PR170M0 OB dipole x-over points.

[AudioGeek]

ok...

i think i will go with 2 alpha15a for bass HF filtered at 200hz.

2 PR170M0 for mids to about 4k or so.

what should my baffle width be for these mids and where should i put the x-over point?

maybe 500Hz due to response of the alpha's?

(see MJK article about the Alpha15a's)

any help??

p.s. i really am looking for some mids that will work OB from 500 up to as high as possible then a supertweeter or something at top like a B&G dipole tweeter

[Rudolf]

The baffle for a 17 cm driver should not be too much wider than 2.2 times the cone diameter. This helps to prevent the development of side lobes. An OB width of 30-40 cm usually will support a 250-200 Hz crossover frequency. I found this almost perfect for my own combination of 5-6" mid and 15" woofer.

[badman]

500Hz is a good choice. I'm running the PR17OMO 350Hz 12dB/Oct now, and am very happy with it's undistorted output at that level (run to 5k, series first order XO to fostex FT17H at that point) My midrange baffle is quite small, fwiw, a trapezoid with dimensions no more than 16" in any direction.

[Rudolf]

Originally posted by badman
500Hz is a good choice.

My subjective impression when running the woofers that high: the imaging plane was lowered at times - low voices or instruments almost at floor level.

[Magnetar]

A pair is good to 300 ! This should sound great! The baffle need not be very wide, these have good coupling when used close together in the low mid.

[mikey_audiogeek]

Hi,
Got PR170M0 in OB's with P.Audio Sn15B 15" woofer and Beyma CP21F tweeter. 1st order series crossover at about 500Hz (2.5mH/47uF) with a 20 ohm resistor acros the PR170M0 to slightly pad down the level and help reduce the impedance peaks. I'm driving the whole shebang with a John Swenson design transconductance amp which has an output impedance of 22 ohms - gives the Sn15B flat response to 40Hz on 1200mm x 750mm baffles. Measurement showed flat response throught he crossover region, works for me.
Oh yeah - not rolling off the PR170M0 at the top, just adjusting the toe of the baffles to match with the Beyma which is brought in about 7K with a 3.3uF cap, level padded appropriately.
Next step is to double up on the mids of course!

Cheers,
Mike Spence

[BDP]

I tried various lowpass X-Over points with the PR170 and in the end I preferred no lowpass X-Over at all. I high passed the tweeter at about 8KHz. Some of the lower X-Overs measured better off axis but they all detracted from the sound.

This is a nice sounding midrange!!

BDP

[SamL]

Originally posted by mikey_audiogeek
Hi,
Got PR170M0 in OB's with P.Audio Sn15B 15" woofer and Beyma CP21F tweeter. 1st order series crossover at about 500Hz (2.5mH/47uF) with a 20 ohm resistor acros the PR170M0 to slightly pad down the level and help reduce the impedance peaks. I'm driving the whole shebang with a John Swenson design transconductance amp which has an output impedance of 22 ohms - gives the Sn15B flat response to 40Hz on 1200mm x 750mm baffles. Measurement showed flat response throught he crossover region, works for me.
Oh yeah - not rolling off the PR170M0 at the top, just adjusting the toe of the baffles to match with the Beyma which is brought in about 7K with a 3.3uF cap, level padded appropriately.
Next step is to double up on the mids of course!

Cheers,
Mike Spence

Hi Mikey,
Is the P Audio SN15B in OB or inside a box? How big is your box?

[AudioGeek]

so,

i could go with 2 emimence alpha 15a on a 20" wide baffle, and 2 PR170M0 on same baffle..

x-over 500Hz and run top end with no x-over on top.

tweeter in at 7khz or so.

2 alpha15 probably 96db.
2 pr170m0 at 100db.

got to pad down mids.

any idea on a good tweeter?? thinking B&G dipole..

what you think?

[SamL]

Hi AudioGeek,

I am also interested in the Audax PR170M0 and like you I read MJK article about the Alpha15a's and was thinking of using them both. However, I later read that Emimence alpha 15a can be is a bit 'slow' for Audax PR170M0. Its high QTS may have something to do with it. Hope someone will confirm this for you.
Below are a few discussion thread that worth reading.

All Eminence OB
Audax PR170MO...
http://www.diyaudio.com/forums/showt...13#post1353613
Sensitive Wide Range Open Baffles
WMTMW Open Baffles

Have fun