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KSP-400 Hum Fix/Possible Non-Powered Tower conversion?


EdmundGTP

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To be honest, I haven't made much of an effort to get in touch with anyone from Klipsch with regards to what I've been working on here. I did contact tech. support about a year ago when my one amp first started going on the fritz. The gist of the conversation I had was pretty much what we all know now; that Klipsch no longer stocks replacement parts for these, and that they contract out their repair work on them to a couple different electronics repair companies. So I did as they suggested and sent it in for repair.

Back then, I mentioned the idea of using a different, or external amp, and they (can't specifically recall who I spoke with, maybe Stephen?) didn't seem terribly keen on having an inclination as to whether or not it would work, nor did they have any immediate knowledge of anyone else who did so. So I dunno. That sort-of lukewarm response on the idea discouraged me from digging much deeper in that direction. At the same time I can understand their position, in that once a serious change is made to the speaker (i.e. amp replacement etc.) then it really becomes a product that they can no longer "guarantee" optimum performance on, or really stand behind in the service/warranty sense.

But if you, or anyone else for that matter, happens to know of anyone at Kilpsch or somehere else who is "in the know" on these speakers, I'd be more than willing to share/seek any info as I try out this amp swap deal. Comparatively speaking, it is a fairly small group of us here who have these speakers, and I really do love them, just as I'm sure the others do. What it boils down to is, I want to find a way to make them work well, and reliably, for as long as humanly possible, and unfortuantely the original amps dont seem to be conducive to such.

Now with that being said, I know that I personally don't have the extensive knowledge of amplifiers, components, and measuring to really even be taking this project on, but present circumstances put me in a good position to do it. So I'll probably have a few questions for our more knowledgable members along the way. The thing I'm trying to figure out now, is which of the amplifiers that I listed above would be best for this project. I've looked over the manuals and specs for all of them and they all seem fairly comparable. The Crown XTi being the most expensive, but also having a lot of bells and whistles that seem unnecessary for this project. So if anyone reading has some input there, I'd be happy to hear it.

Also nice to see this thread finally gaining a little steam. Stay tuned for updates. [<:o)]

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Just found another contender.

Crown XLS202D

If you end up going this route, you'll want to change out the fan for a quieter one. The stock fans are too loud to have in the same room as your speakers. I had 4 of the XLS402D's powering my HT, and changed the fans on all of them. It makes a big difference. I might even still have a quiet replcement fan laying around somewhere if you end up getting one of the 202's. The fans should be the same on both amps.

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Ahh thanks for the heads-up on that. Is the fan like a typical 80mm computer case fan, like this?

papst_silent_case_fan.jpg

Or something fancier?? The fan in my roomate's Xbox 360 is annoyingly loud as well, and I've been putting up with that for a while now.

Oh and aside from the fan noise, how did they perform in general?

Also just looked at the Behringer EP 1500. Seems fairly comparable

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Yes, they're similar. Here's the back of one of the amps that got their fans swapped. You need 2 per amp (click on the pic to see a larger view). I also cut the fan guards off to quiet them even further. The EP-1500 uses a 24v fan like the QSC's. They need to be swapped also as they are quite loud as well. I didn't swap my EP-2500 fans, but did mount it in another room than where my sub is. The Crowns are a good amp for full range speakers but a great amp for subs. They were slightly harsh on the top end when pushed really hard with normal speakers. You don't have to worry about that for the frequencies that the subs will be reproducing.

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In addition, if you use a pro-style amp, you'll need some sort of high pass filter to protect your subs from overexcursion if they get a signal below the tuning frequency of the subwoofer/box assembly. Most sub amps have that built into them already whereas pro-amps don't.

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I didn't know if it was sealed or ported, but I'd hate to take a chance. An amp with enough power can push a driver past it's mechanical limit even in a sealed configuration, under the right conditions. Sealed should be less prone to overexcursion than ported but they're not over excursion proof.

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Thanks for the detailed response on amp removal. As of this moment I don't need to remove it- yet. The 3 into 2 fixed the hum on the non-repaired ampliier. But then, lo and behold, I hear the hum again a few hours later. You guessed it-the "fixed" amp is now humming. Throw in the prong adapter + cross my fingers... voila- no hum. But probably a bad omen to come. We'll see. FYI, the first amp failed and the hum(s) began while plugged into a decent old school Monster hts-3500 power conditioner so I don't think curent fluctuations are the cause. Keep posting the fix.

So, I'll think I'll give the 400's a little rest, and listen to the Cornwalls in 2 channel. FYI, I am still exploring the Cornwalls and dialing them in , they are great speakers, but in a HT set-up I think the 400's/S6 are still the way to go. So it's probably worth the work you are putting in.

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I had heard at some point that the typical reason for failure in these amps is due to aging circuit board component, but I dunno how certain that is. I got on parts express and ordered all the adapters and plugs and cables I think I'll need. Just need to order an amp now. Once the binding posts I ordered arrive, I can finish drawing up the replacement plate which will fit where the amplifier was.

Also been drawing the rest of the speaker up in 3D CAD while researching parts and stuff. Should have some more cool renderings as I finish drawing more parts.

 

 

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Edmund,

Fantastic drawings, dude! Only problem I see is that the perspective (on the side/front view) is a little off (vanishing point is in front of speaker, not behind). Love the wood grain, too.

Thanks for the positive feedback! Yeah I noticed on that one I had the assembly situated at a weird angle so the perspective looked off a bit. Being that theyre 3D models in an assembly I can orbit around the speaker to view it at any angle, add/delete parts, do cross sections. The wood grain is actually a programmed in surface texture for mahogany. I need to make an assembly for the left one, then I can add those to the assemblyI have done of my entire house.

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Edmund, great work! I am currently looking to do exactly what you are talking about. I just purchased two ksp-400 in excellent condition for $400. Currently both amp's work, however the right speaker's sub has a slight hum when powered on, with or without any input. The non-grounding plug makes no difference. This was the reason the previous owner was selling them so cheap. The right sub still works but sounds slightly weak or muffled. The hum can only be heard at low volumes and does not change with volume, gain, phase or boost control. I assume it is the amp, but I am very reluctant to have it repaired after reading the multiple threads on amp problems.

The amp that has been suggested to me was the QSC GX3. http://www.qscaudio.com/products/amps/gx/gx.htm The power output seems to be ample and a bonus is the input options. It is the only rack mount amp I have found that has standard rca inputs along with the xlr and and trs inputs. The price seems very reasonable at around $300. I would love feedback from anyone who has any experience with QSC amps. I am also looking at using the Reckhorn B1 to manage the tuning.

The other option I am looking at is continuing to not use the sub on the right side. I am not convinced I need it. My set-up is a surround sound in a 15x18 living room. The components are listed in my signature line. I think that both subs with that much power may be overkill. Would it improve sound quality significantly?

BTW if you end up making those amp delete plates for the back of the speakers would you be interested in making a spare pair?

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That QSC amp looks like a solid option. I went ahead and ordered a Crown XLS202 last week for $230 and it should arrive here today.

The way my room is set up, I could notice immediately when the one sub stopped working. With only one sub running I get a very noticable lull in the bass output at my listening position, so running only one of them wasn't really an option for me.

The other thing to consider with subs is that from what I've seen, there pretty much is no such thing as overkill. Just because you're running a higher wattage amplifier to the subs, that doesn't necessarily mean they're going to play louder than they did previously, since the amp isn't sending all 300, or 400 or whatever peak wattage at all times. Furthermore, regardless of how much power you apply to your subs, you'll still want to match the output level of them to the rest of your system so that for a given volume level there isn't an excessive amount of bass. So running both of them with slightly higher wattage wont really be "overkill". All that the extra wattage does, is give you the ability to turn the volume up a bit higher before the subs will start to distort. Unless there's some sort of magical subwoofer EQ circuitry in the original KSP amplifiers, your sound quality after the fact should be the same as before.

My main objective in a standalone amp was to find one with about the same or slightly higher power output at a reasonable price. I'm going to try running the new amp without the Reckhorn at first to see if it will even be necessary. Another option I've come across for sub EQ-ing is using the Behringer Feedback Destroyer. There's a really detailed article over at hometheatershack.com which explains how to EQ your subs using it. It sells for about 90 bucks and looks to have MUCH more flexibility, although with that comes more complexity, than the Reckhorn unit.

I sent my drawings for the amp delete plates to a local water-jet cutter (the same one who cut the custom feet which I'm using on the KSP's) and haven't heard back on a price for them yet. I'll be sure to post when I do.

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