Yet another diy cabinet question...

[zaubertuba]

I'm wading knee-deep through all of the great diy cabinet threads, but my situation is a little unique, so forgive the vanity of yet one more diy post:

I'm looking at picking up a half-fretless NS/Stick (currently playing a Megatar). After not playing for nearly 20 years, I just started playing predominantly Bass in a contemporary Jazz trio. Styles run from standard Jazz ballads to funkier gospel-rock oriented arrangements.

I have two cabinets I built 20 years ago but never loaded. The top cabinet is about 2.7 cu. ft. and I was originally planning on loading it with a pair of Eminence 10" woofers and perhaps a compression driver for highs. The bottom Cab. is 7.19 cu. ft. Haven't decided what I want to put in it, yet.

We plan on using P.A. for the larger venues, so SPL is not nearly as much an issue as even frequency response and tone clarity.

I'm already working on comping guitar lines/playing melodies over basic bass lines, so I'm wondering if it might sound better to break out the bass/guitar duties between the cabinets (for those that don't know the NS has separate outputs for the low and high sides of the instrument).

In which case, would it be better to go with, say, a single 15" and a 6" midrange in the large cab., then a 10" and a midrange or tweeter in the small cabinet?

I could go as far as a 4 x 10" and 2 x 10" but I don't need *that much* headroom and don't relish the thought of dragging that much extra weight around.

...Which also begs the question, would I be better off just combining the signals and sending them to a 2 x 10" enclosure for most gigs, anyway? Would that be enough for moderate volumes (including the low "B" string) in small-mediumish venues?

[will33]

The 7.19cu.ft. box nowdays would qualify for a 215 or possibly a 412. Don't know that it'd be neccesary to buy that many drivers or drag the thing around if you've got PA support on bigger stuff.

The 2.7cu.ft. one would likely end up as a 210, 112 or possibly 115 depending on the driver used and how low of a response you want.

If even freq. response and clarity of tone is what you want, I'd consider a woofer + 6"mid design. That'll catch all the useable harmonics of a bass guitar, tweeter isn't really needed but leave the option open just in case you want one in there down the road.

It's always best to choose the drivers that suit your needs best first and design the box around them but your small box is right in the ballpark for a 210 design. Could chop it down a bit for a 112 design. The big box could almost be split into a pair of 115's or chop it down to optimal size for an fearful style cab.

You should read up on the fearful threads, especially for the kind of clarity you're looking for from the funky stick bass thing. You could use a bit less expensive drivers and still get even response if you don't need all that excursion and SPL.

[zaubertuba]

Thanks for the tips! Those fearful threads are awesome!

I've been playing around with the WinISD. It's funny, maybe I haven't tried enough combinations, but between both the cabinets, it seems I can get the flattest *and*deepest response loading the small cabinet with a Legend BP102. When I go to two drivers, I get a hump in the 50 to 500 Hz range that I can't seem to make go away. Tried all sorts of port combinations too and I can't seem to make it much better.

What's really wierd is I tried a lot of 15" drivers in the big cabinet and nothing came out as good as the single 10" in the smaller cab.

I kind of like the idea of using an LA6-CBMR with a single 10" in the small cabinet. I would probably need an L-pad - the sensitivity is pretty far off between the two drivers. If I could get the sensitivity matched it seems the response would be really smooth.

But would it pump enough for a medium-sized venue (like a big coffeehouse)?

I might go to 2 x 10's if some judicious tuning could cut out the rise a bit. I expect there's things I can experiment with in real life (like cabinet stuffing) that could get me closer. With the higher sensitivity, would the LA6 balance better with the 2 x 10's?

[Sundogue]

I built a 210/6 cab using BP102's. It's so damned sweet sounding, from the deep (upper bass) lows through to the highs and the highs are very smooth without a tweeter. I'm building a duplicate of it to use two for bigger gigs. It's a poor man's Acme for me. Of course, while it handles a low B quite well, it does not produce the fundamentals of the low notes, but the BP102's are fabulous tens for low end. But you need a midrange driver with them because they lose it above 500Hz. I have it crossed over at 800Hz with the mid, so it has a bit of a scooped sound to it, though I can EQ it back in if desired.

My cab is 20X20X16, so there is that upper bass/low mid hump. Don't worry about trying to get rid of it. It helps cut through the mix and with the BP102's you can dial in the low end with EQ very nicely. They can handle it very well. I can also EQ the hump out easily too, but I never feel the need for it.

I use my 210/6 on all but the largest gigs and I have full PA support as well. I've played some fairly large gigs with it (that I usually used my 215 for) and it keeps up volume wise pretty good and I've pushed it pretty hard for those and it handles it well. Borderline though for the bigger venues, thus I want another. Best cab I've ever built (and that's saying a lot for me because I've built quite a few nice cabs over the years that are better than most of what's out there without spending a fortune).

Here's my 210/6

[zaubertuba]

That really is a great looking cabinet!

I realized the baffle on my small cabinet is too short to fit 2 x 10 plus a 6". Let alone a couple of vents.

So I played around with WinISD again. I realized if I cut the big cabinet down a bit, say by 10", I end up with a cabinet volume of 5.27." And a 20" x 24" baffle - plenty of room.

Response is not much different then the single in the smaller cabinet. Looks like I found something worth trying. I'll keep playing with it.

What 6" did you use, Sundogue?

And a little off-topic... ...how do you like that Zoom modeling unit? I've been looking pretty closely at that one (or maybe the next one up with the pedal).

EDIT: Seems like a waste of cabinet, but found out the BP102's really seem to work well in the big, 7.18 cu. ft. cabinet. Near-perfect flat response and only down -3dB at 30Hz. Going to 4 drivers pushes that point up to 40-50 Hz.

I couldn't get that with either a Kappa LF or Omega 15"!

[Sundogue]

Originally Posted by zaubertuba

That really is a great looking cabinet!

I realized the baffle on my small cabinet is too short to fit 2 x 10 plus a 6". Let alone a couple of vents.

So I played around with WinISD again. I realized if I cut the big cabinet down a bit, say by 10", I end up with a cabinet volume of 5.27." And a 20" x 24" baffle - plenty of room.

Response is not much different then the single in the smaller cabinet. Looks like I found something worth trying. I'll keep playing with it.

What 6" did you use, Sundogue?

And a little off-topic... ...how do you like that Zoom modeling unit? I've been looking pretty closely at that one (or maybe the next one up with the pedal).

The 6" is just some random stereo speaker I have of many lying around. I'm not even sure what brand it is. I have many little dedicated "mid" cabs I mess around with. I also use a Carvin BX1200 and bi-amp to test my cabs. Once I found a usable mid cab size that sounded good with that speaker, I just played around with the crossover points and output to balance the 6" with the 10's.

So for now I still bi-amp, though I will at some point get an Eminence 800Hz 2 way crossover for the cabs as that seems to be the best point that matches and it's an easy retrofit. I would imagine an Alpha 6 mid driver would work (can't recall the specific model #) with the BP102's. The BP102's are not very sensitive so one 6" matches up fairly well.

As to the off topic...your thread, post what you want. I like the ZoomB2 as it allows me to pretty much take "my" sound with me to some extent whether I play through my rig or not. It's nice to grab for band practice through a horrible Peavey Mark III head and an 1820 bottom or some pickup gigs through others amps. It only takes a little bit of tweaking an amp to dial in my sound as most of my sound is in the pedal. I use the effects sparingly and never have the need to use it as a "pedal" so I keep it on top of my amp.

[ColinB]

Going a little bit off topic...but something that's concerning me...

I know if you have two 8 Ohm speakers (in parallel) then that's 4 Ohms, but if you have two 8 Ohm speakers with a crossover splitting the signal, does the amp still 'see' 4 Ohms or does it behave like one 8 Ohm load.

Sundogue...have you got two 4 Ohm BP102's wired in series to give 8 Ohms, then crossed-over with an 8 Ohm 6" speaker to give a load of 4 Ohms or 8 Ohms???

Any help much appreciated.

[zaubertuba]

Originally Posted by ColinB

Going a little bit off topic...but something that's concerning me...

I know if you have two 8 Ohm speakers (in parallel) then that's 4 Ohms, but if you have two 8 Ohm speakers with a crossover splitting the signal, does the amp still 'see' 4 Ohms or does it behave like one 8 Ohm load.

Sundogue...have you got two 4 Ohm BP102's wired in series to give 8 Ohms, then crossed-over with an 8 Ohm 6" speaker to give a load of 4 Ohms or 8 Ohms???

Any help much appreciated.

Not off-topic - I was just wondering this very thing this morning.

I'm actually thinking I may go 1 10" x 1 6" in the small cab., then 2 10" x 1 6" in the large cabinet. In this case I'd try to wire both cabinets as close to 8 ohms as possible, so that I can parallel them to a near 4-ohm load. This way a well-selected amp will actually "scale" to the speaker configuration based on the load it sees.

But back to your question - I found the following links..

This has a specific discussion on crossovers at the end of the article: http://www.termpro.com/articles/spkrz.html

...and this one's *really* technical: http://sound.westhost.com/lr-passive.htm

Not enough time in the day - I'll have to read this in earnest tonight.

[ColinB]

Passive crossovers affect the load impedance "seen" by the amplifier, but the effect varies from frequency to frequency. For frequencies that fall within the crossover's passband, the crossover's impedance is very low – for practical purposes, zero. This means that you can forget about the crossover when dealing with frequencies within its passband. For all other frequencies, the crossover's impedance rises, and the farther the frequency falls outside of the passband, the higher the crossover's impedance.


Thanks for these articles - very informative. (The second was a bit too informative!)
My initial reading of the first article would indicate that if you have two 8 Ohm speakers with a crossover set at (say) 800Hz, then at around 800Hz the total resistance is 4 Ohms and the further you get away from 800Hz in either direction the closer it gets to 8 Ohms. The second article was well outside my range, but it was to do with calculating the total resistance of the speaker cab depending upon the 'slope' of the crossover frequency graph.

How this affects 'everyday' playing I don't know as we play a whole range of notes with all the harmonics as well. We wouldn't just produce an 800Hz sine wave for any appreciable length of time.

[billfitzmaurice]

Originally Posted by ColinB

My initial reading of the first article would indicate that if you have two 8 Ohm speakers with a crossover set at (say) 800Hz, then at around 800Hz the total resistance is 4 Ohms and the further you get away from 800Hz in either direction the closer it gets to 8 Ohms.

With a properly designed crossover the impedance will be 8 ohms nominal minimum across the full bandwidth. If it did dip to 4 ohms at the corner frequency the crossover would be poorly designed, if not outright defective.

[4Mal]

given the simplicity of the butt joint build process, why not invest $35 in a 5x5 sheet of 12mm Baltic Birch and build a fEarful 12/6. You'll only need 1 and it will probably be the best sounding cab you've ever heard ...

[NoGraveConcern]

Originally Posted by zaubertuba

EDIT: Seems like a waste of cabinet, but found out the BP102's really seem to work well in the big, 7.18 cu. ft. cabinet. Near-perfect flat response and only down -3dB at 30Hz. Going to 4 drivers pushes that point up to 40-50 Hz.

Are you looking at the maximum power curve at all? I suspect not as if you were you would realize how poorly a BP102 in 7.18 cu ft would perform. Not to be harsh, but designing for the deepest low frequency extension is a rookie mistake. There are many graphs in WinISD and you need to take some time to learn how they interact with each other.

The problem is that the BP102 needs a tight enclosure to keep it's excursion in check. Putting it in a giant box lets it move too easily which makes it more sensitive in the lower frequencies but actually creates a lower max SPL in the same low bass regions.

A BP102 looks usable in 1.5 cu ft @ 40 hz. At that configuration you gain aprox 4db in max SPL from 40-60hz over your big box setup and the driver can handle 85w at any single frequency above 32hz vs a lousy 30w in the big box.

Now, take a 3015LF and put it in your 7 cu box and you have a driver with enough excursion to handle the big air space for the full 450w throughout it's frequency range. The response curve is anything but smooth, but it would be a better choice none the less. Even better (as was stated above) would be 2 15's--C2515's + tweeter for a lower cost 8 ohm cab, 3015's for a classic sound @ 4 ohm, or 3015 LF's + a midrange for a flat response.

[uglyrumor]

Or you could find out what your amplifier's high-pass cut-off is, and if too low run a filter that cuts lows below about 35 HZ or EQ to obtain the same results. That would keep your speaker from over-excursion in a bigger box.

[NoGraveConcern]

No it wouldn't. That setup would start to unload below 90 hz. Needless to say, high passing at 90 would be counterproductive.

[billfitzmaurice]

Originally Posted by NoGraveConcern

The problem is that the BP102 needs a tight enclosure to keep it's excursion in check. Putting it in a giant box lets it move too easily which makes it more sensitive in the lower frequencies but actually creates a lower max SPL in the same low bass regions. .

That's not quite true. It's often assumed that a small box is necessary to 'control' excursion, and that's not really the case. But there does come a point of diminishing returns where box size is concerned, and with the BP102 1.5 cu ft would be it, going larger will allow it to go louder but at frequencies that are quite moot where electric bass is concerned.
OTOH your point being that newbies don't know how to interpret the data provided by WinISD etc. is dead on. The response one might assume is required is usually way off from what's really required, often by as much as an octave. And the factor that's almost always missed by newbies is the maximum SPL, which is limited by the combination of power, displacement and sensitivity. Most are aware enough to consider two out of the three, but in this case two out of three is bad.

[Sundogue]

Originally Posted by NoGraveConcern

Are you looking at the maximum power curve at all? I suspect not as if you were you would realize how poorly a BP102 in 7.18 cu ft would perform. Not to be harsh, but designing for the deepest low frequency extension is a rookie mistake. There are many graphs in WinISD and you need to take some time to learn how they interact with each other.

The problem is that the BP102 needs a tight enclosure to keep it's excursion in check. Putting it in a giant box lets it move too easily which makes it more sensitive in the lower frequencies but actually creates a lower max SPL in the same low bass regions.

A BP102 looks usable in 1.5 cu ft @ 40 hz. At that configuration you gain aprox 4db in max SPL from 40-60hz over your big box setup and the driver can handle 85w at any single frequency above 32hz vs a lousy 30w in the big box.

Now, take a 3015LF and put it in your 7 cu box and you have a driver with enough excursion to handle the big air space for the full 450w throughout it's frequency range. The response curve is anything but smooth, but it would be a better choice none the less. Even better (as was stated above) would be 2 15's--C2515's + tweeter for a lower cost 8 ohm cab, 3015's for a classic sound @ 4 ohm, or 3015 LF's + a midrange for a flat response.

+1

My 210/6 cab has an internal volume of about 3.2 cu. ft. and is tuned to 53Hz (which gave the best power handling without overexcursion). I'm a mid freak anyway and cut my deep lows, so the "upper bass/lo-mid hump" is what I want, though the BP102's handle the low end smoothly for what they are.

While these are some awesome speakers in the low end for a 10", I agree they definitely need a tighter enclosure and should not be tuned very low. 40Hz is even kind of low for me. I've had them in another cab at 45Hz. But to try and get fundamental notes out of a ten at any gigable volume is just not going to happen. At 6.2mm xmax, while good for a 10" is not going to handle those deep lows that well. Better served by pumping the harmonics above it. Loaded with the fairly heavy BP102's this little 40 lb. cab is really manageable due to it's small size...for a non neo cab.

And yes, there are some very good alternatives to the BP102. I like the BP102 tens because I happen to like the compressed lows when the tens are pushed a little. Now if I could just get my other 210/6 cab built and match them up with my Carvin BX1200 and a VT pedal, I'd be in tonal nirvana.

[zaubertuba]

Great comments, guys!

Originally Posted by NoGraveConcern

Are you looking at the maximum power curve at all? I suspect not as if you were you would realize how poorly a BP102 in 7.18 cu ft would perform. Not to be harsh, but designing for the deepest low frequency extension is a rookie mistake. There are many graphs in WinISD and you need to take some time to learn how they interact with each other.

Originally Posted by billfitzmaurice

OTOH your point being that newbies don't know how to interpret the data provided by WinISD etc. is dead on. The response one might assume is required is usually way off from what's really required, often by as much as an octave. And the factor that's almost always missed by newbies is the maximum SPL, which is limited by the combination of power, displacement and sensitivity. Most are aware enough to consider two out of the three, but in this case two out of three is bad.

Well, I am a rookie and a newbie. At 40 I guess I figure I can afford ask stupid questions. How else will I learn?

Truthfully, I always say "I know just enough to be dangerous," but one thing in WinISD that's giving me fits is that the Max Power graphs are giving me nothing, zilch, nada, for *any* of the designs I've tried (including the 1.5 cu ft/40 Hz scenario you suggest below). I must be doing something wrong, I guess it's back to RTFM for me.

The problem is that the BP102 needs a tight enclosure to keep it's excursion in check. Putting it in a giant box lets it move too easily which makes it more sensitive in the lower frequencies but actually creates a lower max SPL in the same low bass regions.

This makes sense to me from a physics standpoint, I mean, to oversimplify, I go much further and I might as well just suspend the driver in open space, right?

A BP102 looks usable in 1.5 cu ft @ 40 hz. At that configuration you gain aprox 4db in max SPL from 40-60hz over your big box setup and the driver can handle 85w at any single frequency above 32hz vs a lousy 30w in the big box.

Now, take a 3015LF and put it in your 7 cu box and you have a driver with enough excursion to handle the big air space for the full 450w throughout it's frequency range. The response curve is anything but smooth, but it would be a better choice none the less. Even better (as was stated above) would be 2 15's--C2515's + tweeter for a lower cost 8 ohm cab, 3015's for a classic sound @ 4 ohm, or 3015 LF's + a midrange for a flat response.

I'll play around with these...after I get WinISD figured out, that is.

Originally Posted by Sundogue

+1

My 210/6 cab has an internal volume of about 3.2 cu. ft. and is tuned to 53Hz (which gave the best power handling without overexcursion). I'm a mid freak anyway and cut my deep lows, so the "upper bass/lo-mid hump" is what I want, though the BP102's handle the low end smoothly for what they are.

While these are some awesome speakers in the low end for a 10", I agree they definitely need a tighter enclosure and should not be tuned very low. 40Hz is even kind of low for me. I've had them in another cab at 45Hz. But to try and get fundamental notes out of a ten at any gigable volume is just not going to happen. At 6.2mm xmax, while good for a 10" is not going to handle those deep lows that well. Better served by pumping the harmonics above it. Loaded with the fairly heavy BP102's this little 40 lb. cab is really manageable due to it's small size...for a non neo cab.

And yes, there are some very good alternatives to the BP102. I like the BP102 tens because I happen to like the compressed lows when the tens are pushed a little. Now if I could just get my other 210/6 cab built and match them up with my Carvin BX1200 and a VT pedal, I'd be in tonal nirvana.

I suppose I really am being a little unrealistic trying to squeeze so much bottom-end out of a 10" driver. I suppose I could loosen up a bit and try some other brands, too.

I keep forgetting most of the stuff I do is *not* going to require huge volume levels, either, but more and more drivers and options keep creeping in. I guess that's a diy'rs G.A.S.

Originally Posted by 4Mal

given the simplicity of the butt joint build process, why not invest $35 in a 5x5 sheet of 12mm Baltic Birch and build a fEarful 12/6. You'll only need 1 and it will probably be the best sounding cab you've ever heard ...

Yeah, I realize I'm being pretty stubborn. I guess the idea of finishing a project I started over 20 years ago weighs pretty heavy for me. I used high-density particle board in the cabinets--they've stood up with nary a ding after all these years putting up with use as moving crates and all sorts of other silly things. I wish I would have remembered the drivers I had in mind when I first built these things up. They probably don't make them anymore.

Thanks for all the comments and your continued patience! Keep 'em coming!

[NoGraveConcern]

Originally Posted by billfitzmaurice

That's not quite true. It's often assumed that a small box is necessary to 'control' excursion, and that's not really the case. But there does come a point of diminishing returns where box size is concerned, and with the BP102 1.5 cu ft would be it, going larger will allow it to go louder but at frequencies that are quite moot where electric bass is concerned.

Thanks for the correction.

Originally Posted by zaubertuba

Well, I am a rookie and a newbie. At 40 I guess I figure I can afford ask stupid questions. How else will I learn?

No worries. I've made the exact same mistake.

Originally Posted by zaubertuba

... but one thing in WinISD that's giving me fits is that the Max Power graphs are giving me nothing, zilch, nada, for *any* of the designs I've tried (including the 1.5 cu ft/40 Hz scenario you suggest below). I must be doing something wrong, I guess it's back to RTFM for me.

What you are doing "wrong" is using the BP102 model that comes with WinISD. It's incomplete and therefore doesn't have enough parameters to show max power, which is a frustrating thing.

Good practice is to Download the PDF from eminence and enter the driver data yourself as a new entry. Put in all the params including: sd (344.9 cm2), xmax (6.2mm) and pe (200w). Let WinISD calculate Qts. This will give you the necessary parameters for max power. The shortcut is to click xmax under parameters and just type in 6.2.

What I suggest you use as a rule of thumb for interpreting max power graphs is at least (ie no less than) 33% of your RMS power (PE) throughout the range of frequencies you will use. These frequencies start at 1 octave above the fundamental frequency of the lowest note on your bass. If you have a 5 string that's ~32hz x 2 = 64hz. I also like to see a reasonable power handling around the fundamentals themselves, though it's less critical.

Again, more mechanical power handling doesn't hurt, especially if you will be pushing the driver with an amp that has a little extra "headroom." However, 33% + has given me acceptable results in the past.

[NoGraveConcern]

Originally Posted by Sundogue

40Hz is even kind of low for me. I've had them in another cab at 45Hz.

I doubt you would be able to hear the difference between the 2 tunings (I know I couldn't), but the lower tuning gives a shorter peak and smoother low frequency rolloff. It's a minute and rather academic difference though and a matter of personal preference. Now that 53 hz might give you a noticeable mid-bass hump.