Forums - HDT MK I - alternate tuning

Corey

Ex Member

Re: HDT MK I - alternate tuning
Reply #15 - 10/22/05 at 03:48:42

Brad,

After a brief glance at your pics on this thread, it has occured to me that you glued your passives on backwards. The large dome should be facing out and should be visible from a front view. This loads the sound into a better dispersion pattern and further radiates sound to the chair with a better disappearing act. Time to get new passives if you are picky, I think it will make a difference.

Corey

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Corey

Ex Member

Re: HDT MK I - alternate tuning
Reply #16 - 10/22/05 at 04:03:40

Brad,

After looking at the pic in more detail I think I can pin point the problem. The passive was not built correctly. Not a big deal as Decware will promptly ship you out new ones.
On mine the big outside surround faces out, then the smaller one is inverted(like the Fostex driver) and the dome is glued to the smaller inverted surround. To have your dome facing out you would have had to glue the big outside surround in an inverted position.

The smaller surround should have been inverted then the dome would be facing out.

Take care,

Corey

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« Last Edit: 10/22/05 at 04:12:30 by lynch »

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Corey

Ex Member

Re: HDT MK I - alternate tuning
Reply #17 - 10/22/05 at 05:35:22

To install the ports without having to remove the bracing means sticking the port UP, into the top part of the chamber till it clears the bracing then it will fit down inside.

Also when installing the ports, make sure you have the pipes touching the center line on the coupler. One end usually goes in smoother so attach the coupler to the end that is harder to slide on when it is outside the cabinet. This will leave the easier end of the coupler for pushing onto the existing port inside the HDT. You do not want to break that port free or you are screwed!

Corey

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« Last Edit: 10/22/05 at 08:13:57 by lynch »

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Corey

Ex Member

Re: HDT MK I - alternate tuning
Reply #18 - 10/22/05 at 05:40:52

I wouldn't worry about making adjustments to the size of foam for the passive chambers although you could split it up the middle and extend past the bracing wood, nearing the port. It probably would be a good idea to keep the foam 2 inches from the port if you are going to go longer than 12 inches.

The adjustments that could be made will be in the driver chamber. Here the foam could be even 5 1/2 inches wide by 19 7/8. This way it would reach the very top piece of foam cut into a triangle and reach down to cover behind the driver. If you are going to do this it would be a good idea to glue the foam so it doesn't make contact with the driver. The driver and passive holes must be notched out precisely if doing this.

Corey

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« Last Edit: 10/22/05 at 08:19:48 by lynch »

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zinker

Ex Member

Re: HDT MK I - alternate tuning
Reply #19 - 10/24/05 at 01:56:34

Thanks Corey,
So are you saying that the driver chamber should be completly covered on all 3 sides with foam from the top of the chamber to the bottom of the driver, with the driver hole and the scalloped passive holes completly cut away?
Got any pictures of how yours looked?

Wasn't there any dampening material like felt in those areas to begin with?

I tried lifting, dropping, and walking the passive port extensions in place, but, in the passive chambers, my braces must have been either too wide or too low to allow me to get a straight shot onto the tops of the existing ports. No biggee. I unsrcewed the braces an carefully knocked them out with a hammer.I can reinstal them later.

On a side note:
If I can figure out a safe and accurate way to re-route the passive cutouts on the cabinet sides I will mount the new passives with some laser cut rings and screws. The current rabbit cut is only 1/4" wide, but I need closer to 1/2" to accomodate screw holes and tee-nuts. This design would allow the passives to be removable for easier tweeking. Chrome plating the rings would also echo the chrome finish on the phase plugs.

Thanks for your help,
john

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« Last Edit: 10/24/05 at 01:59:05 by zinker »

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Hrappur

Ex Member

Re: HDT MK I - alternate tuning
Reply #20 - 10/24/05 at 15:43:31

[quote author=zinker link=1123604173/15#19 date=1130115394]

On a side note:
If I can figure out a safe and accurate way to re-route the passive cutouts on the cabinet sides I will mount the new passives [/quote]

The way to re-rout would be to start by routing a circle that fits inside the pasive hole then place a larger peace of mdf inside the HDT behind the passive hole and screw that to the circle that you routed. Now you place a larger peace on the out-side of the box, this peace should have a hole in the midle to locate it to the center of the circle that is sitting in side the pasive cut-out. Now you can screw this together and you have 3 peaces that form a sandwich over the passive hole. Now you can fix the routing circle into the middle whole and rout through the top-most layer of the MDF and down into the underlying cabinet.

Well thats just how I would do it Tongue

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zinker Ex Member	Re: HDT MK I - alternate tuning Reply #21 - 10/24/05 at 17:26:59 Hrappur, That sounds like a winner. I can use the same setup for all 4 cutouts. What is the purpose of the mdf panel on the outside of the cabinet? is it to add stability and support or is it for something else that I am missing? Thanks for your help, John
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brad Ex Member	Re: HDT MK I - alternate tuning Reply #22 - 10/24/05 at 17:27:32 Quote: This design would allow the passives to be removable for easier tweeking. Now that's a great idea. Btw, I still haven't found any grill covers for the passives. Any ideas?
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brad

Ex Member

Re: HDT MK I - alternate tuning
Reply #23 - 10/24/05 at 17:52:10

[quote author=Corey link=1123604173/15#15 date=1129949322]Brad,

After a brief glance at your pics on this thread, it has occured to me that you glued your passives on backwards. The large dome should be facing out and should be visible from a front view. This loads the sound into a better dispersion pattern and further radiates sound to the chair with a better disappearing act. Time to get new passives if you are picky, I think it will make a difference.

Corey [/quote]

I'm not too worried about it either way. The passives are there primarily to boost/extend bass response and better load the main driver. Secondarily, they add "ambient" midrange that is much lower in volume and in any case should bounce off room boundaries before coming to your ears. You really don't want direct radiated midrange from the passives going directly to your ears since it's liable to muddy up what's coming from the main driver. Now after bouncing off room boundaries it should be time-delayed enough to not muddy things but rather add ambient reverberation.

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zinker

Ex Member

Re: HDT MK I - alternate tuning
Reply #24 - 10/24/05 at 18:12:57

Brad,
Grill covers would be nice, but I personally would be concerned that they would end up looking too obtussive and distracting. I want to keep the look of my cabinets as clean and sleek as possible. Having kids, though, I do understand the need for some kind of protection (Wow, that sounds like I was talking about birth control).
The other thing I liked about my chrome ring idea is that it may make the passives look more like drivers and less like circular pieces of foam. The new passives, with thier multiple surround design is a step in that direction. Grin

BTW does the dome on your new passives point to the inside? Is that what Corey is talking about? I personally would rather have them pointing in instead of out if its all the same for sound.

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Hrappur Ex Member	Re: HDT MK I - alternate tuning Reply #25 - 10/24/05 at 18:18:13 zinker the mdf on the outside is to clamp everything in place while you rout, otherwise the mdf circle inside the passive will fall into the cabinet The out side peace could be from anyold thikness of course and I only say MDF because I seem to have loads of it lying around
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ziggy Ex Member	Re: HDT MK I - alternate tuning Reply #26 - 10/24/05 at 18:33:25 I don't know if I might have missed something here or not. Why don't you just use a 1/4" rabbet bit in a router and follow the original inside hole. Thats what I do. BobZ.
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Hrappur Ex Member	Re: HDT MK I - alternate tuning Reply #27 - 10/24/05 at 18:59:27 The man has all the answeres ziggy is right that is the easyest way. It´s just that bits are expensive and if you dont have a rabbet bit and dont want to spend for one then the other way works for the straight bits. Cheap is my middle name you should see some of the home-made clamps I made to glue the HDTs together!
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brad

Ex Member

Re: HDT MK I - alternate tuning
Reply #28 - 10/24/05 at 20:56:57

cheap rabbet bits -->
http://www.pricecutter.com/product.asp_Q_pn_E_P14%2D2705

Btw, my passives look to be in backwards. Although both sides are "domed" the larger dome is on the inside. This really irritates me since they did not come with any directions - and logic told me that you don't want some big dome sticking outside the cabinet.
Still, I wonder if it makes any sonic difference? Ziggy?

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« Last Edit: 10/24/05 at 21:00:54 by Brad »

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Hrappur

Ex Member

Re: HDT MK I - alternate tuning
Reply #29 - 10/24/05 at 21:16:20

Thanks for the link Brad but I never buy cheap router bits, Cheap routers yes but the router bit is the important ´bit´(so to speak) unless you throw them away after use. I would never use a cheap/dull bit on veneer(even my cheapness has limitations) As for the dome sticking the wrong way I thought you were pleased with the sound of the new passives so why change it Wink

If it ain´t broke....

P.s I built the all of the HDT´s using just 2 quality router bits and a cheap no-name router /my Hitachi was at the shop

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« Last Edit: 10/24/05 at 21:21:39 by Rap »

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