LSi15 Woofer mod, if a DB840 is good, would an MM840 be better?

I just picked up a mint set of LSi15 towers on Craigslist really cheap, so I can justify throwing a few hundred more at them, to milk the most performance from them.

I'm probably going to upgrade the woofers and the crossovers. The consensus on the forums seems to be that the Polk DB840 SVC woofer is the replacement driver of choice for most.

My question is, would the MM840 be an even cleaner, tighter, louder upgrade than the DB840? Or, what about a Focal 21A1 8, or a Focal 21-V2 8? Or a JL Audio 8W3V3-4? Just seems like those are higher quality choices than a DB series Polk driver. Any reason why one of those more expensive drivers wouldn't be better?
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Comments

  • hochpt21
    hochpt21 Posts: 5,423
    I asked the same question when I did mine. Feedback basically said it hadn't been done. I went with what had been done and was very pleased with the results.

    I know that doesn't really answer your question, but the 840 was great.
    2 ChannelTurntable - VPI Classic 2/Ortofon 2M BlueAmplification - Rogue Audio Cronus Magnum II, Parks Audio Budgie PhonoSpeakers - GoldenEar Triton 17.2 Home TheaterDenon AVR-X3300W; Rotel RMB-1066; Klipsch RP-280F's, Klipsch RP-450C, Polk FXi3's, Polk RC60i; Dual SVS PB 2000's; BenQ HT2050; Elite Screens 120"Man CaveTurntable - Pro-Ject 2.9 Wood/Grado GoldAmplification - Dared SL2000a, McCormack DNA 0.5 DeluxeCD: Cambridge AudioSpeakers - Wharfedale Linton 85th Anniversary; LSiM 703; SDA 2A
  • F1nut
    F1nut Posts: 49,704
    Any reason why one of those more expensive drivers wouldn't be better?

    Because the good folks at Polk took the time to figure out that the DB840 was the best upgrade replacement.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."


    President of Club Polk

  • davidhawke30
    davidhawke30 Posts: 2
    edited February 2016
    F1 Nut... So the DB840 is an official recommendation of the Polk engineers? Can you please post the link to the write-up of their "official recommendation" ? I'd like to read their findings. Also, was that recommendation published prior to the release of the MM series driver?
  • pitdogg2
    pitdogg2 Posts: 24,471
    Link may be a goner it was on the old forum.... Like a lot of stuff we lost with the switch to vanilla.
  • EndersShadow
    EndersShadow Posts: 17,517
    F1 Nut... So the DB840 is an official recommendation of the Polk engineers? Can you please post the link to the write-up of their "official recommendation" ? I'd like to read their findings. Also, was that recommendation published prior to the release of the MM series driver?

    This was information given by a forum member that doesnt come around much that worked with the Polk engineers directly and this was discussed in person and the recommendation made to install the Db driver as well as add dynamat around the port tube. There is no "official" write up on it from Polk or anyone else and no real testing such as measurements, etc.

    But given the number of people that have done the mod and felt they benefited from it, I'd just trust it and go.

    I've seen one person use the MM drivers and that was in a LSi 25 scenario. Otherwise everyone just uses the db driver.

    Your welcome to make your own decision, but I trust the words of that forum member, and I have done the mod and can tell you it makes a BIG difference.
    "....not everything that can be counted counts, and not everything that counts can be counted." William Bruce Cameron, Informal Sociology: A Casual Introduction to Sociological Thinking (1963)
  • mikeyb128
    mikeyb128 Posts: 2,885
    I did this mod and was well worth the 150 bucks it cost. I would go with what is proven to work and sit back and enjoy the tunes.
    2 channel:
    Bryston 4B3, Bryston BDA3, Cary SLP05, Shanling CDT1000SE with parts conneXion level 2 mods, Nottingham analogue ace space 294, soundsmith Carmen MKii, Zu DL103 MKii, Ortofon MC 20 MKii, Dynavector XX2 MKii, Rogue Audio Ares, Core power technologies balanced power conditioner, Akiko Corelli power conditioner with Akiko Audio HQ power cable, Nordost heimdall 2, Frey 2, interconnects, speaker and power cables, Focal Electra 1028 BE 2, Auralic Aries Femto, Black diamond racing cones, ingress audio level 1 roller blocks, JL Audio E110 with Auralic subdude, Primacoustics room treatments.
    Theater:
    Focal Aria 926,905,CC900, SVS PB ultra x2. Pioneer Elite SC85, Oppo BDP93, Panamax M5400PM, Minix neox6, Nordost Blue heaven LS power cables.

  • K_M
    K_M Posts: 1,627
    edited February 2016
    We did this mod a while back, and I think someone did measurements that backed up what it sounded like to us also. We saw that thread about it years ago.

    http://forum.polkaudio.com/discussion/89529/db840-sub-in-lsi15s-replace-the-stock-8-driver/p1

    It seemed that the bass was nearly identical as far as volume and deepness, but it was a good bit less boomy sounding in the upper bass sounds.

    As far as using another better quality woofer, there are a few things to consider.

    The bass port is very close to the stock woofer, and can not be extended for deeper bass sounds.

    The actual volume of the bass section on the Lsi15 is quite compact, and not many woofers will work better in this small a volume.

    We liked the Db840 "upgrade", but wondered why they did not use it to begin with?
  • EndersShadow
    EndersShadow Posts: 17,517
    K_M wrote: »

    We liked the Db840 "upgrade", but wondered why they did not use it to begin with?

    Well to state the obvious cost. I also think the LSi line came out before this driver... And let's be honest, I wouldn't think its something MOST people would notice. I hold no illusion that we are are standard consumers lol....
    "....not everything that can be counted counts, and not everything that counts can be counted." William Bruce Cameron, Informal Sociology: A Casual Introduction to Sociological Thinking (1963)
  • K_M
    K_M Posts: 1,627
    K_M wrote: »

    We liked the Db840 "upgrade", but wondered why they did not use it to begin with?

    Well to state the obvious cost. I also think the LSi line came out before this driver... And let's be honest, I wouldn't think its something MOST people would notice. I hold no illusion that we are are standard consumers lol....

    Hmm.......trying to imagine how that would matter.... o:) Sarcasm Angel!
  • skrol
    skrol Posts: 3,330
    I had looked at the specs for various Polk automobile subs comparing to the DB840. I had hoped to simulate with some speaker enclosure design software. The DXi804 looked like it might be a closer match. It isn't just the quality of the sub. The specs (Thiele / Small Parameters) are a bit different and may not match the LSi15's sub enclosure. The MM will is also SPL spec'd at 90dB vs the DB840's 85dB. I have a hard enough time taming the bass with the DB840.

    If anyone is feeling ambitious, I attached a spreadsheet with the Polk sub parameters that I collected. Perhaps someone can simulate for the LSi15 enclosure and report back.
    Stan

    Main 2ch:
    Polk LSi15 (DB840 upgrade), Parasound: P/LD-1100, HCA-1000A; Denon: DVD-2910, DRM-800A; Benchmark DAC1, Monster HTS3600-MKII, Grado SR-225i; Technics SL-J2, Parasound PPH-100.

    HT:
    Marantz SR7010, Polk: RTA11TL (RDO198-1, XO and Damping Upgrades), S4, CS250, PSW110 , Marantz UD5005, Pioneer PL-530, Panasonic TC-P42S60

    Other stuff:
    Denon: DRA-835R, AVR-888, DCD-660, DRM-700A, DRR-780; Polk: S8, Monitor 5A, 5B, TSi100, RM7, PSW10 (DXi104 upgrade); Pioneer: CT-6R; Onkyo CP-1046F; Ortofon OM5E, Marantz: PM5004, CD5004, CDR-615; Parasound C/PT-600, HCA-800ii, Sony CDP-650ESD, Technics SA 5070, B&W DM601
  • K_M
    K_M Posts: 1,627
    edited March 2016
    skrol wrote: »
    I had looked at the specs for various Polk automobile subs comparing to the DB840. I had hoped to simulate with some speaker enclosure design software. The DXi804 looked like it might be a closer match. It isn't just the quality of the sub. The specs (Thiele / Small Parameters) are a bit different and may not match the LSi15's sub enclosure. The MM will is also SPL spec'd at 90dB vs the DB840's 85dB. I have a hard enough time taming the bass with the DB840.

    If anyone is feeling ambitious, I attached a spreadsheet with the Polk sub parameters that I collected. Perhaps someone can simulate for the LSi15 enclosure and report back.

    I think the db840 42hz spec is the correct one. I see they list 2 other numbers.
    Rember also, not only is the box size significant, but the Vent, is limited physically, by it's close placement to the speaker magnet.
    It can not be extended any significant amount, to lower the box tuning frequency much at all without coming onto contact with the woofer magnet.
    That may be more of the limitation than anything else, in regards to getting deeper bass.

    Another issue, the Lsi bass enclosure, is quite small. I think about .72-.75 cuft.

    That limits low end extension with many woofers right from the get go!

    I do not think that the 90db sensitivity in itself is a huge issue, but with the the stock woofer and the db840 have an excess of energy in the 90-150 hz range.

    The deepest bass is several decibels lower in level in comparison.
    At our house, we experimented a good bit, with this stuff and even tried running the stock Lsi15 woofers, from an outboard sub amp.

    Boosting the overall level of the stock side mounted "sub", a bit, and rolling off the upper bass made it a lot more listenable overall.
    The deep bass is there, but the upper bass is simply over powering.

  • K_M
    K_M Posts: 1,627
    edited March 2016
    8iy32g0yq32z.jpg


    We measured the stock woofer very near field, and got this.

    as you can see 42 Hz was the frequency of the box tuning and the red curve is the port, the green the woofer itself.
    The levels are not accurate as they were measured very close.
  • K_M
    K_M Posts: 1,627
    px3wblcgu3rs.jpg

    This I believe is the stock woofer, with stock crossover, and one we modded to create the curve that is lower in level for the upper bass.
    Looking for all the other files we created, but not finding them all!

    We had several dozen comparing stock woofer, with db840 and other mods we experimented with.

    In the end I think the one above with the rolled off upper bass, was almost exactly like the db840 but using the stock crossover.
  • K_M
    K_M Posts: 1,627
    To answer the OP question, yes there are technically better woofers available, including the MM840, but the physical limitations of the port almost contacting the woofer magnet as is, precludes extending it more than a small fraction of an inch, hence not being able to take advantage of deeper bass tuning with a longer port.
  • Hi all, copying it here from.a other thread.

    Just registered here to say that although the DB840 upgrade does make the LSi15 bass sound tight and nice, the MM840 sub destroyed the DB840 in my LSi15s with modded crossovers. Whereas the db840 makes the bass tight, the mm840 takes the bass even deeper, punchier, more dynamic and even thunderlike. I'd recommend anyone considering db840 swap to try mm840 as well. Make sure you use all 8 screws to make sure your mighty mm840 is secured tight in there.

    I should note that the crossovers in my LSi15s are modded, this is yet another way to make your LSi15s sound much better. Just in case, I drive my LSi15s with a pair of fully modded Adcom GFA-565 monoblocs.
    qudh67zgcj0y.jpeg
    svin7c39fc51.jpeg

    Cheers.
  • F1nut
    F1nut Posts: 49,704
    The DB840 mod was designed and tested by Polk engineers to blend with the rest of the speaker. Something to consider.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."


    President of Club Polk

  • Well it seems it was more of an opinion expressed by someone at Polk concerning LSi woofer upgrade - as stated by some of the Polk forums members.

    There's something else to consider here - the crossovers for the LSi15 speakers were designed and tested by Polk as well and there is a lot to be tweaked there. Check vr3 mod among others.

    Lsi15 is a very good speaker as when carefully tweaked it sounds way, way better. Cheers for Polk designers and testers for that.
  • F1nut
    F1nut Posts: 49,704
    One of the members worked with the Polk engineers in developing the mod.

    One can modify and improve most speakers because companies have to work with price points.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."


    President of Club Polk

  • K_M
    K_M Posts: 1,627
    mm840lsi15 wrote: »
    Well it seems it was more of an opinion expressed by someone at Polk concerning LSi woofer upgrade - as stated by some of the Polk forums members.

    There's something else to consider here - the crossovers for the LSi15 speakers were designed and tested by Polk as well and there is a lot to be tweaked there. Check vr3 mod among others.

    Lsi15 is a very good speaker as when carefully tweaked it sounds way, way better. Cheers for Polk designers and testers for that.

    Did you try to alter the box tuning frequency at all?
    I posted a graph above showing the measured response of one pair of our Lsi15 with the stock woofer before the db840 change.
  • Airplay355
    Airplay355 Posts: 4,298
    Did you modify the power port tube to accommodate the depth of the larger MM woofer?
  • K_M wrote: »
    mm840lsi15 wrote: »
    Well it seems it was more of an opinion expressed by someone at Polk concerning LSi woofer upgrade - as stated by some of the Polk forums members.

    There's something else to consider here - the crossovers for the LSi15 speakers were designed and tested by Polk as well and there is a lot to be tweaked there. Check vr3 mod among others.

    Lsi15 is a very good speaker as when carefully tweaked it sounds way, way better. Cheers for Polk designers and testers for that.

    Did you try to alter the box tuning frequency at all?
    I posted a graph above showing the measured response of one pair of our Lsi15 with the stock woofer before the db840 change.

    I refitted the dampening material around the tube and all around the box.
    Airplay355 wrote: »
    Did you modify the power port tube to accommodate the depth of the larger MM woofer?

    I did not modify the power port as the mm840 fits nicely without any modification. I wired the subs to 2ohms. The nominal speaker impedance is around 3 ohms now but you know the impedance goes up and down with the frequency played by the speaker. I use my LSi15 with mm840 mod with my Adcom GIA-275, Adcom GCA-510, Adcom GFA-565 monos and GFA-5802 with no issues. Please let me know if you'd like to see additional pics.
  • Airplay355
    Airplay355 Posts: 4,298
    Oh cool, I thought you'd need more space in there. How come you didn't get the SVC version so you didn't have to lower the impedance?
  • Airplay355 wrote: »
    Oh cool, I thought you'd need more space in there. How come you didn't get the SVC version so you didn't have to lower the impedance?

    I couldn't find the SVC version anywhere so I went for the DVC and from what I could hear, the 2ohm wired DVC sub sounded way punchier and better to my ears that when wired to 8ohm impedance. Having lower impedance didn't really bother me as I use nicely tweaked Adcoms with these beautiful speakers and Adcoms are known to control low impedance speakers with no issues.
  • b1u7niif5b3o.jpg
    MM840LSi: Regarding your LSi15 woofer upgrade to the MM840, how did you get it to fit into the cabinet? Did you need to modify? I've got the stock driver pulled out and the MM840 driver diameter is 1/4" larger meaning it does not fit into the recessed mount where the stock driver seats. Stock driver flange diameter measures 8.22" but the MM840 one-piece flange measures 8.47" (about 1/4" larger).

    I can get creative, by fabricating a spacer ring or gasket but wonder why you didn't mention any issue? What am I missing?
  • txcoastal1
    txcoastal1 Posts: 13,124
    The original mob was a DB840 not the MM840
    2-channel: Modwright KWI-200 Integrated, Dynaudio C1-II Signatures
    Desktop rig: LSi7, Polk 110sub, Dayens Ampino amp, W4S DAC/pre, Sonos, JRiver
    Gear on standby: Melody 101 tube pre, Unison Research Simply Italy Integrated
    Gone to new homes: (Matt Polk's)Threshold Stasis SA12e monoblocks, Pass XA30.5 amp, Usher MD2 speakers, Dynaudio C4 platinum speakers, Modwright LS100 (voltz), Simaudio 780D DAC

    erat interfectorem cesar et **** dictatorem dicere a
  • ZombieBeaver
    ZombieBeaver Posts: 3
    edited December 2019
    Thanks txcoastal1. The original mod for this speaker was the DB840, but this thread was questioning the MM840 (which I just happen to have two of sitting on the shelf). I just had a question about fitment from the previous poster in Dec 2017 that had done it.

    Now that even the MM840 sub is discontinued, there are even threads about putting the MM842 sub in. There they claim it is "drop in", but considering what I'm seeing with the MM840, I'm not sure I'd necessarily believe it.

    Decided to be proactive so I got my hands on some 0.22" thick mass-loaded vinyl sheet that I can easily cut into a spacer ring. This should stand off the driver the necessary 0.22" so that the OEM gasket supplied with the MM840 will seal nicely. Once I get some longer screws I'll secure the drivers then it's off to the listening room.

    I know I'm late to the LSi15 party, but for anyone stopping by decades late, hopefully these posts supply some info regarding possible upgrade paths..
  • K_M
    K_M Posts: 1,627
    edited December 2019
    Thanks txcoastal1. The original mod for this speaker was the DB840, but this thread was questioning the MM840 (which I just happen to have two of sitting on the shelf). I just had a question about fitment from the previous poster in Dec 2017 that had done it.

    Now that even the MM840 sub is discontinued, there are even threads about putting the MM842 sub in. There they claim it is "drop in", but considering what I'm seeing with the MM840, I'm not sure I'd necessarily believe it.

    Decided to be proactive so I got my hands on some 0.22" thick mass-loaded vinyl sheet that I can easily cut into a spacer ring. This should stand off the driver the necessary 0.22" so that the OEM gasket supplied with the MM840 will seal nicely. Once I get some longer screws I'll secure the drivers then it's off to the listening room.

    I know I'm late to the LSi15 party, but for anyone stopping by decades late, hopefully these posts supply some info regarding possible upgrade paths..

    Sadly there is not simple way to get great deep bass AND not boomy bass from the Lsi15.
    The DB840 for sure makes it less "boomy", but still lacks deep bass wise, even compared to the Rta11t speakers.

    The issue (obviously) is a VERY small bass box volume of only about .75 cu ft.

    So any 8" woofer that can truly do deep bass well, will either be not very efficient, or require a larger air volume (about 1.25-1.5 cu ft) instead of the tiny .75 we have to work with.

    Actively amping the woofers (by disconnecting from the crossover) with a stand alone sub amp DOES work, especially if there is an active deep bass eq built in, as many have, but complicates hook up and basically makes a semi-franken speaker out of it.
  • Thanks for the posters in this thread. I was able to get the MM840's installed without much issue after making a 0.2" thick MLV gasket and sourcing the proper screws (need longer ones @ 1.5" to get the MM840 in, and the thread pitch is non-standard). After much searching, it turns out that SPAX construction screws as seen pictured match the diameter and pitch of the stock screws, nothing else I could find did. Don't even need to predrill the 4 extra holes for these; just screw them in. Few pictures are attached. The stock grill no longer fits securely since the new driver is stood off by about 3/8" more (plus the MM840 has longer excursion capability). I will just leave the grills off, or eventually put a nice looking aftermarket one on.

    REGARDING THE SOUND: It IS less boomy in my 12'x14' room, but as mentioned I feel the quantity of bass is also slightly less. Basically the bass is more controlled and just as deep, it's just cleaner and less obtrusive and therefore makes it seem like there is slightly less of it. It's still a nice overall balance, and one I prefer over stock. I had the drivers sitting around spare so for the price of the screws and some of my time, it was a worthwhile enhancement.

    Removing stock grill without damage:
    ob0elq2exd3n.jpg
    ntfilb2dbfgm.jpg

    Stock driver seated depth:
    d8icgd8mpl9y.jpg

    Cutting spacer mat:
    vsqkxu9vp02t.jpg

    Spacer mats and gasket seated:
    cwtda5hmkv9k.jpg

    Speaker connection:
    j12dm3zb9z3r.jpg

    Driver installed:
    pp4dbjoou0tg.jpg

    Stock grill protrudes (with a few small tacks of hot glue it would probably stay in place):
    34sc8plrognt.jpg
  • txcoastal1
    txcoastal1 Posts: 13,124
    Nice job, and thanks for posting pics...nice pics too

    Happy New Year
    2-channel: Modwright KWI-200 Integrated, Dynaudio C1-II Signatures
    Desktop rig: LSi7, Polk 110sub, Dayens Ampino amp, W4S DAC/pre, Sonos, JRiver
    Gear on standby: Melody 101 tube pre, Unison Research Simply Italy Integrated
    Gone to new homes: (Matt Polk's)Threshold Stasis SA12e monoblocks, Pass XA30.5 amp, Usher MD2 speakers, Dynaudio C4 platinum speakers, Modwright LS100 (voltz), Simaudio 780D DAC

    erat interfectorem cesar et **** dictatorem dicere a
  • Even with the DB840 upgrade I have never been happy with the low/ mid bass from my LSI15s. It seems that the 8" woofer was designed in to allow the speakers to be played without a sub but I think most people do use a sub anyway. Has anyone tried replacing the stock woofer with more of a midrange/midbass type speaker? I love the highs from these speakers and they are great for movies but for rock music or anything with mid bass they are lacking big time. A sub can fill in the lower frequencies but the from about 80-150hz these speakers just don't cut it. I know that the mid bass modules (MBM) have become pretty popular these days and I was considering it. I know these modules are sort of like a subwoofer but they use a different type of driver. One with a lighter cone material and powerful magnet for the mid bass punch. I had the thought of why not try one of these type drivers in the LSI15s. That way you have a driver more suitable for mid bass and then just allow the sub to take over below 50-60hz. Set your AVR crossover at 80 and then I think the LSIs cross the 8" woofer at 150Hz. Also running the AVR crossover higher will take some load of the rest of the drivers in the speaker. I was looking at some Dayton Audio mid bass speakers that might work in a small ported enclosure like the LSIs. It seems like it could be a cheap experiment. Any thoughts on this? Anyone tried others speaker besides Subs?