Diy center channel passive radiator

[Stones]

Hello,
For fun I decided to make a diy center channel , a more robust version of what was offered by boston acoustic with this series.

I have a Boston acoustic vr-m 9.2 surround sound .
Fronts - Vr-m 90 (towers)
Surrounds - vr-m 60 (bookshelf)
Rear surrounds - Vr-m 80 (towers)
Front height - vr-m 50 (small bookshelf)
Subs - dual svs sb-4000

I modeled my diy center after the Boston acoustic Vr-mc which was the matching center for this series of speakers .
I don’t have any parameters for the woofers so I had to guess, this is what I did, I took two Vr-mc centers ch speakers I had and built a box about two and a half times the volume.
I then used a crossover from a Boston Vr-m80 ( a two woofer one tweeter tower speaker ) . I checked the ohms on the woofers of a working Vr-m 80 I have and realized I would need to use 4 woofers wiring each pair in series to match the ohms of each single woofer In the tower (6.9 ohms) so they would work well with the crossover.
I had extra matching woofers a passive radiators .
So that’s four 5.25 woofers and four 5.25 passive radiators in the center ch.
Woofers in front and 4 pr’s In back.
Sounds pretty good.
My question is , when I use rice on woofer and test tones trick to determine the Tuning of the original Vr-mc center passive radiator so I could match it to the original center ch. it smooths out at 38z. Which I thought was very low for a center. So I checked a bookshelf in the same series . A ported 6.5” bookshelf and it smoothed out at 50hz.
When I checked my diy center it also smoothed out at 38hz.
Is 38hz to low ? Why would the bookshelf smooth out so much higher?
Should I try to tune it higher? Would taking away some volume(adding blocks of wood) accomplish this?

thanks for help.

 

[TLS Guy]

Hello,
For fun I decided to make a diy center channel , a more robust version of what was offered by boston acoustic with this series.

I have a Boston acoustic vr-m 9.2 surround sound .
Fronts - Vr-m 90 (towers)
Surrounds - vr-m 60 (bookshelf)
Rear surrounds - Vr-m 80 (towers)
Front height - vr-m 50 (small bookshelf)
Subs - dual svs sb-4000

I modeled my diy center after the Boston acoustic Vr-mc which was the matching center for this series of speakers .
I don’t have any parameters for the woofers so I had to guess, this is what I did, I took two Vr-mc centers ch speakers I had and built a box about two and a half times the volume.
I then used a crossover from a Boston Vr-m80 ( a two woofer one tweeter tower speaker ) . I checked the ohms on the woofers of a working Vr-m 80 I have and realized I would need to use 4 woofers wiring each pair in series to match the ohms of each single woofer In the tower (6.9 ohms) so they would work well with the crossover.
I had extra matching woofers a passive radiators .
So that’s four 5.25 woofers and four 5.25 passive radiators in the center ch.
Woofers in front and 4 pr’s In back.
Sounds pretty good.
My question is , when I use rice on woofer and test tones trick to determine the Tuning of the original Vr-mc center passive radiator so I could match it to the original center ch. it smooths out at 38z. Which I thought was very low for a center. So I checked a bookshelf in the same series . A ported 6.5” bookshelf and it smoothed out at 50hz.
When I checked my diy center it also smoothed out at 38hz.
Is 38hz to low ? Why would the bookshelf smooth out so much higher?
Should I try to tune it higher? Would taking away some volume(adding blocks of wood) accomplish this?

thanks for help.

There is so much wrong with all this, I just don't know where to begin. That is not anyway to design and build a speaker. You have to select the drivers, and know or measure their Thiele/Small parameters. Then you can consider the optimal loading for the drivers, and design the optimal enclosure with a software modelling program.

Next you must know the electrical characteristics of the drivers and their acoustic responses. Then you are in a position to start designing the crossovers.

End results are highly intolerant of even small mistakes. Speaker design is a very exacting process and NOT a shotgun hit and miss affair.

 

[Stones]

There is so much wrong with all this, I just don't know where to begin. That is not anyway to design and build a speaker. You have to select the drivers, and know or measure their Thiele/Small parameters. Then you can consider the optimal loading for the drivers, and design the optimal enclosure with a software modelling program.

Next you must know the electrical characteristics of the drivers and their acoustic responses. Then you are in a position to start designing the crossovers.

End results are highly intolerant of even small mistakes. Speaker design is a very exacting process and NOT a shotgun hit and miss affair.

Right , I acknowledged this much in my post.
Like I said I had the parts and the time so I gave it a try for the fun of it.
My question was really more about the low “tune” of both the original center channel and the diy center (38hz) as opposed to the bookshelf (50hz). Why so low on the center ch?
Both original and diy centers sound almost identical with the exception of the diy being able to handle louder volumes and has slightly more bass output.
I believe it’s because all the drivers are the same in all the speakers except the ohm rating is halved in the tower which is why I wired them In series to get the exact ohm rating.
I know it’s not ideal but it what I had to work with.