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Subwoofer Ownership – Your Path to Satisfaction - Page 12

post #331 of 663
On other notes I just discovered that data-bass site. Pretty cool to have numbers next to each other like that. And some cool articles to check out as well!
post #332 of 663
Quote:
Originally Posted by jlpowell84 View Post

On other notes I just discovered that data-bass site. Pretty cool to have numbers next to each other like that. And some cool articles to check out as well!

Yeah it's a great site, we like to use it all the time. You can also click on each sub and come up with more. smile.gif
post #333 of 663
Thread Starter 
I was a member at the shack for awhile, but I felt like every other day a moderator Nazi was sending me a PM telling me I hurt someone's feelings or something. Literally over the smallest things... It's like HTS is Rated G and AVS is Rated PG-13.

I got sick of it, made my thoughts public and cut ties.

Whatever... I'll never bash HTS. They are a smaller community comprised of many many AVSers and there is a lot of great info on the site.

Just wasn't a good fit for me personally.
post #334 of 663
Hey guys. Have been doing lots of thread reviewing. Lots of interesting debates in the JTR cap threads. What exactly is a port tuning? Port size, length of port, and enclosure size? I read Archea had a couple Cap pros tuned at 15 hz. Did he have Jeff custom make a port tune?
post #335 of 663
Quote:
Originally Posted by jlpowell84 View Post

Hey guys. Have been doing lots of thread reviewing. Lots of interesting debates in the JTR cap threads. What exactly is a port tuning? Port size, length of port, and enclosure size? I read Archea had a couple Cap pros tuned at 15 hz. Did he have Jeff custom make a port tune?

Taken off of site> Ported enclosures are distinguished by a vent or duct in the structure. This vent allows the rear sound wave of the woofer to interact with the front sound wave. The coupling of a vent to the air inside the enclosure reinforces the low-frequency response of the subwoofer system and can greatly increase the efficiency. By changing either the length or surface area of the port, the resistance to motion of the column of air within the port changes its resonant characteristics, thus causing the tuning frequency of the enclosure to change. Over



One always has a certain set of perimeters to work within considering port tune. You can be sure when the Cap was modeled and tested they worked within certain boundaries and made their decisions according to what they were trying to achieve. The driver, size of the enclosure and port size all come into play when determining.
post #336 of 663
Quote:
Originally Posted by jlpowell84 View Post

Hey guys. Have been doing lots of thread reviewing. Lots of interesting debates in the JTR cap threads. What exactly is a port tuning? Port size, length of port, and enclosure size? I read Archea had a couple Cap pros tuned at 15 hz. Did he have Jeff custom make a port tune?

Every driver has T/S parameters and two of the most important are QTS and FS. QTS is one of the major factors that will help determine whether or not a driver is suitable for a closed box or a vented box and FS is the resonance frequency of the driver. The resonance frequency is the frequency at which the driver naturally vibrates and so requires little power and on an impedance graph is also where the impedance is lowest. Porting a subwoofer will create a new resonance frequency for the box where the driver is moving at a minimum, but air through the vent is at a maximum. So the subwoofer pumps back and forth, which causes the air inside the cabinet to vibrate. Since the cabinet is now ported air will be pushed and pulled through the port at the same time. The box tuning will be determined by the T/S parameters, the box size, the vent volume which is where the length and volume of the port comes into play. Now the port is really just a holder for a certain volume of air that can be achieved in multiple ways as long as the volume of air is unchanged. This is can mean a narrow and long port, multiple wide and short ports, a slot port with a a 90 degree turn or whatever else you can dream up. The key is keeping the vent air velocity below 10% the speed of sound, although lower certainly isn't a bad thing.

So that's kind of the medium length explanation on top of what steve said.
post #337 of 663
Quote:
Taken off of site> Ported enclosures are distinguished by a vent or duct in the structure. This vent allows the rear sound wave of the woofer to interact with the front sound wave. The coupling of a vent to the air inside the enclosure reinforces the low-frequency response of the subwoofer system and can greatly increase the efficiency. By changing either the length or surface area of the port, the resistance to motion of the column of air within the port changes its resonant characteristics, thus causing the tuning frequency of the enclosure to change.

This is not what happens in a ported enclosure.


You have mentioned elements of the physics involved. But not the function of the physics involved.

A simple point as an example.

No front wave rear wave interaction through the port.

Simply a function of air pressure difference. The front of the woofer cone has essentially an infinity large box it is driving into. Low pressure side, compared to the rear of the cone. Much smaller enclosure side, or high pressure side.

The ports only contribute to the output of the driver very close to their tuning frequency.

No real increase in efficiency, just a tradeoff as to possible bandwidth of frequencies that you can produce.

There is no free lunch. A ported enclosure drops off at the rate of 24 decibels per octave. An octave is a halving or a doubling of frequency. 20 to 40 hertz is an octave. 16 to 32 hertz is an octave.

A sealed enclosure drops off after the box system resonant frequency at 12 decibels per octave. There is appreciable much below the system resonant frequency. And he cone is well behaved as the internal box volume when correctly sized acts like a spring keeping the driver from uncontrolled motion.

A vented enclosure has very little output below the system tuning, and wildly uncontrolled cone motion if you try to drive it much below the tuning frequency. It is simply a little bit more efficient near this tuning frequency than a similarly tuned sealed box. Normally it is about 3 db more efficient near the tuning frequency only.

The tuning frequency is directly linked to three things.

Volume of air the port is sitting in. The woofer enclosure.

Cross sectional surface area of the port.

Length of the port.

For a given tuning frequency versus box size, keeping the area of the cross section constant.

The larger the box size the shorter the length to get the same tuning frequency.

There is much more that could be said.

And I'm not trying to bash you over the head with this.

It's just that from time to time I read things that are worded in such a way that they appear to make sense. There is a degree of technical jargon that looks right.

But that's the end of it.

They don't make sense.
post #338 of 663
Questions about xmax of subs. If a sub is rated at 30 or 38 xmax...what percentage of that excursion is a percent you wouldn't want to go over? 75%? It just seems you wouldn't want to hit those limits right? Distortion or possible woofer damage perhaps? I found the piston excursion calculator link on the JTR Captivator thread and it has my wheels turning
post #339 of 663
This is why we want subs tested. You never know how a sub may perform based on specs.
post #340 of 663
Quote:
Questions about xmax of subs. If a sub is rated at 30 or 38 xmax...what percentage of that excursion is a percent you wouldn't want to go over? 75%? It just seems you wouldn't want to hit those limits right? Distortion or possible woofer damage perhaps?

There are usually two numbers that mean something if they are honestly stated. They do not describe the same thing.

X-max

X-mech

X-max is the point at where the driver will start to distort if it is driven much more. The generally accepted rule is this number should be stated at 10% distortion THD level and the actual excursion point you get.

X=mech is the number where if you try to push more power into the driver you will smoke it. As it shredded woofer. It will rip apart if this number is exceeded.

Do not try to exceed this number.

Saddest part about X-max is that it has become a smoke and mirrors numbers game.

Over the years I have done test and measurement on a whole bunch of woofers for many clients.

Very few have honestly reported numbers.

The companies I work with and design for have real numbers.

Companies that I have left have dropped off the deep end, or they never wanted to address the falsification.


Mark
post #341 of 663
Quote:
Originally Posted by mwmkravchenko View Post

There are usually two numbers that mean something if they are honestly stated. They do not describe the same thing.

X-max

X-mech

X-max is the point at where the driver will start to distort if it is driven much more. The generally accepted rule is this number should be stated at 10% distortion THD level and the actual excursion point you get.

X=mech is the number where if you try to push more power into the driver you will smoke it. As it shredded woofer. It will rip apart if this number is exceeded.

Do not try to exceed this number.

Saddest part about X-max is that it has become a smoke and mirrors numbers game.

Over the years I have done test and measurement on a whole bunch of woofers for many clients.

Very few have honestly reported numbers.

The companies I work with and design for have real numbers.

Companies that I have left have dropped off the deep end, or they never wanted to address the falsification.


Mark

Very interesting..
post #342 of 663
Just the plain unvarnished truth.
post #343 of 663
Quote:
Originally Posted by mwmkravchenko View Post

Just the plain unvarnished truth.

I don’t doubt you..
post #344 of 663
Thread Starter 
Quote:
Originally Posted by jlpowell84 View Post

Questions about xmax of subs. If a sub is rated at 30 or 38 xmax...what percentage of that excursion is a percent you wouldn't want to go over? 75%? It just seems you wouldn't want to hit those limits right? Distortion or possible woofer damage perhaps? I found the piston excursion calculator link on the JTR Captivator thread and it has my wheels turning

Don't think I've seen that link....?
post #345 of 663
Quote:
Originally Posted by popalock View Post

Don't think I've seen that link....?

Probably this one:
http://www.baudline.com/erik/bass/xmaxer.html
Note at the top that the calculator is only applicable for a sealed or IB subwoofer.
post #346 of 663
Quote:
Originally Posted by mwmkravchenko View Post

Just the plain unvarnished truth.

So can you tell us which ones are true?
post #347 of 663
We got guys on the definitive technology speaker forum having the revelation that the powered towers, 10 or 12 inch subs with 300 or 455 watt amps, can't play down to 18hz as DT claims. There was a graph posted of a steep roll of at 35hz...
post #348 of 663
Thread Starter 
Quote:
Originally Posted by jlpowell84 View Post

We got guys on the definitive technology speaker forum having the revelation that the powered towers, 10 or 12 inch subs with 300 or 455 watt amps, can't play down to 18hz as DT claims. There was a graph posted of a steep roll of at 35hz...

Ha... Here are the specs for my old DefTech reference:

http://www.definitivetech.com/products/supercube-reference

Yeah...11-200Hz "response." In the overview it states "effortless" extension down to 11Hz.

Here is the actual in room response. Such exaggeration turned me off permanently from ALL of Deftech's products.
DefinitiveTechnologySupercubeReference_zpsf4230e1a.jpg

Send your DefTech friends over this way...

tongue.gif
post #349 of 663
^wow! I feel bad for the company but information like this needs to be revealed. I honestly feel a slight angered feeling at these false advertisements then charging 1900 for that? C'mon people work for their money
post #350 of 663
My first sub was a DefTech ProSub 200TL: 250W, 18-150Hz. Nice sub.

When I had a chance to demo an Energy S10.3 - 200W RMS, 21Hz @ -3dB - I was surprised at how much deeper it went (and how much more cleanly it played).

I contacted DefTech, and found out that the 200TL was actually rated to 26Hz @ -3dB. That explained it.
post #351 of 663
It's masked extortion if we are really honest. Falsifying claims for people's money? And twice, or more, times as much for a product that has cheaper parts? I bet their GP is at least double or more than that of JTR products.
post #352 of 663
My path ended abruptly when i got a Paradigm Reference Servo-15 v.2 that stayed behind even after I got rid of the 100s in favor of a Signature S8 mismatched(v.1,2,3 basically whatever was on Audiogon/Canuckaudiomart to complete the 7.1 at the time) system.

I only allow native signal with a minumum of processing, no LFE on any channel, so mostly my sub handles the 0.1 off SACDs and off DTS-HDMA as my fronts are very competent in the LFE dept.

Never been a headbanger tattoed post-campestral urbanite type, but I do enjoy some heavy metal, Black Sabbath a favorite among other Universal Japan SACD titles.

I loathe compressed music except when i stream WDA1 off my Roku M2000 during the morning workout (basement doubles up as exercise area too).
post #353 of 663
Servo-15 v2: A great sub. cool.gif
post #354 of 663
Quote:
Originally Posted by jlpowell84 View Post

It's masked extortion if we are really honest. Falsifying claims for people's money? And twice, or more, times as much for a product that has cheaper parts? I bet their GP is at least double or more than that of JTR products.

It's not extortion, it's just plain old fraud. Extortion would be if some Deftech sales reps came to your house, grabbed you by the collar and said, "You better buy our subs or else you might have a 'nasty accident'".
post #355 of 663
Quote:
Originally Posted by shadyJ View Post

It's not extortion, it's just plain old fraud. Extortion would be if some Deftech sales reps came to your house, grabbed you by the collar and said, "You better buy our subs or else you might have a 'nasty accident'".

Yes. And you know I don't think their stuff is trash. Surely it's not Bose status but much better. I would really like to keep my DT 8060 towers for an area that won't be my dedicated setup. They offer decent sound and bass for music in a 1 cubic ft footprint. But I'm heading toward a JTR setup and that requires funds to raise.
post #356 of 663
Thread Starter 
Quote:
Originally Posted by jlpowell84 View Post

^wow! I feel bad for the company but information like this needs to be revealed. I honestly feel a slight angered feeling at these false advertisements then charging 1900 for that? C'mon people work for their money

Don't feel bad for them. It would be great if information such as this actually started effecting their bottomline. It would force them to adapt (be honest) or fail.

They, like some other companies, play on the ignorance of their target market. Honestly, how may response graphs have you seen on the DefTech thread? How many owners of DefTech products do you think have truly heard "effortless" response down to 11Hz? What are the chances that anyone within their target demographic/audience would take the time to download an 11Hz sine wave to verify the response? How many DefTech owners do you think actually own measurement gear?

Also, I didn't see an actual output claim associated with their claimed response. <---Something I honestly think might have been removed at some point because I could have sworn to recall seeing something like 121db output claim.

That said, maybe the DefTech Reference can, in fact, effortlessly respond to 11Hz...but at -60db from their max output? Who knows... I don’t care enough to try to investigate. In a way, I have to thank DefTech because my experience with their subs was one of the primary driving forces behind my quest for the truth!
Quote:
Originally Posted by eljaycanuck View Post

My first sub was a DefTech ProSub 200TL: 250W, 18-150Hz. Nice sub.

When I had a chance to demo an Energy S10.3 - 200W RMS, 21Hz @ -3dB - I was surprised at how much deeper it went (and how much more cleanly it played).

I contacted DefTech, and found out that the 200TL was actually rated to 26Hz @ -3dB. That explained it.

Why did you have to contact them for the information? Was it not readily available on their website? Does one have to call the company for the +/-3db point of all of their products?

Quote:
Originally Posted by shadyJ View Post

It's not extortion, it's just plain old fraud. Extortion would be if some Deftech sales reps came to your house, grabbed you by the collar and said, "You better buy our subs or else you might have a 'nasty accident'".

I'd be willing to bet their sales reps are extensions of their actual products. No balls...
post #357 of 663
Thread Starter 
Quote:
Originally Posted by jlpowell84 View Post

Yes. And you know I don't think their stuff is trash. Surely it's not Bose status but much better. I would really like to keep my DT 8060 towers for an area that won't be my dedicated setup. They offer decent sound and bass for music in a 1 cubic ft footprint. But I'm heading toward a JTR setup and that requires funds to raise.

I don't think their stuff is trash either... Very well built and usually an excellent product to accomodate WAF.

I really don't mean to bash on their products per se. My comments above are really based more on their business/marketing practices.

I can't respect a company that disrespects it's customers.
post #358 of 663
On the other hand, the Deftech Trinity sub actually looks pretty good. There are better choices for $3k certainly, but it's a Deftech sub I would love to own, which is more than I can say for any of their other subs. One of the few B&M subs worth a damn.
post #359 of 663
I have a family acquaintance who is a very successful business guy. He started a thing called rapid refill ink here in Eugene OR. He made many seven figures off of it. I only say this so you know he knows what he is doing. He once told me how he does business. He goes, "Jason, if I tell you I'm going to give you $50 to paint a fence white, then I expect it painted white and you can expect $50." He was getting at the "this is what you get and I give for this amount" mentality.
post #360 of 663
Thread Starter 
Quote:
Originally Posted by shadyJ View Post

On the other hand, the Deftech Trinity sub actually looks pretty good. There are better choices for $3k certainly, but it's a Deftech sub I would love to own, which is more than I can say for any of their other subs. One of the few B&M subs worth a damn.

Why would you want a sub with the same response as posted above just with an additional 6db of headroom (at best).

Then again... I guess I would have to agree that it would be one of the more capable subs offered from a B&M perspective... Knowing why I know now, I don't think that is saying all that much.
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