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Help me convert old speakers to actives

So what to to?
Simply connect the white and red wire to the respective binding post. Thus the crossover is out of the way.
More complicated but necassary if you would want to go for a 2 1/2 way design: remove at least the tweater branch of the Crossover and insert a additional pair of binding posts to provide single point of connection per driver.

In any case: make shure the drivers are airthight to the front of the cabinet installed. If not simple window sealing tape may help.

Then we need the microphone and some amplification.
 
Crossover sheme (note1: both coils are 1 mH as I can't see any values for them on the images, note 2: Tweeter polarity is inverted responding to theory of 2nd order filters):

var1 XO-schema-1.png
 
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Crossover sheme (note1: both coils are 1 mH as I can't see any values for them on the images, note 2: Tweeter polarity is inverted responding to theory of 2nd order filters):

View attachment 371055
In the pictures, it looks to me like the shunt capacitor across the woofers is 8 uF.

Anyway, I would not try to replicate the passive crossover if going all active.
 
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More complicated but necassary if you would want to go for a 2 1/2 way design
Assuming there is baffle step loss, that is what I would do.

I would start with something like this:

Tweeter - 4th order or 8th order Linkwitz-Riley high pass.

Top Woofer - 4th order or 8th order Linkwitz-Riley low pass.

Lower Woofer - 1st order low pass to fill in the step loss of the top woofer.
 
Assuming there is baffle step loss, that is what I would do.

I would start with something like this:

Tweeter - 4th order or 8th order Linkwitz-Riley high pass.

Top Woofer - 4th order or 8th order Linkwitz-Riley low pass.

Lower Woofer - 1st order low pass to fill in the step loss of the top woofer.
+ 1.
But first some measurements to estimate the optimum for mid-high crossover frequency.
 
My initial recommendations would be,,,

You (OP) may easily make 3-pair of SP-driver-terminals in the rear of SP cabinet for fully active connection.

I highly recommend you to move/build the identical passive LC network in outer-larger "network box" using new higher audio grade capacitors air-core-inductors resistors so as to be served as "reference passive sound system" during the course of your coming fully active project. In this way, you can easily roll back the SP system into original passive configuration anytime during your "activation" exploration/adventure.

In such outer network box, the air-core-inductors should be well separated with each other and physically aligned in random directions minimizing/eliminating undesirable magnetic interactions between them. Even with these modification on LC network, you may hear some improvement in total sound quality, I believe.

Just for your info, I did it as my first step of my multichannel active project as you can find here on my project thread.
 
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I highly recommend you to move/build the identical passive LC network in outer-larger "network box" using new higher audio grade capacitors air-core-inductors resistors so as to be served as "reference passive sound system" during the course of your coming fully active project.
I think the crossovers that he already has in the speakers are sufficient for that.

He already has air core inductors on the tweeters.

The inductors on the woofers look to have iron powder cores. Although they may saturate faster than steel cores, they should have lower core losses. Although iron powder cores won't sound as good as air cores, they should sound better than the type of steel core inductors that commonly are used in speakers.

His electrolytic capacitors are fine for any comparisons he may make. Some people may hear a subtle difference between electrolytic capacitors and metalized film capacitors (at least they claim they do), but most people will not hear an audible difference. https://www.audiosciencereview.com/...tor-upgrade-in-crossover-is-it-audible.12287/
 
I think the crossovers that he already has in the speakers are sufficient for that.

I essentially agree with you for "preservation of original sound of passive SPs" as reference sound system.

The recommended first step for OP, therefore, wound be taking-out the LC-network out of the SP cabinet, and prepare simple "cabling board" for occasional/flexible interchange between "DSP-based active configurations" and "original passive configuration" for comparative objective measurement and subjective listening evaluations.

Of course, he need to install 3-pair of SP terminals on the rear of the SP cabinet directly connected to SP drivers.

Just for your reference, in my case, I prepared primitive but very robust reliable such SP cabling board beside the SP system including protection capacitors for my midrange, tweeter, super-tweeter (ref. here and here); with this cabling board, I can easily roll back the SP system into original passive LCR-network configuration.
 
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Looks like I have a few options or progressions for the conversion:

1 - use a two way Hypex and feed the two MF/LF drivers from one channel in parallel. This will be the nearest to the ‘as now’ configuration

2 - use three way Hypex and use one larger driver as mid and the other as woofer.
Question: Will I need to create a separate chamber for the woofer? In general, how do I calculate the volume of the chamber to suit a particular driver?

3 - three way Hypex, blank off the second driver and install a new side firing woofer at the bottom, also creating a suitable chamber for it.
 
My personal recommendation would be;

To start with, you may better to go into your option-1 (with no change of the cabinet) which is nearest to the "as now"; step-by-step progress from the original reference system would be recommended. (As I have suggested before, you should not change multiple parameters at once, I believe.)

Next, you may proceed to your option-2 with no change of the cabinet,

After that, if needed, option-2 with separate chambers for the two low-mid drivers. (I am personally rather reluctant to physically change the cabinet/chamber design, though.)

After finding better/best DSP XO/EQ/Delay(Time-Alignment)/Gain configuration, you probably may proceed to introduce a pair of active subwoofer also to be controlled by DSP.

Finally, if needed (if interested in), you may consider implementation of suitable high-efficiency L&R super-tweeters, to be driven by small-power but high-S/N low-distortion amplifier in relatively low gain; the Fq coverage may be (better to be) somewhat overlapped with tweeters. This will contribute better sound stage/image, I believe, even in low-gain operation.
 
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Just for your reference, let me share with you the details of my present DSP-EKIO's XO/EQ/Gain/Group-Delay/Phase-Inversion configuration; as I use -12 dB/Oct Linkwitz-Riley XO filters, you would please note that the "Invert" is checked for subwoofers and midrange(squawker) drivers for phase continuities (ref. here).
WS00006943 (1).JPG


By the way, have you already decided DSP software (I use EKIO on Windows 11 Pro OS) and fully-sync-multichannel-DAC (I use OKTO DAC8PRO in Pure-USB mode) to be used in your multichannel active stereo project?
 
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Just for your reference, let me share with you the details of my present DSP-EKIO's XO/EQ/Gain/Group-Delay/Phase-Inversion configuration; as I use -12 dB/Oct Linkwitz-Riley XO filters, you would please note that the "Invert" is checked for subwoofers and midrange(squawker) drivers for phase continuities (ref. here).
View attachment 371338

By the way, have you already decided DSP software (I use EKIO on Windows 11 Pro OS) and fully-sync-multichannel-DAC (I use OKTO DAC8PRO in Pure-USB mode) to be used in your multichannel active stereo project?
DSP will be whatever is available in the Hypex plate amp and their filter design software.
 
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Looks like I have a few options or progressions for the conversion:

1 - use a two way Hypex and feed the two MF/LF drivers from one channel in parallel. This will be the nearest to the ‘as now’ configuration

2 - use three way Hypex and use one larger driver as mid and the other as woofer.
Question: Will I need to create a separate chamber for the woofer? In general, how do I calculate the volume of the chamber to suit a particular driver?

3 - three way Hypex, blank off the second driver and install a new side firing woofer at the bottom, also creating a suitable chamber for it.
4 - replace the tweeter with a coax HF/MF (Seas for example has a small coax available) and use the two other existing drivers for LF in parallel wiring. Same question applies here: I will need to split the chamber into the MF one and LF one, so need to learn to calculate the required volume.

The Vas parameter I see on driver data sheets seems high and it is impossible to have such volume in my existing box.

I know that sealed boxes need smaller volumes so I can blank off the port if necessary to meet the volume requirements.

Could someone recommend a basic calculator that would tell me the required volume based on the driver?
 
DSP will be whatever is available in the Hypex plate amp and their filter design software.
OK, understood, even though I know little about Hypex plate amp and their XO software.
I hope (and believe) all the channels are fully in-sync, and the software has capabilities for tuning of time-alignments (group-delay settings) plus phase inversion On/Off at XO filters.
 
OK, understood, even though I know little about Hypex plate amp and their XO software.
I hope (and believe) all the channels are fully in-sync, and the software has capabilities for tuning of time-alignments (group-delay settings) plus phase inversion On/Off at XO filters.
The Hypex Filter Design is capable of these.
 
2 - use three way Hypex and use one larger driver as mid and the other as woofer.
Question: Will I need to create a separate chamber for the woofer? In general, how do I calculate the volume of the chamber to suit a particular driver?
In that configuration a separate chamber for the midrange would be best. If a bass driver and midrange driver are in the same chamber, the midrange driver will act as an un-tuned passive radiator in certain respects since it will not have applied power in the low frequencies to prevent that. That will add distortion, and will change the tuning of the cabinet's low frequency response.

Some woofer manufacturer's specify the ideal volume for their woofers. If not, enter the Thiel-Small parameters into a speaker simulator.

3 - three way Hypex, blank off the second driver and install a new side firing woofer at the bottom, also creating a suitable chamber for it.
Chances are that the chamber will be too small to get good bass response. I suspect the bass response would be worse than your current setup. Anyway, BEFORE making any cabinet changes, I strongly recommend making sure that the woofer you will be using will perform adequately in the volume you will be allocating for it. Some manufacturers specify this. If not, use the Thiel-Small parameters to calculate the volume or analyze the bass response in software.

4 - replace the tweeter with a coax HF/MF (Seas for example has a small coax available) and use the two other existing drivers for LF in parallel wiring. Same question applies here: I will need to split the chamber into the MF one and LF one, so need to learn to calculate the required volume.
You will be taking away air volume for your woofers, so the bass may be worse. Also, the existing port probably is designed for the existing air volume. You would want to select a new port length optimized for the new air volume.

If looking to go so far as replacing or adding drivers to your speakers, I suggest just selling your speakers and starting with a fresh design. EDIT: Design a cabinet optimized for the new drivers and hire a cabinet guy to make new cabinets, or try to find an available flat pack that is close to what you need.
 
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To start with just activate the 12 dB crossover. With the 3-way plate amp you can choose in the DSP setup same values for each woofer.
Next step would be the 2 1/2 design as described before.

In aspect of educational approach this will give sufficient insight of how speakers basically do their job.

For any further tweaks I would recommend a new construction from the scratch with new, not worn out drivers.
 
In that configuration a separate chamber for the midrange would be best. If a bass driver and midrange driver are in the same chamber, the midrange driver will act as an un-tuned passive radiator in certain respects since it will not have applied power in the low frequencies to prevent that. That will add distortion, and will change the tuning of the cabinet's low frequency response.

Some woofer manufacturer's specify the ideal volume for their woofers. If not, enter the Thiel-Small parameters into a speaker simulator.


Chances are that the chamber will be too small to get good bass response. I suspect the bass response would be worse than your current setup. Anyway, BEFORE making any cabinet changes, I strongly recommend making sure that the woofer you will be using will perform adequately in the volume you will be allocating for it. Some manufacturers specify this. If not, use the Thiel-Small parameters to calculate the volume or analyze the bass response in software.


You will be taking away air volume for your woofers, so the bass may be worse. Also, the existing port probably is designed for the existing air volume. You would want to select a new port length optimized for the new air volume.

If looking to go so far as replacing or adding drivers to your speakers, I suggest just selling your speakers and starting with a fresh design. EDIT: Design a cabinet optimized for the new drivers and hire a cabinet guy to make new cabinets, or try to find an available flat pack that is close to what you need.
Thank you for the info. Very useful.
 
To start with just activate the 12 dB crossover. With the 3-way plate amp you can choose in the DSP setup same values for each woofer.
Next step would be the 2 1/2 design as described before.

In aspect of educational approach this will give sufficient insight of how speakers basically do their job.

For any further tweaks I would recommend a new construction from the scratch with new, not worn out drivers.
Yes, starting to see this makes most sense - just get the amp and experiment with the existing drivers and cabinet (lowest cost, best learning per buck). Then get new drivers, reuse the amp and make new cabinet. I have thought of using somebody’s workshop but have not thought about outsourcing the whole cabinet building.
 
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