Driver Evaluations for a new project

[Evil Twin]

Working from the top down, starting with the treble unit.

Not to be compared with any other specific tests; all testing conducted on a finite baffle; 9" wide, 22" tall, rounded edges; representative of somewhat typical enclosure dimensions.

Curves taken on axis, 15 , 30, and 45 degrees off axis.

Distortion plots taken with drive adjusted for 90 dB output at 1 meter.

There are many possible selection criteria- SPL linearity, off axis response, distortion; even so, considering the many ways in which drivers can differ, which are most important? You will have your criteria; I will have mine.



Seas 29TAFW







This is a newer driver in the Prestige Series from Seas. Hard dome, with a shallow waveguide that covers the magnetics mounting screws. Off axis behavior is not unexpected, with no phase shield.
Distortion is quite low above 3-4 kHz for a tweeter in this price class
Response droop at 45 degrees or even 30 degrees is unfortunate- perhaps we should name this the Needa tweeter, for another underperformer, Captain Needa. More basically, we Needa 'nother tweeter.



Seas 27TBFCG







Here we have a tried and true Storm Trooper. Not very pretty, with the Hexgrid cover, but get's the job done surprisingly well, considering the low resource allocation. Due to it's phase shield, response holds up well to 15 kHz even to 45 degrees off axis. 30 degrees off axis looks as good as many competing models on axis.
Third order distortion is quite low from 2 kHz up.
And, most importantly, it comes in black.


Seas 27TDFC




Seas 27TAFNCG







This driver is used in the NHT Xds system. Frequency response holds up well to 30 degrees off axis, and the distortion in the range above 3 kHz is consistently low, though not matching the levels of some of the better performers.



RS28a







A long time favorite in many parts of the Rebel Alliance, there are similarities of design with the 27TBFCG. But off axis response doesn't hold up quite as well. Distortion is comparable to the Seas, though differing in details. Above 5 kHz it is almost vanishingly low. And as it too, is black, and doesn't have a hexgrid cover, this may edge it ahead of the Seas for those not seeking as much output at 15 kHz and 45 degrees off axis.


Focal Tc120tdc



Seas Millenium Excel







The Millenium Excel has been a long time favorite of the high end DIY crowd in the early part of the 21st century, and is used in some well known designs, including the Thor, and Sigfried Linkwitz's Orion. Is it past the sale date at this point? The upper range distortion is fair but not stellar, but note that it doesn't increase significantly at 90 dB all the way down to 1 kHz. Is this a better trade-off? This sample and it's sibling have never displayed displayed the ruler flat frequency response some claim for this tweeter, not even when measured by MarkK.

Accuton C30N-6-24







Now we have reached the Grand Moff price class. Note the difference in the on and off axis curves of this hard dome without phase shield, compared with the Seas 29TAFW above. Could there be something to the concept of an inverted dome tweeter?
Distortion plots show clear evidence of resonant amplification of harmonic products; and also suggest that a crossover point above 2 kHz is advisable.

Accuton C25N-6-13



Scanspeak D3004/662001







The last to be acquired and tested for this lineup, it exhibits some interesting and puzzling characteristics.

The on and off axis curves seem to indicate substantial effort in the dome and waveguide design to optimize off axis behavior- 45 degrees at 15-17 kHz nearly match the reference level. Overall, it will probably have the most subjectively flat response off axis.

Distortion is intriguing but puzzling- the 2nd order distortion is actually reasonable in level, but looks high because the 3rd order distortion is so much lower- about 20 dB lower. At 2 kHz, the only competitor is the 27TBFCG; above 3 kHz, there is no competitor for 3rd harmonic distortion; it IS vanishingly low, not almost.

D3004-660000 "Air Circ"



D3004/660000 Air Circ Axis Curves



D3004/660000 Air Circ NF 4"



D3004/660000 Air Circ Distortion at 92 dB output








Strengths and weaknesses seem to be as individual and characteristic as their designers and companies. But two possible winners do emerge- the 27TBFCG for those of a sensible inclination or limited means; the D3004/662001 for those with deep pockets and demanding tastes.

[savage25xtreme]

Awesome evaluation! I look forward to your mid and midwoofer evaluations! :T

[Jed]

Interested to see higher order distortion plots. I know that is a lot of work, though.

[Rick Craig]

Wait till you see the Be version

[Jed]

Wait till you see the Be version

Yeah... saw that in VC magazine. Some new things from SS on the horizon.

[Dave Bullet]

ET, what has the Emperor commanded you build? Is cost no object or size no object? Will this be a monopole design, omni or some other incarnation from the dark side?

[chrismercurio]

Be from SS?

I haven't had a subscription to Voice Coil since 2002. Do tell...

Will there be matching woofers?

[dlneubec]

I would have liked to see the results from the Peerless HDS tweeter in with this group. It has a lot of performance for the $, IMO. Nice comparison at any rate.

[Evil Twin]

I would have liked to see the results from the Peerless HDS tweeter in with this group. It has a lot of performance for the $, IMO. Nice comparison at any rate.

Yes, I would like to see that comparison, too, but the Imperial Treasury is not what it once was, in these perilous times. Add the new Eton dome tweeter to that list, also. Other SS and Seas models would be interesting, but then no funds would be left for construction or crossovers.

When 2nd and third order harmonics are 60-70 dB down, then the value of high order harmonics should be of neglible concern. Most well made tweeters will exhibit very low values- ones with significant high order levels tend to show issues elsewhere, too. John Krutke's comparisons are illustrative.

[Evil Twin]

Wait till you see the Be version

The Be version may be a mixed blessing- though it's break up mode is commendably high, about 32 kHz based on published data, it exhibits the same issues you'd expect with any non-inverted 1" hard dome tweeter with increasing frequency- that is to say, rather poor off axis behavior at 30 degrees, to say nothing of anything beyond that.




The ultimate proof will be what it does with music in a well voiced system.

[Carl V]

it's an oldy but a goody....Focal 120
Do you have any of those on hand?

Can you get your hands on some newer
Focal inverted domes?

[Evil Twin]

I have a pair of the Focal Tc120tdc - I can probably test them in a week or two- getting the newer Focal parts, since they dropped out of supplying the DIY market, is relatively difficult.

[jeffc52053]

Tweeta tests...

Have you ever tested the Morel CAT378? I'd like to build a HT 5 channel set using the CAT378 and Eminence Alpha 6 for a very efficient system with a wide dynamic range.

[Bear]

Other SS and Seas models would be interesting, but then no funds would be left for construction or crossovers.

A pair of traitorous rebel spies with the code names of "Air Circ" has been in custody elsewhere in the Imperium gathering dust on the outside of their carbonite encasement. Such prisoners can be readily transported to Corruscant for extended testing and evaluation should the Emperor provide the appropriate jump coordinates. Local imperial magistrates only request that the broken bodies of the traitors be returned ultimately to face their local crimes, as well as those against the greater Imperium.

Bill

[---k---]

:rofl:

[jdc0589]

A pair of traitorous rebel spies with the code names of "Air Circ" has been in custody elsewhere in the Imperium gathering dust on the outside of their carbonite encasement. Such prisoners can be readily transported to Corruscant for extended testing and evaluation should the Emperor provide the appropriate jump coordinates. Local imperial magistrates only request that the broken bodies of the traitors be returned ultimately to face their local crimes, as well as those against the greater Imperium.

Bill

Oh dear god, I may have shat myself.

[Evil Twin]

A pair of traitorous rebel spies with the code names of "Air Circ" has been in custody elsewhere in the Imperium gathering dust on the outside of their carbonite encasement. Such prisoners can be readily transported to Corruscant for extended testing and evaluation should the Emperor provide the appropriate jump coordinates. Local imperial magistrates only request that the broken bodies of the traitors be returned ultimately to face their local crimes, as well as those against the greater Imperium.

Bill

I am sure it would be possible to arrange an adequately coercive interrogation that would not leave any incriminating marks or evidence of ill treatment to provoke the conscience of rebel sympathizers.

Expect a Holonet Relay transmission later this evening with the relevant coordinates.

[Evil Twin]

Have you ever tested the Morel CAT378? I'd like to build a HT 5 channel set using the CAT378 and Eminence Alpha 6 for a very efficient system with a wide dynamic range.

That CAT378 has never been investigated at this research facility. In the interests of promoting Imperial good will, I do feel compelled to point out that a Focal Td120tdc will provide comparable efficiency (93 dB) through an advanced magnetic structure, rather than a small horn with limited bandwidth and questionable design parameters for the motor- or rather, shall we say, old fashioned design parameters.

At an even lower price than the Focal, the Peerless 810921 hits the 93 dB mark, and with known low distortion- one might suspect it would be an interesting mate up with a waveguide.

[Bear]

I am sure it would be possible to arrange an adequately coercive interrogation that would not leave any incriminating marks or evidence of ill treatment to provoke the conscience of rebel sympathizers.

Expect a Holonet Relay transmission later this evening with the relevant coordinates.

Jump coordinates received, and the prisoners will be placed on the first available transport to Corruscant. To prevent any rebel spies from attempting to free the traitorous scum, local officials here in the Rim will use a decoy shuttle with the markings of a simple Federation Expediters cargo vessel. Our agents have also been holding a pair of 18cm Wookiees from the "Revelator" tribe for local crimes, though the magistrate has been too busy to bother sentencing them to permanent incarceration. Given the "Revelator" Wookiees' reputation as formidable fighters, they may be of interest to the Emperor for his current operations, though a humble servant would never dare press the Emperor or his apprentice for premature disclosure of any information.

Humbly submitted,
Your Loyal Ursine Subject

[Evil Twin]

Your diligent efforts serve the Imperial research labs well, and reflect admirably on your insight and loyalty. Such service will not go unnoticed....
Without question, a suitable quid pro quo with regards to information exchange and development strategies can be arranged. Another Holonet transmission will be arranged in due time. It is most pleasing to note that this forum has loyal Imperial subjects like you and Craig particpating, that have the appropriate appreciation for the power of the Dark Side. :twisted:

[wkhanna]

:roflmao:

It is a true gift from the Emperor to once again have frequent and regular transmissions from our Dark Lord restored!

[Evil Twin]

You are most fortunate that these gifts will continue, with frequent data updates via the Holonet scheduled for this week; the Emperor's request, rather, that is, demand, is that the tweeter testing be completed, the midrange drivers also posted, and most of the planned midwoofer candidates for his new system tested.

I am certain that not meeting this schedule would have most unpleasant repercussions...

[Evil Twin]

An appropriate midwoofer driver?

Now, this is the kind of product which exhibits the engineering workmanship and aesthetic suitable to being incorporated in an Imperial Advanced Research and Development Lab project...




One would hardly be surprised to find these in the sound system of a Tie Fighter or Bomber....

And one will be in the lab for testing this week. The ARDL division has already done a computational analysis of the engineering parameters for the new project, and it appears promising... most promising.

[Dennis H]

Master, it has come to my attention that a pretender is styling himself as the "Dark Lord" amongst the fringes of the galaxy controlled by the rebel scum. I trust that you shall not allow this insult to pass unanswered.

Image not available

[brucemck2]

On the outer fringes of Salk these non-cylindrical devices were spotted performing duties in neither the lower nor upper regions, and have been reported to being instrumental in the teleportation of dead vocalists:

http://www.fal.gr.jp/catalog/english/

[Evil Twin]

On the outer fringes of Salk these non-cylindrical devices were spotted performing duties in neither the lower nor upper regions, and have been reported to being instrumental in the teleportation of dead vocalists:

http://www.fal.gr.jp/catalog/english/

Ah, yes, AMT drivers.... that brings back memories of a time long ago in a galaxy which seems far, far away.

Yes, by all means let's eliminate the "impurity of sound" caused by conical drivers instead of flat planes...

Wait a minute... don't I recall KEF doing that about 30 years ago? And Panasonic about 20 years ago? Well, it must be time for that chestnut to be trotted out again.

Interestingly, they have managed to achieve a sensitivity of 95 dB for one watt. Most curious that the laws of physics must be different in their land, and 8 watts from a vacuum tube amplifier are equal to 50 watts from a solid state amplifier.

Small Planar woofer dynamic drivers do not concern me. I have my orders from the Emperor, I have no choice but to do my master's bidding.

[Hank]

I have my orders from the Emperor, I have no choice but to do my master's bidding.

:sos: We have GOT to find a woman for Jon. Methinks that when he looks in the bathroom mirror in the morning, he SEES Darth. :nonod:
A little diversion from staring at response graphs may do the boy some good.

[TacoD]

Those square FAL transducers are not that great. I heard those once at a local hifi shop and it was just sounding like a small driver, i.e., limited dynamics and with a smallish stereo image.

[Hank]

Now, this is the kind of product which exhibits the engineering workmanship and aesthetic suitable to being incorporated in an Imperial Advanced Research and Development Lab project...

Might one assume those beauties have a smidgen of XMax? :W

[Kevin Haskins]

An appropriate midwoofer driver?

Now, this is the kind of product which exhibits the engineering workmanship and aesthetic suitable to being incorporated in an Imperial Advanced Research and Development Lab project...




One would hardly be surprised to find these in the sound system of a Tie Fighter or Bomber....

And one will be in the lab for testing this week. The ARDL division has already done a computational analysis of the engineering parameters for the new project, and it appears promising... most promising.

That is a fine looking motor.

[Evil Twin]

Might one assume those beauties have a smidgen of XMax? :W

As always, you have a flair for elegant understatement and humor, cleverly concealing the steel trap mind underneath.

The ability to provide long voice coil excursion is insignificant unless it is combined with a balanced overall design and performance parameters.

This one looks impressive, most impressive. But the final assessment must await testing in our laboratories. Only if it completes that phase successfully, will the Emperor be inclined to release it to listening evaluations in the target system configuration. He is determined to calculate every possible parameter and variation of the new system configuration to assure that it manifests the full power of the Force and shows the pretender the error of his ways.

[Bent]

Is the new driver from the constellation of "Kepler" going to be available in Solo form?

[Finleyville]

I am glad to see my favorite tweet, Seas 27TBFC/G, hold up so well against its peers and higher priced siblings. I have never heard the Scanspeak so I cannot comment there. I am surprised that the while the Dayton RS28 looks on paper to be similar in performance that I hear more upper end detail with the Seas.

I am looking forward to this project especially if it turns out to be a all metal, multi-driver setup. Maybe something bigger to perfectly compliment my Zaph L18's! :T (Man, I just love those monitors...)

[Evil Twin]

The Emperor has dictated that this will be completed in two configurations, one sparing little expense and with a driver and crossover budget that may make a successful professional Sabaac player blanch, the other priced for more modest means. The Seas 27TBFC/G is in the front position for the latter combination, and a there is a very promising metal midrange which will likely accompany it- IF it performs as expected. The rest is yet to be determined, and of course, based on sufficient performance equivalence, there may be more than one alternative in some cases.

[Evil Twin]

That is a fine looking motor.

Indeed it is. It appears to be an exceptional driver design in many regards, considering frame rear masking, spider design, motor, and more.

Clearly it is at a different technological plateau than components normally available in this region of the galaxy. Now let us see if it possible to integrate this into a system configuration that becomes more than the sum of it's components.

[Kevin Haskins]

Indeed it is. It appears to be an exceptional driver design in many regards, considering frame rear masking, spider design, motor, and more.

Clearly it is at a different technological plateau than components normally available in this region of the galaxy. Now let us see if it possible to integrate this into a system configuration that becomes more than the sum of it's components.

I've been itching to buy a pair of the Seas DXT tweets and do a quick design in place of the Peerless. The midwoofer requires a low crossover point and I'm betting that the Seas can handle 1.5K with the right crossover.

Ok.... I've talked myself into it.

[Paul Ebert]

I've had my eye on the Kepler mid for quite some time for an OB design, though with two in college in the fall it's probably out of reach. None the less, I'll be very curious to see how it performs.

For what it's worth (not much, since I haven't compared them to anything), I love the DXTs in my Trilliums. In that design they are not crossed low, but I bet they could be.

[JonMarsh]

I've never played with the DXT's myself, had barely heard of them, recalling just one announcement by Seas a while back when they were introduced. That's how little time I've had for this since Autumn 2007! :W

MarkK and others have done some distortion testing, and also determined that using the 27TBFCG magnetic assembly with the DXT helps lower distortion- pulling the original 27TBFC VC assembly off slowly, most of the FF will be left in the gap.

Mark's recommended minimum crossover frequency based on testing is ~1500 Hz.

[---k---]

MarkK and others have done some distortion testing, and also determined that using the 27TBFCG magnetic assembly with the DXT helps lower distortion- pulling the original 27TBFC VC assembly off slowly, most of the FF will be left in the gap.

I would also point to Jed's testing of that combo and his Tombstone design which used it. Good stuff.

[Jed]

I've never played with the DXT's myself, had barely heard of them, recalling just one announcement by Seas a while back when they were introduced. That's how little time I've had for this since Autumn 2007! :W

MarkK and others have done some distortion testing, and also determined that using the 27TBFCG magnetic assembly with the DXT helps lower distortion- pulling the original 27TBFC VC assembly off slowly, most of the FF will be left in the gap.

Mark's recommended minimum crossover frequency based on testing is ~1500 Hz.

What you are referring to above is the test I did.

The tweeter is the hybrid H1212 waveguide loaded DXT tweeter I tested awhile back.

Image not available

I took the 2 best profiles from above and merged them, so I can easily compare the differences. Below you can see the stock 27tbfc-g tweeter and the DXT dome unit on a 27tbfc-g motor. I labeled each set of harmonic distortion for the DXT dome unit on a 27tbfc-g motor as "DXT". The DXT hybrid outperforms the stock 27tbfc-g tweeter in all non-linear distortion tests except D2. With the benefits of a waveguide it will be even better.

Image not available

More distortion tests in this group of Seas tweeters can be found on my website.

[Evil Twin]

I thought the point of the DXT was that is IS a waveguide tweeter, with the modified frequency response (requiring crossover shaping), and the pattern control (at least down to about 4-5 kHz- below that it's like the MCM waveguide used with the 27TDFC, which I've tried out- the output curves meld at about 3.3 kHz, no pattern control there or below). Or are you referring to using that motor with another dome assembly and the MCM waveguide?

What bothers me about this approach, in a practical speaker, is what midrange and/or midwoofer will you mate it up with that will have the same pattern control in it's operating range, so that the power response is consistent? I don't see an answer to that for a monopole speaker, only a dipole.

[Kevin Haskins]

Yea... the camel hump off-axis problem is something your not going to solve in a 2-way device unless you get significantly bigger, Earl sized waveguides.

You can improve the situation with a 3-way but you don't reach perfection way off axis. I'm not sure how much it matters way up high. Most rooms are highly absorptive at the really high frequencies so your late high-frequency reflections are highly attenuated to start with. I'd be happy to have very good +/- 30deg window and smooth past that without the camel hump you get in most traditional 2-ways far off-axis.

Here is a typical 2-way. This was highly reviewed by the audio press. :Z

Image not available

Here is another 2-way although it is clear they have some pattern control up high.

Image not available

Here is a 3-way without top octave pattern control but good design passing off driver to driver.

Image not available

Combine graph Forum & Blogs and you have pretty good control from 700Hz on up. That is good enough for government work.

[Evil Twin]

This is the correct path...

I believe you have the right idea... this is why even in the 70's I was investigating baffle designs with facets to reduce the launch baffle size progressively so that the drivers are operating closer to 4 pi space; if a solid angle of +/- 30 degrees must exhibit consistent performance and only minimal drop off at 45 degrees, then there is very interesting potential in a design.

Paying attention only to a primary design axis on axis is barely a start.

In this project, one step will be an analysis of the chosen drivers for off axis performance, but this must be followed with an evaluation on the chosen baffle design as a guide in selecting the three way center frequency and overall crossover points.

[jkrueger]

Let me get this straight

Sorry your highness. I am not well versed in appropriate Starwars "ese". I am beginning to suspect that this is a very interesting continuation or slight evolution of the old Mt12a thread....Yes?

[Kevin Haskins]

I've had my eye on the Kepler mid for quite some time for an OB design, though with two in college in the fall it's probably out of reach. None the less, I'll be very curious to see how it performs.

For what it's worth (not much, since I haven't compared them to anything), I love the DXTs in my Trilliums. In that design they are not crossed low, but I bet they could be.

Wiggins and I did a quick & dirty design with a pair in an MTM on a baffle. We used LSPCad to digitally emulate the crossover. They work fine but I'd high-pass them at around 80Hz or even higher. It depends on what your output needs are because you quickly run out of excursion down low on the baffle and unlike some of those high-efficiency OB speakers, the suspension doesn't limit them and they will go until you hear the clack-clack-clack of the spider limiting.

I guess that is suspension limiting but it is out past 10mm so it is an entirely different thing than the cone moving a mm or two and not having the motor to force the suspension into lock-up mode. It sounds pretty nasty so you definitely need an electrical filter.