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To say the least, the anticipation is building ... (Read 54121 times)
60ndown
Ex Member



Re: To say the least, the anticipation is building
Reply #15 - 02/09/06 at 15:15:17
 
i would wait till steve releases the ACTUAL plans for the so imp. it would be a p.i.t.a. to cut a sexy enclosure to pieces because of a small overlooked placement of ply? anyone who is anyone knows the importance of patience?
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gexter
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Re: To say the least, the anticipation is building
Reply #16 - 02/09/06 at 16:55:25
 
Have to agree with 60.

thats also an awful large amount of wood and time to end up it not working the way it should.
why risk it?

Thats the major reason I would build a std Imperial sub right now without the exact Imp SO plans
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bassboy
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Re: To say the least, the anticipation is building
Reply #17 - 02/09/06 at 17:09:17
 
Boydon - my comments are based on my own experience with my imperial, which is similar but still quite different than the SO.  In case you didn't see my post in dank's thread here is a brief description.

Mine was originally built from 1956 plans but modified to make construction much easier, built mainly of SOLID 2" doors with no bracing anywhere, although even with the huge panels it might still help.  All internal dimensions are kept exactly to original specs.  

Not happy with frequency response, I did a lot of research and decided, as Steve did, to change the design to front loaded.  All I did to change it was move the driver panel back to close the internal compression chamber and cover the front.

2 10's use the 8 or 9 foot chamber in an infinite baffle situation, as they call for a sealed box of only 1.3 cubes each.  This REDUCES the sensitivity of the drivers from a rated 94 by probably 3 db less.  It does, however, promote low frequency extension and response is still pretty even.

I do not utilize any type of slot in the front, making my design very similar to most commercial units.  

The amp I use is solid state garbage, 200 watts total peak.  I have never used more than 100 watts peak, and at this volume it is very unpleasant as the room vibrations cause more noise than the bass.  You can actually feel the concrete floor vibrating.

It has been my experience that speaker placement in the room is more important than driver selection, compression chamber size, materials used to make the box, etc.  Especially in an untreated room.  In my opinion, the only thing as important is keeping the horn flare as close as possible to a proven design.

All those factors are certainly important but...

I have tried both a front and a back loaded imperial with different combinations of 2x10", 2x8", 4x8".  The speakers had wildly different specs but the frequency response for each combo was ALMOST EXACTLY THE SAME, all combos rolling off steeply below 40.  (I like 2x10" front loaded the best.)

Those are the results directly in front of the horn mouth.  Coupling to the room provides dramatically different results in which moving the speaker just a few inches completely changes the frequency response in different parts of the room.  The best spot to date for even frequency response and low frequency extension has been with the mouth very close to the corner walls.

All that is a long way of saying no, it is not exactly an imperial SO, no, I am not using a 4 watt amp.  But in my untreated room, with the mouth so close to the wall 4 watts is about the max before the room starts shaking and reducing sound quality.  

A 20hz note at 10 watts total peak does not sound loud at all but rattles the room and especially the wall it fires into like you would not believe.  Not enough to shake the drywall free of the screws but definitely enough to crumble old dry plaster.
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Caintuck Randy
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Re: To say the least, the anticipation is building
Reply #18 - 02/09/06 at 17:29:20
 
[quote author=60ndown  link=1139429263/15#15 date=1139498117]i would wait till steve releases the ACTUAL plans for the so imp. it would be a p.i.t.a. to cut a sexy enclosure to pieces because of a small overlooked placement of ply? anyone who is anyone knows the importance of patience? [/quote]

Howdy 60,

I talked to Steve and he said that the plan as it sits will work just fine.  I also have some photos that Zygi took as he was building Tim's (change_out's) pair of SO Imperials and according to Zygi and Tim they work VERY well ..... Smiley

My builder has gone over the plans and photos with a fine tooth comb and is making ACAD drawings for the build.  He works in ACAD all day long and says that the plans and photos make perfect sense to him ..... but he will probably be calling Steve or Zygi to clarify a minor detail or two, as Zygi made a couple of small changes to the original when he built Tim's.

No worries ..... but I appreciate your concerns .....

Randy
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« Last Edit: 02/09/06 at 17:40:28 by Randy in Caintuck »  
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change_out
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Re: To say the least, the anticipation is building
Reply #19 - 02/09/06 at 20:04:01
 
Howdy,

Mine work very well indeed. With 1.6 watts / channel you will move "big air". With a 500 watt Bryston I have seen the Parkers deflect ( rock from side to side ) by as much as 1/16-1/8 inch. I did not keep the spl at that pressure long! No dry wall dammage was incured.

If one has not heard the Imperial as it was at the fest, I don't consider myself articulate enough to describe it. I am sure the speaker can output pressure capable of damage to the structure in which they are housed, as much so to the listeners ears.

What ever the risk of damage may be -- it IS managable and should not present an issue with the prudent audiophile. All that said I would not trade the Imperials.Period. This is a great thread!

Tim



   
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« Last Edit: 02/09/06 at 20:04:51 by change_out »  
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gexter
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Re: To say the least, the anticipation is building
Reply #20 - 02/09/06 at 20:20:01
 
As soon as I can verify the numbers it goes to draft mode and full scale drawings.

Change_out and Randy your my heros

1.6 watts for nice bass fill, looks like Steve is right on the money...again....

Are you using the Daytons or another driver? the dayton 295-130  ST385-8 15" series II woofer was mentioned
Fs 19
Qts .34
Is that what you went with?

Gex
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Caintuck Randy
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Re: To say the least, the anticipation is building
Reply #21 - 02/09/06 at 20:32:39
 
Howdy Gex,

We are both using the Dayton drivers ..... Grin

Take care,

Randy
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boydon_lepasci
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Re: To say the least, the anticipation is building
Reply #22 - 02/10/06 at 01:45:22
 
Randy, bassboy and everybody else,

I'm with you all the way on horn designs. I think they're the only way to go if you can get your hands on quality low-power amps. I'm an efficiency freak so I like horns even with the SS amps in my budget. I even run to the "if more is better then too much is just right" side of things when it comes to SPL or HP. Not at the expense of SQ though.

bassboy, I caught your background in the other post after my question on this one. Have you read the Harman paper on sub placement? I think they only tried monopole subs for the entire test and your results seem to indicate a lack of corellation(sp?) for horns. Anybody up for another thread?
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bassboy
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Re: To say the least, the anticipation is building
Reply #23 - 02/10/06 at 04:06:44
 
Boydon - I have not seen any info on sub placement and any info you have would be a great topic for a new thread.  

Tim, please tell me what kind of frequency response you are getting, in particular, where low frequency starts to roll off.  I have guessed 40 is as low as it is likely to go with -3db at about 35.  I would love to be proven wrong, I would definitely buy new, lower fs subs.  As far as I know you may have the only pro-built SO's so I'm sure everyone would like to know.

I'll also be waiting for Randy's answer to the same question.  How long is that going to take, anyway?  Anyone else measured imperial output?
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Caintuck Randy
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Re: To say the least, the anticipation is building
Reply #24 - 02/10/06 at 14:10:35
 
[quote author=bassboy  link=1139429263/15#23 date=1139544404]

I'll also be waiting for Randy's answer to the same question.  How long is that going to take, anyway?  Anyone else measured imperial output? [/quote]

As I mentioned to Tim in another thread, the friend who is building my Imperials is a "weekend warrior" when it comes to his woodworking ..... because he has a real job and a family to consider.  But, I have seen his work and he has a really nice wood shop.  He is also a detail freak and a perfectionist.

He's finishing up another project that should be done soon and estimates that the Imperials will be ready in four to five weeks ... I probably should have named this thread "The anticipation is killing me" ..... ???

Randy
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« Last Edit: 02/10/06 at 14:10:59 by Randy in Caintuck »  
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Steve Deckert
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If the 1st watt
sucks why continue?

Posts: 2366
Re: To say the least, the anticipation is building
Reply #25 - 02/10/06 at 15:53:23
 
[quote author=J_Rock  link=1139429263/0#14 date=1139465014]EXCELLENT THREAD!



Have you actually tried killing mice with Dynamite?  Cause if you haven't I suggest you do at least once!

Cheesy

But in all seriousness, I am going to have to demand this thread be kept alive forever. [/quote]


That just reminded me of one of my first imperial experiences.  I had a pair in a single car garage (door open) with a large crack in the concrete floor (can't remember how that happened) and after doing some high SPL tests of low frequencies, Paul and I got to watch a mouse crawl up out of the crack - stagger around and die only a few inches from where he appeared.  We knew exactly what killed him.

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Steve Deckert
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Re: To say the least, the anticipation is building
Reply #26 - 02/10/06 at 16:02:53
 
[quote author=bassboy  link=1139429263/15#23 date=1139544404]Boydon - I have not seen any info on sub placement and any info you have would be a great topic for a new thread.  

Tim, please tell me what kind of frequency response you are getting, in particular, where low frequency starts to roll off.  I have guessed 40 is as low as it is likely to go with -3db at about 35.  I would love to be proven wrong, I would definitely buy new, lower fs subs.  As far as I know you may have the only pro-built SO's so I'm sure everyone would like to know.

I'll also be waiting for Randy's answer to the same question.  How long is that going to take, anyway?  Anyone else measured imperial output? [/quote]


At the fest, I did a sine wave sweep on the Imperial SO's so that those who attended could hear a true 20 cycle note.  There was no attenuation as the frequency dropped from 100 to 20Hz.

Also, a note about the plans linked to earlier in this thread.  The color picture posted is low res to prevent people from accurately building a pair.  I have a very high resolution grey scale image of the same thing that I have been e-mailing to those persons wanting to build a pair.  I remember sending one to Randy, but that doesn't mean he got it.  Make sure Randy that you have the right plans.


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bassboy
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Re: To say the least, the anticipation is building
Reply #27 - 02/10/06 at 16:20:01
 
That's the word from the man himself, I obviously need new, lower fs subs.
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Steve Deckert
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Re: To say the least, the anticipation is building
Reply #28 - 02/10/06 at 16:28:06
 
Recalling the incident with the mouse I started remembering all kinds of fun things that happened during my first couple years with Imperials out in that garage.  Paul and I tried every 15 inch driver we could get our hands on for about a year.  Then the crazy stuff began.  At one point we had two 15 inch drivers compounded and horizontally loaded inside the imperial by using the dead air space in the original 1956 design as a sealed box.  Then we reinstalled a 3rd 15 inch driver in the front.  This was the tightest bass we ever got out of them, I remember it was like being hit by a 2x4.  The best combination I ever came up with was taking a 1 cubic foot sealed cube, placing a 12 inch woofer in it.  Measured response in cube was -3dB at 120Hz.  It had no bass.  Then I screwed a 24 x 24 inch board to the back of the cube and installed the cube face first into the 15 inch opening of the Imperial.  The 24x24 inch board held the cube in place and sealed the opening where the 15 inch driver typically goes.  This turned it into the worlds biggest bandpass box and with the SPL meter set at 100dB at 100Hz it hit 124dB at 28.5Hz.  That btw, is one fricking serious bass note that you bones remember for a long time until the inflamation goes down.  Poor mouse...

One of my favorite things to do was stand out there in that garage and do the low frequency sweep - real slow.  I could make it sound and feel like a helicopter was landing on the roof.  Dave, who lived one block away (353 yards by straight line distance) has a beer stein collection that I could make rattle by doing these sweeps.  I figured out a radius from his house to the garage and estimate this effected about 20 houses nearby.

I liked and still do for some reason to call it "wazoo"ing the imperials.  I'm certain this addiction was irritating to people because once around 2:30 P.M.  I saw a guy running across the road about 2 houses down in his P.J.'s trying to find the little bastard who was making all this noise every day.  I guess he worked 3rd shift.
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Steve Deckert
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If the 1st watt
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Re: To say the least, the anticipation is building
Reply #29 - 02/10/06 at 16:43:41
 
And of course thinking about the 12 inch cube trick, we had a local night club call us (we did pro sound at the time) because word got out about the imperials as I started installing them around town.  They had 4 18" subs with 1600 watts driving them and basically had no bass.  The company that designed and installed them blamed it on standing waves and claimed no more bass was possible in the club.  I didn't really like this particular club owner too much so when he called I told him yea, I can make bass in your club hit so low that things could become damaged.  He didn't believe me, so Paul and I heaved the imperial in the truck and drove down there with it.  It still had the 12 inch cube inside.  To power it I took my frequency generator and a harmon kardon 80 watt receiver with one blown channel.  We trucked the cabinet into the club and I did a super slow motion wazoo starting at 150Hz.  When I hit 50 Hz the bass was about the same as what he had before with the 18's.  I paused there and said, well - what do you think of that?  I just had to mess with him.  The wazoo slowly continued down and as predicted, at 28.5Hz I had stopped an entire night club, some 100 people from talking, and most had gotten up from their tables to stand at attention.  Everyone became very uneasy because they had no idea what we were doing, or that we were even there.  The ash trays on some of the tables - no really it was all of the tables - started moving around on the table tops.  I asked the guy if he would agree that this is bass - he did.  Then we turned it off and trucked it right back out the door and left.  A month later we had a contract to design and replace the entire system.
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