Stereo or 2.1 - Which produces better bass punch?

[Bigun]

[...] Just one other observation. Speakers with multiple bass drivers (eg 5" to 6") sound much more punchy than speakers with single bass drivers (regardless of size). That is it is better to have 2 x 6" drivers as opposed to a single 8" driver.

a bit off topic but if I can be allowed - what is the theory behind this ?

I can understand that you can end up with a better dispersion horizontally whilst still having an effective large cone area but what else is there ? Smaller drivers have higher fs so less extension.

I ask because I am considering a new speaker project

Edit: a guess - is there a benefit with smaller woofers that the XO can be pushed higher?

 

[Melon Head]

I wish I could tell you that but I can't, however I have tried this on speaker after speaker and the difference is so bloody obvious you would have to be deaf not to be able to hear it.
My gut feeling on this, is that the cone on a smaller driver (eg 6") will flex less than on a larger driver cone (eg 10") when made out of the same material. Also, the smaller cone will have a smaller moving mass (so there is less inertia) which will mean it can change direction much faster with less overshoot and undershoot.
Less moving mass and flex is a good thing when it comes to woofers.
I can also tell you by adding multiple small bass drivers you increase the efficiency of the loudspeaker so you don't have to pad your tweeter as much (or not at all).

Recently (about 6 months ago) , I went looking for a new stereo system for my friend. We looked at KEF, B&W, and a few others.
Anyway most shops have a switch box so they can switch between speakers on the fly (which this shop had).
Anyway we put on some of my favourite music, and the guy started switching away. One brand of speaker sounded absolutely crap (I am not joking) this speaker retailed at over $1500. There were 4 other speakers which were ok. There were differences between them (One of them was a B&W another was KEF) but it was difficult to have preference of one over the other.
Then there was one (speaker #3) that sounded so bloody awesome in the bass region compared to others I nearly fell over.
At this point in time I had no idea what brands I was listening to and all of them had their protective grills on so I had no idea what drivers or quatity of drivers they were using.

I asked the the guy what speaker #3 was? He pulled off the grill to reveal it had 4 x 5" speakers made by peerless. The speaker company was KRIX. The speaker model was the Neuphonix.
http://www.krix.com.au/Product/Detail.aspx?p=44&id=1

I am not sure I would recommend this speaker though as there was something about the sound coming from the tweeter that I found a little unnerving. I am not saying the tweeter sounded crap it just wasn't to my liking.

Anyway, I hope this story illustrates that, even using 5" inch drivers you can achieve amazing sounding bass.

 

[Bigun]

Thanks, that's helpful.

I have noticed how the big names have been adding cones to their speakers, but thought this was mostly a game of 'mine is bigger than yours'. I will have to dig into this further via Google. They do refer to some extreme tweeters on their web site.

 

[Melon Head]

If you can afford it Zalytron have 4 x 6", and 4 x 5" designs (designed Joe D'Appolito) they would definitely worth considering. They use Focal woofers and the Raven R2 or R3 ribbon tweeter.
http://www.zalytron.com/

If you want to design it yourself I would use the Scanspeak 18W/8545 drivers or you could use the drivers by Usher which are almost identical to the Scanspeak drivers.

 

[AndrewT]

I am on the other side of the fence.
I have a pair of 18" and six 15" to play with.
I also have a variety of 5" to 9" to compare against.
The big driver always has more authority and realism than a small driver.

 

[xitronics]

I am probably going with stereo this time too.

Although I got a few hints from your discussion, but I am still a little hazy on how the speaker dimensions exactly work out for bass frequencies. What I am really interested in is the pattern of the rubber-beats found in many of the electronic/trance genre music.

Edit: Just one other observation. Speakers with multiple bass drivers (eg 5" to 6") sound much more punchy than speakers with single bass drivers (regardless of size). That is it is better to have 2 x 6" drivers as opposed to a single 8" driver.

It could primarily improve the distribution pattern in the horizontal plane I suppose...

Thanks,
Prasanna (Prax)

 

[AndrewT]

It could primarily improve the distribution pattern in the horizontal plane I suppose...

the bass is omnidirectional.
Neither the horizontal nor the vertical distribution pattern needs any improvement.

 

[pacificblue]

I can understand that you can end up with a better dispersion horizontally whilst still having an effective large cone area but what else is there ?

As Andrew already pointed out that is of no concern for the low notes a subwoofer usually reproduces. Beaming usually starts at fmax/PI, with fmax being the frequency at which wave length = membrane diameter. For a 15" driver, which is not often found in homes beaming starts above 300 Hz.

Smaller drivers have higher fs so less extension.

The lower roll-off is not only determined by fs, but also by Qt and the enclosure.

is there a benefit with smaller woofers that the XO can be pushed higher?

It can be a benefit, yes.

My gut feeling on this, is that the cone on a smaller driver (eg 6") will flex less than on a larger driver cone (eg 10") when made out of the same material.

Driver breakup is usually a concern at high frequencies, not at low frequencies.

Also, the smaller cone will have a smaller moving mass (so there is less inertia) which will mean it can change direction much faster with less overshoot and undershoot.
Less moving mass and flex is a good thing when it comes to woofers.

Less moving mass does not mean the membrane will change direction faster. The frequency response diagrams of even 15" woofers show that most of them can easily follow a 1 kHz signal without over- or undershoot. The cross-over will filter out any fast transients, so speed is of little value for a woofer.

Although I got a few hints from your discussion, but I am still a little hazy on how the speaker dimensions exactly work out for bass frequencies.

The room interaction is important. If you are free to place the woofers, wherever you want, build the woofers that you most like and experiment with the position until you find the best one. If your choice of positions is limited, choose the woofer accordingly. E. g. if the woofer will be placed in a corner, choose a closed box or horn, for a placement fairly in the center of the room, open baffle could be a better idea. The room dimensions also play a role as well as the materials. You need a different approach for a wooden floor than for a concrete floor.
You can calculate room modes
in feet and inches and
in meters
and counteract them with the placement and number of subs.
http://www.gedlee.com/downloads/rooms and sources_norm.pdf
http://www.diyaudio.com/forums/showthread.php?s=&threadid=134568

The big driver always has more authority and realism than a small driver.

The explanation could be that bigger woofers usually have longer strokes than smaller ones. Even with the same surface area a bigger woofer will move more air than several smaller ones together. Exceptions confirm the rule.

 

[Melon Head]

Hi Andrew
Are all your drivers from the same manufacturer or are they from differrent manufacturers?

Could you tell me who they are made by?

 

[AndrewT]

Hi T,
two 15" are 385HPD
four 15" are 386 ex Leopard
two 18" are from B950, Celestion manufacture

All are sold as Tannoy.

All have low Xmax for bass drivers.
All have low Qts making deep and extended bass not easy to obtain, but it is possible.

 

[Bigun]

Perhaps there is also the interaction with the amplifier ? with several smaller drivers you have a higher fs and as pointed out this isn't all there is to know about the low frequency roll-off but doesn't it say something about phase and impedance ?

 

[Melon Head]

I suggest to everyone, to go out and listen to as many different speakers as they can. 3 ways with large woofers, 3 ways or 2 ways with multiple small woofers (I have built a 2.5 way). As well as sealed and vented enclosures.
If your into building then you can also try different speaker allignments.
Then try amps with very low damping factor (eg less than 10) and also amps with damping factor of 50 or higher.
It might be that some people may even like distorted boomy bass. "The ear wants to hear what the ear wants to hear." Nelson Pass
I am not going to judge what is right or wrong. But if you guys really want to know what sounds best (for you) you are going to have to listen to quite a few different speaker and amp combinations. Write yourself a list of all the different varriations and tick them off with some of your impressions as you go through the list.

There are so many variables to this it is difficult to be certain one way or another. The best way is to try as many different types of speakers and amps and let your ears be the judge.

Don't buy a sub-woofer unless you want to listen to movies. The money you save by not buying one can be spent on improving your stereo setup.

Edit: Thanks for the list Andrew I will check these out and see how they compare to my favourites.