Do you think you need a subwoofer?

@mke246 Great bass always brings a huge smile to my face, it is the part that makes you want to get up and dance.

@rauliruegas It is phase and time. The Australians call it " launch time"  The sub has to be in phase with the main speakers and the signal from the main speakers and subwoofer have to reach your ears at exactly the same time. Changing only the phase angle of the subwoofer is going to change the amplitude response of the system is unpredictable ways. The system may sound better or worse depending on taste and even the music you are playing. It can drive you crazy. One minute you think you have it sounding great, the next minute not so much.

@lewm  Many subs have continuously variable phase angle over 180 degrees, but without the ability to match arrival times the phase angle control is a real double edged sword. Once matched in time and phase everything sounds great. You REALLY need to try subwoofers with your SLs. Get an inexpensive MiniDSP  crossover to start. This will give you a good idea what the advantages are, then you can get a more elaborate unit down the road. Benchmark Media Systems uses a MiniDSP SHD studio and two of their own DACs.

I just finished the first pair of model 4 subwoofer. I'll be putting a picture on my system page. 

@rauliruegas I never said that! From the second I first fired them up I knew Sub model 3 was deficient, but I did learn a lot from building them. Sometimes you have to know what does not work to know what might work. Sub model 4 was inspired by Magico's Q subs, except I took it several steps further. 

The most efficient location for subwoofers is in a corner followed by up against a wall, 6 to 9 dB more efficient. The problem with these locations is you can not integrate the subs properly with strictly analog equipment. It requires digital bass management.  You are putting the subs where they sound best. I am putting the subs where they work best then making them sound even better.

My subs are not transmission lines. They are a balanced force, acoustic suspension (sealed) design with resonance free (and I mean totally resonance free) enclosures. The walls are 1 7/16" thick. The 10 sides are only 4" wide and they are arranged in a cylinder, an inherently very stiff structure. They are much smaller and lighter than the Magicos making them more practical in all situations. They weigh just over 100 LB each. There will be four of them eventually forming an 8 driver linear array. They are 2 dB down at 20 Hz without any processing. @skoss heard them yesterday. You might ask what he experienced. The picture is up on my system page. 

The sound is not where I want it yet. The system is now dead flat from 20 Hz to 12 kHz. I can boost the subs by adjusting their volume relative to the stats, but this makes the bass too warm. The sound is also on the bright side, again because to is corrected to flat. There will be a EQ program in the DEQX and it is supposed to be in the next upgrade. That will allow me to program the amplitude curve to my taste, bass increasing 3 dB/oct below 100 Hz and a shallow drop from 1000 Hz so that 20 kHz is down 6 -12 dB. 

@rauliruegas I think I had the wrong member. It is @sksos ​​​or @sksos1 who heard them yesterday. 

@rauliruegas is right in many ways with a few caveats. 

In a normal point source system two subwoofers is fine and more does not add much. Line source systems require a driver every 4-5 feet along a wall to form a line source subwoofer to match the main speakers.

I would not bother with subwoofer drivers smaller than 12". 10" drivers are fine if you use two of them per enclosure. Most big point source systems require two 15" subwoofers. The smaller the driver the greater the distortion levels at a given volume.

Blending the subwoofers into the main speakers using second through 4th order slopes is appropriate for all subwoofers except a small number of truly excellent units. Subwoofer enclosures are extremely hard to make. Most of them are musical instruments and have a particular sound. If you use a steep slope with these subwoofers the cross is very noticeable. Turn the volume up and place your hand on the sub enclosure. If you feel any vibration you have a musical instrument. Subwoofers that have no sound of their own (do not vibrate at all) can be run higher up using very steep slopes 8-10th order (digital only) as there is little sonic difference between the subs and the main speakers at the crossover point. Here the important factor is keeping the sub out of the midrange where you will hear it. Subs are integrated correctly when you can't tell they are there. Using a low pass filter only on subwoofers is a sad proposition. Easily 1/2 the benefit of using a sub is cleaning up the midrange of the main speakers. You have to use a high pass filter on the main speakers to do this. It is not done because of the added expense of electronics and cables. 

I believe all subwoofer systems should run down to 18 Hz. Music does not go that low but venue clues do. Large venues breath at very low frequencies. With some live recordings you can feel the venue. Subwoofers should be felt more than heard. This is the difference between a live and reproduced performance. Proper subwoofers give you the feeling and excitement of a live performance. 

In my mind there is no difference in the requirements of a theater vs music system. A great music system will sound just fine in theater mode and is quite capable of rattling your teeth.

These are some important concepts to keep in mind when buying subs. Balanced force design. Some of the vibration you feel is the enclosure shaking in opposing response to cone movement. Placing a driver at opposite ends of the enclosure cancels out these forces lowering the musical instrument factor. Smaller enclosures are better because they are easier to control lowering the musical instrument factor, but they will require more power and possibly EQ. A box is the worst shape for a subwoofer. The best shape would be a sphere, but this is impossible to make. The next best shape is a cylinder. Cylinders have inherently stiff walls and are less prone to resonance than flat walls. Cylinders are relatively easy to make and I am surprised that nobody is making cylindrical subwoofers. Open baffle subwoofers are IMHO a silly concept and a florid waste of power. Why some people think they are great is more an indication of how poor many enclosed subwoofers are. There are many excellent subwoofer drivers out there. Dayton makes a Reference sub driver for any situation and I do not see how you can do any better. DIY by all means. Think big pipe with a driver in each end. You can get aluminum pipe in almost any dimension, cap the ends, drivers, binding posts and cleverness. 

Subwoofer drivers take a beating and even the best ones fail on occasion. It is not a bad idea to keep a spare driver handy. The drivers evolve and it is unlikely you will be able to get the same driver after 10 years. Without a spare you will have to replace all of them. 

@mke246 Cool Loudspeaker. I assume you have them up on stands? I saw Ain't Misbehavin 3 times. 

Think of it this way, you are getting two subwoofers to improve the performance of your Genelecs. Your woofers cross to the midrange at 320 hz. Middle C is 256 Hz. Your woofers are handling a very important chunk of the midrange. The Doppler effect inducing frequencies start at about 100 Hz and the effect increases as the frequency goes down, the worse being under 40 Hz. Genelec did a smart thing by rolling off the woofers at 32 Hz to save power and avoid the worst of the problem, but it is still there. Subwoofers used with a two way crossover will lower distortion in your Genelecs. I can't believe the processor that comes with them does not have digital bass management considering they also sell subwoofers. I am all in on  active speakers. The excellent latency and group delay performance of your speakers is due to digital processing. The easiest way to integrate subwoofers into a system is digital bass management and you are already there. When you do play modern recordings the bass will put a big smile on your face. 

I have a bunch of 78s. I can hear through to the instruments and voices and extrapolate to what the real sound must have been like, but the sound is awful. They are fun to play. Many of them have severely tortured spindle holes from changer use, talking about wow. I use an Ortofon specifically for 78's. It has a humongous stylus.  I also have a collection of popular music on 10" discs, the 45's of the day. 

One of the tragedies of my life was my Grandmother's ancient Victrola with the flowered horn. I thought I had dibs on it, but it got sold out from under me. I've never seen another that was in such good shape. 

@mke246 Again it is not just the added bass performance you are looking for. It is improving the performance of your 8351Bs. 85 Hz is OK, but I would go higher at 100 Hz. Just removing turntable and record rumble from the 8351Bs will make a significant improvement.

@rauliruegas I got that crossover frequency directly from Genelec's literature. 

I use Channel D's Pure Vinyl Program for RIAA correction. It also has every EQ curve known to man. My phono stage is digitized, the signal is converted to a USB channel, sent to the computer that applies the chosen EQ curve and sends it back to the Lynx Hilo on a different USB channel. I can also record it to the hard drive in the process and do a lot of fun things like apply a pop and click filter that is very effective. 

I love Fats Waller songs but I prefer to listen to Art Tatum play. 

@rauliruegas I did not say it was new and I recommend ML subs all the time. KEF does it with the Blade.  Magico does it with their Q subs. 

I am not familiar with HSU, but good for them. You are also right that digital bass management with crossovers, room control and EQ have improved the situation greatly.

I have two Model 4 subwoofers up and running. They measure great with a slowly downward sloping curve from 100 Hz down. They are 3 dB down at 20 Hz. This is without correction, with the crossover deactivated. They do not shake or vibrate at all running a 20 Hz test tone and white noise at 90 dB which is as loud as I can go before things start falling off shelves.