COOL!  8)I can picture Terry making a pair of these for his EV's. 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

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

[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

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

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.  

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!

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? -Matt

Continued...



The bass was very dry and super tight.  We quickly decided to change the send from the monitors to an aux channel where the output was not high-passed and more listenable.  At the same time both channels were mixed to mono so we wouldn't be hearing just one channel anymore.  From this point forward, the speaker was pleasing to listen to.  That was motivation to put on a CD and loose the crappy radio and so it was done.  

We listened to a couple of songs on CD at a high playback level looking for that familiar "Imperial Power" that wrecks the room also known as bass notes from hell and well you get the idea.  Remember, all prior models (about 6 pair) had all been done with a single 15 inch driver and built like the original plan.

I think we were both floored at what we were hearing.  First of all you forget the effortless power these speakers have - at least we did.  The most prominent thing that was different from prior models was the tightness.  The only speaker I've ever heard with bass that tight is my Acoustats.  They can play at 115 dB with less than 1% total system distortion and are the definition of tight.  This single Imperial sounded exactly like it but on steroids.  

When you attend a live rock concert with a sound crew that knows what's going on and is having a good night, you find yourself amazed by the power and the tightness of the kick drum.  Stereo speakers at home simply do not do that.  If you can picture this kind of sound in your mind, what we head come out of the Imperial was over twice as tight and extremely flat with bottomless extension that can and did shake the concrete floor.

Paul noticed that nothing in the room was getting wrecked.  By that he means vibrating.  Usually there are 20 things in the room that have to be quieted down because they buzz or rattle when you play the Imperial.  We just always thought this was normal but this time the sound pressure level was way louder than what it usually takes to start wrecking the room and not one peep from anything.  

Good room you say?  Not from this perspective, no.  There should have been 20 or more things that needed moved or weighted down.  We learned that the velocity and transient response (tightness) was so superior that it didn't give anything in the room time to be wrecked.  More like shooting a bullet through a door vs. someone pounding on it.  For both of us, this was some genuine enlightenment that basically means the nasty resonances of objects in your room are excited by distortion not pressure.

continued....

Here is the sound clip.  It is a recording of us listening to Jazz on the radio in mono using one of the new Imperial cabinets exactly as it is shown in the picture.  

In short this is a recording of the new Imperial speaker in the room as pictured.  It is a 44.1kHz 16 bit stereo wav file.  

This is a stereo recording of one Imperial playing in mono.

Be sure to burn this to CD and play it on your real stereo.  Don't waist your time trying to listen to it on your computer.

https://www.decware.com/imperialsample.wav

Durring the recording I had Joe (who was also there- a friend of ours) take some shakers and walk by the mics so everyone could see this was not a faked recording.  In the complete recording you can hear all of us from time to time in the background.  

Steve

Maybe the secret to the "magic" is the mis-matched speakers. Each could be correcting the flaws of the other.
Dave

increadible... even the top of the ride and the splash were there... Once again, i am on my knees, facing east, bowing to the Deckert. you need to hang a sign on your shop door that says "Welcome to Mecca"

Stevie!...Sweetie! I can believe you and Paul put another set of Imperial's together. And I can believe your finding something magical about them...but, did I read this right..you let Joe within striking distance of them! You know Japan has Godzilla, and well, from past experience, Godzilla has met his match. I have no doubt Japan would reward us handsomely if we were to keep Joe safely contained here in the U.S.

I shall have to stop by sometime and give them a listen to.

One more thing, I am real curious how 15" drivers sound when set up in proper stereo imaging, as they tend to beam start at round 600Hz.  So you would probably have a narrow sweet spot, and I wonder if they would sound as good on axis as the would slight off axis.  Just some thoughts I am wondering if a person can overcome.

TG

Hi Steve,
I am IMPRESSED... wow.  With junk drivers,even.  So when will the plans for the Decware Imperial become available?
Steve F

Not real suprised:

I've always contended that speakers make the biggest difference in an audio system.

The top octave is highly over-rated (as is the bottom octave, but you have to have it on the recording and have the right room to listen in).  This is one reason why single driver speakers can work.

IMO, there's still a lot of life left in the single channel concept (cheaper, smaller, more coherent, many recordings don't support a decent stereo image anyway).

BTW, Wayne Parham from Pi speakers suggests filling the voids behind the panels with expanding foam.

Don't have a CD burner so I'm missing out on the recording.

I'm eyeing the end of my living room right now, looks like there's enough room to fit one on either side of the window.  You know, I've been wanting to reside the house anyway, maybe I could build them into a bump out and not lose floor space (the room fits the golden room dimension ratio as is).

Steve, please provide some specifications.  Could these be driven by a Select?

Steve,

What about drivers for the horns, what do you plan on using for the top end?  Looks like those lenses should be good down to about 800Hz at least.

TG

hi steve: awesome speaks! I have a pair of altec 416-8b's that I want to mate with my 802-8d drivers on 511-b horns. do you think your cab design could be adapted for a single 15 inch woofer? I'd like to build something fantastic for these great old parts, maybe even a wooden horn too?

envious angus

Darn, I downloaded it and I can't play it, with anything I have I have four programs that say they can play wav files, and none of them recognise it.  :'(

TG

P.S. Steve, can you point my to where on your web site i can see a photo of the Imperial horns, with Bendi in it.  I just wanted to compare this one a bit.

I burned a copy of the recording, and took it to my HT room, and played it in several configurations beginning with stereo w/o sub on my KLH model 17s, then my model 4s. then my a/d/s l-1590s and so on. THOROUGHLY IMPRESSED! I think i am going to put my 3 main pairs up for sale and build a pair of Imperials! And no, Elvis, (my HWK-15) aint leavin the building! I will deliver anywhere in the Pacific NW!

Terry,

Bendi can be seen laying in the Imperial during the start of the visual H. Fidelity tour as well as in an article about hi-fi and home theater.

Corey

On Steve's file Win Media Player opens but it come up "data is invalid".

Peter, the MP3 works. Thanks!

Den

>Anyway  shows to go ya, you can't really change universal laws,  what men did 60 years ago to make music sound good still will today, we just made a few changes but we really didn't make much more progress.  We just figured out a whole bunch more about what won't work.<

To judge by some of the speakers being made today, some people still haven't figured out what don't work.
Dave

You think I will get all that from the mp3, as the original file will not work with any of the programing I have here.  mp3's are Ok, but they are somewhat compressed and don't give you a good sense of imaging.   The original wave file if it worked proabably would do a little bit better, don't you think?

TG

I love my Walsh 4's but thave had them for many years and have the bug to change to some kind of horn. (4's are for sale) they are in my basement rec room which is quite large. I have about 12 hours of searching the net in the past few days (I know get a life) for some rear loaded horn plans EXACTLY like these (single 15 would be better). All I found was more PA stuff.  I just scored a pair of old Frasier wood horn lenses on e-bay. And I just ordered some Selenium drivers. I have a very old set of EV drivers as well along with the matching EV tweeters, ST35's I think they were. I was almost settled in on some Altec 816's till I found this thread, Steve, post the plans, please. I just ordered the crossover parts.
Mike

Regarding Steve's adaptation of the Jensen Imperial, perhaps some of you would find these links interesting:

Jensen Imperial horn drawings:
http://home.earthlink.net/~lotusblossom/_wsn/page3.html

some Imperial pics:
http://community-1.webtv.net/KerrB/VINTAGETUBEAMPHORN/page6.html

Peace,
MikeS

Peter said: "The source of the recording is one speaker cabinet, so other than the background shakers etc, most of the 'image' is artificially created. Whether it was caused by the recording or by the mismatched drivers who's to say."

This makes me think the speakers may sound best with mismatched drivers when listening to only one, but when listening to both of them well matched drivers may be neccesary to create a sound stage.  
Not an important point since Mr. Deckert will do an empirical test rendering my speculation moot, but I love to speculate.  

I'm glad I poked my head in to take a peek at what you guys have been up to.  I liked the shakers myself.  Real purist recordings are so nice sometimes.  None of the over compressed flatness of the "finished" products offered as music.

As for the sound from the horn...  I think its pretty cool that you could capture a reproduced source with such finess.  I do however question the accuracy of all of us listening to a reproduction of an event through our own colored speakers and equipment.  I know you mentioned that we would only be exposed to the concept of the event and that we wouldn't have the true experience reproduced for us because of this inconvienence, but I do wonder if what we're all hearing is the same thing?

Oh, and I forgot to mention...  Steve, Those things kick ass!  :D  Very impressive horn's you've built.

Granted I've been out of the scene around here for a while, but we've always seemed to be pretty happy with what we're using.  So I'm just curious as to how much of the actual horn we're getting across on this little file.  I'm very pleased with the sound from the file, but it does remind me of radio quality in dryness. (which is why I was enjoying the moving shakers so much)  Volume is another issue as you correctly stated the background voices are very faint.  I'll admit I only listened to the file once and was playing it straight through my sound card into my preamp.  So right there is a source of variation from the source I'm using vs what most of you probably did. (I don't have a burner on this comp)  I can say that the soundcard i'm running is rather neutral for the most part. (I've tested it as an RTA with software and a decent mic)

I like the premise of the experiment.  I thought it was neat hearing a very dynamic set of doomed speakers perform like champs, but I just wonder how much of the experience is lost in transmission.

I take that dispute back. I was going to put a 'mp3 challenge' up as a new thread to see if you really could tell the difference so easily, despite that I previously couldn't.  So I prepared a clip, and then when I A/Bd my specially prepared clip the difference was indeed obvious -- even with my laptop soundcard.  I should have used LAME to encode it.  Sorry about that folks.  It must be the syntrillium plugin.


--Addendum:  Even so, the crazy imaging is still there.  Where did that come from?

>Even so, the crazy imaging is still there.  Where did that come from?<

If the recording was done with a pair of mics for stereo, there will be some kind of image even from a mono source. The room itself will contribute different sounds from different directions, thus a stereo image of some sort will develop. At least I think so.
Dave

[quote author=Audioillusion  link=1040842968&amp/60#62 date=1041634421]
I've done MP3 A/B's before, I nailed the MP3s every time.
[/quote]
Hehe.. I think with the right tools, (i.e. LAME on the r3mix setting or some of the 'better' alternatives) I could persuade you otherwise.  I have done A/B on those before with far better kit and been gobsmacked.

But not right now.. it's late

As for the image, I'd *really* like to know if it was there 'live'.   I seriously doubt it.  Remember Steve's recording was far short of 'audiophile' quality, so that might have had something to do with it.

My secret theory is that all imaging is artificial --either intentional or incidental --  how sought after it may be.  Especially 3D imaging.

Audio Illusion wrote:  "It's my belief that the best possible recording is one with the least amount of distance between the microphone and our ears. In other words: the simpler the recording the better."

There is a good commentary on this at http://www.xs4all.nl/~rabruil/dongabor1.html  which is a site about Don Gabor's Remington record company in the early fifties.  Apparently Don did not have the money for elaborate equipment so he used simple stuff and accidentaly made great records.  Lots of fascinating biographies of classical pianists and violinists at that site too.  

Boy am i gonna catch hell for that one...

There is an interesting driver for sale in the MCM Electronics catalog for $73.00 each. Part #55-1880. Specs are:
Power handling-400W (I don't think a Zen would be a threat)
SPL- 98dB/W/M 2.8V
Fs- 28Hz
Vas- 16.36 cu.ft.
Qts- .231
Qes- .274
Qms- 1.457
Xmax- 4.4mm/.17"
DCR- 6.6ohm
Magnet weight- 100 oz
Voice coil- 4"

Not sure how high up the frequency range will go. It seems to be hard to get large drivers that will go high these days.
  This driver sounds interesting for the money, and I think it would work in a horn. But then, what do I know  ::)
Dave

Steve, I want to hear the latest.....I know...you said you will try to post over the rest of the weekend....I will be patient

Stone of Tone 8)

Okay, I think an update is in order!

First a few observations about the miss-matched drivers.  One came from a Plush Bass Cabinet and featured a 2 inch voice coil.  It has incredible tone, and basically no mids.  It was the woofer on the right in the pictures.  The left woofer was an inexpensive Eminence PA speaker.  It not only has a midrange but has a 10 dB rise in the midrange a 2K.  This is why the speaker had such good presence and tone.  

When you walked up to the speaker and listened to each driver at close range, the one on the right sounded wonderful and the one on the left sounded like crap - enough to make you instantly take 3 steps back.

The new woofers I ordered came in.  They are probably not ideal for this project, but we're thinking about selling them for sub woofer projects so I wanted to try them.  We mounted a pair of them in the other cabinet and as I mentioned before, everyone leaned towards the miss-matched pair in the other cabinet.

The new woofers also roll off quickly, and sound very similar to the Plush woofer with the good tone.  After playing around for a couple nights I decided we would need more midrange like we had with the miss-matched pair, but without the nasty peaks.

I had a pair of Peavey woofers that when compared to the miss-matched pair fell right in the middle.  The reason the midrange was important to get from the woofers rather than getting it from the bent wood horn is in a word - "hit".   The snare drum crack that comes off so tight you jump, and the kick drum that pops your chest is a function of the higher frequency response of the 15 inch woofers.  The Peavey woofers had the "hit" we needed but no low bass.  The new woofers have the low bass but lack the snap.  It is difficult to find both in a single 15 inch driver.  The new drivers has response down to 30 Hz.  The Peavey drivers are down to around 70 Hz.

We installed one of each in each cabinet.  We put the Peavey driver towards the inside on each side. This is working well with no problems of any kind that we can see or hear.

I installed 1 inch of fiberfill on the back of the interior chambers behind each woofer on the left cabinet.  The right cabinet was left with no damping to see what is better.  Interestingly, most people choose the cabinet with no stuffing because of the added presence it has.  For outdoor use I would recommend it that way.  I like the smoother response of the stuffed cabinet and recommend that for indoor use.  I was pleased to find that the shape of the chambers behind each woofer were not creating any standing waves that hurt the sound.  

Steve  :)

"I plan to give it away for free to everyone following this thread"

pant, pant...drool, drool.......my saw is warmed up and ready to go!

ok, i am ready to buy the plans... i may overdraw my account,  but i feel these are worth it! Anyone in the market for a pair of a/d/s L1590's? i need to finance a pair of Decware Crown Imperials!

Had an interesting revelation this evening while sitting in the shop listening to the Imperials. A new audio term that I will call "transient balance".  While I was listening tonight and pondering the contrasts between what I was hearing from the Imperials and what I would be hearing from a conventional pair of audiophile speakers, I realized something.  

One of the many reasons why conventional audiophile speakers could never sound like this is because the transient balance of regular speakers changes from driver to driver - from woofer to tweeter.  It also changes between the bass and midrange frequencies of a single conventional woofer.  This is what lets your mind know that you are listening to speakers rather than the real thing.  I mean let's face it, if your stereo actually sounded real your mind would short circuit and you would be struck with fear - not unlike seeing a real ghost.  

Anyway, these speakers seem to have a transient signature that is in tact across the entire frequency band.   Besides the Acoustats, I have never heard a speaker that did.  And even though the Acoustats are technically superior on paper, the horns have velocity in the bass and dynamics that even the acoustats could only dream about.  

Transient balance is a definition of transient response across the frequency balance of a loudspeaker.  Regular speakers have wavering transient balance that usually declines with frequency.

All of this is frankly a surprise to both Paul and myself.  Even though this is the 6th time we've built Imperials, they were all by the original plans and with a single driver.  And they were good, but warmer and slower.

Remember, or FYI, back in the 1980's Paul made me build a pair of these so his wife wouldn't see him making them.  I guess he thought he could hide them in his garage.  I agreed and after finishing the first cabinet I robbed a 10 inch woofer from a pioneer bookshelf speaker and stuck it in the cabinet to see what would happen.  The bass response I heard come out of that single 10 inch woofer was so mind blowing that I made a decision right there and then to devote all my attention to audio, the reason DECWARE actually came to be.  I heard two identical speakers, one in the bookshelf cabinet and one in the Imperial and could barely grasp the difference.  It taught me in no uncertain terms that there WAS magic in audio and I wanted more of it!

Cheers

Steve

>I have never been a person to listen to music loud because my distortion alarm always goes off about half way there.  On these speakers it has not gone off yet, and I'm sure we have listened in excess of 120 dB from time to time.  My ears have yet to ring from listening to these, yet at lower volumes our own band has created the dreaded ringing you hear when you go to bed later that night.  That means ringing is not tied to SPL, but rather a side effect of distortions.<

If you recall, a while back I mentioned having read an article about evidence suggesting that one could listen at much higher levels to sound that sounded good without damaging ones ears. It had to do with the ears being relaxed because you are enjoying what you are listening to. Any distortion would cause discomfort, and cause the eardrum and such to tighten up, and you have listener fatigue soon followed by ringing, and eventually, damage.
I don't think anyone took it serious at the time.


On another topic:
>I heard two identical speakers, one in the bookshelf cabinet and one in the Imperial and could barely grasp the difference.<

I have had similar experiences. The 10 inch drivers I have now sound far more alive in the TQWP cabnets then the one fourth the size bass reflex boxes they came out of. The origional boxes are well built and seem to be tuned correct for the speakers. The bass from the TQWP's is just much more alive sounding. Makes me wonder why anyone would want a small bass reflex speaker anymore.
Dave  

Steve,

What you call "transient balance", I call "linear dynamic tracking", I think we are speaking to the same thing.  Meaning that the entire speaker can product the same level of dyanamics at all frequencies equally particularly how this relates to the speed of each driver.

My ideas of how to go about achieving this are a little different, so I am very interested in what you come up with in the end.  I am thinking of having a compression driver that extends as low as possible, below 500Hz, and a front horn loaded 15" woofer below that.

I like your idea of mismatched drivers, having that ability by two 15" drivers in each speaker is a real plus.  Often I feel it is not the tecnology that is flawed often, but how it is implimented.

I think with your offer we will have more people following this thread now.  I can't wait to see what the total size of these speakers is, so that I can see if I have enough room for them to try out.

TG

My Dad is no longer using his barn. Perhaps I should build these and turn the barn into a suitable listening room. The haymow, with arched roof, is part of a smallish barn, but still way bigger then a typical living room. What a place for parties!
Dave

Terry,

Folded or not, TQWP enclosures are floor standing.  The interaction with the floor is an important part of TQWP bass performance.  A pair of floor standing speakers in my MULTI-purpose living room is out, as there simply is no room.

I have 2 pairs of small bookshelf speakers that get exchanged.  The 1st pair are 1st generation ProAc Tablettes that Mr. Deckert did a MAJOR overhaul on a while back.  The bass performance of the Tablettes is remarkable considering that the cabinet volume is about 1/3 ft.³.  I power the ProAcs with either my H/K Citation II or my AVA FET-Valve.  The efficiency of the Tablettes is TOO low for them to be a good match for a ZEN amp.  The 2nd pair of speakers are my own design that use 94 dB. efficient (nominal) drivers in a 0.55 ft.³ enclosure. The main driver runs full range.  A 2.2 muF. capacitor keeps low frequency information out of the tweeter.  FWIW, the simulation plot for the main driver and 56 Hz. vented enclosure combination is flat within 1 dB. down to 50 Hz.  I use the "homebrew" speakers with my SE84Bs.

STEVE,

Do the Imperials sound best when close to the wall  ?
I think most would not want them out from the wall
as they are pretty hefty.

What do You think the overall Speaker Impedance
will be when all said and done ?

4 ohms would probably make the most sense, as
this would work well with ALL the Zen amps.
Of course with the very high sensitivity this probably
isn't a large concern.

Homey

Steve,

Glad to hear you will make the modified Imperial + horn lens plans & white paper available to us.  I've been using an inexpensive Alpha12 Eminence PA driver (low ZMAX) and cheap HF horn with my Zen for many months now and continue to be impressed with the BANG I'm getting for the BUCK, even though I haven't given the LF driver a chance to show its stuff in a huge cab like the Imperials.  How interesting that we're talking about such 'old' technology and how good it can sound...

Peace,
MikeS

This project is really interesting, I just can't convince myself that 2 speakers that would be OVER 6 FEET wide would work very well in my listening room with it's 10 foot wall!

I think it would really convince my friends (not to mention wife) that I'd finally lost it.

Happy Listening,
Jim

I never had it to lose in the first place... i did rent some of "it" for a few days... then i left it somewhere... i hope someone gave it a good home.

Jamie

Steve,

Have you ever thought of trying the JBL 2226G's in this cabinet.  I would think they would work well, sound good, and be a good match for a Zen SE84CS with their 4 ohm impedence.  I recently heard these and have been very impressed with them for a high efficiency driver.  They have a fairly smooth frequency response as well, with nice bass extention.

TG

UPDATE

9:17 pm.  I'm beat.  The bed is calling... back hurts, thinking about skipping the nighty ritual of sitting out in the shop listening to the jazz station on the radio (with the Imperials).  9:41 pm. Oh what the hell...  9:51 p.m. I sit there in my chair staring at the bent wood horns thinking I really should at least varnish the other one so they match.  10:00 p.m. Standing on my tip toes varnishing the insides of the horns - while listening to them of course.  

(Every now and then the audio Gods decide you need to know something and give you the strong spontaneous urge to do something they know will cause a chain of events that allows them to teach you something.  You always know if the discovery was your own, or if it was an intentional lesson by the sudden spontaneity of it.)

The most amazing thing happened while I was varnishing.  As I applied the varnish, while it was still shiny and laying on top of the surface, the sound would come out of the varnish!  Just a 6 inch square area in the throat raised the presence by 3dB. It was unmistakable, yet I couldn't believe it.  Before you know it, I was varnishing like a mad man trying to get the whole inside of the horn wet before it would tack up because as soon as it tacked up the effect went away.

My overwhelming gut feeling is that there is more to it than just the difference between the shiny or rough surface.  The sound was magic.  These horns are working so well it's really amazing me.  The dispersion is simply incredible.  Absolutely NO beam even at a distance of 1 foot away.  In any case having a glass smooth finish inside THIS horn raises the output by several dB and widens the dispersion angle by a very noticeable amount.  Having a wet finish, like liquid, creates the magic as the surface tension between the air and liquid apparently isolate the wave front from the resonance of the horn walls - improving coherency.  Oh God, I'm starting to sound like Terry.  :-/

hmmmm, im thinking horn tweeks now, wax, crisco, jelly...

Continued...

This argument could also lend support to the debate on microphone placement: close or far.  Close micing generally exludes the parts of the instrument that are farthest away from the mic.  A mic that is farther away will capture most or all of the sounds coming from the instrument, but without the emphasis of one source over any other.  Hopefully the artist is getting what they want from what's being recorded or broadcast.

In the end it doesn't suprise me that mismatched drivers lend a more natural sound in this design.  Maybe Steve should PLAN on having 2 different drivers in the final design, if that's what sounds best!

Got a question about those wood lenses.  When you notched the back of the plywood to allow for the bend did you cut through all but the last layer of ply?  It sure looks like it from the pictues!  Is plywood usually consistent enough or did you have to make a couple goes at it to get it just right?

How far you mic an instrument, and how it sounds on play back I feel depends on the play back system.  The better the playback system the better distant mic-ing sounds, but on low fi stuff close micing sounds much better.  Don't even think of asking my why, but I know it is true.  When I go to listen something, I always take a recording that I know most of the instruments are recorded from a distance.  Piano and drums especially take on a spacial property.  Most would feel these are not as good of recordings, but on a good systems they blow all that close mic'd stuff away.  Of course the type of mic used makes a large difference in all of this as well.

TG

Wax, that is a little over simplified but we will let you slide this time.

Oh, it's the old resonance magnifaction through a multi-phasic conductance medium theorem, is it. This argument does have some merit, as it is well known. If the forcing frequency is equal to the natural frequency the magnifacation factor can be quite large. But the fundamental is still a coefficient of viscous damping and is not the same as the natural frequency, this of course is a result free vibrations. On the other hand, it's possible the oscillations could be under-damped which of course means there will be a diminishing amplitude of the sound wave at that locus and therefore the resultant noted increase is the result of psycho-acoustic aromatic hydra-tetra-cannibinols that the government has surreptitiously added to the varnish. In any event it's still fluid dynamics..."a less slick surface!!!" They just don't teach techno-babble like they used to..Sigh.

Trust me David, I know my vibrator's and fluid dynamics.

Let's try and keep things clean Wax...thanks

There for a minute I thought Ms Wax may have inhaled a bit too much fumes as well.
Dave

didnt i mention something about mic tecniques and dumping in digital bullthingy ages ago?

Jamie

[quote author=John_M  link=1040842968&amp/90#103 date=1042634820]

In the end it doesn't suprise me that mismatched drivers lend a more natural sound in this design.  Maybe Steve should PLAN on having 2 different drivers in the final design, if that's what sounds best!

Got a question about those wood lenses.  When you notched the back of the plywood to allow for the bend did you cut through all but the last layer of ply?  It sure looks like it from the pictues!  Is plywood usually consistent enough or did you have to make a couple goes at it to get it just right?
[/quote]

I do plan to have two different drivers in the final design.  It is just working way to well.  It makes it possible to keep this a two-way design.  

As for the wood horns, yes, I cut to the last layer.  The two I built were the first trys.  They are not perfect.  However I know now how to design the jig to make it less painful to build.






Here is a picture of the new 15 inch drivers I got.  I'll take a pic this weekend of the cabinets with the drivers installed.

[quote author=Steve Deckert  link=1040842968&amp/105#119 date=1042864486]

Here is a picture of the new 15 inch drivers I got. .

[/quote]

OOOOHHHHHH!!!!  Pretty!

Could be JBL, Beyma, P audio.

I'm curious too!

Steve F

Ok Steve did you pick this speaker outfit because of their cosmic intro graphics?  ;D

I did not see any usable specs on the 15 though. Do they provide TSP's on their pro drivers?

thats great John , did you cover up the background to make them look smaller , i dotn have the waf to deal with yet, not gonna get married til i meet a woman who approves of this hobby, and i figure if i build a pair before i get married, she wont make me get rid of them, speaking of which, how are those blueprints coming Steve? -Matt

Steve, have You played Your new push pull amp through Your new Imperial speakers?  How do you like the signature combination?  

Oh do I ever have experience staining burch plywood, learned the hard way you need to use a pre-stain, this way you get an even coating and avoid any blochy spots.  This is my one tip for birch plywood.

TG

I wonder if a dye stain would be better than the pigment based Minwax products. I made the mistake of using Minwax on the Poplar (solid wood) I used on my Hedlunds. Lets just say, I will be painting the wood parts for sure.  ;D

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.

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.

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.

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

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

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

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

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

here is the link to pics of my lenses, i hope they will work on the imperials...
http://corpsdriver.home.attbi.com/id19.htm

Give me line of credit, I still learning to making web page.

Jamie

Yep, model 9999062 would be fine, it's just a collar.

Steve,
Would you ever quit doing this!!!! Now I have to think of where I can put these things (once I build them) Do you have any idea how expensive houses are in Ireland?
I bought a pair of the original radial drivers years ago when Steve was still playing with them because I read his white paper after he built the prototypes. Now I am going to have to get these plans and build these monsters. I guess the only consolation is that there is no hope of doing it anytime too soon. Try as I might, they won't fit into our two bedroomed apartment. Please put me on the list for the plans though as I will build them if it kills me.
Neil.

Okay folks, as promised here are the plans in a .pdf format.  I will be offering them on the site for sale in both an online format (this) and a full blueprint.

The file is located here:

https://www.decware.com/forumtemp/imperial.pdf

the username is: forum
the password is: imperial

This file will remain here for a VERY limited time and then it will be deleted.

Have fun!

Steve  ;D

Thank you Steve,  I hope I won't take forever to make one of these - or maybe a pair.  
Brian Albin