glens

Need to change the thread title: "Heresy 1 clean but needs needed refinishing"

Back in '78 $800 would buy 1000 gallons of gasoline at retail. Nowadays, what, maybe 300? And I'd not buy a pair of '78 Hereseys for $800 no matter how mint they may be. $800 would represent exceptional value-holding ability but even at 30% it's not all that... It's more the nature of fiat "money" that $800 could even be asked at this time, IMO.

Bi-amping doesn't require an active crossover, just a low-level one. This is usually done actively, though, for reason. But doing it digitally is actually much simpler than in analog if you also want to shape response and/or time-align. Don't worry, your tube magic will pick right back up where it left off.

Black with contrasting tonsils.

Prolly would (except maybe level matching 'twixt drivers). Where you gonna get one?

I find it amusingly interesting that most of the improvements described (in the snippets provided in the article) as results of decoupling the speakers are almost verbatim the improvements usually described as results of spiking speakers that had been sitting on padded carpeting! It's utterly impossible for the same improvements to be achieved by anchoring a previously-floating speaker as by floating a previously-anchored speaker. This, in particular, is a perfect example of expectation bias being debunked by careful measurement; as well one of careful measurement being decried by those who "know what they heard."

First things first. Swap drivers between cabinets and see whether the problem follows the driver or stays with the crossover. Don't even need any test equipment for that action. I would not be surprised if the same cabinet had the same symptoms, and would then check all the connections in/on the crossover as well the connectors on the ends of the wires going to the driver. Crossover components would be the final thing to check if it gets that far. That's my assumption and I'm sticking to it.

What, in your opinion, was left out?

Without looking it up, I believe the threshold for needing hearing protection in the workplace is in the low to mid eighties...

Yes, a very good read. Thank you. Amazing how changes can be heard when they're wanted and not heard when they're not wanted, but measurement bears true witness.

It depends from which direction you're viewing it whether it's an input or output element. Look at it this way: without error correction the second channel would be able to "run amuck" with the signal and the situation would not only be non-optimal, but actually (quite?) undesirable. Certainly, the channel 1 error amp cannot do all the correction for both channels. In any event I much prefer the method employed by the Hypex boards.

No disagreement on that much here. But are you suggesting that channel 2 does no error correction of its own any longer? I'm kind of back to getting the impression that's what you're suggesting. (Channel 2's error amp inverting input is fed equal parts of both channel outputs.) And you've not yet answered my question regarding the double dose of distortion at the channel 2 output relative to that of channel 1's output. Do you see or not see that occuring?

What have you got for response measurements so far, Dave?

Well, there's really no way that could happen in any event (before - apart from the fact it will always occur sans active crossovers with proper delays established). As to the topic of this thread I've got no opinion other than that the only unsafe amplifier would be one too powerful which is used too powerfully. Who'd care if a 5 watt amp was overdriven? Other than perhaps the degraded sound quality there'd surely be no harm to any of the drivers or other components in the cabinet. Even 30 watts overdriven would be fine if you could stand the volume it would produce inside a residential structure, I'd think.

My opinion is that I'm a fan of continuous solid surfaces to allow the expanding waves' uninterrupted growth / development. In that vein, I don't "grok" a less-than-solid coupling of the cabinet to the floor. If I had a pair of Chorus speakers with compromised risers and I didn't want to fashion replacements, I'd remove them and set the cabinets directly on the floor.

By virtue of my post (from an earlier page) being quoted, I understood "right off" that he was reading through the thread and was at that point inspired to offer his opinion, before having finished catching up. Done it many times myself... Slack given.

I think you're blowing my mind. Not quite sure what you said (I work nights and just awoke). Channel 1 output goes via R108 to its negative feedback section as well via R3 to channel 2 nfb section, which still is getting fed channel 2 output via R208. Are we on the same page? In terms of negative feedback both channels still operate 100% normally, it's just that channel two is primed with the inverse of the channel 1 output instead of its own discrete signal. Maybe we're saying the same thing in that regard, just differently?

It also uses it as a unity gain inverter. It still gets used in its normal capacity for error correction of its amp channel. Instead of simply inverting the low-level input signal and driving the second channel with that, the method used takes the already-amplified signal, drops it down, and injects it (paralleled) into the negative feedback loop of the second channel. So the second channel starts with all the distortions / colorations (house sound) of the circuitry. The distortions et. al. inherent in the amplifier appear once in the directly-driven channel, then the second (inverted) channel adds them again for the inverted signal. Do you agree that this is what happens with this topology?

Mixed drinks... Yuck. Give me straight-up whiskey, please.

I saw that right off, but had mistakenly thought you'd suggested that in so doing, the second channel would be giving up its own use of its error amp. Do you agree that the method would tend to impart a double dose of "house sound" to only the inverting channel?

http://sound.whsites.net/project20.htm This is how the Crown D75 amp that I am bench testing does it. See the first portion of linked page and Fig. 1. What schematic are you referencing? This is the D75: The very one I looked at. I just reviewed the situation and see that I was referring to what you'd said after the snippet I'd quoted. Somehow I'd gotten the notion that you'd gotten the notion that the inverted channel wouldn't be using its own negative feedback in the Crown. I don't see that suggestion today. It was a bad inference on my part. Of the two methods, I'd prefer to feed the second channel with an inverted version of the original, the way it's done on the NCore boards. Distortion is going to be minimal, but not non-existent, through the first amplifier channel, and feeding the inverting channel with the result of that doesn't seem as elegant to me. Assuming both channels were perfectly matched that means the inverted portion of the waveform would contain twice the distortion using the feedback-derived method. Granted that the two input buffers on an NCore board aren't going to be exactly equal, thus the chance for dissimilar "treatment" between the two halves of the output waveform, but at least there won't be a double "stepping on" for the one channel. This entire post merely serves to illustrate my ability to (overly?) consider minutiae...

I think you're good to go. I'm using a ~50wpc amp with my Forte IIIs in a room >500 square feet and it's more than plenty. By a lot.

Nice disclaimer. I don't care for the seafoam carpet, either :-)

@DizRotus There - worked that time...

@DizRotus I guess I don't know how to do that. Supposed to be some way to call out to a member. I believe he'd mentioned using corner horn cabinets for DJ/PA work. If he can be gotten 'hold of I'm sure he'll have workable input to this thread.