BMS 4592ND-MID versus the B&C DCM50 Update

[greg928gts]

Hey, I've got a novel idea. Let's actually listen to them before we comment on them.

I trust my ears.

Edit - New information added

www.voltiaudio.com/midrangedrivers.shtml

Greg

[cjgeraci]

I dunno. Are you sure that your ears were accurate given the martinis? [8-|][:S]

[]

[Mike Lindsey]

Is there a thread that this post was in reference to? If so I would like to read it.

[cjgeraci]

http://community.klipsch.com/forums/t/131776.aspx

Mike, the above following thread, called "Trachorns in the House," started off discussing Al's one-inch throat Trachorns but then got sidetracked into a discussion regarding the two-inch drivers Greg references. I believe Al also again references BMS in his latest thread about the B&C DCM50.

Carl.

[Deang]

Greg -- the BMS driver is effectively out of gas by 6kHz. Combined with the 12dB/octave filter section of the ALK, it's pretty much going into a nosedive. The B&C has more bandwidth, and because of this -- it's rolling off more gradually as it transitions to the tweeter. This in part might explain some of why you're hearing what you're hearing.

I'm somewhat critical of how you performed the test: Level matching by ear don't get it, and besides, it's very unlikely that you'd be able to do it using just the autoformer because of the difference in sensitivity between the drivers. I mean, tap so-and-so gives you one thing with one driver, and then when you move to the other driver you do tap so-and-so -- but they aren't going to be matched to within 1dB.

No matter. The reality is that some will simply prefer the sound of one over the other. Nothing new there!

[Deang]

Something I'm having trouble understanding is the fixation with the 300Hz crossover point.

The V-trac has a Fc of 260Hz. The K-400 has a Fc of 230Hz.

The BMS goes down to 300Hz. The Atlas PD-5VH goes down to 250Hz.

So why didn't PWK cross at 300Hz?

When Klipsch revamped the Heritage Series, they went with steeper slopes on the filters -- yet the Klipschorn went from 400 to 450.

pd5vh_specsheet.pdf

pd5vh_specsheet.pdf

[deafbykhorns]

How about these guys, check out http://classicaudioloudspeakers.com/cgi-bin/index.pl?fs=2&upper=27&content=28 drivers if you are looking for esoteric. I was blown away by these at the Axpona show here in Jacksonville. These use DC Coil and are lightning fast, they also reproduce to 14KHZ. They have the speed of a electrostatic and the classic horn sound all in one. This was by far my favorite speaker of the show. Only two other systems I heard were better (in my opinion) but at an additional cost of 50K.

BTW: I think Dean said it well. And both of these drivers should be in seperate speaker cabinets with a well designed crossover and voicing tests before an A/B test is performed. You just can't expect to throw in a driver and expect it to work out of the box.

I'm somewhat critical of how you performed the test: Level matching
by ear don't get it, and besides, it's very unlikely that you'd be able
to do it using just the autoformer because of the difference in
sensitivity between the drivers. I mean, tap so-and-so gives you one
thing with one driver, and then when you move to the other driver you
do tap so-and-so -- but they aren't going to be matched to within 1dB.

No matter. The reality is that some will simply prefer the sound of one over the other. Nothing new there!

[Audible Nectar]

My local tube tech has been telling me to check out field coil speakers for a while now. "If you're a horn guy, you MUST hear them", he says. I am quite frankly afraid to given his descriptions, as I have a great deal of satisfaction in my current setups (which have been compared to some much more expensive stuff, yet my satisfaction of my setups haven't been ruined by that experience). I'm told that field coils might well be capable of that, and the only thing that would keep me seated was the price.

They are definitely a curiosity, to be sure.

[Fjd]

I could be wrong, but I thought that the introduction of Alnico V as a magnetic material (developed during WWII?) was the main reason that field-coil speakers were abandoned? I’m curious if the sonic advantages of the speakers referenced above come from the use of beryllium diaphragms or the field coil magnet structure? Interesting how things come full circle.

With so many choices, how does a person sift through all the claims for the superiority of ferrites vs. neo vs. alnico vs. field-coil arrangements? I assume that all of these methods of making the magnetic flux allow very different approaches to the design of the motor structure itself and could have an impact on the driver characteristics........ I believe that Dr. Floyd Toole did some work toward defining the qualities that characterize good sound and then tying those qualities to objective, measurable factors (a scientific approach to listening tests?). Seems like ultimately the measurements have to work in a planned project, then some type of A-B testing (without knowledge of which one is being listened to - best case) with recorded material (or memory of the live performance?) a person is very familiar with to know what is correct (or "best") in that specific situation.

[Marvel]

I'm somewhat critical of how you performed the test: Level matching by ear don't get it, and besides, it's very unlikely that you'd be able to do it using just the autoformer because of the difference in sensitivity between the drivers. I mean, tap so-and-so gives you one thing with one driver, and then when you move to the other driver you do tap so-and-so -- but they aren't going to be matched to within 1dB.

I think the larger problem with the setup is connecting the B&C driver to the crossover that has no tweeter or woofer attached. (Unless I misunderstand how they were connected) Won't that throw off the way the crossover functions?

[Deang]

I believe he did a test of just listening to the drivers without the other sections of the speaker playing. I assumed he terminated the unused portions of the filters with resistors. If not, then yes, that would certainly create some problems.

[Guest David H]

I believe he did a test of just listening to the drivers without the other sections of the speaker playing. I assumed he terminated the unused portions of the filters with resistors. If not, then yes, that would certainly create some problems.

Yes, resistors teminating the woofer and tweeter are ideal for single driver test, and I am fairly certain that is the case. As for A/B comparison, I am all for a test based on listening, however I would like to see some graphs as well. The artilce does say more to come.

[Guest David H]

Seems to me using an additional autoformer and a switch would be a fairly quick and accurate way of performing an sound based A/B test.

Any thoughts?

[deafbykhorns]

I could be wrong, but I thought that the introduction of Alnico V as a magnetic material (developed during WWII?) was the main reason that field-coil speakers were abandoned? I’m curious if the sonic advantages of the speakers referenced above come from the use of beryllium diaphragms or the field coil magnet structure? Interesting how things come full circle.

These http://www.truextent.com/ are the guys making the beryllium diaphragms and may have one to fit some drivers mentioned in this forum. We need a developer interested in this product to get the ball rolling. I'm guessing they already have several diaphrams that would fit the JBL line. Don't know if what I was hearing the other day was due to the field coil assembly or this diaphram. Its worth a try, read the following from website.

Why Beryllium?

There is no doubt that of all the commercially-available materials
today, beryllium domes yield the finest sounding compression drivers
with all of the mechanical power handling capability of titanium or
aluminum. Beryllium has the highest stiffness to density ratio of all
commercial driver dome materials. This allows the diaphragm to have a
low overall mass, which greatly improves the responsiveness and still
remain rigid over a wide frequency range, eliminating the “breakup”
associated with the mechanical deformation of traditional domes at
their resonate frequencies. Another critical advantage of beryllium in
diaphragm applications is that it performs up until failure mode with a
minimum of sound quality degradation.

Why Truextent™?

Our beryllium diaphragm assemblies blend the finest materials and design methodology to yield true clarity of sound.

• Aluminum
  Wire Voice Coils. In addition to the beryllium dome, the design further
  reduces overall mass by using edge wound voice coils of pure aluminum
  wire. These voice coils have less mass than copper-clad wire (which
  yields better top-end frequency response) and have superior heat
  transfer capability over copper-clad wire (which improves the
  power-handling capability). Our proprietary aluminum soldering process
  ensures superior reliability.
• Polymer Surround. To
  further extend the frequency response and improve the lifespan of the
  diaphragm, these assemblies incorporate a polymer surround. Our
  proprietary adhesive joining process results in improved uniformity of
  diaphragm-to-diaphragm performance and a uniform application of
  adhesive, resulting in minimal mechanical distortion of the dome (and
  sound waves).
• The Right Design. Our design uses a
  beryllium dome formed from extremely thin sheet material for superior
  performance and does not shatter during failure mode.
• The
  Right Fit. Our standard off-the-shelf diaphragm assemblies have been
  designed to drop right into the majority of existing compression driver
  motor geometries. We have the engineering and manufacturing capability
  to supply full-custom versions for OEMs.

Why Clarity of Sound?

The
sound reinforcement market DEMANDS compression drivers that can
dissipate a lot of power and produce high Sound Pressure Levels (SPLs).
The Truextent brand of compression driver diaphragm assemblies can
deliver that, and much, much more. Unlike titanium diaphragm
assemblies, whose breakup mode occurs around 4kHz where the ear is most
sensitive, our beryllium diaphragm assemblies have been designed with a
breakup mode shifted to above 15kHz, which is higher than all the
fundamental frequencies by an octave. The associated breakup harmonics
fall well above the range of human hearing.

The beryllium used
in the Truextent design is thinner compared to other titanium or
aluminum drivers which further increases detail. By faithfully
reproducing the input signal, the NEED for high SPLs actually goes
down, since the system no longer needs to compensate for missing
frequency bands by overdriving. Vocals and instrumental sounds can be
clearly heard by the audience at an overall lower SPL with the same
perceived “volume”, resulting in a more pleasing audience experience.

[Marvel]

Seems to me using an additional autoformer and a switch would be a fairly quick and accurate way of performing an sound based A/B test.

Any thoughts?

Looks like a great idea to me, with no drawbacks.

Bruce

[deafbykhorns]

Talk about pricey, double the cost of a BMS.

http://www.audiogon.com/cgi-bin/cls.pl?spkrmoni&1271512961&/Beryllium-Truextent-Diaphragm-

[greg928gts]

Revamped my testing procedure and it did change my impressions.

www.voltiaudio.com/midrangedrivers.shtml

Greg

BTW, from what I can tell, my testing before with the passive networks was exactly as Gothover showed in his diagram. Still wasn't as good as with the Behringer/T-amp setup.

[Guest David H]

Greg, I am not surprised both drivers sound good, nor am I surprised about your SPL findings. Simply put a lower impedence driver with comparable spl levels will play louder than a higher impedence version at the same input level.

The efficiency of a driver is the output divided by the input.

That said, at one watt the BMS is generating 118 db and is a 16 ohm driver.

Now without modifying the input level to the B/C driver with the same input level is demanding 2X power from the amplifier

so the B/c is operating at 2 watts "per say" thus giving you an output of 108+3db =111db the difference being 7db.

Advertised spec being off do not surprise me at all.

Any or all of this information may be incorrect, but this is how I understand it.

Dave Harris, what I don't know is alot...

[Bacek]

Listening only to midrange drivers does not give complete view. Driver needs to integrate with rest of the speaker. Good speaker it is not only sum of its components.

[Nat Denkin]

Greg, I am not surprised both drivers sound good, nor am I surprised about your SPL findings. Simply put a lower impedence driver with comparable spl levels will play louder than a higher impedence version at the same input level.

The efficiency of a driver is the output divided by the input.

That said, at one watt the BMS is generating 118 db and is a 16 ohm driver.

Now without modifying the input level to the B/C driver with the same input level is demanding 2X power from the amplifier

so the B/c is operating at 2 watts "per say" thus giving you an output of 108+3db =111db the difference being 7db.

Advertised spec being off do not surprise me at all.

Any or all of this information may be incorrect, but this is how I understand it.

Dave Harris, what I don't know is alot...

WIth the drivers directly connected to the transformerless amplifier output, negative feedback keeps the voltage of the amplifier output the same whether 4, 8, or 16 ohm loads are connected. Since the delivered electrical power would be V^2/R, doubling the load resistance, halves the input power. Since the maximum voltage is limited by the power supplies, amplifiers generally can deliver more power into lower impedance loads with the limit being determined by the current disspated by the output devices.

In any case, I would expect drivers to be most fairly compared when generating the same acoustic power when driven by amplifers that are not challenged by the load. Apparently, Greg has done this.

nat