Blackhole 5 Damping Material In The SDA SRS 1.2TL

DarqueKnight

Introduction

Cookie wonders why I would waste a beautiful spring day taking apart my speakers...again.

This is my favorite kind of mod: cheap and easy with a big payoff. Adding a few strips of Blackhole 5 to the driver/tweeter area of my speaker cabinets provided a bigger improvement than the expensive and very time-consuming rewire (with AudioQuest GO-4 speaker wire). Blackhole 5 is a five-layer foam and stiff polymer material that provides cabinet damping, isolation, and absorption. A 27" x 24" sheet cost $84.90 from Soniccraft (inclusive of $14.95 shipping) and was enough to do both speakers. Blackhole 5 is not recommended in the passive radiator area because it will interfere with the transmission of vibrational energy (fluid coupling) from the drivers to the passive radiator.


Figure 1. Blackhole 5 top side.


Figure 2. Blackhole 5 back side, sectioned off for cutting.

The following pieces were cut from the 27" x 24" sheet:

1. Four 3" x 27" strips, to go behind the stereo and dimensional drivers.
2. Four 1.5" x 27" strips, to go on the cabinet sides.
3. Eight 3" x 6.75" blocks, to go behind the tweeters.

The interior volume of a SDA SRS 1.2TL cabinet is 6.77 cubic feet. The total volume of the Blackhole 5 pieces was 0.26 cubic feet, or 3.8% of the interior volume. However, Blackhole 5 is claimed to only displace 0.25" of air, in which case the effective total volume of the Blackhole 5 pieces was 0.05 cubic feet, or 7 tenths of 1 percent of the total speaker interior volume.

Cutting


Figure 3. I used common kitchen cutting tools.


Figure 4. My cuts weren't the neatest, but they didn't have to be.

I used a box cutter with a sharp new blade to score through the stiff polymer layer, cutting along guidelines in red. Next, I made a starting cut through the foam with ordinary, but sharpened, scissors. Finally, I used a sharp meat cleaver to saw through the foam along the guidelines. It took 20 minutes to complete cutting.

Installation


Figure 5. Blackhole 5 installed in right speaker.


Figure 6. Blackhole 5 block behind tweeter.


Figure 7. Blackhole strip on cabinet side.


Figure 8. Polyfill was reinstalled after Blackhole installation.

The cabinet walls were wiped with a dry cloth prior to installing the Blackhole 5. A small, quiet voice tried to get me to disassemble my speakers and reseal the cabinets with an appropriate construction grade sealant, but I ignored it. I'm getting a 3 second fall on the passive radiator pressure test...so I'm good.

The 3" x 27" strips were horizontally centered behind the drivers and were vertically centered by starting them 2.5 inches from the top of the cabinet. The 1.5" x 27" strips were horizontally centered on the side walls and started 2.5" from the top of the cabinet. Installation took 55 minutes per speaker. I only removed the drivers, polyfill, and the crossover. I would have removed the driver wires, but I have the stiff, solid core wire bent in a certain way for strain relief for the relatively soft driver connection tabs, and I did not want to have to go through the tedious process of realigning them again.

I was very pleased to find that the pressure sensitive adhesive was STRONG!

The Sound

The right speaker was done first. Percussion instruments, like shakers, were much clearer than on the left. The articulation of words with clicks and sharp transients (e.g. unique, breeze, whisper, ocean, etc.) was much clearer and detailed on the right. The sound stage weight shifted to the right and there was more tactile sensation on the right. There was more speed, definition and articulation in the bass. This was evident in both stereo and mono modes with just the right speaker treated. I have been reading about this modification for years, but I was still quite pleasantly surprised at the level of improvement. The right speaker was generating Such Good Sound that I was very enthusiastic about treating the left speaker.

After both speakers were treated, There wasn't any improvement in spatial properties, but there was a significant improvement in detail overall, particularly at the sides and rear of the sound stage. Since the passive radiator was getting more clean coupling to the drivers, bass output, articulation, detail and speed was increased.

Thanks to Polkmaster1, drumminman, and Toolfan66 for their pioneering work with this modification.

When I put these speakers up for sale next April, I hope the next owner appreciates all the hard work that went into updating and optimizing their performance.:cool:

schwarcw

Nice write-up! If I lived closer, I might buy the speakers. The price of gasoline for the trip could easily pay for the mods that you've made that I haven't. I am very curious about this mod. I have contemplated it also. I've been doing to much listening!! I need to get off my butt and indulge in some Polk mod hysteria!

schwarcw

A couple of questions. I assume the Blackhole had self adhesive backing? Was the width cut to fit the available space on the rear panel? Or, cut to size to use the available materials? Did you put the Polyfill back inside?

VR3

Awesome write up!

Just wanted to throw out there you can cut this material with a table saw and it looks great

DarqueKnight

I thought about cutting it with the band saw in the machine shop at work, and I would have, if the kitchen utensils hadn't worked out.

schwarcw

Ah! I see that you installed the Polyfil. Ignore my last question

DarqueKnight

schwarcw wrote: »

Was the width cut to fit the available space on the rear panel? Or, cut to size to use the available materials?

Cut to make best use of the available material. I would have preferred the side strips were a little wider, but I didn't want to buy another sheet and have a lot of left over material.

headrott

Thanks Ray for the write up. I had just finished installing mine (along with the Jantzen inductors). Great improvement! I am still optimizing the large (16mH) inductor placement in the 2.3TL's. I am working on it as I type actually. Thanks again Ray. (Oh, and you should keep the 1.2TL's)

vmaxer

Great information once again. Dibs on the sale!

Toolfan66

I was hoping your findings, would be quite pleasing..:cool:

drumminman

Nice write up as usual. Impressive that you found the same SQ improvement even after your front end upgrade :cool:

Gotta ask - Are you really planning to sell your 1.2TL's :eek:

DarqueKnight

drumminman wrote: »

Gotta ask - Are you really planning to sell your 1.2TL's :eek:

Yes! Keep your eye on the flea market next April. I am expecting to have found a suitable high end alternative speaker by then.

Toolfan66

DarqueKnight wrote: »

Yes! Keep your eye on the flea market next April. I am expecting to have found a suitable high end alternative speaker by then.

On April 1st?:razz:

vmaxer

Toolfan66 wrote: »

On April 1st?:razz:

Yep, and I called dibs. I will be the first April fool!!

drumminman

DarqueKnight wrote: »

Yes! Keep your eye on the flea market next April. I am expecting to have found a suitable high end alternative speaker by then.

Dang! If this is not an April Fool's joke and you're moving on from SDA's it will be the end of an era here on the Polk Forum

Toolfan66

drumminman wrote: »

Dang! If this is not an April Fool's joke and you're moving on from SDA's it will be the end of an era here on the Polk Forum

Even if he moves on, and I'm sure someday he will, he will never let go of them. I know I won't...

My speakers are a mirror image to Ray's. Except the internal wiring..

DarqueKnight

Toolfan66 wrote: »

Even if he moves on, and I'm sure someday he will, he will never let go of them. I know I won't...

I can't imagine ever getting rid of either of my big SDA's (the 1.2TL's or the original SRS's) or my versitile CRS+'s. Speaking of SRS's, I need to order another sheet of BH5 for them.:cool:

thsmith

Ray, Did you consider norez over BH5?

Moose68Bash

Ray,

Another great write-up!

I did this mod to both my SRS1.2s and 1Cs -- on faith, based on the experience and testimony on the Forum about the effects of BH5. Your experience gives me even more confidence that this mod played an important part in the sonic improvement in both my sets of speakers.

Thank you, again -- not only for the write-up, but for the approach you take to documenting what you do.

DarqueKnight

thsmith wrote: »

Ray, Did you consider norez over BH5?

I considered Norez, Sonic Barrier and BH5. BH5 seems to be better suited for full-range speakers than Norez. It came down to a choice between BH5 and Sonic Barrier.


BH5 on left (1-3/8" thick), Sonic Barrier (3/4" thick) on right.

BH5 was thicker, stiffer and heavier than SB and had a much better adhesive backing. More importantly, several people on the forum have used BH5 in SDA's with excellent results.

schwarcw

headrott wrote: »

Thanks Ray for the write up. I had just finished installing mine (along with the Jantzen inductors). Great improvement! I am still optimizing the large (16mH) inductor placement in the 2.3TL's. I am working on it as I type actually. Thanks again Ray. (Oh, and you should keep the 1.2TL's)

I'd like to hear more about your decided location on the big 16 mH inductor.

headrott

schwarcw wrote: »

I'd like to hear more about your decided location on the big 16 mH inductor.

I need to do some more listening tests, but the prime spot (so far) seems to be on the crossbeam just above the crossover board (still attached to to the original 16mH inductor). I have placed the inductor on a piece of solid oak that is 1/2" thick. I will do some more listening tests tomorrow and hopefully be able to let you know. There seemd to be more clarity and especially detail there. Also, the soundstage is slightly more 3D and a little wider there. I'll keep you up to date though.

DarqueKnight

The red metal sculpture between my turntable and SACD player had to go. The greater output due to the Blackhole 5 mod was causing the sculpture to audibly vibrate and ring. I didn't notice it until I went to remove a CD while it was still playing. I could hear the sculpture "ringing" while standing next to it. Prior to putting the sculpture there several years ago, I had some concerns that it might have some audible effects. Listening tests, in addition to room measurements at the seating location with and without the sculpture in place, did not show any differences. Now, I can hear a small improvement in clarity if the sculpture is not in the center. Removing the center sculpture made a very small measurable difference, from 10 kHz upward, but the improvement in clarity is audible even when listening from another room.

Awwwww mannnnn...I'm gonna miss my artsy thing in the center.

Room response with and without the center sculpture.


Current and former room response.

The red line is the room response after the Jantzen high frequency inductors were installed. The black line is the current room response after the following changes:

1. Upgraded power amplifier to the Pass Labs X600.5.
2. Upgraded line level preamplifier to the Pass Labs XP-30.
3. Upgraded crossover resistors to Duelund CAST Silver.
4. Installed PS Audio PowerBase isolation platforms under turntable and SACD player.
5. Upgraded AI-1 Dreadnought cables to PS Audio Xtreme Resolution Reference speaker cables.
6. Installed Blackhole 5 in speakers.
7. Upgraded internal wiring to AudioQuest GO-4.
8. Installed AudioQuest Bi-Wire Jumpers.

I now hear much more high frequency detail. That is why I was surprised to measure a steeper high frequency roll off. As before, the response starts to roll off at 11 kHz, but the response is now only 1.4 dB above 80 dB at 11 kHz compared to 2.6 dB before. The response is now 3 dB down at 15.22 kHz compared to the prior 3 dB down at 17.5 kHz. Much of the previous elevated high frequency response was probably due to the effects of electrical and acoustic noise.

I decided to play with the acoustic panels a bit. Removing the center panel diminished bass weight and depth in the center. Removing the two side panels and the center panel resulted in overall diminished bass weight, and diminished image weight and depth at the sides.

drumminman

Glad to hear the BH 5 made a noticeable improvement. To me this is one of those must do tweaks, like dynamatting the speaker baskets and installing H-nuts or Larry's rings.

DarqueKnight

Blackhole 5 was installed in my SDA SRS's. The performance results similar to those achieved with the SDA SRS 1.2TL's, so I won't rehash them.


Figure 1. Live and learn. I used hand cutting tools to cut the first batch of BH5. This time I used my trusty
jigsaw. It took 5 minutes.

Due to the SRS's extensive bracing structure, I had to cut more pieces of BH5. Cutting with hand tools, for the SDA SRS 1.2TL, took 20 minutes with no cleanup other than throwing away the adhesive backing cover paper. Cutting took 5 minutes with the jigsaw, but required 35 minutes of cleanup due to the sawdust generated. I would rather vacuum than nurse sore hands.


Figure 2. BH5 application to the driver area.

Blackhole 5 was applied to each SRS speaker as follows:

1. A 3" x 27" strip centered 2.5" on the rear wall below the cabinet top behind the each driver row.
2. A 1.5" x 27" strip centered on both sides of the center vertical brace behind the tweeters.
3. Four 1.5" x 6" strips centered on both side walls and resting on the horizontal brace (see figure 5).

The bracing configuration behind the tweeters prevented placement of BH5 behind them.


Figure 3. Close-up of BH5 strips on center vertical brace, rear wall, and side wall.


Figure 4. Close-up of BH5 strip on vertical center brace.


Figure 5. Close-up of short BH5 strip on side wall.

Face

A table saw works even better for cutting BH5.

hochpt21

Would Sonic Barrier 1-1/4" work well (and even be worth it) for my 2A's?? Parts express didn't have Black Hole 5...and the SB was a hair cheaper.

Thanks,
Paul

hochpt21

Nevermind...I found some info on older threads about the differences.

Sonic Craft seems to be the only place online I can find BH5...has anyone purchased from there before?

zingo

SB and similar type products do work well if applied appropriately. If you are trying to absorb some of the back wave from your midwoofers, it should work great.

Moose68Bash

hochpt21 wrote: »

Nevermind...I found some info on older threads about the differences.

Sonic Craft seems to be the only place online I can find BH5...has anyone purchased from there before?

I purchased BH5 from Sonic Craft. I had no problems.

leftwinger57

Now that I've done the mods it's easy it spot a few. The collars to the rings are peaking through and then the close up of the of the allen head machine screws for the rings and changing out of the tweeters themselves.Once a vet you never forget.To cut mine I used a wood cutting board and a new blade sheet rock knife w/ a long yardstick, it worked well for me.Once the polyfill was rerolled and positioned correctly and nowhere near the passive cavity I am hearing the benfits of the mod. When you said you had to remove that artsy centerpiece from your console I had a similar but not so tramatic moment also. I was hearing a buzzing sound only on the left side and went to take off the grille cover but it wasn't coming directly out of the speaker(thankfully) what is was, i had some movies and older CDs in some thin plastic wrap in the bookcase that took on some vibrations that just passed them on. Spikes might be next.