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Adding 6" mid-range driver to cab

#41
thudfromafar said:
It looks like the LA6-CBMR goes to about 5.5khz, but a good 4db cut around 3.5-4kz would even it out a bunch.

I'll probably have a go at this for a summer project.
NicJimBass, did you make any separate chamber/filling for the mid? How did you measure/cut the mid hole? How did you wire/mount the x-over?
If you don't mind :p
Click to expand...

As lbwdog said, this mid driver is a closed-back driver, so no separate chamber or box is needed. To cut the hole, I found a toy tambourine that one of my boys has, and I used that as my template. I took a utility knife and cut the carpet to the diameter of the tambourine. That gave me something to follow when I used my jigsaw to cut the majority of the wood out. Being that the wood I cut out is recessed from the front of the cab, I didn't have enough room to move the saw around on the top edge of the cut... I instead used a Dremel with a sanding bit to remove what was left.

The original crossover was much smaller than the Eminence I bought to replace it. I was planning to mount them the same way (to the back of the jack plate) but couldn't. I simply screwed the new crossover to the inside-back of the cabinet. Works like a charm. As far as wiring is concerned, it's really basic, as the crossover is labeled- 2 terminals for the input, 2 terminals to the woofer and 2 to the tweeter (mid). I used the wires that were originally attached to the Avatar crossover, as they already had the clips to connect to the drivers.
 
#42
NJB, I have a pair of Avatar 112s and have considered adding a midrange driver. One thing I'm concerned about is losing the "growl" that the stock woofer has. I assume the growl is due to distortion in the large woofer as it produces higher frequencies up to the stock crossover point (which has to be quite high, nearly full range). Did you lose any growl when you crossed it over at 1.6 kHz?
 
#43
bobcruz said:
NJB, I have a pair of Avatar 112s and have considered adding a midrange driver. One thing I'm concerned about is losing the "growl" that the stock woofer has. I assume the growl is due to distortion in the large woofer as it produces higher frequencies up to the stock crossover point (which has to be quite high, nearly full range). Did you lose any growl when you crossed it over at 1.6 kHz?
Click to expand...

Not that I've noticed.
 
#46
Wanted to resurrect this thread as I just finished up modding my other SB112 with a 6" mid driver. After reading on TB about possible phasing issues when it comes to drivers being apart from each other, specifically as it relates to midrange drivers, I decided to mod the 2nd cab with this in mind. On the first cab, I removed the tweeter, which, with the cabinet standing in its side was above and to the left of the woofer. On the 2nd cabinet, the mid driver is below and to the left, if that makes sense. I ran my cabs this way last night- both lying on their side (meaning they are wider than they are tall), stacked one on top of the other, with the original modded cab on the bottom. This way the 2 mid drivers were stacked one on top of the other.

Due in part to me being lazy, as well as because of a time crunch yesterday, I left the tweeter in the 2nd cabinet. Driving to my gig last night, I realized that my laziness could actually result in something cool- since I use a Gallien-Krueger head (700RB-II) I have the option to biamp, running the tweeter separately from the woofers, therefore eliminating the need for a 3-way crossover, which I had considered purchasing. The cabs came stock with 4-pole speakon jacks, so I simply wired the woofers, via the crossover, to poles 1-/1+, and the tweeter to 2-/2+. Unfortunately, I don't have a 4-connector Speakon cable to run it just yet, but I plan on getting one sometime in the future. I'm not a huge fan of tweeters, but I like having the option, in case I need just a little more sheen or sparkle, and with the GK head, I can add or subtract as much as I need from the front of the head, so I don't need to worry about adjusting an L-pad on the back of the cab.

Oh, I forgot to mention, I swapped crossovers, again. Obviously, the non-modded cab got a new one, but I also swapped the one in the modded cab. I originally went with an Eminence that was crossed over at 1.6k. Just to see what would happen, I popped a couple Eminence's in that are crossed over at 800hz. I like the new crossovers better... I still get plenty of lows, but now the mids seem to speak a bit better as well. Overall, my perceived volume seems to have increased a bit... not dramatically so, but I don't seem to have to turn my amp up as loud as I used to and I can hear myself just fine. :bassist:
 
#47
You did right by figuring out a positioning scheme where the mids were close together and vertical. Those crossovers are 3rd order HP, good protection and if I recall, the impedance curve of that closed back is pretty close to 8 ohms around 800hz so they should play well together.
 
#48
That sounds like a really good idea leaving the tweeter in and wiring the jack to use it with your GK head . That way you can adjust it with the tweeter volume on the head to match your cabs or turn it off with no ill effects . Sometimes being lazy works out for the good .
 
#49
#1 -- copy and paste everything Bill Fitzmaurice said into a Word document & print it out. He is giving you great advice based on TONS of experience, and using a closed-back mid, while possibly a bit harsh sounding, will save you a LOT of effort compared to building a mid enclosure.

#2 -- Go to the Erse audio website and use their crossover calculator to get the values for a 2-way Linkwitz-Riley crossover at ~1000 Hz. The components you get from Erse are both MUCH more heavy-duty AND less expensive than the pre-built Eminence crossovers, and if you wanted, you could even build an asymmetrical crossover; i.e. woofers go up to 1.5 k, but the 6" kicks in at 900 Hz or have a 6 dB/octave LPF for the woofers and a 12 or 18 dB/octave HPF for the 6".

It will sound MUCH smoother after the mod.
 
#50
Erse is quality stuff although with an overlap like you described you'd have a drop in impedance between 900 and 1.5k, possibly too low for the amp although I think the delta12LF is rising pretty good by then. The emi is 2nd order LP, 3rd order HP and in this case, the mids reading is close. That'd be my main concern....getting too close to fs and not passing steep enough but it seems to work. Being a closed back mid you can take that curve as it's in cab impedance.
 
#51
groovaholic said:
#1 -- copy and paste everything Bill Fitzmaurice said into a Word document & print it out. He is giving you great advice based on TONS of experience, and using a closed-back mid, while possibly a bit harsh sounding, will save you a LOT of effort compared to building a mid enclosure.

#2 -- Go to the Erse audio website and use their crossover calculator to get the values for a 2-way Linkwitz-Riley crossover at ~1000 Hz. The components you get from Erse are both MUCH more heavy-duty AND less expensive than the pre-built Eminence crossovers, and if you wanted, you could even build an asymmetrical crossover; i.e. woofers go up to 1.5 k, but the 6" kicks in at 900 Hz or have a 6 dB/octave LPF for the woofers and a 12 or 18 dB/octave HPF for the 6".

It will sound MUCH smoother after the mod.
Click to expand...

I like the idea of allowing the woofer to go higher than it currently does, while allowing the mid to work at a lower frequency. I'm looking at the crossover calculator, but having a hard time figuring out what I should be entering in order to get the asymmetrical design you mentioned...

Also, from what I've read on TB, the "order" of the crossover is essentially better, the higher the number (meaning second order is better than first order, third is better than second...etc), correct? Beyond that, I'm not really sure I understand what those designations mean, and what it translates to in sound output. Can anyone (briefly) educate me? :)

I ordered the components from Parts Express, so I can return the crossovers anytime in the next 45 days. If building my own will improve my sound, and will be cheaper and more reliable, I'd be stupid not to do it.
 
#52
NicJimBass said:
Also, from what I've read on TB, the "order" of the crossover is essentially better, the higher the number (meaning second order is better than first order, third is better than second...etc), correct? Beyond that, I'm not really sure I understand what those designations mean, and what it translates to in sound output. Can anyone (briefly) educate me? :).
Click to expand...
Passive Crossover Slopes
 
#53
billfitzmaurice said:
Passive Crossover Slopes
Click to expand...

Thank you very much Bill! I truly appreciate all the help you've given me through my experimentation!

I want to make sure I understand the concept of crossover rolloff. From what I gather, the higher the order, the more the frequencies that are being blocked are kept from the speaker... is that right? In other words, if I have a crossover point of 800hz, a 6db slope will allow more content above 800hz to leak through than a 24db slope will. IF this is the case, what order would be sufficient for what I'm doing, and what order would be overkill?

In order to build an assymetrical crossover, like the one mentioned above, would I be able to build it as one piece, similar to the Emi board, or would I need to build a separate LP and HP board, each with it's own frequency point and slope?
 
#55
Something that makes perfect sense, but never occurred to me until I got the plans for a Bill Fitzmaurice cab, was that the crossover does NOT have to be all on one board.

As I got more into the process, I learned that it's actually preferrable, for reasons of inductance, to keep your LPF (low pass filter), BPF (band pass filter) and HPF (high pass filter) as far from each other as is possible.

This isn't always easy; for instance, your BPF will probably have at least 2 inductors on it, so it's essential to learn about and consider how far apart the coils should be and how you orient them.

Anyhow, because these components are all going to separate filters, they COULD all have different cutoff frequencies, although, as has been posted, you could create some impedance issues at those crossover points if there is too much overlap.

But in my nEarful cabinet, I have three separate boards, as far from each other (and as close to the individual drivers) as is possible.
 
#56
NicJimBass said:
Thank you very much Bill! I truly appreciate all the help you've given me through my experimentation!

I want to make sure I understand the concept of crossover rolloff. From what I gather, the higher the order, the more the frequencies that are being blocked are kept from the speaker... is that right? In other words, if I have a crossover point of 800hz, a 6db slope will allow more content above 800hz to leak through than a 24db slope will. IF this is the case, what order would be sufficient for what I'm doing, and what order would be overkill?

In order to build an assymetrical crossover, like the one mentioned above, would I be able to build it as one piece, similar to the Emi board, or would I need to build a separate LP and HP board, each with it's own frequency point and slope?
Click to expand...


In general they will all pass 800hz and higher. The 1st order will be -6db @ 400hz, the 3rd order -18db @ 400hz blocking the lows at a steeper rate.
 
#57
groovaholic said:
Something that makes perfect sense, but never occurred to me until I got the plans for a Bill Fitzmaurice cab, was that the crossover does NOT have to be all on one board.

As I got more into the process, I learned that it's actually preferrable, for reasons of inductance, to keep your LPF (low pass filter), BPF (band pass filter) and HPF (high pass filter) as far from each other as is possible.

This isn't always easy; for instance, your BPF will probably have at least 2 inductors on it, so it's essential to learn about and consider how far apart the coils should be and how you orient them.

Anyhow, because these components are all going to separate filters, they COULD all have different cutoff frequencies, although, as has been posted, you could create some impedance issues at those crossover points if there is too much overlap.

But in my nEarful cabinet, I have three separate boards, as far from each other (and as close to the individual drivers) as is possible.
Click to expand...

+1

It also just makes it plain easier/simpler to keep track of everything.
 

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