New-B woofer driver selection guidance

[RyanW]

I am looking to build a 3 way stereo system. Tweeter and mid seem easy enough to choose, but the woofer seems like a different story. Is it possible to build a LF system that meets the following?

1. 300Hz to ~20Hz response
2. Sharp tight bass that feels like a kick in the chest
3. Accurate response. (ie. Q=0.7~0.8)

I have plenty of power, a commercial amp rated 400WRMS x2 at 4ohms.

Would it be more logical to reduce the crossover frequency to say 150 or 100Hz? I selected this number as it is approximately the half-power point between the 400W amp I will use on the woofers and the 300W SKA that is to be used on the top end.

[FullThrottleRic]

If you're wanting f3 at 20Hz you're getting into subwoofer territory really, most drivers that reach that low arn't pretty higher up. If you want the crossover close to 300Hz I wouldn't look at anything more than an 8" driver, unless it's one of the higher quality large units from someone like ATC or Volt which is designed to go that high.

Whats your budget, sizes constraints and target output level?

[RyanW]

My budget is ~$200 CDN per woofer. I haven't given much consideration to size, but I have no wife to appease... however I do live in an apartment. In terms of SPL, I don't know the numbers too well but loud is good... earthshattering however is not necessary. As I am planning a stereo setup, I am not constrained to the typical 80Hz limit for the sub... what X-over freq do you recommend? Perhaps I should abandon the stereo idea and conform to a typical single subwoofer application.

I was looking at the Linkwitz transform circuit on ESP. Any opinions on this concept and circuit?

[dickmorgan22]

Most 15" woofers in a 100 litre sealed box will do more or less what you want. I have heard a lambda used this way, it sounded superb. I have a Visaton TIW-400 I am using this way in a current design. Avoid subwoofers.... music woofers will sound better, but DO use a linkwitz transform circuit to drag out that last bit of the bottom octave.

Dick

[RyanW]

Thanks for the input. I am having trouble distinguishing a subwoofer from a musical woofer... From what I can tell, a music woofer has less Xmax. Is this correct? If so, then it will not achieve the desired response at low levels. Perhaps if I am looking for tight (kick in the chest) bass, then maybe I must sacrifice on low frequency response and go for the more musical woofer. Perhaps a 10" musical woofer between ~50 to 200 Hz and a 15" subwoofer for 20 to 50Hz? This means a 4-way system... maybe this is too much complexity?

[FullThrottleRic]

Subwoofers usually have high Xmax, low (~80-85db/w) sensitivity and high power handling.

It makes a lot of sense to me to send all the very low frequencies to a subwoofer in any setup. Giving the sub all the heavy lifting to do means you can make the main speakers much smaller.
Another advantage is room interaction, if you only have one speaker producing frequencies that excite room modes you'll have half as much work to do to fix it. Having a single sub means you can use something such as the Behringer FBQ2496 as room EQ but as you're not feeding your main speakers through it you don't have to worry about it degrading sound quality. (Your ears are much less sensitive at lower bass frequencies).
I'm running 3-way fronts (A variation on Troels' Ekta) + sub crossed 60Hz and the sound is seamless

For a subwoofer have a look at Rythmik Audio's Servo Kits. They use a sensing coil on the drive unit to reduce distortion and have a built in adjustable Linkwitz transform. You have the option of either 28Hz, 20Hz or 14Hz f3 and rolloff Q of 0.9, 0.7 or 0.5.
They arn't the last word in output but the sound quality is excellent

[5th element]

Bass that feels like a kick in the chest is rarely the very low stuff too, unless in HT where the level of bass is extreme, such as from an explosion.

You may find you get that kick in the chest bass from a system with much less extension then you are thinking about.

Running a dance track through a frequency analysis, it shows that the bass drum here, is peaking at around 80hz. Yes there is lots of information below this too (significantly lower ~15dB), that adds the depth to the kick, but the hard hitting impact isn't all that low. Testing another track gives the same result, peak at 85hz for the kick drum and on another track 75hz.

This may not be what you are after, but a good solid response flat to 50hz, thats low distortion, with ample headroom should give you kick to the chest, if the music contains it.

As FullThrottleRic mentioned, low bass is sub territory. You could worry less about outright extension and concentrate more on getting a cohesive sound, between your bass/mid/tweet. With less concern for a low f3, you have a much wider selection of bass drivers to choose from. Then if you find you DO need those really low notes, add a sub.

My dipoles go flat to around 40hz and provide a huge amount of slam.

[dickmorgan22]

If your true goal, like most folks, is to rattle up the windows in the house, use a subwoofer, this is what they do. Subs are characterized by their parameters allowing high output at 20-40 Hz. This means very high xmax and very low Fs. To keep the box sizes sensible (google Hoffman's Iron Law), it results in high cone mass and low sensitivity.

Music. as 5th element suggests, contains very little content below 40 Hz. Most contains none at all. Just for reference, the last time you were in an average night club venue listening to live music, a 15" woofer with a 5 mm xMax and an Fs of 40 Hz was kicking you in the chest with the bass. High xmax and sub 40 Hz output go hand in hand, and are really only necessary for HT applications. Even there, a 15" woofer with a 6 mm xmax has the same output at 20 Hz as a 10" sub does with a 15 mm xmax, give or take. You just need a linkwitz transform to get it.

Look for a woofer with a sensitivity over 90 dB, this is your first clue that its for music, and not a sub. None of them will have a cone mass over 200 grams, or an xmax over 10 mm.

Dick

[RyanW]

If the tight bass is in the 70 to 80Hz region, then perhaps an MTM with 6" woofers would offer the snap that I so desire. I could then add a sub later on to achieve some low end extension. I like the appearance (and price range) of ZAPHs sealed version of "Vifa XG18 / Seas 27TDFC MTM". Has anyone else built this speaker? Would it offer a tight kick and detailed mids?

[dickmorgan22]

What you propose is rather common. Most people use this approach for small size high sensitivity wide range designs. Give an MTM a try. After you have lived with it for a while, audition a 3-way with a 12" woofer or so, and we can get back to where this conversation started. No "little woofer" design will give you the output and dynamics in the "slam zone" from 100-200 Hz like a 10"+ will.

Good luck with it.

Dick