Most systems probably need some bass enhancement. But illogical to have one curve built on another when you can simply dial-in an EQ with your DSP.
Yes, systems I put together also sound absolutely wonderful to me too.
I think posters who boast their systems are so great ought to post their in-situ measurements.
Here're some for me. Anybody think they can calculate the first plot after seeing plots 2, 3, and 4?
17 foot pipe sub 12-230 Hz ±5dB
B.
What "guesses" are you talking about?
A Linkwitz-Transform implementation requires actual measured parameters of the existing driver/box system to feed the beginning calculation of the necessary EQ.
Once implemented then actual measured parameters are evaluated to verify the objective was met. You then circle back around and fine-tune, if necessary.
There's nothing seat-of-the-pants about it.
The "influence of the room and everything else" is a separate topic, obviously.
Dave.
Your perceptions of the technology are naive. I bet you think "flat" is the bass curve that most careful listeners end up with when they're done fine-tuning.
Are you saying the hole in the bottom of your boat isn't relevant to choosing the kind of waterproof paint to use on the hull?
Sometimes:
Parameters vary with time.
Manufacturers lie.
Very hard to measure some parameters with any kind of accuracy.
Manufacturing tolerances can be big.
A small mis-guess about one parameter may destroy the whole value of the LT calculation even when you calculator goes to three decimal places
.... and on and on
Or your spouse might want to move the speaker a few inches and the whole process is thrown out.
Again, with all those loosey-goosey factors, why not just tune the EQ empirically since that is what you must end up doing anyway.
B.
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You don't need any published manufacturers parameters (lying or not) to implement a LT. They're irrelevant.
Your post reads like you don't understand the concept or design of a Linkwitz-Transform at all.
Maybe review the description from SL himself.
Active Filters
Dave.
Your post reads like you don't understand the concept or design of a Linkwitz-Transform at all.
Maybe review the description from SL himself.
Active Filters
Dave.
I have a Leach transform made by a fellow Karlson - fanatic. - He uses that on some Karlson - couplers which have vented back chambers. It was set to remove some hump @50Hz which I really don't think K15 would exhibit. (K15 in half space outdoors is up to 10dB down at 50Hz) It uses internal circuit board header plugins which he didn't describe. Although response with such a thing on a vented cabinet doesn't truly make a flat graph down low, the compensation can de-localize the cabinet compared to no eq (assuming the recording has room ambiance and LF in the first place)
I also think that some people have not read or understood the LT-Transform.But for people relying only on dsp it is quite easy:Buy three very cheap chassis of 30cm,10cm, and 2cm and put them into an enclosure. And buy 3 amps and a dsp and a mic.After having equalized 25 peaks and 23 dips you have the best sounding system all over the world.But a word of caution here: Some people relying only on dsp, have compensated themselves and were lost in the acoustic enviroment.
Or buy one of the different DIRAC machines.They will do all for you ( ???) and you have not to stand up or sit down.
Or even more simply, speak : " Alexa, best sound please"
I'm too old and stuck in my ways for any of that digital nonsense...😀
It'a analog all the way for me.
![[[2B CROSSOVER]].JPG](https://www.diyaudio.com/community/data/attachments/664/664727-596d1f74bf7f3f1f9eea12718c831183.jpg?hash=WW0fdL9_Px "[[2B CROSSOVER]].JPG")
Mike
it appears that the ltx used to extend the woofers low end also drives the mid/treble branches...
Yes, I think your arrangement is not correct. The LT (woofer) circuit should not be in the path of the midrange and tweeter, and would preferably be the last section in the woofer portion. (Right after U505.)
Dave.
Dave.
Nope, the phase shift created by the LT circuit will muck up the crossover region between the woofer and mid if the mid is not included in that part of the transfer function, and it follows that the tweeter must be in the path to maintain its crossover from the mid. If the mid-woofer crossover frequency was an order of magnitude above the LT frequency it wouldn't be an issue.
Mike
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The phase shift of your woofer LT circuit is minimal (8 degrees) at 140Hz, and zero above that.
But it follows then that the phase shift of your biquad sections in the tweeter and midrange branches should be included in the woofer path, yes??
Dave.
But it follows then that the phase shift of your biquad sections in the tweeter and midrange branches should be included in the woofer path, yes??
Dave.
are we in agreement, that to achieve the "benefits" of an LR crossover, that all of the drivers acoustic phase outputs must be the same ?
Sealed boxes roll off at 12 dB/8ave. LT is a bass boost meant to precisely compensate for subs that perfectly matched Linkwitz' model. Good luck.
As many have pointed out, prolly not a good way to handle the roll-off because you end up with damaging power at low freq. Better would be just adding some EQ just below the point where the roll-off starts and you have good bass and no damaged drivers. Also, you have no added distortion that arises from but large shaking of the sub cone that's producing no audible low bass sound.
Better yet would be not starting with one of those tiny sealed boxes forever recommended by Parts Express and your favourite sim program too. Start with a bigger box and get better bass with less EQ needed.
But all this action is taking place in a band where designs are hit-or-miss and the room has a monumental influence on the sound at your chair. It also makes the indefensible assumption that flat is what anybody will like, once they start playing music with low bass. If somehow you end up with a flat system you will forever be asking, "Where's the bass?".
Or you could just buy a DSP (with or without bi-amping) and add the EQ that suits your room.
B.
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I have built a couple of LT circuits. You must be careful in the choice of driver and box size trade off or things can distort and/or break. But they did do the job.
regarding the cct in post 29, it is best to simulate it to see if it achieves the goals above.
(the simulation cct should also include 2nd order HPF's to simulate each driver as defined by the Fs/Q data given in post 16)
(the simulation cct should also include 2nd order HPF's to simulate each driver as defined by the Fs/Q data given in post 16)
It's important to understand that usage of LT equalization is merely an option to extend the system response.
Once driver A is installed in box B, many of the system parameters are locked in. SPL capability and power requirements are two of those parameters. It doesn't matter what sort of equalization is applied, you can't alter/improve those.
Electrical and mechanical limits
Dave.
Once driver A is installed in box B, many of the system parameters are locked in. SPL capability and power requirements are two of those parameters. It doesn't matter what sort of equalization is applied, you can't alter/improve those.
Electrical and mechanical limits
Dave.
Hi,
I was wondering if anyone has compared the performance characteristics of a LT transform circuit to a transconductance circuit, especially for a subwoofer?
The transconductance approach is discussed here:
LM1875 transconductance amp
I was wondering if anyone has compared the performance characteristics of a LT transform circuit to a transconductance circuit, especially for a subwoofer?
The transconductance approach is discussed here:
LM1875 transconductance amp
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