Raven / Scan Speak Monitor

[herm]

I’m making my first attempt at building speakers. Here’s what I have in mind:

Small 2 way, Raven R1 ribbons and Scan Speak 15W/8530K01 mid-woofs.

Active crossover, Linkwitz-Riley 24dB to protect the ribbon.

Win-ISD graphs a 9.1 liter sealed for F3 around 60hz

Any problems so far?

Raven's already purchased and I'm just about to pull the trigger on the Scan Speaks....

[Per Nielsen]

Are you sure raven and scan-speak is a good combination, they are very diffrent in playing style
by the way there dosent seem to be any problems, but im not sure it would sound very good.

[redrumjoe666]

It would be an interesting experiment. I think if you built the enclosure properly, with nice large radiused edges, you could get a nice sounding pair out of it. The R1's are a little aggressive, but I don't think the combo would sound bad.

-Joe

[cocolino]

Hi herm,

Both of the two drivers You intend to use are truly excellent by it`s own IMO.
I don`t have own experience with that particular Scan-Speak model but for a 2-way system and combining with a Raven R1 this appears to me being one of the few promising choices (maybe also one of the Jordan`s full range drivers could be an alternative).
This really might become a very interesting project.

Only one thing I`d like to mention and You should keep in mind IMO:
Altough the spec. sheet says the Raven R1 can be used starting from upwards 2kHz (and the frequency response is reasonable well extented down into that range) my experience with ribbons of this size is to cross them as "high as possible" because of distortion issues. Unfortunately distortion graphs (at different drive levels) are hardly found in ribbons spec. sheets (maybe because they would look not so nice).

Although basicly a good idea, even a high slope x-over (as You want to use) might not completely prevent the ribbon to produce higher distortion (compared to a good dome tweeter) in his lower operating range when actually crossed at around 2kHz.
My first guess therefore would be not to cross below let`s say around 3,5kHz - 4kHz (or even somewhat higher if the Scan-Speak permits that). Probably this is near the upper edge of what the Scan-Speak is able but IMO You should make use of it to as much extend as possible.

As You intend to drive active, anyway experimentation with the x-over point (and slope - don`t limit Yourself on a predetermined filter type - experimentation & measurements combined with extended listening of different filter set-ups is announced - it might become a long journey) is quickly done without spending much money on many big & expensive passive x-over parts (that`s only one of the aspects why I love the active way so much).

Good luck & happy building!!

[herm]

Thank you for your responses, Per, Joe & Cocolino.

Per – Thanks for the advice on matching. I’ll let you know how it turns out.

Joe – the first cabinet will be an ugly, square box. Once I have experimented with it, I will get a nice cabinet made like this:

http://mywebpages.comcast.net/kidder...slam_alpha.htm

I was told that Bob at http://quicksitebuilder.cnet.com/wrnch2/ can provide this CNC work.

Cocolino – where do you live? I was stationed in Bayreuth (actually Bindlach) for 2.5 years. I would sure like to drink some Maisel’s hefewiezen again!

The reason I picked the Scan Speak is because it can go high enough to cross at 3.5 kHz or maybe even 4 kHz.

I will start designing the active cross soon.

[herm]

OK, here's my first attempt at building an active cross, and
posting an image.



I am trying to build a block diagram first. Is there anything
I should add to this XO?

How about something to tame the rising response of the scan speak over 1 khz?

An RF filter like Linkwitz uses?
http://www.linkwitzlab.com/xo_eq.htm

Is the level adjust going to be enough for the difference in driver efficiencies?

Should I just put one level adjust (like +5dB) on the mid-woof?

Any comments appreciated.

[RobWells]

Hi Herm,

I thought the RF filter was to do with Radio Frequency interference - I think you'll need the shelving low pass filter(also on the Linkwitz site) to tame the rise. (I'll be using this on my 15W/8530K00) mids - nearly the same speaker, but with the revelator tweeter. (x/0 at 3000)12Db/oct. ESP boards.

What are you doing about time alignment of the drivers? Linkwitz also has an op-amp based delay on his site..

If it's a 2-way are you going to be using a sub? - It may sound a little light otherwise..

I also considered the Raven, so I'll be very interested as to what you think of your speaks, once they're done. Keep us updated!

Oh, and good luck aswell!

Rob

[herm]

Rob;

Do you think it is worth the trouble to add an RF filter? Maybe I will try without and add later.

I think the shelving lowpass is needed. When we get around to calculating values, let's compare notes.

Speaking of calculating, how much tweeter delay do I need for time alignment? I don't know how much is necessary (or if it's the mid that needs delay, for that matter!)

I will use a sub for now, but my long term goal is to add a woofer.

-herm

[RobWells]

Hi Herm,

I'm not going to use an RF filter, but I can't advise as to whether you should. Is RF a problem in the US compared to the UK? I don't know... I'll bet someone who reads this does though!

""Speaking of calculating, how much tweeter delay do I need for time alignment? I don't know how much is necessary (or if it's the mid that needs delay, for that matter!)""

It should be the tweeter, but I don't know much about ribbons..

Hehehee This subject is being discussed here:

driver's acoustical center


and here:

Time alignment question

and here:
Acoustic centres of drivers/measuring

I'm waiting for the Joe D'Appolito book to turn up before I start properly, as I'm still a week or 2 from finishing my bass units..
The loudspeaker cookbook mentions a little about this, but not enough to be truly helpful..

Also, I'll be measuring my drivers after breaking them in for a bit (I'll use my bass cabs as speaker stands with my b+w 602's on top, and the x/o from my HT amp for now), and then calculating the x/o from these measurements.. Most people here don't have much faith in the published specs

Sorry I can't be more specific. Hopefully I'll have some measurements in the next 6 weeks or so (I'm about to move house so can't do too much at the moment.)

Cheers

Rob

[RobWells]

Should have added this too:

http://sound.westhost.com/project09.htm

May be of help.

Rob