Crossover Network for Subwoofer

[rabbitfyter]

I have a pieced together setup in my kitchen/living room area that I have been working on for a long time.

Currently, it consists of a separate preamp and power amp that is running to a subwoofer amp with a high level input. The subwoofer amp has an internal crossover and separate speaker level outputs for the front speakers and the subwoofer. It allows for setting of the crossover and the volume of the subwoofer.

Unfortunately, the subwoofer amp isn't of the best quality, and it's not really letting the other components shine. Additionally, I would like an equalizer to adjust the overall sound of the system.

What I am wondering is how the best way to achieve this.

Is it better to have the crossover at the speaker level, or should it be at line level, between the preamp and the power amps?

The subwoofer power amp also has a low level input, could I just put a Y splitter on the preamp output and have one side go to the speaker power amp, and the other go to the subwoofer power amp, or will that cause impedance issues?

Thanks

 

[Semanon]

Anything done at line level is cheaper and smaller, so that’s my preference.

Y cable should be just fine for this application. Or you could use the B-channel speaker out (if your amp has those).

Another suggestion is a DSP. A miniDSP 2x4 will provide a line level crossover and a bunch or equalizers. It’s computer programmed, so there are no buttons or knives, but it works.

 

[rabbitfyter]

Anything done at line level is cheaper and smaller, so that’s my preference.

Y cable should be just fine for this application. Or you could use the B-channel speaker out (if your amp has those).

Another suggestion is a DSP. A miniDSP 2x4 will provide a line level crossover and a bunch or equalizers. It’s computer programmed, so there are no buttons or knives, but it works.

Thanks

I do have a B speaker out, but I haven't ever turned it on; my power amp has separate power switches for A and B. I am worried that if I use B, it will reduce the overall quality of the sound, though that's easy enough to test.

Also have heard tales of people complaining about the sound of their main speakers after using a Y adapter to split off the pre-out to a secondary headphone amp, but perhaps there was some issue specific to their setup, I can't be sure.

Another thing I found is the old DBX 120 subharmonic synthesizers. This looks like a possible solution. They fit into a preamp by tapping into the tape monitor loop.

The DSP solution looks interesting, but it's also doing digital signal processing to what is currently an all-analog signal path (just cassettes and records), so I am kind of wary of that.

 

[swechsler]

The subwoofer power amp also has a low level input, could I just put a Y splitter on the preamp output and have one side go to the speaker power amp, and the other go to the subwoofer power amp, or will that cause impedance issues?

No, line level inputs/outputs have a high impedance. Using a Y splitter is a common way of doing what you want.

 

[swechsler]

I do have a B speaker out, but I haven't ever turned it on; my power amp has separate power switches for A and B. I am worried that if I use B, it will reduce the overall quality of the sound, though that's easy enough to test.

Using the B output is the same as connecting the subwoofer and mains in parallel off the A output. Shouldn't affect the sound at all.

Another thing I found is the old DBX 120 subharmonic synthesizers. This looks like a possible solution. They fit into a preamp by tapping into the tape monitor loop.

I have a couple of these. You can potentially use it as a sub crossover, but you'll want to connect it between the preamp and amp rather than to the tape loop. Otherwise the sub out will not be controlled by the preamp's volume.

 

[gadget73]

I'm using a stand-alone sub amp with it's own crossover, but off my second set of preamp outputs. Mine are just parallel with the main set, so electrically its like using a Y splitter. I'm running the main amps full range though so whatever goes on inside the sub crossover doesn't have any effect. Could probably use the DSP in a similar way, having it just handle the subwoofer crossover points.

I've actually been wanting to find a sub crossover that is just in a bare board form. I've got a DBX sub amp that has a non-adjustable internal passive crossover. I'd love to gut that part of it and stick something in there that can be easily adjusted so I can make it a useful piece of equipment.

 

[rabbitfyter]

Thanks

Using the B output is the same as connecting the subwoofer and mains in parallel off the A output. Shouldn't affect the sound at all.

I tried it and it sounds "normal," but it's a bit muddier because now the front speakers are getting all the low stuff. The front speakers I'm using sound great, but they are weak at lower frequencies and effected by this, I definitely want to get a crossover in there somewhere.

I have a couple of these. You can potentially use it as a sub crossover, but you'll want to connect it between the preamp and amp rather than to the tape loop. Otherwise the sub out will not be controlled by the preamp's volume.

In reference to the DBX 120 units, there seem to be a number of variants, mostly the older DBX 100, 110 units, and then the DBX 120, DBX 120X and the DBX 120X-ds. Do any/all of these function as an actual crossover (limiting the low frequencies to the main mix speakers) or do they only boost or otherwise effect the bass output?

 

[nerdorama]

You could try these inline passive hi pass units in the pre out line to the main speaker amp and feed the sub amp directly from the pre. They are available in an range of corner frequencies.
https://www.parts-express.com/FMOD-Crossover-Pair-100-Hz-High-Pass-266-274

There are also a number of pro/semipro active crossovers that are reasonably priced from Rane, Art Audio, EMB and others. Might look at some of those. Here are just some examples. You would want to look at the user manuals to know the capabilities before ordering.

https://www.amazon.com/EMB-CROSSOVE...sover&qid=1653579452&sprefix=,aps,140&sr=8-10

https://www.amazon.com/MUSYSIC-MU-C...ssover&qid=1653579482&sprefix=,aps,140&sr=8-8

https://www.amazon.com/ART-CX310-2w...ssover&qid=1653579507&sprefix=,aps,140&sr=8-6

John

 

[swechsler]

In reference to the DBX 120 units, there seem to be a number of variants, mostly the older DBX 100, 110 units, and then the DBX 120, DBX 120X and the DBX 120X-ds. Do any/all of these function as an actual crossover (limiting the low frequencies to the main mix speakers) or do they only boost or otherwise effect the bass output?

I couldn't find the manual for the 110 or the original 120, but the manual for the 120x states that the subwoofer outputs (all of these boxes have them AFAIK, although I've never seen the dbx 100) are strictly low frequencies and it does indeed have a built-in crossover.

 

[Lavane]

I have a couple Crown power amplifiers with DSP built in. They're the CDi-1000's. They're meant for rack mount with screw terminals for speakers and Phoenix connectors for the inputs along with balanced inputs. I modified one with unbalanced RCA jacks where the Phoenix connectors were. My plan is to use at leased one as a sub amp. Yes there is digital prossessing in the DSP circuit, but it's just the low frequencies where your mains roll off. I dought I would really notice much of a difference if any between the possessor and analog at those low frequencies.

 

[rabbitfyter]

I have a couple Crown power amplifiers with DSP built in. They're the CDi-1000's. They're meant for rack mount with screw terminals for speakers and Phoenix connectors for the inputs along with balanced inputs. I modified one with unbalanced RCA jacks where the Phoenix connectors were. My plan is to use at leased one as a sub amp. Yes there is digital prossessing in the DSP circuit, but it's just the low frequencies where your mains roll off. I dought I would really notice much of a difference if any between the possessor and analog at those low frequencies.

The way I use my kitchen audio setup, it's likely that there will be many more additions and subtractions over time. I might include a DSP at some point, and that might be a stand-alone or part of an EQ. This is all just fun for me, and right now I'd like to keep it all analog because it makes me happy to do so. There's no judgement call here on digital signal processing (which I know can be excellent), it's just my whim.

 

[rabbitfyter]

I couldn't find the manual for the 110 or the original 120, but the manual for the 120x states that the subwoofer outputs (all of these boxes have them AFAIK, although I've never seen the dbx 100) are strictly low frequencies and it does indeed have a built-in crossover.

I'm enjoying the way it's setup now that I have the power amps b speakers outputting to the subwoofer amp, but I am going to pick up a dbx unit at some point to use as a crossover. I suppose the bass enhancement processing is interesting, but I'm not sure what even I would use it for. I don't generally have a problem with the way my subwoofer sounds.

 

[rabbitfyter]

I picked up a DBX 120X last week and now have it in my system. It is making the main speakers noticeably crisper (I assume because of the 120Hz internal crossover) and the bass boosting controls are fun to play with. I don't think in most use cases I will ever use the Subharmonic function with my current subwoofer though because it's only an 8" cone in sealed (completely sealed) box. I have plans to build another one, probably a 10" or a 12" ported design, and then will have more of a reason to use it.

Just to be clear, I didn't really expect to notice much of a difference, but I'm truly blown away by how much better my main speakers sound with the DBX handling the crossover duties. I give this thing an A+++