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MT121 comp driver probs

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biggins View Drop Down
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    Posted: 25 April 2021 at 7:25am
Hi there,

I'm hoping someone can help me troubleshoot an issue that i am having with some comp drivers in MT121.

Originally, I had the cabs loaded with P-Audio BMD750 and was seeing an issue where the audio dropped off steeply arund 10Khz. I thought the BMD-750s were crapping out above 10k because they are 2" comp drivers and apparently that is A Thing.

To try and rectify the situation, I picked up some BMS 4555. However when I measure the new comp drivers driver using REW I am still seeing a pretty steep drop off around 10K.

* Measurement of BMS 4555 (laptop > soundcard > amplifier > BMS4555): 

 


* Measurement of BMS 4555 (laptop > soundcard > processing > amplifier > BMS4555)
processing is just some EQ to smooth stuff out

  

~~~~~~~~~~~~~~~~~~~~~~~~~~
 
My expectation (hope) was that the 1.5" comp drivers would behave better above 10Khz but that's not what i am seeing. The comp drivers are attached to a P-Audio P2723 2" horn (with 1.5" -> 2" adapter).

So, I'm a little stuck as to how to proceed. I'm wondering if the issue is being caused by the P2723 horn. Maybe i f'ed up and bought the wrong horn and i need to buy different horns? However, before I spend more $$$ on new horns/shipping, I wanted to get a 2nd opinion on the above issue cos maybe I am missing something or maybe there is some more troubleshooting i can do..

If it is the horn, can anyone give an opinion on the BMS2230 horn or the B&C ME60 paired with the BMS4555? Am also open to other suggests.

Thanks in advance
B

Links:
Comp Driver: http://www.bmsspeakers.com/index.php?id=bms_4555
P-Audio Horn: http://www.paudiothailand.com/pac/index.cfm/products/product/?id=566

BMS 2230 horn: https://www.thomann.de/intl/bms_2230.htm
B&C ME60 horn: https://www.thomann.de/intl/bc_me_60.htm


Edited by biggins - 25 April 2021 at 8:08am
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biggins View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote biggins Quote  Post ReplyReply Direct Link To This Post Posted: 25 April 2021 at 7:37am
OMG, trying to get images to display. Faaark.... Confused


Edited by biggins - 25 April 2021 at 8:09am
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fatfreddiescat View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote fatfreddiescat Quote  Post ReplyReply Direct Link To This Post Posted: 25 April 2021 at 9:20am
Looks like a normal response for a constanrt directivity waveguide, here's a link to a previous discussion that cove rs this topic:

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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: 26 April 2021 at 12:44pm
First of all you can not put 1.5 inch exit driver to a 2 inch throat horn.
I mean you can, obviously, but it will have issues.
Second, just add a highshelv eq above 10Khz and it will be way better.



Edited by MarjanM - 26 April 2021 at 12:46pm
Marjan Milosevic
MM-Acoustics
www.mm-acoustics.com
https://www.facebook.com/pages/MM-Acoustics/608901282527713
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levyte357- View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357- Quote  Post ReplyReply Direct Link To This Post Posted: 26 April 2021 at 3:49pm
Also the 2" horn is very important.

Been easily getting upto 16khz,  with Beyma CP750TI, with B&C ME60 & ME75 Alum horns.

But they are decent, not Cheap sh*t.

I also have approx 12x EV HP940 horns, which are best I have ever heard, but will not be going anywhere.LOL
"Gentlemen, you can't fight in here, this is the war room!!".
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Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357- Quote  Post ReplyReply Direct Link To This Post Posted: 26 April 2021 at 3:55pm
Make life easy, try using decent comps with fairly flat response chart upto 12khz.

Then add correcting eq as suggested by Marjan.

Beyma cp755nd as used in some Void tops, are smooth, loud, go plenty above 12khz.


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biggins View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote biggins Quote  Post ReplyReply Direct Link To This Post Posted: 27 April 2021 at 10:17am
Hi, 

Thanks for the replies all. Lots of info to digest in the Audio Heritage thread in the thread shared by fatfreddiescat. I think that will take a few sittings to digest.

MarjanM & Levyte357 - Thanks for the replies. I'll have a play about with the High Shelf EQ.  Thumbs Up

MarjanM - Sorry, I'm gonna be that guy and ask The Question. Why would you not put a 1.5 comp driver on a 2" horn (using an adaptor)?


Edited by biggins - 27 April 2021 at 10:19am
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