Discussion in 'Audio Hardware' started by riverrat, Jan 6, 2019.
Does any test data exist for the impedance curves of the RTiA9 that you know of?
I googled "RTiA9 minimal impedance"
Polk RTi A9 Speaker System HT Labs Measures
Sensitivity of 90.5 db, minimum impedance of 4.49 ohm.
The RTiA9 also drops off the low end much higher. And that body is exactly what's missing with the LSiM when it's under powered.
That may be true for primary tones, but I believe the harmonics and overtones in classical/non-amplified music actually extend farther at both ends than the harmonics and overtones present in rock and other amplified music. For rock, the range is about 60 Hz to 8,000 Hz, with classical, about 40 to 12,000 Hz. And it’s the harmonics and overtones that give the music richness and depth.
It should also be pointed out that the AR3/3a is a 4 ohm speaker with sensitivity of 86 dB.
This model speaker was manufactured at a time when low current tube amplification was the norm and it is also entirely conceivable the speaker's impedance also dips below the 4 ohm nominal rating at certain bass frequencies.
The equipment most commonly available at the time provided acceptable performance from the AR3 - a number of systems being centered around various Fisher 7591 tube receivers which certainly don't have the output or current capability of the later MC2505 SS amplifier.
Since the MC2505 SS amplifier with 4 ohm capability would never have been said to have been inadequate for the AR3, it's frankly difficult to see why the situation should be any different with the LSiM705 - and certainly when run at half power or less.
All I was trying to say is that speaker and amp pairing is much more than specs. Based on what other LSiM owners have said, and what I personally experienced, it seems that the LSiM pair best with high watt/high current amps. Part of that is how it tests vs specs, but also just pure gear synergy. On the spec sheets an amp that can power the RTiA9 should be able to power the LSiM. In reality that isn't always the case.
If you love your MC2505, don't get rid of it. Loving an amp is a perfectly valid reason to not keep a speaker in my opinion. A bad match is a bad match. Same thing can go for the room. And this is why spending more on components isn't always the solution. Sometimes it even results in moving backwards (which is basically the position you feel you've found yourself in).
But since you have the LSiM already psychically with you in your room, it was simply being suggested that it might be worth trying them with a higher powered amp if you have access to one. Nothing beats a home demo, so if you wanted to keep the LSiM for a few more days and see what a higher powered amp can do, you have the unique opportunity to do so. You might love it. You might still hate it. While you're at it you could demo the RTiA9's with the amp too. Either way it should be fun!
Now if you don't have access to another amp via a friend or dealer, well then it might not be worth the effort for the experiment. But having the speakers in house is normally the hardest part, and you've already got that done.
Well I appreciate your input but the speakers have been returned. I do have other McIntosh amplifiers - two with output taps of 2, 4, 8 and 16 ohms and another with taps of 1, 4 and 8 ohms.
Frankly it never occurred to me to try the any of other units with the 705s, but I would have had no desire to do so even if I did. I certainly wouldn't have considered using anything but 8 the ohm taps either since that is how the Polks are rated.
As I said before, I had no complaints with the RTiA9's performance when paired with the same unit I used with the LSiM705s.
Fair enough. It's a little unfortunate Polk rated them on the spec sheet at 8ohm. I feel like it was a little misleading, and kind of sets them up for disappointment (as you experienced).
But man, multiple McIntosh amps in the house is awesome. I would be mixing and matching all the time if I was in your shoes! Enjoy the journey
I don't think that contacting them is a bad thing. You need to contact them in order to send them back. I have this distinct feeling that they want these to go away, not get them back, which means that they will have to do something with them, when they get them.
I would not bring up the subject of you wanting a discount on them, that is just unprofessional and gives the impression that you are just trying to get something more out of them.
If they have any interest or incentive in wanting you to keep them, they will make you an offer. If no, then they go back.
What you should make abundantly clear is, that other than the single quality control issue, you are not unsatisfied in any way, with your speakers and would like another pair. Check and see if your units do or do not have sequential serial number's. They may or may not. If they do, then indicate your desire for another matching pair. If your pair do not have sequential serial number's, which they might not, since they are not sold as a "pair", then leave the pair stuff out and just let you know that you are requesting a single replacement.
That will work very well too, sine they will be aware that you are not returning both speaker's and will be keeping one of the two speaker's.
They will understand that you are sincere about the quality control issue and understand that you are wanting a single replacement for that reason.
And no that you are otherwise dissatisfied with them.
That is interesting. I find that most tower speakers are about 90 dB., give or take a couple of dB. My Monitor 70's Series II are 90 dB.
I have had my 250-Watt large 72-lb. Emotiva power amp since 2012 and I know how it drives tower speakers, shich is all that I have ever had them hooked up to, except to check out other speakers. The only speakers that I have run with the Emotiva XPA-2 are tower speakers, with a sensitivity of around 90 dB.
Driving the RTiA9's was a piece of cake and the XPA-2 did this to loud levels, effortlessly.
Not so, with the LSiM707's. The LSiM707's can take a great deal of power and they can most effectively pressurize a room, but I found that I had to crank up the volume control of the preamp to get these things really moving and doing their thing.
As they have stereo LED indicators on the front panel display, it is easy to monitor the relative power level of this power amp.
It always seemed to me, that they needed more power than an 88 dB. speaker normally would. I don't know if I could personally tell the difference between an 88 dB sensitive speaker and a 90 dB sensitive speaker. I could surely tell that I needed more power than an 88 dB sensitive speaker would suggest.
That has been my impression anyway.
I mean, that I have the power and know that I have the power and can really crank them up, anytime that I feel like doing it.
But, I have my thoughts, that anyone who is under any impression that just any 100-Watt budget "receiver" can crank them effectively, is under a way mistaken impression.
Just my observations...
I'm only going to beat the dead horse one more time. You are mistaken in your quoted thoughts and it's a shame you didn't try a different amp just to give the speakers a fair shot.
Perhaps @Agitater could chime in.
He would be much better at explaining Ohm's Law to you than I can.
I can only inform you that when impedance drops x amount, the maximum amount of voltage the amplifier will be able to supply will also fall in concert. This would result in clipping if more voltage was being called for than the amplifier was capable of at the lower impedance.
Since the amplifier in question is able to deliver 50 wpc (realistically 70 wpc) into 16, 8 and 4 ohms, there is no possibility the amplifier was being overdriven at 25 watts per channel which is far more power than I would even use under normal listening with a pair of 88 dB speakers., even at 2.8 ohms.
I'm sorry my friend, but on this point you are mistaken. The meters on the MC2505 are 99% accurate and the only issue would be if the amplifier was being overdriven. I know exactly what an overdriven amplifier sounds like (ie: clipping) and I can assure you, this was not the case. Even when playing at only 5 - 10 watts (which is more like it) the sonic character of the speakers was unchanged.
Lack of current has nothing to do with how this speaker performed under the conditions I described. Period.
I don't think @F1nut is totally wrong. In general though, where ohm's law is concerned for a given and unvarying load or signal and unvarying current demand, you're correct.
Unfortunately, and I think partly the reason that @F1nut has taken his particular position, a music signal coming from an amplifier is something that it is continuously and constantly varying in voltage, just as the current demand of a loudspeaker like the Polk you had is constantly changing. That's the nature of music that is electronically reproduced from any recorded format.
At the constantly and continuously varying music frequencies (root notes, harmonics, multiple instruments of widely varying frequency ranges, etc., etc., etc.), the current demanded by the speakers is constantly changing according to the demands placed on the crossover and the signal by the individual drivers that inherently shift their phase angles and also perform more efficiently in some frequencies in their natural ranges than others. For difficult speaker designs and for speakers designs for which efficiency specs are stated optimistically and with speakers for which good efficiency and only minor phase angle shifts are quoted for a deceptively tiny frequency range, more powerful amplifiers that can also freely and instantaneously and more easily deliver more current as the poor speaker design demands it, can solve a wide range of problems. For amplifiers of categorically low or moderate power and restricted current delivery (due to the designer's choice of power output design, and choices for high-frequency and low-frequency finals in the output stage), certain speakers can impose current demands that the amplifier just can't effectively meet. In that sort of situation, basically, a poor speaker design beats up on an otherwise wonderful amplifier.
@F1nut has also noted elsewhere in this thread (or another thread possibly) quite accurately I think, that Polk Audio is not the company it used to be. For what it's worth, I agree. So I think you're well off without the speakers because they just didn't get along with your amplification. I think you have excellent amplification that will do great justice to high quality loudspeakers. The best speaker designs just sing without placing ridiculous and unwarranted electrical demands on the amplifier.
By contrast, though you're more or less correct about impedance vs voltage, it's not the voltage that you have to worry about with misbehaving loudspeakers that are placing unusual demands on an amplifier. Rather, it is current delivery and the ability of the amplifier to respond to current demands by a poorly designed loudspeaker that causes the greatest number of problems. Amplifiers provide voltage to the circuit. Loudspeakers demand current in varying proportions according to the quality (or lack thereof) of their design. The more even the current demand of a given loudspeaker (as a whole and with respect to its individual drivers and its crossover, irrespective of whether it's a high or moderate demand), the better a given amplifier design will do with that loudspeaker.
All loudspeaker problems can't necessarily be solved simply by the substitution of ever more massively powerful amplifiers, but I don't think that's what @F1nut was proposing. Again, IMO, you're well shut of those Polk speakers.
I think all highly regarded loudspeaker designers I've met over the years understand how important it is to choose drivers and design crossovers that present impedance loads, phase angle control and current demands that are effectively manageable by a wide range of amplification. Polk is not the company it used to be.
Thanks for your input.
I'm also sure you'll agree that the current needed in a 5 - 10 watt average signal - even at 2.8 ohms - is well within the capabilities of 45 lb McIntosh 50 wpc amplifier (which is quite heavy for a 50 wpc amplifier owing to its overbuilt output transformers and power supplies) which is designed to run at 4 ohm loads all day long at full output, therefore highly unlikely the speakers performed for lack of current. I think that would be an accurate thing to say.
So according to Agitater, the 705’s are “misbehaving loudspeakers that are placing unusual demands” on 66caddy’s amplifier?
Not sure I’m buying this...
I don't think so either.
And certainly not at the modest output levels that I was using with the amplifier.
See 62caddy's beautiful classic McIntosh SS amplifier in the post above.
OK, say your amplifier is the perfect amplifier to drive these speaker's, because that may well be the case.
Say, we figured that the LSiM707's/705's may not be the optimal speaker's to listen to classical music with? I don't listen to classical music, so I have no comment with this regard.
Say we both agree that the RTi series are easier to drive than the LSiM series and say that they are better suited for classical music.
And say, the it is accepted that for what ever reason the LSiM's haven't worked out for you and that they are on their way back.
Say, that we have figured out some of these things and we can all accept both your observations in your system and my observations in my system.
Say that we note that we do need a hefty, preferable solid state amplifier that has a generous power supply that can deliver a lot of current to the LSiM's and that we don't recommend them with lesser able amps.
Now, I want to examine a few things.
Namely, we have those in this thread who have already owned Polk products, including those in the LSiM line.
We are also hearing feedback in this thread from member's who are responding to the sale pricing as noted by the OP in beginning this thread and that we now have some member's which are purchasing their first pair of Polk tower's in the LSiM line.
From what I am reading, is that if we look at the comments of the previous owner's and we look at the comment's of the new LSiM owner's, the seem to fall with the same general observations and that they appear, as a group to be pleased with the LSiM line.
Also noting that the LSiM line is the flagship of Polk's speaker line and has been so for a few years now. With the 707's retailing for a hefty $4k a pair and the 705's retailing for a substantial $3k a pair.
Although I bought my pair of 707's at a Polk 50% sale, I have owned other Polk tower speaker's for a number of years now. Only replacing the RTiA9's with the LSiM707's. And only after reading many, many favorable on-line reviews of the 707's, both by professional reviewer's and those who own the 707's.
Cutaway view of the LSiM707's.
Front view of the similar but smaller 705's.
Properly amplified, the LSiM tower line, seems to be highly accepted by the large majority of those who have reviewed them..
Just to recap. Many of your observations were comparing the LSiM705's at $3k/pr. with your vintage Boston Acoustics T1000, which sold for abound $1k/pr. back in the early 80's (so keep inflation in mind here).
Anyone else have any observations that they might be able to contribute, as to the sound quality and other observations that you might have woth regard to either of the two LSiM tower's?
I'd say Polk's published minimum "steady state recommended amp power" of only 20w is a little unrealistic for these speakers, probably an attempt to sell to as wide a market as possible. Not to say 20w won't produce sound, even loud sound ... but some serious, high quality current is clearly needed to push 5 drivers and a bunch of crossovers to a place where they really sing. McIntosh is good stuff, but even it has its limitations. Anyone else tried driving them with an older mid-powered amp? FWIW, I demo'd the 705's through a Hafler Pro 5000 (SS 325W per side 8Ohms). KT Tunstall's "Eye to the Telescope" (outstanding album, very nicely-recorded vocals, guitars, percussion, bass, some strings) sounded fantastic... open, nuanced, didn't hear any nasality or dullness at all. So there you go.
Maybe I'm in the minority but I feel the true test of a loudspeaker is how well it performs at all listening levels, not just one or the other. Whether reproducing the delicacy of a Mozart Piano Concerto to Led Zepplin at head-banging SPLs, a true high fidelity speaker should be able to do equal justice to both.
A speaker that must be played loudly to sound its best is of little use to me, every bit as much as one that must be played quietly.
All the other speakers I presently own are capable of both. These include the Polk RTiA7, RTiA9, Snell J7, Boston Acoustics T1000 II and a pair of Altec Model 14.
Each has their strengths and weaknesses as there is no such thing as a perfect speaker. But for my purposes and to my ears, I'm more than satisfied with the way they perform, especially for the cost.
You're darn right it is - for the most part. What bends otherwise terrific amps out of shape when they're connected to misbehaving speakers are the transients that demand sudden and large amplitude changes that can occur at frequency ranges centered on frequencies that the speakers reproduce only with dramatic and just as sudden increases or drops in impedance, and with correspondingly unusual phase shifts and rapid shifts in current demand. Music is dynamic in nature, and so are its demands on amplification, crossovers and drivers. Where I split with @F1nut is in the prescription mainly, not the diagnosis.
So my position is that the problem is not with your McIntosh. As @F1nut has said elsewhere, not least because we're all trying to be decent and realistic audiophiles, Polk is the problem in the case you raised - not McIntosh. For the reasons I mentioned earlier, no amplifier can be all things to all speakers. Badly behaved speakers can make the very best amplifiers sound average or even worse. What I'm saying is that the Polks certainly did tax your McIntosh into mundanity, but more power and more current delivery capability would be unlikely to overcome a bad speaker design in this case.
I'm not defending the speakers and I'm not knocking the amp. What I am saying is the amp doesn't have the grunt to properly drive those speakers. It's not that the speakers are badly behaved and it's not a poorly designed amp. It is a poor match. Had you tried a different amp I'm sure you would have figured that out for yourself.
It's called synergy.
Even though other members here have actually heard them with more power and said they sounded "fantastic?"
I certainly agree with your assessment on keeping the McIntosh and finding the perfect match for it...
I was just going to post the same thing. Synergy is real especially when it comes to amps and speakers.
This is something that I have commented on before myself. Many higher end speaker's are now necessarily efficient. As another member has pointed out, the efficiency of the LSiM tower's is a bit less that they may have you believe. I am definitely in agreement with this point.
What I see is a bunch of inefficient but very well designed and manufactured drivers that need to fill a large listening space. My space is 450 sq. ft. and 62caddy has indicated that his space is about the same.
I think the combination, is that a lot of power is needed, meaning current.
I have a lot of SS power, already in place to drive the 707's. I put a lot of power in place years before, to afford me the micro-dynamics and low level detail that you can get with having a lot of power.
Look at some of the new McIntosh SS amp's:
1-Channel Solid State Amplifier
2,000 Watt Quad Balanced Monoblock
3 speaker terminals for tri-wiring
2 Power Modules, 1 Output Module
Is this an insane amount of power or what? Maybe some of their employee's have LSiM's?
I want to clarify, that I listen at far volume levels now, than I have ever listened with during my lifetime in audio.
Having a lot of reserve power, does not mean that you are intending to listen at high SPL's.
Having a lot of power means bass and dynamics at low SPL's.
Although they may or may not work for someone, I don't think I would label the LSiM line as being "badly behaved speakers".
I love their sound and I don't have a single issue with my LSiM707's.
I agree. I don't think it's at all fair to call the speakers "the problem" or a "bad design". Some speakers are more demanding than others. They certainly didn't "behave badly" (whatever that's supposed to mean) when I demo'd them using the beefy Halfer. I think 66caddy's 45 year old moderately-powered McIntosh just wasn't a great match. I'd like to hear from someone else who's driven 705's with a mid-powered amp.
Well in the interest of experimentation I suppose I should have pulled the MC2155 out of the other system (which is 150 wpc with taps for 1, 4 and 8 ohms with full output available at each of these loads) but of course this would have meant a major system change in the secondary system which I have no desire to do at this time - assuming the MC2155 would have made any difference.
My main intent with the secondary system was always for it to be mainly "vintage" but when the incredible offer came up for the LSiM705s, I thought it foolish not to take advantage, especially since I had always gotten good results with the same amplifier with other large Polks (ie A9) previously.
Incidentally the MC2155 is what powers the A9 in my main rig and couldn't be more pleased with the results - and that's using the 8 ohm taps.
In the "vintage" rig, I have an amplifier/speaker selector console which allows the use of either the MC2505 or MC240 with either pair of speakers - either the Altec 14 or the T1000. Since the MC2505 is the "work horse", it gets the most play - and mostly on the Bostons. Other times when I run the Altecs, I'll use the MC240.
Frankly, either pair sound just as good regardless of which amplifier is powering them.
FWIW: Here's a user review on Amazon which coincides with my experience with the LSiM705 on a few key points.
3.0 out of 5 starsVery laid back... Too much for my taste
January 30, 2018
I bought some of these after owning Polk Monitor 60's and Klipsch RF-82 II's. The Monitor 60's had a nice warm tone but weren't very detailed and lacked bass. I heard the Klipsch speakers in a store and was very impressed, so I replaced the Monitors with them. The Klipsch had fantastic detail and outstanding bass, but they were a bit bright, and I missed the warmth from the Polks.
I had never heard the LSiM 705's, but I read great reviews about how accurate they were and how they were a bit warm, and I thought these would be like my old Polks but with much better quality sound. I also bought a Parasound A23 amp with 125 Watts (200 at 4 ohm) to drive these, thinking my old 110W receiver wouldn't cut it.
These speakers are very laid back, as is noted in many reviews. They are a tad warm, but mostly very neutral, not quite as warm as the Monitors. They are super accurate and detailed with a great soundstage. But they are very polite and laid back, to a fault for my tastes. They don't sound bad, but they just don't excite me either.
When I listen to soft rock or jazz, it sounded great on my old Polk Monitors, and they also sound great on the LSiM's. They're more detailed on the LSiM's, and the warmth really brings them out. Pink Floyd, for example, sounds really good. The detail really makes it enjoyable on the LSiM's. This kind of music lacked warmth on the Klipsch speakers and caused fatigue.
When I listen to acoustic guitar, like Iron and Wine, the warmth is nice, but the guitar lacks a brilliance that the Klipsch had. With the Klipsch, it was like the strumming was right there in the room with you and was really exciting. With the Polks, it just sounds laid back, like it's in the background. It's not bad, but it's nothing great either. I just find myself tuning it out and it becomes background music. This kind of music would get a little fatiguing on the Klipsch but the brilliance was really engaging until the fatigue set in.
For pop music or anything with bass, (Beyonce for example) the Klipsch were very exciting. This kind of music was where the Klipsch really shined and the LSiM's fall short for me. The Polks have clean bass and go very low, but they're overshadowed by the mid range which drowns out higher vocals and bass.
Overall, the Polks are just super laid back. The detail and soundstage are nice, but they don't excite me in any way. If you want detailed background music or you listen to music where detail brings it out, these may be great for you. But they are just too laid back for me. Some music sounds good on them, but most music is a tad too boring for me.
And I don't mean to be too harsh -- these are great speakers overall. If these speakers cost $400 each, I'd say they were great. But for what I paid for them, I expected them to blow my mind, and in the end they were adequate but not thrilling to me. I think what may be best for my taste is to go back to Klipsch and try to get a warm amplifier, maybe a tube amp, to try and tame the brightness. I've also never heard the Polk RTi line but hear some people say they really prefer them to the LSiM line.
As for the power needed for these, I find my Parasound A23 seems to be just on the cusp of what is needed to bring them out. I don't think you necessarily need a lot of power, but getting good quality high current power from a separate amp really helps. I've read that they are really closer to 4 ohm speakers. I hooked them up to my Pioneer VSX D912 with 110 watts, and it was just meh at moderate volume and had trouble at higher volume. I'd also recommend a brighter amp/preamp to help bring them out a little.
Edit: I repurchased the Klipsch speakers and did a side by side comparison, driving them both with the Parasound amplifier. Side-by-side, the Polks are way more clear and detailed and have more upper mid-range and highs, with very little on the mid range to lows. The Klipsch feel like they're missing the mid-range and have great lows but harsher highs. The Polks have a better soundstage but far less presence. My girlfriend, who knows nothing about speakers, vastly preferred the Klipschs, saying that they we're far more dynamic and engaging. The Klipsch are way too bright and fatiguing on the Pioneer AVR but are tamed nicely by the warmer Parasound gear, although they are still a little harsh. If I could have the Polks drive the top half of the spectrum and the Klipsch drive the bottom half, I would have a great speaker. There Polks are just not engaging and the Klipsch are too harsh. I'm going to keep looking for the perfect speaker.
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