LSi9 Mid-Bass port distortion?

ittech
ittech Posts: 3
edited December 2003 in Speakers
Just got in my LSi9's and a Denon pma-200ivr amp yesterday...

Listened to the LSi9's on my Nakamichi AV-10, and it was a no go for that amp, sounded horrible, and needed way too much volume to be at "normal" listening levels.


Hooked up the Denon, and it was a night/day difference... So much nicer sound in every way, even on my old speakers.


Anyways, I noticed while playing certain songs with a mid-bass frequency, maybe 125-300 or so hz, that there was distortion coming from the lower port...

Ex: Rebecca Pidgeon - Spanish Harlem, the bass (instrument) and vocals were very mid-bass heavy and throaty, and the lower port would make pfftb noises... goes away and sounds a lot better when you take a thumb and plug the lower bass port on the front.

This is at a louder volume, perhaps 95db, but even at lower volumes you can hear "WAY" too much bass (distorted/muddled) on these speakers...

I took them to a friends who has a NAD amp / McIntosh preamp, and we hooked them up, same thing...

We did an A/B comparison to his B&W 601's and the B&W's blew them away at half the price... not as nice bass extention, but it was way too much distorted extension on the 9's...

Then we hooked back up the Snell A III's, a class A stereophile rated 3-way tower speaker, and of course made both bookshelfs look like home theater in a box sony systems...

However, the B&W was the most "accurate" representation of almost all types of music except rap/pop, where the 9's shone big time, except for the occasional bass port noise at a louder volume.


What's the deal? did I get bum speakers? can these not handle a "full-range" signal?

I'm going to be picking up some of Mark Levinson's Red Rose Music Spirit bookshelfs, also 1000/pr at a local high end shop to do a comparison on the denon....


By the way, hooking a parametric EQ up in line with the denon and cutting down the 65-120-250 almost ALL the way completely eliminated this problem and it sounds much nicer now, and more "flat" like the b&w's... not as good midrange, but b&w is all about the in front of your superdetail midrange, which has its flaws too, just not as glaring as the 9's...


Any ideas? Anyone else have 9's? I can send you the mp3 file and you can try it yourself, it sounds really apparent with that particular song, but can hear it in a lot of other songs too.

thanks,.
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Comments

  • Frank Z
    Frank Z Posts: 5,860
    edited December 2003
    Check your PM's
    9/11 - WE WILL NEVER FORGET!! (<---<<click)
    2005-06 Club Polk Football Pool Champion!! :D
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  • fireshoes
    fireshoes Posts: 3,167
    edited December 2003
    I might be wrong on this, but it's my understanding that the two ports on the front of the LSi9 are to help reduce cabinet resonance, which helps keep the midrange clean and natural sounding. They are called ARC ports (Acoustic Resonance Control). The bass response should really only be affected by the rear Power Port. I will experiment with them at work tomorrow to see if I can duplicate your situation. In the meantime, I would consider opening the cabinets up just to make sure everything looks normal.
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  • ittech
    ittech Posts: 3
    edited December 2003
    Well I figured out what the problem is with the help of a tone generator and checking out the speaker more...

    Left speaker had to be 7DB higher than Right speaker for this issue to be audible btw...


    Basically the lower port plastic ring is "glued" i guess to the mdf hole in the cabinet...

    well, not so well apparently... a significant amount of air was felt coming from between the plastic inside of the port where it meets the cabinet inside... just at the top, like glue was applied that ran down before it dried leaving an opening.

    placing my finger on that spot covered the hole and eliminated the odd resonance / pfftb noises...

    you may want to feel your units to make sure air is coming OUT and not DOWN from that crack when you are playing some bass at volume... you unit may do this as well but it is hard to notice (i.e. only certain frequency combinations) and only certain songs.

    OK, so now I could fix it myself... But I just can't forget how much cleaner the bass was on the snell / theil / b&w / red rose speakers, in addition to great midrange / highs... In the same price range, especially used, there are some much better speakers apparently.

    Polk needs to turn off the "bass boost" button which seems to be stuck on in these speakers, thats the best way I can put it... If they do that, they would be close to perfect for say, $750... any higher and there is better speakers, and the bass boost feeling kills a lot of the musical sound.. great for HT, just not for say SACD listening...
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  • Frank Z
    Frank Z Posts: 5,860
    edited December 2003
    Well it's all in the ear of the listener I guess, but I honestly felt that my Polks out classed the B&W offerings. I think there may be something else going on with your speakers. Try contacting Ken at Polk Customer Service and discuss the problems you are having. I think that you'll be surprised at the service you get.
    9/11 - WE WILL NEVER FORGET!! (<---<<click)
    2005-06 Club Polk Football Pool Champion!! :D
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  • organ
    organ Posts: 4,969
    edited December 2003
    I've tried the LSi9 with different combination of equipments and I can say that your problem is not the speakers but the gear your running them with.

    With a combination of NAD pre amp and amp, like you said, the bass can sound almost too powerful. With my set up it didn't sound boomy or muddy just very powereful. I didn't mind this.

    With a Rotel pre amp and NAD amp the overall freq response sounds very flat and the bass was tighter and not as loud. Probably the sound you would like.

    With tubes there was less bass but it had a nice character.

    You should try them out on different equipments and to find the sound you like most. Also, try moving them farther from the front wall to decrease bass. I have mine about 2ft away from the front wall.

    Maurice
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  • Dr. Spec
    Dr. Spec Posts: 3,780
    edited December 2003
    Originally posted by organ
    Also, try moving them farther from the front wall to decrease bass. I have mine about 2ft away from the front wall.

    Maurice

    Great point here.

    I would imagine the LSi9 is an overdamped high Q design, which would provide a punchy and slightly exaggerated mid-bass in exchange for a sharp corner frequency and quick roll-off below system resonance. Moving the LSi9 well away from any corner (almost a free field environment) will probably really help balance out the character of this speaker.
    "What we do in life echoes in eternity"

    Ed Mullen (emullen@svsound.com)
    Director - Technology and Customer Service
    SVS
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  • polkatese
    polkatese Posts: 6,767
    edited December 2003
    ittech,
    have you tried a different set of 9 to see if you experienced the same problem? I am almost convinced that you have a defective 9, mine doesn't do that. If you like, email me your mp3, and I will tested out on mine. Here is my email polkatese@verizon.net
    I am sorry, I have no opinion on the matter. I am sure you do. So, don't mind me, I just want to talk audio and pie.
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  • ittech
    ittech Posts: 3
    edited December 2003
    I'm heading out for a while, but I will check back later and get you guys the mp3... If i can find a lsi9 locally i will go listen to it as well...

    thanks for the info
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