8 ohm tweeter with 4 ohm woofer

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Hello,
I realize that this is probably a pathetically simple question for the vets; but you never learn unless you ask!

I have a set of Dayton DC130BS-4. I have not yet bought the tweeters, so I probably should obtain a 4 ohm version and attenuate with an l-pad.

However, I have a set of Goldwood GT-520 1 inch domes that I am also considering. They are 8 ohms as you can guess. I realize that there is no technical problem with this; but I am curious how I should try to match sensitivities.

Perhaps it is better that I put a 4 ohm resistor in parallel and then treat them as 4 ohm tweeters? Or is it simply a matter of subtracting a few dbs based on the 4 to 8 ohm drop?

As always, thanks to everyone!
 
the spec sheets use different methods for spec'ing the sensitivity of those drivers,
post 5 here may help: http://www.diyaudio.com/forums/multi-way/133371-how-convert-sensitivity-values.html

from here:http://techtalk.parts-express.com/forum/tech-talk-forum/42521-2-83v-m-1-watt-m
"Short story:
With 8 ohm drivers, dB/2.83v is the same as dB/w.
For 4 ohm drivers, 2.83v yields 2w. For xover work, if you have dB/w, add +3dB to get dB/2.83v.
By interpolation, a 6n driver (say, a tweeter) rated /w, add +1dB for 2.83v.
If you HAD a 5n driver (I've never seen one), I'd add +2dB for 2.83v.
Going the other way, subtract -3dB from /w rating to get /2.83v for a 16n driver, and for a 12n driver, -2dB from /w rating to get /2.83v."
 
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I don't think a 5" bass is going to be very loud anyway.

This Visaton 8 ohm stock crossover works well enough with a 4 ohm 5" paper bass, IMO. See, they've left room for an attenuator on the 8 ohm tweeter too. :)

LPad Driver Attenuation Circuit Designer Calculator
 

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as others said , compare all drivers sensitivity in dB/V/m
do use an L pad on the tweeter (tends to flatten the drivers impedance better and spreads the wasted heat.)
note higher impedance always takes a smaller series capacitor, so that's a plus.
 
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I found that quite confusing, the more I thought about it! :eek:

Goldwood GT520 8 ohm tweeter: 92 dB 1W/1m
Dayton Audio DC130BS-4 4ohm woofer: 91.6 dB 2.83V/1m

But actually, they are the same voltage sensitivity. You only have to add 3dB with 4 ohms 1w/1m electrical efficiency, because they run louder in the real world due to more current into 4 ohms. Hope I got that right.

Goldwood GT-520 1" Soft Dome Horn Tweeter
Dayton Audio DC130BS-4 5-1/4" Classic Shielded Woofer 4 Ohm

FWIW, I just modelled two similarly loud drivers in this configuration, and I needed around 3.9/8.2R attenuator.
 
\. I realize that there is no technical problem with this; but I am curious how I should try to match sensitivities.
!


you'll probably want to add some BSC to the crossover, so padding the tweeter is in order even if both are equal matched.
I generally go with the calculated sensitivity from a box modeling program for the midbass over the manufacturers numbers.
 
@Pete,
I genuinely appreciate answers to questions I didn't even know to ask!

So the DC130BS-4s have a sensitivity of 91.6 dB 2.83V/1m with 4 ohms. The GT-520s are 92 dB 1W/1m with 8 ohms (and therefore equivalent 92 db 2.83/1m?). In the math, should I calculate for 4 or 8 ohms? Although I'm guessing all the math comes out the same anyways? Or am I completely missing the point? Don't be afraid to tell me, I'm a scientist and everyone always says I'm wrong :p

If at 4 ohms the DC130Bs run 91.6 db 2.83V/1m then the GT-520s are 89 db 2.83/1m? Or am I backwards and the GT-520s are 95 db 2.83/1m equivalently? I have feeling I'm backwards as I expect the tweeter to generally be more sensitive and require padding as infinia remarked.

Thanks so much for the help, I can't thank you all enough.
Can't wait to know enough to help others!
 
Since we're enjoying ourselves here, here's some very rough modelling with similar drivers. All works well, IMO. Should be a nice speaker.

You always have to fiddle about with tweeter level, and I don't think you'll get that Visaton midrange bump.
 

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Oh wow, I should refresh my page before finishing a reply! You guys are awesome.

So, Steve, you agree that I was right and the woofer is technically more sensitive than the tweeter? So I would need an l-pad on the woofer lest the tweeters be drowned out?

And infinia, I'm totally game. If you're going to do something, do it right! However, I believe I understand the concept of BSC, but have no idea how to do that math or even what I would need to accomplish this and integrate it into a 2nd order crossover. I won't ask you to do everything for me, but could you point me in the right direction?
 
The rule of thumb for me when shopping is to get a tweeter that is equal to or greater than the woofer.

My thinking is that the treble power in music is about 1/10th that of the rest of the range, so if I am going to waste power in a resistor, it's much less power to pad down the tweeter than the woofer.

Maybe this works for me because I'm much more interested in the quality of the tweeter than the sensitivity matching.

Best,


Erik
 
Let's get you up to speed how this 5" thing works:
Vifa PL14WJ-

You probably want 0.33cu feet here or 10L at least. Bit more might be good. A reflex tube about 2" by 4".

Hi-Fi Speaker Cabinets in the Speaker Components Department at Parts Express | 288

This one looks a bit too small at 8L IMO:
5-1/4" Two-Way Speaker Starter Kit

BSC (a sort of bass boost) comes with the filter. For 5" 4 ohms, 1mH and 10uF is about right. For an 8 ohm driver you might be nearer 1.8mH coil and a 6.8uF capacitor.

This sort of speaker is a good one for a small bedroom or such. No deep bass, but enjoyable enough. And yes, you need the attenuator. Get some 7W 2.2R, 3.9R, 8.2R and 15R sandcast and I think you'll have enough options.
 

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sensitivity and impedance are two different issues.
set up your crossover filters to suit the IMPEDANCE of EACH driver.
Use a 4ohms crossover filter for the 4ohms driver. Use an 8ohms crossover filter for the 8ohms driver.

Then adjust (by adding an Lpad or similar) the crossover to suit the sensitivities so that the driver outputs match when an equal signal is present at the filter inputs.
 
And infinia, I'm totally game. If you're going to do something, do it right! However, I believe I understand the concept of BSC, but have no idea how to do that math or even what I would need to accomplish this and integrate it into a 2nd order crossover. I won't ask you to do everything for me, but could you point me in the right direction?

>Home of the Edge <Re BSC please spend time playing with this software and reading the text on the pages.

I usually design the woofers 2nd order LPF starting off with a 1st order to compensate for baffle loss (just a series inductor <see software above ) placing the half power point to match baffle width. lastly add a shunt cap to form a 2nd order by watching the speakers summed final response with the tweeters high passed output. BTW you can use many speaker Xover software or even free Spice network software. Depending on speakers placement to walls and taste, adjust lowest bass to tweeters passband roll-off anywhere from -1dB to -5dB. This is one reason why standard off-the-shelf speaker Xovers using text book filters rarely work on small speakers. (probably more successful on biggish speakers placed on walls etc.like system 7's designs)
 
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I can't think of many drivers this stock one would work with:

542936d1460336780-8-ohm-tweeter-4-ohm-woofer-visaton-8-ohm-3khz-crossover.png


But 4 ohm 5" bass and 8 ohm tweeter, happily, is one of them. :)

Visaton Boxsim shows many interesting aspects, like how a small box away from the wall might reduce bass. Or putting it near a wall increases apparent bass.

Then you get the boom from the room called room gain. A small speaker shouldn't be too affected by this.

I always find dispersion interesting. Here's the typical plot. Above and below axis you get a hole in the mids with even order filters. Looks quite good at 30 degrees to the side. So forward facing at ear height, perhaps on stands away from the wall, I'd say. :cool:
 

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Wow, thanks to everyone for their insight.

I am going to go through all of your posts tomorrow between experiments and try out some of the modeling programs and sites you recommended. Hopefully I will have a much better sense on what the right questions to ask are by the end of the day.

In the meantime I'm thinking it might be a good idea to look into more sensitive tweeters. This of course is due to the presumption yesterday that the Daytons are higher than the Goldwoods. This due to the earlier proposal that padding tweeters is a more efficient use of energy than the reverse. I'm thinking a pair of 4 or 8 ohm Vifa(Tymphany) 1 inch domes...although recommendations to match the Daytons are extremely welcome!

Stay tuned for hopefully better informed questions!
 
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