[kgb_m3]

Merry Christmas everyone!

This morning I ripped apart the Logitech sub/amp. Snapped some pics:

Full amp and power supply view

4 chip amps they used (not sure what specific ones yet)

Transformer (not sure which exact one yet)

Power supply capacitors veiw

Overall the amp isn't impressive, have no idea how THX even certified this rubbish.

So here's my dilemma, do I rip the amp off the back plate/heatsink and build my own to fit where the above posted amp sits or do I build a whole new enclosure. Another thing is it even worth messing with the Logitech sub and box? Or do I just build 2 channel amp for my Polks and buy a separate powered Polk 10" sub to run off its own amp? Sell Logitech all together for whatever I can get for it, $80 or so I would imagine, use that to get the Polk sub.

I am curious to rip it apart to see what chip amps they used, I have a feeling they're LM1875s and possibly something stronger for the sub.

Ideas? Suggestions? At this point I need to really think this through and see what's the best possible route.

 

[LUCIDD]

Hmm... No idea!... depends on personal reasons -personality perhaps? -

If it were up to me:
On one hand, I really don't like wasting stuff... and let something -product sit around and collect dust. I'd rather sell it at a loss -cheap for someone else [or their son/daughter] to enjoy. This way, someone that cannot afford $200 for the Logi-Z2300 [a really good system by many standards]... can get great bang for their buck!
On the other hand, I really like to customizing/maximize a system - beefing it up [like "Tim the Toolman Taylor"] - and having fun at it: and if successful - Be Proud Of It! + it can be a learning experience.

But if you already think the Z2300's internals are rubbish, that means that you outgrew them and they may never suffice your growing audiophile needs.

Up to you! Have fun!

_________L

 

[Operandi]

I would just sell the Logitech's. Really the only thing you would want to salvage would be the Tang Band sub but you could easily buy the same driver retail. As you are finding out Logitech's amps are built on the cheap and arent ently really anything special.

 

[kgb_m3]

^^ Sold Logitech for $80 today. So I kept the Polks bookshelf for now and while waiting on the custom amp parts I need to figure out one last thing.

What do you guys think I should do about the sub? I have a JL w3v2 car sub/box laying around, that maybe overkill for a 2.1 pc system. I can buy the 10" powered Polk but rather not. I also have a ported Onkyo 8" powered sub. Any ideas?

 

[Swingtops]

kinda have the same problem with my setup - I am trying to use a 12" Kicker car sub in a custom fiberglass ported enclosure with a JBL home theater sub amp ~150W. It's loud but it lacks any punch at all, the car subs are usually 4 ohm and HT stuff is usually 8 ohm. I think this may be causing some of my problems. I would try looking around for just a woofer that matches the impedence of your amp and possibly build your own enclosure/box. I will be interested to see what you come up with!

 

[Operandi]

Quote:

Originally Posted by kgb_m3 /img/forum/go_quote.gif What do you guys think I should do about the sub? I have a JL w3v2 car sub/box laying around, that maybe overkill for a 2.1 pc system. I can buy the 10" powered Polk but rather not. I also have a ported Onkyo 8" powered sub. Any ideas?

First you won't be able to use the JL without knowing it's T/S parameters. It's probably a good sub but box tunning for a car is very different from box tunning for home audio.

You could use the Onkyo but it probably isn't any better than the Logitech, probably tuned lower though.

That leaves either buying or building. Having heard lots of commercial speakers (and seeing the price tag) and a couple of DIY designs I'm all for building (as you've probably figured out by now). Dayton sells pre-fabbed sub cabinets now so that makes it incredibly easy, the Parts Express site seems to be down at the moment so I'll try to get a link tomorrow.

Quote:

Originally Posted by Swingtops /img/forum/go_quote.gif kinda have the same problem with my setup - I am trying to use a 12" Kicker car sub in a custom fiberglass ported enclosure with a JBL home theater sub amp ~150W. It's loud but it lacks any punch at all, the car subs are usually 4 ohm and HT stuff is usually 8 ohm. I think this may be causing some of my problems. I would try looking around for just a woofer that matches the impedence of your amp and possibly build your own enclosure/box. I will be interested to see what you come up with!

Like I mentioned above if it's tunned for a car it's not going to sound right at all for a room. But almost all home subs are 4ohm also to get more power out of the amps, woofers are usually 8ohm though to be amp friendly.

The lower a driver dips in it's impedance the harder it is on the amp which causes it's distortion to rise (at best) or worse run out of current and clip. Distortion is less audible in the frequencies subs deal with so it's not really a big deal.

 

[LUCIDD]

Quote:

Originally Posted by kgb_m3 /img/forum/go_quote.gif ^^ Sold Logitech for $80 today. So I kept the Polks bookshelf for now and while waiting on the custom amp parts I need to figure out one last thing. What do you guys think I should do about the sub? I have a JL w3v2 car sub/box laying around, that maybe overkill for a 2.1 pc system. I can buy the 10" powered Polk but rather not. I also have a ported Onkyo 8" powered sub. Any ideas?

hehe... sell the sub on craigslist

Or customize the JL sub for home use.
Although it may be a little overkill - it can be tuned to work.
Personally, I do like the JL line of car subs - but with a car sub, depending on the type of amp it has [how adjustable] it can sound great for home use.

And because car sub -box can be quite narrow - it can be hidden behind couch or something. I have a 10" Kicker-Comp-VR sub with a Rockford Fosgate 200m [200watt rms] amp -that was a little too boomy for my car [2007 Infiniiti G35s with an OK - not great Bose system] so I closed the PORT on the sub box - and it sounds perfect now. It's all in the tuning - Gain,lowpass etc.

I'd try to work with the sub you have first - If you don't like the sound, I'd close the sub-box's port --- this will decrease the volume, and boomyness - yeilding a tighter boom. Then tune it to your liking. Even though it is a large -12" sub, it can be tuned. --- even may work, since the 12" JL's response may not be that great in the upper -mid-bass sounds - you can set the crossover to about 65hz [since your polks go to 63hz]... then voila!-

If no good, sell the JL on craigslist... then put that money towards a new home-sub.

__________L

 

[LUCIDD]

Quote:

Originally Posted by Swingtops /img/forum/go_quote.gif kinda have the same problem with my setup - I am trying to use a 12" Kicker car sub in a custom fiberglass ported enclosure with a JBL home theater sub amp ~150W. It's loud but it lacks any punch at all, the car subs are usually 4 ohm and HT stuff is usually 8 ohm. I think this may be causing some of my problems. I would try looking around for just a woofer that matches the impedence of your amp and possibly build your own enclosure/box. I will be interested to see what you come up with!

Operandi is right.

But another solution - a cheap one too, is to buy an ac-to-dc adapter. You can find one on ebay for less than $20 shipped. - I included a pic.

This will work if you have the car amp - so power the car amp with the adapter-transformer. Swingtops, this will not work for you unless you have a car amp.

But with regards to your 12" kicker sub not having "Punch" - it may be that your custom box's port is too large. Again, try plugging it up... and you'll automatically get less boomy - and yeild a punchier tighter bass response - which will only make it better.

Like I mentioned earlier, I had the same issue in my car. The bass was LOUD - really loud, but my 10" Kicker Comp Vr Sub was designed for a closed design box. Mine was ported - and the Bass was slopppyyyyy... so I plugged it up and then adjusted a few settings- tuned it, and then it was perfect.

If your impedance is mismatched [in this case your amp is 8ohms - it can go lower to 6ohms without too much issue - but going to 4ohms is not so good], then you do sacrifice quality... and also, your JBL amp will eventually overheat and fail -if not worse. - what you can do is match impedance by adding another sub [identical sub if possible] -wired in series - which will increase it to 8ohms... then done.

 

[Swingtops]

interesting thoughts, I used a port from a 10" sub and I have tried plugging it with rags but nothing seems to help a lot. The 4 - 8 ohm mismatch isn't helping me either. Pretty sure that the main problem is the box is way too big and it probably leaks as well. I think when I get some time I will reuse the amp and get a sub that matches it and build a new enclosure ( not fiberglass this time ). In the mean time I think I will try using the bandpass box from my car and play with it for a while and try not to burn the amp up at the same time.

 

[Operandi]

Quote:

Originally Posted by Swingtops /img/forum/go_quote.gif interesting thoughts, I used a port from a 10" sub and I have tried plugging it with rags but nothing seems to help a lot. The 4 - 8 ohm mismatch isn't helping me either. Pretty sure that the main problem is the box is way too big and it probably leaks as well. I think when I get some time I will reuse the amp and get a sub that matches it and build a new enclosure ( not fiberglass this time ). In the mean time I think I will try using the bandpass box from my car and play with it for a while and try not to burn the amp up at the same time.

Any good car amp will handle 4ohms, better home amps will handle it too. There are relatively cheap sub woofer plate amps designed specifically for this.

A bandpass box is going to be worse, don't waste your time. It's really only used to increase power handling, Bose also uses it hide the distortion of Acousitmass (aka **** sub woofers). If you want a sub for home use the box has to be modeled for home use.

 

[kgb_m3]

Quote:

Originally Posted by Operandi /img/forum/go_quote.gif That leaves either buying or building. Having heard lots of commercial speakers (and seeing the price tag) and a couple of DIY designs I'm all for building (as you've probably figured out by now). Dayton sells pre-fabbed sub cabinets now so that makes it incredibly easy, the Parts Express site seems to be down at the moment so I'll try to get a link tomorrow.

Quote:

Originally Posted by LUCIDD /img/forum/go_quote.gif hehe... sell the sub on craigslist then put that money towards a new home-sub. __________L

That sounds like a way to go if it sells. The JL sits in a custom made sealed box for the m3's trunk, sub faces down and the box is pretty long and flat making it impossible to use under my computer desk. The thing is though, I also have a 250x1 JL amp. If I can maybe use that with to at least hear how it sounds and maybe get a different enclosure for it, tune, etc...




Quote:

Originally Posted by LUCIDD /img/forum/go_quote.gif Operandi is right. But another solution - a cheap one too, is to buy an ac-to-dc adapter. You can find one on ebay for less than $20 shipped. - I included a pic. This will work if you have the car amp - so power the car amp with the adapter-transformer. Swingtops, this will not work for you unless you have a car amp.

Hmm, how would that work? The adapter is made for small portable electronics with at the current rating at most likely less than 1A, somewhere in the mA. How would that provide enough current for the JL amp? I would have to build a custom power supply, unless I'm missing something...

 

[LUCIDD]

oops... maybe an oversight of mine...

adapter-transformer is to convert from Ac to Dc --- but never thought about the Amps /current if it is enough. Make custom transformer?? - or can you power the car amp with AC?

________________L

 

[kgb_m3]

Quote:

Originally Posted by LUCIDD /img/forum/go_quote.gif oops... maybe an oversight of mine... adapter-transformer is to convert from Ac to Dc --- but never thought about the Amps /current if it is enough. Make custom transformer?? - or can you power the car amp with AC? ________________L

The transformer is to step down AC voltage to a desired number, say 35v, then you usually have a bridge that turns AC to DC. Car amps take DC only and usually can run off ~13-16v DC. They draw high current that the ac to dc wall adapter is unable to provide. For example my JL amp is 250watt, you divide that say by 14v and you end up with approximately 18A of current.

 

[Operandi]

Quote:

Originally Posted by kgb_m3 /img/forum/go_quote.gif That sounds like a way to go if it sells. The JL sits in a custom made sealed box for the m3's trunk, sub faces down and the box is pretty long and flat making it impossible to use under my computer desk. The thing is though, I also have a 250x1 JL amp. If I can maybe use that with to at least hear how it sounds and maybe get a different enclosure for it, tune, etc...

If you have the T/S parameters you can have someone model it for you to see if would work well for a home sub, wouldn't be too hard at all.

You would need a pretty big power inverter though to use the car amp on AC. It's power consumption should be documented or you can just look at what kind of fuse it uses to get an idea of it's max current draw to determine how many watts you would need.

By the time you got a bigger enough inverter you would probably be half way there to a new amp like this 300 watt BASH.

 

[kgb_m3]

I don't think I want to mess with car stuff in the house, rather try to sell it. I'm set on buying a Dayton sub, enclosure and plate amp. Can't decide between the 8" or the 10" HF series. It will be mostly used for games and music, never movies.

I'm also thinking of returning the Polks and building my own monitor type bookshelf speakers using Dayton components from parts express. That way I can pick a set of nice mids and highs, make custom passive crossover that will be tuned exactly how I want.

Meanwhile I only have about 15% of the amp parts, still waiting on stuff to arrive so I can start the build and figure out what to do with those Polks. I have a feeling once the amp is plugged in I would want to upgrade those and by then I'll be too late to return.