12" cab, high power handling recommendations

[agedhorse]

Skeptical, because I want to hear what the voice coil is doing, and this seems to block it.

Why is that?

The voice coil doesn't generate ANY sound by itself, only when coupled to a cone do the vibrations get coupled to the air. Now, if you were to remove the dustcap, you get some diffraction radiation with all kinds of reflections coming off of the cone neck and the inside surfaces of the bobbin. Because of this, the dust cap material is chosen to block (or filter) much of this sound artifact. Even the JBL aluminum dust caps block what comes off of the inside of the (shallow) bobbin, and acts as a re-radiator because it couples to the edge of the bobbin and increases the effective higher frequency bandwidth. The drawback to this is a large increase in distortion in the last octave of its response which for many applications becomes pretty harsh. Generally, we choose a material such as fiber reinforced pulped paper with a specific thickness and density to intentionally filter out and reduce the these distortion artifacts. The dust cap often extends well past the edge of the bobbin which adds an additional low pass filter coefficient to the response. This is where the art of compromise can make or break a driver or speaker design.

With regard to not seeing the cone, perhaps if you look at some of the highest performance line arrays from JBL, RCF, L-Acoustics, Nexo, TurboSound, etc. you might be surprised that you can't see much of the cone in those top of the top of the line products either. It's part of the art of wave-guide technology, because every mechanical aperture and acoustic path carries with it benefits as well as disadvantages (depending on the application and the execution). I have extensive experience with these technologies (both as a user as well as having designed several commercial products in the pro audio side of the industry).

 

[bdplaid]

Why is that?

The voice coil doesn't generate ANY sound by itself, only when coupled to a cone do the vibrations get coupled to the air. Now, if you were to remove the dustcap, you get some diffraction radiation with all kinds of reflections coming off of the cone neck and the inside surfaces of the bobbin. Because of this, the dust cap material is chosen to block (or filter) much of this sound artifact. Even the JBL aluminum dust caps block what comes off of the inside of the (shallow) bobbin, and acts as a re-radiator because it couples to the edge of the bobbin and increases the effective higher frequency bandwidth. The drawback to this is a large increase in distortion in the last octave of its response which for many applications becomes pretty harsh. Generally, we choose a material such as fiber reinforced pulped paper with a specific thickness and density to intentionally filter out and reduce the these distortion artifacts. The dust cap often extends well past the edge of the bobbin which adds an additional low pass filter coefficient to the response. This is where the art of compromise can make or break a driver or speaker design.

With regard to not seeing the cone, perhaps if you look at some of the highest performance line arrays from JBL, RCF, L-Acoustics, Nexo, TurboSound, etc. you might be surprised that you can't see much of the cone in those top of the top of the line products either. It's part of the art of wave-guide technology, because every mechanical aperture and acoustic path carries with it benefits as well as disadvantages (depending on the application and the execution). I have extensive experience with these technologies (both as a user as well as having designed several commercial products in the pro audio side of the industry).

And my education continues...

I was under the (apparently mistaken) impression that a good deal of high frequency info came from the voice coil. Thanks for the correction and explanation.

OK, so now I am interested in that design by Genzler et al. Line array is good, and seeing it built as a virtual coax is interesting.

 

[agedhorse]

Not all high frequency reproduction by a cone transducer is good, and in fact a lot of carefully calculated effort goes into tailoring the response so that it is useful and balanced.

Note that line arrays have almost nothing to do with coaxial speakers (other these 3 examples one being placed in front of the woofer). There's a lot more going on with regards to maximizing what is used as constructive intereference in one plane while minimizing what is used as destructive intereference in the other plane, which is how pattern control is achieved in a line array. Of course it's not quite that simple, as the size of the driver, the spacing and the frequency all come into play with the resulting pattern, and effects that could otherwise be ignored (such as smoothness of off-axis response) factor into how well the execution performs in the real world.

In one product I developed (and is in production in a modified, evolved form), I was able to get better than expected real world performance because the off-axis response of the HF drivers (in this case 1,4" exit, 3"VC neo driver, a pro $600 horn-driver combo... not MI type stuff) was so smooth and even that lobe artifacts were almost buried under the primary response pattern. This is where you HAVE to understand the science behind the technology so that you can recognize all the goofy things BEFORE they can bite you in the ass. I tested this system from 3 boxes deep (tall) to 12 boxes deep and the response changes as the array grows, and then vertical splay factors in as well. There's a lot of data to be sifted through in order to get a meaningful set of practical response plots.

 

[Honch]

Yep. I gigged with one for several years very happily. IME most if not all coax drivers mated to 12s or 15s bring some fairly serious compromises compared to using a compression driver on a separate horn though, assuming the woofer portion needs to make deep bass and "hi-fi" is the game.

Yes, as far as I have heard, is that what works with wedge monitors in PA systems, and colorless replication of sound, where a PA amd powe amps needs to be clean, it doesn't make much sense in bass, say if you have an amp with dirt and grit to it, through tubes or whatever. It's going to have too many limitations. Passive crossovers can be made - today - IN BASS CABS/AMPS to overcome former limitiations os Hifi systems passive crossovers. At least most of them. The most limitation is that you're locked into and forced to use some kind of amps only, whereas you're allowed to vary your choice if it's not biamped, or coax. Barefaceds 12XN driver has extended response and superior dispersion, with the central dome running to ~10kHz - a concentric design would lose that. And so on and so forth. I e you're not forced to use separate tweeter and woofer today anymore, if one driver can cover that much up.

Coax (plus biamp) on stage monitors are a dream though. If you've ever been exposed to feedback from a vocal mike, you know what I am talking about. It's virtually nonexistent on coax plus active biamps of a PA wedge monitor. RCF comes to mind... there are others.

 

[Passinwind]

Coax (plus biamp) on stage monitors are a dream though. If you've ever been exposed to feedback from a vocal mike, you know what I am talking about. It's virtually nonexistent on coax plus active biamps of a PA wedge monitor. RCF comes to mind... there are others.

Yep. I love coaxes in the right applications.

 

[agedhorse]

Coax (plus biamp) on stage monitors are a dream though. If you've ever been exposed to feedback from a vocal mike, you know what I am talking about. It's virtually nonexistent on coax plus active biamps of a PA wedge monitor. RCF comes to mind... there are others.

Coax is just another tool, it's not the "end-all" because there are some serious challenges to pattern control because of the size of the horn mouth and flair rate. There are some excellent examples, the MicroWedge is one, that strikes a good balance by using VERY high quality drivers (and horn geometry) that are specifically tailored to work well as almost a diffraction type device rather than a true horn. When you look at the exit diameter, mouth area and length, you can see immediately that loading below say 2000Hz is almost zero, so the tradeoff is that you give up sensitivity (not a problem with the HF driver used) and live with a little distortion increase (also not a big problem for this HF driver) for somewhat more coherent point sources. Now of course, the MicroWedge is on the kind of expensive side of things, but the performance justifies it (for this particular speaker).

There are all kinds of really nice wedges in the $750 - $1500 range that are not coax, and some that are. Good wedges are just good wedges regardless of configuration IME.

 

[agedhorse]

Yep. I love coaxes in the right applications.

Exactly, right tool for the job is the key. I have a really nice hammer, it's an excellent hammer, but it doesn't work all that well on screws

 

[Honch]

I think british Tannoy did all kinds of studio monitors with coax. Don't know if they invented it though. I can think of some "crossover frequency" idiosyncrasies, and especially when you crank them up, but all in all I think a "one point source" should be beneficial in all areas. My domestic hifi system has one of those, and you don't have to be in the sweet spot to hear true stereo, you can sit, stand, lie a bit "askew".

That's why I don't generally have bass cabs with multiple drivers in them (8x10) or (4x10). Standing next to them makes certain holes and comb filter effects. I've been more and more interested in "single drivers" thing. For some strange reason. It has to do with both transient response and so on. One of my friends had once a "tired" cab of a 4x10, on a huge stage, miked up, not DI:ed. It had bad transient response, i e when a note stopped the cone didn't move back as fast. So, the trick was to let the cab reside on its back on the stage floor and miked it up, so the direct sound went straight up to the roof. Soundman liked it, band liked it, and the speaker cone retracted back sooner because of the gravity that pulled it back! Well, it was a one time solution, because when he finally bought a new cab those idiosyncrasies where gone.

 

[agedhorse]

I think british Tannoy did all kinds of studio monitors with coax. Don't know if they invented it though. I can think of some "crossover frequency" idiosyncrasies, and especially when you crank them up, but all in all I think a "one point source" should be beneficial in all areas. My domestic hifi system has one of those, and you don't have to be in the sweet spot to hear true stereo, you can sit, stand, lie a bit "askew".

Well, Tannoy is a company I'm "kinda-sorta" familiar with in more than a roundabout way. The "coaxial" devices you are thinking about, (and they have several technologies that they have patents on), called dual-centric, are actually quite unique in that there are not 2 separate drivers but a single driver (or more accurately a single motor) that supports 2 voice coils OR a single magnet and HF voice coil that couples through flux only (no wires). What all have in common is the location of the HF point source very close to the LF point source, but the earlier versions with the smaller horn flairs are not as suitable for live use because of the sensitivity (and HF power handling in the non-ICT models). Later models and those more suited to live use use a horn flair extension that covers much of the cone in the horizontal plane. Incidentally, for their larger PA products (that were not very successful here in the states at least) there were models that were not dual-concentric.

That's why I don't generally have bass cabs with multiple drivers in them (8x10) or (4x10). Standing next to them makes certain holes and comb filter effects. I've been more and more interested in "single drivers" thing. For some strange reason. It has to do with both transient response and so on. One of my friends had once a "tired" cab of a 4x10, on a huge stage, miked up, not DI:ed. It had bad transient response, i e when a note stopped the cone didn't move back as fast. So, the trick was to let the cab reside on its back on the stage floor and miked it up, so the direct sound went straight up to the roof. Soundman liked it, band liked it, and the speaker cone retracted back sooner because of the gravity that pulled it back! Well, it was a one time solution, because when he finally bought a new cab those idiosyncrasies where gone.

So ponder this before accepting the above explanation as "fact". Laying the cabinet on its back may "appear" to work this way but on;y for 1/2 of the cycle. What happens for the other half of the cycle when the cone is accelerated inward. In this scenario, the speaker would perform worse on one half cycle and better on the other for no net difference. The "transient" theory is bunk. What did change was the acoustic environment that the speaker was being aimed towards, and since the acoustic environment is one component in the calculation of acoustic Q (or resonance) of the response, so changing this can change the APPEARANCE of "transient response" (which is a bad description anyway since this simply translates to bandwidth).

There are a lot of bizarre theories out there, but there's a lot of science behind what is really happening. Understanding the science is key to debunking the theories and myths that surround amateur acoustics. Without the science, developing and debugging speaker and driver designs (not to mention room acoustic designs) would be phenomenally difficult at best... or even impossible.

 

[Kirk Bryant]

When I read a whole thread like this one I sometimes wonder why I try to understand all this stuff. 80% of it is over my head but I keep telling myself I'll learn something. I have, I've learned to listen to the advice of people I respect as knowing a lot more than I about this. I've also learned to trust my ears. My ears tell me that most of the most respected people in the bass speaker business make cabs that sound good to my ears. Bergantino, Fearfull, Baer, Audiokenisis, etc. and so by association I infer I will probably like others high end builders such as Barefaced, Genzler, M.A.S. And others. I also find I'm less impressed with the run of the mill widely available name brand manufacturers such as Fender, GK, Ampeg etc. and I don't mean to say they're bad just not that bit better that my ears have come to be more pleased by. Could I gig with them, of course I could. But I'd rather have the gear I have now than some of the more generic offerings. It is a great time for bass gear as many have said before. God bless you guys who keep on pressing the envelope to give us these increments of improvement. Oh I play Bergantino and I moved to them from Aguilar. Before that Schroeder, GK, Eden, SWR, in that order. I still have an old Sunn w/JBLs that still sounds good too! Just not as good as my new stuff.

 

[Honch]

So ponder this before accepting the above explanation as "fact". Laying the cabinet on its back may "appear" to work this way but on;y for 1/2 of the cycle. What happens for the other half of the cycle when the cone is accelerated inward. In this scenario, the speaker would perform worse on one half cycle and better on the other for no net difference. The "transient" theory is bunk. What did change was the acoustic environment that the speaker was being aimed towards, and since the acoustic environment is one component in the calculation of acoustic Q (or resonance) of the response, so changing this can change the APPEARANCE of "transient response" (which is a bad description anyway since this simply translates to bandwidth).

There are a lot of bizarre theories out there, but there's a lot of science behind what is really happening. Understanding the science is key to debunking the theories and myths that surround amateur acoustics. Without the science, developing and debugging speaker and driver designs (not to mention room acoustic designs) would be phenomenally difficult at best... or even impossible.

Well, that was a one off kinda thing, with the quick and dirty solution. It was very very old and taxed drivers. Actually, speaker drivers wears out too, in time. On some, in no time at all. It was a wild idea, that worked once only. Nothing I recommed to bring some mumbo jumbo fairy dust better sound to anything. New speakers will beat that one i all areas, 1/2 cycle Full cycle and anything in between.

 

[agedhorse]

Speakers should NOT wear out for decades if reasonably powered, and not stored in a damp environment (mold), nor exposed to strong direct sunlight (UV light).

Speakers are a linear spring-mass system that, like a spring, will last a very long time with no degradation as long it is not driven beyond its elastic (linear) limits. This is one reason I make the (typically) more conservative powering recommendations that I do.

I have pro audio sub drivers with maybe 20 years of touring on them, still match up to the original manufacturer's TS specs. and work as well as the day they were new. They are also powered at less than 1.25x the "continuous" or "RMS" rating.

 

[bdplaid]

Not all high frequency reproduction by a cone transducer is good, and in fact a lot of carefully calculated effort goes into tailoring the response so that it is useful and balanced.

Note that line arrays have almost nothing to do with coaxial speakers (other these 3 examples one being placed in front of the woofer). There's a lot more going on with regards to maximizing what is used as constructive intereference in one plane while minimizing what is used as destructive intereference in the other plane, which is how pattern control is achieved in a line array. Of course it's not quite that simple, as the size of the driver, the spacing and the frequency all come into play with the resulting pattern, and effects that could otherwise be ignored (such as smoothness of off-axis response) factor into how well the execution performs in the real world.

In one product I developed (and is in production in a modified, evolved form), I was able to get better than expected real world performance because the off-axis response of the HF drivers (in this case 1,4" exit, 3"VC neo driver, a pro $600 horn-driver combo... not MI type stuff) was so smooth and even that lobe artifacts were almost buried under the primary response pattern. This is where you HAVE to understand the science behind the technology so that you can recognize all the goofy things BEFORE they can bite you in the ass. I tested this system from 3 boxes deep (tall) to 12 boxes deep and the response changes as the array grows, and then vertical splay factors in as well. There's a lot of data to be sifted through in order to get a meaningful set of practical response plots.

We should have a thread that is just the thoughts of agedhorse.

 

[bdplaid]

Speakers should NOT wear out for decades if reasonably powered, and not stored in a damp environment (mold), nor exposed to strong direct sunlight (UV light).

Speakers are a linear spring-mass system that, like a spring, will last a very long time with no degradation as long it is not driven beyond its elastic (linear) limits. This is one reason I make the (typically) more conservative powering recommendations that I do.

I have pro audio sub drivers with maybe 20 years of touring on them, still match up to the original manufacturer's TS specs. and work as well as the day they were new. They are also powered at less than 1.25x the "continuous" or "RMS" rating.

I guess this is why I still have those EV 15L speakers that still work like new.

 

[CL400Peavey]

We have to get past this 'more power get's you louder' argument. Especially into a single speaker cab. More speakers will get you louder. Putting 800+watts into a speaker with an honest thermal rating of 400w is nuts. Why? It's not going to get any louder. Are your bands that frikkin' loud on stage? No PA support? What happened to finding efficient speaker cabs that will kill with 500w?I frequently do R&B gigs using a GK MB200 into a 4ohm Eden 212 cab. Plenty loud with bands that keep stage volume nominal.

Soapbox moment over. Carry on.

I think you need to understand that not everyone's gig is the same, and different tools work for different tools (people) in different settings.

 

[bdplaid]

Exactly, right tool for the job is the key. I have a really nice hammer, it's an excellent hammer, but it doesn't work all that well on screws

That all depends...

 

[bdplaid]

I think you need to understand that not everyone's gig is the same, and different tools work for different tools (people) in different settings.

That's really true. I've always been the type who buys as much powers as he can afford, in the idea of improved headroom (i like clean clean clean). However, I recently discovered that the right size amp is just right. The amp works just hard enough to get the tone you want at the right volume. 500W is about right for me.

 

[bdplaid]

When I read a whole thread like this one I sometimes wonder why I try to understand all this stuff. 80% of it is over my head but I keep telling myself I'll learn something. I have, I've learned to listen to the advice of people I respect as knowing a lot more than I about this. I've also learned to trust my ears. My ears tell me that most of the most respected people in the bass speaker business make cabs that sound good to my ears. Bergantino, Fearfull, Baer, Audiokenisis, etc. and so by association I infer I will probably like others high end builders such as Barefaced, Genzler, M.A.S. And others. I also find I'm less impressed with the run of the mill widely available name brand manufacturers such as Fender, GK, Ampeg etc. and I don't mean to say they're bad just not that bit better that my ears have come to be more pleased by. Could I gig with them, of course I could. But I'd rather have the gear I have now than some of the more generic offerings. It is a great time for bass gear as many have said before. God bless you guys who keep on pressing the envelope to give us these increments of improvement. Oh I play Bergantino and I moved to them from Aguilar. Before that Schroeder, GK, Eden, SWR, in that order. I still have an old Sunn w/JBLs that still sounds good too! Just not as good as my new stuff.

This!

 

[CL400Peavey]

That's really true. I've always been the type who buys as much powers as he can afford, in the idea of improved headroom (i like clean clean clean). However, I recently discovered that the right size amp is just right. The amp works just hard enough to get the tone you want at the right volume. 500W is about right for me.

I get it. I either use 400 watt tube amps, a 1000 watt micro, or a multi kilo watt pre/power set up.