This was and should've been obvious to me beforehand... Let me explain... Awhile ago, I was tryin' to figure out why my Lasonic TRC-920 didn't have as much bass as the Prosonic/Trident boxes I have. I mean, all 3 have 6.5" woofers! Then I realised that the Lasonic box was much smaller. Bigger box = bigger bass.

Fast forward to now: why is the bass of the i931 significantly weaker than the TRC-931? The fact that the back of the i931 is chopped and rounded may make you think that's the reason for the bass reduction (and that may be a small part of the problem), but upon further inspection...







the Lasonics have gone from a bass-reflex design to a somewhat sealed box configuration. Whereas the old TRC-931 used the entire box for it's enclosure, the new i931's, when closed, have a separate chamber for each woofer therefore cutting down on the amount of boom the box puts out. Look at the last 2 pics. I figured this out when I separated the front from the back of the box while playin' music with an 808 bass kick. What a difference! The "hollow bass" was gone and the boom that I enjoyed with the TRC-931 took its place! I put the 2 together and the boom was gone again.

The bottom line: I believe that if I cut away those plastic walls, the woofers can use the entire box in a bass-reflex speaker design ('cause all the vents are in the middle of the back of the box) and boom the way it should!

Now, my questions to anybody with experience in handling things of this nature... What should I use to cut the plastic walls with and how should I go about doin' this?

Use a dremel tool with a saw blade on it,and u do have a good point too.The bass is trapped in that wack ass desighn

hello,you can use a dremel!

quote:

Originally posted by jimski:
and u do have a good point too.The bass is trapped in that wack ass desighn

You're right about that! They took away one of the main reasons why people like Lasonics when they hooked it up like that! They must've thought they were improving the sound.

I'm gonna go to Home Depot and get some stuff for that. Thanks for the suggestion fellas!

make sure you practice with the dremel variable speed setting --on some similsr plastic and similar thickness -

dremels are the correct tool --but they tend to want to run loose and follow their own path if you dont have the correct speed, pressure and always use new sharp blades.

Great advice, redbenjoe! When it's time, I'll make sure to follow that advice to the letter. No point ruining a brand new box.

I was just thinking... With that simple improvement, we can have something that'll slam the hell out of a stock i931!

I wonder,
1. How much of that Seperating wall is Structural?
2. How Well does it actually Seal from front to back around the woofer's ( those plastic walls ) ?
3. Gee when i can find the time i guess I'll have to take a look at this as well.

Thanks For the Investigative Report of the inside of this

4. I noticed that Heatsink I seen, is it for the amplifier? Does it get hot? Could it be made larger to improve power dissapation/handling

MONOLITHIC,
Thank you for investigating this!It's always great to read the posts of explorers and innovators like yourself!I'm interested to know if the actual drivers (both woofers and tweeters) are identical in specifications to the ones in the traditional 931s.Also,this makes me wonder if the late nineties reissue shared what is essentially the same shell as the new i931.They both certainly have the same profile.If they are the same dimensions and shape I have to wonder if the enclosures for the woofers are new additions.A post I read from a while back claimed that late '90s version actually could put out more bass than the traditional '80s versions.I know DM4U has/had one of the late '90s versions.Perhaps he would be adventuresome enough to open it up if he still has it.I hope you decide to mod your i931.please keep us posted!

quote:

Originally posted by Jovie:
MONOLITHIC,
Thank you for investigating this!It's always great to read the posts of explorers and innovators like yourself!I'm interested to know if the actual drivers (both woofers and tweeters) are identical in specifications to the ones in the traditional 931s.Also,this makes me wonder if the late nineties reissue shared what is essentially the same shell as the new i931.They both certainly have the same profile.If they are the same dimensions and shape I have to wonder if the enclosures for the woofers are new additions.A post I read from a while back claimed that late '90s version actually could put out more bass than the traditional '80s versions.I know DM4U has/had one of the late '90s versions.Perhaps he would be adventuresome enough to open it up if he still has it.I hope you decide to mod your i931.please keep us posted!

No problem. Actually, I opened it up to change the woofers 'cause I thought the old ones might've been better at pounding out the bass. Turns out that wasn't the case at all.

The specs for the woofers are the same (15 watts, 4 ohms). I didn't read what it said on the back of the tweeters, but it's safe to assume it's about the same as the old ones.

As for the enclosures... I was wondering the same thing. Hopefully, DM4U can open his old TRC-931 reissue up. I still plan on buying one of those before the year ends.

Actually, the comment about the late 90's reissue is backwards. The original issue 931's from the late 80's have the best bass, but weak highs in comparison to the 90's model, which has better highs but noticably weaker bass. The i931 is very similar to the late 90's model in that respect.


It would be interesting to see if this tweak works. Someone should crack open a 90's 931 and see if it has the same "shell" around the woofer locations.

quote:

Originally posted by MONOLITHIC:
...but upon further inspection...

...

well, MONO that's the end of your warranty!

This just goes to show that nothing is simple in the world of acoustics.

I think they sealed the woofers in their own enclosures to "tighten up" the bass (bass doesn't leak from the back of the driver which can cancel out what's coming from the front). Less bass, but better quality.
(the sub in my car is in a sealed enclosure. I could get more bass volume if it was in a ported enclosure, but at the expense of quality & seeing as its a 600W 15" sub, I've got plenty of volume already)

Anyway these are b-boxes, not hifi, so we want more bass, right?
For what it's worth, I think you're right. A bigger enclosure with holes in the back (the whole b-box case) should get more bass, especially if it's put in a corner.
btw, if the enclosure & holes (ports) are tuned the results can be astonishing - for example the Kaboom only has 6½" woofers but the bass tuning is right on the money.

Does anyone know whether the early Lasonic 931 & the 90s reissue used similar amps & speakers? That could be the reason for the better bass from the older one.

Anyway, Get the Dremel out & we're interested to see the results...

Simply awesome Mono.Firstly having worked in the Plastic moldings industry R&D in the Mid 80's I can simply say the plastic you are about to cut out is 100% structural, even the position of the plastic through which the screws go is a structural design to add strength to the matching molds (back and front covers)Not just on this Boombox but others as well.DM4U IS RIGHT IN HIS CONCERN. Should you decide to accept this mission however... The guys are right Dremel with new blades.

Structural strength points on back cover you will find the match points on front cover for these.I venture to say this is done to cut cost as it appears both covers are the same with some mods for boards and hardware this is a less complicated molding design than that of 80's boxes.Typical of a computer generated design of 90's and today.

Have you compared both boxes using the same external speakers cabinets.
That's to wonder if both electronics can deliver the same amount of bass. Perhaps the new electronics (amp, premamp, supply) can't deliver soo much bass.

If you feel the same amount of bass using an external spekaer, you are rigth in trying to change the spekers or the cabinet.

But you could try to add some compensation at preamp level to obtain more bass or changing some cap value in the amp circuit.

Power supply strength is also important for bass reporduction ... and it's always a weak point, more in modern designs ...
You should test it running on batteries ...

EDITED:

I don't want to hurt anyone, I know several member has that modern BBX, but looking inside (thank to post pictures) it doens't look like a true BBX ... but it's a good effort.

if you don't have a pair already... make sure to pick up some safety glasses or goggles while you at it...like RBJ mentioned before the dremel has a way running off on its own...sometimes with plastic parts flying...

U do not have to cut all the way down,leave some sticking up,but for god sake let the woffers breath

quote:

Originally posted by Blaster:
if you don't have a pair already... make sure to pick up some safety glasses or goggles while you at it...like RBJ mentioned before the dremel has a way running off on its own...sometimes with plastic parts flying...

This was the somewhat rare day that I had to work on Saturday, so I took your advice and grabbed my safety glasses. You're right - those bits of plastic do fly!

Thanks.

quote:

Originally posted by jimski:
U do not have to cut all the way down,leave some sticking up,but for god sake let the woffers breath

I started workin' on it a little while ago... I took your advice and left about an inch sticking up. There's enough clearance to let the bass flow throughout the box and stop the woofers from choking themselves to death.

Thanks.

This is gonna take more time than I thought 'cause I bought a cordless dremel. The convenience of not being tied down is good and all but the charge doesn't last as long as I hoped it would. I'll say I'm about 1/4 of the way done.

U got that dremel at walmart right? Cheaper there man,anyways an inch is godd support for the back. Let the bass flow again

quote:

Originally posted by jimski:
U got that dremel at walmart right? Cheaper there man,anyways an inch is godd support for the back. Let the bass flow again

Nah, I got it at the Target on Old York Road.
http://www.target.com/gp/detail.html/sr=/qid=/ref=br_1_...0000302Y2&rh=&page=1

quote:

Originally posted by Panasonic Fan:
Actually, the comment about the late 90's reissue is backwards. The original issue 931's from the late 80's have the best bass, but weak highs in comparison to the 90's model, which has better highs but noticably weaker bass. The i931 is very similar to the late 90's model in that respect.


It would be interesting to see if this tweak works. Someone should crack open a 90's 931 and see if it has the same "shell" around the woofer locations.

It does not have the shrouding. And im pretty sure it was me who stated I like the sound of the re-issue better. It isnt because it has more bass, it's because it has a better sounding, tighter bass.

quote:

Originally posted by MONOLITHIC:

quote:

Originally posted by jimski:
U got that dremel at walmart right? Cheaper there man,anyways an inch is godd support for the back. Let the bass flow again

Nah, I got it at the Target on Old York Road.
http://www.target.com/gp/detail.html/sr=/qid=/ref=br_1_...0000302Y2&rh=&page=1

Target same as walmart..

When done take it back and say u want a refund becouse it did not work

Have you determined if there is now more bass? We are eager to hear the report.

Couldn't you leave most of the woofers backsides separated from the rest of the box by keeping most of the dividers to "cup" them?Then ( as seen in pictures #5 and #6 ) level down far enough on the top/front edge of them to let air escape into the rest of the box.Alternately If the structural points are entirely necessary you could leave them by cutting in between them.I don't know much about how acoustics work but this sounds like it might address all of the concerns listing in this thread.Of course the resulting effect on the bass doing it one of these two ways might be a bit of an experiment/surprise.

quote:

I don't know much about how acoustics work but this sounds like it might address all of the concerns listing in this thread.Of course the resulting effect on the bass doing it one of these two ways might be a bit of an experiment/surprise.

an anology to this would be like blowing up a balloon, thereorectically same air in, same air out, ie; the push an pull of the woofer inside the cabinet, displacing the same amount of air with each stroke of the woofer in & out, with the air going into the backside of the woofer-cone-area pushing against the same volume of air inside the cabinet acting like a spring and when the area of the spring of air instide the cabinet is smaller - the the travel is shorter therefore tighter bass or a higher bass frequency that the woofer is allowed to respond to at its limits. BUT if that Backspring area is enlarged ( the wall's removed without losing any structural integrity ) then the Boombox remain's in its rigidty to withstand the additional deeper bass assaulted to the cabinet and return's with a Lower frequency responce and a longer travel of the woofer cone resulting in a better and deeper bass sound arriving from this cabinet. Concern's are if that too much of the walls area of contact from the backside to the front when the 2 halves come-together are removed that the box would lose its rigidity and flex more and have a possible rattling sound because the all six side's of this box are now allowed to flex more due to the More bass emanating from this cabinet, inducing a unwanted noise to the music dersired ... something like them car's you hear as they go down the road with their bass cranked to the limits and you can hear the booming coming but dont know from which direction untill they are upon you an when they travel by you - you can hear the bass rattling the panels of their vehicle's because their panels to their cabinet are not stiff, so the unwanted noise is there that you can hear, I giggle every time I hear one of those go by I tried explaining this to them to get a better bass responce by deadening their panel's with this stuff link Hopefully that this will sound good in this lasonic i031 with this modification to the cabinet

You folks really know your stuff. This is extremely interesting to a veritable boombox novice such as myself. It's damn near adventurous busting open boxes and endeavouring to push them beyond their pre-determined limits. Keep us all updated and the discussion going

quote:

Originally posted by The Bunyip:
You folks really know your stuff. This is extremely interesting to a veritable boombox novice such as myself. It's damn near adventurous busting open boxes and endeavouring to push them beyond their pre-determined limits. Keep us all updated and the discussion going

thanks James here has; in the past designed and built many of custom subwoofer's for special needs customers specifically car stereo's as each one desired different sound and various level's of $$$ to get desired sound effect's

That baffle on the back was a vague attempt by lasonic to make the box louder,It plain blows it wasnt even air tight.Since the highs are better on this model then maybe by removing those baffle's will bring the bass back and in turn will be better than the original since that one lack highs that this model allready has.Cant wait for mono's final determinaton.

I broke almost every cutter I have and got tired and sleepy so I sealed the box up, threw on some bass heavy tunes by early Beastie Boys, Mantronix, Sir Mix-A-Lot, etc.... and hoped for the best. I won't say there's major improvement to the point that it'll compete with a TRC-931 (and I now need a stock i931 to compare it to), but I will say it throws out bass better than before if you stand about 10 feet back...

Maybe the shallow box design will only allow for but so much bass or I need to cut the plastic down about a 1/2" more to allow the woofers to breathe into the box more... Suggestions are most definitely welcome.

I'm still not finished... When I get a chance to sand down what I cut to make it look more presentable, I'll post some pics... Unless y'all don't care about the shabby (prolly good for a novice like me) job I did. If that's the case, I'll post pics A.S.A.P..

I still wonder if you could get the benefit of both a bass reflex and semi-sealed design by keeping most of the dividers.If you made them slightly more shallow this would allow air to escape into the rest of the box for more "boom".This would be a bit of a compromise.However,I wonder if this could work together to give an overall better listening experience.Just a thought.

Wish I could've tried that out. I started workin' on the box before you first brought up your suggestion. What's done is done now.

So would you say it was worth it to cut out the bass blocking baffle. I would take it down a little more..Mono where did u cop this, im gonna pick 1 up monday and do some independent test on it.Dampning material and stuff.

Yeah, I'd say it was worth it! Before, the woofers looked pretty stiff because of the sealed design. Now, they seem to throw out bass better and move a lot more like the old Lasonics. I believe that if the i931 had vents in the back that went all the way from the left to the right side like the old Lasonics, it would kick out more bass and we wouldn't even be having this discussion. But the way things are, I was thinking about cutting the baffles down about a 1/2" more. I don't think it could hurt the performance.

I got mine on 11th Street, a few doors down from the Sound of Market. It was the only one they had. It's funny, there was another store I originally went to near Broad and Walnut Street (the old former Sam Eric(?) theater is close by)... Dude was standing there and ignored me for about 5 minutes and I stepped off! They only had 1 Lasonic too. Either way, check the cheap electronics stores downtown. They all prolly have at least 1 box.

I'm gonna buy another i931 in 2-4 weeks and compare the two.

Ill check it all out.Thanks, Yo whats youre location again? Im in the "danger zone" Front st e. Lehigh ave. Maybe one day we will meet up.. Ill bust out the conion and the 777z and maybe the linolium and pledge and mess my hurtin ass knee up some more than what it is.

Used a soldering iron to melt a line where you want the plastic cut out.
Than snap it off.
Works but might not look too good, but its not seen anyways
Do it outdoors because the plastic will smoke and smell a bit.

I'm sure there's a way to get better bass.Its just a matter of figuring out how to do it.There are probably many ways.I have to wonder if its possible to retain the sealed areas but make them larger.Then you could figure out how to splice some small ports into these chambers.Of course this would change its looks somewhat.Since you've already cut some on it,that might be an interesting avenue to consider.

One way of getting better bass would be to convert the existing sealed enclosure into a tuned, bass reflex enclosure.
Trouble is you need to know some specific parameters of the woofer (as explained here: subwoofers.org )& the volume of the sealed encolsures in the new Lasonic.

I'll bet the results wouls be good though.
It's the reason some 90s Panasonics (RX-DTs, cobra-tops, etc.) have such good bass from their 4" woofers.


*TPR* :link repaired

*TPR* :link repaired

...thanks Jens!

quote:

Originally posted by MONOLITHIC:
Yeah, I'd say it was worth it! Before, the woofers looked pretty stiff because of the sealed design. Now, they seem to throw out bass better and move a lot more like the old Lasonics. I believe that if the i931 had vents in the back that went all the way from the left to the right side like the old Lasonics, it would kick out more bass and we wouldn't even be having this discussion. But the way things are, I was thinking about cutting the baffles down about a 1/2" more. I don't think it could hurt the performance.

I got mine on 11th Street, a few doors down from the Sound of Market. It was the only one they had. It's funny, there was another store I originally went to near Broad and Walnut Street (the old former Sam Eric(?) theater is close by)... Dude was standing there and ignored me for about 5 minutes and I stepped off! They only had 1 Lasonic too. Either way, check the cheap electronics stores downtown. They all prolly have at least 1 box.

I'm gonna buy another i931 in 2-4 weeks and compare the two.

and did you ever get this "Second Lasonic i931" ?
and do like you said above?

Nah, I didn't get one - I've been jammed up with paying bills and buying other boxes!

But now that you bring it up, I'll buy one next Friday - mainly because I told my nephew a month ago I'd buy him one to compliment his iPod Nano.

Great thread Mono!!!