lots of motion no bass. - diyAudio
Go Back   Home > Forums > Loudspeakers > Subwoofers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 23rd November 2007, 04:47 AM   #1
diyAudio Member
 
Join Date: Oct 2004
Send a message via AIM to rx7speed
Default lots of motion no bass.

I have one of the older infinity perfect 10.1" subs. not the DVC type. right now it's sitting in a junk sealed walmart enclosure that I have braced up. for damping I had an old sound damping mat that came out of my car. Took the thick stuff out and lined the walls of the sub with that then took an old pillow gutted it and used it as fill. yes I know cheap and ghetto but so far it has made a world of difference with the sound quality. my problem though comes with the amount of bass it is giving off.
I admit I don't have an actuall sub amplifier for it yet and so just for at least testing I've been running it off a nakamichi receiver. the sub is setup on the left channel and then on the right I just left my infinity sm122. For sound I'm trying the boston accoustics bass test.
What I'm noticing is when I turn it up to about 1/4-1/3 volume it is moving the sub almost to it's peak excursion limits during the deep bass parts, but yet it doesn't seem like a whole lot of sound is comming out. when I switch it from the left to the right channel the sm122's woofer is hardly moving and yet all of a sudden I hear a loud amount of bass, my floor vibrates like crazy and yet still that woofer is just hardly moving. go back to the perfect and it gets quite but yet that thing is vibrating like crazy.

how can that speaker be vibrating like that and yet give off hardly any sound? I admit I'm an DIY audio noob but I figured with that much excursion there would be more output involved. Is there anything that can be done to get the output up or something I need to check. the other worry I have is that reciever I believe is only 25w and yet to be able to push the sub to that much excursion already makes me worry for if I get any real powre on that sub that it is going to make it bottom out. please guys any help?
  Reply With Quote
Old 23rd November 2007, 06:38 AM   #2
dnsey is offline dnsey  United Kingdom
diyAudio Member
 
Join Date: Mar 2004
Location: Shropshire, England
How does the Infinity sound on the left channel? Are both channels fed with the same (mono) signal?

Quote:
all of a sudden I hear a loud amount of bass, my floor vibrates like crazy
<snip>
Quote:
to be able to push the sub to that much excursion already makes me worry for if I get any real powre on that sub
Why would you want any more power?
  Reply With Quote
Old 23rd November 2007, 07:07 AM   #3
BHTX is offline BHTX  United States
diyAudio Member
 
BHTX's Avatar
 
Join Date: Feb 2006
Anyone have any T/S parameters on this thing? I don't remember them having all too low of a Qts or anything, but I'm not exactly sure.

Also, keep in mind.. those boomy/harsh SM122's are efficient as hell. And vented too, if I remember correctly. If you're not willing to get rid of them for some strange reason, at least consider some modifications, altho I'm not so sure it'd even be worth it imo. I seem to remember the cabinets and construction being pretty unsatisfactory, to say the least. Good and loud tho. Probably great for rock.
  Reply With Quote
Old 23rd November 2007, 07:40 AM   #4
diyAudio Member
 
Join Date: Oct 2004
Send a message via AIM to rx7speed
dsney I wouldn't want more power untill really. Just find it odd that a sub that should be able to handle 350watts is reaching it's excursion limits on only less then 25w. if anything I would rather not have more power for those lower notes like that.

both are being fed a mono signal from the same receiver just one is on the left channel one is on the right. sound wise both are fairly clean other then the left (perfect) sounds like it has a pinhole leak where the connector box fits in.


BHTX the specs on the perfect 10.1 (lifted from winisd)
qts .420, vas 32.10, fs 28.35, xmas 14.1mm, qms 8.830, qes .441.

I haven't had too much of an unsatisfactory experience so far with the sm122's other then they make any other speaker a wisper and some weird frequency spikes on some voices, and that they are a little bright sounding with a little more bass then I prefer. hasn't been boomy or harsh sounding though. but then again I don't crank them either as I don't have that large of a room so chances are I'm not letting their flaws come to bear that much. Main reason I have them is I'm broke and couldn't find much else for 50 bucks that sounded as decent as these except for a pair of the RSa line of speakers. I do know though that the cabs on the sm122's are a lot more lively then the RSa speakers. though I'm not a full fledge audio nut with a lot of experience either so what is decent to me might be junk to others. soon enough though I am at least going to damped the cabs if not brace them as best as I can.



how is it though that my perfect is sitting there moving close to an inch total travel and yet the sm122's are moving if even 1/4" total travel and I would guess even less then that and yet can easily put out more volume.
  Reply With Quote
Old 23rd November 2007, 08:25 AM   #5
BHTX is offline BHTX  United States
diyAudio Member
 
BHTX's Avatar
 
Join Date: Feb 2006
Quote:
Originally posted by rx7speed
how is it though that my perfect is sitting there moving close to an inch total travel and yet the sm122's are moving if even 1/4" total travel and I would guess even less then that and yet can easily put out more volume.
Basically, what it all boils down to is.. Those 12's in the SM122's are pretty sensitive, and in a large bass reflex cabinet on top of that..

On the other hand, the kappa perfect 10.1's are very inefficient, in a small sealed enclosure (probably too small too), and much less effective cone area for a 10" subwoofer versus a more efficient 12" woofer. Like I said, it all comes down to sensitivity, plus the fact that one is in a vented cab versus sealed, which can also be considered sensitivity in regards to system as a whole.

Welcome to the world of loudspeaker transducers and speaker systems, where anything and everything is a matter of trade-offs. For a 10" woofer to have the ability to provide deep bass in a small sealed enclosure at decent volume levels, it's going to have to have a lot of moving mass and a good amount of maximum excursion, since the cone itself will be required to move MUCH more than a larger vented system with higher efficiency. If that 10" infinity were more efficient, it wouldn't go anywhere near as low as it does in such a tiny sealed box. How many big amplified rock concerts have you been to? (tinnitus and ear damage here ) ..Those 18's they're using are hardly moving at all, yet it's so loud you can hardly stand it, while your gut and testicles vibrate from yards away. If you were able to go up to any one of these large woofers without a grille and take a close look at it while it was cranking so darn loud, you'd probably be amazed at just how little it was actually moving. However, as a result, these massive sound systems used in concerts (pro sound) don't go as low as one might think. Most of them begin rolling off around 50-60 Hz, and are almost always rolling off very steeply much below 40 Hz.

Like I've seen someone else say in their posts several times around here (can't remember who it was tho)... I can't remember their exact words either, but when you think about it, it's pretty much correct 100% of the time under normal conditions..

Choose any two of the following, but you can't have all three:
1. small size
2. high efficiency
3. very low frequency response
  Reply With Quote
Old 23rd November 2007, 11:08 PM   #6
Svante is offline Svante  Sweden
diyAudio Member
 
Svante's Avatar
 
Join Date: Feb 2004
Location: Stockholm
Two questions:

1. Is it a single driver in a single box?

2. Is it a closed box or a bass-reflex?


If there are two drivers, there is a chance that they are wired in opposite phase. That will make the sounds from the two cancel.

If it is a bass-reflex, there is a chance that the box is poorly tuned. If so, what are dimensions of the box and the vent?
__________________
Simulate loudspeakers: Basta!
Simulate the baffle step: The Edge
  Reply With Quote
Old 24th November 2007, 05:56 AM   #7
diyAudio Member
 
Join Date: Oct 2004
Send a message via AIM to rx7speed
it's a sealed box with a single driver. I'll be honest in saying I'm not sure on the dimensions of the box, but I can get them later if I can get a tape measure. I do at least have pictures though if nothing else.


BHTX I'm not too worried about the size of the box with this sub. If a larger box would help this sub out with this situation I would be game for it but my worry with that is it is already reaching the point where it will be causing a problem with this small receiver already. is there something I can do to keep the low end yet get the excusion under controll while trying to get it to play a little louder? from the sounds of it I guessing this is leading to a port reflex design which I know even less about then sealed boxes other then I haven't cared much for the sound of most of the ported subs I have heard and that they are a little louder


a little off topic though but in a nutshell how is a transmission line different then a ported unit?
  Reply With Quote
Old 24th November 2007, 07:27 AM   #8
BHTX is offline BHTX  United States
diyAudio Member
 
BHTX's Avatar
 
Join Date: Feb 2006
On top of all the above previously mentioned in regards to sensitivity, there's probably another primary cause for what you're experiencing here. However, it's really dependent on your lowpass crossover point, etc. Regardless, bottom line is.. this woofer needs a vented enclosure. With the Thiele/Small parameters you provided, EBP (efficiency bandwidth product, or FS/Qes) is about 64.3. The main problem you'll have with using a vented alignment with this driver is trying to fit a port of suitable size in the smallish enclosure that'll be required, so that air velocity within the port won't be sky high at moderately high volume levels. Anyway, after several minutes of briefly playing around in WinISD Pro, here's my suggestion: Find a way to get it in a nicely built 2.1 - 2.2 cubic foot enclosure (add port and driver volume to that though!) tuned to 20 Hz, and you'll be happy with it. Either build it yourself, or have someone build it for you. However, I'm currently trying to figure out a good size for a port or vent, as this thing really 'wants' a passive radiator. Even with the suggested C4 alignment, the port lengths required to obtain acceptable air velocity are still too long for the box it'd be in.

As it sits now, you're probably getting -3 dB at about 50 Hz. Sd wasn't provided, so I just entered 350 cm^2 as an estimate. Strangely though, with 25 watts, excursion is only around 3.5mm at 20 Hz. You'd need over 400 watts at 20Hz to reach the specified xmax of 14.1mm, and approaching 600 watts to reach xmax at 40Hz.. just to give you an idea. The voice coil probably wouldn't take much of that last example though, so it's only that.. an example. So, I'm not so sure what's going on there, as far as so much excursion with so little power.

By the way.. if there was a feasible way to use a suitable port in the recommendation above (which is essentially a -3 dB EBS alignment.. 2.2 cubic feet + woofer and port tuned to 20 Hz), an amplifier rated at around 300 watts would be about perfect. For higher tuning, etc..400+ watts should be sufficient.
  Reply With Quote
Old 24th November 2007, 07:46 AM   #9
BHTX is offline BHTX  United States
diyAudio Member
 
BHTX's Avatar
 
Join Date: Feb 2006
Oh, and I also meant to add...

Just glancing at a couple of the T/S parameters you gave, I would think this woofer COULD do pretty well in a properly designed TL. However, I can't really say much more than that in regards to transmission lines, since I haven't messed with them much myself. On the other hand, I do have a 10" Adire Brahma MKII in some kind of big crazy TL-like thingy that I purchased a few years ago from a gentleman by the name of John Nolte (www.nolteaudio.com). Yeah...it was supposed to go in my '90 300ZX TT, but that car ended up being a disaster in which I got screwed over badly and lost over $30,000 and ended up with nothing. Add to that around $5,000 in car stereo equipment that never got installed too. I sold all the rest of that equipment, but still have the 'Snailshell' enclosure with the Brahma in it sitting around here going to waste (dustcap needs to be reglued AGAIN tho...rattles a bit sometimes). Anyway, this thing produces by far some of THE loudest bass that I've ever heard from a 10" woofer. And it has a very unique quality to it too...very difficult to explain. Doesn't sound anything like a sealed enclosure, but not really sloppy either. And it goes surprizingly LOW!!! And LOUD!!! You can crank it up to a fairly high volume level, then walk over to that little 10" woofer rated at 27mm xmax, and it's usually hardly even moving. Anyway, I'd expect very similar qualities from most TL's. However, this is really the closest thing I've had good experience messiing around with...and I don't even really know exactly what it is..lol. Pretty amazing though.
  Reply With Quote
Old 24th November 2007, 07:50 AM   #10
BHTX is offline BHTX  United States
diyAudio Member
 
BHTX's Avatar
 
Join Date: Feb 2006
Oh yeah, I almost completely forgot..
I posted a short video clip of this thing a long time ago here:
http://www.realmofexcursion.com/vide...brahma10.5.wmv

  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Adcoms with lots of DC offset. Lots! ben62670 Solid State 71 16th February 2010 03:01 AM
New guy here with lots of bass related questions. looneybomber Subwoofers 45 4th October 2006 09:16 PM
DIY Motion Capture Rig? Dranore Everything Else 1 13th November 2005 08:25 AM
DIY Air Motion Transformer OliverD Multi-Way 55 10th April 2005 12:28 AM
how can sealed subwoofers produce lots of low fast bass? pkgum Subwoofers 30 11th January 2002 06:31 PM


New To Site? Need Help?

All times are GMT. The time now is 08:04 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2