Stereo Integrity BM prototype

[Boostedrex]

This will be my review of the Stereo Integrity BM prototype. This sub differs from the producton model in that it has ferrite motor assembly versus the lightweight neo motor assembly of the production models. The T/S specs are supposed to be VERY similar if not the same. So I feel this driver should give me a good idea of what to expect from the production model that is due to start shipping soon. Here are some pics of the BM in the test box that I whipped up for it last weekend. (Forgive the sloppy cuts, this box was made in about 30 minutes. )




From the front footwell looking back. Don't mind the seat weight sensor wire.


I have the BM in a .45ft^3 sealed box that has been liberally stuffed with polyfill. This is a dual 4 ohm voicecoil sub and I have it wired down to 2 ohms. The sub is being powered by a Clarion DPX-11551 monoblock. I have the gains dialed way down as the Clarion is capable of producing 1550 watts into a 2 ohm load. The BM is only rated for 500 watts IIRC and it doesn't need nearly that much. The BM is being low passed at 100Hz with a 12db/oct slope by my DRZ-9255. I did not EQ in the subs passband at all. The nearest EQ point that is adjusted is 250Hz. The full system that is being used along with the BM is:

Head - Clarion DRZ-9255
tweets - Alpine/SS ring radiators from the SPX-Pro comps
mids - Dayton RS100
midbass - random 7" that were laying around
mid/tweet amp - Zuki ELEETS 4 channel
midbass amp - Xtant 404m bridged
sub amp - Clarion DPX-11551

I'm impressed with this sub. You wouldn't guess that it's a shallow mount if you didn't see it prior to listening. I will say that this sub isn't as transparent as the DIYMA R12 (which is my reference car sub) or the SI Mag v4. This may or may not be a bad thing as most people seem to think that the DIYMA R12 and Mag v4 seem to lack output and impact due to how transparent they are. So if you are one of the MANY people who feel that way about the R12 and Mag v4, then you'll probably enjoy the BM.

I personally really like the look of the flat piston "cone" that was used on the BM. It reminds me of the old school ppi flat piston subs from the late 90's. The cone is tough too, I have a feeling that Nick was thinking ahead when designing this sub. I wouldn't worry about this cone being delicate at all. +1 for building a tough sub! Ok, on the my review. I've tried to keep this review in a bullet format to hopefully make it easier to read.

1. Diana Krall - Temptation
- The upright bass was fulland detailed. The blending between the BM and my midbass was very smooth.
- The placement of the upright was correct when I compared it to my hoe reference system.
- The kick drum was full and very nice attack and decay to the notes.

2. Paul Oakenfold ft. Britney Murphy - Faster Kill Faster Pussycat
- This song had the classic Oakenfold driving and intense bass line. The BM had no problems reproducing this just fine.
- The initial beat is nice and strong with great attack. The flowing synth bass lines that follow are well defined and powerful.

3. Stevie Wonder - Superstition
- The kick drum is nice, full, and rich. It's firmly placed dead center with good depth.
- The bass guitar in this song is tuned down to Drop D ad was recorded with an over-driven tube pre-amp to give it that nice grit. The lower notes that fall in the BM's passband are clean and well presented. Nice separation between notes from the bass.

4. Disturbed - Deify
- As I've mentioned in other sub reviews I've done, I like to use Disturbed as they seem to use a bit lower tuned kick drum than most rock bands and they always have a nice amount of double kick bass work. This song is a great example of that. The BM seems quite happy reproducing the mix of drums and bass in this song at low, moderate, or high volume.
- The double kick bass notes are well defined with a noticeable separation between them.
- The drum solo starting right around the 3:30 mark of the song was very nicely reproduced. The notes were strong and didn't run together at all.

5. Alice in Chains Unplugged - No Excuses
- In comparison to the acoustic guitars and bass in this album, the kick drum really seems to stick out. The notes had a great feel to them and had an impressive feeling of impact.

6. Crystal Method - P.H.D.
- Well, here's my low bass test track. There are some seriously low notes on this one. The BM did a great job and even held it's composure as I pushed it up towards it's excursion limits.
- The bass line alternates throughout this track and the BM followed right along keeping everything clean with no hint of mud or boom.

7. Michael Jackson - Bad
- The kick drum and walking bass line are both presented well with great separation between notes.
- The fist 2 notes of the bass line are meant to be played with inflection. The BM portrayed that and the difference in strength of notes was quite apparent.

8. Timbaland - The Way I Are
- This track has a great strong upbeat and the BM did a great job with it. LOTS of impact and even when pushed hard the BM didn't get sloppy or start to sound strained.
- The synth bass line and drum machine beats really came through nicely.

9. Verdi - Anvil Chorus
- Low harmonics from the kettle drums are strong and placed nicely where the percussion section would be in an orchestra.
- The huge drum hits starting at 1:00 strong with just enough heft to the notes.
- At 1:40, there is a nice drum roll tat comes through with a great rumble of clearly separated notes.

10. Profokiev - Romeo and Juliet Sutie no 2 (Montagues & Capulets)
- Lots of low end presented in this piece frm the tuba, contrabassoon, upright bass, and large drums. This is a very dramatic piece of music and that feeling is maintained with the BM on sub duty.
- During the build up passages there are some strong drum hits. These sounded great and I got a feeling of big impact.


Ok, to wrap all this up. I do think that the BM gives up just a touch of performance to my tried and true DIYMA R12. But it's a small margin. However, when you compare the shallow mounting depth and 9.5-10 pound weight vs. the R12's 38lbs and 6" mounting depth, the BM becomes quite impressive. The BM also offers a better feeling of impact than the Mag v4 or DIYMA R12 IMHO. For those of you who like that "feel it in your chest" impact, the BM can do that all day. It's no Monster, but it sure doesn't sound like any of the anemic shallow subs I've heard. I will say that I don't have any experience with the top flight shallow subs though (Alto Mobile Falstaff and one other that escapes me at the moment) so I can't say that the BM is the best shallow sub on the market. But I don't think you'll be able to touch it for anywhere near the BM's price point.

Strong points:
- Shallow mounting depth
- Small box requirement
- Nice amount of available excursion
- Great impact
- Clean, accurate, and strong bass
- Lightweight driver
- Good value due to nice price point
- Behaves well even when pushed hard

Weak points:
- Not as transparent as my benchmark sub (as stated above, this might be a plus for a lot of you)
- Dual 4 ohm VC config instead of dual 2 ohm VC config. IMHO it would be easier to wire up multiple BM's if they were offered in dual 2 ohm. (Yes I'm nitpicking here)
- Not shipping yet!!!! Hurry up Nick!

If you couldn't guess by my last comment, I am picking up a pair of the production BM's for my car. The little bit of performance they give up to my R12's is GREATLY outweighed by the fact that I can fit one under each of my front seats. The more I can keep my install hidden, the better. And I think that the sonic differences wouldn't even be noticed if I didn't have both subs in the car with the ability to switch back and forth. Well, I hope this review has been somewhat helpful even though it's the length of a short novel.

Zach

[trevordj]

Thanks for the review, I am excited to get my hands on a few of these.

[1sashenka]

You rock! Thanks for the review!

[H-Audio - AKA - Here-I-Come]

Thanks for the great review. I have a install that is awaiting 2 of these. They will be replacing 2 C-Mass LS122 running on a DLS A6.

[Mless5]

Thanks for your review.

Could these be used in ported enclosures I wonder? Any approximate $$$ points?

Thanks.

[Boostedrex]

Glad I was able to help out with some info.

Mark, I'll be interested to hear your thoughts on these seeing as you are a fan of the Falstaff subs.

MLess, I'm sure Nick (Electrodynamic) will chime on the exact pricing and enclosure design, but IIRC they were supposed to be $275 shipped.

Zach

[bsvrs]

Great review! .. And at the introductory pricing, it's going to be even more tempting.

[H-Audio - AKA - Here-I-Come]

Originally Posted by Boostedrex

Glad I was able to help out with some info.

Mark, I'll be interested to hear your thoughts on these seeing as you are a fan of the Falstaff subs.

MLess, I'm sure Nick (Electrodynamic) will chime on the exact pricing and enclosure design, but IIRC they were supposed to be $275 shipped.

Zach

Yep, I'm wanting to see how they compare also. The Falstaff was a very expensive sub no matter thin or not. The Falstaff to me is very much like the DIYMA R12, just seem to have a little more impact and the attack and decay of the Falstaff is just to die for.

The BM seems to me much like the jl TW5, but cost less. This is way I'm looking to them for this install. He wants a sub to has very good output, but I need it to sound very good, as he will be competing as part of Team H-Audio and he enclosure should work great for then and they should drop right in, I hope.

The C-Mass LS122 are very nice themselves, but we are looking for a little more low-end output as the enclosure is the smallest they C-Mass recommends for the LS122, so the lowend suffers. The enclosure is under the rear sets of a 97 GMC pickup. The enclosure is about 1.2 cu.ft. total internal, which should be prefect to the BM's. The LS122 really needs to be in about .80 - 1 cu.ft each.

[trevordj]

Originally Posted by Mless5

Thanks for your review.

Could these be used in ported enclosures I wonder? Any approximate $$$ points?

Thanks.

There is a thread over at SI stating they are sealed only subs; putting them in a ported enclosure will void the warranty.

Price: $269.00 with a $40 discount for the first month they are on sale.

[Boostedrex]

Originally Posted by Here-I-Come

Yep, I'm wanting to see how they compare also. The Falstaff was a very expensive sub no matter thin or not. The Falstaff to me is very much like the DIYMA R12, just seem to have a little more impact and the attack and decay of the Falstaff is just to die for.

The BM seems to me much like the jl TW5, but cost less. This is way I'm looking to them for this install. He wants a sub to has very good output, but I need it to sound very good, as he will be competing as part of Team H-Audio and he enclosure should work great for then and they should drop right in, I hope.

The C-Mass LS122 are very nice themselves, but we are looking for a little more low-end output as the enclosure is the smallest they C-Mass recommends for the LS122, so the lowend suffers. The enclosure is under the rear sets of a 97 GMC pickup. The enclosure is about 1.2 cu.ft. total internal, which should be prefect to the BM's. The LS122 really needs to be in about .80 - 1 cu.ft each.

Awesome, thanks for the info Mark. A pair of BM's in 1.2 ft^3 gross stuffed with some polyfill should be able to reach low for days!

Speaking of the JL TW5, I've heard those in 2 different installs and I don't think that they even come close to the BM. I wasn't impressed by them at all. It was the Falstaff and the (Elegante maybe) other shallow sub that I wanted to see the BM A/B'd with.

Zach

[bafukie]

looks like another strong contender for shallow mount subwoofer.. i know it isnt out yet.. but where can we get it? (not from US btw)

[Electrodynamic]

Thanks for your review Zach. I was just about to email you asking if you've had time to listen to it a little bit more when I thought "why not hop on DIYMA and see if he posted a review yet?"

Zach hit the nail on the head as to how the driver sounds. The BM's are slightly less transparent than the Mag v4's, which will make quite a few people happy. The weirdest thing about the BM mkIII's is how they perform vs. how they are perceived when handled. They'll weigh less than 12 lbs, look kind of funny because they're so shallow, but they'll sound like a very solid "normal" depth subwoofer.

As trevordj said, the new BM's are a sealed-only design. Every ounce of their design was poured into sealed enclosures only, which means they will not perform well in any other type of enclosure, especially the vented type (std bass reflex or bp's). Technically they'll work IB, but power handling would be in the 50 watt range due to the compliance of the driver. The best thing to do with these drivers is to put them in their tiny recommended sealed enclosure. That way you'll get the exact results we engineered the driver to provide (sonic and low frequency abilities along with power handling).

Production should be wrapped up by the end of this week. Once I hear/see that they're done being assembled officially I'll send out another newsletter and also post it on here.

[6262ms3]

So. @#$!-ing. Excited!!!

[Boostedrex]

Originally Posted by bafukie

looks like another strong contender for shallow mount subwoofer.. i know it isnt out yet.. but where can we get it? (not from US btw)

Stereo Integrity is Nick's website. You can order the BM's from there once they're ready for shipment.

Nick, I was hoping you'd see this review. I was going to email you this morning and let you know I had posted it. Go figure. Also, the big NorCal/Bay Area meet is this weekend and I'll have the BM there for people to check out either in my car or in theirs if they'd like. Good job on this sub bro!

Zach

[trunks9_us]

Originally Posted by Boostedrex

Stereo Integrity is Nick's website. You can order the BM's from there once they're ready for shipment.

Nick, I was hoping you'd see this review. I was going to email you this morning and let you know I had posted it. Go figure. Also, the big NorCal/Bay Area meet is this weekend and I'll have the BM there for people to check out either in my car or in theirs if they'd like. Good job on this sub bro!

Zach

Great review I might be getting some for under my seats now to have extra bass.

[fish]

Great review Boosted, thanks for taking the time out for us. You said you crossed it at 100hz, would you mind raising the lowpass until the BM begins to break up & report your findings? Thought about using these for sub/midbass is why I ask.

Nick or Zach, is rec volume of .5cf before or after driver displacement? What is driver's displacement?

[Boostedrex]

Fish, yeah I'll see about finding the upper limits of the BM. Just remember that going too much higher will start to get you into the lowest part of the male vocal spectrum. So depending on where you place the BM's you could have some issues.

And .5 ft^3 is after displacement.

[Electrodynamic]

The displacement of the BM mkIII is 0.05 ft^3. And the recommended enclosure of 0.5 ft^3 is after displacement. Steven is building enclosures for the Lexus IS guys that are 0.3 ft^3 along with a SS Variovent with great results. The test box that I built was 0.46 ft^3 sealed before the driver was placed in it, but I used fiberglass insulation and polyfill to make up for the lack of actual internal volume and it worked nicely. So as long as you keep the enclosure between 0.46 and 0.55 ft^3, you'll be fine. Well, with stuffing, that is. We always recommend stuffing the inside of your enclosure - preferably with fiberglass insulation and polyfill. If you go smaller than what we recommend you'll need to use a Variovent in order to make up for the thimble-sized super tiny enclosure.

FWIW: We don't recommend crossing the driver over any higher than 250 Hz at all, as at that is the upper frequency limit of the driver. Normal subwoofer use should be kept below 150 Hz.

[Boostedrex]

FWIW, I'll probably be dropping the LP filter point in my install once I get the pair of production models installed. Seeing as they'll be mating up with a pair of 8" midbasses in sealed pods, I more than likely won't need them to extend up as high as I do now.

[94VG30DE]

Originally Posted by Electrodynamic

The displacement of the BM mkIII is 0.05 ft^3. And the recommended enclosure of 0.5 ft^3 is after displacement. Steven is building enclosures for the Lexus IS guys that are 0.3 ft^3 along with a SS Variovent and he got great results. The test box that I built was 0.46 ft^3 sealed before the driver was placed in it, but I used fiberglass insulation and polyfill to make up for the lack of actual internal volume and it worked nicely. So as long as you keep the enclosure between 0.46 and 0.55 ft^3, you'll be fine. Well, with stuffing, that is. We always recommend stuffing the inside of your enclosure - preferably with fiberglass insulation and polyfill. If you go smaller than what we recommend you'll need to use a Variovent in order to make up for the super tiny enclosure.

FWIW: We don't recommend crossing the driver over any higher than 250 Hz at all, as at that is the upper frequency limit of the driver. Normal subwoofer use should be kept below 150 Hz.

Please excuse my noob-ery, but as I understand it an aperiodic vented enclosure responds much the same way a ported one would, yet you strongly recommended against porting earlier in the thread. Do you mind elaborating on how you are tuning the vent so that you get away with it? 0.5ft^3 is tiny, but 0.3 is just a miracle :-)

[Electrodynamic]

Originally Posted by 94VG30DE

Please excuse my noob-ery, but as I understand it an aperiodic vented enclosure responds much the same way a ported one would, yet you strongly recommended against porting earlier in the thread. Do you mind elaborating on how you are tuning the vent so that you get away with it? 0.5ft^3 is tiny, but 0.3 is just a miracle :-)

An AP alignment behaves significantly different than a standard bass reflex alignment. Steven isn't "tuning" the vent by modifying the stuffing density of the variovent. He is simply dropping the factory variovent into the enclosure. You can "tune" variovents by modifying the stuffing density inside the vent itself, but you're not tuning the enclosure to a specific frequency like you would tune a standard ported enclosure because technically a variovent, which is very close to an aperiodic enclosure, isn't a ported enclosure. Variovents damp the enclosure even further than can be done by traditional methods of stuffing an enclosure. The overall impedance of the subwoofer system is lowered with a variovent unlike a ported enclosure where your overall impedance is higher since you have two impedance swings instead of one swing for a sealed alignment. Search the net for the Dynaudio Variovent document that shows the impedance plot and compare that plot to a standard bass reflex alignment and that will demonstrate how different the two alignments are. It's easier to think of an aperiodic alignment as enlarging a sealed enclosure without making it physically bigger. A standard ported alignment is a different animal all together because you're tuning the enclosure volume to a specific frequency. And to get the BM to benefit in any way by porting it you would need to make the enclosure at least 1.5 ft^3 in internal volume, which would destroy the power handling of the driver further negating one of the benefits of making the enclosure ported (if you can port a driver, ideally you want to keep your power handling and extend the F3 of the driver). If you gain 3 dB by porting a BM but lose 50% of the power handling of the driver, it doesn't make much sense to do it...especially when the enclosure volume just got 150% bigger. But long story short, an AP vent doesn't reduce the power handling of the system by a significant margin. Nor does it tune the enclosure to a specific frequency. Steven and I discussed using one in his enclosures because his enclosure size was so tiny. If you can fit 0.5 ft^3 sealed, you don't have to worry about using a Variovent.

[sundownz]

Nice review -- the new BM is a great sounding sub indeed.

[94VG30DE]

Originally Posted by Electrodynamic

An AP alignment behaves significantly different than a standard bass reflex alignment. Steven isn't "tuning" the vent by modifying the stuffing density of the variovent. He is simply dropping the factory variovent into the enclosure. You can "tune" variovents by modifying the stuffing density inside the vent itself, but you're not tuning the enclosure to a specific frequency like you would tune a standard ported enclosure because technically a variovent, which is very close to an aperiodic enclosure, isn't a ported enclosure. Variovents damp the enclosure even further than can be done by traditional methods of stuffing an enclosure. The overall impedance of the subwoofer system is lowered with a variovent unlike a ported enclosure where your overall impedance is higher since you have two impedance swings instead of one swing for a sealed alignment. Search the net for the Dynaudio Variovent document that shows the impedance plot and compare that plot to a standard bass reflex alignment and that will demonstrate how different the two alignments are. It's easier to think of an aperiodic alignment as enlarging a sealed enclosure without making it physically bigger. A standard ported alignment is a different animal all together because you're tuning the enclosure volume to a specific frequency. And to get the BM to benefit in any way by porting it you would need to make the enclosure at least 1.5 ft^3 in internal volume, which would destroy the power handling of the driver further negating one of the benefits of making the enclosure ported (if you can port a driver, ideally you want to keep your power handling and extend the F3 of the driver). If you gain 3 dB by porting a BM but lose 50% of the power handling of the driver, it doesn't make much sense to do it...especially when the enclosure volume just got 150% bigger. But long story short, an AP vent doesn't reduce the power handling of the system by a significant margin. Nor does it tune the enclosure to a specific frequency. Steven and I discussed using one in his enclosures because his enclosure size was so tiny. If you can fit 0.5 ft^3 sealed, you don't have to worry about using a Variovent.

Ok, very thorough explanation. Thank you for that. I think I have a better idea what's going on. FWIW, this is the PDF I found on the Dynaudio Variovent: http://diyaudioprojects.com/Technica..._variovent.pdf

/Thread may resume original direction

[fish]

Thanks Zach & Nick for your responses. I'm throwing around the idea of using these in my doors up to 200hz.

[Boostedrex]

No worries, I'm glad that question was asked. It opened up even more install possibilities for the BM IMHO. If you can fit it in an even smaller box so long as the variovent is used, then that opens up this sub as a choice to more people possibly. IME, there aren't enough subs that work in very small boxes that are able to sound good and provide enough output to be worthwhile.