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Hell, those aren't big ! (Read 136513 times)
Albert
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Re: Hell, those aren't big !
Reply #135 - 01/24/03 at 21:33:17
 
Use 3/4 inch white Melamine particla board for that stark look, and the melamine is bullet proof for little hands that like to use finger paints on your cabinets.
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Steve Deckert
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Re: Hell, those aren't big !
Reply #136 - 01/25/03 at 01:52:58
 


As far as finishes go, one thing I've thought about is wrapping it with the same vinyl as the guitar amp in the background of this photo.  Probably won't do anything until Spring in the way of finishes.

Here is a small pic of the left cabinet with new drivers installed.  The one on the right is a Peavy Scorpion.



I'm going to start posting about the horns here with pics here shortly.

Cheers,

Steve
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Steve Deckert
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Re: Hell, those aren't big !
Reply #137 - 01/25/03 at 02:05:15
 
Design notes: Jan 2003 - New Imperials

As usual the batteries in my camera are dead so pictures will be forthcoming.  I wanted to take a few shots of the bent wood horn.  I'm still experimenting with it.  At the present time I have a different compression driver in each cabinet.  The one on the right is an audiophile grade unit that goes up to 20K.  The one on the left, is the Selenium that only goes out to 9K, but can be used down to 600 Hz.  

I ended up leaving the left hand one in all this time because it actually sounds much better even though it lacks the top octave. Naturally I've decided the tone and timbre of the left side is something I can't live without but I've got to get more extension in the top.  

Last week I discovered a significant rise in efficiency as I was varnishing the inside of the horn flare.  This improved the situation somewhat with the left compression driver, but it will still have to either be replaced or supplemented with a super tweeter, something I hate to do.

Right now there is a natural balance of current between the three drivers in the cabinet and virtually no crossovers other then a single cap on the compression driver.  Adding another component will probably break the synergy.

Terry and others have been waiting to see details on how the compression drivers are mounted onto these bent wood horns but at this point it's too early to say.  My original idea, which I did, was to use a 3/4 board with a 1-3/8 hole threaded for the driver and mount it directly on the back of the lens.  I used plywood at the time and it proved impossible to thread properly.  Knowing I would have to resort to hardwood, and purchase a 1-3/8 fine thread tap I decided to cost of the tools may be less than ideal for the people planning to build a pair of these.  To cover all the bases I decided to purchase some plastic horn lenses from a surplus catalog and cut the threaded flange off and simply glue it to the back of the bent wood horn.  This is $5.00 verses the price of an expensive tap.  

Tonight I re-installed the left compression driver by using part of a plastic lens as mentioned above.  I cut the lens about 1.5 inches past the threaded collar because the square shape of the plastic lens matched perfectly with the square 1 x 1 inch opening in the back of the bent wood horn.  I knew that the plastic in this high pressure area of the horn would raise the efficiency a bit, and should be technically superior to the original method of mounting the driver directly on the wood.  

Interesting results.  The horn did indeed pick up more efficiency.  In fact with the varnish and now the plastic part, the sensitivity is now almost in danger of needing attenuation.  

Listening test - prior to tonight, the horn on the left always had better tone then the horn on the right.  Now with the plastic piece the entire speaker on the right hand side sounds better then the left.  Prior to this the speaker on the left always sounded better because it has a calculated amounted of stuffing behind the woofers whereas the cabinet on the right does not.

The sound that is coming from the left horn is now unlistenable.  It has that famous "horn" sound that makes you think your at a small live concert with a crappie sound man.  I was surprised that it only took 1.5 inches of plastic to ruin the sound.  Prior to this the horns sounded anything but like a horn, in fact I've been flirting with the idea of replacing my acustats with these speakers - in part because the highs are so good, open, free of any coloration, and non-beaming.

The conclusion is that the high pressure zone directly in front of the diaphragm is full of stress that is compounded by the first couple inches of the lens.  All lenses are smooth, especially there.  Controlled pressure release with pin holes, or specific dampening in the critical area of a horn determines the signature of the horn and effects every other aspect of its parameters.  In the original method using a 3/4 board with the hole drilled in it so that the driver could screw in, the end grain of the plywood that was left because I couldn't thread the driver all the way in.  The end grain absorbed the stress.  

Next step is to restore the original driver mounting and loose the plastic piece.  I knew from past experience that this was the most critical area of building a wood horn lens.  I did not realize however what caused most commercial horn lenses to sound like PA systems until tonight.  My conclusion is that if it is plastic, metal, fiberglass and does not trade a few dB with some carefully designed stress relief at the throat, it will sound like a horn.  My bent wood horns do not sound like a horn, the sound like and in fact better than my electrostats.  This is proof that the "horn" sound is really a byproduct of poor design.
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Steve Deckert
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Re: Hell, those aren't big !
Reply #138 - 01/25/03 at 02:34:16
 
A follow up to the above post:

I left the 1-1/2 inch plastic horn piece fixed to the back of my bent wood horn all week.  Each night when I go out in the shop I tried to listen to it.  Never made it past 4 minutes during any one night.  It is amazing how it has ruined the sound of the entire speaker.  

I have pondered the GIANT change in sound all week.  I have to admit that when I first hooked up the bent wood horns and listened (with the driver screwed into the wood) I was a little surprised that it had ZERO "horn" sound.  And also amazed at the absence of a beam and complete lack of peaks anywhere in it's response.  Over the past month, I have come to respect them to the point where I'm thinking they're better than my electrostatics.  Then my little mod with the plastic threaded extension and what I am hearing is the definition of the "horn" sound multiplied by at least four!

I realized that it is also the fact that the plastic throat is too close to parallel for proper wave expansion and is so on both the horizontal and the vertical.  To hear what this does to sound, just make a 10 inch diameter tube from poster board and tape it to the front of the woofer on your loudspeaker.  What you hear is a few octaves lower than a compression driver obviously, but the signature is the same.

I studied the plastic throat carefully and realized that most inexpensive horn lens are made this way, and that is where the "horn" signature got it's reputation.  Then I pondered why?  Surely they can't be this stupid...  oh, perhaps it's because it develops about a 10 dB peak at 800 Hz and gives the illusion that it's kicking some real ass when in fact it's not.

Anyway, it was an epiphany for me, I gained a deeper understanding of how critical the first 1 to 3 inches of the throat is and now understand why the bent wood horns originally sounded like QUAD electrostatics rather than like compression drivers.  Now I know how to make sure they stay that way.  I also realized that many people might make a lens similar to these and conclude that they suck because they improperly mated the compression driver to the throat...

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Steve Deckert
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Re: Hell, those aren't big !
Reply #139 - 01/25/03 at 02:41:44
 


This is a picture of the "evil" plastic thoat.  To kill the "horn" sound it made, I cut the threaded part off and sanded it until I had a threaded collar.  This way the outlet of the compression driver mates directly with the wood throat.  The 1 x 1 opening is carefully rolled into a dish shape to maintain a smooth transition from the outlet of the driver to the throat of the wood horn.

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Steve Deckert
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Re: Hell, those aren't big !
Reply #140 - 01/25/03 at 02:48:00
 


Here is a pic showing the 3/4 board used to receive the collar as well as hold the back of the horn up.  Setting beside it is the "evil" plastic throat that this system replaces.



Woops, another damn picture... by now I'm sure modem users are well, less then happy!

Steve
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Albert
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Re: Hell, those aren't big !
Reply #141 - 01/25/03 at 02:57:14
 
Hey Steve my Altec 811's and 511's have a slight chamber opening up just after of the beginning of the throat and it is not a casting anomally but actually part of the design. I wonder what this was designed for? Take a gander at the pics and take a shot at it.

http://home.internetcds.com/~adaatdh/511_top.JPG
http://home.internetcds.com/~adaatdh/511_side.JPG

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« Last Edit: 01/25/03 at 02:59:16 by Albert »  
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Brian
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Re: Hell, those aren't big !
Reply #142 - 01/25/03 at 02:59:54
 
This project is fascinating!  
Back on pg 4 Steve, you said: "acoustic bass on this speaker simply wastes Pauls 200 watt CLASS A all tube bass rig - also using 2 15 inch drivers. Imagine that for a minute. Imagine an acoustic bass growling with textured low notes that are tight and powerful enough to make a good sounding electric bass sound stupid. Well, this is what is happening."

This has lead me to wonder, has Paul played his bass amp through the Imperial cabinet?  I guess a road crew would not be willing to lug such a thing around on a tour, but it might be a nice choice set up in a long term installation in a night club where a performer was returning night after night.  
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Terry
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Re: Hell, those aren't big !
Reply #143 - 01/25/03 at 03:05:52
 
As a DSL user I am very very happy.  I was wondering how it all would fit together.  Steve I can't remember how low can the wood horn go in frequency of hertz?  Is this an exponential or tractrix curve?  This is a interesting learning experience much like some of the things I have gone through.  Where is your crossover point?

TG Grin
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« Last Edit: 01/25/03 at 03:15:56 by Terry »  
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Steve Deckert
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Re: Hell, those aren't big !
Reply #144 - 01/25/03 at 03:45:43
 

[quote author=Albert  link=1040842968&amp/135#141 date=1043463434]
Hey Steve my Altec 811's and 511's have a slight chamber opening up just after of the beginning of the throat and it is not a casting anomally but actually part of the design. I wonder what this was designed for? Take a gander at the pics and take a shot at it.

[/quote]

It rotates the wave front 90 degrees from V to H.

Steve
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chrisb
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Re: Hell, those aren't big !
Reply #145 - 01/25/03 at 03:49:29
 
nice job on the HF horns, Steve - still pulling those slivers out?

the resolution on my monitor's not fine enough to see, did you use kerfcore or timberflex- or table saw the kerfs in solid or ply?

As for finishing birch ply, my own personal tip is seal (wash) coat of solvent based lacquer, sand, spray pigment based stain of choice, followed by  3 -4 spray coats of pre-catalyzed nitro-cellulose lacquer, hand sanding between coats, progressively to 400G.
Better yet, laminate with cherry, walnut, maple, mahogany, beech, almost any quality veneer. Birch can be either really boring, or have tons of patches, poorly matched cathedral patterns, color variations  and mineral stains.

Once fully cured the better of today's lacquers are almost bulletproof, and never need touch-ups for gloss like oils or waxes do.  Of course any finish can be damaged .

Of course you could always go P-lam (which can be harder to work with than veneer, and never as pretty)  Obviously I've got some strong opinions here.


http://homepage.mac.com/tlinespeakers/TLS/FALL/images/Hugos-TL-pipes.jpg

http://members.shaw.ca/t-linespeakers/FALL/images/BD-Pipes-FE103A.jpg
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« Last Edit: 01/25/03 at 03:55:52 by chrisb »  
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John_M
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Re: Hell, those aren't big !
Reply #146 - 01/25/03 at 04:58:41
 
My wife likes the natural wood grain.  Maybe a simple clear urethane?  Hard to tell from the pictures how good that would look. Undecided
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bmar
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Re: Hell, those aren't big !
Reply #147 - 01/25/03 at 05:31:27
 
Nice looking project. You can also buy an adaptor that has female threads for a screw on driver to a bolt on pattern horn flare. This adaptor could then be mounted directly to your horn throat, eliminating any straight sided throat transition.
If you make a throat you might try a 12-16 degree angle for that short section. The conical throat section will help to eliminate peaking too.

Bill
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Terry
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Re: Hell, those aren't big !
Reply #148 - 01/25/03 at 07:25:00
 
Chris,

Was that vineer you used on your little bypolar VP's?  How do you router it on the 45's at the corners?

Steve,

What you discribed you experienced sound very similar to what I have experienced.  The best speaker I have ever heard was a Sounddesign A-1, a nearly 7' tall by 2.5' wide electrostac pannel.  The times I have heard horns done well, along with Lowthers in the Oris 150 horn, they both sounded similar.  Which to me seems strange.  I guess they have some similarities, one is that both are moving air by means of a diaphragm that is moving moving just milimeters at most.

To me the advantage of the horn is the simplest circuits you can couple it to, SET amplifiers.  This is horn driver thing is becoming more interesting by the moment.  

TG Grin
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« Last Edit: 01/25/03 at 10:17:42 by Terry »  
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Corpsdriver
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Re: Hell, those aren't big !
Reply #149 - 01/25/03 at 15:30:01
 
I have GOT to dig out my lenses, and take some pics to see what you guys think. i want to use them with my "Crown Imperial" project. but new drivers are WAY spendy...

Jamie
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