Subwoofer Crossovers

Guys, just interested, how many of you are using both high pass on the mains and low pass on the sub? And if you are, what are the speakers concerned and what's the crossover frequency and slope?

 

I preferred the sound without high pass on the mains.

 

60 hz, 2th order on mains, 4th order on sub...

Standard AV way, it integrates very well if the xover is good and the main speakers handle the choosen frequency at ref level... :MILD:

If the xover isnt good enough do as 7_V, if the speakers dont have full energy at 60hz, choose higher freq...

 

Antonio,

I was reading an old Soundstage article the other day about integrating subs for music and it was quite surprising.

Here's a summary

So given that my little Proacs give out very little below 60hz, I thought I'd experiment with crossing over at 120hz, something the JBL's have no problem with, being pretty flat from 100hz to 400hz. The results were impressive. I have lost a lot of the character of the Proac, the warm cuddly bass that results from the port induced peak centred at 90hz. Instead I have a very solid sounding combo that seems effortless in the bass. This makes sense to me. Why run the mains close or even below their resonance when a higher cut off should substantially reduce the distortion of the small mid/bass unit?

The only problems are if a) you actuallt like the bass bloom that the manufacturer built in to the response, or b) you use a HT Processor or Receiver that only provides mono sub outputs rather than properly designated left and right.

 

That doesnt go against what I said, I did realize that the main speakers have to be strong at the xover point, my previous Concertos that are supposed to go down to 40hz didnt integrate well at 50hz, the EAII wich go to down to 35hz, but with lots of "energy" do work well with 50hz, but now that I have the choice of 60hz, it works even better...

Above that, even 80hz, doesnt sound right to me, and as I have two subs, it has nothing to do with directionality, but, I feel, "speed", the sub just doesnt sound right at those frequencies...

I guess one important factor is to be under the port's ressonance frequency...

 

I would be interested to hear what happens with alternative subs crossed over at 80hz in your system. It rather sounds like your subs aren't very good. As merlin says, even his giant JBLs will play beautifully up to 400Hz (although not as subs, obviously).

Way to go, Mike. Defy convention ... :boogie:

 

IME, ported speakers and subs do not integrate that well. You always seem to end up with a lumpy bass response with suckouts due to the out of phase port output. Michael, have you tried blocking the ports?

Neil

 

That's a good point, Neil and it makes sense. It probably accounts for why so many speaker/sub systems are so badly integrated.

Mind you, that being the case, I wonder why more Naimees don't go for subs. Their little floorstanders are sealed aren't they?

 

Interesting point Neil. In fact the port's output on the 1sc peaks at 65hz and is -6db compared with the bass driver at 120hz which may well explain why I get no bloom with the higher crossover. In effect, by high passing the Proacs, the port is no longer contributing a great deal.

Of course most subs out there have filters around the 120hz area, which I suppose means you cannot run them up to that point without the bass performance suffering some what.

It's always puzzled me why sub manufacturers limit them in this way.

 

My subwoofers are closed boxes, and reasonably good ones too, REL Strata III, and I have never heard subwoofers as well integrated, nor have any of the friends that listened, or at least so they say... :MILD:

 

Antonio,

I believe we are talking about the ports in your satellites. The tuning frequency of a vented sub enclosure should prevent it from interfering with the integration process.

 

Once one does, the rest follow. :sheep: :sheep: :sheep: :sheep:

 

My MJ Acoustincs Pro50 allows you to set the xover frequency as high as 240Hz. When I previously used it for music (via a hi-level connection to my stereo amp) I found the best xover position was around 100Hz which gave considerable overlap with my Dyns. The integration was absolutely seamless but the bass, whilst it did obviously go lower, wasn't quite as tight and controlled as with the speakers alone - much like Robbo said.

I haven't been using the sub for music for a while now but once I've finished my new amp I'm going to give it another go and wheel out the laptop, ETF 5 software, cables and mic/SPL meter to see what I can achieve.

Michael.

 

Wooah! Techy Just stick some huge drive units under your standmounts and tweak the level by ear - it's hugely entertaining

Seriously, were you using a highpass on the Dyns, cutting them at the 100hz?

I've just laughed all the way through a Spongle track

 

You are right, but the EAII have passive radiators, wich are not as bad as holes...

Anyway, as they go down to 35hz and the CC2 to 25hz, xover at 60hz is about one octave higher then the port ressonance, so I see no reason for, and dont hear any interference, I think Michaelab didnt either... :MILD:

From my experience with good subs with 10" woofers, I seriously doubt your JBLs sound good that high, particularly in a smallish room...

 

Ooh Dear Antonio, maybe you need some more experience

Remember I've had a pair of Rel Stentors amongst others and nothing comes close to these. Most commercial subs have appalling distortion figures, wimpy amplifiers & drive units, and poorly designed and implemented crossovers.

The JBL's have none of the above:MILD: (as you would say!)

 

No - I just had the xover freq. on the sub set at 100Hz (stricly speaking it's not a xover but just a low pass and I noticed that it's a fairly gentle low pass on the MJA Pro50). The signal going to the Dyns was unchanged (straight from the amp) so as a result there was a significant sub/speaker overlap.

Michael.

 

This lack of tightness and control comes from having more deep bass, not from using subwoofers per se. If there are no phase problems (as there might be with ported main speakers), there is no basic difference between the sub/main crossover point and any other crossover point on the mains.

Therefore, if there's a problem with control of the bass, it's nothing to do with the 'principal' of subwoofers. You could look to the positioning within the room of the sub(s), the quality of the subs themselves, the quality of the sub amplifiers and the cabling, which (amongst other things) should be as short as possible.

 

RELs (and plenty of other subs - especially HT-oriented ones) may use drivers that don't work so well up above the 120Hz range or thereabouts but that doesn't mean all subs don't. I had an ATC Concept 4 sub with a 12" driver rated up to 2+KHz, and it's used to very good effect in the Active 100s up to a x-over point of 380Hz.

Anyway, high crossovers are all well and good - as long as either you have a stereo pair of woofers located one each next to a speaker, or a single woofer located directly between your stereo pair. Any other position and the high crossover point is likely to make it blatantly obvious that the bass isn't coming from where it's supposed to.

It is an interesting idea, though one I would think that wouldn't be as necessary or useful for high quality sealed box speakers. Ported speakers roll off very steeply below the port's resonant frequency, so setting the crossover well above that is probably a good idea. Sealed boxes on the other hand have a nice smooth 2nd-order roll-off, so as long as they have good quality bass drivers, they should have a fairly smooth, even, extended response to well below the nominal -3dB point. So I would think it wouldn't be quite as necessary to set the crossover point much higher than that with a sealed box.

Anyway, interesting thread. Anyone else tried it out? With ported or sealed box speakers?

I would be happy to contribute... except I don't have my lovely sub anymore.

Dunc

 

I use a Linn Sizmik 10.25 with (ported) Linn Espeks. The processor (5103) provides a sub out and rolls off the feed to the mains. I don't know what freq but I have a feeling starting at 120Hz. I have set the sub to roll off at 50Hz and 12Hz. IIRC the Espek -3dB point is 30 Hz. I found this sub setting to be the best, certainly better than setting it to 80Hz.

IME so far (couple of weeks, sames as Tones) the sub gives better, cleaner, more tuneful bass (and of course deeper) than the Espeks.

I have a problematic room resonance broadly around 90Hz, and for whatever reason the current set-up cleans up this area considerably. The sub is just to the left of the left Espek, in a corner.

Re directionality, if I turn off the other speakers I can clearly hear where the bass is coming from on a frequency sweep, but with the full range on, characteristics like the thwack attack of a drum localise the sound where it should be. Even so, I would like to run stereo subs, and gain the extra power for things like the film Master and Commander, where cannons feature.