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Multi-Way Conventional loudspeakers with crossovers

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Old 25th November 2012, 12:51 AM   #51
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Location: Adelaide, South Australia
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Winslow - I promised to keep you posted on some measurements of the BEYMA 10XC25.

Tests I did today have shown that:
- The 1/3 octave smoothed measurements are very (very) close to those published by Beyma.
- A close investigation of the published plots indicated there may be a bit of fun ang games to get a relatively smooth an uncoloured response.
- Making measurements without smoothing there are a couple of features that really impact these for use outside sound reinforcement - in my humble opinion...

Beyma 10xc25 Nopara.pdf

Things of relevance to these measurements:
- Driver mounted in 280mm wide, 320mm high closed box stuffed with wool. (sizes approximate)
- Enclosure about 1.3 metres from floor and ceiling.
- Measurement made at 1 metre on axis
- Behringer cal mic used
- SPL something in the order of 90-100dB
- Gated measurements used - hence loss of meaningful data at low frequencies. (Cut off plots)

The top 3 plots have no smoothing applied at all. When smoothed these are remarkably similar to the Beyma data.

I also measured the second driver, which coincidentally I just reconed, and the response is smack on the OEM response. A nice thing to see!

The way I think Beyma address the rising response in the bass unit is to put the XO at 2KHz (if I recall 2.2?) and use this to roll off the rising response of the bass unit.

That dip in the horn is there, and is real. Without active EQ not a lot is going to fix that. That said, the unsmoothed response is rather unflattering - when run through a 1/3 octave smoothing, there is still a dip but it does not look like a chasm.

The plot showing bass and horn response is rather daunting... A quick listen to the bass driver shows it really does need some work.

I have not had a lot of time to think this through yet - but did choose to play with some active EQ on this to see how it could be "beaten into submission". I have not tried to be elegant e.g. using the rolloff of a high order XO's on the bass unit to flatten out the peak - just for now I "smacked it down" with a parametric EQ.

That said, with enough EQ you get the response shown at the bottom. It looks better than is sounds - though I suspect that a pair of these with a sub would be respectable.

Just for giggles - here is what I did in terms of EQ...
- BASS Unit EQ1:
Type: Parametric
Centre Freq: 1700Hz
Q: 4
Gain: +5dB

- BASS Unit EQ2:
Type: Parametric
Centre Freq: 300Hz
Q: 0.8
Gain:-5dB

- BASS Unit EQ3:
Type: Parametric
Centre Freq: 500Hz
Q: 10
Gain: +10dB

- Horn Unit EQ1:
Type: Parametric
Centre Freq: 7000Hz
Q: 0.7
Gain: +10dB

- Horn Unit EQ2:
Type: Parametric
Centre Freq: 4850Hz
Q: 10
Gain: +10dB

- Horn Unit EQ3:
Type: Parametric
Centre Freq: 7000Hz (yes - but High Q)
Q: 10
Gain: +10dB

Would I use them like this? No.

Will they work, and would they be good for PA? Yes

Are they HIFI? I don't think so yet...

Last edited by googlyone; 25th November 2012 at 12:56 AM. Reason: update
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Old 9th December 2012, 12:23 AM   #52
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Location: San Diego
Quote:
Originally Posted by JRKO View Post
10" coax for the car?!?!

Aren't the benefit of a 'point source' driver kinda nullified with legs, tunnel & shifter in the way and unequal listening distances/angles?
At home I used Gedlee Summas, but nearly all of my car audio experiments have been variations on a point-source speaker, or approximating one. And the reason is very simple:

You're sitting very close to the drivers.

For instance, if I listen to my Summas at a distance of 4-6 meters, they blend well. But if you listen to them very close, the transition to the midrange suffers because you're in the nearfield.

Long story short, I prefer not to listen to speakers in the nearfield, and in the car that's hard to do because of the large distances between woofer and tweeter.
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