[Ultralight]

Dave at Planet 10 has been incredibly helpful in answering some of my e-mails (thanks Dave) but I don't want to keep bugging him with questions....

So, my question here.  What exactly is a helper woofer for a full range speaker?  It was brought up while I was thinking of a subwoofer to take the load off a full ranger - say 80 hz and under.   How is a helper woofer different from a subwoofer - or are both really the same?

Thanks,
UL

[TerryO]

Dave at Planet 10 has been incredibly helpful in answering some of my e-mails (thanks Dave) but I don't want to keep bugging him with questions....

So, my question here.  What exactly is a helper woofer for a full range speaker?  It was brought up while I was thinking of a subwoofer to take the load off a full ranger - say 80 hz and under.   How is a helper woofer different from a subwoofer - or are both really the same?

Thanks,
UL

UL,

Dave's a good guy and I'm sure you're not bugging him. However, there are opinions on what difference exists between a "helper woofer" and a subwoofer. I just give you my take on it and others can debate it if they wish. A helper woofer is just there to flesh out the shortcomings of whatever is the frequency roll-off of the main speaker (single driver/ fullrange?). If your speaker normally has a fairly high roll-off or you want more powerhandling then the woofer takes over normal bass duties. That could be from 200Hz down to 45 Hz or even 35 Hz, with the right set up. A subwoofer is actually a specialized driver that is specifically designed to plum the depths of the bass regions. They are usually not too efficient, and usually start having problems sounding good at anything above 300 or so Hertz. They are best used at 80 Hz on down to 20 Hz or even a bit lower.

I don't know if that's a good answer, but it's a grey area at best and you'll hear different opinions. You now have mine.


Best Regards,
TerryO

[strider]

Terry's take on it is pretty much spot on with mine. I have a pair of 7 inch woofers per side crossed over at about 200 hz. IMO that 's a bit high to be called a sub; they also have a -3db point in the mid 40hz range, which I think would be a not too great showing for a true subwoofer.

Even though it may not be the purest implementation of a single driver system, I don't really care. It opens up the range of music that sounds good to me in my system, and that's what I'm after.

Ben

[planet10]

A helper woofer (you need at least 1 per speaker) does not plumb the depths like a subwoofer but goes higher and will integrate with a FR better. Typical XO between 80 & 400 Hz. All those mid-woofers capable of 25-40 Hz bass that often struggle to reach up to meet a dome tweeter, 2-4kHz make ideal helper woofers once relieved of the mid-top. Relief of doing bass lets the FR excel in the mid/top. The combo provides the potential to overcome a significant number of the shortcomings of both FRs & 2-ways with their evil crossover.

dave

[Ultralight]

Thanks TerryO, Strider & Dave/Planet10.

Dave, once again you manage to find and answer one of my newbie question.    Appreciate it.

As I've said before, one good deed begets another question...

I'm thinking of running my main speaker 80hz and up.  The helper woofer or sub is to produce 80hz and below.  The work to redirect the signals will be done by a miniDSP which supposedly does not degrade the audio at all - at least not discernibly.

Questions:

1. My thought is that one speaker reproducing 80hz and up (or maybe 100hz and up) gives a better sense of imaging and due to one driver producing that primary range.   The sound is primarily coming from one point.  A number of speakers can now easily do this it seems.   I can't for the life of me figure out why one would cross at 400hz.  Would that not be two drivers producing frequencies that are clearly directional and hence, affect imaging?

2. In the above scenario of 80hz 'cross', is there any reason not to use a sub that's capable of flat to 30 hz.  Or even better, if budget allows, down to 20hz?   And if one has a pair of sub, that serves the same function as a pair of helper woofer right?   The advantage of sub are that:

a. Many are self powered, hence no need for additional amps.
b. They extend pretty low.
c. A pair of decent musical sealed subs can be had for about $650 (i.e. Emotiva 10) and dispense with a second amp for the helper woofers.
d. Or a higher quality musical sub going down to 20hz can be placed exactly in the center of the two full range speakers, and 80hz and below is supposedly largely non-directional.

3. What are some example of drivers used by DIY community for helper woofers if one doesn't do a sub?

Thanks,
UL

[JLM]

UL,

I'm with you on points 1 and 2.  Can't help you with #3.

IME the term "helper woofer" is not widely used or defined, so it muddies discussion.  This is a problem in several aspects of wide-bandwidth (extended range) drivers.  To me, a design using a "helper woofer" as defined above is a 2-way design that simply has a lower than ordinary crossover frequency.

Note that there is precious little music below 32 Hz.  So going lower is primarily for movie special effects.  That last half octave is expensive and fraught with risk (rattling stuff in the room, WAF, neighbor issues).  A friend had speakers good down to 40 Hz and infinite baffle subs (dual 15 inchers with a big amp mounted in his attic).  He pulled out exagerated bass effects "music" and switched the subs in and out.  You could hear the difference, but would have been very easy to live without.  And I'm a huge believer of needing deep bass as foundational to the high end sound.  We even went outside where you could hear it through his attic venting, but barely.

There's lots of advice online for positioning subs.  (Middle of the front wall is never recommended.  Time delays and phasing issues are relevant with the very large sound waves coming from subs.)

I don't know about the Emotiva subs, but most of their stuff is well built, but mid-fi sound quality.  I'd shop around.  Check out ecoustics.com and look into Hsu, SVS, Rythmik, Epik, and Paradigm.  And don't forget our A/C sponsors.

[chrisby]

as JLM implied,  the hunt for the lowest official octave ( i.e. 20-40Hz) is fraught with many issues, not the least of which is that at those frequencies, the room is the speaker enclosure, so there is no universal strategy that will "work" for all venues.

Early in my DIY speaker addiction I built an Adire Shiva "sub" (based on a 3 cu ft ported alignment published on Dan's old website).  It was over-built as per the recommendations - double layers MDF, lots of bracing , and powered by a 120W or so plate amp whose name escapes me for the moment.  ( Kiega?)

Did it dig deep? - oh my yes
did it rattle the china and pictures on the walls?  - same answer

did it sound musical and seamlessly integrate with the speakers at the time (Vifa PW13  Dalines?)   absolutely not - to say it was completely unlistenable would be overstating it, but there was never any doubt where the trade off was taking place 

Over 10 years and at least 4-5 different iterations of "subs" later with a range of 6-12" drivers,  I've found the most natural balance in my HT system with a pair of corner mounted vented enclosures each employing a pair of approx 7" Eastech drivers, XO's at 110Hz to Alpair7s.  They are powered by a basic stereo power amp ( Rotel RB850).  Most current surround receivers have far more versatile bass management systems than the simple XO's built into any plate amp I've seen, and it's a lot simpler to build woofer enclosures without need to accommodate internal amp(s).

There are lots of drivers to choose from in the 6-8" range that have adequate performance to blend well with "full range" (really "wide-band") drivers.  While there are distinct advantages to placement flexibility of separate enclosures, they can always be integrated in a separate section of the same cabinet (a la Tyson), to create what is essentially a bi-amped, active  2 way with a very low XO to the mid/tweeter.   

Tang Band,  Silver Flute,  CSS SDX7,  Vifa,  etc - pick your favorite flavor, or even recycle something like I did with the Eastechs from Dave's stash. 

The music system upstairs is wife's domain - very zen and minimalist, and a pair of extra cabinets to fill in the bottom 60 or so and down that the dual EL70s or FE126E/FH3 I played with on the weekend can't reach is not gonna happen, nor would they be required based on the listening levels and average program material.  When I played some tunes the other day at mid 90s SPLs,( Loreena McKennit and Wailing Jennies)  she had to leave the building and play in her garden, 'cause I was "master-blasting" again.   

[PDR]

Agreed with the boxed sub, but not with all subs.

I have a couple of dual 12" designs that I was happy with for HT....but not so much for tunes.
I have speakers that incorporates a Rythmic servo amp with a couple of GR Research 12" drivers per side
in an OB H baffle....this is the most musical I have heard. They just dont load the room like boxed drivers. Lets you use flea amps for the main drivers and you can taylor the servos to your taste/room. The best of both worlds.