lobing of drive units

[gedlee]

Mixing engineers are not super human. The limited capabilities of their equipment will affect the results.

 

[meko]

Mixing engineers are not super human. The limited capabilities of their equipment will affect the results.

Absolutely. No question about that.

1) The "way old" days of RCA and JBL dual drivers used curved plumbing to manifold 2" exit drivers, which eliminated the lobing from multiple horns, but caused some serious dips and peaks in the response. Gunness mid 1980's manifolds reduced the response dips and peaks, but the higher powered drivers used revealed the new problem of 10 pounds of SPL shite in a 5 pound throat.
And yes, throat width must be limited to less than a wavelength to avoid dispersion and bandpass problems.

Hey Art (or anyone else that likes to chime in), could we talk more about these manifold systems?
I would like to understand what exactly is going on here. The very old, "curved" plumbing manifold adapters had some periodic cancellations and peaks in their response, because of the acoustically large dimensions of the cavities and the "intuitive" way they were bent (as if it were just plumbing for water), as I understand it.

David Gunness designed his "MT" manifolds for EV in the mid-80s that still were acoustically large internally as I understand, but because they were, he treated the sound as if it were something like "light", where he let it reflect off of flat surfaces to join the multiple outputs in a more coherent and "in-phase" manner.

So if we look again at the pathlength-correcting adapters from turbosound or any other manufacturer of a similar design, we see "intuitively" bent paths again, but this time it works because of the acoustically small dimensions.

In Danley's patent ("paraline") he mentions that in bent/curved pathways that are acoustically small, the difference between the outer and inner path distance of any tunnel must be kept lower than 1/3rd wavelength of the highest desired frequency. So if we would follow all these rules using acoustically small paths, we could still join the outputs of two compression drivers in a way that is not creating a slim line source termination, but rather a compact, circular or square in-phase entry into a (circular) horn that radiates classical spherical wavefronts, couldn't we?

So if we would actually try to join two 2" exit drivers that way, we would of course need to allow for more horn throat diameter in order to actually increase max possible output without increasing throat distortion, but that would compromise our HF performance because of the larger throat.
Two times the area of a 2" exit is equal to a circular throat of ~72mm in diameter.
Those 72mm are the wavelength of around 4800 Hz.

So, I am seeing that as an option for the 2" band. The pathlength-correcting systems to join the outputs could be kept a little more minimal compared to those that aim at creating a line-source and a (circular) sphercial wavefront-horn could be used.

Any thoughts on that?

Thanks so much!

 

[weltersys]

In Danley's patent ("paraline") he mentions that in bent/curved pathways that are acoustically small, the difference between the outer and inner path distance of any tunnel must be kept lower than 1/3rd wavelength of the highest desired frequency. So if we would follow all these rules using acoustically small paths, we could still join the outputs of two compression drivers in a way that is not creating a slim line source termination, but rather a compact, circular or square in-phase entry into a (circular) horn that radiates classical spherical wavefronts, couldn't we?

You could in theory, but will still have ragged frequency response and the problem of air distortion if you cram the output of two drivers into a throat sized for one.

 

[meko]

You could in theory, but will still have ragged frequency response and the problem of air distortion if you cram the output of two drivers into a throat sized for one.

Thanks for the reply! I think I was not very clear with what I said:

Two times the area of a 2" exit is equal to a circular throat of ~72mm in diameter.
Those 72mm are the wavelength of around 4800 Hz.

What I meant was that I would double the area of the throat when the two drivers enter the throat, with all the consequences it has for HF performance, since I would be crossing over at about 5k anyways (which creates a lot of problems again).

I wonder just how bad the response will get in comparison to a "perfect" circular horn directly loaded with just one driver. I guess there is just one way to find out... damn.

What do you think of coaxial-style horn setups?
I am thinking of mounting a very slim vertical line source radiating 5k and up in front of the 2" driver horn that plays from ~500 up to 5k, time aligned.
I guess after reaching a certain listening distance, lobing would be not so bad with such an arrangement.

 

[weltersys]

What I meant was that I would double the area of the throat when the two drivers enter the throat, with all the consequences it has for HF performance, since I would be crossing over at about 5k anyways (which creates a lot of problems again).

What do you think of coaxial-style horn setups?

I like the Synergy concept for coaxial-style horns. I also don't find well executed multiple individual horns to be problematic at appropriate listening distance.

Rather than using two 4" diaphragm drivers to do <1000 Hz "grunt work" I prefer using larger horn loaded cone speakers for that range. There are many that cover a decade nicely, look at the Turbosound Flashlight and floodlight for examples.

But that approach still has lobing, if you want to avoid lobing, the Synergy or Co-Entrant approach is the way to go.

 

[meko]

Rather than using two 4" diaphragm drivers to do <1000 Hz "grunt work" I prefer using larger horn loaded cone speakers for that range. There are many that cover a decade nicely, look at the Turbosound Flashlight and floodlight for examples.

Thanks, I'll look into those more closely. good points about the "grunt work". Though the JBL 2482 are probably among the very best compression drivers for that, I guess I could rethink the crossover region. I am planning to use the B&C 8MDN51 (8") below the compression drivers, so these would easily play up to 1k, though I'd have to cook up a proper phase plug system for that.

On another note, I have to admit I don't like the thought of an army of those 10kg+ Alnico or Ferrite comp drivers. It is really madness. Are there any non-metallic / plastic ultra high efficiency neodymium drivers out there? All I see is Ti and Al. And Be of course, but well... that would be rather extreme. And I never heard one.

I also don't find well executed multiple individual horns to be problematic at appropriate listening distance.

okay, that gives me a bit of hope again
Thanks Art!

 

[meko]

Hmm... looking at the turbosound designs and funktion one again, I am yet another time intrigued to ditch the large-scale compression drivers altogether and go with something like 6.5" cones or smaller for the range up to 6...7...8k or even higher. Tough one.

 

[weltersys]

Are there any non-metallic / plastic ultra high efficiency neodymium drivers out there? All I see is Ti and Al. And Be of course, but well... that would be rather extreme. And I never heard one.

You can listen to the difference between non metallic BMS neo and ceramic, EV & Eminence titanium, and B&C combination plastic & titanium and one old aluminum diaphragm driver here:

http://www.diyaudio.com/forums/multi-way/212240-high-frequency-compression-driver-evaluation.html

So far, no one has mentioned any differences in how they sound after being equalized flat, other than at very high SPL levels where each has a different distortion signature.

BMS makes co axial plastic diaphragm compression drivers, which does allow a wider range to be covered without diaphragm breakup, but the <1000 output seems no higher than a 2482.

Curt Graber may have the ultimate device for what you want to do, his TCPA tandem transducer compression phase plug using two M5 drivers per waveguide cover 250hz-5Khz and up to 147dBA 1m at full rated power (500 watt) and the total weight of the entire device is 21 lbs.

 

[meko]

Oh Art, you never seem to run out of goodies. Amazing, thanks!
Your driver evaluation is completely nuts, why have I not seen this before...

I am really confused about BMS- I think I never heard one and I just read so many completely opposing opinions about them... kind of hard to make up my mind about this. Their coaxial drivers are no option for me anyways since I want to limit octaves per horn, and their high-eff mid-only options are very expensive, so other concepts appear more attractive.

Because you mentioning Curt Graber I just discovered the Hyperspike range of products and it is quite amazing, I am surprised I have not stumbled upon this before. I then discovered your HyperboLine-System - great stuff, really! It is funny, just yesterday I was thinking about using parabolic dishes as a means to create planar waves for completely in-phase HF radiators. Insane stuff.
Still have not understood what the 12" driver inside the Meyer Sound SB-1 is exactly playing. Oh well... lots to learn.

Thanks again Art.

 

[gedlee]

I am really confused about XXX - I think I never heard one and I just read so many completely opposing opinions about them... kind of hard to make up my mind about this.

This is a big reason why I pay no attention to opinions and focus on objective data. While it may not be perfect, it is far better than the wildly variant opinions that one always gets on this and any other topic. Let the data guide your decisions and you won't be sorry. Listen to opinions and it is a crap shoot. Listen to enough opinions and its certain that many (most!?) of them will be wrong. Getting an optimum design with such an approach is impossible.

 

[ErnieM]

Art,

You should put a link to your comparison in your signature line.

 

[meko]

Getting an optimum design with such an approach is impossible.

Best piece of advice. Thanks Earl.
It is a problem that today's culture experiences in an extreme form. Big, big topic.
One more bad thing about all these opinions is that it just wears you out and makes you lose sight of the picture. Very decelerating.

Art,
You should put a link to your comparison in your signature line.

+1

 

[head_unit]

...Anyways, a lot of control room monitors are close to CD.

You mean, a lot of control room monitors are CLOSE!

I also agree, a good engineer/mixer/mastering engineer can hopefully listen past/listen "into" their speakers and imagine what the sound will be like on a variety of systems

 

[weltersys]

Because you mentioning Curt Graber I just discovered the Hyperspike range of products and it is quite amazing, I am surprised I have not stumbled upon this before. I then discovered your HyperboLine-System - great stuff, really! It is funny, just yesterday I was thinking about using parabolic dishes as a means to create planar waves for completely in-phase HF radiators. Insane stuff.
Still have not understood what the 12" driver inside the Meyer Sound SB-1 is exactly playing.

Considering Curt's Hyperspike-60 is literally the loudest loudspeaker in the world (Guinness World Book approved), it is surprising more people are unaware of his work, but his products are not "aimed" at the usual PA or consumer audio market.

The 12" cone driver at the center of the Meyer SB-1 is used to cancel out off axis mid range spill, it is playing what is sometimes called "anti-sound" creating phase cancellation of the lobes in the 500 Hz range where the pattern of the dish becomes relatively wide compared to the nominal 10 degree conical dispersion.

 

[meko]

The 12" cone driver at the center of the Meyer SB-1 is used to cancel out off axis mid range spill, it is playing what is sometimes called "anti-sound" creating phase cancellation of the lobes in the 500 Hz range where the pattern of the dish becomes relatively wide compared to the nominal 10 degree conical dispersion.

Thanks Art! I have read the Meyer patent for the SB-1 concept and a couple of Curt Graber's patents as well and I think I have a better understanding of these reflector systems now.

Am I correct that the dish in the SB-1 is the bare "minimum" size to properly reflect and direct 500Hz and thus the complicated side-lobing control with calculated cancellations was necessary? Am I correct that 500Hz could have been precisely directed with both an adequately sized waveguide and dish and without a seperate dispersion-control driver?

Meyer states that they designed a "special" horn shooting into the SB-1 dish to counteract the beam's tendency to be narrowing as frequency rises.
Looking at the drawings, it seems to be a conical horn (to precisely define the angle in order to hit the dish and nothing else I suppose) that features a rapid increase of the included angle at the mouth. Is that what they are talking about, similar to something like Keele's designs that double the included angle near the mouth to counteract beaming HF?
So the thing I am having trouble with is this: is the narrowing beamwidth more a property of the parabolic mirror itself or of the waveguide shooting into the mirror?

And Art, I'd be interested in how you experienced HF pattern behaviour in your HyperboLine prototype. Thanks so much!

 

[weltersys]

1)Am I correct that the dish in the SB-1 is the bare "minimum" size to properly reflect and direct 500Hz and thus the complicated side-lobing control with calculated cancellations was necessary?
2)Am I correct that 500Hz could have been precisely directed with both an adequately sized waveguide and dish and without a seperate dispersion-control driver?
3)So the thing I am having trouble with is this: is the narrowing beamwidth more a property of the parabolic mirror itself or of the waveguide shooting into the mirror?
4)And Art, I'd be interested in how you experienced HF pattern behaviour in your HyperboLine prototype. Thanks so much!

1) My guess is the dish is near large enough, but a horn with pattern control down to 500 Hz would obstruct a good portion of the dish, making for more problems.
2)Yes. Long ago I tried a narrow pattern horn and a 60" dish and don't think the side lobes were huge, but at the time did not measure the side lobes carefully.
3) Combination of the two.
4) I think that was covered in the Hyperboline threads.
On axis, the transient detail is pretty amazing considering the drivers used.
If you want to experience the HF pattern first hand, three of the prototypes are available cheap !
Cheap being $150 for three (72 drivers) plus shipping from 87505 (Santa Fe NM).

The remaining prototype has been converted to a pair of mini line arrays, also available pretty cheap.

Art

 

[meko]

Hi Art, thanks for the reply and please excuse my late reaction.

1) My guess is the dish is near large enough, but a horn with pattern control down to 500 Hz would obstruct a good portion of the dish, making for more problems.

Ah yeah, that totally makes sense.

3) Combination of the two.

Alright, I think I understand. I was wondering lately- is it true that reflectors behave somewhat similar to horn's bandwidths when it comes to dimensions of the structure vs. dimensions of the wavelengths involved?
I mean- is there an upper frequency limit for any given reflector system size where it would always start to negatively affect the dispersion pattern? or could you fire multiple mid/high horns of different bandwidths into one big reflector (offset dish) and really get 5-6 octaves or so out of it?


thanks, I'd love to hear your array, but I live in Germany and that makes these things almost impossible.

kind regards!

 

[mayhem13]

1) Your problems will be made much greater using separate mid and HF drivers and horns in a line array. Though I have fond memories of the 2482, I would not consider it (or any other driver not going up to around 16 kHz) for line array use.
2) The 8" mid drivers cross over to the DH1AMT/Paraline acoustically around 1000 Hz, the electrical crossover for the mids is lower.
3)The Paraline makes the frequency response far rougher than it would be on a conical horn. I don't recall saying "slightly altered", though the response can be corrected with EQ, the deviations are fairly major as can be seen in the comparison of a DH1AMT on a conical horn, on a Paraline, and 5 Paralines with mids equalized. Both non-smoothed and smoothed (as seen in most charts) are shown.
With EQ correction, nothing "weird" about the sound quality, and the pattern control is excellent, so everyone gets to hear a very similar presentation even though multiple drivers are used.

Given your explanations for high SPL applications, I would assume for home use you would prefer a single waveguide matched suitably to a woofer whose crossover points would mate their directivity?......OR....would a Paraline approach still be preferred IF the rough response could be eliminated without extrem eQ?

I bring this up as I've always been impressed with coincident drivers and the one audition of a Synergy system but could always detect some discontinuity with waveguides mated to a single midwoofer. My thoughts recently have centered around a hybrid approach with two or more planar/ribbon HF devices stacked vertically flanked on either side with multiple 2-2.5" Fullrange type drivers which would allow for very tight C to C spacing yet would meet efficiency and SPL requirements for home use and small event installations......sort of the general principle of Peavey's Versarray without the side flanking large format woofers.
Thoughts?