Is there a good diy active sub xover?

[etcarroll]

I'd like to add my 10" powered, enclosed sub to my 2 channel system, intrigued by the thought of active xover for it, but they seem a bit pricy.

Was wondering if anyone knew of a decent diy active sub xover?

Gene

[richidoo]

Hi Gene,
By active, do you mean a Behringer type digital speaker management device, or do you mean a simple analog line level filter?

For external analog line level crossover filters:
http://sound.westhost.com/project09.htm
http://www.marchandelec.com/xm1.html

Your sub probably has low pass filter adjustments on the plate amp? Those are "active" in that they are line level filter feeding one amp for one speaker. That would be the thing to try first. What subwoofer do you have? 

[etcarroll]

Something that drops in between preamp and amp like the Bryston 10b-sub xover;

http://www.6moons.com/audioreviews/bryston2/crossover.html

Background: As a result of impending divorce a few years back, began thinking of building new system, always liked the Onyx Reference 3, figured they'd be good for ht and 2 channel. Dropped the Skiing Ninja master xovers in with platinum by-pass, no rez and a few other goodies. Then ex said she'd move out, not me. So, I should have bought dedicated 2-channel speakers, but who knew at the time. Also got an AV123 10" sealed sub, and as many did, my board blew up, so have a PE plate amp on it.

Recently auditioned another members Von Schweikerts, very nice, but for rock and jazz, not tremendously better. But big symphonic work, they really were better.

So, I want to relieve the Ref 3s from handling the bottom end of the bass, and amp as well. I figure that will allow them to reproduce rest of the sound spectrum better.

But, for price of the Bryston unit, I could almost buy my own used VS speakers.

And I'm selling the house in 2 to 4 years per divorce decree, and don't want to buy new speakers till then.

Thus - how to improve what I have already, for short money. I looked at the X1 this morning already, that's certainly a contender.

[shadowlight]

Maybe something like miniDSP

[richidoo]

The parts express plate amp probably has the filters you need to pull this off without buying another box. It would be better if you didn't have to put anything in the Onix signal path. But to get excellent phase coherence you will need to do that, and the Marchand will work fine. But try it without first, just using the plate amp filter controls.

There are a couple issues to consider when adding sub to mains.

Phase: As mentioned above, you want the subs to be in phase (phase coherent) with the main speakers woofers through the crossover band. This is what makes that bass detail, fast bass that you are seeking with the sub. This is not possible if you leave the Onix ports open because port phase twists like crazy. So you have to seal the main ports, then set the sub to 12dB low pass slope to match the rolloff of the sealed speaker, adjust the sub freq and volume to fill in under the mains by ear or with a SPL meter if you have one, then adjust the sub phase switch or knob so the phases are matched. Adjusting phase is simple if you set the phase to zero and put the sub at same distance from your ears as the main woofers. Up on a stand sounds even better...  Your PE plate amp can probably do all this.  The Bryston might give you more options or finer control, but in concept the sub controls do the same thing. Whether the sub filters are good enough quality parts for precision adjustments is another question, but probably so.

The other issue is the single sub in a stereo system. Assuming you're not buying another sub, you need to either sum stereo to mono, or choose R or L signal for the sub. Summing smears the detail, so I prefer to choose R signal because most classical bass is on the right side. Most popular and jazz is in the middle. Bass might seem too quiet because you only have half of it, but you can adjust the sub volume for that. Maybe you'll like summing better, for me it loses too much detail, especially with very detailed main speakers.

If you try the plate filters first, just run a speaker cable from the main amp right channel posts to the sub's speaker level input. This will prevent any small phase error picked up by the main amp.  If you don't have extra speaker cable you can split an RCA to the sub line in, no biggie, most amps are pretty flat phase anyway.

[etcarroll]

Gotta say Rich, I'm not hip to using the plate amp electronics, it feels like I'd have wasted the money I spent on the improved xovers in the Ref 3s. Obviously, I don't think much of the PE xover, though I have no concrete reason to think so.

But I guess I should try that 1st to see if it even makes any kind of improvement I'm hoping for. If not, then why continue.

[etcarroll]

Maybe something like miniDSP

hmmmmm, lot of reading there, but it may have a solution in there somewhere.

[richidoo]

The Onix passive crossover is still used from 100Hz up, so your new upgrade passive crossover is still used. The subwoofer crossover is only a low pass filter and is only used for the subwoofer. There would be no high pass filter for the main speakers, they run au naturale, just like now except without the ports... The Onix ports that you seal only function at very low freq. and everything above that is unchanged. Plugging the ports makes a rolloff that acts like 2nd order high pass filter. Your regular amplifier will still power the Onixes through their crossover, no change at all on the main speakers. The sub fills in the missing SPL of the low freqs caused by plugging the ports. The benefits are clearer bass without the ports' phase shifts, and lower extension than the ports can give cleanly.

You could run the sub with even lower freq low pass with steeper 4th order slope and NOT plug the ports, but the phase difference between sub and ports would not line up very well. Worth a try to hear the difference. Ports make a 4th order slope, sealed makes a 2nd order slope. The 2 slope settings of the subwoofer are intended to compliment either type of speakers.

You are right that you would not want to run the Onix through PE subwoofer type electronics. For similar reason, I think you would not want to run the Onix through ANY external crossover box, and you don't have to. Just add the sub to supplement and improve bass quality. The plate amp only affects the sub low freqs, where sound quality is not as important as on the tweeter. You don't hear "air" or much imaging way down low.  You're only concerned with level,  phase, slope and the plate amp controls let you adjust those.

So you take the signal off the Onix amp to drive the sub.  Then you adjust the sub controls to fill in the bass by ear. Simple!    I can help you by PM or phone if you want.

[Vapor1]

My MiniDSP sounds terrible by the way ... don't know if I got a bad unit or what, but it sounds like throwing a wet blanket over my speakers.  Most users however report no such problem. 

While not exactly what you're looking for, I've been thinking of trying one of the new Behringer iNuke DSP amps.  Take a look at this and read about all they can do. 

http://www.behringer.com/EN/Products/NU3000DSP.aspx

[mgalusha]

While not exactly what you're looking for, I've been thinking of trying one of the new Behringer iNuke DSP amps.  Take a look at this and read about all they can do. 

http://www.behringer.com/EN/Products/NU3000DSP.aspx

I love the name, might work well for driving a couple of subs. 

[rollo]

My MiniDSP sounds terrible by the way ... don't know if I got a bad unit or what, but it sounds like throwing a wet blanket over my speakers.  Most users however report no such problem. 

While not exactly what you're looking for, I've been thinking of trying one of the new Behringer iNuke DSP amps.  Take a look at this and read about all they can do. 

http://www.behringer.com/EN/Products/NU3000DSP.aspx

  But can "it core an apple ?" That is a lot of technology there.  My buddy sweras by this stuff. He keeps trying to persuade me to take the Berhinger plundge.
   For Bass management and crossover for the money and sonics as well it is the piece to buy. Not the amp but the EQ /crossover.
    Not saying the Amp is not desired. As an aside my buddy literally has owned in gear what we dream about. He has owned some fine sound, period. He swears by this Berhinger gear. Now using their mono preamp, two amps, and EQ for subs. Speakers are KEF.
    I take his word on this as I know what he is used too.



charles

[Face]

Behringer is great, if you don't mind having to replace it in a year or two.  Their reliability is known to be horrid. 

[etcarroll]

I may have a line on a used Bryston unit, we'll see.

[etcarroll]

Grabbed an unused Dahlquist DQ-LP1

https://sites.google.com/site/mpbarney/home/dahlquist-dq-lp1

Going to listen to it for awhile, then some mods to circuit board, and maybe replace RCA jacks, they're junk.

Have to add caps to bring it inline with my amps input impedance of 50k ohms. The LP1 is built to expect something in the range of 75-100k ohms.

[richidoo]

Gene, here are some nice caps you can use for your xo.

http://www.partsconnexion.com/capacitor_film_silvermica.html

.027uF = 27pF etc

So you could add 15pF at Cx location to maintain ~60Hz crossover as described in the manual.

Or you could get a few caps that allow 40-100 crossover frequencies in 10Hz increments to play around with. The higher the xo, the fuller but less resolved the sound will be. Raise the sub off the ground to improve it's resolution in upper bass. Stuff your main speaker bass driver reflex ports also might improve resolution around the xo range.

You should also replace the original .027uF cap with an audiophile approved variety like these silver micas, since it is in the signal path to your main speakers and will have a profound effect on the overall sound. Since the cap is so small your choices are limited, but silver mica is good choice.   

You might as well replace the power supply caps in it while you have it open, since electrolytic caps deteriorate with age. If you tell me their size and voltage I can recommend replacement parts. Panasonic and Nichicon are good quality. For power supply storage caps you can increase the value and voltage rating over the original size as long as they still fit.

There may be some other electrolytic caps in there. Depends on how crazy you want to go. Better listen to it first, and see if it sounds like you want.