Mid-bass: Expensive high-power vs inexpensive drivers

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When we go up in price range, drivers usually get more fancy looks, larger coils and magnets for higher power handling and longer Xmax.

Just compare the cheap looking thing on the left to the 20 times more expensive luxury item to the right:

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Are expensive drivers always better? I'm not so sure...

I will set my design goals first :
  • Four 12" drivers
  • Used for mid-bass, 100-500 Hz
  • Line-source
  • Open baffle or closed box
  • Required SPL 100 dB @ 3 meters with less than 1% distortion

(And EQ is available)

Extreme input power or cone excursion is not required to meet these goals. So why pay thousands of US$ for 1000W drivers with long Xmax, when far less expensive drivers can do it?

The thing is that I was rather surprised how well an inexpensive driver like Eminence Delta 12A performed as mid-bass driver compared to drivers costing many times more.
 
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Trying to think of a legitimate use case for the latter high-power drivers, could be those in-between sized gigs where someone wants "blast" levels for a midsized venue but still wants everything to fit into the boot of a car. I once saw a (approx) 100L cab claiming to have 3000W of amplification! I doubt it had a 3-phase plug though.

But as soon as you start scaling up, efficiency goes up, so you could run 10 speakers, producing vastly more output, more cleanly, and at a fraction of the power at the same time.
 
I suppose in fairness, we should probably note that not all expensive [relative term -anything's expensive to me at the moment :bawling: ] drivers necessarily have high power handling. Depends on the type & objects in mind. Most 'traditional' type units e.g. those from Supravox, PHY cost a fair old sum and don't have especially high power handling as that isn't their design goal and they're more or less custom-made on a low-volume basis so by definition aren't going to be cheap.

Be that as it may -assuming the cheaper units achieve the design goals in terms of on & off axis FR, HD, IMD and power-handling / headroom, are free from other potential issues such as varying distortion through thermal heating of the VC, then in theory you don't need more. Although assuming other design features not necessarily always associated with them -give me a well-designed AlNiCo based motor for preference any day. So shoot me: I'm an Altec / W.E. fan, even if they aren't 'perfect'. ;)

Those points are, or can be, big 'if's in a more generalised sense though. For e.g., assuming equal sensitivity but inferior distortion performance at higher levels for the cheaper midbass, and it's used in a relatively compact enclosure for whatever reason (decor, partner, space requirement or simple preference for smaller boxes, even if it's a compromise), then chances are the technically more capable unit will win out when the volume gets cranked & it's driven to higher levels -especially in a medium-larger sized space. I know a couple of people with barn conversions who won't accept particularly large speakers in their, er, 'barn-like' [surprise...] living area. No accounting for taste. ;) Likewise -all things aren't necessarily equal & some of the pricier drivers may have more LF extension capability in a smaller box for similar or lower HD. Broader points not particularly applicable to the stated situation given that 4 x 12in is a fair old amount of cone acreage and even if run dipole, limiting them to the 100Hz - 500Hz range immediately takes a significant amount of stress off them. But that's not what the drivers with the large linear travel, 'advanced' [may or may not be true ;) ] motor design etc. are created for, so in such cases, there may be little value in using them providing you've got something cheaper that ticks all the required boxes. Right plant, right place for gardening -right driver, right use for audio. That's just good engineering.
 
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Where I am willing to pay extra is neodymium magnets and therefore weight saving.
Hi,
like always there is trade-offs which one needs to balance to given context :) few with the magnet as well: simplified, the whole system mass including possible enclosure could be quite low with neodymium magnet which changes resonances, might matter or not. Magnet size also affects thermal effects, how much magnet can soak heat from voice coil and transfer to surrounding air.

In home hifi context with closed box that is not moved around weight savings is not as important as heat stuff, while reflex box for live use could be exactly opposite.

Also, looks could be a thing if the rear side is visible. People seem to associate shiny objects and price tags to good sound.
 
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Yeah for sure :D looks and high price can be important factor and there is high probability audio performance is good as well. But they are not a requirement I'd say :) This is relevant topic in a way, many many projects start from fancy drivers for some reason, while I think it is exactly opposite how a good system should be designed. Forget drivers, crossovers and all details at first, even budget, and figure out what makes your brain happy, then figure out what the pressure variation in the room should be, then how to make it happen. One could assume any size ideal drivers are available, best looks and sound you can imagine.

Designing without limits one would land on some kind of speaker system, which might be anything depending on the context, the room, the brain and stuff like that :) Now you would know size of transducers you'd need, perhaps having calculated how much xmax is needed, perhaps other requirements. Now its easy to choose drivers, you know exactly what to look for, pick few options and listen in the application if there is difference and choose the better one with what ever metric is relevant. If looks and expense is important, pick the fanciest one. If trying to get best possible sound these are irrelevant metrics and could be sacrificed as trade-off in favor for better sound if there is an opportunity.

Sometimes one would choose for credibility, or availability, or top audio performance, what ever. Be sure to know what the options are, what the compromises and trade-offs are, to be able to make a good choice.
 
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Extreme input power or cone excursion is not required to meet these goals. So why pay thousands of US$ for 1000W drivers with long Xmax, when far less expensive drivers can do it?

The thing is that I was rather surprised how well an inexpensive driver like Eminence Delta 12A performed as mid-bass driver compared to drivers costing many times more.
Yeah nice! you are on a path to better sound since attention is on the sound and not in the cosmetics! :) you know your application and context, and what is required to achieve.

Perhaps the expensive driver sounds better but the difference is audible only on another context, like with only 1 driver per side so its not relevant for your application. It is important to give the context, as it could flip preference around. For example if space was premium and only one driver would fit, then in that context some other driver would work better.
 
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Better for business!:) and context.

Its fun to think about it, the technology has been around quite some time so I would assume pretty much any driver manufacturer should be able to make "best" driver for any application/context. But, if you make a special driver with small production volume its gonna be high priced in general, in which case one could add the shiny flashy things which would increase price only marginally but could double the sales as its more appealing, making it financially possible.

Key thing for us DIY folk would be to know the context a driver must fit in, what kind of special driver you need or is bulk stuff fine or even better fit. It might have gold plated connectors or not.

I'm with you on this, the looks is mostly irrelevant for audio performance in particular application )
 
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I think the price difference usually comes down to how high a SPL do you need the driver to maintain full linearity.
And seems most of the time, the pricier ones.....with beefier motors, suspensions, cones, fames etc....have comparatively narrower bandwidth, that also reflects a higher SPL design intention.
So, my take is, the extra $$ are mainly about making cleaner higher SPL...
 
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It seems like a case of chasing your tail; if you want high power handling, you need big, heavy voice coils, which lowers the sensitivity - d'oh !
Plus you need stiff suspension, which curtails the low end. After listening to 3 watt amps, and hearing what they can do has made me rethink how much power a driver needs for MY particular needs, totally different than for PA or car sub use. I'm even considering using a full range driver for augmenting the bass in another speaker.
 
Me, and a friend, tried to line up different sets of woofers for the range around 60 - 500Hz. We already had some midrange/tweeter top box, and multi subwoofers.
2 x 9,5" Satori
2 x 6,5" Purifi
2 x 8" SB NRX
2 x Dayton RS225

A difference... in SPL yes - and extension. But mostly in this range, they work pretty well all of them. Amplitude variance seemed still to be the main factor in perceptive sound quality - in this frequency area.

I think I'm aiming at the RS225 because they would look nice with the black KEF coax that I got for my next DIY. It could might as well have been Seas or NBAC from SB. But the Dayton seems to fit the bill in every aspect. So why pay more?
 
I'm going to put my neck out on the line and state there are some major advantages to cast frame drivers vs stamped steel.

Stamped steel baskets

  • tend to ring at certain frequencies (the cheaper ones) if not reinforced properly (stored energy problems)
  • shroud more of the cone's rear radiated acoustical energy which can reflect easier back into the cone
  • pull a small amount of magnetic flux from the VC gap which can distorrt flux symmetry across the VC gap
  • are more sensitive to rough handling if the magnet is large / heavy
  • will bend rather than break when not bolted down evenly on an uneven bafle surface (a good thing)

Cast aluminum baskets

  • are more acoustically inert thanks to higher inherent stiffness and greater resistance to mechanical distortion
  • can be designed to impart less acoustical shrouding and therefore smaller amounts of reflected energy back into the cone
  • are non magnetic and won't affect magnetic flux symmetry or strength across the gap
  • allow overall tighter manufacturing tolerances ie. tighter VC gaps, higher efficiency and better radiant VC heat transfer
  • are more durable and hold up better to transporting, especially with heavy ferrite magnets
  • tend to be more sensitive to mounting on uneven surfaces (risk of cracking rather than bending)
  • transfer the smallest mechanical drive forces from the VC to the cone, retaining greater low level detail and resolution

There are of course good and bad examples of both types of baskets.

Alot of the stamped basket pro drivers are very nice and approach performance equal to a decent cast frame driver ie. Eminence Beta8, Dayton PA310-8, etc which are both superb drivers. Don't let some of those cheap cast basket Chinese drivers fool you into thinking they're any better. What really counts is the complete package, considering all of the components working together. The cone material, VC and motor design matter much more than just the basket construction itself. Only for portable PA needs would i opt for cast baskets and neo magnets for reliability sake. Domestic hifi use isn't nearly as critical and a decent stamped frame driver would be more than sufficient to get the job done. You can always use some dampening pads on a steel basket if you need to tame basket resonances.
 
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