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Old 2nd December 2011, 10:58 PM   #1
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Default Would this work?

I know it is taboo to talk crossovers here, but it has been suggested enough times around here that some people like to add a tweeter to their FR systems for some more "air" up top.

I am just playing with this idea for now, but I'd like to know your opinions on this...
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Old 3rd December 2011, 02:45 AM   #2
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Hi Cogitech,

1. Can you post at least the tweeter's specs? It would be interesting to see the attenuation at the tweeter's Fs.

2. Just curious, what do you like about this tweeter? Have you heard a good ribbon tweeter?

3. 1st order parallel is a classy choice. Are you familiar with 1st order series? It has some unique advantages / tradeoffs.
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Old 3rd December 2011, 02:58 AM   #3
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Not to sound like Debbie Downer, but probably not. I take it those xo values from an online calculator or something? That tweeter will likeling ring at Fs (right around 2000hz I suspect). 2nd order would protect it better. Also, if there is a phase mismatch, which is quite likely with a dual woofer arrangement, you could end up with a null at the xo point. The acoustic center offset between the woofer and tweeter are very close to the half wavelength at 6000hz.

I've worked with the larger version of that tweeter (nd28f-6). It sounds great
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Old 3rd December 2011, 04:54 AM   #4
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Quote:
Originally Posted by rjbond3rd View Post
Hi Cogitech,

1. Can you post at least the tweeter's specs? It would be interesting to see the attenuation at the tweeter's Fs.
http://www.solen.ca/pdf/dayton/ND16FA-6.pdf

Quote:
2. Just curious, what do you like about this tweeter? Have you heard a good ribbon tweeter?
A) A few people at Parts-Express have raved about it being as good as a ribbon, no ringing, etc.

B) I love the form factor. For my application (retro-fit) this is one of the only tweeters that will work. Drill a hole and shove it in

C) The price is right.

Quote:
3. 1st order parallel is a classy choice. Are you familiar with 1st order series? It has some unique advantages / tradeoffs.
I chose this type of crossover because it requires the fewest components, which means 2 things to me; cheap and easy. I am actually not familiar with any crossovers, as I am a newbie, and chose FR for simplicity initially.
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Old 3rd December 2011, 04:58 AM   #5
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Quote:
Originally Posted by tuxedocivic View Post
Not to sound like Debbie Downer, but probably not. I take it those xo values from an online calculator or something? That tweeter will likeling ring at Fs (right around 2000hz I suspect). 2nd order would protect it better. Also, if there is a phase mismatch, which is quite likely with a dual woofer arrangement, you could end up with a null at the xo point. The acoustic center offset between the woofer and tweeter are very close to the half wavelength at 6000hz.

I've worked with the larger version of that tweeter (nd28f-6). It sounds great
Yep, online calculator. I wanted to aim for a very high crossover because I love the presence and tone of my EL70s and I really only thought some shine at the very high end might be nice.

If I crossover at 6k, how will it ring at Fs (2283hz) ?

Forgive my ignorance, but I don't understand the third-last sentence (last sentence of first paragraph, to be precise). Is that a bad thing, or a good thing?

Last edited by cogitech; 3rd December 2011 at 05:06 AM.
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Old 3rd December 2011, 05:01 AM   #6
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I see now that I misread the specs on the tweeter. They are 6ohm. Not sure how I made that error... perhaps there is an 8ohm version as well...
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Old 3rd December 2011, 05:12 AM   #7
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Quote:
Originally Posted by cogitech View Post
I chose this type of crossover because it requires the fewest components, which means 2 things to me; cheap and easy. I am actually not familiar with any crossovers, as I am a newbie, and chose FR for simplicity initially.
Hi cogitech, 1st order series uses the same number of parts as 1st order parallel, just wired differently. A lot of people feel 1st order sounds best when it's an option.

An oversimplification but whereas parallel 1st order consists of two "separate modules," (a high pass and low pass, the values of which you might choose more or less independently), series crossover has an interesting property in that the cap and coil work together to split the signal "sort of perfectly." I've not stated it well but that's the basic idea. I think it's even simpler than the crossover you've suggested (same number of parts but potentially more tolerance and potentially easier to dial in).

The trick is that the drivers will have significant overlap as 1st order, and while that has good phase characteristics (which are -totally- audible in my limited experience), the shallow attenuation means you want to cross well away from the tweeter's Fs. And well away from any midrange / treble problems that the fullrangers might have on their top end (probably not a consideration with widebanders but a consideration for woofers of larger size).

I'm definitely no expert but your project is similar to something I'm fiddling with.
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Old 3rd December 2011, 05:23 AM   #8
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Quote:
Originally Posted by rjbond3rd View Post
Hi cogitech, 1st order series uses the same number of parts as 1st order parallel, just wired differently. A lot of people feel 1st order sounds best when it's an option.

An oversimplification but whereas parallel 1st order consists of two "separate modules," (a high pass and low pass, the values of which you might choose more or less independently), series crossover has an interesting property in that the cap and coil work together to split the signal "sort of perfectly." I've not stated it well but that's the basic idea. I think it's even simpler than the crossover you've suggested (same number of parts but potentially more tolerance and potentially easier to dial in).

The trick is that the drivers will have significant overlap as 1st order, and while that has good phase characteristics (which are -totally- audible in my limited experience), the shallow attenuation means you want to cross well away from the tweeter's Fs. And well away from any midrange / treble problems that the fullrangers might have on their top end (probably not a consideration with widebanders but a consideration for woofers of larger size).

I'm definitely no expert but your project is similar to something I'm fiddling with.
Interesting. Thanks for taking the time to explain that to me. It does sound as if series 1st order would be better. 6k crossover point is quite far from the tweeter Fs (2283hz), so I suppose I'm OK there. The EL70s start to roll off very, very gently after about 5k, which is why I chose 6k to bring in the tweeter. I don't think the EL70s have any real "problems" in that upper range... In fact, they are actually really quite nice on their own, just rolled off in a classy, "warm", "vintage" sort of way.

Perhaps an L-pad would be handy for the tweet, so I can choose just how much "air" I want.

The other option is to just stick with the EQ or "Treble" knob and leave well enough alone. I'm just a bit of a tinkerer and need something to tinker with, or at least think about tinkering with.

Last edited by cogitech; 3rd December 2011 at 05:26 AM.
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Old 3rd December 2011, 09:14 AM   #9
ODougbo is offline ODougbo  United States
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Default My two cents:

Quote:
Originally Posted by cogitech View Post
I know it is taboo to talk crossovers here, but it has been suggested enough times around here that some people like to add a tweeter to their FR systems for some more "air" up top.

I am just playing with this idea for now, but I'd like to know your opinions on this...
My two cents: It looks way too risky as far speaker building goes; talking from experience and have old double woofer boxes around that fit this idea.

Take a look at Madisound's HDS kit, they have been there since 1972 and the fellows there designed this.

I've built 10 so far, and using one for my center channel. It will take a couple of months of break in period, but once it get going, it's remarkable. The other 9 are spread out among friends, they think they are great and are spreading the word around.

HDS Home Theater Kit - Parts Only: Madisound Speaker Store
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File Type: jpg HDS HDS Kit 01.JPG (617.2 KB, 215 views)
File Type: jpg HDS Cross 02.JPG (712.8 KB, 200 views)
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Old 3rd December 2011, 01:31 PM   #10
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Quote:
Originally Posted by cogitech View Post
6k crossover point is quite far from the tweeter Fs (2283hz), so I suppose I'm OK there... Perhaps an L-pad would be handy for the tweet, so I can choose just how much "air" I want.
Hi cogitech,

But with a first-order crossover, the attenuation is only 6db/octave so 6k is actually very _close_ to Fs. Let's say it's an octave and a half (1.5k is two octaves away from 6k). So it will be attenuated 6db at 3k, 12db at 1.5k. So let's call it roughly 9db at Fs.

That's probably not enough attenuation and so for a first order crossover, for that particular tweeter, you probably want a higher crossover point (or alternatively, a steeper slope but there goes all the fun!)

Air in my experience is around 12k. Don't get discouraged, you are on a good and exciting (and affordable) DIY path with first order crossovers. The quality of sound is in keeping with single driver principles, especially the series variety.
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