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Help me convert old speakers to actives

have you had good results sealing with shelac ? I've thought of using shelac to seal wood things I make to try and avoid the grain swelling that seems to happen with every other method I've tried
Yes. It covers well and sands easily and perfectly (even by a first timer). But working time is very short, so use roller instead of brush. Also avoid going too thick as it tends to remain soft if thick and then clog in sanding.
 
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I call it ‘hand made in London. On a dining table’.
You did a very good job.

You also would have managed to get your own speaker without the existing monitor audio speakers perfectly.

It would also have saved you a lot of work, because you could then have aligned the speaker only to your acoustic goals - and not to the requirements of existing cabinets.
Next time.
 
Exactly!
I knew the cabinet will impose hard acoustic constraints, but I also thought that modifying vs new will make things simpler in the build stage. In my case that was not true. Building from scratch would have been easier. So the trade off did not happen.
 
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You did a very good job.

You also would have managed to get your own speaker without the existing monitor audio speakers perfectly.

It would also have saved you a lot of work, because you could then have aligned the speaker only to your acoustic goals - and not to the requirements of existing cabinets.
Next time.
I understood this project (I followed from the beginning) as self educating lecture, to start based on a commercial available speaker and 'do it all right' in refurbishing. The results until now are very promising (we have seen lots of other outcomes (or better: start an implode, here), my respect!
The now gained result looks very promising, but now: measurements and crossover design are on the table ....
 
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Why not? You managed the hardware very good, and with the software there are more than You want to will chime in ...
... the perfect speaker is not invented yet, but Your's may be very fine for Your purposes.
 
If you really want to do the crossovers "right" there is a great free CAD program called VituixCAD. It has quite a learning curve and you need to take "outdoor spinorama type" measurements as well as impedance measurements and then you can design the crossovers (it works for both active and passive). Lots of work but compared to "driving blind" trying to use "cookie cutter" crossovers that are never right you are bound to have better results. https://kimmosaunisto.net/Software/VituixCAD/VituixCAD_help_20.html
 
Forget about that -CAD stuff (that does not reflect real life in all it's facettes). Measure, trial and optimize.
Vituix is good to have a look on not yet existing projects if they may see the light of the world, but for real existing items (like Your speakers) we should deal with real facts than do 'calculations'.
 
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Forget about that -CAD stuff (that does not reflect real life in all it's facettes). Measure, trial and optimize.
Vituix is good to have a look on not yet existing projects if they may see the light of the world, but for real existing items (like Your speakers) we should deal with real facts than do 'calcualations'.
Respectfully disagree. The way VituixCAD works is that you have to measure the actual drivers in the actual enclosures first. They are very extensive full polar measurements taken outside on a turntable. You also take measurements of the actual impedance of your drivers in your enclosures. This information is then input into the program and then you start on the crossovers. Compared to trial and error it is very powerful with much better results.
 
Forgive my ignorance of the technical brilliance at "measurements taken outside on a turntable" ... and "measurments of the actual impedance of .. drivers":
First: it's raining outside, and my turntable is only able to handle vinyl disk inside (for other purpose inside there is the MM - Method).
Second: using a FA (active Plateamp) the impedance is out of interest.

Agreed I'm old fashioned, coming from changing coil, cap, resistor to find out the correct solution, but you can not tell the story that any simulation is better than reality?

What, you think, would 'shorten' the finding of optimum crossover in XCad compared to real life (expecting you have experience with digital xover)?
 
Forgive my ignorance of the technical brilliance at "measurements taken outside on a turntable" ... and "measurments of the actual impedance of .. drivers":
First: it's raining outside, and my turntable is only able to handle vinyl disk inside (for other purpose inside there is the MM - Method).
Second: using a FA (active Plateamp) the impedance is out of interest.

Agreed I'm old fashioned, coming from changing coil, cap, resistor to find out the correct solution, but you can not tell the story that any simulation is better than reality?

What, you think, would 'shorten' the finding of optimum crossover in XCad compared to real life (expecting you have experience with digital xover)?
The biggest problem for DIY speaker building is getting accurate measurements. Measurements taken inside are inherently inaccurate due to reflections from the walls even with gating and all the other tricks. That is why speaker companies use either anechoic chambers or a Kipple machine. For DIY the best we can do is take measurements outside as far away from any reflective surfaces as possible. The turntable I referred to is for the speakers (not your LP's) because you need to take measurements every 10 degrees off access for each driver so there is a lot of "turning" of the speaker (leaving the MIC stationary). The impedance measurement is used to confirm the resonant frequency of the drivers but as you say for active crossovers is less important than for passive. What is extremely powerful is than once you get these measurements into the CAD program you can experiment with different crossover slopes and crossover points and crossover styles and instantly get results not just "on axis" but also "off access" and "directivity" and much much more. It is simply not practical to take these advanced outdoor measurements on a trial and error basis. After you get one or several crossover designs you like in the program then you can go back outside and test them and optimise some more or use them. If you want to read more of what ViruixCAD can do and how to use it you can read through the documentation that I linked to.
 
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If you really want to do the crossovers "right" there is a great free CAD program called VituixCAD. It has quite a learning curve and you need to take "outdoor spinorama type" measurements as well as impedance measurements and then you can design the crossovers (it works for both active and passive). Lots of work but compared to "driving blind" trying to use "cookie cutter" crossovers that are never right you are bound to have better results. https://kimmosaunisto.net/Software/VituixCAD/VituixCAD_help_20.html
I am at this stage now. I have done the initial far field sweeps (indoors) and with some help managed to import the driver response into vcad. I find vcad challenging.
I am doing nearfiels this weekend and will try better far fields either outdoors or large room.
Then I will attempt to merge in vcad and model crossovers, then try in HFD and measure.
The mf/hf is already very good (subjectively), but I want to learn to verify it objectively.
Then lf/mf and lf on its own is not yet good.

Here are the sweeps. I was told they are of poor measurement quality.
 

Attachments

  • Baseline Tw 0-15-30-45-60.zip
    2.5 MB · Views: 30
  • Baseline Mid 0-15-30-45-60.zip
    2.6 MB · Views: 20
  • Baseline Woof 0-15-30-45-60.zip
    2.7 MB · Views: 20
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Ok, that indeed looks a little unexpected.
At what distance and vertical position did you measure, and are the other drivers, except the one that is measured, muted via HFD?
 
Ok, that indeed looks a little unexpected.
At what distance and vertical position did you measure, and are the other drivers, except the one that is measured, muted via HFD?
2m mic distance, at respective driver height, other drivers muted. Same REW level for all drivers. Woofers both playing. The room is 4m x 5.5m approx, so very small.
Which aspects are looking wrong and what are the possible/likely causes?
 
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