Dual TD12S for center speaker


  • Member
    simon5 on #6603

    @mfishmike wrote:

    I’ve got the parameters in Xover Pro 3 and did the updates a while back. Are the T/S paremeters the same in the program or have there been some changes that I need to plug in so I can make a good xover?

    No real changes since Nick at Lambda Acoustics designed them. You can double check to be sure with the parameters available on the forums which were updated by John, but it should be nearly the same.

    As A9X said, 85L is for Q=0.707, and that would suit most people if it’s possible for you to have such a big center channel. You can always use stuffing to have more “space” if you can’t go that big.

    By the way, it’s a good idea to use TD12S like in your mains, it will be easier to match sensivity and everything else ! 8)


    Participant
    mfishmike on #6604

    @a9x wrote:

    For Q=0.707 in an unstuffed box a pair of TD12S sims out in Unibox to 85L net. F3 is 67Hz.
    Under the same conditions as above, 12H 35L 83Hz, 12M, 35L 112Hz and 12X 53L 89hz.

    A9X,

    Thanks for the modeling…..

    I’ve just calculated the actual internal volume and am asking if you could figure the pair of TD12s for the center speaker again with the correct volume. I have a net volume of 3.74 cu ft or 105.42 liters without the 2 drivers’ displacement figured in. I couldn’t find those displacement numbers posted anywhere. I figured the volume to include the bracing and center speaker’s midrange box displacements. I do have enough space to mount them.

    Thanks in advance for your help. I need learn to work with unibox and winisd. I just haven’t had (or maybe taken) the time.

    Mike


    Participant
    mfishmike on #6605

    Simon,

    My center channel box is 16″ H x 17″ D x 34.5 W with net volume of 3.74 cu. ft. or 105 liters.

    I just went to the AE store and found the T/S numbers posted with the description, so when I go to figure the xover, I’ll make sure XoverPro 3 is using the same numbers.

    I haven’t heard back from John yet. Is he on Easter vacation?

    Thanks

    @simon5 wrote:

    @mfishmike wrote:

    I’ve got the parameters in Xover Pro 3 and did the updates a while back. Are the T/S paremeters the same in the program or have there been some changes that I need to plug in so I can make a good xover?

    No real changes since Nick at Lambda Acoustics designed them. You can double check to be sure with the parameters available on the forums which were updated by John, but it should be nearly the same.

    As A9X said, 85L is for Q=0.707, and that would suit most people if it’s possible for you to have such a big center channel. You can always use stuffing to have more “space” if you can’t go that big.

    By the way, it’s a good idea to use TD12S like in your mains, it will be easier to match sensivity and everything else ! 8)


    Member
    simon5 on #6606

    Well since you are going sealed, internal space precision is way less important. Since you have more than 85 liters available, you will be fine. Those drivers will take about 2 liters or less, so I simulated with 100 liters.

    You will have 0.69 alignment instead of 0.707, which is fine.

    John have been hard to reach lately, I guess he’s busy and yes probably things to do with kids for easter, I wonder ! 8)


    Participant
    mfishmike on #6607

    @simon5 wrote:

    Well since you are going sealed, internal space precision is way less important. Since you have more than 85 liters available, you will be fine. Those drivers will take about 2 liters or less, so I simulated with 100 liters.

    You will have 0.69 alignment instead of 0.707, which is fine.

    John have been hard to reach lately, I guess he’s busy and yes probably things to do with kids for easter, I wonder ! 8)

    Simon,

    XoverPro 3 did have some different numbers, so I changed what I could till I got a red indicator of the wrong value that I got from the Store.

    If you have those numbers still plugged in, can you tell me what the F3 might be with the extra 15 liters?

    I appreciate your correspondence and will wait to hear back from John. I’ll spend the rest of the weekend working up xover specs.

    Mike


    Member
    simon5 on #6608

    It’s 66 Hz F3 instead of 67 Hz, it’s not a big difference. The rolloff will also be slightly more shallow, but not that much. That is without any polyfill. Polyfill would slightly increase F3 but have a shallower rolloff, if that is needed.

    The best numbers are here AFAIK : http://www.aespeakers.com/phpbb2/viewtopic.php?f=3&t=2377


    Participant
    mfishmike on #6609

    @simon5 wrote:

    It’s 66 Hz F3 instead of 67 Hz, it’s not a big difference. The rolloff will also be slightly more shallow, but not that much. That is without any polyfill. Polyfill would slightly increase F3 but have a shallower rolloff, if that is needed.

    The best numbers are here AFAIK : http://www.aespeakers.com/phpbb2/viewtopic.php?f=3&t=2377

    Simon5

    Thanks for the numbers. I’ve got a great xover worked out with impedance EQ and a resistor to compensate for the high efficiency of the paired TD12s.

    Have a great Easter weekend.


    Member
    simon5 on #6610

    Your tweeter is less efficient than your paired TD12S ? You better use a beefy resistor if you use lots of power hehe ! 8)


    Participant
    mfishmike on #6611

    @simon5 wrote:

    Your tweeter is less efficient than your paired TD12S ? You better use a beefy resistor if you use lots of power hehe ! 8)

    Simon5,

    I got ahold of John today and he has a pair of 4 ohm TD12s that will work better in series than the 8 ohms in parallel. I only need to eq my tweet a bit. The xover shows a nice plot with them in series. I’m driving the mains and center with the Emotiva Supercharger 3 channel amp, so I’ve got plenty of power to spare. I’ll post some progress pics after xover is done and the drivers are here.


    Member
    simon5 on #6612

    Nice, good idea ! 8)


    Member
    simon5 on #6613

    @mfishmike wrote:

    btw….I spent a lot of time posting some of my earlier builds with the Lambdas and the Prs. John asked me to post them. What happened to the pics? They are all gone, replaced with those nice X red empty boxes.

    Mike

    John confirmed to me that it has been probably lost due to forum updates to try to correct the nasty spam issues we experienced several months ago, We are very sorry about it, and if you want you can update the links if you wish so. Sorry again for your time…


    Participant
    mfishmike on #6614

    @simon5 wrote:

    @mfishmike wrote:

    btw….I spent a lot of time posting some of my earlier builds with the Lambdas and the Prs. John asked me to post them. What happened to the pics? They are all gone, replaced with those nice X red empty boxes.

    Mike

    John confirmed to me that it has been probably lost due to forum updates to try to correct the nasty spam issues we experienced several months ago, We are very sorry about it, and if you want you can update the links if you wish so. Sorry again for your time…

    Thanks Simon5….I’m studying for my electrical master’s exam so when I get that behind me, I’ll have more time to work on it. The new TD12s are on the way. I’m tracking them now.


    Participant
    mfishmike on #6615

    Simon5,

    I took some time from the books and treated myself to a couple of hours of crossover build time. It is finished and awaiting the Lambdas next Tuesday. I eq’d the tweet just a bit and my graph is about as flat as can be; ie a perfect graph. My f3 shows I’m going to be about 58 to 60 hz with a gentle roll off. I use my THX setting and cut everying off at 80 hz anyway. I’ve got a nasty impedance hump at 30 hz on the Lambdas, but my xover point is at 500 hz so that is far enough away so I shouldn’t notice it. Nothing I could enter would correct it. I’m certainly not worried about it at 30 hz. The 4 ohm drivers were a blessing indeed. My xover board is a large one so I’m not worried about all of the inductors laying flat as far apart as they are.

    I’ll keep ya posted with the pics.

    Mike


    Member
    simon5 on #6616

    Yeah I was about to tell you about inductors laying flat but you are right that they are far away. Also since you glued them, there’s no problem with metal screws messing with inductance.

    The 30 Hz impedance hump is normal, it’s the Fs of the driver, which will become Fb once in a box. It’s the driver entering into self resonance mode, like an electrical circuit in resonance, where it needs the less power to produce the most loudness. Usually, you only correct that in tweeters with a parallel RLC circuit, also called Zobel filter. It’s possible to do it with woofers, but problematic because it needs huge components, and as you said, it’s not worth it at all to correct it, too low in frequency, can’t hear it and amplifiers don’t care about it, unless maybe some tube amplifiers.

    Well, you already designed nice speakers, so you probably know about all this… if yes, ignore what I just said ! 8)


    Participant
    mfishmike on #6617

    @simon5 wrote:

    Well, you already designed nice speakers, so you probably know about all this… if yes, ignore what I just said ! 8)

    Thanks for looking and commenting….When I was 16, I used to break off my erasers ’cause I knew it all. At 58, I order extra erasers when I buy my pencils. I’m not as smart as I thought I was, so I always am open to suggestions. That is what the forums are here for and how I’ve learned over the past 15 years in part.

    I think it is going to be some kind of awesome center speaker when it’s all finished. I’m sure glad John bought out Nick’s inventory and kept the Lambda line in production.

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