THX and Amps

[Reorx]

With amps...What is the difference between THX certified, THX approved, and non THX?

Is a Ashly FTX 2001 any good?
Ashly amp link

Reorx

 

[forumtroll]

A THX amp is supposed to deliver a certain amount of power into 3.2 ohms. What that number is I don't know. I not sure the ohm limit a THX speaker is allowed to drop down to. I'm about 95% sure it's its 3.8 ohms at any given frequency but then again rating the amps with a 3.2 ohm load then wouldn't make sense so, it's either 3.8 or 3.2 ohms. If the amp doesn’t deliver the THX spec then you can take that matter up with THX.

 

[MDS]

THX certified means the amp was submitted to THX for evaluation and in the opinion of THX it meets their criteria and may use the THX logo. The criteria are not public but some of them are known from various articles and interviews over the years. Audioholics had an article a few years ago that is probably still available if you search for it.

If I remember correctly, the minimum impedance is 3.2 ohms as forumtroll suggested and the amp must have a minimum 40V rail voltage and be able to output at least 50 wpc all channels driven. There are other criteria that are not secret, like the requirement for 4th order lowpass, 2nd order high pass for bass management. The color coding for each channel also came from THX.

I don't think 'THX approved' is an official certification. I could be wrong, but I bet that is marketing speak. It's akin to saying 'our amp meets THX specs and we follow the THX guidelines, but we haven't bothered to pay for an actual certification'.

Non-THX receivers are simply those that are not certified and don't make any claims that they would pass certification were they to submit it to THX for evaluation. Note that there are many receivers and amps that are not certified but would pass if they were submitted for evaluation. The only thing you can be absolutely certain of with a non-THX certified amp is that it will not include the THX post processing routines (adaptive decorrelation, timbre matching, etc).

 

[forumtroll]

THX certification is great if you’re just interested hooking everything up and having everything work. You’ll be guaranteed 85 spl for dialogue and 21 spl for dynamic head room.

While it may be true many speakers will qualify for THX certification, there are just as many that won’t.

My only word of advice…stay away from any speaker/subwoofer that is front ported. The bass will always be out of phase. The woofer will push out rather than in. Rear ported speakers are better, but still always out of phase but just slightly because air has elasticity. However, a rear port will have the woofer push in as supposed to.

 

[tbewick]

Forumtroll, I don't really know very much about speaker design, but I have seen very good speakers the use front-ported designs.

The top-end Tannoy studio monitor, the System 215 DMT, appears to have a front ported design (see www.tannoy.com). The enclosure is described as 'Optimised bass-reflex loaded', and the speaker has a distortion rating of 0.5%. Many other high-quality speaker manufacturers use front-ported designs.

Maybe there's a way of designing the speaker so that this out of phase effect is inaudible/insignificant?

 

[Buckeyefan 1]

A THX amp is supposed to deliver a certain amount of power into 3.2 ohms. What that number is I don't know. I not sure the ohm limit a THX speaker is allowed to drop down to. I'm about 95% sure it's its 3.8 ohms at any given frequency but then again rating the amps with a 3.2 ohm load then wouldn't make sense so, it's either 3.8 or 3.2 ohms. If the amp doesn’t deliver the THX spec then you can take that matter up with THX.

This was taken from the THX website.
THX Certified Amplifiers are designed to drive the speaker systems to cinema-quality sound levels in home environments with no distortion. Before being awarded certification, amplifiers are tested for frequency response, distortion, power output, and stability. THX Certified amps share a common input sensitivity and gain structure with a wide variety of controllers and speakers to insure optimum compatibility. In systems with eight or more amps these standards guarantee that the system will have the lowest level of unwanted amplifier hiss and noise while achieving the maximum possible headroom. In short, they're really quiet but play really loud.

Amplifiers, Equalizers and Interconnects
All audio components in a home theater system can color the sound. In more complex audio system, like multi-channel THX Home Theater systems, there’s higher risk of colorations and distortions that can degrade sound quality. Products with THX certification protect against these risks. THX Certified components are designed and tested to meet THX specifications for minimal noise, distortion, and frequency response errors. To ensure continual compliance, THX Ltd. engineers personally subject a sample of each component category to after-market testing to confirm adherence to all performance standards.

THX Select and Ultra2 Certified Products offer these qualities
Qualities Faithful sound reproduction.
Re-EqualizationTM removes the edgy "brightness" of cinema sound, accurately adapting movie sound for home playback.
Timbre MatchingTM ensures a tonal match between front and surround speakers for smooth sound movement.

Surround-sound spaciousness.
Adaptive DecorrelationTM manages Mono Surround signals for a true stereo feel.

Wide dynamic range with massive, distortion-free bass.
Bass ManagementTM sends bass to subwoofers, delivering cinema-quality bass and allowing for smaller, easier-to-place speakers
Bass Peak Level ManagerTM protects subwoofers from overload, ensuring trouble-free delivery of bass-heavy soundtracks.

Optimum listening throughout the room.
Loudspeaker Position Time SynchronizationTM lets you set up your system for optimal "sweet-spot" listening anywhere in large or space-constrained rooms.

Quick and easy set-up.
Guaranteed swift and seamless setup across all THX brands and components.

 

[forumtroll]

A port NEVER belongs in the front. Porting in the rear is okay, but porting introduces a whole new set of problems. That isn't to say rear porting is a bad thing. Like everything else, it just has to be done well.

There are indeed a lot of high end speakers that front port. Many of those companies I wouldn't consider high end. It's not about price. Many people mock Bose (with good reason) but don't mock companies that use front porting.

Many of those high end speakers charge way too much for the product they deliver.

It's a personal thing. There are people who like the way distortion and port noise sound and associate it with bass. There's a difference between accuracy and precision.

I like accuracy, whether I like what is coming out is a different beast.

I don't what the post to turn into a huge flame war. I'm just posting facts. If you want bang for the buck--check out M&K speakers. ( www.mksound.com ) most major studios use M&K. I bought a 750 system minus the sub. I went with definitive technology's SuperCube I for the sub; however my dealer is willing to refund my SuperCube 100% towards credit towards an M&K 350 subwoofer. I'm very tempted to do it. It's just that I've spent a lot of money on audio equipment as it where already.

I guess what I'm saying is that for the price of Bose or Paradigm you can get M&K and the sound will be true as mixed (assuming the room is good). I have a bias. I've mentioned it--accuracy. I also like to support the local economy (there located 8 miles from my house in the porn capital of the world Chatsworth CA).

 

[MDS]

A port NEVER belongs in the front. Porting in the rear is okay, but porting introduces a whole new set of problems. That isn't to say rear porting is a bad thing. Like everything else, it just has to be done well.
...
It's a personal thing. There are people who like the way distortion and port noise sound and associate it with bass. There's a difference between accuracy and precision.

I don't what the post to turn into a huge flame war. I'm just posting facts. I guess what I'm saying is that for the price of Bose or Paradigm you can get M&K and the sound will be true as mixed (assuming the room is good).

You are not posting facts - you are posting your opinion. You basically state that only M&K speakers reproduce the sound 'accurately as mixed'; as if no other speaker could do the same and no speaker with a front port could ever be as good. That is just not true. There are dozens of variables that go into speaker design and ported vs sealed is just ONE of them.

...and Accuracy and Precision ARE the same thing. If something is not accurate, how could it be precise? Accuracy implies strict adherence to a tolerance as does precision.

 

[dillweed]

Seems like this question is asked every month.

I recommend you do a search. Here is a link on me.

http://forums.audioholics.com/forums/showthread.php?t=8088&highlight=THX

 

[forumtroll]

You’re reading too much into my post. I never said M&K are the only speakers able to produce accurate speakers. However, they are capable to doing it. That’s it.

Accuracy and precision is not the same thing.

Precision implies something is able to reproduce something over and over. For example, during a bass sweep speakers A always have a dip between 32 Hz and 22 Hz of -6dB. This is precision. It always does it. These speakers are precise.

Accuracy is the true measurement as indented. Example, you design a speaker to be flat with a deviation of ±2 dB and that speaker only has a ±2 dB deviation as intentioned. No dips or unexpected deviations. If they are to reproduce the deviation of ±2 dB more than once time after time then would also be precise. They are related terms but don’t mean the same thing.

Ports still don’t belong in the front of a speaker.

If you like the way a speaker with a front port sounds then that is a different thing. They’re just not accurate. But if you like it, then it’s okay. Personally I don’t.

 

[MDS]

You’re reading too much into my post. I never said M&K are the only speakers able to produce accurate speakers. However, they are capable to doing it. That’s it.

I guess what I'm saying is that for the price of Bose or Paradigm you can get M&K and the sound will be true as mixed (assuming the room is good). I have a bias. I've mentioned it--accuracy.

That is exactly what you said. M&K sound will be 'true as mixed' and Paradigm won't, so for the same money buy M&K. If you prefer M&K for whatever reason, so be it but you are not 'stating facts'. You have brand loyalty and nothing more.

My only word of advice…stay away from any speaker/subwoofer that is front ported. The bass will always be out of phase. The woofer will push out rather than in. Rear ported speakers are better, but still always out of phase but just slightly because air has elasticity. However, a rear port will have the woofer push in.

So the port determines which way the woofer moves? The woofer moves in response to the musical signal. Unless you flip the phase switch on the sub to 180, the woofer will move in when the other speakers move in and out when the other speakers move out.

Accuracy and precision is not the same thing.
Precision implies something is able to reproduce something over and over. For example, during a bass sweep speakers A always have a dip between 32 Hz and 22 Hz of -6dB. This is precision. It always does it. These speakers are precise.

No, that says those speakers are down 6 dB between 22 and 32 Hz. Every time you play the same sweep you will get the same response. If speaker B is down only 3 dB between 22 and 32 Hz, it too will give that exact same frequency response each time you play the sweep. So by your definition, they are both 'precise' and for that matter all speakers are precise because every speaker will behave the same as it did the last time if you run a sweep over and over.

6 dB down is not precise by any stretch of the imagination. 0 dB down would be truly precise and you won't find any speaker that can do that.

Accuracy is the true measurement as indented. Example, you design a speaker to be flat with a deviation of ±2 dB and that speaker only has a ±2 dB deviation as intentioned. No dips or unexpected deviations. If they are to reproduce the deviation of ±2 dB more than once time after time then would also be precise. They are related terms but don’t mean the same thing.

Play the same tone or the same music and you will get the same response each and every time. The only thing that can change that are environmental factors such as room acoustics - move the speaker an inch and it might change a bit. All speakers strive to be accurate; none truly are.

Ports still don’t belong in the front of a speaker.

Your opinion, which based on your prior statements of 'facts' means little.

 

[forumtroll]

WOW.

Let me address those one at a time.

The paradigm/bose thing. All I meant to say was for the same price can buy m&k speakers. Implying they don’t cost more than the competition. The true as mixed was implied to mean that the majorities of movies/music is mixed on m&k speakers, and there for would sound close if not exactly the same as mixed because you’re using the same speakers (if not the same exact speaker then, at least the crossovers and tweeters if you have a THX system).

The port does determine which way the woofer pushes. The woofer pushes towards the front with a front port and back with a back port. In a sealed system the woofer pushes back or inside the cabinet.

Yes you understood what precise means. Repeatable.

0dB down would be an accurate speaker, but if your speaker was only able to do it once then it wouldn’t be precise.

From your post I know you’re not in design or manufacturing because you would understand the difference. It’s like the difference between these numbers:

7 inches
7.00 inches
7.000 inches and
7.0000 inches

each measurement implies a difference level of accuracy. One to the tenths, one to the hundredths, and the other to thousandths, but you then have to take into account the least significant number (it’s a long post if I continue).

If you don’t believe me, please take the time to research before posting. You understood the concepts I was typing. You just don’t want to believe me.

My background is in design, with some aerospace experience (JPL in Pasadena).

Again, ports still don't belong in the front.

 

[Buckeyefan 1]

Troll,

You do realize most front ports (ports in general) have tubes extending into the rear of the speaker. Higher end speakers may also contain "cavities" (almost a simple labrynth) to channel higher pressue out the ports. Making a statement that ports don't belong in the front is a little misdirected unless you are assuming this port is a simple hole, which is rarely if ever an issue. A woofer will move in the same direction whether the port and tube extends front to back, or back to front (unless of course you've swithed the polarity of the speaker cable). If you can hear the air coming out of a front port as opposed to a rear port, then your ears are better than 99.9% of everyone on the forum.

 

[MacManNM]

WOW.

Let me address those one at a time.

The paradigm/bose thing. All I meant to say was for the same price can buy m&k speakers. Implying they don’t cost more than the competition. The true as mixed was implied to mean that the majorities of movies/music is mixed on m&k speakers, and there for would sound close if not exactly the same as mixed because you’re using the same speakers (if not the same exact speaker then, at least the crossovers and tweeters if you have a THX system).

The port does determine which way the woofer pushes. The woofer pushes towards the front with a front port and back with a back port. In a sealed system the woofer pushes back or inside the cabinet.

Yes you understood what precise means. Repeatable.

0dB down would be an accurate speaker, but if your speaker was only able to do it once then it wouldn’t be precise.

From your post I know you’re not in design or manufacturing because you would understand the difference. It’s like the difference between these numbers:

7 inches
7.00 inches
7.000 inches and
7.0000 inches

each measurement implies a difference level of accuracy. One to the tenths, one to the hundredths, and the other to thousandths, but you then have to take into account the least significant number (it’s a long post if I continue).

If you don’t believe me, please take the time to research before posting. You understood the concepts I was typing. You just don’t want to believe me.

My background is in design, with some aerospace experience (JPL in Pasadena).

Again, ports still don't belong in the front.

I think what you mean to say is that front ports and rear ports are phased matched with the woofer, such that a front firing woofer/port combo, the bass will be in phase as not to cancel any sound, or a rear port will be phase matched for the same reason.

Ports don't belong on good speakers. Acoustic suspension or passive radiator designs are superior.

 

[MDS]

From your post I know you’re not in design or manufacturing because you would understand the difference. It’s like the difference between these numbers:

7 inches
7.00 inches
7.000 inches and
7.0000 inches

each measurement implies a difference level of accuracy. One to the tenths, one to the hundredths, and the other to thousandths, but you then have to take into account the least significant number (it’s a long post if I continue).

7 = 7.00 = 7.000 = 7.0000. Your credibility is shot. Keep trollin'

 

[Reorx]

lol, damn thread hijackers.
Thank you all who posted about THX and amps.

7 = 7.00 = 7.000 = 7.0000. Your credibility is shot. Keep trollin' - MDS

Not completely true...
significant number's

Yes, I know this is a chemistry link, ignore that, it is actually for all sciences, and engineering. AND it is extremely important when doing calculations. I have seen calculations off by as much as 50% because of ignorance of significant numbers.

Reorx

 

[MDS]

Rounding down to whole numbers as speaker specs are:

7 = 7.0
7.0 = 7.04
7.00 = 7.004

So yes 7 = 7.0 = 7.00.

So what? That's a statement about the accuracy of the measuring equipment and says nothing about whether the speaker is accurate or precise. No speaker is accurate or precise by the definitions given above.

 

[Buckeyefan 1]

I think what you mean to say is that front ports and rear ports are phased matched with the woofer, such that a front firing woofer/port combo, the bass will be in phase as not to cancel any sound, or a rear port will be phase matched for the same reason.

Ports don't belong on good speakers. Acoustic suspension or passive radiator designs are superior.

Here's the low down on ports, if anyone cares.
Ports sacrifice accuracy.
There is ~6 db/oct rolloff with a sealed enclosure
Without a port, use a top notch crossover, and a ton of power, to make up for the efficiency loss.
Manufacturers don't want to sell speakers at a premium, expecting consumers to have adequate power, so they use ports.

 

[forumtroll]

I don't know if this is true for other manufactures, but M&K uses a 12 dB/octave Linkwitz-Riley crossover for there sat+sub systems. The total roll off would end up closer to 24dB/octave.

M&K does have two models that are ported (rear) that when open produce a total roll off closer to 12dB/octave, which is why if you decide to use a subwoofer with those two particular models you must seal the speaker with the foam plug to achieve the desired 24dB/octave with a sat+sub system.

Again, it's dependant on crossover design. M&K follow THX suggestions.

MDS don't underestimate least significant number. It's VERY important in engineering as it's directly related to cost. Accuracy costs $$$.