10" woofer to use with BMR in FAST?

[sharpi31]

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 :-)

[sreten]

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.

[sharpi31]

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.

[jerome69]

Originally Posted by sharpi31

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 !

Originally Posted by sharpi31

Do I need to go for a 4ohm woofer

no

Originally Posted by sharpi31

or could I also use an 8ohm unit?

yes

Originally Posted by sharpi31

What sensitivity of woofer should I aim for (both 4ohm & 8ohm)?

89dB

Originally Posted by sharpi31

What order crossover would be best? I'd prefer simple (1st order) if at all possible.

1st order

Originally Posted by sharpi31

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

Originally Posted by sharpi31

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.

Originally Posted by sharpi31

Many thanks in advance :-)

You welcome

[sreten]

Originally Posted by jerome69

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.

[jerome69]

Originally Posted by sharpi31

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

[jerome69]

Hi, I know what i write !
Did you read below SEAS curve (zoom of the frequency response) for the CA26RE4

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

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.

Originally Posted by sreten

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.