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Full Range 4 Ohm 15" Driver Availability and Options

#25
AlexanderB said:
OK; yakmastermax, while I still say you are doing things the wrong way, I will fill you in with some more data (in the same line given by the other posters, too).
As mentioned, high SPL, deep bass in moderate size enclosures calls for a long stroke (Xmax), rigid (read heavy) cone, low Qts (read powerful magnet and voice coil) to take advantage of the venting, plus a robust surround for linear motion at high excursion.
A speaker uses the current from the amp to move the cone. The magnet field and voice coil gap will act as a "springboard" for the current/magnet force through the voice coil. A good coil to coil gap ratio will transfer a percentage of the current into a motion = high sensitivity. The thing is, that the longer voice coils needed for high Xmax in sub woofers will have more Windings outside the voice coil gap, so less energy is converted to motion, and more to heat. Look up an exploded view or cross section view of the motor assembly to see how different a car subwoofer (sensitivity in the 85 dB range) is from a HF driver (with 105 or so dB).
In the end, when in a correct box, and powered with HIGH power levels, the dedicated subs will still outperform "regular" woofers or full range drivers for maximum output IN THE LOWEST REGISTER, nowhere else.
So that is sensitivity vs extension.

For tone: all the other factors usually found in subwoofers; heavy cone, high inductance and high mass voice coil, robust surround etc will be detrimental to buth clarity and extension of the mids.

So again, I really suggest you rethink what you are doing - especially if you have a (low power) tube amp with the 4 Ohm tap. There is no way you will take benefit of any technical solutions chosen in modern, high power (sub-)woofers. Either you find a pair of modern MI 8 Ohm drivers and get a high sensitivity, medium power, full range cainet. If not, you will have to accept that there very few "raw" 15" 4 Ohm drivers that will do a good job.
One more driver you could consider is the 4 Ohm version of the old Cerwin Vega 15" driver used in PA and bass cabinets through the 80s. Nothing fancy, but fairly robust, cast frame, deep bass, nice sounding for bass (in my opinion), 4 Ohms and easily available from reconing shops or second hand. It is lower sensitivity than the same era "bass" speakers from EV and JBL, but goes deeper.

By the way, I am not sure about how you have determined the bass extension of your candidate drivers? The "unloaded driver" charts provided by some manufacturers are useless below a couple of hundred Hertz. To understand the final result of driver + cabinet, some sort of modelling software (or manual calculations!) is needed.
Click to expand...

Wow that makes great sense. :) The current running through the portion of the voice coil which is external to the gap is essentially wasted current. It is necessary to have this longer voice coil though for big Xmax and extension numbers required for good bass. I clearly see how the mechanical optimization of a driver for big bass means reduced sensitivity/efficiency elsewhere.

Large inductance, necessary to get a large electromotive force for big bass extension naturally results in increased impedance. This impedance is linear with frequency of the applied current so the large inductance reduces sensitivity at high frequency.

What is an MI driver? Yes the bottom line is that when it comes to 4 ohm 15" drivers there really aren't too many options. :unsure:

Would love a model number on the Cerwin Vega. Pickings are slim and I'd like to make the most informed decision possible. Is it full range?

I've simply been looking at the graphs provided by Eminence and Faital. I assumed they could be read straight off but we all know what happens when we assume. Except you guy's aren't asses. I'm just an ass lol :D

I'm on my mac right now but as soon as I get home I'm gonna download WinISD.

If anyone has any more full range 4 Ohm 15" driver suggestions please tell me.
So far the list is a measly 3 long including the unnamed Cerwin Vega from the 80s!

On another note: A whole other can of worms.
What do you guys think about making use of a sealed back midrange driver. The option for a properly designed full range cabinet with separate enclosure for the mid driver isn't available but I've got baffleboard space for a mid driver so a sealed back could work. Eminence makes a sweet looking sealed back mid driver with 100 watts RMS handling but it is only available in 8 Ohms and all of the 2 way crossover circuits (A whole other can of worms) that I've found are meant for matching impedance woofer and midrange. There are some 4 ohm sealed back mid range offerings but most of them have pretty low power handling (50 watts or less RMS) are smaller drivers (5 inches) and are kinda cheap/dinky looking (10 dollar driver :greedy:). I assume I could use these with any 2 way crossover of appropriate crossover frequency and meant for 4 ohm drivers. There are also plenty of prebuilt high and low pass filters meant for 4 ohm loads around the 800-2000Hz range.

Yeah sorry I should clear things up. I'm being such a stickler about the 4 ohm thing because the head is from the 70s and I'm pretty sure it does maybe 100 to 150 watts at 8 ohms. Now maybe that 150 watts at 8 ohms would be enough if it was powering an 8x10 but I'd like to be able to practice and schlep a single 15" cabinet, not a fridge so it seemed reasonable to make use of two 4 ohm 15"s. One for practice and both for gigs.

Thanks a lot for the detailed explanation AlexanderB. I appreciate it very much.

Thank you all for your input and advice. Seriously it is a blessing to have you guys school my 20 year old ass. :roflmao:
 
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#31
B-string said:
You know that answer.;)

To get all those watt thingies out of my amp to fry voice coils, don't care if it get loud as long as the watts numbers are there. :)
Click to expand...

I have been using a stand alone, 4 ohm, 115 cab for over a year now, and don't even feel the need for another cab. It's a Greenboy, Bassic 15, and is plenty loud enough with my GB Shuttle 6.2, and is all I need for my gig situations, with or without PA support.
 
#32
Downunderwonder said:
There is a unused 4 ohm faital in the classifieds. $200 shipped.
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Wow thanks DownunderWonder. That looks really good. I'm still eyeing the Legend though because it is less than half the cost. Also I talked to Eminence (They were extremely helpful) and their tech guy said the Basslite C2515 would work by itself. Any thoughts on that driver for this application?

StraightSix said:
What amp head is it...?
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Acoustic 370. I know most everyone is recommending me to get a matching vintage cab. I understand the merits of doing so but their are also several disadvantages. First and foremost most of those vintage acoustic cabinets are pretty expensive. There is a 408 on reverb for $750 and 406 also for $750. Secondly, the vintage cabinets are hard to find. In many ways they are even more rare then the heads and they're often in worn shape. Lastly I'm not trying to lug a fridge to practice and my car (a small impreza) isn't big enough for a fridge like that. So I do know that the best match for these heads is a vintage matching cab (and maybe one day I can get a 301 cabinet) but I've decided to go another route. I think 2 separate 4 ohm 15"s will give me the most flexibility in the smallest package. Right now I'm trying to put together the first 15" cabinet.

jnewmark said:
I have been using a stand alone, 4 ohm, 115 cab for over a year now, and don't even feel the need for another cab. It's a Greenboy, Bassic 15, and is plenty loud enough with my GB Shuttle 6.2, and is all I need for my gig situations, with or without PA support.
Click to expand...

Yeah I'm pretty confident a single 4 ohm 15" will work pretty well for this head and that's why I'm only focused on making one cabinet at the moment. The Shuttle 6.2 puts out a lot more power at 4 ohms though than my Amp. In the long run I'd like to have 2x115"s.

Also just because I'm curious, your basic 15 is using a 15PR400 driver?


Has anyone heard of the Basslite C2515? How do they perform by themselves without a mid driver or tweeter?

Thanks guys!
 
#33
yakmastermax said:
Wow thanks DownunderWonder. That looks really good. I'm still eyeing the Legend though because it is less than half the cost. Also I talked to Eminence (They were extremely helpful) and their tech guy said the Basslite C2515 would work by itself. Any thoughts on that driver for this application?


Acoustic 370. I know most everyone is recommending me to get a matching vintage cab. I understand the merits of doing so but their are also several disadvantages. First and foremost most of those vintage acoustic cabinets are pretty expensive. There is a 408 on reverb for $750 and 406 also for $750. Secondly, the vintage cabinets are hard to find. In many ways they are even more rare then the heads and they're often in worn shape. Lastly I'm not trying to lug a fridge to practice and my car (a small impreza) isn't big enough for a fridge like that. So I do know that the best match for these heads is a vintage matching cab (and maybe one day I can get a 301 cabinet) but I've decided to go another route. I think 2 separate 4 ohm 15"s will give me the most flexibility in the smallest package. Right now I'm trying to put together the first 15" cabinet.



Yeah I'm pretty confident a single 4 ohm 15" will work pretty well for this head and that's why I'm only focused on making one cabinet at the moment. The Shuttle 6.2 puts out a lot more power at 4 ohms though than my Amp. In the long run I'd like to have 2x115"s.

Also just because I'm curious, your basic 15 is using a 15PR400 driver?


Has anyone heard of the Basslite C2515? How do they perform by themselves without a mid driver or tweeter?

Thanks guys!
Click to expand...

Yes.
 

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