Scan-Speak 7" Revelator

[gmed]

Im calculating the box volume and port size for the Scan-Speak 7" Revelator 8 ohm 18W/8831G00 or the 18W/8531G00, and Im coming up with a Box volume of 46L, F3 29.8 Hz, ported with 5.08cm x 10.3cm. At 21 Liters, Im getting an F3 of 42.7Hz with a port 5.08cm x 15.4cm. Can a 6.5" really go this low? I think I would be happy with an F3 of 42 Hz. This seems to be a very big volume for a 6.5". Am I doing something wrong? can I go smaller?

Based on Madisound.com "The 18W/8531G should have an F3 of about 50Hz sealed and 35Hz vented".

TECHNICAL DATA:
Sensitivity 2.83V/1M 87dB
Free air resonance Fs 27.5 Hz
DC resistance 5.8 ohm
V.C. inductance 0.35 mH
Power 70W
Effective cone area 150 cm2
V.C. diameter 38 mm
VC height -
Air gap -

Lin. & max. excursion ±6.5 / ±11 mm
Air gap flux density -
Force factor BL Product 6.7 Tm
Moving mass incl. air 15.5 g
Net weight 1.75 kg
Vas 61 ltrs
Qms 5.0
Qes 0.39
Qts 0.36


What do you guys think?

[TacoD]

Sweetspot for this woofer is 22 liter, this information was provided by the designer of the woofer (on a Danish forum). Almost every Scanspeak woofer is optimized for LF extension,(heavy cone, light suspension), this results in a larger Vas.

[gmed]

So would I be OK with 22 Liters?

[TacoD]

Yes, read this pdf from Troels, he discusses the cabinet and tuning.

You can make a test cabinet, to try the tuning if you're not certain. But from my point of view it makes sense to use the advise from Scanspeak.

[JonMarsh]

Thanks for posting the link to the PDF. I've always thought the D3806 might mate well with the 7" SS this way-- but it's an expensive speaker!

28 liters sounds about right to me... the 0.75 cu ft PE cab does that, the RS180 works very nice in it, too. I'm sure the Revelator would also if one wants to try for a little different bass extension (one must remember the difference between gross and net- net is what determines the acoustical properties, but you need the larger gross because of the driver volume, port volume, crossover volume, damping, etc.

Personally, I think a 10 -14 kHz crossover for the dome mid and tweeter is NOT the way to do a three way with these driversr, but using conventionial crossover approaches pushing the crossover points this far apart to aovid interactions would "seem" to be necessary.

Still, there's a lot of good info in the article, and stuff one could use as a "jump off point" to a nice design.

I'm looking at retrofitting my M8ta's to a similar concept with the RS52, but trying the Duelund crossover approach. Got my fingers crossed. Too many ideas and not enough time, as usual. That will wait until spring or so I imagine.

[CraigJ]

Jon Marsh wrote:

That will wait until spring or so I imagine

A bunch of us are plotting a mass mailing campaign to your boss, for an extra two weeks off for you. We are working on a medical excuse; let's use the bad disc issue, no lifting, can't assist in corporate move, must stay home We would go to Evil Twin for advice, but he seems to have your busy schedule, it's a mystery, go figure.

Anyway, trying to visually fit the NS10-513-4A 10" Subwoofer, with RS52 and RS28 or D26NC55, into the M8ta type box. Isis/M8ta 8O Ah, winter projects.

Cj

[JonMarsh]

Anyway, trying to visually fit the NS10-513-4A 10" Subwoofer, with RS52 and RS28 or D26NC55, into the M8ta type box. Isis/M8ta 8O Ah, winter projects.

Cj

Well, now that's an interesting idea... the existing M8ta would be hard to honk out for the 10, but perhaps not impossible.... have you run a Unibox calculation on that? Could look pretty good.... you shouldn't get my thinking going down these paths, Craig!!!! The 4 ohm woofer impedance would help the net sensitivity; with 2.83V, should be about 87 dB, it's just pulling a bit more juice from the amplifier.




Now, I'm wondering if just for fun we should have some options on the tweter, maybe jazz it up to a D3004/66000... you were the one escalating to an Aurasound woofer, so I'll play the tweeter trump card, it would give a lot of fexibility in the crossover transfer function using a Duelund style design. And due to impedance similarities, the crossover would require little tweaking between this part and say, the RS28a.

Sounds like something for Evil Twin to think about...

[CraigJ]

Not to steal the thread, I was thinking of a petite Isis Grande, or an M10ta in the existing M8ta box + top piece

have you run a Unibox calculation on that?

ah, no. Does Unibox, or any of the the other speaker design software actually run on a Mac? I'll go back to you design, I build. ;x(

Cj

p.s. the NS10 requires a 8.89" cut out, the M8ta has 9.875" internal width 8) and a $28 mid and a $220 tweeter 8O

[JonMarsh]

Not to steal the thread, I was thinking of a petite Isis Grande, or an M10ta in the existing M8ta box + top piece ah, no. Does Unibox, or any of the the other speaker design software actually run on a Mac? I'll go back to you design, I build. ;x(

Cj

p.s. the NS10 requires a 8.89" cut out, the M8ta has 9.875" internal width 8) and a $28 mid and a $220 tweeter 8O

Hey, sounds like I could be in business... now remember, a $220 tweeter IS less expensive than a $270 tweeter, blah blah blah!

On my intel based Mac Laptops, I'm dual boot to Windows when I need it, so I can run XP apps natively. On my Quad core G5 Power Mac, we just do it by shear brute force and CPU cycles- VPC (virtual PC), a product from Microsoft that creates a customized XP enviroment on a Power PC based Mac. Not very practical for standard G4 or G5 PowerMacs, but on a Quad Core G5 with 8 GB of RAM, there's plenty of CPU cycles to throw around at the problem. That's what I've done all my EDGE simulations on, too.

I'll setup a Unibox calc for the NS10-513 this week- should be interesting. Since the twelve does so well in 76 liters, versus the RS225 in 68 liters, I'm thinking the 68 liters will probably be fine for the 10.

Anyone wants to do a customized top module scheme, well, that's where the Y in DIY comes from!

We'd better quit hijacking this thread and let it return to discussion of enclosure and design for the 7" revelator.

[TacoD]

The 6600 is a great tweeter, hopefully the new production run sounds the same as the "original". I like the idea with the Aura, but this thread was about the 7" scanspeak...

What about the 10" scanspeak revelator (the one with alu cone).

[JonMarsh]

On the original topic, I think that set of drivers with a higher crossover might be a good candidate for a Duelund three way, maybe a center frequency near 2 kHz.


Which one of the SS 10" woofers were you referring to? The compact one, or the 26W8867T or it's 4 ohm sibling? It looks like it could be usable up fairly high, though there's a curious step in the published response around 500 Hz, and it does the typical big dip from flex before letting loose up on top that seems typical of curvilinear cones. Decent 9 mm Xmax. At ~260, it's a little dear on this side of the Atlantic.

It's an interesting comparison to the similarly priced W26, which has a bit less Xmax, almost identical moving mass, peaks at 550 Hz then drops back a bit. Not sure how high I'd trust it... the Seas W26 has about 3X the rated Le. The Seas ought to be very nice up to 300-400 Hz at least. I'd be curious to see what shows up with shaped sine bursts above that.

[TacoD]

I was thinking of the 26W/8867T00. I heard the Seas W26, but I wasn't blown away by it, but I think most of that was due to the bad execution (BR tuning was way of).

Also expensive overhere (but Aura is also very expensive ~270 euro)

[JonMarsh]

Yeah, the price differential on Aurasound certainly hurts. I haven't seen any US measurements on the 26W8867T- what about Klang and Ton?

The first SS metal 10's that came out over here was the sub driver that was nearly $400- didn't generate a lot of interest at that price!

~Jon

[xyrium]

Would anyone care to repost that PDF? It appears to be no longer available at that link (Yeah, I know, this is an oldie). Thank you!

Yes, read this pdf from Troels, he discusses the cabinet and tuning.

You can make a test cabinet, to try the tuning if you're not certain. But from my point of view it makes sense to use the advise from Scanspeak.

[Arc00]

http://www.troelsgravesen.dk/SP38.htm

That is the project it relates to.

[TacoD]

http://www.troelsgravesen.dk/SP38.htm

That is the project it relates to.

Thanks.

[Notorious_AK]

Troels' SP38 doesn't look like very optimized design.
tweeters don't perform to full potential, while 7in revelator is pushed too far at high frequencies.

[TacoD]

The document describes what the Revelator designer recommends for box tuning. You can find lots of designs on the Internet which are not optimized, do not get me started on many commercial loudspeakers .

[jkrutke]

The document describes what the Revelator designer recommends for box tuning.

Taco, I see you're still talking about enclosure size for the 18W/8531G00. I made a blog entry a while back about that, though not you in particular.

It is often discussed about what the optimal enclosure size is for this excellent woofer. For a vented enclosure, a number that often pops up is 22 liters with a low 30's tuning because at one time or another, an engineer from Scan Speak said this is what the woofer was designed for. Well, I've got to warn you folks: vented in a 22 liter enclosure is clearly bad advice - and it keeps getting repeated by people who think it's some sort of definitive number. What the engineers designed for and what manufacturing has come up with is often different, and in this case very different. I think I've tested about 8 or 10 8531's over many years and the average Qts is about .47 with a range of .4 to .55 - very far off from manufacturer's specs. My tests for T/S parameters are often verified with high level in-box near field response curves. With the 8531, the best advice you'll get is to go big or go sealed. And even having said that, don't be afraid to go sealed as the 8531 has very satisfying extension in a sealed box. For vented, I think 30 liters is the smallest I would go, but 38 is even better, such as what I used in the ZRT design.

Taco, what kind of real data or measurements would it take to prove to you that 22 liters vented is too small for a 18W/8531G00? Chances are I have that data and could post it here.

[JonW]

My experience with the 18W/8531 mirrors what John is saying.

I made a series of test cabinets and tried different tunings. I listened to all the various configurations. Details are buried somewhere in the Spassvogel thread. I did 2 rounds of listening to different tune options, first in test cabinets and then in the final cabinets. In both rounds I ended up at the same tuning preference.

I went for a 34 Hz tune in about 39 liters. The woofer can certainly play lower. But it seemed to me that, say, at 30 Hz tune you got more bass but gave up a little bit of midrange clarity. Tunes higher than 34 Hz were diminishing in terms of picking up more midrange clarity but did loose some bass, of course.

All of this is just with my ears, so the results are not solid measurements like John has.

[SoundOfNothing]

Anyone play with and hear a sealed alignment? What was the optimum volume you came up with? Right now Im leaning with bigger is better, but I dont want to take too much volume from my bass driver.

[xyrium]

That's kind of where I'm headed with my inquiry. Zaph mentioned a potential sealed design for his ZRT, but I haven't seen anyone execute it yet. If that little 18W can get down to 35Hz in a reflex cab, I'm thinking one could get a solid 50-55 out of a sealed. That would be about as sweet as a design could be to cross over to a sub since the sats would be sealed, and the sub would only really need to play true sub freqs.

Anyone use a 20l sealed cab for this yet?

[TacoD]

Anyone play with and hear a sealed alignment? What was the optimum volume you came up with? Right now Im leaning with bigger is better, but I dont want to take too much volume from my bass driver.

I used both sealed 20 liter and vairous designs in ported 18 - 25 liter cabs. In a closed box the woofer still has decent bass performance. The woofers I used where early models from Scanspeak (do not have the T/S, but the measured FR response looked decent)

I also heard designs using the woofer in larger cabinets (first desgin of Dutch importer, when the revelator series where brand new), but it then doesn't sound as tight on the bass. I did not use myself the woofer for years, they also added a rubber sock for the magnet assembly, so your milage may vary.

The only advise I can give is to try various cabinets.

[TacoD]

Taco, I see you're still talking about enclosure size for the 18W/8531G00. I made a blog entry a while back about that, though not you in particular.



Taco, what kind of real data or measurements would it take to prove to you that 22 liters vented is too small for a 18W/8531G00? Chances are I have that data and could post it here.

I only wanted to help, as somebody was reading this old topic . Thank you for the offer, but you do not have to prove me anything, I fully capable to do the measurements myself (I only do not write a blog about it ).

[kstich]

Sealed is what I plan on doing with Zaph's 2.5 way ZRT.

With Zaph's T/S, the 38 l enclosure comes out with an F3 of 60 Hz, and a Qtc of 0.783, which is pretty consistent with Zaph's tuning. I am planing on a little larger enclosure, but not much. Based on the above, it would take 54 l to get the speaker to a Qtc of 0.707 for two drivers.

When I model the various enclosure sizes they all seem about the same once the 80 Hz HP filter is applied. Considering the HP/sub filter, I am not sure how much effect the various enclosure Qtc's would have on the sound.

[Bear]

You may find Zaph's blog post from August 22nd helpful in terms of planning cabinet size for the 18W Revelator:

http://www.zaphaudio.com/blog.html

[Curt C]

From the FWIW corner:

I tested a pair this weekend. I don't have all the T/S numbers handy, but I remember their consistency was very close, with Qts around 0.5, Vas of 42 liters, and fs of around 30 Hz.

C

[xyrium]

Thanks guys. I totally appreciate the input.

[xyrium]

Hey Gmed,

Though I'm not being a slacker, can you copy and paste your DDBase entry for the 8531 and PM it to me? For some reason, I can't get unibox to display the proper output after i enter the parameters into the DDBase tab.

Tks,
Paul

Im calculating the box volume and port size for the Scan-Speak 7" Revelator 8 ohm 18W/8831G00 or the 18W/8531G00, and Im coming up with a Box volume of 46L, F3 29.8 Hz, ported with 5.08cm x 10.3cm. At 21 Liters, Im getting an F3 of 42.7Hz with a port 5.08cm x 15.4cm. Can a 6.5" really go this low? I think I would be happy with an F3 of 42 Hz. This seems to be a very big volume for a 6.5". Am I doing something wrong? can I go smaller?

Based on Madisound.com "The 18W/8531G should have an F3 of about 50Hz sealed and 35Hz vented".

TECHNICAL DATA:
Sensitivity 2.83V/1M 87dB
Free air resonance Fs 27.5 Hz
DC resistance 5.8 ohm
V.C. inductance 0.35 mH
Power 70W
Effective cone area 150 cm2
V.C. diameter 38 mm
VC height -
Air gap -

Lin. & max. excursion ±6.5 / ±11 mm
Air gap flux density -
Force factor BL Product 6.7 Tm
Moving mass incl. air 15.5 g
Net weight 1.75 kg
Vas 61 ltrs
Qms 5.0
Qes 0.39
Qts 0.36


What do you guys think?