spots on the lawn, all for one thing: to get to the bottom of the bottom end, to separate Real Wallop from Codswallop.

 

[SpeakerBob]

Interesting links. I think the avtalk one has upset some people on avs though

Mike.e Have a look at the dd18 graphs here:

http://www.ultimateavmag.com/features/1004way/index4.html

Somethings not adding up. The freq response graph shows the 115dB and 110dB plots having the same spl as the 105dB plot at 21 Hz. Therefore the power compression graph should show the 110db plot as having 5dB power compression (yellow plot), and the 115dB plot as having 10dB power compression (red plot)

The power compression graph looks wrong to me....

Cheers,

Rob.

 

[mike.e]

Rob: After skimming through the article,what you say makes sense. But,what could be happening is the they are measuring ELECTRICAL output not acoustic,revealing the electronic protection circuits which have Dynamic EQ/shelving type filters.

Hah just realised that this is the THIRD 'way down deep',I must find the second aswell!

LOL 117% THD

An externally hosted image should be here but it was not working when we last tested it.

http://www.ultimateavmag.com/news/050704yates/

 

[SpeakerBob]

2nd part :

http://www.guidetohometheater.com/speakersystems/704way/index.html

Mike I believe the dd18 'power compression' is electronically caused. ie: the servo circuit cuts back the excursion to lower distortion / prevent over excursion. Still the graphs don't look right to me..

The graphs were all acoustic measurements I believe.

Cheers,

Rob.

 

[Bass-Depth]

I don't believe that the SVS-Subs are capable of the same high output levels of the Velodyne,but how is it possible that the DD-18 plays so deep,(What is the x-max of this driver???)

Would be interresting which of these super subs is capable of more than 120dB @ 30Hz 1m measuring

David

 

[simon5]

SVS subwoofers are quite capable beasts. They are quite large subwoofers, that's why they perform so well.

The DD18 excursion is probably very very large. It's also servo controlled for extended depth.

 

[BassAwdyO]

I'd like to see a comparison of those to say an Adire Tumult with 1000watts in a say 4 cubic ft PR alignment tuned around 15hz

 

[simon5]

I'd also like to see a comparison between them and the subwoofer I built to see how far it is from them hehe!

I know it's not fair, but the subwoofer I built is quite capable, reaching 16 Hz at around 116 dB SPL in room. So I guess outside like they are testing, it would be around 105 dB. Just to check for fun the distortion levels graphs. That way I could know how real that 16 Hz is hehe!

 

[BassAwdyO]

I think the ported or PRed tumult in 5 cubes could do 110db @15hz outside....

 

[mike.e]

What Im interested in is the velodyne servo feedback circuit,how it acheives such linearity compared to the other woofers. From what Ive seen it takes a good system to lower system harmonic distortion appreciably.

 

[rcw]

re servo

Philips had a similar system in the 70's, this used a velocity transducer mounted on the front of the voice coil I have forgotten the details of it.
At the time there was much discusion how you could do this by other means and the simplest way is to take a signal proportional to the back emf from the top of a resistor connected between the driver and ground, the second coil on a dual coil driver is also a possibility.

 

[SpeakerBob]

A few years back I read an article about the phillips speaker. I think it was called a motional feedback speaker. (read it in HI-FI World I think)

I think the velodynes use an accelerometer in the dust cap as a sensor. I remember about 10 years ago velodyne released a 10" servo car sub driver that came with an electronic box of tricks that sat between the head unit and amp. The reviewers loved it, but I think it cost about £900 or £1200....


The servo subs do sound excellent. My friends got the Martin Logan Descent. 3x 10" drivers. In room sounds excellent. I was surprised by the amount of output from 'just' 3 10" ers.


Rob

 

[mike.e]

rcw: Ive read the EW article that used the 2nd VC as a pickup,it seemed to work in this case - the results werent too scientific.

Many seem to agree that making a good pickup + feedback circuit that doesnt oscillate is difficult.

 

[rcw]

re feedback

Yes Mike, you have to be sure that the feedback is always negative other wise you end up with an oscillator.
Matlab has a control system toolbox that can model such things.