Super Tower /R SE specs

Stimpy · « **Reply #20 on:** 4 Apr 2016, 09:59 pm »

So, how similar to each other were these two? One just a newer version of the other? I've always loved the look of the rounded Oak cabinet corners, and the D'appolito driver layout of the top speaker. Just wondered how they sounded?

James Romeyn · « **Reply #21 on:** 4 Apr 2016, 11:05 pm »

As you can see, the wave front of the SE on top beats the lower standard ST/R. But the lower one has Brian's own mid design, which I prefer overall vs. the WCF mids on the SE, but I'm nit picking. Overall the upper SE speaker is better, by good margin. Better domes too, by good margin, never really liked the Morel domes much at all.

I kept hounding Brian to switch to the Scan Speak soft dome D200009, and he did later, and those are the best domes he ever sold, but the Focal are not bad at all, much better than the Morel (almost anything is, the Morel are just kind of fuzzy sounding...the 30s are better than the 29s, but neither as good as the Focal and Scan Speak.

If I had room I'd have a pair just for old times sake, and they sound very good for a cone/dome system...it's just that I don't really have any interest in cones/domes any more, except for maybe the insanely expensive stuff.

ST86 · « **Reply #22 on:** 5 Apr 2016, 04:03 pm »

Stimpy, yes the Goldwood 15" woofers were drop-in replacements. No need to modify the cabinet. Brian only specified a crossover change when I replaced the 12" original poly driver with the Misco LC12W-8A. He said there isn't a crossover change needed if only the 15" is replaced. He suggested a low pass coil change from 1.0 mH to 2.8 mH along with the Misco driver. This also moved the woofer to mid crossover from 600 Hz to 450 Hz. Brian told me there is a response dip at 1 KHz in the Supertower/R and Tower ii, and this coil change along with the driver change should mitigate it. It did, somewhat, so I kept tinkering. I changed (unwound) the coil to 1.4 mH. This also changed things but I am not sure it improved anything. Recently I cleaned the L-pads with DeOxit Gold (thanks James) and that made a huge improvement in clarity, so now I am thinking I need to go back to Brian's 2.8 mH coil value. Maybe the improvement at 1 KHz with the 2.8 mH coil was masked by the dirty L-pads. I see another Parts Express purchase in my near future.

For the past couple weeks I have had my Supertowers apart trying to figure out how the woofer to mid series crossover works, where the break points are, and what the "correct" L and C values should be for the drivers that are in the cabinet. I have an audio signal generator and volt meter. I send 1 VAC 50 Hz to 1 KHz to the speaker terminals and sweep the signal until I see 707 mV across the driver which should be the break point for that driver. Sounds simple but it has been more complicated that I expected as every component affects every other component and I am having a difficult time isolating signal paths to determine which frequencies go through which drivers. Can someone with a bigger brain shed some light on this?

Ed

James Romeyn · « **Reply #23 on:** 5 Apr 2016, 05:03 pm »

Unfortunately, it is impossible to isolate poles in a QSO crossover, which means there can never be modeling software, which is the main reason it's not more commonly used.

I think you can find the crossover poles by testing as you describe, but changing one leg also changes the other, so it's impossible to isolate the two.

At least one crossover design genius is on my speed dial. If I had my druthers, I'd probably send the drivers to him to model. Based only on aural memory, and some intuition, I suspect a good option for this model is 2nd order LP for the mid bass (really, the coil value is so low that it has little affect on the 15"), and 2nd order HP for the mids (no QSO....these slopes are electrical, acoustic unknown). As stated earlier, I prefer Brian's own mid cones over the Taiwan Versa Tronics WCF, but Brian's likely benefit with a small value LP coil (Brian would never approve) while the WCF would degrade with such coil. Adding this LP coil may require moving the treble pole a bit lower, but it's so high (estimate 5k Hz) that there is plenty of margin for this mod, and it's easy, just add cap value.

Brian's LEDE sound room was so dry on the speaker end that it tended to mask certain qualities that were audible in normal applications. It's interesting to me that our Space Generator reverberant field system, coupled with main speakers having a very tightly controlled radiation pattern, replicate in a normal sound room the best qualities of Brian's LEDE sound room.

One of the benefits of QSO for OEM is that it magnifies the value of the HP cap bank for the mid range, allowing a much smaller value than a non-QSO xo. I wonder if this cost-savings affected Brian's preference, but it might have been of no consequence.

Stimpy · « **Reply #24 on:** 5 Apr 2016, 05:15 pm »

ST86,

Thanks for the Goldwood feedback. That's very good info. Every VMPS owner needs to know these things, since VMPS spare parts aren't exactly plentiful! Back-up drivers have to be tried and evaluated.

Good luck on figuring out your crossover too. And if your Supertowers have Brian's typical series crossover, I expect it won't be an easy dissection. It's no wonder you can't isolate components if the speaker does have series wiring.

ST86 · « **Reply #25 on:** 5 Apr 2016, 05:39 pm »

James, Stimpy, thanks for the feedback. I am going to go back to Brian's value of 2.8 mH and re-measure.

To follow up on the Goldwood woofers I use the smaller 12" Goldwood GW-12PC-8 for the lower woofer in my Tower ii. Those were a very tight fit, so much so that when I refinish the cabinet if the weather ever gets warm enough here in MA to work in my garage I will open the cutout with a rasp or hand planer.

Ed

RSorak · « **Reply #26 on:** 5 Apr 2016, 08:20 pm »

There are 2 sets of speakers pictured in this thread....I have the bigger ones at the top....Not the smaller ones posted second....Do these suggestions apply to them or the smaller ones or both?

ST86 · « **Reply #27 on:** 5 Apr 2016, 08:37 pm »

My experiments with the crossover and recommendation of Goldwood 15" woofer apply to the older Supertower/R, the one pictured with black painted front and non-rounded corners.

Ed

RSorak · « **Reply #28 on:** 5 Apr 2016, 09:18 pm »

Heres the crossover schematic for the larger version

The image is getting shrunk somehow......I can read fine on my puter but here and DL version is smaller???

I uploaded a 964kb file and when choose save as get a 44kb file?

James Romeyn · « **Reply #29 on:** 5 Apr 2016, 10:05 pm »

You would not believe how fast Brian would assemble those xo's. Conversely..........

We had a customer call for a copy of this exact xo diagram. He purchased ST/R kits many years prior, and never assembled them.

Besides building the xo, his next biggest problem was giving his cats the sad news that he had found a better use for their "cat condo," AKA empty ST/R enclosures...

My very very first VMPS buyer was a local guy in Novato, Marin County, who bought an Original Sub kit. Debra bumped into him years latter, at which time he mentioned they still awaited assembly.

The best of intentions...

RSorak · « **Reply #30 on:** 6 Apr 2016, 04:26 am »

When I got my kits I couldn't put them together fast enough....and being slow and careful building the XO's, because I understood how important it was not to make any errors, was a difficult process at my relatively young age then. I remember staying up way too late and the forcing myself to sleep so I could stay coherent, and make sure they were right. I sure glad I did because my ears and friends have enjoyed them for many many years now.

James Romeyn · « **Reply #31 on:** 6 Apr 2016, 04:43 am »

The R value on the mid bass: is that 30R crossed out, replaced by 11R?

The bass and mid bass were each 8 Ohm nominal. If yes to above, the respective nominal impedance were:
6.6 Ohm (30R)
5.6 Ohm (11R)

ST86 · « **Reply #32 on:** 6 Apr 2016, 02:43 pm »

That schematic looks like mine except for the C and L values. The series resistor on my 12" midbass was 25 ohm, not needed with the upgrade to the Misco driver. Your crossover cap to the mids is 4.19 uF and mine is 54 uF? That is quite a difference, everything else is pretty similar. What is the inductor value between woofer and ground? Can't read the drawing.

My Supertower schematic is posted somewhere on another thread, I can repost here if there is interest.

When you used "save as" did it give you a list of sizes? Some programs will resize large documents to "standard" size for email.

I was the same way building my Supertowers. Long nights, many checks to be sure everything is right, and then the payoff of countless hrs of listening enjoyment.

Ed

Stimpy · « **Reply #33 on:** 6 Apr 2016, 03:21 pm »

I wish there were enough owners, with crossover schematics, that we could start a new thread, and Pin it. Nothing but VMPS documents and schematics for current and future owner use. While I respect that this was intellectual property for Brian, but it seems that most of this stuff was only filed within Brian. We need a record of his notes, at least as much as we can find. I don't think there will be a future VMPS legacy if we don't attempt this.

ST86 · « **Reply #34 on:** 6 Apr 2016, 03:58 pm »

Stimpy,

I agree. I don't think for example there should be a problem posting whatever paperwork was provided in the kits, which would include schematic, parts list and build instructions.

Ed

RSorak · « **Reply #35 on:** 6 Apr 2016, 04:16 pm »

The R value on the mid bass is 22 ohm.

The coil to the woofer/midbass is 1.5mH.

James Romeyn · « **Reply #36 on:** 6 Apr 2016, 04:32 pm »

Quote from: ST86 on 6 Apr 2016, 02:43 pm

That schematic looks like mine except for the C and L values. The series resistor on my 12" midbass was 25 ohm, not needed with the upgrade to the Misco driver. Your crossover cap to the mids is 4.19 uF and mine is 54 uF? That is quite a difference, everything else is pretty similar. What is the inductor value between woofer and ground? Can't read the drawing...
Ed

I would bet the Misco was a pretty huge upgrade from Brian's 2710 Gefco 12" mid bass (the only VMPS 12" w/radial ribs, small magnet, and 1.5" VC), probably made in greater quantity than any other VMPS driver. The 2710 had great mid bass dynamic snap, but after hearing it forever, both alone and in systems, I was convinced it really needed either to be crossed lower or redesigned (it was unchanged my whole time there). Crossing the 2710 so high shifted higher all poles on the smaller drivers, increasing system global power handling. (Crossing the 2710 higher has no effect on its power handling, but it moves the mid range HP pole higher, which increases mid range power handling.) The higher the 2710 is crossed the more distinct is its cupped hands effect. There is much less cupped hands effect in use in the enclosure, but still too much for my taste.

If the Misco mid bass swap maintained the same L, the lower impedance (no R) moves the pole lower. That, coupled with what I presume is less natural extension than the 2710, required the increase in C value, which moved the mid range pole lower.

I presume the increase in C value is not linear. IOW, 2x the C value does not equal one octave lower, as would be the case with a straight first order electrical pole, because QSO is not linear in that way. Also, the lower mid bass impedance and different mid bass parameters directly affect the mid range pole, in ways I can not explain.

The person I know with the most knowledge about QSO is Fritz of Fritz Speakers, a great guy who makes possibly the best performing small speakers ever.

I presume the Misco swap is a big performance upgrade. FYI: QSO is 1st order electric LP, 2nd order electric HP.

ST86 · « **Reply #37 on:** 6 Apr 2016, 04:58 pm »

Performance upgrade with Misco? Yes. The difference was obvious, even to me.

Brian told me the 25 ohm on the 12" was to level match (acoustically) the 12" with the other drivers and the resistor was not needed when switching to the Misco. Was unaware of the effect the resistor has on crossover performance.

54 uF high pass cap to mids with Misco is pretty close to original value with 2710, maybe an increase of a few uF.

Original woofer-to-ground inductor with 2710 1.0 mH, changed to 2.8 mH with Misco driver.

Oh, and I should also mention mids were upgraded from the grey poly cone Peerless to what Brian referred to as "classic mids" that look strikingly similar to a four ohm version of the Dayton Audio DCA 130A-8. I don't remember if I had to change the high pass cap value to 54 uF when I updated the mids or the 12".

Ed

RSorak · « **Reply #38 on:** 14 Apr 2016, 08:37 pm »

I got the Goldwood woofer, here's pic showing the diff in magnet size, GW is also much heavier. Goldwood is slightly bigger in outside diameter and will not fit in stock hole. I had to enlarge the hole slightly about 1/16 all around.

Sound wise, it rocks....just like the original. The bass extension may be greater w the GW. Very happy my crackle is gone.

Looking Misco's website today {original woofer manufacturer}, they certainly don't seem like a high end company at all....Don't know if it was this way 30 yrs ago....

James Romeyn · « **Reply #39 on:** 14 Apr 2016, 09:39 pm »

Why on earth would that woofer on the L outperform the one on the R? That makes absolutely no sense at all! None!

/sarc off

Doesn't that just seem wrong when one woofer requires 1/16" larger radius than the another?