Preferred LSi25 hookup

snake1 · June 2013

I'm curious about hooking up a pair of LSi25's. I've looked at a few other threads and want to make sure I'm right about my options.

1. Make sure jumpers are in place and simply use speaker wire inputs. As I understand this will work the subwoofer as well since I have an external amp??

2. Use the LFE out from my Onk to send the signal and use the internal amp for the sub.

Am I correct about these and is there a "best" way to hook them up?

EndersShadow · June 2013

snake1 wrote: »

I'm curious about hooking up a pair of LSi25's. I've looked at a few other threads and want to make sure I'm right about my options.

1. Make sure jumpers are in place and simply use speaker wire inputs. As I understand this will work the subwoofer as well since I have an external amp??

2. Use the LFE out from my Onk to send the signal and use the internal amp for the sub.

Am I correct about these and is there a "best" way to hook them up?

The "Best" way is going to be the way they sound best to you so between those two the "best" may vary room to room and setup to setup. Using option 1 may work better than option 2 for you or vice versa. Keep in mind though with Option 2 you may need a y splitter if your receiver only has 1 sub pre-out since you will have to run one LFE cable to each of the towers.

snake1 · June 2013

EndersShadow wrote: »

The "Best" way is going to be the way they sound best to you so between those two the "best" may vary room to room and setup to setup. Using option 1 may work better than option 2 for you or vice versa. Keep in mind though with Option 2 you may need a y splitter if your receiver only has 1 sub pre-out since you will have to run one LFE cable to each of the towers.

I was leaning toward the first one because my amp puts out more than the internal one. I will however try both and see what happens.

EndersShadow · June 2013

snake1 wrote: »

I was leaning toward the first one because my amp puts out more than the internal one. I will however try both and see what happens.

Either option still uses the internal amp to power the sub in the speaker so thats a moot point. Its more about using your AVR to set the crossover with its auto cal (Option 2) or running the tower full range (Option 1)

snake1 · June 2013

EndersShadow wrote: »

Either option still uses the internal amp to power the sub in the speaker so thats a moot point. Its more about using your AVR to set the crossover with its auto cal (Option 2) or running the tower full range (Option 1)

I thought somehow the internal amp could be bypassed. I misunderstood. So will the sub be driven by using speaker wire inputs only or do I have to use LFE or Line-in for the sub?? Sorry, just trying to wrap my head around the idea. Not as simple as hooking up my 12s.

EndersShadow · June 2013

snake1 wrote: »

I thought somehow the internal amp could be bypassed. I misunderstood. So will the sub be driven by using speaker wire inputs only or do I have to use LFE or Line-in for the sub?? Sorry, just trying to wrap my head around the idea. Not as simple as hooking up my 12s.

The internal amp will ONLY ever power the sub so you are still using your amp its just powering the top section of the speaker.

Look at the manual: http://www.polkaudio.com/downloads/manual/LSi25_MN.pdf

Technically there are 3 ways to connect the speakers to your setup. Again which one will depend on what you like best and also on your gear.

I like the 15's because they take all that out of the loop for me, I just connect them straight to my amp and call it a day.

snake1 · June 2013

EndersShadow wrote: »

The internal amp will ONLY ever power the sub so you are still using your amp its just powering the top section of the speaker.

Look at the manual: http://www.polkaudio.com/downloads/manual/LSi25_MN.pdf

Technically there are 3 ways to connect the speakers to your setup. Again which one will depend on what you like best and also on your gear.

I like the 15's because they take all that out of the loop for me, I just connect them straight to my amp and call it a day.

I gotcha. So, just run auto-cal with the jumpers or without run from LFE or line-in. I did read the instructions but I'm just making sure I understand what I'm reading and seeing. It is a bit complicated but shouldn't be too bad now. I was looking for 15's but found some 25s locally so probably going to jump on those. Besides the different subs, the mid and highs are the same setup like the 15s and 9s I'm assuming.

snake1 · June 2013

Been talking with tech support at PA and the guy selling the 25s. Both say you can turn the internal amp off, put the jumpers in place, and run the subs plus the mid and hi array all off an external amp. Thoughts??

EndersShadow · June 2013

snake1 wrote: »

Been talking with tech support at PA and the guy selling the 25s. Both say you can turn the internal amp off, put the jumpers in place, and run the subs plus the mid and hi array all off an external amp. Thoughts??

So then why bother with the 25s if our not going to use the built in amp?

Do what you want but the point of the 25s was to have a built in amp to lighten the load on an amp for the mods and highs.

I would personally just look for the 15s if that's the case, seems like a waste if 2 plate amps otherwise.

My 2 cents

tonyb · June 2013

I could be wrong, but I'm not aware of any way to "turn off" the internal plate amps on the 25's. Not without doing some mods to the inside of coarse.

Never been a big fan of speakers with built in amps myself.

snake1 · June 2013

EndersShadow wrote: »

So then why bother with the 25s if our not going to use the built in amp?

Do what you want but the point of the 25s was to have a built in amp to lighten the load on an amp for the mods and highs.

I would personally just look for the 15s if that's the case, seems like a waste if 2 plate amps otherwise.

My 2 cents

Well, they are available is the main thing, they have bigger subs, cause I have a big room to fill. I understand the point of the internal amp, but the fact that it can 'possibly' be bypassed is kinda sweet in case the internal amp ever goes out maybe?? I'm going to try them both ways, I was just curious to see if it was possible and also to see if anyone knew of a preferred method to hook them up is all.

tonyb wrote: »

I could be wrong, but I'm not aware of any way to "turn off" the internal plate amps on the 25's. Not without doing some mods to the inside of coarse.

Never been a big fan of speakers with built in amps myself.

It will require a little bit more tweaking during setup, but shouldn't be too bad. There is a switch for 'off' 'auto' and 'on' on the back of the plate amp. Could it be that simple?? I don't know for sure but its possible. We'll see. Thanks for the input!

EndersShadow · June 2013

snake1 wrote: »

Well, they are available is the main thing, they have bigger subs, cause I have a big room to fill. I understand the point of the internal amp, but the fact that it can 'possibly' be bypassed is kinda sweet in case the internal amp ever goes out maybe?? I'm going to try them both ways, I was just curious to see if it was possible and also to see if anyone knew of a preferred method to hook them up is all.

It will require a little bit more tweaking during setup, but shouldn't be too bad. There is a switch for 'off' 'auto' and 'on' on the back of the plate amp. Could it be that simple?? I don't know for sure but its possible. We'll see. Thanks for the input!

Good luck. I am assuming you've talked to Polk to discuss how to go about doing this correct?

snake1 · June 2013

EndersShadow wrote: »

Good luck. I am assuming you've talked to Polk to discuss how to go about doing this correct?

I have. I spoke to the current owner and tech support. When I read the directions for wiring, I believe this was this first option for hookup. Just using wires and jumpers.

ZLTFUL · June 2013

OK...sorry for not piping up sooner.

First, there is no way to actually bypass the plate amp. At least not without serious internal re-wiring as Tony pointed out.

Now let's break this down a little bit.

Think of the LSi25s as LSi9s sitting on top of standalone subs.
The wiring methodology is the same as wiring a pair of subs into your system.

First, you have method one where you use the speaker posts. Jumpers in place or bi-wired, the same thing occurs. Think of it as using the speaker level inputs/passthrough on a sub. The signal is fed to the plate amp but then the signal from your AVR/amp is also fed to the upper half.
Sort of like this: AVR/Amp-->Sub-->Mids/High.

Removing the jumpers and using only the top binding posts takes the sub out of the equation. Signal will only be going to the top portion of the speaker. So I guess technically, *this* could be considered bypassing the sub.

To get a signal to the sub section with the jumpers removed, you can do 1 of 2 things. Connect a pair of ICs to the low level inputs and then hop to the other speaker using another pair of ICs from the output side of the first plate amp. This will utilize the crossover/gain control on the plate amp.

Or you can use the LFE input on the sub (jumpers still removed). This will pass the crossover control to the AVR and is the "Subwoofer Out". You would need to split this signal (Radio Shack and Audioquest both have decent single male to double female IC splitters available reasonably priced) to feed both subs and because your AVR is a 7.1, the LFE signal would not be "stereo". But bass is omni-directional so it may or may not matter to you.

Obviously, you still have the fine tuning that you would do using your AVR's built in crossover/delay/correction functionality but those are the ways to connect up the 25s.

TLDR: Jumpers connected = Speaker wire only needs connected. Jumper removed = Speaker wire connected to top binding posts, ICs connected to one of the IC connection options.

snake1 · June 2013

ZLTFUL wrote: »

OK...sorry for not piping up sooner.

First, there is no way to actually bypass the plate amp. At least not without serious internal re-wiring as Tony pointed out.

Now let's break this down a little bit.

Think of the LSi25s as LSi9s sitting on top of standalone subs.
The wiring methodology is the same as wiring a pair of subs into your system.

First, you have method one where you use the speaker posts. Jumpers in place or bi-wired, the same thing occurs. Think of it as using the speaker level inputs/passthrough on a sub. The signal is fed to the plate amp but then the signal from your AVR/amp is also fed to the upper half.
Sort of like this: AVR/Amp-->Sub-->Mids/High.

Removing the jumpers and using only the top binding posts takes the sub out of the equation. Signal will only be going to the top portion of the speaker. So I guess technically, *this* could be considered bypassing the sub.

To get a signal to the sub section with the jumpers removed, you can do 1 of 2 things. Connect a pair of ICs to the low level inputs and then hop to the other speaker using another pair of ICs from the output side of the first plate amp. This will utilize the crossover/gain control on the plate amp.

Or you can use the LFE input on the sub (jumpers still removed). This will pass the crossover control to the AVR and is the "Subwoofer Out". You would need to split this signal (Radio Shack and Audioquest both have decent single male to double female IC splitters available reasonably priced) to feed both subs and because your AVR is a 7.1, the LFE signal would not be "stereo". But bass is omni-directional so it may or may not matter to you.

Obviously, you still have the fine tuning that you would do using your AVR's built in crossover/delay/correction functionality but those are the ways to connect up the 25s.

TLDR: Jumpers connected = Speaker wire only needs connected. Jumper removed = Speaker wire connected to top binding posts, ICs connected to one of the IC connection options.

Ok, I understand. Just wasn't sure and looking for possibilities.

How do you have yours wired ZLT?

ZLTFUL · June 2013

Since I have 2 stand alone subs already that are getting both of my LFE channels, I use method 1 with them crossed over at 50hz (lowest I could go). But I am planning on pulling my subs and using the top binding posts and LFE for the 25s.

Wildcat445 · October 2014

I can see this being a potential DIY project, to bypass the plate amps. The easiest would be to bi-amp and use an outboard crossover for the sub portion, wiring the woofer terminals directly to one set of the binding posts. Harder would be to design a crossover which would let us run the system from one amplifier.

One reason I have shied away from this LSi25 is due to the anemic 150 watt (seriously??) power rating. My power amp is double that currently. I need the 10" woofer to fill a larger room, as with my current system, and scattering subwoofer cubes around the room is not an option (much as I'd like that quality of bass). Another: how do we know what quality this plate amp has? If I'm running a Mark Levinson or Audio Research power amp, is this little thing going to be up to the same quality? Even if I went in an entirely different direction and used the built-in plate amp and used a tubed power amp of lower power for the passive drivers on top, the difference in amplifier slewing rates would create another sonic mismatch (the solid state amp may react faster to input voltages than the tube amp).

That is the reason some of us do not want "powered" systems. I feel Polk really missed the boat on this design. Locally there are both LSi15 and LSi25 systems for sale, similar price, so it's only a matter of deciding if I want to meddle with the guts of the larger system, or try to live with the weaker bass of the LSi15. I just feel the plate amp, and the inability to bypass it, is the weakest point in what is otherwise a very refined sounding speaker.

EndersShadow · October 2014

Wildcat445 wrote: »

That is the reason some of us do not want "powered" systems. I feel Polk really missed the boat on this design. Locally there are both LSi15 and LSi25 systems for sale, similar price, so it's only a matter of deciding if I want to meddle with the guts of the larger system, or try to live with the weaker bass of the LSi15. I just feel the plate amp, and the inability to bypass it, is the weakest point in what is otherwise a very refined sounding speaker.

Weaker bass?? Have you heard the 15's powered right?

I've got a set and when I had my Carver M1.0t I could get to 109db 12 feet away and my room was darn near shaking stuff off the walls with bass..... Speakers were totally fine with the wattage.

The problem with EITHER of the LSi towers is that the internal cabinet space is too small to dig much lower than they do.... however they do a GREAT JOB of doing what they are supposed to....

I'd take the 15's over the 25's all day long as the woofer size doesnt really make that much of a difference in real life. And the 15's can give you all the bass you want or would need.

Most floorstanding speakers cant truly dig deep enough to be full range, or if they do they are MUCH larger than the LSi's.....

Plus if your doing a HT, you really need a sub regardless. Where you locate your mains is normally not in the best position to give you bass regardless, hence why subs are cornered loaded for a HT setup. The mains are normally located too far from wall boundaries to really give you the right kind of bass. Hence why lots of folks suggest that the LSi 7's are the darling of the line. They are made to dig down to where most folks cross their speakers over 80hz so your not wasting floor space for your fronts and then you just augment them with a couple good subs located properly.

Also dont mistake booming bass for bass. There are lots of big floorstanders that can go boom, but the polks do a great job of providing CLEAN bass, provided you've got them setup right and give them the right amount of power.

I had 550 wpc @ 4 ohms in my Carver M1.0t for them, had them running off a Carver 5 channel with around 200 wpc @ 4 ohms and there was a big difference. I now have them running off a B&K 200.5 which is 375 wpc and they just love the power it can give them.

mlistens03 · January 2018

I know this is an old thread, but in my LSi25s the speaker level input on the sub is connected to the terminals through a screw on post on the back of the amp, it would be simple enough to put one of the rings that goes on the post on a cable to bypass the amp, you would just need an amp running off of a low pass output. One of my amps are toast so I’ve taken them out before

Preferred LSi25 hookup

Comments