Adding subwoofer to Full-Ragne Speakers question

Especially for music...
The sub will surely add deeper base in the bottom end side..., I guess that's the purppose of adding a sub to begin with...

However, does it help in the midrage area?
Taking some load off of those woofers on the speakers so that they can concentrate on the midrage? or it doesn't matter as far as midrage's concerned.

I think I never got clear answer to this question, yet...
Let's not anthropomorphize speaker drivers. They do not have powers of concentration. They merely move in response to electrical signals delivered to them. Now I suppose it's conceivable that if a crossover were diverting LF signals away from your mains, the drivers might be marginally more accurate, at least at times. But I wouldn't expect this to be particularly significant, if it's even real. And any such effect will be overwhelmed by the effect on the bass. When you try out a subwoofer in your system, I guarantee that your decision about whether you like it or not will turn on bass performance, period.
The sub will only help the front speakers at and below the crossover point you set. Most will set it at 60-80hz. You need to know the low cut-off HZ level for the speakers and then see what either the pre-amp/receiver and sub x-over will allow you to set for the cross over. If you have speakers the drop down to e.g. 35Hz and the sub will let you set your X-over point as low as 40hz the try it there for starters. As far as the Mid Range it remainst the same. The speakers never know the sub is playing so they offer no compensation for range. If your reciever/pre-pro let you set the cross over then the front speakers will never see the frequencys below the cross over point as that information is re-routed to the subwoofer.
Well, thanks guy...

Theo says it's not goinig to help at all.

Bomarc basically says it might be marginally helpful but probably not that significant

I don't know how speakers work internally, but basically what I thought was that producing bass is a lot of work for the speakers, and if the subwoofer take some of the hard work away, then there would be more capacity left with the mains to work on other area(namly midrange), thus produce more accurate and rich midrange sound.

I guesss it does not quiet work that way??
No, it does not work really work that way.
I'm no EE, but I'm gotten different answers to this. There are a number of different factors at work.
1. The bass waveform places a significant demand on your amplifier. If you use a powered sub and cut off the low bass with some kind of crossover, then the main amp does not have the same demands placed on it and has more current reserve available.
2. Reproducing low bass can also place a significant demand on the main woofer. If it does not have to go as low, there is a good likelihood that there will be less distortion in the bandwidth it is producing.
3. Most (but not all) full range speakers cannot produce the bass in the lowest octave at the same volume. In other words, they roll-off the lowest frequency. Or another way to look at is "how low can they go". A good subwoofer can usually provide useful, undistorted output down to 20 hz; few "full range" speakers go that low.

I'm sure there are others with more technical know-how, but that's my understanding.
The folks at Audio Concepts agree with Swampwalker's #1. Since they sell powered sub-woofers, they designed high pass filters to help the amp out. These would be if your preamp or processor has no built-in crossover controls. These filters come in both SE and balanced. Since they have a 30 day return policy, the best way is to hear for yourself if they work or not.
i added a pair of 2wq subs to my 3a sigs and it really cleaned up the mid/upper bass. mids and highs also improved. the setup utilizes a 6db/octave highpass filter which is sampled then boosted by the sub. whether the improvement is due to less strain on the 3a's woofer or increased amplifier headroom, i'm not sure. probably both. but the systems performance did improve noticably.

aloha keith
Swampwalker gave a good answer. In addition to the amp issues he explained, I believe his #2 comments have to do with the main bass driver not trying to move as much air if the LF is cut off. Therefore, the excursion of the bass driver will be less and the inherent distortion will be less when that driver is trying to also reproduce lower mids and upper low frequencies (above your cut off). However, like most things audiophile, there are trade-offs, which in this case include very careful matching of the sub with your main speakers, meaning the actual type of sub speaker(e.g., size/ported/sealed/servo-type/power, etc.), as well as the phase, crossover level, and boost/volume. You have to be careful because many/most subs are actually designed for the loud impact of HT, and not particularly for music. Your success will also depend on where your LF driver is crossed over. If it acts mainly as a subwoofer already, e.g. crossed over under about 150 Hz, or has its own internal amp, then your benefit may only be the adding of the very low bass below what your main speakers can do. However, if your LF driver is crossed over high, up into the midbass range, then you start to get the other benefits discussed by swampwalker. Many folks with high quality full range or almost full range speakers (that go down into the mid 30's to 20's) believe their speakers sound better without the issues associated with trying to integrate a sub. Then there is the type of music you listen to, your room size and characteristics, WAF, and on, and on, and on....Good luck.
I agree with Mitch. At present I am using a Loft active crossover in my signal path. I did this more from for as amplification relief for my tube amps as Swampwalker outlined in his first comments. The other reason I experimented with this was the fact that what money I had invested in it initially, I knew I could recover if the experiment did not yield the results I wanted. I actually would have made a profit since some one offered me his present crossover + the $400 I paid for mine and a second person offered me $700. As for the Adcom I got on E-Bay to run the lows I would more or less broke even if I decided to sell. External active crossover use is pretty rare and many will argue that an added component with an added interconnect in the signal path may produce more ailments that outweigh the symptoms that are cured. So if you are willing to invest the time in trying which may be considerable since you can experiment with different crossover points and if the crossover has a gain control (My Loft does)it will only add to the possibilities. Remember if you decide to try this and once you have it tuned to your liking, pull it out and see if you are still happy without it. When I pulled mine out my music lost some of the dynamics and lower midrange clarity. I did get tiny, tiny bit of smoothness on the upper highs on some recordings so I basically choose my poison.

Good Luck James
I don't have any engineering or electrical background, but here's my experience:

I had Maggie 3.6's and a REL sub. I sold the Maggies and bought Aerial 9's. They are rated to 30hz, down 6 db at 27hz. They aren't at all bass shy.

I still had the REL....just hadn't gotten around to selling it. So, for kicks, I hooked it up with the Aerials. I ran the REL straight off the amp, driving the Aerials full range.

AND>>>>WOW. It made the whole system sound better, top to bottom. I found that I was setting the volume lower and the room was still pressurized. It seemed to me that the treble was clearer and the midrange more spacious.

I don't have a clue why this was the case, but I hooked it up and unhooked it, and I've done this with friends present, and they all agree. So don't look for my REL for sale any time soon.

Of course, YMMV.

Me no electrical engineer either, but think of it this way -- folks bi-amp speakers, right? And the point is both to increase the power to each individual set of drivers and to put correspondingly less demand on each amplifier in order (which is why folks presumably do it) to improve the sound. Depending on how, where in the signal path (and if) you've got a crossover dividing things up, the addition of a powered sub could work in exactly the same manner. As long as there is some sort of crossover in the chain before the signal gets to the speakers, the speakers should never see the low frequency demand (nor place the power requirement demand on the amp in order to reproduce it) as those low frequencies would be sent to the sub (with its own, private amplifier). The functional equivalent of bi-amping by proxy. Thing is, while they could be, I bet most subs simply aren't set up this way (which is only right an proper, when you're talking about a full range speaker in the first place). Rather, they are simply put on top of the existing setup: the amp and the speakers continue doing exactly what they were doing before the sub got there and the sub just provides "extra," instead of redistributing the signal, or power demands or responsibility for makeing certain sounds. Sure, this might make "everything" sound better for a whole number of reasons, real or imagined, I just have a lot more trouble coming up with a rational, electrical explanation for the improvement in the second scenario.
Take the speaker grill off, and play a record with lots of bass, best of all an LP with a bit of a warp, and watch the antics of the woofer cone. I think you will agree that it is a wonder that the poor woofer reproduces midrange at all.

Also, some folk think that the slightest movement of the speaker "blurs" the midrange, and they go to great expense to immobilize their speakers. Well, with the midrange emminating from a cone that moves back and forth 3/4 inch or more, what does that do to the midrange?

I think that the main reason to have a subwoofer is to get that LF which requires long cone excursions, out of the woofer. Oh, and it helps the HF power amp too.
I have two ways (w/12"PHL 4530 midbass drivers) plus stereo subs, and use a DEQX with both 2 and 3 way digital crossover ability. My initial plan was to implement a 3 way crossover to lessen the bottom end burden on my PHL midbasses (decrease intermodulation distortion). Philippe Lesage, head speaker designer of PHL, graciously answered an email inquiry on this topic with the following. He said, in essence, that the deleterious effects of a high pass filter on the midbasses outweighed the benefit of chopping off their low end duty, and that letting the midbasses naturally roll off while "dialing in" the subs to supplement the bottom octave was far preferable.

Another factor to consider is the low end capability of your 2 ways. My 2 ways are -3dB at 44 Hz and there is precious little musical content below this frequency in the music I listen to (example: the lowest electric bass note is still above 40 Hz). In truth, my stereo subs are a costly luxury, basically musical slackers for the vast majority of my listening with much potential to overly excite room modes and detract from enjoyment. "Dialing-in" is far from a simple task, even with stereo subs.

My 2 cents, to be taken ONLY for what it's worth, is to find two way loudspeakers that are capable of playing down to 40-50 Hz at adequate SPLs for your taste. It's all about choosing the best compromise among the imperfect solutions. A single full range point source reproducer exists only in theory. For me, no single driver stereo loudspeaker system will truly "rock" to the SPLs I like. I've never heard the big 2 way line array loudspeakers so can't comment. For me, 2 ways with large cone midbass drivers, actively biamped, provide the best combination of imaging, soundstaging, dynamics and SPL ability.

Just some grist for the mill - nothing more, nothing less.

I don't know how many times I've heard other REL owners say the same thing as you, and that's why I intend to buy one myself to improve the already great sound I'm getting from my ProAc 2.5s.

I guess when a sub bass system is well designed and set up correctly it can yield improvements in the main speakers even if the sub is completely separate from it. The point you make about the REL pressurizing the room and being able to back off the volume to the mains may be the key.