The Effects of Qts on Low end extension in Vented Alignments

[sundownz Pro Seller]

Not really valid...at all.
You can't just shift Qts...

"To every action there is an equal and opposite reaction."

If you shift Qts, Bl changes...Fs changes..response changes...

Just a fyi //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Indeed.

 

[ciaonzo 5,000+ posts]

I think what has happened is this is out of context slightly as audio phill was just trying to illustrate something for me by quickly altering only the Qts to drive home a point he was making in a PM we shared earlier. Both of you gentlemen are correct in your statements, not that you needed me to verify that. I'm not sure how this came to public view though. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

While reading this please consider that I am not an authority on anything, just a hobbyist. If you disagree, that's perfectly alright. Sometimes it takes an open mind and another person's input to gain a perspective that you didn't have prior to the discussion at hand. We all like different things, that's the way it should be. Let's keep it friendly. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

For the topic I'll state that I deal with mostly home audio suited for music and very rarely build vented enclosures. I mainly build transmission lines but sometimes the odd sealed enclosure here and there. My personal preference for Qtc in the home environment is in the neighborhood of .577 to .65. Among other desirable attributes, I find this allows for easy placement when paired with the room's transfer function without getting thick or boomy. On the rare occasion I do build a vented enclosure, I design it to mimic the roll-off of a sealed enclosure with a Qtc of .65. In other words, it's highly damped. These types of enclosures are not for high power handling, nothing I design ever is. Excursion is always the limiting factor in my alignments by design. I've long preferred highly damped systems with a very mellow Q and have never liked the sound of high Qts drivers with a high Fs, especially when they are forced into vented alignments. Again, this is a personal preference. I'm not suggesting that anyone who designs systems like that which are meant for high power SPL purposes are doing anything wrong. My efforts are to reproduce the smoothest, deepest, low frequency response from whatever driver it may be at the expense of displacement-limited output. That's not to say that the things I build don't get loud, many of them do. I just place character-free playback at the top of my list of priorities.

In the car environment however, an alignment with a Qtc of .577 is not likely to be desirable unless very specific precautions are taken up front to have authority in the midbass (I usually use 8' or 10's up front) due to the lack of impact an alignment like that would appear to have being so efficient in the subsonic region due to the transfer function of the vehicle. So I can see why some alignments find their way into some vehicles. I detest boomy bass with a lack of definition and extension. ANYONE can make something loud. Not everyone can make it sound good. I shoot for a Qtc of .65 in the vehicle as well, whether it's a straight sealed enclosure, a vented enclosure designed to mimic a sealed enclosure with a Qtc of .65 (very damped), or a transmission line (the ultimate in low frequency extension). TL's take up lots of real estate so they're not always practical to implement. Many are surprised to see such small drivers digging so low in frequency that they forget all about how loud they wanted it to be. The power of psychoacoustics should never be underestimated and you should manipulate it whenever possible.

I hope I didn't put anyone to sleep with all that babbling. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[audio_phill 10+ year member]

Does anyone know the formula for turning TSP's into EBP? I'd like to look at how each parameter affects the freq response independantly to add more validity to the topic. I'm sure their some where online or in a loud speaker cookbook but everything I've seen so far isn't as technical as I'd like.

 

[mrogowski 5,000+ posts]

I think what has happened is this is out of context slightly as audio phill was just trying to illustrate something for me by quickly altering only the Qts to drive home a point he was making in a PM we shared earlier. Both of you gentlemen are correct in your statements, not that you needed me to verify that. I'm not sure how this came to public view though. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
While reading this please consider that I am not an authority on anything, just a hobbyist. If you disagree, that's perfectly alright. Sometimes it takes an open mind and another person's input to gain a perspective that you didn't have prior to the discussion at hand. We all like different things, that's the way it should be. Let's keep it friendly. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

For the topic I'll state that I deal with mostly home audio suited for music and very rarely build vented enclosures. I mainly build transmission lines but sometimes the odd sealed enclosure here and there. My personal preference for Qtc in the home environment is in the neighborhood of .577 to .65. Among other desirable attributes, I find this allows for easy placement when paired with the room's transfer function without getting thick or boomy. On the rare occasion I do build a vented enclosure, I design it to mimic the roll-off of a sealed enclosure with a Qtc of .65. In other words, it's highly damped. These types of enclosures are not for high power handling, nothing I design ever is. Excursion is always the limiting factor in my alignments by design. I've long preferred highly damped systems with a very mellow Q and have never liked the sound of high Qts drivers with a high Fs, especially when they are forced into vented alignments. Again, this is a personal preference. I'm not suggesting that anyone who designs systems like that which are meant for high power SPL purposes are doing anything wrong. My efforts are to reproduce the smoothest, deepest, low frequency response from whatever driver it may be at the expense of displacement-limited output. That's not to say that the things I build don't get loud, many of them do. I just place character-free playback at the top of my list of priorities.

In the car environment however, an alignment with a Qtc of .577 is not likely to be desirable unless very specific precautions are taken up front to have authority in the midbass (I usually use 8' or 10's up front) due to the lack of impact an alignment like that would appear to have being so efficient in the subsonic region due to the transfer function of the vehicle. So I can see why some alignments find their way into some vehicles. I detest boomy bass with a lack of definition and extension. ANYONE can make something loud. Not everyone can make it sound good. I shoot for a Qtc of .65 in the vehicle as well, whether it's a straight sealed enclosure, a vented enclosure designed to mimic a sealed enclosure with a Qtc of .65 (very damped), or a transmission line (the ultimate in low frequency extension). TL's take up lots of real estate so they're not always practical to implement. Many are surprised to see such small drivers digging so low in frequency that they forget all about how loud they wanted it to be. The power of psychoacoustics should never be underestimated and you should manipulate it whenever possible.

I hope I didn't put anyone to sleep with all that babbling. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

Cliffs?

 

[PaulD 10+ year member]

cliff .... he prefers ported boxes that sound similar to sealed. Other than that, this is pretty much a useless thread

 

[mrogowski 5,000+ posts]

Oh.

 

[squeak9798 5,000+ posts]

Does anyone know the formula for turning TSP's into EBP? I'd like to look at how each parameter affects the freq response independantly to add more validity to the topic. I'm sure their some where online or in a loud speaker cookbook but everything I've seen so far isn't as technical as I'd like.

http://en.wikipedia.org/wiki/Thiele/Small