CurtPalme.com Home Theater Forum

Sparky015

Hey guys,
I was getting ready to do a parts order for my pj, so I thought I would investigate my front speakers as to why my bass is lacking. Here is a bit of background info before I dive in to my question:

These speakers are known for their response and base characteristics. I thought it was my crappy Sony AV receiver I had been using until I connected them to a known good Pioneer stereo amp and same problem. So, I decided to open them up to see if connections were correct. I popped out both xovers and I see some bulging caps. I have not measured them yet, but I'm pretty sure it's a safe bet they are leaking, which is why my bass response is lacking. So to my question, have you heard of this company Elytone? It seems they manufacture xovers for speaker companies. My guess the caps are junk caps, but wanted to ask the question, since I'm not an audio guru. Pic below for your perusal! Laughing

The 88uF cap is the one bulging. Hard to tell from this picture.

Sparky015 · Posted: Sun May 02, 2010 6:53 pm Post subject:

I've been searching all day for audio grade electrolytics to recap this crossover curcuit. Apparently people don't do this, because finding the right values is turning into a much bigger exercise than I had expected. PITA. Pretty soon I'm going to call it and just live with it until it's time to get new speakers. This is insane.

**Curt Palme** · Posted: Sun May 02, 2010 6:59 pm Post subject:

I disagree. Check the foam surrounds on the woofers, if they are foam and not paper, I'll bet that they have deteriorated. you're looking about $50 per speaker to replace just the foams. Any competent speaker repair shop will be able to do that, it ain't a speaker repair shop if they say to replace the drivers!

Sparky015 · Posted: Sun May 02, 2010 7:21 pm Post subject:

I thought that too Curt, but these are not old speakers. These are less than 10 years old. I bought them about a year before Infinity discontinued the Studio Monitor series. Here is a pic of the woofer. No deterioration. That's why I focused on the cross over circuit.

The only thing I didn't do was hook up a generator and pump known frequencies to it and take a scope at the leads to the woofer to see if the signal is reaching it. I guess that would be telling if it is indeed leaky caps on the cross over.

**Curt Palme** · Posted: Sun May 02, 2010 7:29 pm Post subject:

OK, good, the caps are cheaper. try eBay. Usually though, the signal passes clean to the woofer, and the crossover is only used for the mids and tweets. Draw it out, maybe there are caps in the woofer stage.

Sparky015 · Posted: Sun May 02, 2010 7:46 pm Post subject:

There is, although I am not sure why. Like you said, if you filter the highs and mids, anything left should be lows. There is an inductor in line with the positive terminal, and then a 120uF cap across the terminals. I found a schematic online, although unfortunately, it's not clear enough to see all of the values. If that 120uF cap is leaky, I could be losing Dbs.

**Curt Palme** · Posted: Sun May 02, 2010 9:57 pm Post subject:

True, but that should also put the amp into protect mode.

The cap/coil attenuates the high end, that's all. Cut the cap out of the circuit, or bypass the coil and see if your bass increases.

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

Caps are used to allow high frequency pass and block lower frequencies while inductors are used to allow low frequency pass and block higher frequencies. The levels of control are based on the values.

ecrabb · Posted: Mon May 03, 2010 12:36 am Post subject:

Mac's right - the caps are high-pass filters for the midrange and tweeter, while the inductor is a low-pass filter for the woofer... I can't see how there could be anything wrong with the crossover that would cause weak bass response. If the surrounds and cabinets are in good shape, then I can only think of two possible explanations for weak bass:

1) Poor room treatment and response (nulls). Have you moved the speakers around? Changed listening positions? For kicks, try putting one in a corner temporarily just to see what happens to the bass.

2) Unrealistic expectations compared to subs. Do you have another room with a sub? Been hanging out a friend's house with a sub? From all the user reviews I found on this model loudspeaker, the one con that keeps coming up is weak LF response. The one response spec I read said 32hz, but that's probably the -3db point, so at reasonable listening levels, it's much less than that. The bass is probably similar to my old M&K subs, but with the disadvantage of totally inflexible room positioning.

Just my .02.

SC

JustGreg · Joined: 07 Mar 2006 Posts: 3098 Location: Kenosha, WI

One of my subs is a JBL PSW-DPS112 (hey...I have a beer budget!) and known for failed C6 caps (4.7uf 100v). So prevalent that JBL even offered a repair kit (but no recall!...the bastages!) The kits contains 2 caps, and 2 resistors.
The values recommended in the Audio community call for more robust caps and an increase in resistor values.

I repaired it when it blew but only replaced C6 with the same value. I lost ALOT off bass response for reasons unknown to this non-tech brain. What was left was muffled and at high volumes a scary annoying BRRRAAAPPPP sound occured during explosions, etc. Since replacing all the components recommended it sounds pretty darn good....for a JBL. Rolling Eyes

I'd replace all the caps and resistors. You might want to think about increasing the value of the bloated one by a couple clicks. General Purpose components don't cost much.

Sparky015 · Posted: Mon May 03, 2010 12:36 pm Post subject:

Thanks guys. I have to admit, the bass has been lacking since I bought them, which ties in to SC's research. I do have a matching powered Infinity Sub, but here is the thing. I knew this guy in college that had the SM255s, which steps up to two mid-range woofers and a 15" woofer in place of the 12" that's in mine. His speakers were literally as loud LF wise as my powered sub. They were just that impressive. We even did an experiment and hooked in my powered sub to see if it would make a difference, and his 255s were so loud, you couldn't even here the sub. This may tie in to SC's point #2 of unrealistic expectations, but I would expect better LF response than what I'm getting today, which is pretty much nothing given the performance of the speaker's big brother. A slightly bigger woofer and an added mid-range can't be that much better.

Given the fact that the caps are deformed, I ordered some better quality audio caps and I'll recap the cross over. For $5 in caps, I'm willing to go through the exercise to see if I can't make an improvement with just better components. I'm also investigating if there are better inductors, but I want to do one change at a time.

Like SC said, I could have unrealistic expectations, but the fact that the 255s are so good, I can't help but think there is some performance to be had out of these things. We'll see. If anything else, it'll be a learning experience. Since these are used primarily in my theatre, and I have the sub, it's not a big deal, especially with the long term plans to replace them for something with a smaller footprint, but it's a hobby Razz

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

Sparky. Just hook up one of the speakers woofer directly (bypassing the crossover) and turn down the treble on the amp, and see how the bass is. You wont ever get more bass than this no matter what inductor you use. This would solve the expectation part.

Sparky015 · Posted: Mon May 03, 2010 12:57 pm Post subject:

That's a good idea, Mac. I'll give that a shot this evening. That's easy enough to do without being evasive. I'll report back if there is performance to be had, or if I'm trying to get Corvette performance out of a Malibu! Laughing

Sparky015 · Posted: Mon May 03, 2010 4:35 pm Post subject:

Bored over lunch, I did some calculations wiht the values in the crossover. At an 8 ohm input, they match the specs on the tech manual I listed above. The low frequency is ~427 hz. Drops by about half at 4 ohms. It seems that should be a 15mH inductor on the LE to get the most bass response. Not sure if they did this so really low-end noise/hum isn't broadcast. Anyway, Mac's test of the woofer should confirm that as well. I just need to find a SM-255 tech manual to see what's in that cross-over. Like SC said, I could be trying squeeze water out of a turnip, but, hey, it's fun!