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MHB-46 Measurements

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slaith View Drop Down
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    Posted: 08 July 2013 at 9:54pm
So finally got around to doing some measurements on my MHB-46:s.

The amp used was a PROLINE 3000 (Not that it really matters).
Wattage into boxes: Don't really know forgot to measure. Embarrassed
SPL level calibrated with cheap DB meter, so take the SPL with a pinch of salt. (or pint of beer).

A few word about my boxes:
Driver is RCF LF18G401.
They differ from the original ones in that the port go all the way out to the sides of the boxes, but I made the port narrower.
So the area and tuning reamins the same, did some simulations in hornresp and the difference was nothing to be concerned about.

The microphone was on the ground on all the measurements, aprox 1,5m from the box.
Did measure on one box standing up, one box on the side and finally 2 boxes standing up side by side.
Didn't measure with the stacked option primarily because I thought my back would break in two, or maybe a change of underwear would be needed.

This and some other measurements may come when there is more people around to do the heavy lifting. Wink

First picture.
Explained by the text inside.
What I can deduct from my measurements is that these work best in pairs.
The dip between the horn and port is gone in the doublebox measurement.


The second image is of some EQ:ing I did just to see if I could get rid of the dip.
The values are inside the picture.
Honestly I didn't hear that much of a difference between the two.
But the values are there to be used if you will, (Don't blame me for blown drivers though).


Conclusion:

Admitedly these are the first 18" horns i have built so I have no real reference here, but I am more than happy with their performance.
Especially since I only have two, will probaly build 2 more and be happy with that.
With the driver I have now I gave them arond 1000Watts per driver, (saw my pdu showing around 9 amps).
And they didn't even sound bad, just kept on giving, although this is more than the rated power of the driver.
Personaly I think that the recommendation that one should not put more than 6-700 watts into a single box is a bit on the safe side.
They take alot more and are happy with it, depending on the driver of course.

I'll answer any questions that you guys might have to the best of my capabilities..

Patrik

(Edit: images on another server)


Edited by slaith - 08 July 2013 at 11:30pm
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slaith View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slaith Quote  Post ReplyReply Direct Link To This Post Posted: 08 July 2013 at 9:54pm
Saw that the pictures are to small will fix that right away ....sorry for that.

Fixed!

Whoever wrote the image resolution script on this forum should have their skin flayed!


Edited by slaith - 08 July 2013 at 10:22pm
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Keen View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Keen Quote  Post ReplyReply Direct Link To This Post Posted: 08 July 2013 at 10:29pm
Nice work Thumbs Up , thanks for posting
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MR-FIZZLE-89 Quote  Post ReplyReply Direct Link To This Post Posted: 09 July 2013 at 3:39pm
Great stuff Slaith Thumbs Up
 
Would be interesting to see pictures of your modifications to the port Wink
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slaith View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slaith Quote  Post ReplyReply Direct Link To This Post Posted: 09 July 2013 at 6:31pm
Will do, but at the moment it's filler and paint.
So they are not really respectable just yet.

But it's coming.

Glad you guys find the measurements informative.



Edited by slaith - 09 July 2013 at 6:31pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 09 July 2013 at 6:38pm
Seems like quite a big box with a large port considering it only goes down to 50Hz even in pairs…
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slaith View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slaith Quote  Post ReplyReply Direct Link To This Post Posted: 09 July 2013 at 8:22pm
One could probably reduce the height and thereby lowering the volume of the chamber, and not shortening the horn.
Just by compensating with port length.
Could maybe shrink the height by 10-15cm.

But I suppose that Marc.O has thought about this, considering chamber pressure and portspeed.

Even on hornplans it says does 40Hz when using 4, but I can honestly say i'm not really missing anything at the deep lower end.
Not for the music i'm playing through them.
For roots and dub something would probably be missing on the lower end.

But then again I chose this configuration mainly because it has a usable spectrum from 40:ish up to 120hz, which means I can use them for kick also.
And thereby reduce the size of my lower-mid bin.

Since these are the only "horns" I have heard, I have nothing to compare to.
Maybe someone who has heard both types can shine some light on the subject?
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martinsson View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote martinsson Quote  Post ReplyReply Direct Link To This Post Posted: 09 July 2013 at 9:04pm
Yes, it is rather big, and yes it drops of at ~50Hz, again proving that there are no free lunches, the same can be said for alot, if not all of other popular designs out there, it's just a matter of how the design is balanced with regards to LF extension, size or SPL capacity, simply choose a design that meets you needs, capabillities and priorities.

What they do really well, and what i think was the designers intent, was to achieve high SPL capacity in a range that covers most usercases with only a single 18" driver, to me that signifies a well thought out design with a clear objective, and as far as i could tell the objective was achieved.

Thank you Slaith for the opertunity to listen your system, it is well woth repeating what a nice job you have done, and what a impressive result you achived, cutting cost with skill, knowledge and hard work.

Pro-fi diy-nerd from sweden
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MarjanM View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 10 July 2013 at 6:12pm
Increasing the port length will tune the back chamber lower. So maybe worth trying since boxes are not painted yet.
Marjan Milosevic
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slaith View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slaith Quote  Post ReplyReply Direct Link To This Post Posted: 10 July 2013 at 8:23pm
I could probaly do that, but i'm not really missing anything in performance from the sub.
However I could probably make a protype vent to clamp on the front just to measure the frequency response.
But that will probably happen after painting, will in all likelyhood spray them tomorrow.

But if I lower the tuning of the port, the dip between horn response and port will be even bigger.
Which in turn means that I would have to apply more eq to correct this.

But I will give it a test (probably).

Also remembered that at resonance the movement of the driver is lowest, so if i apply some narrow eq at that frequency I could probably make the frequence response a little lower.
Without compromising the cone movement to much.

Question is how to verify where the movement is lowest?
I will measure the impedance of the cab, so that would be a good start.
But the determine the bandwidth of the eq?
Ideas anyone?
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MarjanM View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 10 July 2013 at 9:20pm
With 4 boxes the dip will be gone anyway.




Edited by MarjanM - 10 July 2013 at 9:24pm
Marjan Milosevic
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slaith View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slaith Quote  Post ReplyReply Direct Link To This Post Posted: 10 July 2013 at 9:44pm
Yeah you're right, it will be gone, and besides I will allways run these in pairs if I have to split them left/right.

I'll have to think about it, it can always be fitted afterwards.
There's plenty of space in the box.
Wonder how much I should add?
Should probably make something on the outside to just test, since the measurements are being done with very little power applied.

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