what to do with Neo8s + 12" midbass + 18" subwoofer: large box or OB? - Page 2 - diyAudio
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Old 30th June 2013, 11:53 AM   #11
Scott L is offline Scott L  United States
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Default Very nice post

Greg:
The above is a very nice post. A lot of valuable information. Thanks.
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Old 1st July 2013, 09:20 AM   #12
zmyrna is offline zmyrna  United Kingdom
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Thank you very much for the excellent post, Greg.
Cool pictures too.
My 12" mid is very similar in TS to the 10" ScanSpeak you have used in your monitor.
Main difference is in Fs (50 vs 23) and efficiency (100 vs 90).
I did buy the wood for the upper box in the weekend. Cheap 18mm spruce ply.
Cabinet will be h40; w75; d44 cm in size.
Housing 12" FaitalPro and Neo8s in separate sealed compartments of 65 and 33 liters respectively.
This box will cross to a large bass reflex sub base at around 80-120hz.
Once this box is up and running, I will experiment with diy waveguide and edge rounding, both made out of acoustic foam.
Adding a ribbon supertweeter on top of this box is also in the book.
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Old 1st July 2013, 12:59 PM   #13
zmyrna is offline zmyrna  United Kingdom
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Greg,
Here is my response to your Qs:
I have built a few OB prototypes using vintage alnico Seas drivers.
These sound sweet in the mid freq at low-medium volume.
I have also tested some PA drivers on the nude.
However, I haven't heard a top class OB speaker.
Orion and Nao type OBs have too much EQ and cone movement for my liking (I don't like how those modern hifi drivers sound).
My ideal OB would be a B&G linesource (like yours or Stig's).
But I do not have the cash or room for such a system.
I live in a rental flat in London. And I move quite often.
So placement is critical for me.
For me, even a fridge size direct radiator is more practical than an OB.
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Old 9th August 2013, 08:01 PM   #14
taloyd is offline taloyd  United States
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Quote:
Originally Posted by zmyrna View Post
However I tested the nude 12" and 18" yesterday evening and did not like the sound very much.

Either the drivers or my amps or both are clipping.

I tried 18" HP 30, LP from 100 to 200, with 6-14 dB compensation.

And 12" HP from 100-200, LP 1000, with 3-14 dB comp.

Several other DIYers seem to use similar drivers in this set-up with great reported results. Am I missing something?
Are you boosting the OB cancellation loss (acoustic short-circuit), or cutting above that frequency (ie: a shelving filter)? If the former - that might be why it's clipping. If the latter - then nevermind! You usually want to cut with EQ - never boost as that eats away at headroom/dynamic range...

cheers,
-Tal
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Old 13th August 2013, 10:16 AM   #15
zmyrna is offline zmyrna  United Kingdom
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Tal;
I knew I was missing sth. Indeed, I was boosting the OB loss. Does that cause some sort of digital overload? If so why is it there on the DSP software?
I will try the opposite, when I have a chance.
However, I am quite committed to my massive box built these days.
I did cut the baffles in the weekend.
I am fully in love with the vintage JBL studio monitor look.
It will be an homage to JBL 4345.
Attached Images
File Type: jpg 4345jbl.jpg (5.8 KB, 348 views)
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Old 14th August 2013, 02:29 PM   #16
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You can boost with the mini, but I would lower the level for that channel in the dsp by the same amount of boost that you are using to prevent clipping the outputs.
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Old 15th August 2013, 01:23 PM   #17
zmyrna is offline zmyrna  United Kingdom
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I was planning a nude dipole like these:

the three way nude swinging dipole thread
4-way Dipolar Disorder........

before running into DSP clipping.

What now? Am I going to have to throw away all that wood and insulation and what not?
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Old 15th August 2013, 11:49 PM   #18
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Quote:
Originally Posted by zmyrna View Post
I was planning a nude dipole like these:

the three way nude swinging dipole thread
4-way Dipolar Disorder........

before running into DSP clipping.

What now? Am I going to have to throw away all that wood and insulation and what not?
Clipping your DSP and still not getting enough output? You're either going for concert PA levels or something is not adjusted optimally. Or you've boosted the low end of the woofer far too much. Can you run through your set-up once more?

Greg
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Old 16th August 2013, 08:29 AM   #19
zmyrna is offline zmyrna  United Kingdom
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True, it was not the drivers running out of excursion (the cones were not moving much).
It was probably the DSP. Remember, I am using a fully digital DSP. So no opamps or like.
Last night I tried lowering the higher end instead of boosting the lower end and it sounded much better. However these large PA drivers still make some unhappy noises when driven nude with EQ.
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Old 16th August 2013, 03:24 PM   #20
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Quote:
Originally Posted by zmyrna View Post
True, it was not the drivers running out of excursion (the cones were not moving much).
It was probably the DSP. Remember, I am using a fully digital DSP. So no opamps or like.
Last night I tried lowering the higher end instead of boosting the lower end and it sounded much better. However these large PA drivers still make some unhappy noises when driven nude with EQ.
So you're not applying any boost at all? When you cut the high freq to match the low you still have to raise the level of that driver to match the rest of the system, or cut your higher freq units to match the bass. You said you are using Panasonic power DACs, which I assume are receivers? If you are raising the level here, I wonder if you are clipping the DAC outputs for your woofers in the receiver. Dipole woofers can take a lot of power.

I don't really see much benefit in running the bass drivers nude, especially with the low Q woofers you are using. Depending on how low you want these to go, you would need to shelf down the high freq quite a bit to get any appreciable bass output. An h-frame or at least a large baffle will help quite a bit. A hi-pass filter at or below your low corner will help protect against over excursion as well.
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