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HDT_DFR-8_Alternate Tuning Images (Read 28472 times)
RFZ_Quest
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HDT_DFR-8_Alternate Tuning Images
10/31/07 at 04:44:46
 
The following images are of my current project, assembling a set of single driver HDT cabinets with the recommended alternate tuning procedures implemented to match the performance characteristics of the modified DFR-8 / Fostex driver conversion. These photographs show extensive detail as to what is required for optimal performance with these drivers.

There is a blend of two different types of acoustic foam used in this build. This involves a combination of convoluted acoustic foam, and a higher performance rated multi-layer composition foam for controlling vibration and standing waves inside the cabinet.

To further reduce vibration within the inner walls of each chamber, all areas NOT covered with foam have been coated with an asphalt based sound deadener used to undercoat automobiles for noise reduction. Extreme care was established by very careful masking of each panel to insure that none of the coating was applied to any joint surface where glue is intended for assembly. The foam sections are glued to the bare MDF surface which was also masked off prior to coating with the visceolastic application. The foam is attached after the coating is applied, with only the black sections that are visible actually coated.

A very critical modification NOT shown on the blueprints, are that of the hardwood cross brace stiffeners required for EACH chamber to nullify any cabinet flexing between the chambers. This requires only one brace per chamber as shown in the photographs. They are cut to fit from hardwood dowling and beveled to fit snugly within the chamber V-sections.

These cabinets as shown have not been glued together as of yet. What is shown is a DRY-fitting to insure that everything matches-up correctly. The perimeter foam sections 'compress' together perfectly when the panels are clamped together. The compression forces the foam sections to merge together very snugly which expands tightly into all of the gaps for complete encapsulation where it needs to be.





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RFZ_Quest
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Re: HDT_DFR-8_Alternate Tuning Images
Reply #1 - 10/31/07 at 04:47:16
 



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RFZ_Quest
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Re: HDT_DFR-8_Alternate Tuning Images
Reply #2 - 10/31/07 at 04:49:32
 





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RFZ_Quest
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Re: HDT_DFR-8_Alternate Tuning Images
Reply #3 - 10/31/07 at 04:52:03
 




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RFZ_Quest
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Re: HDT_DFR-8_Alternate Tuning Images
Reply #4 - 10/31/07 at 04:54:49
 





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RFZ_Quest
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Re: HDT_DFR-8_Alternate Tuning Images
Reply #5 - 10/31/07 at 04:58:02
 





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RFZ_Quest
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Re: HDT_DFR-8_Alternate Tuning Images
Reply #6 - 10/31/07 at 05:01:39
 





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RFZ_Quest
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Re: HDT_DFR-8_Alternate Tuning Images
Reply #7 - 10/31/07 at 05:11:59
 






This view shows the bottom averaging chamber.

The three port tube openings can be seen entering from all three chambers.

This all combines and routes into the fourth chamber which is the
'transmission-line'.

That chamber runs along the back of the cabinet, exiting through the
top plate of the speaker.
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RFZ_Quest
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Re: HDT_DFR-8_Alternate Tuning Images
Reply #8 - 10/31/07 at 05:21:27
 




This should help clarify some of the questions asked about the alternate tuning method used for the
single driver HDT using the modified DFR-8 driver.


If a picture is worth a thousand words, then this should
speak volumes about how everything is put into place.


More assembly photo's will be shown as the project progresses.
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erimille
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Re: HDT_DFR-8_Alternate Tuning Images
Reply #9 - 10/31/07 at 20:00:29
 
RFZ_Quest wrote on 10/31/07 at 05:21:27:
[size=12]If a picture is worth a thousand words, then this should
speak volumes about how everything is put into place.


Absolutely *brilliant*! You're way ahead of me in terms of construction. Thanks for recording your journey and sharing. I'd be interested to hear how these sound to other HDTs you've listened to (as well as the Radials ;-) )

--e
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RFZ_Quest
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Re: HDT_DFR-8_Alternate Tuning Images
Reply #10 - 11/01/07 at 02:31:15
 
Thanks Eric.

I should have these operational by this Sunday (if all goes well).

The nice part of it is that the DFR-8 drivers will be pulled out of
the NFX models for a new home within the HDT's.  This means that
'break-in' of the drivers is not so much of an issue due to them
already having a significant amount of hours on them (somewhere
around 150-200 hours while in the NFX models).

These are primarily for testing and analysis as the primary purpose,
so external covering will be put on hold  until later. I have not
decided on whether to go the veneer route or prepare them for
automotive paint. These would look great with a metalic/pearl
base coat with several layers of clear coat. That is alot of work with
precise attention to detail for preparing a surface good enough for
that type of finish, without noticable flaws in direct light. I have
prepped and painted auto's before, so this would not be too difficult for me.

I have also devised a much better 'cloth-based' driver covering system
in my mind that will be easy to construct and blend with the speaker
lines very well. This is a one piece system that blankets the top section
(under the dispersion plate), and extends downward over the two passives
and the driver. This would be non-obtrusive or cause any concern with
diffraction. Due to the design, this would simply conform snugly down
and around the top of the speaker with nothing but gravity holding it in place.
The contact area would be covered with felt, thin cork sheet, or something
similar to prevent vibration.

I have even considered going to the extent of embedding sections of
brushed-aluminum panels flush within the surface areas, below the
passives, and the main driver. The aluminum plates could be inscribed
with great detail using a CNC machine.

Anyway, the primary objective is analysis for this particular HDT model
upgrade. That means after I have had sufficient listening time, a review
by comparison to what I've experienced with the other models will
be in the works.

I believe that if I was to predict the sound of these HDT's before hearing
them, I would speculate in my mind, a sound which would be similar to a
'hybrid' combination of the early radial designs, and that of the top end
Kadence design which I am using now. If these speakers capture the
presence, speed, and finesse which I've come to know within the original
radial designs, and that of the Fostex based Kadence design, I will be
very pleased to say the least.

Here are a few more detailed images showing a breakdown
of the assembly process.






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RFZ_Quest
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Re: HDT_DFR-8_Alternate Tuning Images
Reply #11 - 11/01/07 at 02:34:09
 




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RFZ_Quest
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Posts: 296
Re: HDT_DFR-8_Alternate Tuning Images
Reply #12 - 11/01/07 at 02:38:55
 





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RFZ_Quest
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Posts: 296
Re: HDT_DFR-8_Alternate Tuning Images
Reply #13 - 11/04/07 at 15:52:33
 




DFR-8 Driver ready for installation.



Terminal leads routed directly thru X-Brace. Holes are drilled to pass wires thru section into back chamber. It is important that these holes are drilled to pass the wires tightly! Once the wires are in position, the entry & exit points MUST be sealed off air tight to prevent unwanted interaction between the front chamber and the transmission-line. This can be done by coating the section of wire with some sticky putty, hot glue, etc., that resides within the X-brace section to seal the wire feeds effectively. The next step would be to coat the entry and exit points with hot glue, epoxy, etc.









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« Last Edit: 11/04/07 at 15:57:47 by RFZ_Quest »  
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RFZ_Quest
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Re: HDT_DFR-8_Alternate Tuning Images
Reply #14 - 11/04/07 at 16:02:50
 





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