Subwoofer setup in an active 2 channel system

J

Jon622

Audiophyte
I would like to build my own speakers sometime this year. my plan is to build a pair of 2 way speakers and put an active crossover before the amplifiers. Obviously I’ll have to bi-amp with an active crossover. I’d also like to add 2 subwoofers to the system. What I’m unsure of is how to connect my subs. Should I get a 3 way crossover and send the low frequencies to the sub, or is there a better way? I already have one sub and I will probably buy a matching one, and they do not have high level inputs, so that won’t be an option. One more question: can I utilize the balanced outputs and the unbalanced outputs on the preamp at the same time? For instance, can I connect the preamp to the crossover with the balanced outputs and connect the preamp to the subs using the unbalanced outputs, or can you just use one or the other?
the system will be set up like this: cd transport>dac/preamp>active crossover>poweramps>speakers
Thank you so much to anyone who is able to answer this question.
-Jon
 
TLS Guy

TLS Guy

Audioholic Slumlord
I would like to build my own speakers sometime this year. my plan is to build a pair of 2 way speakers and put an active crossover before the amplifiers. Obviously I’ll have to bi-amp with an active crossover. I’d also like to add 2 subwoofers to the system. What I’m unsure of is how to connect my subs. Should I get a 3 way crossover and send the low frequencies to the sub, or is there a better way? I already have one sub and I will probably buy a matching one, and they do not have high level inputs, so that won’t be an option. One more question: can I utilize the balanced outputs and the unbalanced outputs on the preamp at the same time? For instance, can I connect the preamp to the crossover with the balanced outputs and connect the preamp to the subs using the unbalanced outputs, or can you just use one or the other?
the system will be set up like this: cd transport>dac/preamp>active crossover>poweramps>speakers
Thank you so much to anyone who is able to answer this question.
-Jon
Not sure what you are going to gain here.

That is a lot of cash and money just to power a tweeter. Unless you are going to get fancy and use DSP for Eq and time alignment, I doubt you will have an advantage over a passive design.

I assume you are going to use an AV pre/pro to drive this. In which case you use the sub outs to power subs, then you also capture the LFE signal. If you use a three way active crossover, then you will need to design and build a mixing circuit to blend in the LFE. So a lot depends on the frequency you cross to the sub. If it is 100 Hz and below, then I would not use a three way crossover.

You also have to decide how you will power and protect your tweeter, if you use a two way active crossover. Tweeters take little power for one thing. If you connect a power amp directly to a tweeter, you will soon blow it. You have to protect from pops and thumps. The first turn on thump will be the end of the tweeter.

The real advantages of active bi-amping come from crossover points lower in frequency.

So If you are going to go to this expense and trouble, I would actually design a three way. Then you can select a midrange driver that can handle the whole of the speech discrimination band. So crossover points at 400 Hz, and 3.5 to 4k range. Use a passive crossover for the upper crossover and active for the lower, and then you get to pay dirt. That is what I would do.

The other problem you need to solve is how to handle the baffle step compensation from an off the shelf crossover if that is what you use rather than a custom one. This is to compensate for the transition from half space, to full space radiator. This compensation is a function of the width of the front baffle, and there needs to be a boost of 6db below the transition point. If this is not applied the speaker will sound thin. This is actually more easily done with an active design over a passive one. If you know what you are doing you can make this variable to fine tune a speaker to its position in the room to adjust for boundary effects etc.

If you have never designed a speaker before, then starting with a good two way passive design is a good way to start.

If you have never designed a speaker before, then I don't think you are ready for project where you need a bit of experience under your belt.

To your last question you can use balanced and unbalanced outputs at the same time on a pre/pro. However the only time I can see this being advantageous is if you are designing a truly potent full range speaker (20Hz to 20KHZ) and need to blend in the LFE signal. That is what I do, which is also integrated with variable BSC.
 
J

Jon622

Audiophyte
Hey, thank you so much for your quick and thorough reply! I really appreciate the insight of someone who cleary knows more about this than I do. To be honest, I don’t mind dropping the money, and I just want to build a pair for fun, and of course for the experience. I actually want to build several pairs in my lifetime. I will definitely consider going with a three way design as well. So basically if I do what I had originally mentioned I’d blow my tweeter? Can this be negated by using multiple tweeters per channel to divide the power, or possibly by using a low watt amp, like a vintage tube amp for the tweeter, or would you always recommend a passive crossover for the highs? One of the reasons I wanted to start with a 2 way design was because I already own a 3 way that I purchased used (Klipsch heresy) and I wondered what a large driver would sound like playing up into the midrange. In your experience, what is the biggest advantage to using an active crossover in the lower frequencies? Since I want to add subs, I just didn’t want my midbass drivers trying to play too low. Am I on the right track there? Thanks again.
 
TLS Guy

TLS Guy

Audioholic Slumlord
Hey, thank you so much for your quick and thorough reply! I really appreciate the insight of someone who cleary knows more about this than I do. To be honest, I don’t mind dropping the money, and I just want to build a pair for fun, and of course for the experience. I actually want to build several pairs in my lifetime. I will definitely consider going with a three way design as well. So basically if I do what I had originally mentioned I’d blow my tweeter? Can this be negated by using multiple tweeters per channel to divide the power, or possibly by using a low watt amp, like a vintage tube amp for the tweeter, or would you always recommend a passive crossover for the highs? One of the reasons I wanted to start with a 2 way design was because I already own a 3 way that I purchased used (Klipsch heresy) and I wondered what a large driver would sound like playing up into the midrange. In your experience, what is the biggest advantage to using an active crossover in the lower frequencies? Since I want to add subs, I just didn’t want my midbass drivers trying to play too low. Am I on the right track there? Thanks again.
The point is that you need some type of crossover to the tweeter in any case. One tweeter is best. But you have to stop low frequencies getting from the power amp to tweeter. That means a cap at least between amp and tweeter. It is a very bad plan to couple a tweeter to a direct coupled amp. Pops and thumps happen.

Lets be clear bass is 20 Hz to 500 Hz. This nonsense about midbass is just that. If you cross below 350 Hz for sure, then in my view an active design is mandatory.
The lower the crossover point in a passive design the more you are likely to have difficult to drive loads. The components get enormous and power losses get significant.

The next issue is localization. So you need your main speakers to have good performance to 40 Hz ideally, as you don't want to cross above 80 Hz ideally. Then you should aim for a speaker that plays an octave below crossover, since crossovers are not brick wall.

Now the ear is most sensitive in the speech discrimination band, which is essentially 400 Hz to 4 KHz. If you can build a speaker with a single driver or MTM arrangement covering that band, that has good performance you are miles ahead. That avoids time/phase issues in that band and aids speech intelligibility.

If you do cross in the speech discrimination band, then your crossover requires obsessional thought and design, or it will stick out like a sore thumb.

And don't forget, whether passive or active your crossover must be designed to the drivers you select, so that the crossover meshes with the acoustic responses of the drivers, especially an octave either side of crossover at least. Often times you need notch filters included in the design, to deal with out of band response peaks from cone break up issues.

Building a speakers is great fun. However, a good design takes a long time to refine. The more ambitious and complex the more thought you have to give to it.
You end up modelling a lot of possibilities. That is especially true when you are trying to select drivers that will work well together. Selecting the wrong drivers shoots you in the foot, fatally so to speak at the outset.
 

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