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rcgtrix

rcgtrix

Apr 15, 2008
80
1
Texas
#1
I'm wondering how well the Eminence Commonwealth 12" guitar speaker will work as a bass guitar speaker. The reason I mention the Eminence is its resemblance to the old JBL speakers with aluminum dust caps - just a silly aesthetical preference. Thought about buying some old JBLs (D-120 a bass speaker?) for reconing but figured a current model might benefit from newer technology and materials.
My goal is to build a 3x12 cabinet that will emulate (as best as a cab loaded with 12s is able) that of an Ampeg 8x10 - tightly focused with a hard punch.
What I have in mind is to mount each speaker in a separate, sealed chamber - each chamber being of the same size housed in one cabinet.
I'm not concerned about the bulk or weight - even the cost (within reason).
An extremely broad frequency range isn't necessary as I have a 2x15 cab and some 10" Hartkes. It would be nice to be able to use the 3x12 as a stand-alone, though. Too, it dosen't matter how much or how little power is required.
I'm sure Thiele-Small is obvious but still seems to escape me.
I'd be happy to hear any criticism, opinion, input or direction any have to offer.
Thanks so much and sorry for the rambling rant.
 
#2
It might work, but it might not, and you would be somewhat limited in wattage you could use. I think it's an interesting idea, and you could make a standalone cab out of it, but I would probably look for heavier-duty speakers voiced for bass.
 
#3
Hey, Jimmy,
This is what I'm saying about not understanding the mechanics of the parameters. The speaker has a 225w rating, yet you understand there would be a limitation in using it for a bass. Which parameter is weak for my application? It just flies right over my head. Please excuse my ignorance and I appreciate the reply.
Rick
 
#4
Here is the (huge) weak point:

Maximum Linear Excursion (Xmax) 0.7mm

Halve Xmax and bass power handling reduces to a quarter. The 10" woofers in an Ampeg 8x10" have about 3mm Xmax, and more modern bass guitar woofers have an Xmax of ~5mm. That means each 12" speaker can handly less than 5W in the lows before distorting, vs an Eminence DeltaLite II 2512 handling more like 50W in the lows in a sealed cab.

Alex
 
#5
What alexclaber says is right. Guitar speakers can't handle the long excursion needed for bass, despite the rated power handling. You'll wind up with a cabinet that could only be used for quiet at home practice, and there are a lot of small cabinets made for the purpose that you could buy for less than the cost of making a cabinet and buying the speakers you mention.

The D120 was not a good bass speaker. Even the old D140 which was designed as an electric bass speaker couldn't handle the low end without failure like the modern bass speakers can. I managed to blow a few of them back when they were the latest thing and with low power by today's standards.

If you must build yourself a sealed enclosure, find an Eminence bass speaker that is designed for mounting in a small sealed enclosure.
 
#6
If the eminence driver is voiced like the JBL 120 it would be a diaster as a bass guitar speaker. The JBL 120 was a fine guitar speaker but has no low end at all. Very little output below 100 HZ. Alex is right about the excursion also. For a bass amp go with a bass speaker.
 
#8
I did notice the big difference in the Xmax figures in comparing the Commonwealth to speakers made specifically for bass. I read when speakers are installed in an enclosure, the listed parameters could change - also to consider how one will influence the other.
Let me try a different approach here.
Can I retrofit a new bass speaker with an aluminum dust cap without severly altering the characteristic or performance of the speaker?
Or, are there any good bass speakers being made that have the aluminum cap?
Thanks again.
Rick
 
#10
Lloyd,
I just like the look of the old JBL speakers. I don't really want to extend the range. In fact, I would prefer them to perform more like that of a 10". I'm going to build the cabinet myself and would like for it to have a personal flavor.
Rick
 
#11
Rick,

I don't know of any modern speakers that use an aluminum cap, but you could find a reconing facility for JBL and see if you can purchase the dust caps and the setting glue. Just realize that some of the modern dust caps (paper) have a more spherical appearance than the JBL and the JBL aluminum cap may not seat without doing some surgery on the original dust cap.

Try http://www.simplyspeakers.com or Link Removed or [Invalid or Expired Link Removed]

http://www.talkbass.com/forum/archive/index.php/t-76947.html may help also.

The other thing is that most of these repair parts come in recone kits and I think you might have to buy the entire kit and they can run up to $100 or you may luck out and find someone who'll sell you just the aluminum dust caps.

Good luck,

Lloyd
 
#12
Thanks Lloyd,
When you said there are better solutions for extending the response, I thought you were talking lower frequency - my mistake. I appreciate your suggestions and links. I'll probably check with a speaker repair shop to see if the caps are interchangeable.
Rick



PS Or maybe you were talking about the overall response. Anyway, thanks again.
 
#13
rcgtrix said:
Thanks Lloyd,
When you said there are better solutions for extending the response, I thought you were talking lower frequency - my mistake. I appreciate your suggestions and links. I'll probably check with a speaker repair shop to see if the caps are interchangeable.
Rick

http://s84.photobucket.com/albums/k9/rcgtrix/

PS Or maybe you were talking about the overall response. Anyway, thanks again.
Click to expand...

Actually I was referring to the high end frequency response. I should have been more explicit, sorry.

One remark about the older JBL drivers, in particular the musical instrument drivers. They have a very low Qts, and over the years, I've done some experimenting with these in various sized boxes, all vented. I've found that these drivers are much more forgiving about being in a too-small box than drivers with a Qts in the mid 0.3's and higher. Although I really like the sound of the newer Eminence Neo drivers, I still have an affection for those old Alnico drivers. I'm also very partial to the Electro-Voice EVM-15B drivers (ceramic magnets). I've had/kept and EVM-15B, a D130 and a D140 that I bought in the early '80s and they still work fine and sound great. I don't gig with these anymore as I baby them at home. But I do use an E145 loaded cab that sounds very smooth for an older JBL. I know the D130 was intended for guitar, but its amazing how nice it sounds with bass at low power. It came out of a Fender 2-15 late '70s cab that a guy on the road, in '81, cut in half and needed to sell the other D130.

:)

Lloyd Howard
 
#14
lhoward said:
I've found that these drivers are much more forgiving about being in a too-small box than drivers with a Qts in the mid 0.3's and higher.
Click to expand...
One property of low Qts drivers is that they work well in small boxes, or more properly, they don't need large boxes to deliver what they're capable of giving. The downside to low Qts drivers is that they also choke off bass response, often by an octave or more compared to drivers with a Qts in the .35-.4 range.
 
#15
OK
After unsuccessfully finding a 12" bass speaker with an aluminum dust cap, my focus now is to determine which 12" will be the ultimate performer for my application.
As I stated in my original post, I'm going to build a 3x12 cabinet to emulate an Ampeg 8x10 - to the best of its ability.
To find a 12" speaker that will perform as a 10, which parameters are of importance?
I assume that mounting one speaker per one sealed chamber will yield the best result. Is this true?
The luxury of this build is that the cabinet can be built to accommodate an outstanding speaker.
All comments are welcome.
 
#16
DSCN2927.jpg


DSCN2926.jpg
 
#20
spode master said:
And what did you end up using?

I was a little upset to find those Neutrik Locking connectors are not sealed. And It doesn't apear they make a sealed version.
Click to expand...

My plan was to enclose the rear of the dish within the cabinet. Then it dawned on me that I have a bag full of combination cables and adapters and I don't need to do all of that unnecessary work. So, the dish will have two airtight Neutrik Speakons.
The speakers are Weber ceramic Californias with bass cones. They are listed as 80 watts each but Ted Weber assures that the rating is on the conservative side.
You do very nice work, by the way.
Rick
 

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