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Old 3rd January 2013, 07:35 PM   #51
badman is offline badman  United States
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I've not liked the cap-only method of attenuation when there's a big sensitivity gap. With a smaller gap it's less of an issue, but if it's 3dB or more I always use at least 1 resistor.
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Old 3rd January 2013, 08:14 PM   #52
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by badman View Post
I've not liked the cap-only method of attenuation when there's a big sensitivity gap.
With a smaller gap it's less of an issue, but if it's 3dB or more I always use at least 1 resistor.
Hi,

Generally I would agree, but the flushmount Dayton looks
particularly well suited to a single cap for around 10KHz
x/o, effectively using a higher x/o point for attenuation.

In this particular case more than 3dB should be fine.

rgds, sreten.
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Old 3rd January 2013, 08:53 PM   #53
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Dayton's ordered. Can't wait for them to arrive
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Old 4th January 2013, 08:25 PM   #54
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Just been looking at the frequency response graphs on the datasheets for the EL70s and the Dayton ND20FA-6. At 10KHz the EL70 is 85dB and the Daytons are 92dB. This seems quite a bit of difference in sensitivity.

I have a couple of ideas that I will try, I am new to crossovers and speaker matching, so please correct any of my errors I've made here and any other advice is gratefully received.

1) I could put a 6 ohm resistor in series with the Dayton, that would give me -6dB giving me a total of 12 ohms. Now for 12 ohms and a crossover point of 10K, I would add a 1.32uF cap.

2) I could put a 2.5 ohm resistor in series with the Dayton, I would get roughly a 3dB attenuation, and then I have 8.5 ohms and I could use a 1.87uF cap to cross at 10KHz.

3) No resistor at all and use a 1.32uF cap to cross at 20KHz, as this would give me a 6dB attenuation at 10KHz anyway.
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Old 4th January 2013, 08:35 PM   #55
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Option 1 and 3 seem to make the most sense to me, but these options are only really necessary if you do plan to have a front-firing tweeter. I think it is worthwhile to consider that there is a very high likelihood that the speakers will lose a lot of top end coherence in this configuration.

The best option, from all the reading I have done, is to mount the tweeters in the backs of the speakers, with a simple cap to crossover where you want it. Maybe a resistor, too, but backfiring will attenuate significantly on its own...

Forum member Pit Hinder explains... Adding Tweeter to Full Range

That whole thread is very informative, IMO.

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Old 4th January 2013, 09:01 PM   #56
sreten is offline sreten  United Kingdom
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Hi,

3) is your best first option, use 1.0uF and 0.33uF in parallel.
(Removing the 0.33uf will reduce extreme treble a touch.)

Its better than 1) due to the tweeters roll-off above 10KHz.
With just the capacitor 3), the response won't roll-off.

rgds, sreten.
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Old 4th January 2013, 09:11 PM   #57
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Thanks for your responses, so at least in theory my calculations were OK, so at least I can experiment and kind of understand what I should be affecting with the various components I am placing.

Cogitech, that thread was an interesting read, thanks.

Sreten, I think the single capacitor (well, 2 parallel caps) is the cheapest and easiest option and looks like it would do the job. I'll have to order up a few caps and wait for the tweeters and caps to arrive.
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Old 4th January 2013, 09:18 PM   #58
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Cool. I am very much in the learning stages as well. I look forward to hearing how your project goes.

Just yesterday I ordered some 2.2 uF Roederstein caps off e-bay to replace the 3.3 uF I have in the retro crossovers. I think the tweeters could stand to be crossed a bit higher. I might also swap out the resistors for something slightly smaller. I am thinking I will limit the bandwidth to 8k and up, but then add a couple of dB and mount the tweeters backside... I think I will play with all sorts of configurations and see what I like best.

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Old 4th January 2013, 09:49 PM   #59
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Let me point out the real issue you're fighting with here. Beaming. The EL70 beams quite a bit, which is why you're feeling like it's missing "air" or "sparkle" or what ever it is you're after.

Here it is on axis
Click the image to open in full size.

Here is 5, 25, and 45 degrees
Click the image to open in full size.

Because we're in breakup land above 4khz, you can see there is some bunching and spreading depending on the frequency, not nice parallel lines. Not bad though, just ignore the bunching for a while and assume they're parallel.

By 10khz the response is down 5db at only 5 degrees off axis! So what do you think is going to happen when you introduce a nearly omnidirectional tweeter around 10khz? It's going to spray sound all over the place and fill in all that sound that is missing off axis.

Now move back on axis. You have nearly flat response with the EL70, plus all the extra ouput of the tweeter. That's going to sound to bright.

Just beware.
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Old 4th January 2013, 09:54 PM   #60
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Quote:
Originally Posted by tuxedocivic View Post
Because we're in breakup land above 4khz
Transition from piston to breakup is actually at 650 Hz. The nature of it is pretty much under control until 4kHz.

Ryan,is that your old EL70 or your new EL70eN?

dave
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