Does your Theater have enough octane?!

[prerich]

Many people are worried about over powering their speakers, well that's not the big worry - especially with HT. I would worry about underpowering them instead - especially if you are trying to produce THX 85db reference levels in your room (with 105db peaks).

I 've use a free SPL calculator developed by Nyal Mellor over at Acoustic Frontiers and just input some hypothetical measurements. A speaker that has a sensitivity of 100db and a person is seated 12 feet away only needs 22 watts of power to reach THX 85db and 43w to reach 105db peaks. A speaker with 90db seated 8 feet away would need a 96w amp for reference and 192w for peaks. A person with an 85db speaker seated 7 feet away would need a wopping 233w amp to achieve reference 85db and a 464w amp to reach 105db peaks!!!!!

It's kinda fun to look at. The tool is located here http://www.acousticfrontiers.com/hom...spl-calculator
(but uses Excel). Check in and see if you may need to give your HT a little boost? However, if you're happy and you know it - stay with what ya got!!!!

[Flatnate]

Originally Posted by prerich

Many people are worried about over powering their speakers, well that's not the big worry - especially with HT. I would worry about underpowering them instead - especially if you are trying to produce THX 85db reference levels in your room (with 105db peaks).

I 've use a free SPL calculator developed by Nyal Mellor over at Acoustic Frontiers and just input some hypothetical measurements. A speaker that has a sensitivity of 100db and a person is seated 12 feet away only needs 22 watts of power to reach THX 85db and 43w to reach 105db peaks. A speaker with 90db seated 8 feet away would need a 96w amp for reference and 192w for peaks. A person with an 85db speaker seated 7 feet away would need a wopping 233w amp to achieve reference 85db and a 464w amp to reach 105db peaks!!!!!

It's kinda fun to look at. The tool is located here http://www.acousticfrontiers.com/hom...spl-calculator
(but uses Excel). Check in and see if you may need to give your HT a little boost? However, if you're happy and you know it - stay with what ya got!!!!

AaaaHaaa! Looks like we are expanding on some of the questions I had yesterday over in the audiophile vs pro monitor thread.

I'm also glad we retouched on what the definition of "THX Reference level" is.

I found two SPL calculators yesterday that I was playing around with.

http://myhometheater.homestead.com/splcalculator.html

as well as

http://www.doctorproaudio.com/doctor...ladores_en.htm.

Both of those calculators gave me a peak SPL of 106.2 on my Mackie HR824 MKII's at listening position of nine feet. Which I would consider to be fairly accurate based on my observations.

The required amplifier calculator says I need 97 watts RMS, and 193 peak to achieve reference level. However, on paper the Mackies have more power than that, so I'm kinda wondering if some efficiency is lost in the way Mackie must EQ them internally at the factory? I ran Audyssey, and let it set the levels. If I turn my pre/pro to "THX Reference" I still get the occasional limiter light come on the left or right speaker. I could probably set the crossover at 85 HZ and that might solve it but I know at these setting and levels I'm right at the limit of my systems dynamic range. I still don't think I could have done much better for the money in terms of power and accuracy.

[prerich]

Originally Posted by Flatnate

AaaaHaaa! Looks like we are expanding on some of the questions I had yesterday over in the audiophile vs pro monitor thread.

I'm also glad we retouched on what the definition of "THX Reference level" is.

I found two SPL calculators yesterday that I was playing around with.

http://myhometheater.homestead.com/splcalculator.html

as well as

http://www.doctorproaudio.com/doctor...ladores_en.htm.

Both of those calculators gave me a peak SPL of 106.2 on my Mackie HR824 MKII's at listening position of nine feet. Which I would consider to be fairly accurate based on my observations.

The required amplifier calculator says I need 97 watts RMS, and 193 peak to achieve reference level. However, on paper the Mackies have more power than that, so I'm kinda wondering if some efficiency is lost in the way Mackie must EQ them internally at the factory? I ran Audyssey, and let it set the levels. If I turn my pre/pro to "THX Reference" I still get the occasional limiter light come on the left or right speaker. I could probably set the crossover at 85 HZ and that might solve it but I know at these setting and levels I'm right at the limit of my systems dynamic range. I still don't think I could have done much better for the money in terms of power and accuracy.

Yep - so your Mackies are 91db efficient . You may try raising the crossover, however - sitting a foot closer would give you more gain at your seat.

[Flatnate]

I also remembered that it uses a 4 ohm bass driver and a 6 ohm high frequency driver. So that is 150 watts in to 4 ohms and 100 watts in to 6 ohms. So, that could make an easy comparison to the "required amplifier needed power" a little trickier as well. It also means "250" watts may not be entirely accurate when being entered in to those SPL calculators as well?

[prerich]

Nate, I can see why you are clipping. I looked up your speakers and they are bi-amped (100w for the high 150w for the lows). I believe your speakers are demaning more power than available for mid and low frequencies. At 8 ft you will right at you limits, but sitting 7 ft away - you will be a happy camper (those speakers are generally made for nearfield monitoring). At 7ft you will only need 117w for 105db peaks. So bring your seat up 2 ft if possible

[prerich]

Originally Posted by Flatnate

I also remembered that it uses a 4 ohm bass driver and a 6 ohm high frequency driver. So that is 150 watts in to 4 ohms and 100 watts in to 6 ohms. So, that could make an easy comparison to the "required amplifier needed power" a little trickier as well. It also means "250" watts may not be entirely accurate when being entered in to those SPL calculators as well?

No, that's not accurate . If it were me - I'd put 100 watts.

[prerich]

Originally Posted by Flatnate

I also remembered that it uses a 4 ohm bass driver and a 6 ohm high frequency driver. So that is 150 watts in to 4 ohms and 100 watts in to 6 ohms. So, that could make an easy comparison to the "required amplifier needed power" a little trickier as well. It also means "250" watts may not be entirely accurate when being entered in to those SPL calculators as well?

My son uses non-powered studio monitors (Bagend M6) that are only 87db efficient and hes 7ft away - however - he uses my old 260w per Yamaha M-80 power amp to drive them. That's not peak power, that's continuious. So he needs 147w for THX 85db and 293w for 105db peaks (his peak power is right around 600w) so he can hit that in his space without distoritng or clipping ...and does.

[Flatnate]

Originally Posted by prerich

No, that's not accurate . If it were me - I'd put 100 watts.

Hmm, ok. I would have thought it would still be more than that based on the specs of the amplifier section on the spec sheet?

http://www.mackie.com/products/hrmk2...4MK2_Specs.pdf

But you're observation does seem quite accurate in terms of observed performance. I however doubt the couch is going anywhere right now. I also never really watch movies at reference level.
.

[prerich]

Originally Posted by Flatnate

Hmm, ok. I would have thought it would still be more than that based on the specs of the amplifier section on the spec sheet?

http://www.mackie.com/products/hrmk2...4MK2_Specs.pdf

But you're observation does seem quite accurate in terms of observed performance. I however doubt the couch is going anywhere right now. I also never really watch movies at reference level.
.

10-4, I'm wondering does the THX pm3 certification only take traditional near field monitoring into consideration (9ft is definitely not considered near-field). I say this because in a near-field setting your speakers will handle it no sweat!

[Flatnate]

Originally Posted by prerich

10-4, I'm wondering does the THX pm3 certification only take traditional near field monitoring into consideration (9ft is definitely not considered near-field). I say this because in a near-field setting your speakers will handle it no sweat!

I did some homework (or at least attempted to at one point) on THX pm3. THX sure won't tell you much as its all proprietary. Anyway, best I can gather is that it is short for "precision multi-channel mixing and monitoring". A fella on another site who seemed to be aligned with a small speaker manufacturer once said (take this with a grain of salt). That pm3 is very similar to the original THX Ultra spec in terms of linearity, off-axis response etc.. but it can't be guaranteed for a specific square footage say xxxx square feet as the amplifier section can vary greatly between various near field monitors.

Me, I'm still trying to wrap my noodle around why despite being bi-amped it still comes out to only 100 watts for the calculator.

[Canada]

My uncle was told a long time ago when he was buying speakers for his car that under powering your speakers will create a lot more problems than over powering them. It's also much easier to do, my 683 B&W can handle 200 watts hell my 685 which is the smallest speaker in B&W 600 range can handle 100 watts.

[prerich]

Originally Posted by Flatnate

I did some homework (or at least attempted to at one point) on THX pm3. THX sure won't tell you much as its all proprietary. Anyway, best I can gather is that it is short for "precision multi-channel mixing and monitoring". A fella on another site who seemed to be aligned with a small speaker manufacturer once said (take this with a grain of salt). That pm3 is very similar to the original THX Ultra spec in terms of linearity, off-axis response etc.. but it can't be guaranteed for a specific square footage say xxxx square feet as the amplifier section can vary greatly between various near field monitors.

Me, I'm still trying to wrap my noodle around why despite being bi-amped it still comes out to only 100 watts for the calculator.

I did a Microsoft on ya Nate!!! Don't let it bug ya, - I used the lowest amp value in your setup as a standard. Your bottom end is a 150 but what you don't do is combine the amp values and say I have 250 watts, what you have is one amp section with 100 and another with 150 powering individual drivers with different impedences at that. I used 100w as a safe generalzation - but it's not 250 watts . You are clipping because of said distance (IMHO) it makes total sense with nearfields. That's why you will see more than one pair of monitors in a setup - some are nearfiled - some are fullfledged floor standers like B&W 802D's or Westlakes! They will use them for different things. I believe the THX PM3 standard is definately for nearfield movie mixing (not distance movie viewing). Just my 2 cents.

[prerich]

Originally Posted by Flatnate

I also remembered that it uses a 4 ohm bass driver and a 6 ohm high frequency driver. So that is 150 watts in to 4 ohms and 100 watts in to 6 ohms. So, that could make an easy comparison to the "required amplifier needed power" a little trickier as well. It also means "250" watts may not be entirely accurate when being entered in to those SPL calculators as well?

You are right. 250 watts is not the number. I also looked at your over all power handling - its 20watts for long term and 50 watts for program.

[prerich]

Originally Posted by Flatnate

I did some homework (or at least attempted to at one point) on THX pm3. THX sure won't tell you much as its all proprietary. Anyway, best I can gather is that it is short for "precision multi-channel mixing and monitoring". A fella on another site who seemed to be aligned with a small speaker manufacturer once said (take this with a grain of salt). That pm3 is very similar to the original THX Ultra spec in terms of linearity, off-axis response etc.. but it can't be guaranteed for a specific square footage say xxxx square feet as the amplifier section can vary greatly between various near field monitors.

Me, I'm still trying to wrap my noodle around why despite being bi-amped it still comes out to only 100 watts for the calculator.

That's your point right there - A THX Ultra spec must fill a very large room, everything comes into play including amp power. The pm3 spec may have similar requirements as far as linearity - but most of the PM3 speakers that I've found are small mini monitors (its like saying I should be able to fill up a room with my Klipsch THX certified computer speakers ... right ). That won't happen. Your speakers are fine - actually very good speakers (got a lot of respect for Mackie). However, to do the job especially at 9 feet - you're going to need something bigger and an amp that will bring the necessary fuel to the race. The PM3 spec ... you would actually need it to ensure that your room, equipment, and everything else conforms to THX PM3 (which was designed for broadcast mixing i.e. a broadcast truck enviornment).

What are you using for room correction? Are your levels calibrated? There are plenty of question (and I know you have a great pre/pro).

[Flatnate]

Originally Posted by prerich

What are you using for room correction? Are your levels calibrated? There are plenty of question (and I know you have a great pre/pro).

So far I have ran Audyssey XT32, but I should really go and verify a few things with the SPL meter.

My hope was that the Mackie would perform like a poor mans Genelec 1031a (also a THX pm3, nearfield monitor). Genelec still sells the 1031b essentially re-branded as the HT208b under their residential home theater line. However close inspection of the specs shows the Genelec would outperform making reference level for that last two feet, where my Mackies just can't quite muster. The line between nearfield and midfield with the pro oriented stuff is pretty fuzzy. Granted the Genelecs I think retail for like $2200 bucks and I paid around $400 for my Mackies. I shouldn't complain but if I found the Genelecs on eBay for a steal..... hrrmmmmm.

Edit: The Genelec HT208B actually is biamped 120 watts for the lows and 120 watts for the highs. Not much better than my Mackie on paper, but they state that it is intended for rooms up to 4200 cubic feet?! That seems like a stretch for what was originally a "nearfield" monitor.

[victortubeman]

Hi Nate,

Do you use a sub? Or running the makie,s full range?

100 watts seems right,max power draw is 150watts per speaker.

[Flatnate]

Originally Posted by victortubeman

Hi Nate,

Do you use a sub? Or running the makie,s full range?

100 watts seems right,max power draw is 150watts per speaker.

I'm running with a single sub, crossover is set at 80 hz. However, I'm running a crappy Cerwin Vega sub (next on the upgrade list), so if I'm not running loud or anywhere near reference level, I find I actually prefer the sound of running them full range. Low frequency output seems a bit snappier and a bit less muddy then.

On the spec sheet Mackie lists the lower frequency power amplifier with 150 watts "rated power output" and 350 watts "burst power output". I'm not sure if "rated" can really be called "RMS" or if "burst power output" can be called "peak". I just know the limiter kicks in only on the most extreme scenes.

I really wouldn't look to upgrade beyond the Mackies unless we buy a house with a truly cavernous/sweet home theater room downstairs (or if I can get a killer deal on say a pair of M&K's or Genelecs).

[prerich]

Originally Posted by Flatnate

So far I have ran Audyssey XT32, but I should really go and verify a few things with the SPL meter.

My hope was that the Mackie would perform like a poor mans Genelec 1031a (also a THX pm3, nearfield monitor). Genelec still sells the 1031b essentially re-branded as the HT208b under their residential home theater line. However close inspection of the specs shows the Genelec would outperform making reference level for that last two feet, where my Mackies just can't quite muster. The line between nearfield and midfield with the pro oriented stuff is pretty fuzzy. Granted the Genelecs I think retail for like $2200 bucks and I paid around $400 for my Mackies. I shouldn't complain but if I found the Genelecs on eBay for a steal..... hrrmmmmm.

Edit: The Genelec HT208B actually is biamped 120 watts for the lows and 120 watts for the highs. Not much better than my Mackie on paper, but they state that it is intended for rooms up to 4200 cubic feet?! That seems like a stretch for what was originally a "nearfield" monitor.

Your differences between the Mackie and the Genlecs are very important:
Mackie 91db sensitive Genlec 100db to 110db adjustable
Mackie amps rated into 6 and 4ohm. Genlec both rated into 8ohm
You are right, the Genlec is another animal, it is easier to drive, more efficient, it's a better overall powered speaker.

[prerich]

Originally Posted by Flatnate

I'm running with a single sub, crossover is set at 80 hz. However, I'm running a crappy Cerwin Vega sub (next on the upgrade list), so if I'm not running loud or anywhere near reference level, I find I actually prefer the sound of running them full range. Low frequency output seems a bit snappier and a bit less muddy then.

On the spec sheet Mackie lists the lower frequency power amplifier with 150 watts "rated power output" and 350 watts "burst power output". I'm not sure if "rated" can really be called "RMS" or if "burst power output" can be called "peak". I just know the limiter kicks in only on the most extreme scenes.

I really wouldn't look to upgrade beyond the Mackies unless we buy a house with a truly cavernous/sweet home theater room downstairs (or if I can get a killer deal on say a pair of M&K's or Genelecs).

If that's where the limiter kicks in....that's the problem, no enough juice for what you want to produce (at least not at your main seat).

[Flatnate]

So many upgrades before I worry about doing anything with the Mackies. Thinking of an SVS sub next, followed by an acoustically transparent screen once we move, then possibly an anamorphic lens or a projector with a zoom lens memory. That said, if I move to a bigger room and then find the Genelecs that I have the hots for on the cheap I may pull the trigger.

Don't get me wrong I really like the Mackies. I never watch movies near the levels we are talking about, and the clarity I'm getting is nothing short of amazing. I got in to them for so cheap that the amount I may need to spend to really offer a compelling upgrade is probably on the magnitude of two to three times what I'm in so far.