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Old 28th December 2012, 08:53 PM   #1
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Default 10" woofer to use with BMR in FAST?

I'm looking for a 10" woofer (to fit 230mm cutout) to use with a CSS BMR driver in an old pair of Wharfedale Glendale XP2 cabinets.

http://www.cotswoldsoundsystems.com/...5DD_N4Y_r1.pdf

The BMR will be installed in the (slightly enlarged) 4" hole used for the midrange driver in the original design. The woofer will go in the 10" hole. The 3" tweeter hole can then either be blanked off or fitted with a port, depending on the choice of woofer.

The BMR driver will have its own 2.2litre sealed enclosure (a round cardboard tube glued to the back of the 4" hole). The remainder of the cabinet volume for the woofer is just over 28litres.

My plan is to cross over to a more sensitive woofer to compensate for the baffle step of the cabinet (approx 380Hz). The BMR looks to be approx 89db sensitive at this point, although the sensitivity is given for 2.83V/1m as it's a 4ohm design.

My questions are:

Do I need to go for a 4ohm woofer or could I also use an 8ohm unit?
What sensitivity of woofer should I aim for (both 4ohm & 8ohm)?
What order crossover would be best? I'd prefer simple (1st order) if at all possible.
The BMR based designs I've seen to date (Naim Ovator and Rhythm King) are infinite baffle - would you expect this to work best here?
Can anyone recommend a suitable woofer?

Many thanks in advance :-)
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Old 28th December 2012, 09:12 PM   #2
sreten is offline sreten  United Kingdom
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Hi,

Allegedly 90dB+ in the top end requires a seriously efficient 10" or
more prosaically some attenuation and EQ of the mid.treble driver.

Can't see 1st order working well, series or parallel.

If it can you need a driver something like :
http://www.bluearan.co.uk/index.php?...emode=category
with AV filtering and subwoofers.

http://www.humblehomemadehifi.com/do...20Box_copy.pdf

Is a really good 10" (with the right x/o), 85dB (very normal)
sensitivity,though looks like BSC is being somewhat ignored.

rgds, sreten.
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Last edited by sreten; 28th December 2012 at 09:37 PM.
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Old 29th December 2012, 05:55 PM   #3
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Thanks Sreten. I'm tempted by the Scanspeak Discovery 26W 4ohm as it goes just a bit lower than the Dayton in a sealed box.

http://www.scan-speak.dk/datasheet/pdf/26w-4534g00.pdf

Playing around with crossover sims - hope to have a full recipe sorted by the end of the holidays.
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Old 29th December 2012, 07:06 PM   #4
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Quote:
Originally Posted by sharpi31 View Post
My plan is to cross over to a more sensitive woofer to compensate for the baffle step of the cabinet (approx 380Hz). The BMR looks to be approx 89db sensitive at this point, although the sensitivity is given for 2.83V/1m as it's a 4ohm design.
400Hz is low for a 4", 600Hz is better !


Quote:
Originally Posted by sharpi31 View Post
Do I need to go for a 4ohm woofer
no

Quote:
Originally Posted by sharpi31 View Post
or could I also use an 8ohm unit?
yes

Quote:
Originally Posted by sharpi31 View Post
What sensitivity of woofer should I aim for (both 4ohm & 8ohm)?
89dB

Quote:
Originally Posted by sharpi31 View Post
What order crossover would be best? I'd prefer simple (1st order) if at all possible.
1st order

Quote:
Originally Posted by sharpi31 View Post
The BMR based designs I've seen to date (Naim Ovator and Rhythm King) are infinite baffle - would you expect this to work best here?
yes

Quote:
Originally Posted by sharpi31 View Post
Can anyone recommend a suitable woofer?
28L is fine for the SEAS A26RE4
See The Madisound Speaker Store

Or for the SEAS CA26RE4X
H1316-08 CA26RE4X

Or Beyma SM110
http://profesional.beyma.com/pdf/SM-110%20NE.pdf
etc.

Quote:
Originally Posted by sharpi31 View Post
Many thanks in advance :-)
You welcome
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Old 29th December 2012, 07:17 PM   #5
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by jerome69 View Post
400Hz is low for a 4", 600Hz is better !

no
yes
89dB
1st order
yes

28L is fine for the SEAS A26RE4
See The Madisound Speaker Store

Or for the SEAS CA26RE4X
H1316-08 CA26RE4X

Or Beyma SM110
http://profesional.beyma.com/pdf/SM-110%20NE.pdf
etc.


You welcome
Hi,

All those answers are highly debatable or simply not right.

400Hz is fine for a 4" with a claimed high +/-6mm Xmax.
(Clearly intended to work down to 80Hz for modest AV.)

For an 89dB midtreble driver x/o for BSC the bass driver needs
to be the BSC level more sensitive, e.g. for 4dB BSC it needs
to be 93dB/2.83V, and that is far more likely with a 4 ohm driver.

There is little point with 4 ohm midtreble having 8 ohm bass,
that is completely the wrong way round for good design,
4 ohm bass and 8 ohm midtreble is generally better.

Bass drivers designed for vented boxes work far better in low
tuned vented boxes than sealed, as any sim will show, giving
quasi first order roll-offs even better for rooms than sealed.

rgds, sreten.
__________________
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When your only tool is a hammer, every problem looks like a nail - Abraham Maslow

Last edited by sreten; 29th December 2012 at 07:37 PM.
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Old 29th December 2012, 07:19 PM   #6
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Quote:
Originally Posted by sharpi31 View Post
Thanks Sreten. I'm tempted by the Scanspeak Discovery 26W 4ohm as it goes just a bit lower than the Dayton in a sealed box.

http://www.scan-speak.dk/datasheet/pdf/26w-4534g00.pdf

Playing around with crossover sims - hope to have a full recipe sorted by the end of the holidays.
This scanspeak will be not at ease in 28L

Don't see a lot of scanspeak good candidates
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Old 29th December 2012, 07:35 PM   #7
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Hi, I know what i write !
Did you read below SEAS curve (zoom of the frequency response) for the CA26RE4
Click the image to open in full size.
Quote:
The frequency responses above show measured free field sound pressure in 0, 30, and 60 degrees angle using a 28L closed box. Input 2.83 Vrms, microphone distance 0.5m, normalized to SPL 1m.The dotted line is a calculated response in infinite baffle based on the parameters given for this specific driver. The impedance is measured in free air without baffle using a 2V sine signal.
The A26RE4 is the same thing No BSC too and 89dB / 2,83V
Quote:
This classic paper cone has a wonderful roll off at 2000Hz. This is one of the only 10" drivers we know of that could be used in a 2-way by letting the woofer run full range without a crossover
The Madisound Speaker Store

Please read.

Not very agree with the rest of your text ...

Take a look to LX521, a 8" 8ohms blends with a 4" 4ohms or to NaO Note II RS
http://www.linkwitzlab.com/LX521/Description.htm
http://www.musicanddesign.com/NaO_No...S_Details.html

rgds.


Quote:
Originally Posted by sreten View Post
Hi,

All those answers are highly debatable or simply not right.

400Hz is fine for a 4" with a claimed high +/-6mm Xmax.
(Clearly intended to work down to 80Hz for modest AV.)

For an 89dB midtreble driver x/o for BSC the bass driver needs
to be the BSC level more sensitive, e.g. for 4dB BSC it needs
to be 93dB/2.83V, and that is far more likely with a 4 ohm driver.

There is little point with 4 ohm midtreble having 8 ohm bass,
that is completely the wrong way round for good design.

Bass drivers designed for vented boxes work far better in low
tuned vented boxes than sealed, as any sim will show, giving
quasi first order roll-offs even better for rooms than sealed.

rgds, sreten.

Last edited by jerome69; 29th December 2012 at 07:48 PM.
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