three-way speaker conversion to four-way active

[Urotdukidoji]

Hello, I have two diy three-way speakers, with two woofers, one 8" and one 10" for the bass line.
Thinking about making the 10" woofers active with miniDsp and hypex nc 500.
What cut-off do you recommend for the fourth channel, knowing that the current cut-off is at 450Hz and the speaker goes down to 30Hz?

 

[DVDdoug]

What? The 8 & 10 cross-over at 450?

Is the 4th frequency band a subwoofer? 80Hz is "standard" for subwoofers and that would be good if you ever want to use it for the "point one" LFE channel in movies. (You need a an AVR other surround processor to get the LFE. It's not included in the stereo downmix.)

 

[Urotdukidoji]

8 and 10 now work as one, 450 is between the bass track and the mid track, 5

 

[Urotdukidoji]

My system is 7.2, there are already two 12" subwoofers.
activate the 10" ones, I don't know if it can be considered a "semi-active" bi-amplification.
The reality is that I bought a stage that I didn't need... and now I don't know where to use it

 

[alex-z]

In an ideal 4 way I would recommend the woofer be 12-15" and crossed at 150-200Hz. That way you have enough linear excursion to blend in the subs around 40Hz.

Are the 8 and 10" sharing cabinet volume? It is pretty unusual that you would have two different size of woofer with the same crossover.

 

[Urotdukidoji]

In an ideal 4 way I would recommend the woofer be 12-15" and crossed at 150-200Hz. That way you have enough linear excursion to blend in the subs around 40Hz.

Are the 8 and 10" sharing cabinet volume? It is pretty unusual that you would have two different size of woofer with the same crossover.

The speakers were given to me by a co-worker who updated his system, today he explained its configuration to me,
I have been manufacturing them for 17 years, active in all four ways, they have three separate cabinets, a tweeter and a midrange in one, an 8" bass in another, sealed, and a 10" subwoofer in bass reflex.
I try to sell them and change them to passive, so there is the strange configuration... I guess.
These speakers sound like they are bigger than my Swissonic x8, they fill the entire space...it doesn't make sense to me.

 

[Urotdukidoji]

this would be, I'll look inside

 

[Putter]

FWIW these appear to be a highly modified JBL Ti 6k speakers (https://www.canuckaudiomart.com/details/649852919-jbl-ti-6k-speakers/) with a different midrange and tweeter mounted on a wood plate over the existing holes. Also apparently a 10 inch woofer is substituting for the 8 inch woofer. The best action IMO would be to measure them to determine what mods might be useful. If you're trying to sell them you could attempt to restore them to their original condition although that might not be cost effective
It is very difficult to sell modified speakers due to the lack of information.

 

[alex-z]

Looking at the pictures, a number of basic design principles such as flush mounting the tweeter and keeping the mid close to the woofer have been ignored. Fixing that stuff takes priority over updating the crossover.

Running the 10" woofers as active does make sense. Having a sealed 8 and ported 10" on the same crossover doesn't make sense given their different bass rolloff behaviour.

 

[Urotdukidoji]

FWIW these appear to be a highly modified JBL Ti 6k speakers (https://www.canuckaudiomart.com/details/649852919-jbl-ti-6k-speakers/) with a different midrange and tweeter mounted on a wood plate over the existing holes. Also apparently a 10 inch woofer is substituting for the 8 inch woofer. The best action IMO would be to measure them to determine what mods might be useful. If you're trying to sell them you could attempt to restore them to their original condition although that might not be cost effective
It is very difficult to sell modified speakers due to the lack of information.
View attachment 353296

They are not to be sold, they were given to me and I want to make them work, if possible, if they give me a lot of headache, they will return to their owner.

Those JBLs look too refined to be these...maybe you want to imitate them?

 

[Urotdukidoji]

I have measured (I don't know if) each controller separately and one from MLP and from your response I think that a fourth way is missing.

I have also looked inside them, and they are like a passive three-way sealed monitor, placed on top of a subwoofer without a filter and without an amplifier, all in the same cabinet.
sorry for the drawing...
If something doesn't make sense, I apologize, I write with a translator
The 10 woofer would work as a subwoofer, but it wouldn't make sense to me, I have an AV receiver and I cut all the channels at 80Hz.
I already have two 12" subs and if I make these work, they will be four subs, but does it make sense for subwoofers that cannot be varied in position?
It also seems that they don't even measure well.

 

[Urotdukidoji]

Looking at the pictures, a number of basic design principles such as flush mounting the tweeter and keeping the mid close to the woofer have been ignored. Fixing that stuff takes priority over updating the crossover.

Running the 10" woofers as active does make sense. Having a sealed 8 and ported 10" on the same crossover doesn't make sense given their different bass rolloff behaviour.

The middle near the woofer, does it refer to middle below and tweeter above, rotate them 180°?
What effect does the tweeter have between the woofer and the midrange?
ask from ignorance
Embed the tweeter, it is a job that I have pending

 

[alex-z]

The middle near the woofer, does it refer to middle below and tweeter above, rotate them 180°?
What effect does the tweeter have between the woofer and the midrange?
ask from ignorance
Embed the tweeter, it is a job that I have pending

Yes, rotate them 180 degrees. With the mid closer to the woofer they will have superior time alignment, meaning their energy is summed over a broader physical range.

The current tweeter mounting is problematic not because its height but because of the diffraction, both from the tweeter flange itself protruding, and the wooden block that holds them sitting above the baffle face. It also looks like the tweeter could be moved about 1" closer to the mid, which again would improve time alignment.

Having the additional 10" subwoofers should be beneficial, even with the inflexible placement. They can be used to reduce seat to seat bass variation.

Multi-Sub Optimizer Freeware for Multiple Subwoofers

Optimize bass performance of multiple-subwoofer audio systems. Reduce seat-to-seat frequency response variations.

www.andyc.diy-audio-engineering.org

Not all channels in a home theatre setup need an 80Hz crossover. If your speakers and room acoustics allow then 60 or even 40Hz is acceptable. Typical AV receivers use 12dB high-pass filters, moving the crossover point lower can result in improved spatial cues from the mid-bass region.

 

[Urotdukidoji]

Yes, rotate them 180 degrees. With the mid closer to the woofer they will have superior time alignment, meaning their energy is summed over a broader physical range.

The current tweeter mounting is problematic not because its height but because of the diffraction, both from the tweeter flange itself protruding, and the wooden block that holds them sitting above the baffle face. It also looks like the tweeter could be moved about 1" closer to the mid, which again would improve time alignment.

Having the additional 10" subwoofers should be beneficial, even with the inflexible placement. They can be used to reduce seat to seat bass variation.

Multi-Sub Optimizer Freeware for Multiple Subwoofers

Optimize bass performance of multiple-subwoofer audio systems. Reduce seat-to-seat frequency response variations.

www.andyc.diy-audio-engineering.org

Not all channels in a home theatre setup need an 80Hz crossover. If your speakers and room acoustics allow then 60 or even 40Hz is acceptable. Typical AV receivers use 12dB high-pass filters, moving the crossover point lower can result in improved spatial cues from the mid-bass region.

My idea is to remove the top wood and make the entire front new with a 22mm MDF board superimposed on the existing one, to reach a thickness of 40mm, flush and bring all the drivers closer to each other, flip the treble and midrange ones (hugely grateful alex-z)
and if the volume of the 8" cabinet allows it, I will reduce the height.
I don't know if it makes sense to have so much empty space up there...
first quickly to see if everything is going well.
I already use MSO and rephase on my system, very good software

I will try different cross points, the 80hz thing will be because of the Thx certificate that I have in my head....

 

[Urotdukidoji]

I understand that adding more absorbent to a ported cabinet increases the virtual volume.
In a sealed cabinet is it the same?
If I reduce the volume of the 8" enclosure, can it be compensated with absorbent material?
In every way I must find the way to calculate it.