Single large bass driver versus multiple smaller bass drivers.

admin_exported

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Without getting too deep into the physics of this question, what are the tonal differences of these different approaches to bass reproduction? I know someone like lyndsayt would probably say larger drivers are better but these are almost impossible to go and hear now. Does the multiple driver approaches do a good imitation? Do the quoted bass frequency responses actually matter and how are they affected by room size?
 

MajorFubar

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Single large drivers will often go lower in frequency than mutiple smaller drivers. However big drivers don't guarantee better quality bass, just like small drivers don't necessarily give poor bass. The quality aspect is dependent on the design and build of the enclosure and the drivers. I've heard huge speakers which sound like shoeboxes and I've heard shoebox-size speakers which rattled my balls with the volume turned up loud enough.
 

noogle

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Large drivers are more efficient than multiple small drivers (the voice coil excursion is lower to move a given volume of air). However, they may 'break up' as you drive the frequency up into the midrange meaning that you need a three-way system (bass/mid/treble) instead of a two-way with smaller bass/mid drivers. That means more driver integration problems and a more complicated crossover. Also, large drivers mean a large front baffle and worse imaging. Larger cabinets also tend to be less stiff than smaller cabinets and radiate more spurious sounds, as well as being potentially less aesthetically pleasing.
 

lindsayt

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I agree with almost everything majorfoobar's said.

Larger cone sizes give you greater bass extension. It's all down to the natural resonant frequencies of the cones. As a general rule of thumb:

6" cones will start rolling off at 100hz

12" cones will start rolling off at 40hz

If you want to get down to 20hz, you're looking at 18" or larger cones.

You can extend the measured frequency response of the speakers downwards with the use of bass reflex ports or transmission lines. Techniques which are almost universally used in modern speakers. However the quality of the bass suffers - bass bloom.

Another much rarer technique is to use equalisation to pump more power at lower frequencies into the bass cones to extend their response downwards.

The trouble with quoted bass frequency responses is that too many manufacturers don't quote +/- db figures. I'd rather see a Stereophile type frequency response chart that has different colours plotting the midrange unit, the bass unit and any bass ports, as well as an overall frequency response. If this curve starts sloping down at 100hz you know you'll have a lean sounding speaker, what I call a "transistor radio" frequency response. Also if you get a camel's hump or a sugar loaf mountain somewhere below 100hz this indicates one-note bass.

Do multiple driver approaches do a good imitation? Depends. If you're talking about two 6" cones, no. Not enough surface area and they roll off far too early. Two 8" cones can be OK and not a bad compromise between size and sound quality. Two 12" cones and now you're talking - if they're done right.

I have a pair of speakers with two 12" cones that have better bass than the pair I've got with single 15" cones. The main reason for this is that the 12" cones are in a large sealed box whilst the 15" cones are in a large ported box.

I have never heard any small speakers that have both bass quantity and bass quality.

It's a shame that so few modern speakers use large drivers, as it's always nice to have a choice. There are always enthusiast led events, public shows and private bake-offs where you can hear large speakers as well as a variety of other interesting hi-fi equipment. There's also a lot of large speakers that are readily available from eBay for very affordable prices.
 

CnoEvil

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lindsayt said:
There's also a lot of large speakers that are readily available from eBay for very affordable prices.

.......bachelors only need apply. ;)

Not that I disagree with what you've said. :)
 

lindsayt

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noogle said:
Large drivers are more efficient than multiple small drivers (the voice coil excursion is lower to move a given volume of air). However, they may 'break up' as you drive the frequency up into the midrange meaning that you need a three-way system (bass/mid/treble) instead of a two-way with smaller bass/mid drivers. That means more driver integration problems and a more complicated crossover. Also, large drivers mean a large front baffle and worse imaging. Larger cabinets also tend to be less stiff than smaller cabinets and radiate more spurious sounds, as well as being potentially less aesthetically pleasing.

I agree with some of this, but there's a lot of "it depends" when it comes to speakers.

Two 12" drivers have more cone area than a single 15" driver. And to take an extreme example: one 30" driver has the same area as twenty five 6" drivers.

Yes, large cones do break up earlier than small cones as you rise up in frequency, meaning that most large speakers are 3 ways. There are some that are 4 ways and some that are 2 ways such as vintage Tannoys and Altec Model 19's.

There are large 3 ways speakers that have uncomplicated first order (6db/octave) crossovers.

Driver integration will depend on how many different drivers are used. It also depends on other things such as designer skill and whether the manufacturer makes their own drivers or not.

A large front baffle might produce worse imaging with some speakers, but not in every case. What if they're horns? What if they use a vertical array of drivers? What if you listen to them from a distance of 15' and the speakers are 10' apart - IE you're trying to create the impression of lifesized musicians playing in a band at the other end of your room? What about the vertical aspects of imaging? Kick drums located near the floor, singer standing up, cymbals high up?

Large cabinets less stiff than small ones? Depends upon wall thickness and bracing. How stiff do they have to be to be stiff enough?

Spurious sounds? What spurious sounds are these? Surely these spurious sounds would result in distortion, or a lack of clarity, or detail, or a worse signal to noise ratio, or a worse bass, or midrange or treble or something? I can't hear any spurious sounds from my large speakers when I compare them to my small speakers. Maybe someone can suggest some small speakers that I can use as a reference to hear these spurious sounds from my large speakers? Spurious sounds. Spurious marketing ploy more like.
 

manicm

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So a large driver by necessity can't be housed in a cabinet as rigid as smaller driver cabinets Nooble? That's pretty heavy generalising there.

I also don't necessarily agree that larger drivers afford less imaging - this is an absolute myth, if common sense is applied on purchasing a right-sized speaker for a room.

From these forums I gather that not many UK residents living in apartments have space to place speakers 2m apart or more. If you have this kind of space you can place larger speakers without affecting imaging or depth.
 

noogle

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manicm said:
So a large driver by necessity can't be housed in a cabinet as rigid as smaller driver cabinets Nooble? That's pretty heavy generalising there.

I think I said that "larger cabinets tend to be less stiff than smaller cabinets". I stand by this.
 

noogle

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OK - let's take 10 floorstanders and 10 stand-mounters. For longitudinal stiffness lay them horizontally on their sides supported at either end. Place a 50kg weight on top in the middle and measure the deflection in mm. For rotational stiffness restrain one end and bolt a 1m steel bar to the other. Hang a (say) 10kg weight from the bar end and measure how much the bar rotates in degrees. I'm surprised WHFSV don't do this.
 
A

Anonymous

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manicm said:
noogle said:
I think I said that "larger cabinets tend to be less stiff than smaller cabinets". I stand by this.

And you substantiate this...how???

This is simple Newtonian physics, a bigger/longer item made of the same stuff bends further with the same force applied. Big speakers are rarely made stiffer and better braced for their size than small ones. Next time you see a place with small and big speakers rap your knuckes on the top of them. The higher the note the more rigid (that bit of) the box is.

This is one (one) reason why open baffle speakers are making a comeback - no cabinet colouration, which frankly for many modern speakers is appallingly audible.
 

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