subwoofers and crossovers

[paulCJ]

I have a dilemna. I have an older Infinity subwoofer that has an active crossover box that takes the rca outputs from the preamp, sends the subwoofing signals to the self-powered subwoofer, and sends the rest of the signal path to the main amp. In this configuration the main amp and the main speakers do not see frequencies below approximately 65hz.

I also have newer SVS subs that can be connected into the system without an active subwoofer crossover box in the signal path. The SVS subs are built like tanks and can easily handle any torture test thrown at it. The system this way is full range and the subs handle only the lowest frequencies (below 32Hz). The connections this way could be either a preamp with XLR out to the main amp and rca out to the SVS subs, or 2 sets of rca connectors out from the pre, with one set going to the main amps and another set going to the SVS subs.

The Infinity sub cannot handle torture tests, but the system seems to sound better with the Infinity sub and the Infinity active crossover control box in the signal path. The SVS subs seem to have a bit of a muddy sound even with the subwoofer volume at -12db to -16db and the high sub limit set at 32Hz with a 24db decay.

Is this most likely due to the active crossover helping the system or potentially the old Infinity sub simply being a better subwoofer even though it is over 30 years old?

[admin]

Could be either or both.

I don't particularly like sending the signal through crossover's unnecessarily. My first question would be, do you really need the sub? I know it's giving your some low end but there is simply not a lot going on in the under 32 hz area to begin with. Maybe a few tracks here or there, but I would try to do some critical listening without the sub to see if maybe you can get away without one. That would be my first recommendation.

Can you hook up the subs so that the input is after the amp (using the speaker cable, not the RCA cables between preamp and amp)? I really don't like the audio being manipulated before getting to the actual amp. I would try to avoid the sub "robbing" the audio signal before the amp.

At the end of the day your ears should be the final determinant. Again, I would try to get the subs out of the system first. Second, I would try to get the crossover/subs to the end of the chain behind the amp, not in front of it. If that doesn't give you superior results I would stick with what sounds the best. Sometimes what makes sense from a technical perspective doesn't coincide with real world application and you just have to trust your ears.

[paulCJ]

My speakers are far into the room, with the front of the tweeters 7' out from the front wall. Imaging is just the way I like it, and the system does not have enough bass without a sub. I understand your point of the sub's crossover box robbing the signal, which is why I am asking the question. Running the speakers full range and having the SVS subs NOT in the main signal path just doesn't sound as good as when the Infinity crossover is (unfortunately) in the signal path.

[admin]

7' out is pretty far from the wall with a conventional speaker (ie, not a bipolar or planar speaker). Any chance that if you put the speaker closer to the wall/corner you would get enough low end increase where you don't have to employ a sub?

BTW- what speaker are you using?

[paulCJ]

PS Audio FR20. The speakers LOVE the GAT-S2 preamp

[admin]

You need more bass than the FR20? Those are massive speakers with two nice 8 inch woofers. My god, I thought you were running some bookshelf speakers or something.

Ok, I have to ask. Is there something wrong with the placement of the speakers or is the amp not a good match? I just find it hard to believe that you would need to use a subwoofer for a pair of FR20. And I wouldn't be cutting off the low end being fed to those speakers with some active crossover as those are definitely full range speakers and I would argue higher "quality" than the subs.

The only other thing I can think of is that you just prefer a massively exaggerated low end. Have you ever done a frequency sweep with a calibrated mic to see if you are truly deficient in the low end or it's just your preference? I say this from personal experience as I have two setups in my home theater room. One for listening to music and one for movies. For movies I like an exaggerated low end. When things are blowing up in movies I like to feel them! But for my music I like a very clean audio signal. But for the movie setup I have the low end disproportionally set to higher via a sub than reference. It's personal preference.

And congrats on the FR20's. Really cool speakers. I'm a big fan.

[paulCJ]

Thanks! They are 7' out into the room, and imaging is pleasant with them out there. But a sub does help open up the sound. Having a sub allows the speakers to be out there for imaging, but will still play around to see if the sound can improve even more without a sub in the system.

[admin]

I would maybe say instead of "tweaking" the current setup, kind of go back to step one with some more traditional placement. The FR20's are truly the definition of "full range speakers". Really not a speaker where I would think, "oh, that's going to need a sub." Something is going on there and I can't put my finger on it. Maybe shove them back in the corners like most people do and start from there? Sometimes it's beneficial to start with a clean slate.

[paulCJ]

I did exactly just that. (I am missing bass, lol). I have another issue, am hearing a crackling distortion after about an hour of listening. I disconnected the sub and crossover completely from the system, and the same thing repeated 2 more times (crackling sound). I put my older PV10AL back in, just to see if the distortion returned (as in to test if the problem is with the amp), but there was no distortion, just the "yuck, the GAT sounds MUCH better". I don't know if the tubes in the GAT are bad or what. I have a full factory warranty on the GAT

[admin]

Funny, Paul McGowan from PS Audio literally talked about this very concern 5 days ago in his youtube video and even mentions the FR20 as an example.

https://youtu.be/3cb4Z2GT2DU?si=z-EjgbjDZVfqqb6V

[AnotherJohnson]

The tubes in the GAT are not “bad.” They’re just being tubes.

If it’s a true crackling sound, and not just normal noise floor raising hissssss, you might have a tube that is failing. Simple enough to replace. Replace the tubes one at a time and see if it solves your problem.

Once you’re used to a modern preamp, the flaws in any of the PV preamps become more apparent. In my opinion, it would be hard to go back.

Same with the amp. Teflon or no Teflon, an MV55 is not going to be as realistic as a good modern amp.

[paulCJ]

@admin, thanks for the link. Notice where Paul has the FR30's in the room (quite a bit out into the room)
@AnotherJohnson, yes is a specific crackling and not tube hiss. I have had tube hiss for 25+ years (generally small amounts of hiss that do not bother me), but this crackling is different, and starts up after about an hour of listening to music.

Just a few days, and I am already used to the GAT. I never thought I'd say this, but it was already rough going back to a PV series to see how it sounded on day 3. Now that I have the GAT, I cannot go without.
I have been enjoying the GAT-S2 to Levinson 5302 combo so much that I have not tried the MV-55 yet.
I was (and maybe still am) questioning about properly integrating a sub. Right now it sounds better to have the Infinity crossover box in the signal path, so that is what I will go with for now.

[AnotherJohnson]

You know, it could be a thermally sensitive solder joint or socket too. Or even a thermal issue with a resistor.

If there is a problem, don’t let CJ talk you out of a thorough bench examination under sufficient time and load.