crossover help for my boombox

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gio89

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Joined 2011
#1
I have built this boombox
PIC_0002.JPG

It sounds good but I would like to make sure it sounds the best.
I am using a lepai amp and hivi b3n speakers, but I would like to add a crossover and these dayton audio tweeters. If any one knows a crossover design to add tweeters to these speakers it would help me out greatly.
Right now they are 8 ohm speakers but ideally I am looking for 4 ohms after the added tweeter if its possible.
Thank you for anyone that can help. 🙂
 
#6
As a reference you will need to mod the sensitivity of the crossover with the new drivers.
L-pad is playing with original drivers 8R/10R (series/parallel)
for Dayton ND20FA-6 3/4" (~90dB) and you're moving to Dayton ND16FA-6 5/8" tweeter (~89dB). You need to go up 1-2dBs here.
The same with the Swan Hivi BN3 vs. HiVi B4N 4" (82dB vs. 85dB). You need to drop ~3 db's here to match your smaller driver. All in all you can start to change your crossover l-pad for less 1 or 2 dB.
Overview M3N Full-Frequency_HiVi, Inc.
Large Bande - HiVi B4N Haut-Parleur Large-Bande Aluminium-Magnésium 4"
(Note) you might be happy with the result before changing, you will probably will notice the tweeter louder to start with, there are more important details like a good integration of the two drivers at crossover frequency.
 
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#12
we can use the data sheets from the manufactures right?
Click to expand...
We are just looking at the data provided by the manufacturers, impedance, output et al.
If you know how to recreate the drawing for the crossover that I would need to use, that would be great.
Click to expand...
For a more accurate process of simulating as you imply, without measurements, mics and other equipment, you must have available the drivers FRD & ZMA files. There are only two or three ways:
1. The files are available for use because they were published by someone.
2. You measure them (drivers) with measurement hardware.
3. You used the drivers datasheets to make pseudo-frd/zma files making use of processing scanning software for this effect.
Driver FRD & ZMA files
FRD & ZMA File Online Data Base
 
#14
After spending some time looking at the graphs of the speakers and tweeters used in the overnight sensations I have concluded that the graphs of the hivi speakers in the sensations and my boombox are almost identical. The tweeters are also almost identical except that the ones I want to use have a little higher peak in the impedance.

So if i use the same diagram as the overnight sensations, I think i will be fairly close to what I want to achieve.

My question now is, how do I go about fixing the the db changes you mentioned, and how do I lower that impedance peak by the additional 2ohms difference.

PS. I would like it all to be 4 ohms, because the lepai amp I am using puts out 20watts per channel at 4 ohms.
 
#16
gio89 said:
PS. I would like it all to be 4 ohms, because the lepai amp I am using puts out 20watts per channel at 4 ohms.
Click to expand...

Power supply requirements
From datasheet of TA2020, we can obtain the following values:
88%@12W8Ω
81%@20W4Ω
So we have:
13.636364W x2 -> 27,26W at 8Ω
24.691358W x2 -> 49,38W at 4Ω

Then we need at least a 12v Power Supply Unit and preferably not above 13.5v (because above of that the Lepai zenner diode for protection will reduce it, and will be useless, and some users reported that sound quality decreases). The higher the Voltage supplied, the more power will be able to output the amp, so 13.5V are desirable.

It will also should be capable of at least 3.7A @ 13.5V (13.5 * 3.7 = 50W, which is the needed for 4Ω loads), or 2A @ 13.5V (for 8Ω loads).

For a 12V PSU will need 4.1A @ 12V (12 * 4.1 = 50W, which is the needed for 4Ω loads), or 2.3A @ 12V (for 8Ω loads).
Amplifier:Lepai T Amp - diyAudio
Click to expand...
Close to 6 ohm (woofer/tweeter), is that a problem for you?

gio89 said:
After spending some time looking at the graphs of the speakers and tweeters used in the overnight sensations I have concluded that the graphs of the hivi speakers in the sensations and my boombox are almost identical. The tweeters are also almost identical except that the ones I want to use have a little higher peak in the impedance.

So if i use the same diagram as the overnight sensations, I think i will be fairly close to what I want to achieve.
Click to expand...
You will be very close, no need for big changes (if you're lucky). The problem if any, is the integration at crossover frequency, impossible to guess without a simulation. Not a problem in a boombox but more in a commercial product or hifi/audiophile type of loudspeaker.
You just need to adjust for the different sensitivities.

gio89 said:
My question now is, how do I go about fixing the the db changes you mentioned, and how do I lower that impedance peak by the additional 2ohms difference.
Click to expand...
I don't see the impedance peak in a driver being a problem for you in the general concept.
You just need to add (1 or) 2dB attenuation to the 8R/10R l-pad. Subject to your verification and testing.
 
#18
6 ohms is fine. 🙂
and on the l-pad it looks like it is 6R/10R not 8R/10R. (its hard to see the number but i found a higher quality image of the crossover layout and it is a 6R in series and 10R in parallel.
So knowing that should i change the 6R to a 8R to get the db changes I need?
Also what watt rating should the resistors have?
 
#19
gio89 said:
and on the l-pad it looks like it is 6R/10R not 8R/10R. (its hard to see the number but i found a higher quality image of the crossover layout and it is a 6R in series and 10R in parallel.
Click to expand...
6R8/10R (- .67dB)
6R8/6R8 (- 1.64dB)
6R8/4R7 (- 2.86dB)
10R/10R (- 2.96dB)
10R/6R8 (- 4.06dB)
6R8/3R3 (- 4.23dB)
10R/4R7 (- 5.36dB)

5-10W series and 3-5W parallel should be fine.
Strassacker: Speaker Building, Components
 
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