DIY monitors question

[TomasJ]

Great, thanks!

So as far as separating cabinet. I get great results with 11l volume for my woofer. So if I want to separate cabinet, I dont' really separate, I just add one more (maybe smaller one) for tweeter? Is this right?

 

[TheJames]

One thing that was hinted at by Michael (and something I almost wrote about last night) is the difference in the time domain of a sealed vs vented box.  A sealed box will seem "punchier" and more "dynamic" with "tighter" bass.  The trade off compared to a vented design is low-frequency response.  Sealed boxes typically don't go as low.

A vented box, while producing more output at a lower frequency than a sealed enclosure, will seem a little "looser" dynamically speaking.  They also tend to "unload" at and below the port tuning.  In some designs the force of air moving through the port causes a sound on it's own. 

With a sealed box, the overall internal dimensions aren't that critical.  You can model this yourself by changing the box dimensions with your driver and seeing how  (little) the response changes.

In a vented cabinet, the internal volume is pretty important as it works with the tuning of the vent and the mechanical characteristics of the driver.  Anything that consumes volume inside the speaker enclosure should probably be accounted for (crossover, tweeters, enclosures for midranges, the woofer itself).

That said....Most (not all) tweeters won't really have an air-path to the  tweeter diaphragm from behind so I wouldn't consider a separate enclosure inside the speaker system necessary for the tweeter.  I also wouldn't consider the volume occupied by the tweeter to be of much consequence, but again...If you want to be spot-on, calculate the volume and adjust box size accordingly.  This is same idea as Michael was suggesting with calculating the internal volume of the cabinet offset by the woofer.

Sounds like you're making progress.  Keep it up.

 

[TomasJ]

Thanks guys! So I've decided to use another woofer. It's a paper cone 61/2'' woofer which is no longer made. The brand is from Czechoslovakia (in 1993 it split to Czech republic and Slovakia - where I am from) and in 2010 they stopped making more speakers. I've found an eshop where a guy sells last stocks and this woofer has some great parameters:

http://www.tvm-valmez.cz/index.php?id=109&catit=88&l=1&catg=1

here's the frequency response in  the same sealed box as the previous woofer:
http://postimg.org/image/tpqyab8rb/

and if I use some damping, as audiomixer said, the woofer will act similar as in a 20% bigger cabinet, we are getting this kind of frequency response:
http://postimg.org/image/u6e9z9sol/

Maybe I can make a cabinet slightly bigger to get even closer to what I want. But I am talking here about 1 or 2 liters.

What do you guys think about this woofer?

I've decided to not split the cabinet but use it's whole volume for both woofer and tweeter. Splitting might make me make pretty big cabinet which I don't want to. Anyway I am getting pretty nice frequency response with what I already tried so I better stay with one non separated cabinet.
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Tweeter part.

So as we already finished woofer part, lets talk about tweeter. The first question that's in my mind is what about power? If the woofers power rating is 100W RMS/ 300W Peak, what should be the tweeters numbers?

As far as tweeters frequency range. If my woofer covers 40hz-4khz, what's optimal frequency range for tweeter? is 1.5khz too low?

Are there any calculators for tweeters or for whole two way speaker box  to see its frequency response?

Thanks,
Tomas.

 

[audiomixer]

HI,

splitting the volume does not mean splitting it in half.... usually you would use an L-shaped partition to divide a small (0.5l) volume for the tweeter, not half of the box... but hey, no problem here.

regarding the 6.5" woofer, I don't know which one will be better, but that might not be the biggest issue at hand. you will need to have an possibility to take acoustic measurements - so that you see what happens with x-over design. your x-over frequency can't be set theoretically and inductors / capacitors calculated using your 4 or 8 ohm driver impedance. first the impedance is variable over the frequency range, and secondly some driver will not cross over at certain frequencies.  trying to do so results in very funky response curves, so the driver will 'tell' you what x-over frequencies are actually doable. this will pretty much define your tweeter requirements. the size of the drivers also influence the on-axis / off-axis response. larger drivers have narrower coverage at higher frequency. at the same frequency the small tweeter will have a much broader coverage. matching the optimum x-over frequency with all of these basic criteria is part of the art of speaker design. measuring on axis / off axis and comparing them helps to find out if the chosen x-over is a solid candidate. lower order x-over (6dB / oct or 12dB/oct are simpler to adjust and to get to work, but they have limitations as well of course. listening test help identifying issues / problems.

now to you original question. generally power in music is concentrated around 80Hz - 200Hz, depending your musical taste. the upper frequency range requires significantly less power. if you tweeter has a higher sensitivity them your woofer - that is usually so - then you will automatically reduce the level directed to the tweeter, giving you more headroom. I think 100w/30w LF /HF is a sound choice for a two way speaker. try to get a tweeter with a reasonably low resonance frequency, but may be not the lowest possible. lets say between 1000Hz to 1500Hz.... a larger tweeter (the dome, not the mechanical size) might give you more headroom.

cheers,

michael

 

[TheJames]

The new 6.5" woofer has a bit of a lump in the LF that might not be desirable.  It does have much smoother upper-range response which will make integrating with a tweeter easier.  A second-order low-pass at 2.5k should be a good starting point.  When looking for a tweeter, I'd find one with similar sensitivity or you'll need to add in some attenuation in the crossover to tame the loudness of the tweeter.  I don't think you'll have any concerns with the power handling of a tweeter matched with this woofer.  I'd say 30-40 watts would be a good target.

With tweeters, there's typically very little internal box considerations as it primarily interacts with the surface of the front baffle.  Generally speaking, you'll want to put the tweeter as close to the woofer as possible.  In a perfect world, the tweeter would be recessed to be more in-line with the woofer.  You don't want a hard edge near the tweeter and if you look at most modern studio monitors, you'll see a contour (waveguide) around the tweeter.  Many modern tweeters will have a smooth curved surface from the tweeter dome base to the top surface of the tweeter mounting plate.  Ultimately this plate will be recessed into the front baffle.

Michael just dropped some good info on what it will take to really tweak the speaker to get it to sound good.  You can kind of guess at things and come up with something that works (like how I can guess that a 2.5k second-order low pass will be good with that 6.5" woofer).  But if you want it to be "good" to "great" you'll need to measure the drivers' response in the cabinet (frequency and impedance) and design a crossover that corrects any oddities in the response.  You'll listen, measure, tweak, measure, listen for hours and may decide that you need to use a different woofer/tweeter.  But that's the fun of designing a speaker system.

 

[TomasJ]

Thank you guys! Some really helpful stuff are here! I'll try to look for some appropriate tweeters and crossover design and will come back to you with some candidates. Thank you many times!

Tomas.

 

[TomasJ]

Ok so here I am back with my tweeters. I checked few local shops and eshops. I think I've found the best one I could (according to what frequency response I required). I also add two more candidates just for you guys to tell me whether it's better solution or not. There are few questions about tweeters that come into my mind. In each tweeters technical data the frequency range starts with "fx". What does it mean? How can I calculate this value? Second question*. I can't see any difference between 4ohm and 8ohm when it comes to tweeters. (Woofers have some differencies in T/S parameters between 4ohm and 8ohm version which can be seen on frequency response.) So how can I know which version is better for my system?

1. http://www.monacor.co.uk/products/0/vnr/105320/
that's the number one tweeter for me but I am not sure about the power. Isn't 45W/100W too much?

2. http://www.monacor.co.uk/products/0/vnr/100040/
3. http://www.monacor.co.uk/products/0/vnr/104010/

Last two tweeters's frequency response is pretty much flat at high frequencies.

Now about crossover. I am not sure how to start. You guys said it's not possible to choose right crossover theoretically. So what I basically can do right now is just hope that the 2.5k two order crossover will be the best starting point right? Now what's the difference between Linkwitz-Riley, Butterworth, Bessel and Chebychev type of crossover? And is impedance really the only parameter (and also desired crossover frequency) I need to calculate crossover? When I use both tweeter and woofer with same impedance, all the components in circuit are same (L1=L2, C1=C2). Once I change tweeter to 8ohm and woofer to 4ohm (or vice versa) parameters change. So is this the answer on my previous question (marked with *)?

Anyway I checked crossover circuit diagram of ns10. (once again, I am not trying to copy these monitors, I am just trying to compere mine with something thats possible to find on the internet and ns10 are so 'revealed' that I can find anything about them.) What I don't really understand is following. I put 8ohm woofer and 4ohm tweeter in calculator, x-over frequency set to 2k as it's done in NS10 and chose linkwitz-riley type. I got very similar component values as are used in ns10. BUT! It seems like condensers are switched. The condenser that should be (according to calculator) in tweeter part of circuit is used in woofer part of circuit and vice versa. I am not sure you guys understand what I am trying to explain as my english sux, but please check this pdf: http://www.advancedaudiorentals.com/docs/ns10mstudio.pdf and then try to use any online x-over calculator and put 8ohm in woofer field, 4ohm in tweeter field (ns10 use this kind of woofer/tweeter) and set x-over frequency to 2khz and use linkwitz-riley type. you'll see what I mean. And my question is - is it so variable thing that the values of components in crossover can be even twice as big/small as calculators suggest?

Thanks for your help guys
Tomas

 

[audiomixer]

the crossover interacts with the tweeter / woofer much more then what x-over calculators suggest. even if you use impedance linearisation (look at zobel network et al.) so the basic calculation is a start at best, not a final recipe.  again, that's were you need a measurement system.  try something out, check, change.....

out of the monacor range I would also consider the DT-280, or the large DT-300 but this is not a recommendation out of knowing the tweeter itself, just the look of some parameters....

the impedance is probably not critical, usually 8 ohms speakers are an easier load for the amplifiers. 4 ohm are recommended for low supply voltage (like in a car...) or mobile applications. very high power subwoofer system can be as low as 2 ohms nominal....

cheers,

michael

 

[TomasJ]

Ok so I think, we are done here. I'll check your suggested tweeters and pick the best out of all I checked. Then I'll simply try to create at least two  different crossovers and build a proper cabinet. Then it's all just about listening and changing. One more question for you guys: is there any software I can use to measure my final systems frequency response or group delay or any other parameters. I mean the parameters of whole finished speakers. I am using mac but there's no problem using windows at all.

Also what do you think about this tweeter: http://www.tvm-valmez.cz/index.php?id=107&catit=191&catg=5
Isn't it too week? 20W rms/30W peak? Or this can't be an issue?

Oh and can you please answer my previous question? What does fx in frequency range means? "Frequency range: fx-20khz"

It's beed an wonderful time chatting with you. I learnt some useful stuff and finally am able to build some starting point. I'll let you guys know once I finish my project how it's done.

Best,
Tomas.

 

[audiomixer]

fx - 20'000 means from crossover frequency to 20k....

Arta is good chioce for LS measurement andis basically free for private use. www.artalabs.hr

from the TVM I would try to go with a higher end one, but hey, they do cost more....

good luck with your build. 

- Michael

 

[TomasJ]

from the TVM I would try to go with a higher end one, but hey, they do cost more....

But is it an issue putting 20W/30W tweeter in pair with 100W/300W woofer?

 

[TheJames]

Most of the power in a speaker system will be used by the woofer.  It takes much more juice to produce 100db of 50hz than it does to produce 100db of 12khz.  A 30-40 W tweeter should pair will with a 100W woofer just fine.  20W might be fine, but I would be a little cautious if you plan on "cranking" things.

 

[audiomixer]

.  20W might be fine, but I would be a little cautious if you plan on "cranking" things.

to expand on this a little: if your tweeter has a higher sensitivity then your woofer  you will use a L-pad to reduce the level. let's say by 3dB for example. this will let you drive the HF segment with double the power - since 50% go into the resistor network. suddenly your system has 40W HF power handling capability. so there is no final answer to whether 20W are ok or not. soft factors like the crossover frequency, the filter slope (2nd order, 3rd or 4th order filters) or  the type of measurement done by the manufacturer to get this figure are excluded anyway. you can not trust manufacturer specifications by the book... 
the sensitivity you can reach with your woofer also depends on the alignment. you might have to reduce the woofers midrange to attain a flat response using additional parallel or serial LCR filtering, or by aligning the crossover itself to form a dual slope (-6dB/oct from lets say 800 - 1600Hz, then getting steeper so that you reach -12 dB /oct at your crossover frequency). this is some part of the art of crossover design, to compensate for irregular driver response. remember, the measured curves from the manufacturer are done on a very large flat surface, not your typical box. this has great influence in the actual frequency response of your drivers.


- michael

 

[TomasJ]

Hey again! Now I have question about damping. What's the best material and the best method to damp the sealed cabinet? The question is not really about 'best' method but the one that you guys have any experience with and what works and what doesn't.

I've found few methods:
http://i555.photobucket.com/albums/jj456/letstakeawalk42/BozakB-305internal002.jpg
http://www.troelsgravesen.dk/cabinet-damping_files/cab_damp_CSM01.jpg
http://www.troelsgravesen.dk/sonab_files/sonab_OA6-II_18%20(1).jpg
http://img.photobucket.com/albums/v347/shaneybob/Speaker-Damping.jpg
https://s-media-cache-ak0.pinimg.com/736x/62/e8/3b/62e83b3e8a3c96ab2473e92573ae17e3.jpg
http://www.preservationsound.com/wp-content/uploads/2013/09/Technics_SB10_inside.jpg

Which method were you talking about in previous posts Mike?

Thanks!

PS.: btw why when I put image link into '

 

[spintonik]

Hello,

You guys a pretty deep in loudspeaker design - I am newcomer to this group (altough I happen to know a bit from loudspeaker design myself and could perhaps help) and I am bit unsure if I should put my 50 cents into this discussion - You've been directing fearless TomasJ to right direction

However, I did read from somewhere, that TomasJ, You're trying to make a sound replica of Yamaha NS10. Is this still correct assumption?

So many things affect to the sound, "timbre," of a loudspeaker. It's drivers, cabinet, cabinet materials, acoustics, driver placement, cross-over components, etc etc.

The only way to replicate NS10 would by copying the design as well as you can, starting from identical drivers, then continuing to dimensions. However, like anything else legendary - someone's done it and posted a great article about it! And it's not even that hard. NS10 drivers should be available at Ebay, rest is more or less just woodworking.

Google search for "Yamaha NS10 DIY" gives you so much to read, but I enjoyed this one:
http://mnats.net/ns-10_clone.html

Good luck!

 

[TomasJ]

...once again, I am not trying to copy these monitors, I am just trying to compere mine with something thats possible to find on the internet and ns10 are so 'revealed' that I can find anything about them...

you must've miss some of my notes. I explained few times that I am not trying to copy NS-10. But thanks for your '50 cents'

Tomas.

 

[audiomixer]

damping itself is probably an art in itself.... damping the cabinet is about reducing the cabinets resonance, but not fully filling the cabinet or you will lose a lot of LF, specially in vented enclosures. but for closed boxes, its not to critical.

I used or seen pretty much every possible lining: glas fiber matts, sheep wool, PE based wool, natural fibre matts, open/closed cell foam, you name it.

I would start with foam / fibrous matts or wool. a combination of two products for example.

cheers,

michael

 

[TomasJ]

Basic question (sorry about it): if my woofer is 4ohm and tweeter 8ohm. What's the final impedance of my speakers?

 

[audiomixer]

you should take a look at a few impedance traces for different speakers around the net. it's almost never flat (I can be on special cases). you take the lowest point in your speakers impedance. this may be around 20% lower then your nominal impedance. so lets say if you measure 3.6 ohms at a certain frequency, you may well call the speaker 4 ohms. the minimum impedance rules....

your speaker will probably end up being 4 ohms nominal, unless you build a very funky crossover....

- Michael

 

[TomasJ]

So basically when I finish my speakers and measure the impedance on the speakers output, I get the answer on my question right?