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StevieQ

how to get rid of muddy bass on La Scala

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I recently picked up a decent pair of 1980s/1990s vintage La Scala on Craigslist.  One tweeter was blown and requires a diaphragm/coil replacement (no biggie), and the 3/4" plywood finish is very ugly, but the pair of speakers is otherwise in very good shape.  It comes with AA crossovers.  Everything about the speakers is nice - except for the sound coming out of the 15" woofers.  It has good treble and very strong and rich mid range, but the sub-400 Hz frequencies coming out of the 15" woofers are just exceedingly muddy and boomy.  The muddy echos are highly irritating.  The muddiness must be because of cabinet resonance on the 3/4" plywood.  What can I do to eliminate the resonance?  I am thinking of applying 12"x12" marble or granite tiles to the interior and exterior surfaces of the woofer box to stiffen the walls to eliminate resonance, but the tiles would add a whole lot of weight.  Are there other solutions I can try?

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Sounds like it could be blown? Mine sounds nothing like what you described. Maybe someone with more experience can chime in.

Sent from my LG-LS997 using Tapatalk

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IMO, If you have muddy bass from a LaScala, there is some problem other than cabinet resonance. Otherwise, brand new, people would have complained of muddy bass, and they didn't. Unless the cabinets are somehow falling apart.

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Welcome.

 

When I rescued a pair of La Scalas of a similar vintage from 30+ years of service in a bar in Ohio, they too had resonance issues.  Refreshed AA networks, new Crites woofers and a cosmetic update and they were ready to serve in a high school band practice room.  Or so we thought.

 

At first, the band director was thrilled. They sounded great to him and to me.  After a few weeks, he called with concerns about anomalies during certain recordings.  My immediate reaction was bad recordings; garbage in, garbage out.

 

Soon I became a believer in the La Scala sidewall resonance issue.  The quick and dirty "fix" was to wedge pieces of 3/4" dowels in the spaces between the doghouse and sidewalls vertically centered in horn mouth.  Although far from an ideal long-term solution, the improvement was immediately apparent.

 

The band director was happy, but I was not satisfied.  During the next summer break, I collected the speakers and put in the more substantial and permanent braces visible in the photo where the speakers are taped in preparation for a coat of Duratex.  The Duratex and Speakon connectors are this summer's tuneup.  The bass reflex mod, apparent in the photo showing the Speakon, was done when the horn mouth/sidewall braces were installed a few summers ago.

 

The photo of my son removing one before this summer's servicing, illustrates their daily use in the band practice room.  They were originally powered by an h/k 730 receiver.  Eventually, that vintage piece needed service.  My tech lent the band an Onkyo integrated amp (~80 watts/channel).  Long story longer, the band director chose to keep the Onkyo; the now refreshed h/k 730 is now powering a pair of Klipsch KLF-20s for a friend of mine.  All of this would have been impossible without the assistance of the good people on this forum.  At least  a dozen Klipsch forum members were instrumental-- pun intended -- in every aspect of this saga.

 

This experience has made me a believer in the need to brace the bass horns of vintage La Scalas.  I am also a strong proponent of the bass bin mod.  It is easy to do, easily reversible, and provides a noticeable improvement in the bass, without sacrificing the tight La Scala bass that makes percussion sound great.  The small trade-off is slightly less efficiency.  To put that in perspective, the modified La Scalas are still capable of summoning the police -- without Sting -- when powered by a TDA7297 chip amp -- visible in the last photo -- capable of 5 watts/channel if fed more than 12 volts.  That white tube holds 12 AA batteries powering the TDA7297.

 

Feel free to send a PM if you want more details.

 

 

 

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The bass of a LaScala should in no way be muddy. Something is wrong. Nothing wrong with bracing cabinet but from your description you have a problem with the speaker or crossover. A LaScala does not go down into the wall shaking bass stage below 50hz but the bass it makes is outstanding. Some detective work is called for. 

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Have you opened the doghouse and physically checked the woofer? At least make sure everything is tight and clean the connections.

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37 minutes ago, dtr20 said:

Have you opened the doghouse and physically checked the woofer? At least make sure everything is tight and clean the connections.

 

I agree.  The woofers are typically only attached with four screws.  I used eight.  What is "not worth a dime's worth of difference" at the production stage is worth the time, effort and expense to the DIYer.

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The doghouse has a leak somewhere. A leaky horn is no longer a horn. The bin mods suggested are good advice, but first I'd check the doghouse and driver gasket for leaks. A diluted solution of dish detergent and water sparingly applied to the joints can show leaks. The construction of a LaScala or any other W-style horn makes this tricky. I would replace the gaskets on the drivers immediately, since they don't improve with age and Klipsch boxes are noted for their construction integrity. 

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The seal on woofer door is bad or seal on woofer is bad I bet. I would also loosen and re-tighten all the connections on the crossover and update the caps. Also check the terminal connection going into the dog house. I replaced mine with better ones. Could be wrong woofer in them also easy to check.post-7905-1381971186562_thumb.jpgpost-7905-13819764513688_thumb.jpgpost-7905-13819795236662_thumb.jpg

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16 hours ago, STEVIEQ said:

"I recently picked up a decent pair of 1980s/1990s vintage La Scala on Craigslist.  One tweeter was blown and requires a diaphragm/coil replacement (no biggie), and the 3/4" plywood finish is very ugly, but the pair of speakers is otherwise in very good shape.  It comes with AA crossovers.  Everything about the speakers is nice - except for the sound coming out of the 15" woofers.  It has good treble and very strong and rich mid range, but the sub-400 Hz frequencies coming out of the 15" woofers are just exceedingly muddy and boomy.  The muddy echos are highly irritating.  The muddiness must be because of cabinet resonance on the 3/4" plywood.  What can I do to eliminate the resonance?  I am thinking of applying 12"x12" marble or granite tiles to the interior and exterior surfaces of the woofer box to stiffen the walls to eliminate resonance, but the tiles would add a whole lot of weight.  Are there other solutions I can try?"

_________________________________________________________________________________________________________________________

 

Now, I am saying: FIRST THINGS FIRST!  The cabinet resonances have nothing (or little!) to do with "muddiness" in the bass bin.  The bass bin side panel stiffness issue is primarily associated with the MOUTH end of the bass bin's side panels (meaning they need stiffening MORE from the center of each panel FORWARD, simply because the rear cabinet joinery GENERALLY suffices for the center-rearward stiffness of the side panels!) The stiffness issue PRIMARILY affects the MEASURED response curve of the bass bin...and you MAY HEAR the difference (especially at higher volumes!) ...but...  "Muddiness" is more than likely a separate issue, or a COMBINATION of separate issues, which are easily addressed, as follows: 

 

If the LaScala bass bin woofers are K33 models and are actually functioning OK, but just "sound muddy", or MUFFLED...then it is HIGHLY LIKELY primarily a "filth accumulation" issue.

 

CLEAN OUT THE BASS BIN!  Your speakers are OLD, and there is NOTHING to keep the accrual of "DUST BUNNIES" and other stuff (such as mouse or rat nests, to include dead mice or rats!) from cluttering up the horn-pathway from the face of the woofer cone all the way through the compression slot on rear of the doghouse and into the first flares (to the left and right past the "splitter" on the speaker rear panel just to the rear of the compression slot!) of the "bifurcated bass horn lens.

 

SOOOOOOO.....Flip the speakers upside-down. Take a permanent marker and draw an arrow towards the front on the bottom panel, which is removable...and label it with the serial number of the speaker.  Do this for both bottom panels PRIOR TO removing them.  This will make re-attachment of that bottom panel (woofer door cover!) go MUCH EASIER when you get ready to put them back on the bottom of the speakers...trust me on this!

 

Remove the bottom panels (woofer door covers!) using a HAND screwdriver (and when replacing them use a HAND SCREWDRIVER, while applying PRESSURE to the panel...that way you won't "Strip-out" the threads the original screws made into the wood of the speaker bottom!)...they are screwed onto the bottom panel of the speaker's actual bass bin bottom, itself!  Because of the age of your LaScalas, you may have to pry the door panels off once ALL the screws are removed because the "gasket" material will probably have them stiuck on through deterioration of that gasket material.  If you need to replace the gasket prior to reassembly then be sure to scrape off  all of the old gasket prior to installing new gasket material!

 

Once you have removed them both of the panels, unhook the connecting wires to the woofer.  If the wires are soldered to the woofer tab, don't break the solder to do this. There will be UNSOLDERED connectors to make this happen for you where the woofer wires connect to a terminal at the top of the inside of the doghouse assembly.

 

Now remove the woofers, themselves.  Be sure that they are ACTUALLY K33 woofers!  Your speakers are used and they may NOT have K33 woofers in them anymore!  I bought a used pair once which had Peavey Black Widows in them...which are worth more than the K33 woofers but do NOT perform as well in the LaScala Bass Bin!  Your woofer cones may be damaged or (BEST CASE SENARIO) the front of the woofer cones will HIGHLY LIKELY be covered in years of built-up filth and crud.  Use a gently SOFT paint brush to gently remove al the crud and such from the front of the woofer cones.  You can also used compressed air AT LOW PRESSURES!

 

Now...take the speakers OUTSIDE or somewhere else so that you can take some compressed air and shooting it through the compression slot in the doghouse, blow out all the trash, dust bunnies, dead mice, mouse houses, etc.  TRUST ME...you don't want to be doing this INSIDE THE HOUSE!

 

ALSO, use that soft paint brush to "whisk" out any accumulations in the left and right initial bass horn flares...you can do this by reaching your hand holding that SMALL brush through the compression slot inside the doghouse assembly...and finish it up by facing the front of the doghouse assembly and reaching around to the back of it on each side of the doghouse, up into the mouth of that initial horn flare behind each side of the doghouse,   Once you get all the crud loosened up, then blow more compressed air through the compression slot to each side.

 

If the woofers are actually K33 models, and are in good condition AFTER cleaning them...put everything back together...and enjoy them...the "muddiness" you described should be HISTORY!...at least down to around 45 hz or so...the lower limit ( it rolls off severely around 45 hz!) of the LaScala bass horn lens, itself!   If the woofers are NOT K33 models, then replace them WITH K33 models!  THEN put everything back together!

 

If the woofers are functioning ok, then the CLUTTER is the MAIN issue...BUT....whiie you are into everything, disconnect all the screw-down connections, clean them off (to include the screws!) Birchwood-Casey"Gunscrubber" (solvent-grade ether under pressure) works well...just squirt a bit on a Q-tip and watch it clean the "connection crud" right off!  Once the connections are cleaned and shiny (it may take more than the gunscrubber to make the "shiny" thing happen, so use one of those scotch-brite green pads for that part),  take a q-tip with a tiny dab of dielectric grease on it and LIGHTLY apply the dielectric grease to the CLEAN connections and screws and re-attach the connections, then wipe off any excess dielectric grease which squeezed out.  It is easiest to actually remove one pair of connections at a time while doing this and saves time trying to "figure out what goes where" when re-connecting everything back up.

 

DIELECTRIC GREASE IS YOUR FRIEND!  You can find it at any automotive parts store!  One small tube will last for years on various applications...to include your car battery terminal connections (do that twice a year, once in the late fall and once in the late spring!)....you will be surprised how much longer your battery will last (providing it doesn't run down for other reasons than bad terminal connections!)...and it saves your alternator diodes from going out pre-maturely!  Most alternators nowadays have to be replaced because the "sealed-inside" diodes have gone out way before the rest of the alternator is actually worn out!.

 

You can thank me later!  Dalwhinnie 15 year-old single malt makes a great "thank you"!

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I will tackle the woofer chamber clean out project next week to see what it can do and also to examine the identify of the 15" woofers to see if they are original.  

 

For what it's worth, when I knocked on the lower exterior side walls with my knuckles, the tone of the echo matches the muddy hollow resonant sounds I referred to earlier. This is why I believe it's a resonance issue, not that other issues may not also be present, such as debris buildup.  Also when I played bassy music, it's the lower exterior side walls and the lower back wall that have the most vibrations.  This again points to resonance problem.  I will also try the internal bracing method DizRotuz showed in the pictures.

 

I am very new to Klipsch speakers.  I recently bought a pair of RP280F for my home theater, and a pair of RF-7 II for my living room.  I really like my RF-7 II after correcting some deficiencies with a 31-band equalizer.

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I just restored an old pair of 1979 lascalas............did the complete disassembly and clean out of the cabinets, midhorns, drivers, and recapped the AAs.  I don't have ANYTHING like you are describing.  I am using tube pre and amps.  The bass is tight and clean..........but does drop off as expected with a lascala.

 

What are you driving them with?

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