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Help with replacement speakers for unknown cab.

hedshovel

hedshovel

May 16, 2009
23
5
SoCal Desert
#1
Hi Guys, I need some help with replacing speakers in a couple of unknown cabs. I picked up two of these 15" cabs from a friend and they are in excellent cosmetic condition. They have an old school 70's vibe in appearance, but they sound like crap. I do not know the maker of the cabs. I opened them up to check the speakers and there are no manufacturing markings or #’s on the speakers. Upon inspection of the speakers I noticed that the paper cones show signs of distress & creases and when I push on the speakers I hear a scratchy crunchy sound that I think is coming from the voice coil(?). I would love to make these cabs useable because they look so good but after researching here on talk bass I realize that there is a lot that goes into making a cab sound good. I would hate to drop money on a pair of speakers only to have disappointing results. So I was hoping that some of the experts here on TB could offer some advice.
Here some spec’s on the cab: INSIDE cab dimensions are 17” Wide x 17” Deep x 19” Tall. - So approx. 3.17 sqft. The boxes have just one round port each on the back side. Port size is 3” across and 5.5” deep. The port size seems small to me and I can cut a larger port if needed but I would rather not. I can trim some off the port length as well. Now a little about the sound I would like to achieve –deep, round, even old school Reggae and Motown sound w/ clear definition. I play a 5 string through a Hartke 3500A - 270 watts @ 8 ohms / 350 watts @ 4 Ohms.
So if it is at all possible, I would like to drop in some replacement speakers and put these cabs to work. Please chime in w/ opinions or suggestions - Thanks
 
#4
Pictures… of course, I’ll try to upload some when I get home tonight.
Now as far as WinIsd goes, I expected that suggestion and I have checked out the online version and it is completely confusing to me. I’m not trying to be lazy about this, I’ll invest some of my time into trying to figure that out, but I was really hoping some of the experts here could offer some suggestions with the info I provided. Once again – Thanks!
 
#5
Ok -here is a picture of the cab in question...
 

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#6
So I have downloaded WinIsd and started working with it, after spending a few hours with it things started to make sense - I still have a long way to go but here is what I come up with... Plugging in the sq-ft of the cab and using the Eminence Kappa Pro 15lf as a point of reference - I discovered the 3" port is too small - I assumed that from the get go. So if I add two 4" ports at 4.5" in length (total of 9")the vent mach is 0.06, well within the green but the cab tuning will be in the range of 155hz. What would that sound like? I'm not sure, but shouldn't the cab tuning be in the range of 35 - 45hz to sound good. If I want to tune it to that range of 35 - 45hz, WinIsd says I need a port length of 9.34 meters. I just don't see how that is possible. Am I missing something here? Please, can anyone offer me advise, am I just spinning my wheels here w/ this cab?
 
#7
hedshovel said:
So I have downloaded WinIsd and started working with it, after spending a few hours with it things started to make sense - I still have a long way to go but here is what I come up with... Plugging in the sq-ft of the cab and using the Eminence Kappa Pro 15lf as a point of reference - I discovered the 3" port is too small - I assumed that from the get go. So if I add two 4" ports at 4.5" in length (total of 9")the vent mach is 0.06, well within the green but the cab tuning will be in the range of 155hz. What would that sound like? I'm not sure, but shouldn't the cab tuning be in the range of 35 - 45hz to sound good. If I want to tune it to that range of 35 - 45hz, WinIsd says I need a port length of 9.34 meters. I just don't see how that is possible. Am I missing something here? Please, can anyone offer me advise, am I just spinning my wheels here w/ this cab?
Click to expand...

you could try parts-express.com and see what speakers work w/ that size cabinet. they may have a driver that's perfect for your cab. that kappa pro is obviously wrong for your cab.
 
#8
WinISD ProAlpha is much more detailed, but, something's not right there. Make sure all your measurements are in the correct Liters, cubic feet, inches, mm, or whatever.

How about a budget?

That cab is a little on the small side for some 15's but a few will work well in there.

Some choices.....

Emi. Legend CB158. Good lows, warmer/old school, not a lot of treble.

Emi. Kappalite 3015. Good lows, reaches higher, mid punchy.

Faital 15PR400. Smooth response, brighter than the others, still good lows.


A budget option would be the Emi. Beta15. I normally wouldn't put one in that small a box because they get a big response hump towards the lower end that can make boomy/muddy sound, but, your Hartke has a slider at 125hz which is pretty much the center of that boom. Could use that one to clean up the lows without losing the whole bottom end. That hump can help give you some "oomph" to the sound when playing outdoors, can cause problems indoors, especially in already bad sounding rooms.

Calculate two 4" ports, and a tuning probably in the mid 40's for most of these, a bit lower for the Beta.
 
#9
I went back and checked my numbers and I was imputing cubic feet rather than liters! I can't believe I didn't double check that before posting. Now the port length numbers look correct in correlation to the tuning Hz. I'm excited that this is starting to make sense. So now to my next question, What should I be looking at to determine which drivers would suite this cab or my tastes the best? The drivers I tried all plot about the same on the graph and I just really don't know what I should be looking at. What I would like, as far as "my sound", is a deep, defined tone - Reggae. I would also like to be loud in the low end, other cabs and amps I used in the past always sounded fine in the mids and uppers but always lacked in the low end. If I turn up, the speakers would always fart. I would always have to cut a little of the mids and upper spectrum and then I would loose my volume.

Thanks you guys, I appreciate your input and advice!
 
#10
It would seem as if these were designed for the older legend CB15

the older legend in WinIsd with a BB4 alignment will show specs very similar. around 3 cubic feet and tuned to Fs ( resonate frequency) which is around 34hz for the older and newer CB158

the 3" port at 5" length will tune approx 26 to 30hz
only down side is total port area which is a little small, would have high velocity. high velocity can cause "chuffing"

being that it is such a low tuning and on the back of the box
probably is no big deal. With such a low tuning
power handling could be lower, but since the total volume is
only 3 cubic. This should work well and almost behave like a sealed cabinet.

You could show a picture of the current speakers, if they are older legends.
A recone could be around 75dollars. You mention that the voice coil is scratching, so if the gap has been damaged then recone is not a option. only way to know if someone pulls the cone and inspects it. Not sure how nice of a recone guy you can find. But they might be able to inspect it for you with little or no charge.

Otherwise a newer Legend[Invalid or Expired Link Removed]will work fine for about 130dollars. The speakers are very similar, the older speaker has
a higher mechanical quality (Qms) which allows it to work in smaller boxes or sealed applications. So with a recone I would stay with the actual original cone part number. The newer legend can also go into a sealed or vented box 3 to 6 cubic feet. But the lower Qms leans more to a vented box, which is what you have...so all good.
 
#11
Ok, so after working with WinIsd for a little while, I finally think I got this figured out. It's actually not so difficult, the more time I work with it, the easier it gets and the more I understand.
So now I pose another question. Since I have two identical cabinets and I intend to cut new ports into these, would there be any benefit to tuning the two cabs differently. I plan on putting identical 15's in each cab, I'm leaning towards the Kappalite 3015, but still not decided. I was thinking about tuning one cab in the 35 - 40hz range and the other cab in the 40 - 45hz range. Would this cause any "phasing out" issues? I was just wondering... I really have no experience in audio design or the physics so I thought I would just ask, is this a dumb idea?
 
#15
Although curved may look similair, look at the max power graph. That shows you what xmax does for you.

As far as ports. For straight pipes, I use 20 meters/second at whatever power reaches xmax as a rule of thumb. 30 m/s for flared ports.

Probabpy gonna want a pair of 4" pipes in there for any decent speaker. Pair of 3" absolute bare minimum but I don't think that's enough. Too small of ports don't just make air noise, they can "choke off" the flow and make the actual box tuning, and thus tone, wander around at higher volumes.
 

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