Skip to main content

Using room acoustics/eq to increase headroom on passive mains (urei 813c's)

Member for

12 years 4 months
i was talking to a dude about these speakers the urei 813c's.

he was saying that when he had them paired w/ a mcintosh 2500 power amp, that he did something (forget what he said) to the amp's transformer, or something that allowed that amp to push all it's wattage as opposed to just the 500 per channel it does unmodified.

anyway, he was saying that he achieved more 'clean' volume or 'increased headroom, by using an eq to pull back about 5db under 100hz, and modifying his room to be 5db hotter in this range, he was able to use make the amp work less hard because those frequencies take a lot of power, and essentially are just distortion of sorts below a certain frequency (think he cited 25hz). So by not making the amp work as hard in this range, it lended more power for the rest of the frequency range, giving hI'm more clean power, and inevitably headroom, because he didn't have to work the amp as hard to get a certain volume level.

he went into a lot more detail, some of which i forgot already, and some i just didn't understand.

Does this make sense to anyone else? this dude is pretty crazy, but usually very on point when it comes to audio. just wondering what others though about this concept, and if if holds any weight, or if it's more of a case of 'better cuz i did it', which wouldn't shock me.

either way, can't wait to hear these speakers in a a few weeks, i've been told they aren't very accurate by todays standards of 'big guys', but they look like they'll be at least entertaining to listen to. any thoughts on the speakers are welcome as well.

Attached files


Member for

19 years 11 months

Davedog Mon, 05/13/2013 - 11:52
Seems his point is a matter of efficiency. Having enough headroom in a system to allow the longer/taller frequecies to develop without a strain on the amplification is why the best set-up is always one with a lot of power....power used efficiently. Some of this, as far as the speakers' power curve, will be the effect of the crossover and its efficiency as well as its points of crossover. A passive speaker like the Urie will have (at some point) have some lossy issues due to the impedance shift through the frequency range. The good news in this case is the array of the speakers and the fact that they are time aligned will compensate for their problems. There are some very good older threads on these most from the R/E/P forum. Of course in this case as in all cases at this level there will conflicting opinions in the 180degree range.

BTW I spent a lot of hours in front of a pair of Urie 809's. The imaging was really good and so was their ability to ROCK. They also begged you to place the mids correctly. They aren't pretty sounding nor would you want to call them modern sounding or really accurate. But, an improvement on the quality of the components can bring them back to working spec easily. They are a learned pleasure.

BTW....One of the posts I referenced said specifically to NEVER use a Macintosh 2500 with the outboard transformer pac. Jus sayin

Member for

12 years 4 months

kmetal Tue, 05/14/2013 - 00:00
cool dave, thanks for shedding some liight! i'll def def check out the threads. i'd like to know all i can before i get to working on these speakers. I think the owner is going to tweak/work on the crossover section, during the repair of the speakers, (one needs to be reconed).

yeah as far as the mcintosh, the owner isn't gonna use that due to budget restraints, and the dude who i was talking to certainly wasn;t a rule follower. certainly noted about the transformer pac.

my feeling is to just leave the room as accurate as possible, and get the speakers sounding as accurate as possible, something just worries me about creating modal boosts in the room, but it's about 30 years too late for that.

:edit: i just did a general search for urei 813, and not much cam up, what's the R/E/P forum? sorry if that's a numbskull question.


Member for

11 years 10 months

bouldersound Tue, 05/14/2013 - 09:55
Getting additional response in a particular frequency range in the room is going to mean more reflections, more interference and less consistency.

All woofers have a lower frequency limit below which they rapidly get inefficient. A well selected HPF keeps away the LF that the speakers can't properly handle and frees up a bunch of power at the frequencies they can reproduce well.

R/E/P is part of

Member for

12 years 4 months

kmetal Wed, 05/15/2013 - 00:21
Getting additional response in a particular frequency range in the room is going to mean more reflections, more interference and less consistency.

yeah thats what i'm worried about...maybe when it comes down to setting up the speakers i can try to weigh in on getting the room to boost less bass, maybe 1 or 2 db instead of 5. thanks for the heads up on prosoundweb