DynaVox LY302F  with  Wharfedale W15/FS

 

This project yielded an interesting result.  The original intent was to use a vertical line array of four DynaVox Y302F units in conjunction with a Wharfedale W15FS in a corner cabinet.  The idea was to use an existing woofer in lieu of building another, the space for which was not available.  It was also intended to find out if the midrange and treble sound of the Wharfedales could be duplicated.   These DynaVox 4 inch units have a frequency response that extends well to 20khz, thus eliminating the use of a tweeter.  The Wharfedale W15 would be switched from the  HS/CR3-2 crossover to another crossover and the input to the HS/CR3-2 would also be switched between the two crossovers.  However, complications arose later that were enough to abandon that project and instead of the W15, the 8 HiVi 4" woofers under the sofa would be used instead.  These were also used with another wall mounted line array comprised of eight BMR12W units, a 1.5 inch square flat diaphragm speaker.  These worked very well but didn't sound like the Wharfedales and I found an excuse for some new toys and another project.

The aforementioned complication was that there was later added a switching system to switch the corner Wharfdales from the Adcom to the Scott 99B.  This is shown in figures 4 and 5.

Anyway, the DynaVox units worked better than expected.  They do reproduce the treble louder but that's due to the speakers' being aimed forward; the Wharfedales aim upward.  However, a comparison was made with the Wharfedales forward aimed.  That comparison is shown later on this page.

An interesting phenomenon was noticed.  If not knowing which pair is playing, it's difficult to make that determination when facing the painting.  However, if the listener turns towards either Wharfedale, that determination becomes easy.  This is assumed to be what appears to be the wide radiation pattern of the DynaVox units.  The Wharfedales, being in the corner have the walls reflecting their radiation pattern.  This is independent of the aiming of the Wharfedales' mid-ranges and tweeters.  (NOTE: This little determination was made while writing this paper.  I had to retrieve my coffee cup left in the living room on the table and noticed that I couldn't tell which pair was playing.  When I decided to walk towards the left Wharfedale, I had to turn to my left and then it became apparent.  Walking to the left corner verified that.  This was repeated several times with the same results despite that during subsequent trials, I knew which was playing and it was still difficult to know by listening.)

 

 

PHOTO 1

The following two photos just show the upper section of the Wharfedales' facing forward.

The painting is oil on canvas and actual size to the original.  It's described HERE

The frame is not paint; it's 24 carat gold leaf

 

 

 

PHOTO 2

 

 

 

 

 

 

FIGURE 1

RED=Wharfedale-upward; GREEN=Wharfedale-forward; VIO=DynaVox; BLUE=Wharf-THD; GREY=Dyna-THD

Click on the figure for a larger view

The Wharfedale firing upward has a louder response above 6khz.  This may be due to the wide dispersion of the vertical array.  The Wharfedale firing forward has the strongest response above 6khz due to the beaming effect of cone tweeters.  The DynaVox units also have a whizzer cone for high frequency dispersion.

What was surprising is the very close identities of THD above 125hz.  At its worst, above 2khz, the 25dB difference equates to about 7% THD.  At the lowest, around 200hz, it drops to about 3%. While it may seem very high, we become accustomed to THD as all speakers have it to some degree.  However, in both these systems, the 2nd harmonic is predominant below about 300hz which may account for the liked sound of these Wharfedales.  The ear and brain seem to favour even numbered harmonics. It's the harmonics that differentiate the sound of different violins, acoustic guitars, even electric guitars although a lot of other distortions can be added to electric guitars as well as any other microphoned and electronically amplified instrument.  A Yamaha piano, a Steinway, a Bosendorfer and a Fazioli all sound different due to harmonics.

The SPL here is between 75dB and 80dB due to the measurement not being made to equate to 1w1m which is about 90dB, a little loud for a sweep although that would have required only about 5 watts at the 12 ft distance.  The inverse halving law does not apply in a reverberant field.  In open space (2 pi steradian, a hemisphere) it would require16 watts.

 

 

 

FIGURE 2

Let me explain the 4 confusing traces here.  Between around 4khz and 10khz, one can easily see 4 traces.  From top to bottom, they are ORANGE, GREEN, RED and GREY.  They correspond to the the designations in the handwritten image below.  The numbers to the left of the cabinet drawing are the positions at which the mic was pointing.  All traces were made at 1w1m.  It appears that the #3 curve is the best as that was done with the mic pointing midway, between #2 and #3.  They all correspond well to the manufacturer's data sheet found HERE

All 4 speakers were operating during this run

Note the rise at 20khz which doesn't appear in the VIOLET trace of figure 1 above.  This was puzzling and was solved in figure 3 below.

 

 

 

 

FIGURE 3

Single unit 85dB at 12 feet

Fortunately, I bought 10 of these fellas so I was able to run another response curve of one speaker in the living room under the same conditions as that run in figure 1 above. 

The rise at 20khz is again there, somewhat attenuated probably due to the effect of the soft velvet sofa, the blue chair and the heavy drapes.  This room is slightly more treated than the music room in which the traces of figure 2 above were run.  At any rate, it appears that the disappearance of the bump is due to the vertical array of 4 drivers.

 

 

 

These are the schematics intended for the switching of the W15 and the input from the Adcom from the Wharfedale crossover to another crossover.  Fig. 4 shows the original intent until it was realised that there was that little blue box (photo 3 below) that also switches the Wharfedales between the Adcom and the Scott.  So, the schematic on the right was drawn.  This added another 4 pole double throw switch, both having to be switched simultaneously.
FIGURE 4

 

 

FIGURE 5

 

 

 

 

PHOTO 3

The Little Blue Box

There's another barrier strip on the rear panel.

PHOTO 4

A bar was made from a wood dowel that allowed both switches to be toggled simultaneously.  A couple of 4 pole double throw relays was considered but that complicated things even more.  The whole idea was abandoned due to its becoming resemblant to the cockpit of a 747

     

 

 

 

PHOTO 5

Here's the first baffle design.  The theory to use open back failed dismally.  The response was all over the place with peaks and dips of +/- 15dB.  A little thought inspired the idea that the back of the speakers was too close to the wall, about 4 inches.  The reflection path of 8 inches is a wavelength at 1700hz and a time delay of about 0.0006 second, roughly half a millisecond.  That's where most of the acoustical nightmare started.

So, it was back to the drawing board and that produced the cabinets seen in photos 1 and 2.

The array is second order high pass filtered at about 300hz.

 

PHOTO 6

These little fellas are the woofers.  There's two cabinets under the sofa housing 4 units. They are HiVi B4N units, inverted copper dome or copper plated inverted aluminum dome.  They do very well to 45hz with a little bass boost.  At levels approaching 90dB, the bass has to be brought back down to about high noon after which they'll hold up well to maniacal 100dB+ levels.  This was done twice; once for myself and once for a friend.  Their Xmax is 3.2mm.

 

 

 

 

 

PHOTO 7

A view of the dining room.  The speakers in the rear are described briefly in photo 5 on this page and in detail on this other page

 

 

PHOTO 8

This photo shows the previous vertical line arrays.  The speakers contained therein are available HERE

They sounded great but as mentioned earlier, I needed another project.

The blue speakers are SONY car speakers of which I bought 20 at Parts Express for less than $5 each.

They are described HERE

The tweeters attached to the sides are BESTON and can be seen HERE

 

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