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|13th February 2020, 07:43 PM||#1|
Join Date: Feb 2020
(Beginner) An attempt to improve my speakers, help appreciated.
I want to improve the sound quality out of my speakers, yes - I know, a very generalized term, but then again I'm a complete beginner.
To start off, here's a picture of my speakers:
Here's a drawing of the cabinet:
The manufacturer will not help me in telling each drivers individual specifications, they're way too secretive, hence my doubt of the speaker not performing as per specifications.
Word has it this speaker performs very well in its price point, it's pretty much impossible to find speakers sounding this good for any lesser amount, and I can honestly agree, as long as you don't build the speakers from scratch yourself, nothing really beats it at this price level, which is $300.
Manufacturers and my take on the specifications:
Cabinet consists of 18mm MDF all around, and 15mm bracing internally.
MTM enclosure is 12,97 liters, woofer enclosure is 58,76 liters (with ports plugged from the inside)
4x 80mm 150mm long vented ports in the rear
1" Super Audio (lol) fabric tweeter, all plastic, neodymium magnet, 6 ohm
2 x 5.25" midrange, coated paper, shielded, steel basket, 80mm magnet, 4 ohm each
2 x 8" woofers, coated kevlar, full cast aluminium basket, 100mm magnet, 8 ohm each
Frequency Response 24-32000 Hz (- 3 dB)
Crossover Frequency 240/2500 Hz
Impedance 4-8 ohms
Sensitivity 94 db
RMS Power 190 W
Max Power 280 W
There is a terminal where you can change the midrange, -2 dB / 0 dB / +2 dB / +4 dB
Size (HxWxD) 1100 x 238 x 395mm
Weight 28 kg per tower
I don't know how to measure the drivers to calculate the RMS wattage of each individual driver, the impedance I could easily measure, but the sticker on each driver should do just fine.
There is no ampere figure on the drivers, the wattage is therefor completely unknown.
Word has it the tweeter easily blows if you turn the speaker up too loud, common issue.
To my plan:
I plan to focus on the weaknesses of these speakers, I find the cabinet to be of my taste, and it's decently sized for my room, fits perfectly with all of my other speakers too.
Obviously the tweeter needs to be changed, it's probably very weak, either that or the crossover is just poorly designed, I would guess a mixture of the too, but more the tweeter itself being the issue.
Also the midrange is made out of cheap coated paper, by the looks of it it's a very cheaply made driver, only 80mm magnet, and the overall quality inspection and feel of the driver is very cheap, there is no quality inspection during the fabrication process it feels like.
The woofers however, they're not that critical to replace, they're made of kevlar (supposedly) and it looks very much like it at the back of the cone, however the magnet is only 100mm, most midrange drivers have this size and that makes me question these woofers.
I also plan to seal these cabinets with foam plugs internally, so that I reduce the cabinet volume as much as possible (the new midrange speakers I found does require a bit less volume) so nothing wrong in that.
While doing these improvements to the speakers, I also cover all the inside walls with dampening material (Zachry Q12) since I seal the cabinets fully, I don't fill them fully. just cover up the walls.
Is there a better way to dampen the cabinets, again - please look at the cabinet drawing and suggest improvements.
First however, let's focus on tweeter and the midrange.
I know I will need to design a new crossover for these improvements and changes, I've fiddled around somewhat in XSim, planning on getting a UMIK-1 to measure the current speaker as a whole and each individual driver.
I found this tweeter to be a perfect match, physically, and it seems really nice by looking at the specifications as well, people have reported this driver to be perfect with a 2k crossover, and it's made out of fabric, which my atmos upfiring speakers are too, so that's good I guess.
SB Acoustics SB26STAC-C000-4 - 1.1" Dome Tweeter
As for midrange, it's quite tough finding speakers with the very strange frame/basket shape that these speakers have, it's a square shape with rounded corners.
Anyway, Aurum Cantus reportedly seems to offer pretty nice midrange speakers, I have no clue what my current midrange are rated at in terms of power, or pretty much any specification really, other than the magnet being 80mm, and the 4 ohm rating.
Aurum Cantus offer many variations, but I thought that the AC-130MK2 looked pretty nice, it's very even in the frequency response, and the 2k crossover fits perfectly with the SB26STAC-C000-4 from what I can tell as a beginner.
Aurum Cantus AC-130MK2 - 5.5" Woofer
Right, my questions:
1) Can I measure the RMS wattage closely to the manufacturer specifications (if I had them) by measuring with a True RMS volt/ampmeter?
2) If yes on the above, tell me step by step how to connect everything, because I'm unsure if the drivers can be connected directly to a PC for example, you would need some sort of amplifier I guess, but is a normal 2-channel amplifier (like a Yamaha) overkill, is it easier to have a USB soundcard at hand?
3) What kind of test tone would you output, is there a general rule of thumb, 1k? 2k? What kind of SPL, just about any would do? Speakers vary quite a bit in voltage and amps (hence also watts) that's why I ask.
4) Does my suggested tweeter/midrange combo look like they would match and yield great performance if the crossover is designed correctly?
5) How would I go about matching the tweeter/midrange to my already existing woofers, do I need to measure them and create/generate a FRD/ZMA file somehow, with the UMIK-1 maybe?
I've read some stuff on the forums, but I have a hard time connecting everything together, I appreciate all the help you can get me, we all start somewhere, this is where I start.
Explain to me in a greater noob fashion that you think you need to, because eventhough I might of touched on some delicate topics, I'm really just a beginner.
And oh yeah, I plan to measure the speakers assembled together (once upgraded) in the room where they'll be used, so that I can measure the room strength/weaknesses and implement and compensate for those in the crossover.
I have no issues at all having to re-design the crossover if moving the speakers to a different room.
Feel free to toss my thread around, anywhere it can go for the right answers and I'm more than glad.
Maybe some real gurus could hop in and have a go at it, I need all the help I can get.
I'm used to be an electrician as a profession, so I'm not too shabby with electrical terms and how all that plays out.
I would give you something if I could, thank you.
Last edited by Vitus; 13th February 2020 at 08:11 PM.
|13th February 2020, 08:33 PM||#3|
Join Date: Apr 2019
It is a very difficult job to shoe horn different speakers into a established cabinet. Yes changing the tweeter is the easiest. The cabinet size & shape has been developed to suit the other speakers & most likely will not suit another speaker from a different supplier. One way to upgrade the sound is to ditch the X-Over & go for tri-amping with an electronic X-over. It will mean buying a bass amp (around $100, class D TPA3255) & tweeter amp (around $35, Class D TPA3118)
However if this does not suit, then you need to buy or build new speakers.
|13th February 2020, 08:41 PM||#4|
Join Date: Sep 2011
A few people have replied since writing my main post. I would agree with them, probably not worth messing with an “affordable” commercial speaker.
Having said that;
Building a new crossover for those speakers may be worth a try even just for the learning experience, I cannot recommend changing drivers. You would need to modify the enclosure, changing the midrange driver will almost certainly require a different enclosure volume. At most I would consider changing the tweeter.
I do not want to stop you from trying but when I first started in DIY speakers I considered modifying commercial speakers before building a new design. If you are going to invest in the measurement gear and put the time in you may as well just start with decent drivers and build your own enclosure?
I would highly recommend getting the UMIK-1 as the frequency and impedance response is unknown.
You will also need something like DATS to take an impedance measurement, your post states you can measure impedance not sure if this is with a multimeter?
I would try to get a measurement of the speakers as they are before deciding on any new drivers.
Sorry I cant help you with “measuring RMS wattage”, I would instead measure for harmonic distortion on each driver at increasing levels and go from there.
Also I would Not try to account for the room frequency response within a passive crossover. Not sure if that is what you meant or not?
|14th February 2020, 12:15 AM||#5|
Join Date: Jan 2014
DO NOT try to measure the speaker RMS wattage, there is no need for that! It is certainly 100 Wrms at least, so you can safely use a 100 W amplifier. You don't need anything more powerful than that.
Cheap look of the drivers doesn't "guarantee" low sound quality, but skimpy woofer magnet may produce boomy bass. Put more damping material in the cabinet and block vents with foam - it should tighten the bass.
If all these doesn't help, only then you can try to replace drivers with the better ones. For that you need UMIK-1, REW or ARTA measurement software and sim software (VituixCAD or similar). Prepare for many hours of learning... and fun!
|14th February 2020, 12:26 AM||#6|
Join Date: Apr 2008
Location: Carlisle, England
You need to sit down and decide what you want fro ma set of speakers and what you didn't like about your ones.
A simple approach I use is using full range drivers line Fane 12-250TC which goes from low to 17KHz. Some love it and some hate it but I have had good results with a pair. With full rangers you get rid of the pain and cost of crossovers.
If you want a bit more bottom end and size isnt a problem then Fane 15-TC300 is an option.
2020 versions of PCBCAD51, PCBCAD360 and PCBCAD720 out now >>> https://www.murtonpikesystems.co.uk
|14th February 2020, 05:28 AM||#7|
Join Date: Jun 2007
Location: Norlane; Geelong: Victoria: Australia
I will assume that is $300- USD
If so they do actually look like good value.
I wouldn't bother yet with any driver substitutes, instead i would ask how long you have owned them, how hard you have driven them and what sort of music you listen to.
Secondly have you taken the drivers out and had a look in the boxes interior?
Padding or no padding? If padding what is it?
If no padding add some decent fibreglass, wool wadding or good synthetic fibre; especially to the mid-range
Thirdly some cheap speakers can sound a lot better by adding in a good pair of subwoofers and taking all of the signal below 80 / 120 Hz
We need pictures of the midrange drivers from the rear Ditto the tweeter I don't think they are sealed back drivers because of the separate driver compartment but best to be sure
QUOTE" The more I know, the more I know, I know (insert maniacal laugh >here<) NOTHING"
Last edited by Moondog55; 14th February 2020 at 05:31 AM. Reason: Additional thoughts
|14th February 2020, 06:03 AM||#8|
Join Date: Aug 2008
Location: Portsmouth UK
As Sonce says, you really must work out what the filter is and how the speakers are wired.
Since this is a WWMTM, you need to know if the drivers are wired series or parallel.
I'd guess the mids are wired series at 4 ohms each, to make 8 ohms. The woofers, I can't guess.
This is a glorified 8" plus 5" plus 1" 3 way, like Troels Gravesen's fine SEAS 3 way Classic:
Before you go running around looking for new drivers, the greatest improvement will come from a good crossover. It is easy to convert a given circuit for multiple drivers and that should be your approach.
Job 1: Trace the existing crossover and find out if the basses are series or parallel wired. Note the polarity of the drivers too. 3 ways often mix it up.
Best Regards from Steve in Portsmouth, UK.
|14th February 2020, 02:19 PM||#9|
Join Date: Feb 2020
Althought I'm still interested to find out to which extent I could possibly improve the audio coming from these, so I'll give it a shot and see how far I can come.
As for the X-change, I could very well remove it if designing a completely new crossover, I mean why bother with a X-change when you can design a crossover for my room and my room alone?
Tri-amping is out of the question I think, I need a passive crossover to go along with my STR-DN1080 130W/channel home cinema receiver, I don't have the space for any more amplifiers.
Yes, that's right, I want to improve these speakers for movies first hand, second comes music, I'll just chime in on FLAC/DSD at times.
Yes, the tweeter is certainly the best change here, however I am still very curious about finding out of I can improve the midrange too, I see modifying the enclosure/enclosures as a part of the challenge to improve the audio if needs be.
I don't want to build my own enclosures for now, maybe next time.
Yes, when I talked about impedance measuring I refered to using a multimeter, maybe not the best way to do it, better just refer to the nominal impedence rated by the manufacturer.
UMIK-1 I will certainly buy, DATS is a nice recommendation, I see that DATS V3 just got released, I'll look into it, thank you!
By accounting for the room frequency response in a passive crossover I would get the best possible audio out of the speakers in the very room I decide to measure in, no?
Otherwise I would have to use more software based EQ and that's worse than doing the EQ with hardware in the crossover, yes/no?
I wouldn't really modify the current crossover to accomodate for an improved audio with the current tweeter, because the tweeter itself is probably very poor, as even stated by the reseller (it often blows with high volume).
I would much rather change the tweeter, and then adjust in the crossover for that, no point spending time adjusting for something that's not worth adjusting, IMHO.
Draw the crossover schematic and post it here
Yes, this is very tricky, I took one of the speakers apart, and I tried to follow the circuits by continuity, but it's rather hopeless as the PCB's are multi-layered and you don't really know if some components are wired in parallel to ruin the measurements.
I certainly tried to measure, but it's hopeless, it's pretty much impossible to trace, you would need to un-solder every component and open the PCB to really find out how it's wired, you can't see any wiring paths on the PCB.
However, I took note of the components.
There are two PCB's, one for HF, one for LF.
The HF PCB has the following components:
1x CYC CD71 100V 100uF
1x CYC CD71 100V 5.6uF
1x CYC MKT J250V 4.7uF
1x Solid-Core Inductor 1.5mH 0.45 Ohm (Midrange, manufacturer says)
1x Air-Core Inductor 0.25mH 0.95 Ohm (Tweeter, manufacturer says)
The LF PCB has the following components:
1x CYC NP 100V 6,8uF
1x Solid-Core Inductor 3mH 0.48 Ohm (Woofers, manufacturer says)
1x 5W4R7J Resistor
The X-change terminal has the following components:
1x 5W2R2J Resistor
1x 5W1RJ Resistor
When not using the X-change, i.e. unplugged, both of these resistors are utilized and affects the 4-20kHz range (i.e the tweeter most likely, haven't checked physically in the crossover).
For a +2dB boost in the X-change, the 5W2R2J is bypassed.
For a 0dB difference, the 5W1RJ is bypassed.
How would I go about reverse engineering the crossover?
It's pretty much impossible to figure out how it's wired?
I'm using the Sony STR-DN1080 home cinema receiver, as I will mostly dedicate these speakers towards movies, occasionally I would put on some FLAC/DSD.
It's rated 130W per channel, 6-16 Ohms.
I more dampening I understand is a pretty simple fix, the speaker is originally based a vented design, thus the lack of dampening material on certain inside walls, more dampening is required when using a sealed design I take it.
Below you'll find what's dampened and not, currently - sketch is from the side of the speaker.
Green is where there is dampening, red is where there's not.
+ Side Walls in GREEN means there is dampening on the side walls.
+ Side Walls in RED means there is no dampening on the side walls.
Plugging the ports definitely tightened up the bass, I much prefer this sound, and leave the lower bass handling to my active subwoofers which also are sealed, hence why I am looking to redesign these speakers for a sealed operation.
UMIK-1 I will get, thanks for the recommendation.
I tried VituixCAD, I much prefer Xsim due to the larger crossover schematic window, I'll look into REW and ARTA, and I will most likely purchase DATS V3.
I also like the idea of fiddling with the sound with a crossover.
Thanks for your input!
For padding/dampening, look at the below picture, it's a side view of the cabinet:
Green is where there is dampening, red is where there's not.
+ Side Walls in GREEN means there is dampening on the side walls.
+ Side Walls in RED means there is no dampening on the side walls.
The current dampening material is synthetic I believe.
I have dual 10" sealed active subwoofers from 30-180hz.
Crossover possible from 40-180hz.
The midrange drivers are definitely not sealed, they're open-back drivers, so are the woofers, only the tweeter is sealed back.
Midrange drivers are in a separate MTM enclosure, just as you mentioned.
Could I improve the dampening here and add dampening to top and bottom of the MTM compartment?
Why did the manufacturer leave top and bottom naked?
Tweeter - Parallel (6 Ohm driver)
Midrange - Series (4 Ohm drivers)
Woofer - Parallel (8 Ohm drivers)
This leaves the tweeter at 6 Ohm, not accounting for the crossover (see the crossover components in the FOURTH quote in this post).
Midrange is wired in series to 8 Ohm.
Woofers are in parallel to eachother and makes for a 4 Ohm load, there is also a resistor here (5W4R7J) however I'm unsure what to make of that as the crossover design and schematics are unknown, again see the FOURTH quote in this post).
Could you ellaborate on how to reverse engineer and determine how the crossover circuitry looks like?
I tried measuring continuity but it's impossible since you don't know which components might be wired in parallel to others.
There are two PCB's, HF/LF, both have multi-layered PCB design so the circuit paths are impossible to see, you would have to open up the PCB (impossible) to see the wiring.
About the polarity of the drivers, could you expain some more?
I'm much interested in finding out, but since the crossover is hard to trace, I would need some further advice on this point, thank you.
Further on I have some questions about the internal wiring to the speakers, this is what I could see inside the cabinet:
Tweeter: 20AWG, non-golden cable shoes, ordinary copper wiring.
Midrange: 18AWG, non-golden cable shoes, ordinary copper wiring.
Woofers: 18AWG, non-golden cable shoes, ordinary copper wiring.
Is there an audio quality increase from using a different gauge wiring for the drivers, if so, which and why?
Would there be a benefit of using Oxygen-Free-Copper (OFC) cables or just better HiFi cables/wiring internally?
Gold-plated cable shoes, or better off just soldering directly with 9,5% silver solder?
All speaker terminals are non-gold plated.
Thanks for your reply!
Last edited by Vitus; 14th February 2020 at 02:49 PM.
|14th February 2020, 05:54 PM||#10|
Join Date: Oct 2012
If you're willing to learn, what you are proposing looks doable to me. This thread should help: So you want to design your own speakers from scratch
Probably most important is to learn how to properly take frequency and impedance measurements because if you can do this right, it's pretty easy for others to use those files and help you design the xo's.
For FR measurements - White paper: Accurate in-room frequency response measurements
How to find the relative acoustic centers is vital as well.
To start with, you can actually use an AV receiver's measurement mic with free REW software if your computer's soundcard allows it (mostly yes for older desktops but no for laptops - laptops usually require a separate soundcard). A better mic can be purchased later if desired.
For impedance DATS will certainly work but you can also use a little homemade jig with REW to get the job done as well.
Given all of that, I would indeed practice on your existing speakers and perhaps correct any glaring xo problems to start off with. You may actually be able to improve those quite a bit. Or maybe not. Regardless, you must have your woofers' FR and impedance measurements in the cabinets in order to work out any simulations with new drivers.
But you've got 13L for your mids to work in and that should be fine for 2 of the AC 130-MKII's. Trouble is that that driver's FR starts falling fairly early at about 1600Hz which doesn't leave a lot of room to play with at the xo point. I might instead choose the AC-130F1 which has a more extended FR and should be easier to work with. It's also used in the well known Continuum speakers by Jeff Bagby.
Potentially, your biggest problem is matching the existing woofer's sensitivity with the new MTM you want to build. Likely though that if your current speaker's sensitivity is below 90dB, that shouldn't be a problem. More than likely, you'll instead have to pad 2 of those mids in parallel down a fair amount to match the woofers instead.
Personally for this kind of learning project, I might choose less expensive drivers but I'm assuming you are looking at the AC's because they will fit your existing cutouts. There are ways to possibly get around that but if your budget allows for the AC's you are looking at, well then by all means proceed. With the caveat of course, it's always best to simulate the whole speaker response before buying any new drivers.
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