PR170M0 Appreciation Club: new member questions

[ultrachrome]

I've ordered a pair of PR170M0's and will be deciding on which ribbon to use. However, I'm completely lost deciding what to do for a woofer solution. There are so many options.

Goals:
- open baffle PR170M0
- use active 2-way crossover for woofers
- passive 2-way for mid/tweet
- high efficiency / play loud using relatively low power (15-25W) mid/tweet amp.
- woofer budget $600 to start

Equipment:
crossover: ESP 4th order LR 2-way active @ 500Hz
<500Hz: Adcom 545ii 100W/ch (150W@4ohm)
>500Hz: Dynaco ST-70 or DoZ or other lower power amp.

So with a 100W amp and $600 in woofers, what options do I have? I like the idea of dipole if I can avoid having to build a big heavily-braced cabinet.

A phased approach is also good. I have a sub so I don't need super low extension. But if I can later phase out the need for a separate sub with more power / more woofers / equalization, that would be great.

Or am I overanalyzing this too much? Maybe I should just by a cheap woofer and throw it in a box to have something to start with.

[thylantyr]

[QUOTE]Originally posted by ultrachrome
PR170M0's

Good choice

and will be deciding on which ribbon to use.

Choose wisely, don't go too cheap as you can have a
great sound system.

However, I'm completely lost deciding what to do for a woofer solution.

If you operate the PR170M0 at high pass 500hz then your
woofer needs to sound great up to 500hz. The best woofer
for this is a Lambda TD12X with faraday motor or the TD15X.

John from AE may be able to build you two of them, contact
him.

http://www.aespeakers.com/phpbb2/viewtopic.php?t=257

Make sure you get the faraday motor version as they can
operate clean up to 2khz so crossing them over at 500hz
is sonically pleasing.

These woofers work great in sealed and I think they work
excellent in ported too.

IB? Try this;

http://www.aespeakers.com/products.php

click store
click AE speakers IB15
http://yellow.mynethost.com/~bv12636...1e9901e1da7230

I would contact John to see if he can build a faraday motor
version of the IB. /hehe

I really don't know if he is still building these Lamdba woofers,
but he bought their inventory of parts last year. I would assume
he has parts to build them still.



If you want to do more research on the product, there is lots of
data here;

http://groups.yahoo.com/group/LambdaDrivers/

[ultrachrome]

I've sent John an email.

Anything that might be off-the-shelf?

[thylantyr]

Originally posted by ultrachrome
I've sent John an email.

Anything that might be off-the-shelf?

I'm always been keeping my eye open for woofers
that will sound good at the higher frequencies, ie up to
500hz or even greater and the only thing I can find is
TAD and Focal Audiom but those cost alot more than the
Lambda and I think the Lambda TD w/faraday motor is better


Anything else I find may not sound as good but may be
acceptable depending on how picky you are. One example
would be the cost effective Dayton woofers;

http://www.partsexpress.com/webpage....age_ID=114#ref

Weird idea.. What about dual 10" Dayton Reference woofers
per speaker box ?

http://www.partsexpress.com/pe/pshow...=295-368&DID=7

Looks perty with the phase plug

[ultrachrome]

Those do look sharp. Even two per side is not too bad on the wallet. A sealed box doesn't look too unwieldy. Ported might be.

Typically what types of features should I be looking for in a woofer when crossing over at 500Hz?

I don't really know exactly what I should be looking for in the graphed response other than flat response in the area of intended operation and any nasties beyond that range that might not be masked by the crossover. The Daytons look a little hairy above 1k. Will my 4th order LR pretty much take care of that?

Thanks.

[ThorstenL]

Konnichiwa,

Originally posted by ultrachrome
I've ordered a pair of PR170M0's and will be deciding on which ribbon to use. However, I'm completely lost deciding what to do for a woofer solution. There are so many options.

In my Pro-Audio Days we used them with an Electrovoice EVM15B or 15L or "lookalike/soundalike" far eastern copies.

Originally posted by ultrachrome
crossover: ESP 4th order LR 2-way active @ 500Hz

Bad choice. X-Over point is too high. Consider using a lower X-Over point (< 250Hz), a suitably large baffle and a low order X-Over. If you do your homework you can combine driver, baffle and a 1st HPF into a combination that offers a 4th order acoustical slope.

The Driver has a resonance aorund 120Hz and a Qt of 0.5, in other words without baffle rolloff you will have 120Hz/-6db. Make the baffle large enough and add a suitable 1st Order HPF and you can aim at 250Hz -6db and make the Woofer system to match. The woofer system needs to not go excessively low if you have a sub.

One option might be to build a fairly slim and tall open baffle (Triangle Octant style) using 3 - 4pcs 8"...10" Woofers as linearray and the the Ribbon & PR170M0 on top. If you select 8" drivers with a fairly high Qt & Fs you can run that without requiring much EQ and even as a completely passive speaker!

For fun I "fudged up" in my XLBaffle Spreadsheet a system with 3 X Audax HM210G6 in parallel as LF section and a PR170M0, all on the same baffle. The predicted response below:



As you can see, a simple inductor on the Woofer array (you do need impedance compensation or an active 1st order LPF) would allow the tree woofers to match the PR170M0 in the midbass equalised and to give an in-room -6db point (relative to 96db/2.83V/1m mean sensitivity) of around 50Hz, which should make matching a subwoofer easy.

The other extreme would be a Woofer with a large diameter, loads of throw but good behaviour up to >> 500Hz, which means any of the "wideband 12" or 15" Pro Audio drivers. The number is now legion, originally we would be talking JBL D/E/K130 or 120 and/or EVM 15B/12B. This would need active drive and a lot of EQ, but as you don't requite very low frequencies to be covered you can still get away with this easily.

Sayonara

[ultrachrome]

Kuei, I was hoping you'd chime in as you sort of prompted me to join in on the fun.

When you talk of EQ'ing, are you referring to fixing bumps in the response or dealing with OB rolloff? Or both?

When I compare an array versus a single larger woofer, the latter seems less risky if the attempt fails. I only have two woofers to shed instead of 6-8.

John of AE just responded. A pair of TD12X's would be $440. 6-8 HM210G6's from Madisound are $300-400. Both are easily within budget.

Another concern about a 5-6 driver speaker is managing the overall impedence so that the amp-of-the-week won't be brought to its knees.

The LR crossover is just something I have lying around. I can wire it as 2nd order. I'm not sure I've ever seen a 1st order active. I imagine it would be easy to build.

[thylantyr]

Originally posted by ultrachrome
Those do look sharp. Even two per side is not too bad on the wallet. A sealed box doesn't look too unwieldy. Ported might be.

Typically what types of features should I be looking for in a woofer when crossing over at 500Hz?

I don't really know exactly what I should be looking for in the graphed response other than flat response in the area of intended operation and any nasties beyond that range that might not be masked by the crossover. The Daytons look a little hairy above 1k. Will my 4th order LR pretty much take care of that?

Thanks.

Just like any other driver (tweeter, midrange, etc.), I think it's
hard to judge it's ability to deliver good sound just by looking
at the datasheets. But you may be able to get some hints
by the type of design. ie, the Lambda w/faraday motor was
specifically designed to be a 'wideband' driver not just a
subwoofer. You can read about the motor design here;

http://ldsg.snippets.org/motors.php3

The Apollo motor was once called the TD series on steriods,
the ultimate Lambda woofer, his dream woofer. The difference
between the faraday motor and the Apollo motor is;

Nick said
The Apollo drivers use 2 more Faraday rings on the outside of the voice coil.

The top plate (steel air gap) has been modified substantially, it has 18
threaded holes for all the mounting bolts and also the magnetic path shape
was changed slightly so we could lower the weight of the driver as well (we
removed steel from places it was not needed magnetically).

The Top Faraday ring is ~6" wide and 5/8" thick at its largest points. Its
inside dimension is held to a tolerance of 0.002" so that it is spaced just
a few thousandths from the voice coil. It pulls the heat from the top of
the voice coil directly and sinks it into the cast aluminum basket, which
is about 5 lbs of solid aluminum.

The Lower Faraday ring is spaced under the air gap and inside the magnet
stack. it allows a more linear inductance to xmax curve, and transmits any
heat picked up from the lower region of the voice coil into the top plate.

The Top Ring and the Top Plate (of steel) form a tight sandwich with heat
sink compound between them. And the Top Ring is a massive thick chunk of
aluminum that now completely connects the basket to the voice coil heat wise.

Both rings also force any flux movement to fall near to zero, especially
combined with the already massive copper ring and solid aluminum phase plug.

Other than that, they are exactly the same drivers.

I have collected ten Apollo motor TD15H's over the years
at $400-$500 each. They sound awesome. I bet the regular
TD w/farady will generate the same SQ level. $440 for a pair
is quite good considering that it's a great sounding woofer that
can play 'full range' very clean while offering really good bass
if you port the design. You might want to get the TD15's as
Nick claimed they are slightly better sounding than the 12's.

I've done alot of homework on these drivers and some folks
who used TAD woofers ($600-$700 each) say the Lambda is
equal or better in sound.

[thylantyr]

I'm not sure what you want to build.


T
M
W8
W8
W8
W8

W8 = 8" woofer

or

W8
W8
T
M
W8
W8

or

I would suggest;

T
M
W12

W12 = Lambda TD12 w/farady motor

or

better yet, the TD15 w/farady motor


Get a big ribbon tweeter;

http://www.madisound.com/neopro5i.html

$305 each, competes with the $500 AC version.

That would be pretty sweet 3 way design, simple.

Biamped -> sweet.


Look here;
Finally, my new LAMBDA-PHL-Esg3 speakers are done. Check them out.

Great tweeter
PHL 10" midrange
Lambda SB woofer

The PR170 midrange is great for the money and sounds almost
identical to the PHL1120 which cost alot more.

The TD series will give you better 'wideband' sound quality
than the SB series.

Your path to success is an easy road.

[ultrachrome]

I'm not sure what you want to build.

Yeah. Me, too. Whatever ensures the highest chance of success!

All those sound like cool ideas. However, $600 in tweeters might lower my woofer budget but not enough to rule out the Lambda's or Audax array.