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Imperial SO has problems, need help (Read 59067 times)
gexter
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Re: Imperial SO has problems, need help
Reply #51 - 02/04/06 at 16:01:41
 
Nice, really nice.
looks alot better than cardboard Smiley

best of luck.
   Gex
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Zygi
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Re: Imperial SO has problems, need help
Reply #52 - 02/05/06 at 00:23:43
 
Dan,

  what I thought I saw that was bothering me is not what I'm seeing now. I will send you the pictures that I think is where I'm seeing differences, with my limited knowledge of horns or just common sense is telling me something.

    Hopefully we can figure this out and make everyone happier because we did.

     BobZ
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dank
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Re: Imperial SO has problems, need help
Reply #53 - 02/05/06 at 12:08:15
 
I have 3 more graphs that may shed light.  The graphs go from 20 hz to 20khz, keep in mind that we are really only interested in the 20 - 200 hz range.  Also disregard the blue line, all the information is in the green line.  I think I'll admit that the steep ramp up (looks like about 24 db per octave) is due to the poor speaker choice for this application, but the responce from 70 to 200 hz is what seems to have a very serious problem, and I'd sure like to know what it is.  The 3 graphs are 1)  front panel removed - this should act just like a speaker in a 5 cubic foot sealed box not coupled to the horn at all.  2)  with front panel - normal Imperial SO.  3)  with a solid board covering up the front panel so all the speaker energy goes into the horn.

http://www.mninter.net/~kuechle/open_ft.jpg

http://www.mninter.net/~kuechle/slot_ft.jpg

http://www.mninter.net/~kuechle/solid_ft.jpg

Dank



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bassboy
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Re: Imperial SO has problems, need help
Reply #54 - 02/08/06 at 21:20:18
 
Here's my two cents.  I didn't bother to look at any of your pictures or graphs because it's not really necessary.  (And I have a dial up connection)  The design of this subwoofer is solid.  As far as I can tell it appears to be in the area of a 35-38 hertz horn with a flare inspired by the tractrix contour.  I have done a lot of research and this is a great design.  I am assuming that you did a good job building it.  I am assuming it is absolutely airtight where it should be.  Assuming these things there are only three varibles left - the driver, the hole in the front and room position.  

The hole in the front of the driver is NOT NECESSARY.  If it is doing what it is supposed to do, great, by all means it improves on the overall design.  If not, and it obviously isn't helping you, cover it up.  It won't hurt anything and you can rest assured that is how it is usually done anyway.

I would try a smaller driver, or one with a smaller vas.  Or restore the chamber to original size.  It's not going to hurt anything and you really don't need to try to max out this box, trust me.

That leaves the room position.  Consider this - I spent about 20 hours making my Imperial from the 1956 plans.  I spent about 5 hours modifying it to make it a front loaded design, similar to yours, and many other horn plans available on the internet.  (Without the slot, of course, simple as possible works well for me.)  I have spent over 60 hours listening to this thing and adjusting it's position.  It's still not perfect, but here is what I found.  

My garage has no treatments and it is about 30x30 with a 12 foot ceiling.  Backed into the corner it sounded great but low frequency extension was painfully inadequate.  I found, as you did earlier that it was a whole lot louder when facing into the corner.  Better lf extention as well, but at about three feet out the response was very jagged.  At high power levels (100 watts) the fluorescent lighting, the garage door and garage door opener, the electric panel and anything leaning on any wall would vibrate almost as loud as the bass.  You could even feel the concrete floor vibrating.

Moving it closer to the corner helped a lot but even a couple of inches in any direction made a huge difference in frequency response and lf extension.  Still not happy with this arrangement, I remembered the Big Fun Horn project and how much I was fascinated that in this design, the box itself actually cuts the corner in half.  So I turned the box so the SIDE was facing into the corner, tight to the walls.  Huge improvement, with less power it was louder and lower.  Angling it in even further helped, until the mouth was only about a foot from the wall on one side, tight to the wall on the other.  Placing a 100 lb slab of door on top, closing it off to the ceiling and further preserving directionality seemed to help too.  It looks oddly like the corner horn design, also on this website, but with a mouth on only one side.

This placement yeilded highest SPL, even frequency response, and oddly enough, the least room vibration noise.  In fact, leaning on the drywall near the mouth listening to a 20 hz note at 10 watts feels like a vibrating bed and makes it difficult to breathe.

That being said, the response is still pretty erratic as you move through the room, but if it's a listening room, you only have to pick one good spot anyway.  Room treatments would probably do miracles as well.  But don't try to get flat response below about 40, mine drops off pretty fast below that.  I have 2 10's in an infinite baffle situation, using the full box size available in there.  You guys can question this if you like but I think the horn flare, not the sealed chamber OR the driver is going to determine your low cutoff.  Of course they will have some effect on the overall outcome but I don't think you will get much lower than 40 flat unless you use room placement and room characteristics to effectively extend the horn or at least preserve directionality as long as possible, which I suppose is kind of the same thing.

But probably the easiest thing to try is actually turning it down.  Try going from 0 to 10 slowly and this is what I found.  Up to about 3 watts total peak, everything sounds great, and you can actually FEEL the SPL like an invisible vice around your head.  At about five watts it sounds louder but a lot sloppier and the pressurization effect is gone.  Some of the extra noise is the room rattling and most of the power is used shaking the hell out of the drywall.  Unless you are in a big nightclub, you really don't need more than 10 watts to lose your hearing.

By the way, if you want to take a meaningful measurement, do it right in front of the horn mouth, before the room gets ahold of it.  That's the only way to tell what's truly there before room effects add and subract.

Good luck
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Zygi
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Re: Imperial SO has problems, need help
Reply #55 - 02/10/06 at 18:19:35
 
Bassboy,
 

   Can you explain this..... The hole in the front of the driver is NOT NECESSARY.

    BobZ
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bassboy
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Re: Imperial SO has problems, need help
Reply #56 - 02/10/06 at 18:51:54
 
What I am referring to is the K-slot in front of the driver.  If I understand correctly, Steve explained that it's main purpose was to prevent high frequencies from entering the horn.

This was historically done by tuning the chamber in front of the driver, but since this design employs no front chamber high frequency cutoff would mainly be determined by the horn bends.  

If Steve's design does what it is supposed to do, it is a major update to horn theory, as this field has not advanced much in a few decades.

However, if for any reason it is not doing what it is supposed to I do not see any reason why it should not be covered.  This will necessitate the use of some form of crossover, but actively filtering the input to the operating range of the speaker should help any design, SO included, so I would use an active crossover anyway.

I have an imperial very close to SO design with no slot and it works very well with an active crossover.  The WO32 is very similar in concept if not scale, and works well with no slot, as do countless other similar designs readily available.

Humbly stated, I have been proven very wrong this very morning in my assumptions regarding theory, so please correct me if I am mistaken in any way.
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Zygi
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Re: Imperial SO has problems, need help
Reply #57 - 02/13/06 at 18:54:30
 
Bassboy,

  Not trying to prove anyone wrong here, that would be wrong, this forum is a learning tool for a lot of people.  It really helps the DIY'er which is great for the IMP/SO due to size and shipping costs.

 I'm just not much of a fan of someone making blanket statments about a design unless they have good reason for making such statements.  Just thought I'd keep your ideas in check a bit, thats all. Nice response by the way...


  I looked at Dans pictures and saw something that didn't look right, after building a set for Tim, and countless calls to Steve I may have a handle on building them correctly, but this in no way makes me and expert on the Imperial or any horn for that matter.

  My thoughts are, if the IMP is a 40 hrts horn covering up the K slot will make it just a 40 hrts horn. While it is the same idea as the WO-32 and that sure doesn't have a horn large enough to go very low, it works.

  I think theres two things at play here,  the begining of the horn is the narrowest section at the top of the k slot, and the k slot builds a high preasure area which feeds the horn itself. I think that is why a low FS driver is used which works well in a 4.5-5 cf box. The lower FS driver will continue below the horn cut-off as well as gain from the room making the SO IMP almost flat to the lowest octive yet it still remains as effortless sounding as any sub I've ever heard.  I could be way off here, however.  All I know, built correctly, it works.

  What we all got to hear at Decfest was a treat, which is why a few people with the space are building the SO's for there rooms, I will have a pair of SO's its just a matter of time till I have a new listening room which will accommodate these beasts.

  The biggest problems with a lot of people building speakers of any sort from plans or kits, is they don't take the time to build it  exactly to the plans specs. They  sometimes take artistic libertys with the design and then complain the speakers sucks.

 Dan didn't take liberties with the design, he had only a sketch, which Steve drew for him at Decfest to work from. Now we just need to help Dan get his SO/IMPS working as they should.


     BobZ
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bassboy
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Re: Imperial SO has problems, need help
Reply #58 - 02/13/06 at 20:39:51
 
Thank you for your reply.  Your response indicates that the the slot is not just to filter high frequency response, as I had assumed based on Steve's description, it actually has a complex relationship with the throat itself.  That changes things a bit.

As I have said before, this design is certainly revolutionary.  And since I don't have one, and have never heard one, I am guessing at best, based on papers on horn theory.  As you can probably imagine, I have never seen a paper concerning this type of slot or using the brute force of low fs to overcome limitations of the horn.

When I mentioned I had not seen the pics of dank's imperial, I did not mean to imply that rigid conformity to the plans doesn't matter, I assumed since he has seen it he did it exactly perfectly, or reasonably so.

I checked out the dayton driver series II.  The thing is only $89 on parts express, or whatever website I was looking at.  In light of this, it would be silly not to use the specified driver.

That would eliminate driver and box as the source of the problem.  (If the slot is confirmed to be the exact correct size and geometry.)

Then it would have to be perfect, wouldn't it?

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Zygi
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Re: Imperial SO has problems, need help
Reply #59 - 02/13/06 at 23:06:02
 
Bassboy,

   If you want to see something that turns theory upside down, look at Steve's Cornerhorns. The man doesn't know what it means to think inside the box.

     BobZ
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dank
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Re: Imperial SO has problems, need help
Reply #60 - 02/20/06 at 15:58:44
 
Well, I broke down and bought the Dayton 295-130 for my Imperial SO.  I installed it this past weekend, and everyone who was betting on the problem being the speaker just lost their shirts!  The new speaker makes little or no difference.  It is still performing reasonable well with the front boarded up, but down right pathetic when in it's intended configuration.  An SPL meter right in the horn reads an average of over 18 db lower across the entire range of 30-100 hz (measured at 8 points) when the SO is "normal" vs boarded up.  The only other thing I can think of is that I don't have the football shape cutout in the front panel yet, but Steve's worked well enough without that at Decfeast 2005 so I'm not sure that will make that hugh a difference.  I'm about ready to hang this one up, maybe I'll plan on throwing it in the truck and take it to DecFest 2006 unless someone can come up with something else to try.

Dank
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60ndown
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Re: Imperial SO has problems, need help
Reply #61 - 02/20/06 at 16:50:08
 
return new drivers and get you money back, dont give up 5 seconds before the miracle. ??? they will give you what you want we are just missing something. i dont read long posts (too a.d.d.) but could you list your signal chain EXACTLY.and how its all connected.my guess is that there is soething wrong with one of your components.

have you tried
just 1 imp?
on both channels?
on a different amp?
different x over?
no x over?
different source? maybe your source just doesnt produce any output below 80hz for some reason?



1.source
2.x over
3.amp
4.etc
5etc
6.etc
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Steve Deckert
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If the 1st watt
sucks why continue?

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Re: Imperial SO has problems, need help
Reply #62 - 02/20/06 at 21:39:44
 

Dank,

My SO's that were at Decfest 05 had the football shaped cutout.  From looking at your original pictures the obvious thing I saw was the spacing between the baffle and the front panel followed by other small details that were all just a bit off.  I e-mailed you a high res image of the plans so you could compare them to yours and see if anything could be easily adjusted closer to spec.  That was months ago.  Did you ever get it, and if not, would that help?

Also, on mine, installing a solid front baffle without the cutouts has almost the opposite effect in that it kills efficiency of the low bass.  What you have now is probably close to a giant sized WO32 cabinet where the horn flare shrinks to a point with minimal air space in front of the woofer.
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dank
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Re: Imperial SO has problems, need help
Reply #63 - 02/21/06 at 12:22:29
 
Steve

Yes, I got the drawing and mine is close.  I got a little confused as to the front removable baffle though.  Mine is currently only single thickness, and some pictures from Zygi just had the inner cutout (with the football shape) so I incorrectly assumed the front panel had changed.  I will add a second sheet of plywood to mine (with the football shape) and see what happens.  

If I'm reading the plans right though, the main important thing is that the front of the compression chamber angles from 0 to 2.5" away from the inner side of the front removable baffle board and that the top of the compression chamber angles from 2.5" to 3.75 inches away from the inside of the top.  My cabinet is quite close to these dimensions.

DanK
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gexter
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Re: Imperial SO has problems, need help
Reply #64 - 03/15/06 at 01:46:02
 
Dank

I gotta know, did you get things worked out?
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serenechaos
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Re: Imperial SO has problems, need help
Reply #65 - 03/23/07 at 14:31:07
 
gexter wrote on 03/15/06 at 01:46:02:
Dank

I gotta know, did you get things worked out?

Still curious...
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dank
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pair of dual 18
Imperials

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Re: Imperial SO has problems, need help
Reply #66 - 03/23/07 at 23:31:50
 
I gave up on this quite some time ago.  I have no idea what's wrong.  My interests have shifted, so I'm working on other things, and the SO is just sitting in the storage room (along with my pair of dual 18 Imperials).  It has to be almost perfect cancellation between the front wave of the speaker and the wave out of the horn.  It's still VERY impressive if you board up the front and send all the energy into the horn, so I know the speaker and the amp are all working fine.  That gives me an idea...if that scenario is true I should see increased output if I board up the horn mouth instead of  the front...maybe I'll try that this weekend.  But the way things have been going lately, I'll just generate more questions...that seems to be my motto lately:  looking for answers,  finding only questions.


Dan K
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JRock
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Re: Imperial SO has problems, need help
Reply #67 - 03/26/07 at 06:01:08
 
I re-read this entire thread again and am still entirely mistified.  I was certain it was the driver- but it obviously isn't.

DanK- I plan on building a pair of Imperials this summer- and I would love to talk with you a little more about what drivers you have tried and whats worked in the normal Imperial.

I also have a new big PA amp if you decide you want to send some serious wattage to your imperials- I remember them having some huge Cerwin Vegas in them.

In any case- what are your new projects?  Anything you would like to share?
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60_and_up
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Re: Imperial SO has problems, need help
Reply #68 - 03/09/08 at 02:16:19
 
any updates?

where are these beasts?


dank wrote on 03/23/07 at 23:31:50:
I gave up on this quite some time ago.  I have no idea what's wrong.  My interests have shifted, so I'm working on other things, and the SO is just sitting in the storage room (along with my pair of dual 18 Imperials).  It has to be almost perfect cancellation between the front wave of the speaker and the wave out of the horn.  It's still VERY impressive if you board up the front and send all the energy into the horn, so I know the speaker and the amp are all working fine.  That gives me an idea...if that scenario is true I should see increased output if I board up the horn mouth instead of  the front...maybe I'll try that this weekend.  But the way things have been going lately, I'll just generate more questions...that seems to be my motto lately:  looking for answers,  finding only questions.


Dan K

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dank
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pair of dual 18
Imperials

Posts: 418
Re: Imperial SO has problems, need help
Reply #69 - 03/11/08 at 16:12:30
 
60_and_up wrote on 03/09/08 at 02:16:19:
any updates?

where are these beasts?





Some of you might enjoy the following pictures, others may not.  Warning - the following pictures are very graphic in nature, parental control is advised!















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musgofasa
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Where is that
monkey? I want to
shoot something!

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Re: Imperial SO has problems, need help
Reply #70 - 03/11/08 at 17:57:35
 
 :'(           :'(
Cry           Cry
Cry           Cry
Cry           Cry
Cry           Cry
Cry           Cry
Cry           Cry
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The graveyard is full of important men
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60_and_up
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Re: Imperial SO has problems, need help
Reply #71 - 03/11/08 at 23:52:18
 
i hope steve or zyggi dont look at those and tell you what was wrong.

bottom line is, the imperials work, and steve wouldnt reccomend something if it wasnt great, you were so close..........

ive scrapped more than 1 box that i lovingly built

always a hard decision.....
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Ratchettune
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I have the SOLUTION accidentally
Reply #72 - 01/20/19 at 19:18:58
 
I made a profile so I could provide the solution!!! Only a decade too late...

I was so excited to get the imperial SO built. I had a friend cut everything out on a CNC router to inhuman perfection, pieced it all together and.... Wait for it... Nothing. I've built a Fitzmaurece tuba HT before and loooved it. The imperial was meant to be a subtle upgrade and more interesting to look at than a 3 foot cube.

I double checked all dimensions with the blueprints. All good. I tried the same thing as a few others and covered the K-slot with a noticable improvement but still nothing like I expected.

While the K-slot was covered I noticed I could feel air pushing past the front plate. I rememberd my saxaohone days. When even a single upstream pad is subtly leaking air, hitting those low notes is... Not possible.

So, I calked it up, opened the slot back up and WOW! After walking all over my room to find the node...( Haven't picked a perfect spot for the horn yet)... I have finally experienced the hype. Impressive, clean, and resonant bass at very low power levels.

tLDR;. The front plant is removable (don't glue it) but it must be air tight. I used clear waterproof calk which I can easily scrape off if I need to replace the driver later.

I should also note that I made a few mistakes with my CAD file. My K-slot is shifter 2 inches too far from the pinch point, and I guessed on the slot dimensions since I didn't know what it was, and (too excited to wait) I don't have the two small angle boards in the first too bends yet. I only say this to prove the resiliency of the horn. SOME mistakes can be made... Others cannot.
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Ratchettune
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Seems rediculous now.
Reply #73 - 01/20/19 at 20:00:49
 
Well, I found my favorite spot in the room. I turned it on it's side and faced the horn into the front left corner, pushed right up against the walls at 45°. Never in my life did I think 1 15" Dayton and 100 watts could do this to my ears.
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Brian
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Re: Imperial SO has problems, need help
Reply #74 - 08/11/19 at 05:06:44
 
It is so very good to hear that someone found the answer to this puzzle!

I read that you prefer them turned into the corner. Did you also like them directed out into the room? Is the difference a large one?

Brian
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