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Old 12th September 2012, 09:27 AM   #11
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By having the woofers on the same plane , a big surface , you lose the perception of the two different sources . It might be doable for something like a mono sub ; still you have ruined a boundary and transferred lots of vibrations to the structure .
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Old 12th September 2012, 07:43 PM   #12
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Quote:
Originally Posted by AndrewT View Post
15" wide seems more like a mid range OB.

10' wide is a bass OB.
Or better, a true infinite baffle. i.e. inserted into the wall separating two rooms. The other "room" can be the basement or the loft.
It is for midrange and not for bass.

Its a 2 way trapezoid needing no real output under 80hz. I have subs and I'm happy with them.

The size has been altered to be 12" wide at the top and 15" wide at the base very similar to an apogee stage sitting on a rectangular base.
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Old 12th September 2012, 07:46 PM   #13
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Quote:
Originally Posted by picowallspeaker View Post
By having the woofers on the same plane , a big surface , you lose the perception of the two different sources . It might be doable for something like a mono sub ; still you have ruined a boundary and transferred lots of vibrations to the structure .
see post 9. its not a sub
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Old 12th September 2012, 08:42 PM   #14
Rudolf is offline Rudolf  Germany
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This is the Qts-induced roll-off (around Fs) of the driver in infinite baffle:
guete_neu.gif
The-x axis is divided into multiples of the drivers Fs: 2.0 is double Fs, 0.50 is half Fs etc. You can easily see how a low Qts driver rolls off at higher frequencies than a driver with Qts=1. The 6dB dipole roll-off has to be added to this.
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Old 13th September 2012, 08:45 AM   #15
AndrewT is offline AndrewT  Scotland
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Spin,
you confused me by stating
Quote:
bass roll off
Now I understand.
But why did it take 12 posts?
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Old 13th September 2012, 04:43 PM   #16
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Quote:
Originally Posted by AndrewT View Post
Spin,
you confused me by stating
Now I understand.
But why did it take 12 posts?

lol, because you chose to answer the question you wanted instead of the one I asked in the first post.....

I asked what was the rate of roll-off of a driver in an open baffle?

Quote:
Originally Posted by SpinMonster View Post
Sealed subs are 12db

Ported can vary but 4th order is 24db

What is an open baffle woofer roll off?

I'm looking to use a 7" thats FS 35hz w/Qts of .45 so it starts to roll off at 77hz but how steep? It s going to be used with multiple subs but Im trying to model the midbass. Is my math off?

Any help appreciated.
I didnt ask about baffle width or what was the best sub configuration.

Since the first post also stated it was a 7" and the FS/QTS, it stated the exact application was midbass and specifically stated that my subs were separate from this application. Its all good tho.

Last edited by SpinMonster; 13th September 2012 at 04:53 PM.
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Old 13th September 2012, 04:45 PM   #17
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Quote:
Originally Posted by Rudolf View Post
This is the Qts-induced roll-off (around Fs) of the driver in infinite baffle:
Attachment 301036
The-x axis is divided into multiples of the drivers Fs: 2.0 is double Fs, 0.50 is half Fs etc. You can easily see how a low Qts driver rolls off at higher frequencies than a driver with Qts=1. The 6dB dipole roll-off has to be added to this.

Answers everything and ties it in. Thank you.
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Old 13th September 2012, 05:29 PM   #18
sreten is offline sreten  United Kingdom
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Hi.,

The ultimate roll-off is 18dB/octave.

However excursion follows the driver infinite baffle response, (12dB
/octave) and the extra 6dB of baffle loss per octave chucks away driver
excursion, it is not just a simple manipulation of response, it is a loss.

The response can be EQ'd to anything you like, the real issue is SPL
capability at 80Hz with narrow baffles, it will be very poor compared
to boxes, baffle roll-off is a SPL loss, not the response of the driver.

rgds, sreten.
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Last edited by sreten; 13th September 2012 at 05:38 PM.
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Old 13th September 2012, 05:55 PM   #19
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Quote:
Originally Posted by sreten View Post
Hi.,

The ultimate roll-off is 18dB/octave.

However excursion follows the driver infinite baffle response, (12dB
/octave) and the extra 6dB of baffle loss per octave chucks away driver
excursion, it is not just a simple manipulation of response, it is a loss.

The response can be EQ'd to anything you like, the real issue is SPL
capability at 80Hz with narrow baffles, it will be very poor compared
to boxes, baffle roll-off is a SPL loss, not the response of the driver.

rgds, sreten.
Yes, I'm aware but its a test build to see how my set-up works with speaker location and the dipole effect. I have space but its a home theater so first to see if dipoles work in the locations I have then a RD50 with 6-8"drivers (dayton subs with 9mm excursion) crossed at 500 or so with the same 80hz low end would suffice. If it doesnt cut it, it will be a hybrid system.
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Old 17th September 2012, 03:29 AM   #20
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Default OB

Quote:
Originally Posted by SpinMonster View Post
Yes, I'm aware but its a test build to see how my set-up works with speaker location and the dipole effect. .....
Hi there SpM: Just ran a SPL check on an experimental OB (18" curved to 16.25") Uncalibrated generator, DVM and SPL meters: 2.83v:
130hz-70db, 140hz-65.8db, 150-58db, 160hz-71.4db, 170hz-75.3db, 180hz-76db,
190hz-78db, 200hz-78.8,300hz-84db, 400hz-8.3db, 500hz-85.2, 1k-84.4db, 1.5k-97.5db
2k-91db, 3k-97.2db, 4k-97.3db, 5k-97.4, 6k-97.5db, 7k-82.2db, 8k-87.5db, 9k-87.5db,
9k-87.5db, 9.3k85.1, 10k-62.8db. Since I intend to cross over to the bass unit around 150hz, I did not record the fall off below 130hz. ...regards, Michael
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