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Old 6th July 2011, 04:51 AM   #1
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Question Please help choose active X-over frequency

Greetings,

I recently purchased the Elliot Sound Products Linkwitz-Riley active X-over board. The X-over will go between the amp for my Vandersteen 3A's and an amp for a pair home-built subs.
  • Vandersteen advertises that the 3A's go down to 26hz at -3dB, with a "power assisted" passive radiator (probably 18dB/octave or steeper).
  • The subs aren't finished yet, but they should be flat up to atleast 200Hz.
So, clearly, I have a wide window for a 24dB/octave X-over. The problem with the ESP kit is that X-over centers are not adjustable. They are determined by the values of several resistors and caps in the PCB. I wondered if anyone had any suggestions about where to put the X-over frequency for best sound for both home theater and music. Presumably, I'll want both high and low-pass slopes down -3dB at the same frequency. The 8" woofers in the Vandersteens are fast and detailed, so I'd like to use them as much as is possible, but might transients become even better if I move the X-over frequency up? But then the woofers are heavy paper cones (Audio Concepts DV-12) not designed to handle mid-bass.

I figure anything between 36hz and 200Hz will work. Any advice?

-Byron
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Old 6th July 2011, 10:38 AM   #2
60ndown is offline 60ndown  United States
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most good speakers will play down to 80 or 60 hz,

so in my opinion a subwoofer doesnt need to play any higher then that.

and making a subwoofer play down to 16 hz so *dinosaur footsteps* are exciting is foolishness if at the same time that tuning makes bass guitars and drums 'sloppy'

35-15,000 hz is where its all at.

if i miss a few db of dinosaur footsteps once in a while, i dont care, i get all the accurate bass guitars and drums i want

can a subwoofer be designed and built to play from 10-80 hz well?

i dont believe thats possible with current technology..



so a subwoofer for music doesnt need to play any lower then 30hz (imo)
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Old 6th July 2011, 11:25 AM   #3
sreten is offline sreten  United Kingdom
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Vandersteen Audio 3A loudspeaker Sidebar 3: Measurements page 2 | Stereophile.com

Hi,

For modest volumes it appears subs are simply not needed.
Roll-off is 4th order, 6dB down at 23Hz.

L/R crossovers are 6dB down at the common c/o point.

I can't recommend a c/o point, seems too inflexible to me.
Sensibly though I'd say around 50 to 60 Hz might be ballpark.

rgds, sreten.
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Last edited by sreten; 6th July 2011 at 11:34 AM.
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Old 6th July 2011, 11:39 AM   #4
epa is offline epa  Netherlands
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imo 50 or 60 hz
fundementals wil be picked up by the subs,and harmonics(even from the lowest 5 string base gitar)are pickep up by your full range.
scond harmonics are usualy louder than fundementals.

but i.m not an hifi guru.
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Old 6th July 2011, 11:54 AM   #5
60ndown is offline 60ndown  United States
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yea id say you dont need a sub at all unless your room is very big.

your speaker already get down to 26hz !!!

http://www.vandersteen.com/pages/3alit2.html

DRIVERS

ACTIVE ACOUSTIC COUPLER
Long excursion, dual-spider 10" with die-cast basket and aluminum alloy cone
Heavy-duty 1 1/2" four-layer voice coil with ventilated aluminum former
60 oz. linear excursion magnet structure with focused field pole piece and copper rings
Range of operation: 26Hz - 35Hz1" critically damped metal alloy dome
WOOFER
Long excursion 8" with die-cast basket and curvilinear polycone
1 1/2" two-layer voice coil with ventilated aluminum former
40 oz. linear excursion magnet structure with focused field pole piece
Range of operation: 35Hz - 600Hz
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Old 6th July 2011, 01:56 PM   #6
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Several of you have pointed out the superfluousness of a subwoofer with the Vandersteen 3A's. The problem is that I've run out of things to build. I figure building an active X-over, another amplifier, and a pair of subs will keep me entertained for a while. The justification for the subs is that I've read that relieving the main speakers of the burden of deep bass improves the mid bass. Richard Vandersteen recommends against using them for home theater without a subwoofer, as they're not designed for that - though I suspect he's just trying to sell his subwoofer. Also, the room is huge. My house has an open floor plan, which means no walls across the entire length of the house. So it's effectively a 3-walled room with a vaulted ceiling. And we watch a lot of movies!

The subs are almost finished, so it's too late to turn back now. It looks like I'll go with a really low X-over point of 60Hz or so.

Thanks all for the input!
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Old 6th July 2011, 02:01 PM   #7
DrDyna is offline DrDyna  United States
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Even with main speakers that can play down low, it seems like sometimes due to placement in the room, they can be a little lackluster. Subs can be moved around to tune room resonances or reinforcement from walls.

Placing main speakers to have a great stereo image is, at least to me, an idea that often is at odds with placing speakers so that they have the best sounding bass response.

Edit: Oh yes, knocking the mains off at 50 or 60hz will definitely clean them up and lower distortion. Remember the Velodyne DF 661? I think 80% of the secret to their claim of low distortion was a series cap

Last edited by DrDyna; 6th July 2011 at 02:04 PM.
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Old 6th July 2011, 02:10 PM   #8
nmiljac is offline nmiljac  Germany
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I'd say - go on!

I added a pair of active subs to a system that was anything but bass shy. It is not about having more bass at all - good, low reaching subs bring a nice improvement of the size of soundstage and imaging. If you can, equalize and make them flat to 15 Hz or so.

My "Linkwitz transform" is a Behringer FBQ-2496 parametric equalizer. I figured out that it gives me more configuration options than an opamp filter.

The mains work full range, i.e. the subs are switched in parallel to main loudspeakers instead of having the crossover.
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Old 6th July 2011, 02:54 PM   #9
doug20 is offline doug20  United States
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Quote:
Originally Posted by 60ndown View Post
most good speakers will play down to 80 or 60 hz,

so in my opinion a subwoofer doesnt need to play any higher then that.

and making a subwoofer play down to 16 hz so *dinosaur footsteps* are exciting is foolishness if at the same time that tuning makes bass guitars and drums 'sloppy'

35-15,000 hz is where its all at.

if i miss a few db of dinosaur footsteps once in a while, i dont care, i get all the accurate bass guitars and drums i want

can a subwoofer be designed and built to play from 10-80 hz well?

i dont believe thats possible with current technology..



so a subwoofer for music doesnt need to play any lower then 30hz (imo)
Your assumption is incorrect. YES subwoofers can be designed to play very well from 10Hz or 15Hz to 80Hz. If someone wants to experience low, low bass in movies and still have clean bass for other content it can be done EASILY!! I have three different sub systems in my house that would simply prove your opinion wrong

btw,
Its fine for anyone to choose only 30Hz but there is content below 30Hz even in music. Just because that music is not your cup of tea does not make any subjective conclusion fact

My experience and opinion with the highest quality bass systems tells me 35Hz to 15KHz is not a high end system, its lacking several octaves

Last edited by doug20; 6th July 2011 at 03:01 PM.
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Old 6th July 2011, 02:59 PM   #10
doug20 is offline doug20  United States
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Quote:
Originally Posted by 60ndown View Post
yea id say you dont need a sub at all unless your room is very big.

your speaker already get down to 26hz !!!

http://www.vandersteen.com/pages/3alit2.html

DRIVERS

ACTIVE ACOUSTIC COUPLER
Long excursion, dual-spider 10" with die-cast basket and aluminum alloy cone
Heavy-duty 1 1/2" four-layer voice coil with ventilated aluminum former
60 oz. linear excursion magnet structure with focused field pole piece and copper rings
Range of operation: 26Hz - 35Hz1" critically damped metal alloy dome
WOOFER
Long excursion 8" with die-cast basket and curvilinear polycone
1 1/2" two-layer voice coil with ventilated aluminum former
40 oz. linear excursion magnet structure with focused field pole piece
Range of operation: 35Hz - 600Hz
You read that like it says there is bass...I read it and I think it will honestly suck for bass, hmmm a whole 1 1/2" voice coil....hold the presses!!

We live in different worlds of experience and one of us has seen distoriton measurements from main speakers that some people consider quality bass designs

Here are the facts, main speakers have issues with bass below 80Hz.

1. Always XO one octave above the F3 point of the design for the smoothest transition.

2. The placement of the speaker is seldom the best placement for bass response.

3. The box build, amp power, etc involved with the main speaker is not remotely good enough to a quality subwoofer build with its own box, own amplification, own DSP.

4. Multiple sub boxes is better then one box below 80Hz (even below 300Hz its important to correct room modes with multiple bass sources).

Last edited by doug20; 6th July 2011 at 03:02 PM.
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