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Small 2-way speakers with linear on-axis and power response characteristics (Scan Speak and SB Acoustics drivers). H&V off-axis measurements included

MT_bassbone said:
Can all of the parts be obtained from Parts Express or is it better to order from Solen? Would tariffs apply if I am in the US?
Click to expand...

They have all the xover parts, in stock is another story. I did have to get a 12.5ohm resistor instead of a 12ohm but you can plug that change into the vcad project the designer shared and see that it makes no difference. I also opted for an 18awg inductor over 20awg for the 1.5mh becuase it's just what was in stock. The DCR will be different but not in a manner that will affect anything.

You can see my xover on post #636 in this thread on page 32.
 
TommyKoo said:
I finished my rear speakers a couple of weeks ago and I´m very pleased how they turned out. I built them with closed enclosure (little under 4 l) and mounted them to the ceiling. This time I used Kimmosto´s crossover because it takes less space and it turned out to be very close to the original in sound perspective. I tested the speakers in the front speakers position and bass was definitely weaker, but not as much i feared. The ceiling position on the other hand gives them noticeable bass boost and the sound is very close to the original. They are very good match in surround sound and now the sound field is uniform (the former rear speakers are Wharfedale Diamond 9.0sr). The response chart´s blue curve is the original speaker (with passive radiator). Measurement was taken with REW in the center of the room ( microphone distance 70cm).
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Congratulations on the successful modification. I was trying to replicate your results with a non-angled back. While I am getting good results within 1-2 db variation to the original design above ~100Hz, I still can't replicate your near-perfect match.
Could you please give us more details on your implemention? You mentiond the volume being little under 4l. Can you give us the exact measurements?
I was not able to get below 4.1 l (not considerung the space the drivers and the crossover take) because otherwise the crossover would touch the drivers. So maybe I need to redesign the crossover layout, to get a lower internal volume. On the other hand, my measurements did not suggest a siginicant difference between 4.1 l and 4.5 l (or even more), so I am not expecting lots of help from reducing the volume to say 3.9 l. What's your exact internal volume (not considerung the drivers and crossover)?
How much stuffing did you use?
 
Ktacos said:
They have all the xover parts, in stock is another story. I did have to get a 12.5ohm resistor instead of a 12ohm but you can plug that change into the vcad project the designer shared and see that it makes no difference. I also opted for an 18awg inductor over 20awg for the 1.5mh becuase it's just what was in stock. The DCR will be different but not in a manner that will affect anything.

You can see my xover on post #636 in this thread on page 32.
Click to expand...
This is what I was talking about before. Good to know it's a minor issue.
 
MT_bassbone said:
This is what I was talking about before. Good to know it's a minor issue.
Click to expand...
If you haven't ordered the xo parts, check JFcomponents.com. They have good quality components and are moving locations and currently have ridiculously low prices. But I don't know if they have all the parts needed for this design.
 
sebastian k said:
Congratulations on the successful modification. I was trying to replicate your results with a non-angled back. While I am getting good results within 1-2 db variation to the original design above ~100Hz, I still can't replicate your near-perfect match.
Could you please give us more details on your implemention? You mentiond the volume being little under 4l. Can you give us the exact measurements?
I was not able to get below 4.1 l (not considerung the space the drivers and the crossover take) because otherwise the crossover would touch the drivers. So maybe I need to redesign the crossover layout, to get a lower internal volume. On the other hand, my measurements did not suggest a siginicant difference between 4.1 l and 4.5 l (or even more), so I am not expecting lots of help from reducing the volume to say 3.9 l. What's your exact internal volume (not considerung the drivers and crossover)?
How much stuffing did you use?
Click to expand...
I re-measured the enclosure and the volume is very close to 4l with very generous internal bracing (I used 12mm birch plywood for making the speaker lighter) and crossover included. The overall gross volume of the box is 4,9l. The filling is 25mm thick polyester wool on every enclosure wall in the woofer compartment and the tweeter compartment stuffed full. I placed the crossover behind the woofer, but it was a snug fit (about 1,5 cm room between the magnet and crossover).

I didn´t want to throw my old Wharfedales away, so I made them new enclosures with the same style too and recapped the crossovers. The sound is nowhere near as good, but I guess they work ok in atmos height channel.
Wharfedale.jpg
 
XMechanik said:
Inspired by the purifi blog post on reducing THD (link) I did some experiments with the crossover.

The new traps
View attachment 425673(4.7uF,0.11mH/0.14ohm, 47ohm)

The test interface: two pairs of wires per cabinet, one is to insert the new trap (parallel resonance circuit in series with the midwoofer) and the other pair is for switching on and off the original trap (opens or connects the 0.82uF cap branch). Interface holes drilled in the least visible place, i.e. in the bottom panel. After the tests they will be filled with epoxy.
View attachment 425671

Impact on the system spl: +-0.5dB from the original characteristic (green). The lower curve: both traps enabled, the higher curve: only new trap enabled.
View attachment 425670 (5dB/div)

Finally, the impact on THD. The 2.3kHz THD peak was attenuated by 5dB so THD was reduced by almost half. With the new trap it's 0.8% 87dB. (In the original article the reduction was about 10 dB)
View attachment 425672(5dB/div)
Click to expand...

@XMechanik can I ask what power rating and type the 47ohm resistor is? Is it 5w metal oxide? I'm looking at making a small PCB for this modification.
 
Where is everyone getting the woofer? Part Express doesn't appear to have it and Madisound only has the coaxial version on the website. Any other locations in the US have it?
 
wineds said:
@XMechanik can I ask what power rating and type the 47ohm resistor is? Is it 5w metal oxide? I'm looking at making a small PCB for this modification.
Click to expand...
This resitor could actally have any power rating. The power dispation tool shows <0.1W for flat spectrum with 12.6V RMS at input (40W to 4ohm).
I think the resistor could be removed from the circuit entirely. It was to widen the peek of output impedance (at cost of decreasing it's maximum to some extent). The widening effect turned out to be marginal.
 
XMechanik said:
This resitor could actally have any power rating. The power dispation tool shows <0.1W for flat spectrum with 12.6V RMS at input (40W to 4ohm).
I think the resistor could be removed from the circuit entirely. It was to widen the peek of output impedance (at cost of decreasing it's maximum to some extent). The widening effect turned out to be marginal.
Click to expand...

Ok thanks I think I'll allow for it anyway. People can omit it if they wish.
 
TommyKoo said:
I re-measured the enclosure and the volume is very close to 4l with very generous internal bracing (I used 12mm birch plywood for making the speaker lighter) and crossover included. The overall gross volume of the box is 4,9l. The filling is 25mm thick polyester wool on every enclosure wall in the woofer compartment and the tweeter compartment stuffed full. I placed the crossover behind the woofer, but it was a snug fit (about 1,5 cm room between the magnet and crossover).

I didn´t want to throw my old Wharfedales away, so I made them new enclosures with the same style too and recapped the crossovers. The sound is nowhere near as good, but I guess they work ok in atmos height channel.
View attachment 491841
Click to expand...

I have some questions if you don't mind?

Can I ask how you calculated an internal volume of 4ltr for the sealed version? As in, why 4ltr and not 3ltr etc?

Also I'm trying to make sense on your numbers. If I calculate a box using the original baffle dimensions of 174 * 290mm and 12mm wood thickness, to reach an internal volume of 4L it would make the box 125mm deep. That works out at 6.3L gross volume and 4.03L internal volume not including bracing, drivers, XO etc.
Ignore - I think by gross volume you are saying the volume without subtracting bracing, XO plate etc.

How does the sound of the rebuilt Wharfdales compare to the Mechano23 sealed speakers?

Also for anyone buying components in Europe, I've used https://en.toutlehautparleur.com/ previously and can recommend.
 
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For anyone confused...Madisound carries four models of SB13PFCxxxx with four different model numbers. You want 4-ohms, not 8-ohms and not COAX. If you can find the 4-ohm version of the old "pincushion" frame for cheap somewhere (model without the "R" at the end), it will work, it is just a pain to flush mount.


SB13.png
 
Got the PCBs for the low distortion filter delivered today. Installed and both speakers are running again. I'll add more details over the next few days.
 

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Anyone know the minimum volume for a sealed cabinet where no changes are required to the XO?

Also, has anyone created a DXF file for the baffle?
 
essjay said:
Anyone know the minimum volume for a sealed cabinet where no changes are required to the XO?

Also, has anyone created a DXF file for the baffle?
Click to expand...

I don't believe changing the cabinet volume would require a xover change. You can always sim the driver in an enclosure in tools like vituixcad. Between ~5 liters and the stock ~9 liter box, there isn't much change. I can't imagine you could go much smaller than 5 liters because you won't be able to fit drivers and xover in the box.
 
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essjay said:
Anyone know the minimum volume for a sealed cabinet where no changes are required to the XO?
Click to expand...
What were you planning to do, exactly? The baffle dimensions (especially the width) should not be modified much; doing so will change the so-called "baffle step" and may require crossover changes. Cabinet depth is not as important, although the midrange directivity will change somewhat. Internal volume by itself influences the low-frequency corner (Fc) and Q, and in this case has little effect above 150Hz or so. Based on a quick enclosure simulation (including the DCR of the series inductors), a volume around 4L with a bit of stuffing should result in a Q around 0.7 and an Fc around 90Hz. 8L gives a Q around 0.55 and an Fc around 70Hz.
 
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