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Hell, those aren't big ! (Read 132485 times)
Steve Deckert
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Hell, those aren't big !
12/25/02 at 18:02:48
 
It was a cold winter night just before Christmas, a hot fire in the wood stove... lots of power tools, wood and beer with too much snow for anyone to bother you.  Good tunes in the background and no phone or computer.  DECWARE's self-prescription for a badly needed vacation - results pending.

Paul and I have been building a new pair of speakers for ourselves.  You may remember from taking the visual tour of Decware, the Bendi speaker(as it has come to be known)?  

Just thought it would be fun to share some pics of our recreational activities as they happen.  

I'll be adding more pics as things progress over the next few days..

Cheers  ;D



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hurdy_gurdyman
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Re: Hell, those aren't big !
Reply #1 - 12/25/02 at 18:15:00
 
COOL!  8)I can picture Terry making a pair of these for his EV's. Grin I'd love to have big efficient horns in my living room, but I don't really want to lose my wife at this time, so it'll have to wait.
Look forward to more pics.
Dave Smiley
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Terry
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Re: Hell, those aren't big !
Reply #2 - 12/26/02 at 01:08:09
 
Hey flip those babies over with the speakers on top and they would be perfect!  I wish I lived closer to someone that would help me build speakers, I have to make jigs to hold the other end most of the time.  Takes me as much time making things to take the place of another person than to make the speakers.  I can now cut a piece of MDF by myself with great precission.

Keep us posted Steve, I like this kind of project.  If only I had the room for the Jensen Imperial Horns, that project sure looks a like the Imperial horn, but a little smaller.

TG Grin
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« Last Edit: 12/26/02 at 08:45:38 by Terry »  
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chrisb
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Re: Hell, those aren't big !
Reply #3 - 12/26/02 at 17:09:48
 
Steve: aside from the obvious weight factor, do you find any sonice advantages to plywood over MDF.  

If that's Meranti ply, watch out for slivers - they'll dig deep and fester for a week if you let them

Is that power bar UL approved?

Can't wait to see the grill covers (inspired by the famous Ed Shilling leopard skin "twins"?)

Nice work on the updates to the listening room page, and thanks for the peak at the business end of the Dechorn.  Have you already named the driver(s) utilized in the main section?



cheers, and happy New Year's  all
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Steve Deckert
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Re: Hell, those aren't big !
Reply #4 - 12/26/02 at 18:11:43
 
Chris,

The only obvious advantage is strength.  MDF has more mass.  I've made these imperials from MDF before.  The weight is lucid.  These are being built from Luan (sp) a form of Redwood.  It can lay outside in the rain for the entire summer and will not warp.  I have gotten so many splinters from this stuff I just quit taking them out.

Terry,

These are the 1956 Imperials, however we have redesigned them to be twice as strong and twice as easy to build.  If you've ever seen the original 1956 plans, they are a joke.

We will be running these with the woofers on top.  I had planned to run coax drivers but I ran into a few things, 1) not very many to choose from, 2) pricey, 3) most have limited low freq. response.   I have decided to go with conventional pro woofers and load a horn with a good 2 inch compression driver.   We already know that this requires a serious horn lense for the compression driver to keep up.  With two 15's in each cabinet it will be even more difficult.

I needed a challenging project while Paul was gone so I decided to build the horn lenses myself.  I've done this before, but they were only 20 inches wide.  This time I'm going to make them bigger Smiley




The trick to building these is self-inflicted temporary ignorance of the compound radius angles involved.  Once you reach that state you may begin. (beer helps) Then once you've spent the entire day cutting parts the realization that there are severely complex angles to cut is balanced by the time you've invested and you really have no choice but to press on.



We've got both speakers together now, just working on the cleating and trim.  I'll post some more pics tonight or Friday.

Steve
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« Last Edit: 12/28/02 at 03:02:31 by Steve Deckert »  
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Terry
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Re: Hell, those aren't big !
Reply #5 - 12/26/02 at 23:32:34
 

[quote author=Steve Deckert  link=1040842968&amp/0#4 date=1040926303]

These are the 1956 Imperials, however we have redesigned them to be twice as strong and twice as easy to build.  If you've ever seen the original 1956 plans, they are a joke.

[/quote]

Steve,

Why are those plans a joke?  I think I have those plans.  Good idea on the plywood, I know redwood is very light for its size and strength.  If the wood you are using is similar it should be great.  To me the lighter more porous the wood the lower its resonance, and if it resonates below the usuable frequency of the driver all the better in my opinion.  Let us know what drivers you have chosen, and what efficiency you expect.  How about those horns Albert has Altec 811's 117 1w/1m?  They might keep up with two 15" bass drivers.

TG Grin


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Steve Deckert
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Re: Hell, those aren't big !
Reply #6 - 12/27/02 at 17:00:58
 
[quote author=Terry  link=1040842968&amp/0#5 date=1040945554]


Steve,

To me the lighter more porous the wood the lower its resonance, and if it resonates below the usuable frequency of the driver all the better in my opinion.  TG Grin



[/quote]

Terry,  actually the lighter the wood (less mass) the higher its resonance will tend to be.  You could not get a speaker cabinet to resonate below the usable frequency of a woofer unless it was concrete.  Most objectionable panel resonance in speaker cabinets can be found between 140 and 600 cycles.  As we add bracing or increase the panel stiffness (by adding another panel for example) we push the resonance up past this area so that it no longer effects the mid bass and lower mid range of the woofer. Grin

The plans are a joke because they are dimensioned like a puzzle with conflicting measurements and angles that don't jive.  Also it is obvious by looking at the original design that is was intended to be as light as possible.  The joinery is weak, as is the cleating technique.
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« Last Edit: 12/28/02 at 02:57:32 by Steve Deckert »  
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Terry
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Re: Hell, those aren't big !
Reply #7 - 12/27/02 at 17:20:40
 


That is interesting, that contradicts an experience I had here recently.  I use MDF in all my protype cabinets, because of ease of workability, but prefer plywood as it has a more natural sound to me.  Could it be I like the resonance of plywood?

Sooooooooo, what drivers do you have in mind?  I have been looking at several lately for bass horns and am extremely curious.

TG  ;D
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Steve Deckert
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Re: Hell, those aren't big !
Reply #8 - 12/28/02 at 02:45:20
 



Terry-  Yes, that's exactly what it is.  Plywood resonance can add objectionable OR pleasing colorations to the sound.  In the case of these Imperials, the bottom and top are double thick, as are the sides of the enclosure area (source of energy).  The horn is intentionally left as a single thickness and supported by large stiffening cleats.  This allows the large rear panel to resonate in a complimentary way.  Not unlike a musical instrument, careful design and control of panel resonance can make or break the signature of a loudspeaker.  It's an esoteric and ambitious way to build speakers making it obvious why so many just go for inertness.  Here is a photo of the rear panel and stiffening members from looking down the horn.

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« Last Edit: 12/28/02 at 02:52:16 by Steve Deckert »  
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Steve Deckert
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Re: Hell, those aren't big !
Reply #9 - 12/28/02 at 02:51:03
 


Here is another picture of the construction.  I think we're at around 5 sheets of plywood for each cabinet.  Basically around $300.  This will grow to about $500 by the time everything is said and done.  

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Corpsdriver
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Re: Hell, those aren't big !
Reply #10 - 12/28/02 at 03:07:16
 
I can hear the "Tim the Toolman" grunts from here...
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Steve Deckert
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Re: Hell, those aren't big !
Reply #11 - 12/28/02 at 03:10:29
 


Here is where we're at so far.  The cabinets are largely completed and ready for sanding, trim and finishing.  As you can see we couldn't stand it so we dug some old 15 inch woofers out of the bone yard and hooked them up.  I'll have a story about what happened when we turned it on.  Give me some time to write it - for now lets just say it was memorable!
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Steve Deckert
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Re: Hell, those aren't big !
Reply #12 - 12/28/02 at 03:23:21
 


Just kidding !  Okay back to working on the story!

Cheers,

Steve Grin
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« Last Edit: 12/28/02 at 03:35:25 by Steve Deckert »  
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thedude
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Re: Hell, those aren't big !
Reply #13 - 12/28/02 at 03:47:36
 
hehehe, weeeeeee
remember to wear ear protection when blasting those monsters, those high frequency horns look awsome, what is the low cuttoff, and i like the way you made them, just cut, bend and glue right? Smiley -Matt
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« Last Edit: 12/28/02 at 03:49:57 by thedude »  
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Steve Deckert
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Re: Hell, those aren't big !
Reply #14 - 12/28/02 at 04:28:00
 
The story about a first test listen to one cabinet in mono.

As I mentioned, we couldn't stand the anticipation and even though drivers have been ordered we just wanted to hear something come out this new horn.  We dug around and each of us found a woofer.  One was an old bass musical instrument speaker and the other was more along the lines of a PA driver.

The idea was that we would play the radio through one cabinet while we continued to work on them.  We thought we'd kind of get an idea how these cabinet alterations and improvements effect the bass.  To drive them I simply unhooked a floor monitor that was in the room and replaced it with an Imperial.  The amplifier behind it is a 400 watt Ross - the equivalent of a decent audiophile solid state amp.  

The source was a $70.00 Pioneer tuner with no antenna fed into the mixer behind my drum kit.  I listen to this stupid tuner through the monitors all the time when I work out here and have never once stopped and said, "gee that sounds really good!".  

As soon as we turned it on, Paul and I both stopped for about a minute and stared at it.  The sound I heard was so tight that I made the comment I thought maybe the two woofers were wired out of phase.  We listened to it for a few minutes frankly not sure what to think.  

Continued...

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