Ordered my SVS!

Originally posted by Crustyloafer
...for £700 you can get an MJ Acoustics Reference 1 which goes to 10Hz @ -6dB.

Where did you find the -6dB bit? I've seen them quote 10Hz but never quantify it with a +/-dB figure.

Matt.
 
I called them and asked the engineer there. I am a dealer for MJ Acoustics amongst others and am on pretty good terms with them.
 
Flat to 10Hz, that is very impressive for a relatively cheap sub. My sub is only rated to 15Hz so I might sell it and get an MJ sub cos I'm obviously missing out on some ultra low frequencies.
 
That's not flat to 10Hz, thats at -6dB output. Flat repsonse is about 14Hz I believe. The only thing is it doesn't go tremendously loud as it's not the most powerful sub by a long way. I plan on using one primarily for music purposes to accentuate a pair of Acoustic Energy AE1 Mk3s. It will of course also provide a good upgrade for my home cinema too.
 
Originally posted by Crustyloafer
That's not flat to 10Hz, thats at -6dB output. Flat repsonse is about 14Hz I believe. The only thing is it doesn't go tremendously loud as it's not the most powerful sub by a long way. I plan on using one primarily for music purposes to accentuate a pair of Acoustic Energy AE1 Mk3s. It will of course also provide a good upgrade for my home cinema too.

Even if they are "in room" figures (another trick to make figures look better than they really are) then I'd be surprised if it would go flat to 14Hz.

We are talking about a very nice sub here but at the end of the day it's a 10" cone with a 120 watt amp and a medium sized enclosure. So it's somewhere between an REL Strata 3 and Storm 3.

My guess would be mayble flat (+/-3dB) to 20Hz in room. Flat Anechoic (i.e. with no room loading) I'd be surprised if it was lower than 25Hz. Just my estimations of course.

Actually - just remembered - one of the avforums members did some measurements on the Pro 50 (which MJA claim 15Hz) in as near to anechoic conditions as he could. He measured 33Hz @ -3dB, 27Hz @ -6dB and 13Hz @ -22dB.

Here's the link: http://www.avforums.com/forums/show...71969&perpage=15&highlight=Quake&pagenumber=3

Matt.
 
MJ´s Pro 50 was measured in a anechoic chamber by Finnish "Hifi" -magazine. -6db point was 33hz. At 20hz it has gone down to -14 decibels.

Distortion levels were high - small cube & small woofer -combination has its limits... With 80db output (anechoic - in practice room amplifies sound a lot) distortion level was at usable levels with over 30hz. Under 30hz distortion level goes up. With 20hz distortion is over 30%. Pro 50 was reviewd as beeing a an OK small sub (3/5 stars) when using modest volume levels.
 
When people say "tuning a subwoofer", they are talking about a ported/venter bass reflex subwoofer.

The vent is tuned to a speific frequency and when this is tuned low like 20hz the gives greater effieceny on the deeper bass region.

The main dissadvantage is that a vented subwoofer will roll of extremly fast (24 db per octave) below the tuning point of the vent.

So this the last thing you want to do is tune too high like 35hz as you will have a huge peak at 35-45 hz almost no output at 20hz.

There are three laws to subwoofers, bass extention (Depth of bass), size od enclosure and power efficentcy. You can pick two but at the sacrifice of one of the others.

Have a large box (2-7 cubic foot in size) ported at around 16-25 hz, use a well built subwoofer driver and use a decent amplfiier between 250 and 750 watts of power.

Examples of this would be SVSubwoofers, HSU VTF, AdireAudio Shiva/ Tempest and Strike AV series.

The SVSubwoofers are excelent examples of a propery designed subwoofer.

The other way is to use a smaller box around 1.5-2 cubic volume, well built driver and use a Heafty amp 750-2000 watts with some EQ, bass boost or Linkwitz Circuit programmed in to make up for the much reduced F3 point. You can also use a clevler servo system to control the cone movement.

Examples are Velodyne CHT, HGS, Paradigm Servo 15. IPL Acoustics SW2/3.


Another method is to use a Infinte baffle this is where you build the multiple large subwoofer drivers into a large space like a attic ajoing room or large cupboard and efectivly greate a huge sealed enclosure. (Generaly size between 4 and 10 times the VAS of the subwoofer driver)

This if done corretly can give huge output right down to lowest depths.
 
The key to recognising a capable sub is in the tests and measurements. Its the basis for comparison with experiment controls.

Subwoofers are prone to severe distortion the moment we crank them up or when the bass goes deep.

I personally feel that MJA's claim that the Pro50 is able to to down to 15hz is highly suspicious. I've personally heard them myself and could hear distortion on movies soundtracks way even before it reaches my usual "movie" volume.

I'd take FR claims with lotsa salt until its been validated by numerous independant testers.

A sub I once had did have a rating of 18hz (-6dB). However, i found out that claim was valid for ridiculously low-volume (background music) listening; failing rather embarassingly in serious hifi organ listening or movie watching. At my listening volumes, 18hz info is recogniseable as serious port noise, driver flapping......... all tale-tale signs the sub is loosing control and steam.

I'd be careful in taking manufacturer's claim as gospel truth as who knows what agenda they may have (honest ot not).
 

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