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Push Pull Slot Loaded quad SI HT18s

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#21 maxmercy

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Posted 10 August 2014 - 01:30 AM

I may be able to do something like that....I'm building 8 sealed boxes right now.  Hornresp could probably sim it with its newer capabilities.


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#22 MemX

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Posted 11 August 2014 - 12:52 PM

 

You are putting a little too much thought into the plate...Think about how a horn or bandpass system works. No laws of physics are broken. I am a bit surprised at a gain being shown over such a large bandwidth even if just 1dB or slightly less.

I think this is where my knowledge gap is evident :lol: I think I understand something about how the volume of the air inside a horn effectively acts as one and the mouth being larger than the driver itself therefore gives more output (unless I am completely wrong, which I fear I am...)

More reading required!!
 

 

I've been struggling with the 'velocity' thing.
 
I know it must be a simple matter to grasp since so many people refer to it so matter-of-fact-ly. The speed of sound is a constant and velocity is just another word for speed. So, how does the velocity (or speed) of sound increase?

Ditto those comments/thoughts.

Over the weekend I was pondering the assertions made elsewhere on this. Is it a case that the air being forced through a smaller slot makes it denser, therefore soundwaves travel faster through it? Does the restriction, effectively, 'couple' the air to the driver's cone?

I might stick a post up on DIYAudio as the confused n00b that I am :lol: lol


 

I had already been building up-firing (with a glass top plate) and down-firing sealed subs by then, but hadn't considered the distance from the top plate-to-driver or floor-to-driver. The following year, circa 2003, I built the 1st in a series of dual opposed, up/down-firing and it was then that I looked at the distance between driver and plate/floor.
 
There was some discussion about it at HTS regarding the distance between driver/floor when building a down-firing sonosub, and I seem to recall Seaton suggesting that the area should be equal to Sd. Since I personally dislike HTS and its dictatorial chief moron, I didn't follow or participate in the discussion, so I don't know what the general consensus ended up being or if anyone posted measurements of any kind.
 
I've experimented with from 30% to 75% of Sd. IMO, 100% of Sd is no different than FF with no plate. I never published my test results regarding THD and/or increases in efficiency/output, I only mentioned on occasion that dual opposed and plate loading and up/down firing and stacking are all beneficial and the benefits are additive.
 
So, help me out with the velocity thing?
 
And, is there any difference between 'slot loading' and plate loading? IOW, take the slot loaded sub and compare it to a FF, same-Vb version that has a plate in front of the drivers at a distance that is calculated to equal area of the slot. And, the same sub in a down-firing config with legs calculated for same area as well.
 
I've always thought it would be a worthwhile test outdoors to compare a DF sub with various length legs (different size support blocks under your stock sealed cube with the driver facing down) vs the same sub in FF config.

Check out this post on AVForum, showing some hornresponse modelling of different distances of a front/base/top plate:
http://www.avforums....0#post-20855553

Hope it is interesting/of use! :)

IMO slot- and plate-loading must effectively be the same thing - it must surely just present a reduced available area of expansion to the driver's cone, regardless of whether the 'escape zone' is circumferential or just to one side??
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#23 3ll3d00d

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Posted 11 August 2014 - 01:44 PM

The linked post on avf is wrong, I miscalculated one of the values so the effect was really exaggerated. The one further down (http://www.avforums....0#post-20869302) is accurate for the method described in diyaudio that assumes a circular plate BTW.
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#24 MemX

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Posted 11 August 2014 - 04:47 PM

D'oh, my bad!

#25 MemX

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Posted 07 September 2014 - 12:41 AM

With many thanks to 3ll3d00d for his patience and helping me out, and his excellent tutorial / guide on AVF (which links to and gives full credit to the other helpful posts on HTS and AVS), I have just about managed to get a Behringer UCA202 soundcard calibrated on REW, get a RadioShack meter setup and calibrated, and have just about got the hang of it...  I think... :blink:

 

So, first graph and first problem - it looks like the calibration on the setup only really goes down to 15Hz usefully, as the sweeping line (SPL Meter OFF) seems to suggest when compared to the captured output graph (SPL Meter on) which seems to stop capturing actual output at that point...

 

As per 3ll3d00d's recommendation, I shall have to order a CSL mic as that's calibrated to 5Hz and is not as expensive as the Bosso-approved mic! :D

 

 

I will do some MLP captures tomorrow, hopefully, as I've been at this screen for about 12 hours trying to get this bloody program to play ball, and I am now somewhat tired... lol

 

Respect to anyone who uses REW a lot - it is powerful and an amazing shareware, but it is not very user-friendly to get setup initially, seemingly!

 

 

Oh, and a big thank you to James, who was kind enough to lend me the mic and soundcard :)

 

 

 

EDIT:  I forgot to say I was slightly confused - the calibration graph of the soundcard (done via the loopback method) seems to suggest -3dB at around 4.5Hz, so I don't know why I'm not capturing down to that point?  (graph attached)

 

EDIT EDIT:  I'm having weird deja-vu like I've written this before, but I am 100% sure I haven't... lol

Attached Thumbnails

  • close mic measurement - 75db - audyssey off - no sub xover - no speakers - spl meter on+off.jpg
  • behringer 202 calibration - left loopback - output 0.266 input 0.237 - upload.jpg


#26 MemX

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Posted 07 September 2014 - 01:14 AM

Er...

 

 

 

Calibrated UMM-6 microphones will no longer be shipped outside the US??

 

http://cross-spectru...rated_umm6.html



#27 3ll3d00d

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Posted 07 September 2014 - 07:11 AM

Er...



Calibrated UMM-6 microphones will no longer be shipped outside the US??

http://cross-spectru...rated_umm6.html

The umm6 has a bit of a bad rep anyway. If you want USB then http://cross-spectru...rated_umik.html

The rising response looks like your meter cal file to me.

If you click "Change cal" on the measurement and remove the meter cal file then it will flatten out if that is the cause

#28 MemX

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Posted 07 September 2014 - 10:44 AM

Just went back and checked - I don't have a Cal file for the SPL meter? :unsure:  I calibrated the mic to the output on-screen using the REW SPL Meter section's calibration but I couldn't find a Cal file for the meter itself.  I think there are cal files for radioshack meters on HTS but I didn't see one for this UK-bought SPL meter, unless I am blind and missed it lol

 

I had them on C-Weighted, though.  This graph is what it looks like if I take C-weighted off.

 

I think I will have to go with the umik, then, thanks for the link  :)  As it comes with a Cal file it should make things a lot clearer! 

Attached Thumbnails

  • close mic measurement - 75db - audyssey off - no sub xover - no speakers - spl meter on+off - not c-weighted lines.jpg


#29 Madaeel

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Posted 09 September 2014 - 10:31 PM

MemX at a close mic sweep shouldn't the response not show effects from the room? Should be a typical sealed sub 12db roll-off right?

 

Hey 3II3 I was about to order the UMM-6 but now I'm curious why you said it has a bad rep?



#30 3ll3d00d

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Posted 10 September 2014 - 06:04 AM

Hey 3II3 I was about to order the UMM-6 but now I'm curious why you said it has a bad rep?


They seem to be physically quite brittle and have a higher noise floor then the umik, particularly at higher frequencies so not such an issue for sub measurements but still. The umik is also more convenient to use in REW because it has a known sensitivity, ie no SPL meter required. Basically I can't see a reason to get the umm over the umik.

#31 Madaeel

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Posted 11 September 2014 - 02:39 AM

Yah I did see that and said something to Paul about that noise floor. You're right. UMIK it is! Thanks man.

#32 hoppaz

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Posted 11 September 2014 - 06:48 PM

Hey MemX I stick my head in the forums over here to find you have a thread. Small world!

One thing about the umik is make sure the usb cable clicks and goes in to the mic more than it hangs out. I spent a couple of hours with mine not being found by windows not realising that I almost *felt* I had to break the mic pushing it in.

#33 MemX

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Posted 12 September 2014 - 11:51 PM

One thing about the umik is make sure the usb cable clicks and goes in to the mic more than it hangs out. I spent a couple of hours with mine not being found by windows not realising that I almost *felt* I had to break the mic pushing it in.

haha  I spent two hours chasing what I thought was a broken/mis-wired connection / broken amp, only to realise I needed to stop being a pansy and actually push the speakon in and turn it till it clicked... :facepalm: :lol:

 

I will have to get a UMIK and a soundcard ordered ASAP - my second sub is almost ready and I will need to give back the SPL Meter and soundcard I have very generously been lent when I pick it up... lol

 

 

 

Hey MemX I stick my head in the forums over here to find you have a thread. Small world!

I am omnipresent, don't you know :ph34r: ;) :lol:


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#34 MemX

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Posted 12 September 2014 - 11:53 PM

MemX at a close mic sweep shouldn't the response not show effects from the room? Should be a typical sealed sub 12db roll-off right?

 

Er, yeah...  I think you're right... :blink:

 

 

I have no idea what's going on really, watching me attempt measuring is like giving a monkey a typewriter and waiting for him to write Shakespeare... :lol:



#35 MemX

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Posted 13 September 2014 - 12:08 AM

Oh, and aaaaargh, CDL have sold out of UMIKs at the moment! :angry:  :lol:



#36 Madaeel

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Posted 13 September 2014 - 01:03 AM

Hahaha all I read was "giving a monkey a typewriter" and I started lol. You'll get it man. A monkey could run circles around me on a PC so I'll be in the same boat as you trust me. I guess I'll find out soon enough.

I ordered an UMIK last night and it didn't mention being oos.....hope I didn't get the last one.

#37 MemX

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Posted 13 September 2014 - 09:21 AM

If it was...  as it's you I'll let you off ;) :P



#38 MemX

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Posted 13 September 2014 - 09:44 AM

I will have to get a UMIK and a soundcard ordered ASAP

 

 

Wait, I am an idiot...  you don't need a soundcard with a USB UMIK... :huh:  :rolleyes:  :lol:



#39 Madaeel

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Posted 13 September 2014 - 02:57 PM

I didn't know that either. :(

Paul told me. He's my PC guide/mentor. Idk wtf I'm doing without him and Dave. Once I start using it I'm sure I'll pick it up quick but to set it up and all that bs is not something I'm looking forward too. I gotta go to BB today and a buy a laptop. Mic should be here this week.

#40 hoppaz

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Posted 14 September 2014 - 08:45 PM

Hey MemX you need to sort that omni presence out with a omni mic for sure.




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