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

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

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




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

[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



[/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.

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.

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.

I can hear the "Tim the Toolman" grunts from here...

Just kidding !  Okay back to working on the story!

Cheers,

Steve

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...

We ran through several more songs with different type of music and before you know it we weren't finishing the cabinets like we planned to.  

I think we both found it interesting that two grossly mismatched woofers could hit so precisely as one, not to mention sound even listenable in the midrange and high frequencies.  We simply ran them full range with a flat signal.  Now, unlike the original design that took months of playing musical woofers until we found ones that worked, this new cabinet design is obviously not going to give a shit what you put in it!

The horn lenses you see in prior pictures setting on top are not hooked up.  We don't have the drivers for them yet.

I expected to turn this speaker cabinet on, crank it a few times and reduce it to a background listening level so I wouldn't become tired of crappy mismatched speakers.  Instead we spent the rest of the evening from I guess around 7pm to 2am listening to it with bigger than life grins on our faces!

What clinched it was around 8pm when Paul flipped the crappy little tuner to our local public radio station that played jazz and blues.  It was the first time I heard the tuner sound good.  But it goes way beyond that...  Good is okay for about an hour.  Anything longer than that usually has to be great.  We had it cranked, but it was so clean that it didn't seem the 120 db it probably was.

Song after song, the cabinet just sitting there in the middle of floor and no good reason why it should be sounding this good.  Hour by hour and beer by beer we simply couldn't turn the damn thing off.  I started to have disturbing thoughts about the fact that I'm listening to "inferior" electronics when compared to our Zen Triodes, yet somehow this was sounding incredible.

Towards the end of the night, still listening to the radio in mono cranked to the wood on great jazz and enjoying it as much as stereo I had a good idea.  I decided no one would believe this if we told them, so I was going to get some proof.  All I had to do was go over to the computer by the mixer and start the recorder.  I used the two boundary mics also known as room mics (CROWN PZM) fed into the board in stereo.  

The songs kept coming and I recorded 4 of them.  Then we took a break and I just had to hear what the recording sounded like so I hit play.  Now, here we were sitting in the same room listening to a recording of the Imperial - ON the Imperial.  It was playing a recording of itself.  That was interesting.  There was a noticeable difference in the sound of the recording.  It was less detailed and less tight and slightly smoother sounding.  But considering we recorded the room and the speaker was 90 degrees off axis to the mics this effect is normal.

I have saved the recordings because I think you'll want to hear this.  Even though a conventional stereo will never be able to fully recreate it, you will get a taste of it, perhaps 50% which is enough to hear what is so special about it.

I'll post a link to a 30 second clip of song 2.  It is about 2.5 meg in size.  The whole song is 43 meg, and I'm trying to figure out what is the best way to present it.

I can't believe it, I gotta hear the full song.  I have never heard 15" woofers produce such treble before.  What are those crappy woofers you dug up, you might be disappointed in the ones your ordered.  Which you haven't told us what drivers they are yet!!  One thing I have learned is not to under estimate vintage drivers, and pro drivers, they can do more than we imagine.

Cool suff keep it comming!  I think I might just have to make a pair of these, when will the plans be available?  But it have to wait until I get done with another project.

TG

P.S. Looks like someone else has a Shopsmith.

Ok now wouldn't it be wild if when you put in the "correct" speakers that you lost all the magic! I know you guys have thought about that

No way! That wonderful High End was your buddy with the shakers, right?  :o

Yes, Paul and I had this exact conversation.  I personally expect to like the miss-matched pair better.  We plan to install the fresh woofers in the second cabinet and compare once they come in.  To keep costs down I'm going to be using some no-name woofers from China.  They might be a flop, if there are you will all know about it --- as the Imperial turns.

Like I told Paul, don't laugh, we may have to find another pair of miss-matched woofers that match these!

I agree, you all need to hear the entire song.  I will post the 43 meg file on the site soon.  I will also remove it shortly afterwards.  Perhaps a few days.  Those without high speed Internet could possibly do an all night download while they sleep.

I thought many of you would find the highs interesting... we did!  Hell, why don't you all drive or fly over here and we'll roast a pig on the wood stove and have another go at it!

I'll be honest here for a minute... what is really sick is the fact that a single cabinet playing in mono with a poor source, crappie wire, and so so solid state amp can be as rewarding to listen to as the high end gear in stereo.  And in many ways it goes well beyond it.  At least that is what went through my mind at least 40 times on Thursday night

Of course the main course still awaits.  A finished pair set up properly being run by Zen amps.

I posted this a while back, it is all about tone.  The only reason for trying to get a stereo set up correctly put together is to get the right tone.  Phase coherency is just one aspect of that.  What you are saying is not surprising to me in the least, we have been so misguided by manufactures.  In the realm of speakers, one thing has proven true, BIGGER IS BETTER.  I have got to make a pair of these speaker for my garage.  No matter how nice I make them look, I don't know if my wife will let them in the house, but I will try.  Perhaps when she is seventy and doesn't care any more I could hire a moving company to move them in the house then, but I gotta have a pair now.

I think those china cheapies might just work fine, but you have got to try a few different speakers in them to help us understand what will work and what will not.  I find pro-drivers and vintage speaker drivers to be more forgiving of enclosers.  I mean in the scale of 12  cubic feet, what is one foot here or there.

I guess Steve doesn't have to worry about WAF when his business is audio, you just go to work and enjoy.

TG

Wel that just proves, there's no substitute for a big a-s-s pair of speakers. I listened to the WAV file, and it sounded pretty good, but that's because I've got my WebTV box hooked into my home theater/surround rig.

Why do I bring this up? Well, my processor has five LEDs that glow with varying brightness to indicate the relative strength of the signal going to each channel. And even the TWO channel recording Steve made does have some embedded ambient/surround information.

When the recording started, it was like being transported into the room that the big ol' Imperial was playing in. I even played the thing a few times through, just to confirm it wasn't a mistaken impression. It was like I was in the room with the speaker. If any of you decide to burn a CD, try listening to it in a surround rig, preferably in a matrix mode with NO room simulations. You may be suprised.

C'mon now Steve let's have some plans and I will develope a 3D solid model of them on the computer; it would be a nice evening project. Oh if it was just as easy to build cabinets in real life as it is on the computer!

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

Those things look efficient enough to be driven by anything, even a headphone amp. 8)
Dave

JLM,

In the original design filling the voids with foam would have really helped things.  This new version has no voids except in one spot.  It is cleated in five places.  Time will tell.

I will publish the new plans once I feel we are done with these cabinets and happy with the results.  Sounds like a pair built into your walls would be interesting!

Can these be driven by a Select?  I can think of no better speaker.  

Terry,

I've ordered some 2 inch compression drivers by Selenium for the horn lenses.  The drivers have an fs of 400 Hz.  The lenses should easily reach 500 Hz if I wanted to go that low. I plan to work on them sometime this week once the drivers arrive.

Steve

Here is the complete song from which the clip was taken.  It is 46 meg.

https://www.decware.com/imperial1.wav

This should be interesting!

Cheers,

Steve

Steve, I dont' mind since I'm on Broadband anyway, but mightn't it be more convenient (and less costly in terms of bandwidth) to zip the file or compress with some lossless audio packer?

I can't play it with Windows Media Player or Real Player..oh well...

I think the file's corrupt, media player et al don't like it, I was able to put it into cooledit though.  Perhaps you need to burn it to CD or open it with a program that doesn't require it all in memory at once?

I had a play with it, it does sound amazing, there's basically nothing in the registers abouve 16,000 Hz except a band of noise between 18KHz and 20KHz which probably comes from the recording media.  I did a high-pass filter at 14KHz and it still makes very little difference to the sweet ride cymbal.  This is what we'd expect from a pair of 15" drivers, I suppose, but it just goes to show that timbre and voluminous bass can make such a huge difference.   I was surprised to note that there seems to be a stereo image, Bass is where it should be... along the bottom.  The sax is somewhere right of centre and the ride cymbal seems to be off to the left.  Very odd.

The spectral analysis shows the track to be absolutely saturated with below 100hz.  Who needs subwoofers!?  That's rib-crushing bass I suspect the real thing sounded more tight than the recording, and it especially suits that music, but I was also surprised to hear the quality of the announcer's voice, too.

I think this beast is going to sound amazing with the top end drivers in.

For those of you who couldn't hear the file, I took the liberty of putting a high-quality mp3 up here.  I don't want to damage anyone's self-calibrating hearing  :P but it's super-high quality variable bitrate and to me sounds easily as good as the original.  It's the bandwith I'm more worried about

PS - I'd love to hear those beauties belt out some piano when they've got their top bits in.  Even without, I bet they sound about as close to the real thing as you can get.

erratum: high-pass should read low-pass.

That is what my computer keeps saying that the file is corupt.  Thanks for the mp3 file Peter, I was able to play that, although I don't know if I want to waist a CD for it though I haven't decided.

This is what I think, the shakers, high hat, cymbles, and tamborine, were all being played by Steve and company.  The rest was comming from the Imperials, even at that the imperials sounded great.  You can not beat high efficiency drivers.  I of course on my computer did not get the sense of huge bass, but the rest of the tonal quality was great.  I suspect these speakers will be much happier with vintage high efficient woofers such as Electro-Voice (that would be my first choice), and Altec drivers.  I also would think many modern pro and high efficient drivers would sound great as well, but just not quiet as tonally balance as the vintage drivers, much like the ones Steve has in their now.  In fact the on driver looks like an EV driver.  Steve can you tell us the mismatched pair you have in their now.  I also think having a mismatched pair would have some advantages, as you could get a little better tonal balance.   Both are feeding the same horn, but are separated by their own enclosers aren't they?

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.

TG

If you haven't got studio speakers or good headphones with a suitable soundcard or audio interface on your computer, I highly recommend burning a CD.  It's difficult to appreciate the sheer depth of the recording.  -- and these day's a blank CD sells for less than 50c.

The cymbals sound like they're in the room, it's true, but I'm 99% sure they're part of the original recording.

The voice at the end's a dead giveaway, all the S's and T's are clear as a bell.

To be honest, I don't think so.  (addendum: I mean I think you will get all that, I don't think you'll lose the imaging ) 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.  What I will say, though, is that the mp3 is recorded at a very high variable bitrate.  i.e. when not needed, the bitrate is low for better compression, when needed, the bitrate goes up to 240bps, which is easily high enough for 'cd quality' recordings and way higher than most anything you'll find on the internet.

On my studio sound module and fairly good sony headphones I couldn't tell the difference and was satisfied with the quality and the imaging (inside my head), or I wouldn't have posted it.

After all, what the original file contained was a noisy recording done (I'm assuming) on PA kit, of FM radio played through mismatched 'cheapo' 15" drivers with no tweeter.   Blank between 16-18Khz and full of recording noise between 18-20Khz.  I even left the recording noise in!  Believe me, mp3 or original, you don't lose the jaw-dropping disbelief in what you're hearing.