This thread will document a side project, of an active speaker conversion.   

 

I have a thing for Active speakers.  Have been using actives built by SGR for years, in my home theatre, and I just love them.  My HT cranks at really stupid SPL's at times, and the SGRs do a remarkable job, with their built in amps.

 

And, for years, I have had a hankering to do my own active speakers. But speaker building isnt my thing, and never will be.  I'm more of a configurer, than a builder.

 

So, I have been casually keeping my eyes on the second hand market of cheap speakers. Waiting for the right set to pop up, that will inspire me.  I wanted to find a multi driver speaker system, where i can perform a passive to active conversion.  Open them up and bypass the passive crossover network.

 

This week, I found something.  So, the project has officially begun.

 

For me, this isnt an end game project.  It's just a fun side project, to satisfy my curiosity.  

 

Here we go.......

 

 

 

 

Edited July 7, 20223 yr by Sentient

 

courtesy of facebook marketplace

Edited July 7, 20223 yr by Sentient

Per side, they are a 3 box integrated 4 way passive speaker system.   They stand 1.4m tall, and the veneer is quite nice.   😍

Edited July 7, 20223 yr by Sentient

There are 4 pairs of binding posts per side.  Beautiful, that saves me needing to add extras. 😍

Edited July 7, 20223 yr by Sentient

My first step, will be tri wire / tri amp the speakers, and do some measurements.

 

This is my initial test rig, using kit I had laying around.  

 

Edited July 7, 20223 yr by Sentient

Good project, @Sentient.  

 

I presume you are planning on doing some measurements of the individual driver responses ... so as to be able to plot the slopes and roll-off points of the HP & LP filters - so you can then copy these in a miniDSP or similar?

 

Andy

 

I have 2 yammy amps, i love Yammy's. ❤

 

The juicy one is an MX-830, which i'll use to drive the top/bottom bass boxes. 

 

And the other Yammy amp underneath, is a low powered amp, but is switchable between 2 way or 4 way amplification.  So, I'll use it to drive the middle tweeter section.

Edited July 7, 20223 yr by Sentient

The front end is a pi based Bossdac, running as a Roon endpoint.

 

There is a little Douk Audio tube preamp handling volume control duties. Love this little toy, it's a real surprise packet.  I didnt want to mess around with digital VC and potentially make a mistake.

 

The silver boxes on the left are Musical Fidelity buffers, that are currently distributing the audio to the amps.  These buffers have been unused for a good 7 years or more.  They wont hang around long, they're just for initial testing and measuring. 

Edited July 7, 20223 yr by Sentient

1 hour ago, andyr said:

I presume you are planning on doing some measurements of the individual driver responses ... so as to be able to plot the slopes and roll-off points of the HP & LP filters - so you can then copy these in a miniDSP or similar?

 

Gday Andy.   minidsp is likely.   But not initially.  

 

I'll certainly be measuring.  I plan to initially go old school, and use some electronic active crossovers.  I assume the speaker designer already found the optimal crossover points, and designed them into the passive network.  So i just have measure what the speakers do with the passive network in play, and replicate it (as a starting point).

 

Active testing will be done first with a Swamp 234XL active crossover,  which gives me 3 way stereo configuration, at a far more sensible pricepoint than 2 x minidsp's.  And if the swamp does the job and sounds ok, i may get a 2nd, and have 1 per side, for a 4 way mono active setup (on each side).

 

I'll likely get to minidsp in due course, but that is down the road.   I'm taking the slow road intentionally. 😇

Edited July 7, 20223 yr by Sentient

this pic, gives a sense of the speaker system size, standing alongside the test rig.

all unpacked and wired up.

each box in the speaker towers is individually amp'd.

have got the volumes matched across the 2 amps.

Edited July 8, 20223 yr by Sentient

Sounding really nice actually.

 

I plan to run-in the speakers for 100 odd hours over the weekend.

 

Before swapping out the buffers, for the Swamp electronic crossover, early next week.

Edited July 8, 20223 yr by Sentient

they sound darn good, but I cant wait to bypass the passive crossovers. 😎❤

23 hours ago, Sentient said:

Gday Andy.   minidsp is likely.   But not initially.  

 

I'll certainly be measuring.  I plan to initially go old school, and use some electronic active crossovers.  I assume the speaker designer already found the optimal crossover points, and designed them into the passive network.  So i just have measure what the speakers do with the passive network in play, and replicate it (as a starting point).

 

Active testing will be done first with a Swamp 234XL active crossover,  which gives me 3 way stereo configuration, at a far more sensible pricepoint than 2 x minidsps.

 

Why do you need 2x miniDSPs?  Sure ... if you are thinking 2x4s or 2x4HDs - but when I changed from 3-way analogue active to 4-way active (when I added a pair of subs to my 3-way Maggies) ... I bought a 10x10HD; this offers 8x analogue output channels.

 

23 hours ago, Sentient said:

And if the swamp does the job and sounds ok, i may get a 2nd, and have 1 per side, for a 4 way mono active setup (on each side).

 

Looking at the specs for the Swamp 234XL active crossover - yes, you can buy them very inexpensively.  But they seem to have very limited functionality, compared to miniDSP.  

 

Andy

 

13 hours ago, andyr said:

 I bought a 10x10HD; this offers 8x analogue output channels.

that looks like a good option.

 

unfortunately out of stock and cant be ordered, due to the chip shortage.

 

i'm forced to wait anyway, which suits my plans perfectly.   it's a step by step journey, that i plan to enjoy slowly. ✌

 

13 hours ago, andyr said:

Looking at the specs for the Swamp 234XL active crossover - yes, you can buy them very inexpensively.  But they seem to have very limited functionality, compared to miniDSP.  

 

why the shock face?  that's a bit ott, lol.    not sure i need phase tweaks, and i already have digital eq on the front end.    will see how the project unfolds, but as i said, am likely to end up using a minidsp or 2, i wasnt aware of the 10x10, ta. ✌

Edited July 8, 20223 yr by Sentient

5 hours ago, Sentient said:

Sounding really nice actually.

 

I plan to run-in the speakers for 100 odd hours over the weekend.

 

Before swapping out the buffers, for the Swamp electronic crossover, early next week.

 

bruuh that's a long weekend 😎

 

Are the individual boxes locked together, or just sitting with self-weight? ..they look pretty solid. And photo with grilles back on would be good to see.

 

Looks like a great project, thanks for sharing the journey.

 

Cheers

2B

10 hours ago, 2Brix said:

 

bruuh that's a long weekend 😎

Gday 2B.   haha, yeah, likely to bypass the passive crossovers next weekend.  I will,,,

1. run them for a few days.

2. measure each box individually

3. swap the buffers for the swamp, and replicate the crossover points, while the passive network is still in play.  i should be able to get it fairly close.

4. bypass the passive network, re-measure each box and fine tune the crossover points.

 

10 hours ago, 2Brix said:

Are the individual boxes locked together, or just sitting with self-weight? ..they look pretty solid. And photo with grilles back on would be good to see.

 

Self weight.  They are weighty, but I may need to look at modifying the bass boxes, if i get any resonances at higher levels?   

Edited July 8, 20223 yr by Sentient

Classy look with the grilles on too.  Nice to have that option for bgm and off-duty.

 

Will be interested to know the xover freq for each driver and what range the upper box is handling, and its weight.  If any resonance occurs you'd have a few options to address it (stiffness, mass, etc).  And depending on the thickness and quality of the panels there'd be ways of joining the boxes if that was desired and could be done neatly.  But for now, KISS :0)

 

 

On first rough measure, it looks like the top and bottom bass boxes are intended to sum for info up to 120hz, and they both roll away gently up to 250.   

 

The mid driver in the middle box, covers a big range from around 200hz upwards, blending with the bass boxes,

 

and tweeter looks to kick in at 6k.

 

Replicating what the passive network is doing, doesnt make sense to me.  I'll re-measure each driver without the passive filtering in play, and decide on crossover points.   

1 hour ago, 2Brix said:

 there'd be ways of joining the boxes if that was desired and could be done neatly. 

 

My back is a bit over moving around monster boxes. 🙃   I like that they come apart.   😇

Interesting, the "semi-wide band" mid range, and high handover to tweeter.

 

For the bass boxes i would have guessed the bigger box goes to 60-80 before roll off, and the smaller (top box) up to 120-150 before roll off.  Will be fun playing around and finding out what feels and sounds right.  And maybe having some "party mode" settings :0)

25 minutes ago, 2Brix said:

For the bass boxes i would have guessed the bigger box goes to 60-80 before roll off, and the smaller (top box) up to 120-150 before roll off.  Will be fun playing around and finding out what feels and sounds right.  

 

There are differences and similarities.

 

They both have stuff all below 40.  *shrugs

 

The bigger driver puts out more volume, and yes it starts to turn at around 80, but still has decent volume at 100.

 

The other bass box extends to around 110, before turning.  

 

and they both have a gentle roll off.  like a 1st or 2nd order roll off up to over 200.

 

I'm hoping once i remove the passive filtering, the top bass box will go comfortably to 200, with a bit of eq?   will see.   

With this type of inexpensive, no-name, Chinese speaker I would not be confident that the design makes any real sense 🙂   Having two bass bins with different drivers covering the same frequency band......it's going to be hard to work out a way to integrate them properly!  Maybe initially try to  design a 3-way system using just one of the bass boxes.   Muck around with the tweeter XO, try from 3k up. Can the Swamp do delay on individual channels?  You will need it if you want to get the XO's correct.

2 hours ago, RoHo said:

Maybe initially try to  design a 3-way system using just one of the bass boxes.   Muck around with the tweeter XO, try from 3k up. Can the Swamp do delay on individual channels?  You will need it if you want to get the XO's correct.

i'll play around with it.  no delays, 24db xover slopes, should be fine to play around.

 

i think my starting point will be:

* bottom bass up to 80hz,

* top mid bass 80-200,

* mid driver 200-3k

* tweeter above 3k. 

 

 

it's a play project. 🙂

Edited July 9, 20223 yr by Sentient