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Imperial SO has problems, need help (Read 35255 times)
Zygi
Ex Member



Re: Imperial SO has problems, need help
Reply #45 - 02/03/06 at 17:46:05
 
Dan,

  Sure, I remember everything about Decfest...... I'll try to e-mail you some pictures tonite, as you look them over you might spot something.

 I should get the pictures to Steve D. He might see something I did wrong, but Change-outs sounded great before they left here.

                BobZ
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change_out
Ex Member



Re: Imperial SO has problems, need help
Reply #46 - 02/03/06 at 22:08:23
 
Howdy Dank,

I remember you from the fest. I hope your problem will be quickly spotted by Zygi or Steve. Your Imperial cabinets look great.

Zygi,

I think the Imps are getting better wiyh age, I am only driving them with the select mono's. I expect a long break in on such a beast  using 1.6 watts per channel. Grin

Tim
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« Last Edit: 02/03/06 at 22:09:04 by change_out »  
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J_Rock
Ex Member



Re: Imperial SO has problems, need help
Reply #47 - 02/03/06 at 23:42:36
 
I could be completely wrong but my guess is the sealed chamber isn't allowing the subs to move air.  Too high of a compliance.  

I mean, if the driver can't produce reasonable output in the sealed chamber, theres no output for the horn to amplify...

I hope its something other than the subs though.

Perhaps Zigi could give us the name of the drivers in chnageouts, to see how they model in a sealed enclosure.  If they model as poorly as the JBL's do, they we could deduce that the sealed volume is not what is impeding the output.
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Zygi
Ex Member



Re: Imperial SO has problems, need help
Reply #48 - 02/04/06 at 00:23:47
 
J. Rock
     Dayton 295-130 are in Change_Out's IMP's
 
      BobZ.
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Zygi
Ex Member



Re: Imperial SO has problems, need help
Reply #49 - 02/04/06 at 00:27:45
 
Tim,

   I think you will experience a long break-in, but they will break -in.

        BobZ
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gexter
Ex Member



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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« Last Edit: 02/05/06 at 01:11:50 by gexter »  
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Zygi
Ex Member



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
Ex Member



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
Ex Member



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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« Last Edit: 02/08/06 at 21:50:45 by bassboy »  
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Zygi
Ex Member



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
Ex Member



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
Ex Member



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
Ex Member



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
Ex Member



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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