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Post by Boomzilla on Jan 9, 2015 17:28:58 GMT -5
Assuming is maybe not a good idea on this...
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Post by leonski on Jan 9, 2015 19:08:38 GMT -5
Boom,
In general, you want a high ratio of INPUT impedance of your amp to OUTPUT impedance of the PRE. 5:1? 10:1? Higher is usually better, up to a point. The goal is to stay away from the LOW end of the ratios. And dont' forget that (just an example!) your amp may be rated for say 33k Input Impedance. but at 20hz? It MIGHT be as low as 20k or maybe lower. At 20Khz? The impedance might ALSO be way down. Many (most?) manufacturers are reluctant to give up such information as min and max input OR output impedance. An ALL EMO or ALL XXX system should Not have such problems. After all, ONE company made all the stuff.
My preamp, a Parasound P5 has built-in high and low pass filters. They are 'only' 12 db / octave. Fine for removing the lows from the main speakers. The natural 'fall off' of the mains at the low end WITH the crossover slope really rids the mains of LF energy very quickly.
But, I use the crossover in the sub. Why? It is 24db / octave and cuts the higher frequencies very quickly. With a 45hz crossover, that works out to 24db down at 90hz. Hardly a problem. Running a full-range signal to the sub might result in useful output to 150hz or higher. Can't have THAT!
I'd suggest that a SPL meter, like the analogue Radio Shack AND the test disc would allow you to do a real good guess of crossover frequencies. Do the sub first. I won't give directions here, because it may end up being TOO detailed and long, but think about what the GOAL is and proceed. Me? I tried to get the crossover frequency 6db or MORE below the level at which the speakers were playing. So, the LoPass was below and the HiPass above that point. The result? NO output peak AT CROSSOVER.
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Post by Axis on Jan 9, 2015 19:16:45 GMT -5
Boom here is my decades of advice. Forget all this crap and run your mains at full and let that sub go just shy of being localized.
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Post by namikis on Jan 10, 2015 9:54:48 GMT -5
Hi KeithL - Agreed point for point. Yes, specifications are valuable and necessary for design engineers (of which I'm not). My assumption is that the specifications published for any given amplifier or preamp are those that the maker assumes will cast their product in the most favorable light. Are the specifications useful? Probably not, because the consumer (if they even know what the specifications mean) doesn't know how the measurements were taken. Full power? Half power? Wherever on the power band the specification came out the best? At what frequency? Often, no way to know... Do I care what someone else thought of the sound? Maybe a little, but not very much. Why? Because I have no way to know what aspects of audio are important to the other listener. As one Lounger said recently (and very profoundly): "Reviews are written for the reviewer." So how do I judge the quality of an electronic component? By listening. I know what live music should sound like (yes, even in my own living room, since my daughter has been a musician for many, many years and we were the only parents consistently willing to provide a practice venue for various string quartets). If the device under test doesn't make known recordings sound like live music to me, then I don't want that component. Has my hearing changed over time? Yes. Has the sound of my room changed since adding absorbers, etc.? Yes. Do I still know what live music sounds like to me? Yes. Do I still care about specifications in spite of all this? Yes. Why? Because I'm stubborn enough to think (probably mistakenly) that I can at least infer some evaluation of sound quality based on specs. Regardless of that, if the component doesn't sound right, regardless of specs, then I don't want it. Listening trumps specs every time. Am I a curmudgeon? Yes! ---- New here but my exp is very similar to Boomzilla's my Oppo 105s balanced out do not have enough oomph to drive amps - any amps I have thrown at it. Tried it for a month, had to go back to having a pre. Agree that the XSP-1 g2 gets better after a week or so. I do not use the bass mgt as my speakers are full range, but would sure be nice to have the controls in the front if I had a sub in the system. I have been switching back and forth between balanced and unbalanced cables (using admittedly a cheap balanced interconnect). Balanced is a very small tad quieter, but the bass is weaker (could be my cheap cable), so I am using unbalanced so I can have the Carver C-9 in line for holography (using the processor loop for my tape decks). Cheers, Namikis |
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Post by Boomzilla on Jan 10, 2015 13:26:33 GMT -5
I find that my mid to upper bass sounds crisper and cleaner if I roll off the bass at the preamp. When I run my speakers full range (and they're specified as being -3dB at 32 Hz.), they seem to muddy up the sub. Phase interference? Quite possibly. But with the mains in high-pass mode, and the sub set right, you can't tell where the transition happens. AND the bass sounds cleaner.
No contest in my room. YMMV
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Post by leonski on Jan 10, 2015 14:11:38 GMT -5
That's pretty much my observation, too. Full range mains = muddy mid-bass. Indistinct, even, with poor note definition. The LF amps appreciate not having a full-range signal, too.
Again, it's probably a good idea to ignore most specs. -3db @32hz? Is that in-room, and if so what room or in some kind of anechoic chamber? I keep it simpler and know from running a FEW test tones that my mains give up somewhere mid-30s. Which is why I set my crossover to 'em ABOVE that point.
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Post by stlaudiofan1 on Jan 11, 2015 12:04:48 GMT -5
At some point, turn-ON surge may become an issue. A dedicated outlet MAY be indicated. Now, I'm doing a similar amp scheme with my panels. A Parasound A23 of 200x2@4 per speaker, which is a little less than I had with the 'd' amp these replace. Each amp has an input and output to another channel. so, I run ONE single ended to the amp, and a SHORT loop-over to the other channel. But the GOAL? FORGET the Speaker Level Crossover and go to a Line Level Crossover BETWEEN amp and PREamp. You will gain as much as 3db of apparent amp power since right now, EACH amp is dealing with the Full Range signal and the speaker crossover is sorting it out. Limiting each amp to the frequency range of the driver it is DIRECTLY connected to is good. And besides, have you Priced the PREMIUM caps and big AIRCORE inductor needed for THAT modification? Not to mention the fact that it would NOT fit where the current crossover is, with the iron core inductor and physically smaller caps. Just my opinion, but while it seems Maggies DO respond well to Your Plan, the line level crossover is a whole New Deal You just MIGHT want to wander over to Audio Asylum and get with the Planar Asylum folks and read, than ask a few questions. They have a huge knowledge base and a bunch of folks willing to help with this specific issue. And, from our FWIW department? I'd take the drivers out of that ratty MDF frame and get some NICE OAK, MAPLE, CHERRY or perhap MAHOGONY, for a reframe / stand. Sound improves when you get RID of that MDF which is nasty stuff. You ALSO need to keep the INPUT impedance of the amps in relation to the OUTPUT impedance of the preamp in mind. The spec says 50k input impedance. I'd make SURE that is for balanced, too, which would work out to 25k per LEG. (it adds). If the preamp is say, 1k or LESS per leg, you're golden. Rule of thumb is what? 5:1 ratio? But it varies by frequency, so may have some weird effects at the highest or lowest frequencies. Thanks for the feedback. Yes, the whole crossover thing has my heighten awareness for quite some time. Some of those guys are doing crazy complicated stuff like using tube amps for the highs and SS amps for the lower frequencies. My my goal was really just getting double the power. I'm not all that concerned with bi-amp benefits. I'm more concerned of any negative impacts it may introduce. When I asked Emo about exchanging the 1Ls for XPA-1s, they brought up trying 4 1Ls. They said they came off a recent road show where they compared 4 1Ls to two XPA-1s and the 4 1Ls faired very well. I chose that option based partially on that feedback and it prevents the returning my existing 1Ls effort. |
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Post by leonski on Jan 12, 2015 3:08:49 GMT -5
What is your speakers crossover frequency? That will have the most influence on which 'way' runs out of power first, if you are inclined to NoseBleed levels. GAIN is very important, too. Since the gain of the XPA-1 and the 1L is the same, that's a WASH. However, the input impedance is usefully higher in the 1L and so you stand less chance a bad interaction if your preamp has output impedance toward the HIGH side.
I considered a QUAD of the 1Ls, too. But ONE downside was that I'd need an additional duplex outlet dedicated to a pair of amps in addition to the duplex I NOW have just for amps. NOTHING else is connected to that circuit and I use a PSAudio Soloist outlet which retails for about 200$. I'm figuring somewhere from 500$ to 700$ additional for the pleasure of the 4x 1L amps. And I'm not even going to get into the storage / rack issues involved, either. I'd need a double level rack behind EACH speaker to make that work. With attention to cooling, wire management and the 'look'.
'Fared very well' is, IMO, sellers talk. I'll bet NOBODY could tell 'em apart except MAYBE near redline. In the linear portion of the power output and level matched, No Way could you tell 'em apart.
I found for ME, that a pair of good stereo amps worked wonders. The drop in power of 100 watts (500 watts to 400, per speaker) is certainly NOT a deal breaker and the a/b amps ability to provide long-term power, as opposed to the time limits of the 'd' amp they replace, is MORE than a good trade.
Next Step? If you find you need MORE power, replacing the speaker level crossovers with active OR passive Line Level crossovers between the main amp and preamp will net as much as an additional 3db. bringing you to within a db or so of maximum power from the XPA-1 I think the XPA-1 has that 'class-H' power supply, to, of which I'm not the biggest fan.
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Post by stlaudiofan1 on Jan 12, 2015 23:28:37 GMT -5
Well....I hooked them in and the difference is not subtle. 4 of these bi-amped don't sound like 2 more of the same amp. It's remarkably transparent and effortless. I don't even think my ERC-3, preamp and first 2 1Ls are broken in yet, much less the additional 1Ls straight being out of the box. Can't wait for this to settle in.
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Post by novisnick on Jan 12, 2015 23:56:36 GMT -5
Well....I hooked them in and the difference is not subtle. 4 of these bi-amped don't sound like 2 more of the same amp. It's remarkably transparent and effortless. I don't even think my ERC-3, preamp and first 2 1Ls are broken in yet, much less the additional 1Ls straight being out of the box. Can't wait for this to settle in. Isn't life grand! More of a statement then a question! |
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Post by stlaudiofan1 on Jan 13, 2015 10:45:05 GMT -5
BTW. I'm using the 1X2BAL Emotiva XLR splitter. It is completely transparent, as far I as I can tell. I'm running 2 3ft Mogami Gold XLRs to 4 2ft Mogami XLRs into the 1Ls. I should also mention these amps are plugged into 2 Richard Gray 400s. Additionally, I tried the amps straight into the Richard Grays vs each channel of amps plugged into their own Emo CMX-2 plugged into the Richard Gray. Each channel of amps going through their own CMX-2 plugged into the Richard Gray offered an additional small level of refinement.
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Post by garbulky on Jan 13, 2015 10:56:16 GMT -5
BTW. I'm using the 1X2BAL Emotiva XLR splitter. It is completely transparent, as far I as I can tell. I'm running 2 3ft Mogami Gold XLRs to 4 2ft Mogami XLRs into the 1Ls. I should also mention these amps are plugged into 2 Richard Gray 400s. Additionally, I tried the amps straight into the Richard Grays vs each channel of amps plugged into their own Emo CMX-2 plugged into the Richard Gray. Each channel of amps going through their own CMX-2 plugged into the Richard Gray offered an additional small level of refinement. Hi stl. Thanks very much for letting us know about using four for bi amping. I just so happen to have bi amp terminals on my axiom. And I really want to get an XPA-1 because of the larger transformer but it's $$. So it helps to know that going XPA-1 L's at the start and later adding on a pair to bi amp is a worthwhile endeavour. If you have any more impressions to share on the sound quality or differences noted, I would much appreciate it. |
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Post by djoel on Jan 13, 2015 11:02:03 GMT -5
Can someone with the know how either draw me a chart, or a fancy schematics on the how one biamps connections to the preamp, either xlr, or rca along with speaker wires to the speakers.
All of a sudden it seems to me like lots of wiring, and potential to fudge things up quickly!
But I could be over thinking this of course!
Thanks
Dan
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Post by Boomzilla on Jan 13, 2015 11:08:01 GMT -5
Simply jump the input signal to both amplifiers (both amps get fed the same signal). The speakers' crossover will do frequency division. So, in effect, you have one amplifier driving the woofers of the speaker & another amp driving the mids/tweets. I've done the same using a stereo amp for each channel - works like a charm (AND with some audible benefits). All this happens at the OUTPUT of the preamp. The preamp has no more than it's specified number of channels (unless you want to run two preamps, and nobody does). So full range signal into the preamp - let the preamp separate subwoofer from main outputs - main preamp output feeds two power amplifiers (rather than one) - each amp feeds the individual (and electrically unjumpered bi-amp input terminals of the speakers. Like This:  |
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Post by moko on Jan 13, 2015 11:26:26 GMT -5
When I asked Emo about exchanging the 1Ls for XPA-1s, they brought up trying 4 1Ls. They said they came off a recent road show where they compared 4 1Ls to two XPA-1s and the 4 1Ls faired very well. I chose that option based partially on that feedback and it prevents the returning my existing 1Ls effort. i think that's a great idea. 35 watts of class A for midrange and tweeter is a lot. so you should set class A for mid+tweeter and class AB for bass. |
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Post by garbulky on Jan 13, 2015 11:48:12 GMT -5
Does anybody know if bi amping in the manner Boomzilla showed will double the impedance (or halve it)? |
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Post by Boomzilla on Jan 13, 2015 12:25:29 GMT -5
No impedance difference at all. Below the high-pass crossover, the impedance rises to infinity. Above the low pass crossover, the impedance rises as well. ONLY the frequencies in the bandwidth of the speakers' crossovers will be seen by the amplifier channel driving them.
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Post by garbulky on Jan 13, 2015 13:22:41 GMT -5
Very interesting.
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Post by djoel on Jan 13, 2015 13:23:44 GMT -5
Simply jump the input signal to both amplifiers (both amps get fed the same signal). The speakers' crossover will do frequency division. So, in effect, you have one amplifier driving the woofers of the speaker & another amp driving the mids/tweets. I've done the same using a stereo amp for each channel - works like a charm (AND with some audible benefits). All this happens at the OUTPUT of the preamp. The preamp has no more than it's specified number of channels (unless you want to run two preamps, and nobody does). So full range signal into the preamp - let the preamp separate subwoofer from main outputs - main preamp output feeds two power amplifiers (rather than one) - each amp feeds the individual (and electrically unjumpered bi-amp input terminals of the speakers. Like This: Thanks Boom very helpful & nice illustration , so the same goes with pairs of amps per speaker ? I'm just trying to wrap my mind around the connections 2-> Amps to the Right side of a pre/pro, and then 2-> more amps going to the Left channel of the same pre/pro! That's four amps that are going to the pre pro, lets say an XSP-1 that will translate into 2 channels. I guess, Y connectors would be use for such method. Sorry about disrailing the conversation, I'm a little dense at times  Djoel |
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Post by leonski on Jan 13, 2015 13:39:32 GMT -5
Gar, Are you asking about between AMP and speaker OR between preamp and amp? I'll address between amp and preamp. What Boom is calling the 'source', I'll call the preamp. And YES, the impedance of the amps will be seen as 1/2 the single channel value. IF you use a splitter from preamp to amp. So, and this is for single ended now, IF your input impedance per channel is 22k ohms. Now your preamp is seeing 11k ohms and must have low enough OUTPUT impedance to avoid interaction. I'd say anything 1k ohms or LESS output impedance of the preamp is OK for this situation. Less is somewhat better. For BALANCED, it is a little more complicated. When the manufacturer says the balanced input is 50k ohms, that is 25k ohms PER LEG. You have a +(plus/positive) and a -(minus/negative) AND a ground/shield. So your 50k ohms turns into 25k PER LEG. Than the same rules apply. IIRC, you want AT LEAST 10:1 ratio here. Don't forget that the spec is probably some kind of nominal or average value. At frequency extremes, impedance MAY rise dramatically and effect the 'ratio'. sound.westhost.com/bi-amp.htmThe BEST way to impliment a TRUE biamp system is with a crossover BETWEEN main and pre amplifiers. I believe the amps, will STILL see a full bandwitdth signal if you don't. And you will NOT gain the full benefits of biamp which could be as much as an additional 3db. unless you REMOVE the speaker level crossover and wire the drivers directly to the respective amp. Line Level crossovers are EASY to make and the 'passive' version doesn't even need a power supply, though lead length is important (won't drive long runs) and you need to know the input and output impedance of what you're hooking up. An ACTIVE line level crossover uses a good DC power supply AND opamps. And input / output impedance is of almost no consequence while it'll drive longer cables. ME? my passive crossover will be located RIGHT AT the stereo amp behind each speaker. PLEASE read the above linked article. It also explains WHY boom's assertion that 'ONLY the frequencies in the bandwidth of the speakers' crossovers will be seen by the amplifier channel driving them' is INCORRECT. Without crossover BEFORE the amp, it is still burdened with a full-range signal and you won't get Full Benefit of 2x amplifiers. This is where I now find myself. In process of getting a 2-way crossover together at Line Level. It has Very Low capactitance values and I'm putting it in an Altoids case. One per channel! And while I'm using Radio Shack boards, other parts are more 'premium', especially the Caps and RCA connectors. |
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