Hi everyone,
I'm new to DIY audio, so forgive me if I'm misguided from the start. On a rash, late-night eBay impluse, I bought four 15" Eminence drivers that had come from Allen Organ speakers from the seventies. The plan was to use them in an open-baffle speaker that I was building with my daughters, but we've decided to simplify that project and won't be using the big woofers.
They have alinco magnets and paper cones and they seem to be in good shape. The stamps on the magnets say "292-0008 67-7548". The 292 code means that they are 15" subs, the 67 is the manufacturer code for Eminence and the 7548 is the date of manufacture. I've contacted both Eminence and Allen Organ and that's as much information as they could give me.
I don't know Fs, Qts, Mms, Xmax, etc. All of the Allen organs have a 32hz stop (maybe even 16) so they must dig down to a low frequency. We tried to power them with a Yung 100W plate amp in the open baffles, but were only able to produce low volumes.
If I wanted to build a pair of subwoofers with these four drivers, how would you guys recommend getting started? All variables are negotiable: I'd consider cabinet sizes big or small, ported or sealed, even odd configurations like ripole. I assume that I'd need bigger subwoofer amps to power them, but that's fine.
I don't have any measuring equipment, but that may prove neccessary. Again, as a beginner, I don't really know.
Thanks in advance! Any help you can provide is appreciated.
David
I'm new to DIY audio, so forgive me if I'm misguided from the start. On a rash, late-night eBay impluse, I bought four 15" Eminence drivers that had come from Allen Organ speakers from the seventies. The plan was to use them in an open-baffle speaker that I was building with my daughters, but we've decided to simplify that project and won't be using the big woofers.
They have alinco magnets and paper cones and they seem to be in good shape. The stamps on the magnets say "292-0008 67-7548". The 292 code means that they are 15" subs, the 67 is the manufacturer code for Eminence and the 7548 is the date of manufacture. I've contacted both Eminence and Allen Organ and that's as much information as they could give me.
I don't know Fs, Qts, Mms, Xmax, etc. All of the Allen organs have a 32hz stop (maybe even 16) so they must dig down to a low frequency. We tried to power them with a Yung 100W plate amp in the open baffles, but were only able to produce low volumes.
If I wanted to build a pair of subwoofers with these four drivers, how would you guys recommend getting started? All variables are negotiable: I'd consider cabinet sizes big or small, ported or sealed, even odd configurations like ripole. I assume that I'd need bigger subwoofer amps to power them, but that's fine.
I don't have any measuring equipment, but that may prove neccessary. Again, as a beginner, I don't really know.
Thanks in advance! Any help you can provide is appreciated.
David
You will need to get yourself a DATS measurement system to measure these drivers, anything less and you're just shooting in the dark.
No subwoofers by any means.
Doubt they would even qualify as woofers by modern standards.
Way back then they would be known as "15" speakers", period, usable with Bass, Organ, and probably Guitar.
Not sure they are Alnico either (although not impossible), would expect early Ceramics, included the funky square magnets CTS and Eminence loved.
Rather than foggy verbal descriptions, please supply a couple pictures: front, side and back.
A ruler by the magnets will help estimate size.
Fs: probably 50/60Hz or thereabouts.
Qts: high,might be as high as 1
Mms: usually "relatively" light cone and voice coil, think "large Guitar speakers somewhat usable for Bass Guitar"
Xmax: short, around 1mm.
Might be wrong but unless proven so, that´s what I expect from your description.
Oh and power handling would be around 50W RMS.
If what I think, very high Q might make them not very good candidates for Reflex cabinets and maybe boomy in closed ones, a popular solution way back then was the aperiodic cabinet: a largish closed box with many small holes in the back or slots covered with fiberglass to damp high Q boomyness.
Surprisingly, often those cabinets "sound good", and I bet Allen Organ used some variation of it.
Search for aperiodic cabinets in this Forum.
Such as:
Aperiodic enclosures
EDIT:
About:
Sorry but they ere NO subwoofers and barely qualify as plain woofers.
An OB is not a bad idea since OBs don´t reach low anyway (unless HUGE) but they may still be boomy.
Maybe enclosing their backs in blankets tacked to the baffle board helps.
Serious.
Doubt they would even qualify as woofers by modern standards.
Way back then they would be known as "15" speakers", period, usable with Bass, Organ, and probably Guitar.
Not sure they are Alnico either (although not impossible), would expect early Ceramics, included the funky square magnets CTS and Eminence loved.
Rather than foggy verbal descriptions, please supply a couple pictures: front, side and back.
A ruler by the magnets will help estimate size.
Fs: probably 50/60Hz or thereabouts.
Qts: high,might be as high as 1
Mms: usually "relatively" light cone and voice coil, think "large Guitar speakers somewhat usable for Bass Guitar"
Xmax: short, around 1mm.
Might be wrong but unless proven so, that´s what I expect from your description.
Oh and power handling would be around 50W RMS.
If what I think, very high Q might make them not very good candidates for Reflex cabinets and maybe boomy in closed ones, a popular solution way back then was the aperiodic cabinet: a largish closed box with many small holes in the back or slots covered with fiberglass to damp high Q boomyness.
Surprisingly, often those cabinets "sound good", and I bet Allen Organ used some variation of it.
Search for aperiodic cabinets in this Forum.
Such as:
Aperiodic enclosures
EDIT:
About:
They will be VERY inefficient below, say, 90 or 100 Hz so waste of power to feed them that, and they won´t handle more than 50W tops, so a 100W plate amp feeding two (what you already have) is the limit.
Sorry but they ere NO subwoofers and barely qualify as plain woofers.
An OB is not a bad idea since OBs don´t reach low anyway (unless HUGE) but they may still be boomy.
Maybe enclosing their backs in blankets tacked to the baffle board helps.
Serious.
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Let me see if these photos load.
Thank you for the replies, guys.
JMFahey - you are almost certainly right about everything. I don't know exactly what to do with these speakers. Maybe sell them...
Thank you for the replies, guys.
JMFahey - you are almost certainly right about everything. I don't know exactly what to do with these speakers. Maybe sell them...
Well, 4x 15" cones can still move a useful amount of air. What're the chances of doing an infinite baffle subwoofer?
If not, I'd probably build a few 1x15" cabinets and sell them to musicians that are chasing a vintage sort of sound.
That said, this can still be a good learning experience for you. I'd recommend grabbing a Behringer UMC202HD, a measurement mic (lots available to suit any budget, although the cheaper ones lose accuracy above 5kHz-ish),, an XLR cable, a couple of 1/4" jack cables and a 100R resistor.
With that lot and a bit of soldering, you'll be able to measure frequency and impedance curves, which IMO is essential for speaker design.
FWIW, to determine Xmax I tend to run tone bursts through the speaker and gradually increase the level until it's just about struggling, and design with that as the limit. You can do that free-air so long as you're careful - start quietly and increase the levels slowly.
Chris
If not, I'd probably build a few 1x15" cabinets and sell them to musicians that are chasing a vintage sort of sound.
That said, this can still be a good learning experience for you. I'd recommend grabbing a Behringer UMC202HD, a measurement mic (lots available to suit any budget, although the cheaper ones lose accuracy above 5kHz-ish),, an XLR cable, a couple of 1/4" jack cables and a 100R resistor.
With that lot and a bit of soldering, you'll be able to measure frequency and impedance curves, which IMO is essential for speaker design.
FWIW, to determine Xmax I tend to run tone bursts through the speaker and gradually increase the level until it's just about struggling, and design with that as the limit. You can do that free-air so long as you're careful - start quietly and increase the levels slowly.
Chris
Thank you, Chris. That's a good idea.
I don't know why I can't load photos of the drivers. I've tried a couple of times and nothing happens. If I can't work the DIY Audio site, it seems unlikely that I've got the chops to actually make speakers!
I don't know why I can't load photos of the drivers. I've tried a couple of times and nothing happens. If I can't work the DIY Audio site, it seems unlikely that I've got the chops to actually make speakers!
This is probably a can of worms, but how would I get started if I wanted to try an infinite baffle? Based on a very quick search, there seem to be tons of different designs.
The reason when you hooked them to your 100 watt plate amp, might it be you have some high impedance drivers? Typically a drivers rating is at eight ohms...if there was four of these beasts within a large organ, they could all have been wired as such, that they all could theoretically be 32 ohms?...or?
Do you have access to a volt/ohmeter?...If they are at 32, you can still work with that.
A large four foot square piece of plywood or MDF, get yourself an inexpensive 6 1/2 inch full-range to extend the top-end...maybe an L-pad to "turn down" the volume of the said new, smaller driver...
Align the three top to bottom...easy! The idea is to create an open baffle, a single freestanding, wide & tall single panel to mount them to...the larger, the better.
Firstly, find out about the impedance .
------------------------Rick..............
Do you have access to a volt/ohmeter?...If they are at 32, you can still work with that.
A large four foot square piece of plywood or MDF, get yourself an inexpensive 6 1/2 inch full-range to extend the top-end...maybe an L-pad to "turn down" the volume of the said new, smaller driver...
Align the three top to bottom...easy! The idea is to create an open baffle, a single freestanding, wide & tall single panel to mount them to...the larger, the better.
Firstly, find out about the impedance .
------------------------Rick..............
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An infinite baffle is a subwoofer with a very large enclosure, typically 10x Vas. We don't know Vas for these drivers, but that's okay.
People typically build IB subs into a wall between two rooms, often cellar and living room.
If you've got somewhere in your house where something like that might work, it might be worth considering. Obviously, it's non-trivial, and as much building work as cabinet work.
Chris
PS - Chances are your photos are too large to upload. You can use something simple like MS Paint to reduce the size - select all, scale to 50% (or smaller), crop the canvas to match, save, and upload.
Ultimately, this is probably what I'll need to do if I want to do anything with these. I'm not sure I'm ready to go down that rabbit hole just yet, though. Maybe after I get the garage cleaned up and finish the open baffle speaker I'll be ready to tackle learning a new system.
There is a place, a coat closet under the stairs, that would work for that. However, if I'm going to demo a wall are these the drivers i want? It's a commitment.
Kalil,
Those drivers brought back memories of a pair from a Jordan bass guitar speaker used in my stereo back in 1975, until I plugged them in to a Phase Linear power amp with DC on it's output and burnt them in a very loud half second..
They did "sound good", though everything JMFahey wrote in post #3 would apply- not enough excursion capability to qualify as sub-woofers today.
Enough harmonics generated from any low tone to give an impression of low bass that is hardly produced...
That said, using your closet for an IB would not require the wall to be destroyed, the speakers could be mounted in a manifold slot, the exit width could be quite small. The slot chamber would provide an acoustical bandpass, and if partially filled with damping material (fiberglass, polyfill, felt etc.) would filter out some of the harmonics. The damping material can be put in a pillowcase or similar suspended near the cones.
The plenum (slot chamber) below has the driver magnets facing in, it could be reduced to 4-6 inches in width with the cones facing inward. Stud spacing could determine width, which is not critical.
If the bass doesn't meet your expectations, you could replace the drivers with better, and sell yours to some Stevie Ray Vaughan wanna-bees, they love Alnico 15s ;^).
Art
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For subwoofer duties, those are not the drivers you want. I'd expect a modern sub driver to eat them alive in terms of output.
That said, making a slot-loaded IB system with those drivers, and then planning to upgrade them, would be a fine plan. Just make sure the drivers are either a sensible cutout diameter, or the baffles are replaceable.
Working what you have is free.
Chris
This is a great suggestion, Art. I may give it a try. Or, I could build them into a guitar cabinet (or cabinets) and give them to my 12-year-old, guitar-playing daughter. She might get the most out of them.