Diy center channel passive radiator

S

Stones

Audioholic Intern
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

TLS Guy

Audioholic Jedi
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.
 
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