HSU STF-2, measurements?

RuSsMaN

Anyone (Doc) got any real-world graphs / numbers on this sub?

If you haven't done it yet Doc, I'll buy your favorite bottle of Scotch if you could take the time. I'm looking at mating these (a stereo pair) with some Spendor 1/2's - and though I trust my ears, I'd like to see the response graph charted on paper in an avg living room.

Cheers,
Russ

pjdami

Russ,

I did some sweeps a few months ago in my living room and in my two channel rig in the office. I got the STF-2 around 23 Hz in the office (smaller room) before it tails off. I'm pretty sure Doc has graphs of the STF-2 because he had one for a while and he has professional gear to measure it.

By the way, you bagged the 1/2s? Congrats. I use the STF-2 with my S8s for the bottom octave setting the crossover at about 40 - 45 hz. If you have a tube amp laying around try them 1/2s on that too for some gorgeous midrange.

http://clubpolk.polkaudio.com/forum/showthread.php?threadid=14932&highlight=Hsu

pjdami

Found Doc's review of the STF-2 here:

http://www.hometheaterforum.com/htforum/showthread.php?s=&threadid=209418

Dr. Spec

That in-room curve is with an 80 Hz xo and a 2nd order high pass and a 4th order low pass.

This disparity in the slopes will unfortunately cause an emphasis in the 50-90 Hz bandwidth, and is a throwback from the THX days of bass management.

THX recommended an 80 Hz xo and the 2nd order high pass and 4th order low pass filter rates because THX certified surround speakers were sealed units with a natural 2nd order roll-off and an F3 of about 75 Hz.

The combined effect of a 2nd order high pass filter at 80 Hz, and a 2nd order natural speaker roll-off at 80 Hz, resulted in a 4th order roll-off - not coincidentally the same as the low pass filter rate imposed on the subwoofer. The final result: a 4th order high pass and 4th order low pass filter rate at the selected xo of 80 Hz and a nice neat crossover.

Unfortunately, nearly all surround speakers these days are vented, and imposing a 2nd order filter above the tune point will predictably result in a 2nd order roll-off. Below the tune point, the combined roll-off suddenly steepens to 6th order.

With an 80 Hz xo AND dissimilar HPF and LPF slopes, the use of vented surround speakers with an F3 of 50 Hz will likely result in an emphasis in the 90-50 Hz region because the vented speaker has not yet begun to naturally roll-off, and is only being artificially filtered at a 2nd order rate.

Russ, my advice for a 2 channel rig is to use a high quality external xo (like a Marchand) with same slope HPF and LPF (maybe 2nd order) and a frequency of about 80 Hz with the STF-2 directly between the two Spendor's. Since the Spendor 8" midbass driver is xo'd at 3 kHz, this will reduce IMD and clean up what is already an exceptional midrange. It will also keep the Spendor away from its tune point (probably 50 Hz), which will keep group delay lower in the mid-bass region, improving the coherence of the bass delivery. Since the STF-2 lacks a variable phase, you might have to experiment with the distance to the listener for all three speaks, or the STF-2 might be perceived as "early" or "late" to the party.

Regards,

Doc

Tour2ma

Originally posted by pjdami
Found Doc's review of the STF-2 here:

http://www.hometheaterforum.com/htforum/showthread.php?s=&threadid=209418

You do realize you just cost Doc a bottle of Scotch, don't you??? Brave man to come between someone as heavily armed as Doc and his beverage of choice...

pjdami

You do realize you just cost Doc a bottle of Scotch, don't you??? Brave man to come between someone as heavily armed as Doc and his beverage of choice...

Waz up Tour! Let me put it this way; I'm off of work all week and just got in from Bourbon Street in Nawlins.

If that's the case, Scotch is on me for Doc:D

And by the way, congrats Doc on making it bigtime on that Secrets review of the newest SVS subs. Way to go man.

p.s. I'm serious about the Scotch too.

Cheers to all!!!

Dr. Spec

Macallan will do........:cool:

http://www.themacallan.com/index.html

You guys are just too cool; Club Polk always holds a warm place in my heart.

It seems all the initial doubters are now silent as other reviews and owner reports are flooding in on the PB10-ISD; it's a great sub.

I''ll be doing more sub reviews for Secrets in the future. Look for the MRS-10 review sometime in the next week or two.

Regards,

Ed

Tour2ma

Nice site... but this kinda surprised me (He Heeeee)
==============================================
Malt Whisky Companion - Michael Jackson

This is the updated fourth edition of Michael Jackson's malt whisky companion. Jackson is acknowledged as the world authority on malt whisky. ==============================================

Of course, I guess there could be two MJ's...

Doc,
Mrs-10? A sub with wife appeal?

Dr. Spec

You know it buddy - WAF is sky high with this little tyke. Diminutive and classy come to mind. You could hide it anywhere, but why would you - it's a good looking unit. Fills the room darn well too, considering its size. I like it..........

gatemplin

I really like that sub, I bet it sounds great. Mid Q sealed with and XBL^2 driver. Yum yum. Me thinks it uses the CSS SX-10 driver, am I right Doc? It looks the same as this sub except with a different amp.
Here are some pics of the driver:http://www.diycable.com/main/product_info.php?products_id=534

Dr. Spec

You are correct, oh great DW gang member. The cab can be sourced from CSS, as well as the driver. And the driver is also available from DIYCable per your hotlink. The amp is not CSS spec; not sure where he's sourcing that from.....

Nothing really revelatory about the performance of the unit; a tiny sealed enclosure won't generate a great deal of output down low, nor was it intended to. I'm sure the driver would perform considerably differently in a larger vented or PRd enclosure.

It definitely does take advantage of room gain in a small-mid sized room, since it rolls off 2nd order (until 31 Hz, and then it's 3rd order). It has good extension to about 23-25 Hz in my room.

It's a good sounding unit for both music and movies; well balanced and well behaved with surprising ability to fill the room for being so small.

gatemplin

I thought so, Adire, DIY cable, CSS and AV seem to be working together a lot lately. And probably even more now that the great DW has expanded into driver manufacturing.

I hear rumours about some new products heading Acoustic Visions way. I think maybe an uber 18" with Xbl^2. Maybe you'll be testing some of this stuff out in the near future.

The amp is not CSS spec; not sure where he's sourcing that from.....

It's probably from Parts Express. Looks similar to this little fella.

As I told you before, I'm looking forward to seeing your review of the MRS at HTS.

Sorry for de-railing the thread Russ:D

Dr. Spec

Yep, that's the amp.......thanks for the link.

I think maybe an uber 18" with Xbl^2.

Whoa......an XBL Maelstrom - think of the possibilities.....

I hope to test more products with Adire woofers to see how they perform in a variety of applications.

Don't worry about the de-rail........Russmeister has what he needs (I hope).

Russ - you could always uses the LPF in the STF-2, but it lacks any HPF for the speaks, even a fixed one. So you will be double bassing things. I prefer the external higher quality xo, or digital xo if you can find a pre/pro with similar slopes for both ends. I know the B&K units have this capability....

gatemplin

Whoa......an XBL Maelstrom - think of the possibilities.....

Yep. If I recall correctly it is meant for small Vb sealed apps. What I am not sure about is who is getting it done.There will be a ton of drivers coming out with XBL^2 over the next year and I know some of them are headed Kyle's way. Maybe even super tweeters with 4mm Xmax.:D I know that some friends of ThomasW have licensed the tech and they are doing 18's, 15's and 12's very soon.

RuSsMaN

Stupid question, but what is the crossover in/out toggle on the rear for, I figured that was the high pass, if you ran high-level connections to the sub.

I wouldn't think about running ANYTHING between the Spendors and the amp / preamp anyway. Not even the fanciest of external crossovers.

The 1/2 is the ONLY speaker the Absolute Sound tested, and couldn't get ANY measureable distortion from the original recordings they played on it. They actually shut the entire session down, to troubleshoot their equipment - only to find nothing wrong - the 1/2's are THAT good.

They will be hooked up to a one-of-a-kind Dodd Audio Tube line stage, and a 100wpc Beard Tube amp. Just looking for a sub, or pair of subs to blend in, where the Spendor's trail off. If I go with the HSU, I will run a stereo pair - I'm just not convinced they can 'keep up' yet.

De-rail away fellas.

Cheers,
Russ

Dr. Spec

Stupid question, but what is the crossover in/out toggle on the rear for, I figured that was the high pass, if you ran high-level connections to the sub.

This deactivates the variable low pass filter for a low level home theater connection where the pre/pro does the bass management.

I wouldn't think about running ANYTHING between the Spendors and the amp / preamp anyway. Not even the fanciest of external crossovers.

Then you certainly don't want to do any sort of high level connection using the STF-2 outputs back to the Spendors.

You will need a L/R low level output from the preamp to go directly to the STF-2.

Just looking for a sub, or pair of subs to blend in, where the Spendor's trail off.

If that's the case, connect the STF-2 with a separate L/R output from the pre-amp and then engage the low pass on the STF-2 and set the frequency to about 40-45 Hz.

Unless lack of output is a consideration, you won't need stereo subs at this low of an xo. And the L/R low level inputs are summed on the STF-2.

Run a sweep and look for a hole or a peak in the response and fine tune the low pass accordingly.

Tour2ma

I dunno, Doc... What you are suggesting comes perilously close to calibrating a 2 ch rig...

Dr. Spec

The only reason I originally recommended an external xo with a higher frequency is to provide more coherence to the bass delivery.

The Spendor's are vented and have an F3 of like 45-50 Hz so by integrating the STF-2 at such a low frequency, you will have a spike in group delay in the 45-50 Hz region. This will make seamless integration more difficult...if GD exceeds about 20 ms at 50 Hz, it might be perceived by Russ as a vagueness in the phase/timing of the bass delivery, especially if the STF-2 takes over right below that point (and lacks variable phase).

You could always plug the ports on the Spendors and make them sealed........that would be an interesting experiment. They might lose some extension, but who cares - you've got the STF-2 for that. And there won't be a GD spike at the tune point anymore. They will roll-off 2nd order, too (unless Spendor has a high pass installed or some EQ, etc.).

The easiest way to match the phase with the STF-2 is to run a 50 Hz (or whatever xo you select) test tone through both the Spendors and the STF-2 with the STF-2 set to 180. Move the STF-2 backward and forward until a noticeable drop in SPL is seen at the listening position. Then flip the phase back to 0 - the Spendor's and the STF-2 will then be in phase.

Tour2ma

Sure... easy for you to say...

Neat trick setting the sub out of phase, but I actually have one potentially useful comment after I read your post twice. The 'trick" does presume the Splendors, and the sub(s) are operating in the correct absolute phase. We know that is not necessarily the case. Amps and speakers don't always absolutely allign...

Damn, posting something even borderline profound is exhausting...

BTW, Doc, the calibration comment above harkens back to a thread I started a couple weeks ago. You may not have seen it, due to it being hunting season and all...

RuSsMaN

Originally posted by Tour2ma
Amps and speakers don't always absolutely allign...

Mine do.