10F/8424 & RS225-8 FAST / WAW Ref Monitor

nikpolini

Member
2019-04-10 12:50 am
HI X.
Just a quick one hopefully, can the RS100 be used as a direct replacement for the 10F? I see you have an XO for the RS100, but I note the driver is the 4 ohm and all the other values have changed too... I already have the XO build for the 10F...

Only reason I ask, is I have both the 10F and RS100 on hand, and the RS100 looks cooler, ie, matches the RS225 look...(better WAF?)

Thanks.
Nik.
 

nikpolini

Member
2019-04-10 12:50 am
Yes, I think so to: I have just put the 10F into my PC speaker case that had the RS100, I notice the 10F is much brighter, although lacking in bass compared to the rs100, not a problem in the TL, but as stand alone full range, I think the rs100 sound a bit fuller....

Ill run the 10F in a bit like this...
 

nikpolini

Member
2019-04-10 12:50 am
PXL_20220718_060002375.jpg

PXL_20220721_082940482.MP.jpg

Making progress...
 
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Hi Folks,
I have some good news for those of you who may have wanted to pursue this speaker but felt that the cost of the 10F was prohibitive. Recently, Keantoken has been working on optimizing a crossover for this speaker specifically tweaked for the very good and affordable TC9FD. Keantoken happened upon a set of cabinets built by TubaV locally in Texas with a crossover (based on the 10F) and built with a set of TC9FD but no woofers. I donated Keantoken a set of new RS225-8’s and he quickly went to work on refining the sound quality. It’s quite impressive what he has come up with after many hours of careful measurements, tweaking, and auditioning. His work has paid off and what I am seeing is possible with this speaker and a $20 TC9FD is quite amazing. Due to his room size (small) and the height of his speaker stands, he chose to use the speakers with the tweeter on top, but microphone axis is still on the woofer. Here is a photo of his setup and playing with some foam padding behind the speaker to reduce wall reflections:
1658408790578.png

What Keantoken was working on a lot was a strange anomaly around 2kHz which is mostly the result of diffraction from the baffle and the woofer. The treatment for this was to add a 1mH inductor after the main 4mH inductor (in this case, an iron core that has lower DCR and is less expensive). The 4.4uF cap was reduced in value and the 0.5ohm shunt resistor deleted. There was also some adjustment to the TC9FD high pass capacitor and resistors. I’ll let him post the final schematic when he is done but if you look at his measured response, it is quite impressively smooth. The step response looks very clean. Here is a closeup of the various tweaks to the response near 2kHz. The orange curve with a dip was the original XO and the cyan colored curve is the modified XO:
1658409530410.jpeg

1658409077741.png

A big thanks to Keantoken for taking the time to do this - and I’ll let him share more details on the final XO schematic mods. I am thinking perhaps the woofer filter mods may be applicable to those who are using the 10F even. The graph above is truly reference monitor quality. Based on the measured curves… It will play music faithfully and neutrally and have great transient snap for percussion instruments. The imaging and sound stage will be top notch. Looking forward to the final update on the XO and listening impressions from Keantoken.
 
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I will add some notes. First of all, I have typically used 5-cycle FDW in my measurements for this speaker since the listening position is further away and more subject to reflections. My default is 10-cycle FDW.


The first plot with the red circle is a fairly early test of the crossover mod with a crude mic placement, but shows the basic effect of varying a woofer inductor added to the crossover right in series with the speaker. Changing the woofer capacitor was needed to achieve the full effect because this inductor with the capacitor compensates the woofer null thereby improving SPL at 2-3KHz, which is a region also affected by a diffraction null, and these effects together caused suppressed output in this range. In my listening the 2-3KHz region is important for the sense of proximity to voices and sounds, for shakers in music, realistic breathiness in vocals, correct snap of drums and dropped objects. Also provides bite in instruments like mildly distorted guitar.

2-3KHz is the region of the second harmonics of upper vocals, so when this region is suppressed vocals can sound marble-mouthed, even to the point of discomfort.

The impulse response was taken about 32 inches away and off-axis. It wasn't intentional but it ended up being the ideal position for getting a good looking impulse response. This position is a bit too far off-axis for me in that the highs are rolled off, but it also dodges the diffraction that is due to the tweeter being centered between 3 edges, so shows what this woofer/tweeter/crossover are capable of, in principle.

Here is an off-axis measurement I made.

1658411766938.png


As you go off-axis, the 2 octaves around 1KHz drop as well as everything above 3KHz. The curves bunch up at 2-3KHz because in addition to being where the diffraction null and woofer nulls affect the response, it is also where the tweeter takes over with better dispersion than the woofer. So you have this interesting confluence of 3 different issues happening in the same frequency range (actually 4). Too far off-axis and 2-3KHz actually becomes a hump in the response.

As you move away from the speaker, you get more treble because you end up more on-axis to the tweeter. In terms of listening axis, toe out affects the mids to highs balance and speaker tilt/elevation affects the mids to bass balance as well as the uppermost treble.

You would think that you could tilt and toe the speaker to dial in the sound perfectly, but I have found there is really only one ideal listening axis and it doesn't really change with the crossover. The photo I took that XRK posted shows what the speaker looks like when you are on the listening axis. Crossover changes didn't really change the axis much. If anything, crossover changes were an improvement mainly when they allowed me to use this listening position. So you take the best listening position and the best crossover and you usually end up with something quite nice.

I think the listening axis is locked in because of the effect of diffraction on the tweeter. Too on-axis sounds harsh and shows a peak at 3.5KHz. Too off-axis sounds muffled because the tweeter is rolling off and also the majority of energy is going into room reflections.

Diffraction is really only a convenient explanation for the issue, which was also an effect of the woofer null. The diffraction peak at 3.5KHz happens to boost a resonance in the spectral decay at that same frequency... So we have a woofer null, diffraction from 3 edges, a dispersion peak, and a cone resonance occurring in the same frequency range. I'm doing all I can to tame this beast without changing the physical design...
 
I am not sure if this is the final XO that Keantoken ended up with but it shows the relatively small changes to the woofer circuit. On the use of the TC9FD as a tweeter it seems changing the original XO schematic C1 from 60uF to about a 30uF cap and changing the original XO schematic R1 to about 3.0ohms will do the trick. On the woofer, a 4mH iron core inductor followed by a 1mH (air core?) and dropping the cap from 4.4uF to 2.2uF yielded improvements. This is a nice result for a TC9FD/RS225-8 specific implementation of the this FAST/WAW speaker. It remains in the same cabinet baffle geometry and is still 1st order transient perfect.

This is the revised crossover by Keantoken and C2 and C4 can be replaced with equivalent 30.3uF and R1 and R6 can be replaced with 3.0ohms:
1658427849709.png
 
When I got these speaker boxes and was gifted with the woofers to put in them, I was excited to finally hear a design vetted by the forum. I was not expecting to be so critical once I heard them. If the original design sounded great, then the TC9FD is probably not like the 10f at all.

In my case the treble was way too soft, the midbass was absent and the mids were overblown and marble-mouthed. The reason is kind of convoluted. The TC9FD has less sensitivity than the 10f but has a descending response from the bass whereas the 10f has a well damped rising bass response. In the case of the TC9FD this means the drivers cancel in the midbass and we lose it. When we raise the level of the tweeter to bring the highs to the level of the 10f, the cancellation gets worse. Both these issues together mean that ultimately you end up with boosted mids around 1KHz if you try and reach a compromise. This is also where the natural baffle step hump is... So the crossover really needed redone.

I suspect that the original suffers from this issue just to a lesser degree. I'm also extremely curious whether my crossover would change if I had the baffle with the offset tweeter...

I must have done hundreds of measurements, maybe even thousands by now. And in between those bursts of measurements, I was listening. It's not as if I am just trying to create a flat response or get a perfect impulse response. That is a good target or starting point, but despite my best efforts I have to allow some departures from what is hypothetically accurate, in order to make a sound that me and my weary test subjects (family) actually want to listen to, and resembles what instruments might actually sound like.

In this case I think it may have a lot to do with the ringing of the tweeter at 3.5KHz in combination with the diffraction from 3 baffle edges at the same distance. With my current preferred crossover this region ended up suppressed, which suggests that unevenly dispersive ringing is far worse than a deviation from a straight line in the step response.

As much as I like the idea of a good step response and time alignment, I only view that as a starting point. If the result doesn't sound good, adjustments have to be made. To come up with a good step response chart and then say I was finished would be ignoring a great deal of my own experience listening to my modifications.

But ultimately I don't have a bucket full of inductors to test with, and my design may be as much a result of my flawed listening environment as it is genuine problem solving. It would be better at this point for someone to replicate my work and add their observations, because it's not obvious whether I'm improving it at this point or just changing the flavor. And actually I need a long break. I've actually spent many, many hours on this. Here is where I'm at:

TC9FD WAW crossover schematic 2022-7-25.png


All the extra tweeter components were unnecessary as far as I can tell, and don't seem to be needed for the TC9FD. The treble was rolled off a bit in the 10f crossover which was not an advantage here where the diffraction means we need to be off-axis and still have good treble response.

Changing the value of R5 has a very interesting effect on the sound...

I don't know what this crossover would do for the 10f, but I would use the woofer portion of this crossover with either tweeter. I think the step response could likely be improved. The step response of this crossover is pretty good even though it's not the best I achieved, but it sounds so much better than the version with the best step response.

The imaging is unreal at times. All of the music sounds better, it is smooth yet detailed, all the instruments can be heard when they were intended to be heard and not climbing over each other. The imaging is incredibly solid, not exaggerated at all, just very life-like, as if something is really there. Especially with nature sounds.
 
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I won't say every one of those measurements were meaningful. Some of it was just fun... And also I probably took a lot of measurements because I'm still learning and it's not always obvious what the measurements show. But I definitely had an intention for everything I did.

As much time as I have put into this there is still uncharted territory. For instance, it's possible the TC9FD is underdamped and is doing something funny to the midbass that doesn't show up in room measurements. I heard a difference in the midbass when going to the simpler tweeter circuit, whereas the original tweeter circuit had a lower impedance to the tweeter. I did not focus on this because subjectively it wasn't nearly as important as as getting the other parts right. But there could be some improvements to be made here. Would they hold in a different room though?

Also finer adjustments to C3 could be explored, with adequate capacitor tolerances.
 
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There was a link to the BOM for the XO in post 1. But it seems since we migrated to the new forum software, the link is broken.

Searching in this thread shows it as post 1529. The BOM is below:


Product Name Sku Qty Price Total
Dayton Audio DNR-4.7 4.7 Ohm 10W Precision Audio Grade Resistor 004-4.7 4 $1.09 $4.36
Dayton Audio DMPC-27 27uF 250V Polypropylene Capacitor 027-439 4 $8.58 $34.32
Dayton Audio DNR-0.51 0.51 Ohm 10W Precision Audio Grade Resistor 004-.51 2 $1.38 $2.76
Dayton Audio DNR-10 10 Ohm 10W Precision Audio Grade Resistor 004-10 2 $1.38 $2.76
Dayton Audio DMPC-2.2 2.2uF 250V Polypropylene Capacitor 027-415 2 $1.87 $3.74
Dayton Audio DMPC-6.8 6.8uF 250V Polypropylene Capacitor 027-424 2 $2.75 $5.50
Jantzen Audio 4.0mH 18 AWG Air Core Inductor Crossover Coil 255-280 2 $20.91 $41.82

* note that there is a typo, you need qnty 4 of thr
 
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There was a link to the BOM for the XO in post 1. But it seems since we migrated to the new forum software, the link is broken.

Searching in this thread shows it as post 1529. The BOM is below:


Product Name Sku Qty Price Total
Dayton Audio DNR-4.7 4.7 Ohm 10W Precision Audio Grade Resistor 004-4.7 4 $1.09 $4.36
Dayton Audio DMPC-27 27uF 250V Polypropylene Capacitor 027-439 4 $8.58 $34.32
Dayton Audio DNR-0.51 0.51 Ohm 10W Precision Audio Grade Resistor 004-.51 2 $1.38 $2.76
Dayton Audio DNR-10 10 Ohm 10W Precision Audio Grade Resistor 004-10 2 $1.38 $2.76
Dayton Audio DMPC-2.2 2.2uF 250V Polypropylene Capacitor 027-415 2 $1.87 $3.74
Dayton Audio DMPC-6.8 6.8uF 250V Polypropylene Capacitor 027-424 2 $2.75 $5.50
Jantzen Audio 4.0mH 18 AWG Air Core Inductor Crossover Coil 255-280 2 $20.91 $41.82

* note that there is a typo, you need qnty 4 of thr
Thanks XRK. I don’t actually know the term BOM but now that I’m thinking about it I’m assume it means Bill of Materials?
This is really helpful. I guess I need to figure out all the liner etc as well and put a final price to these for “the decision”. Cheers!
 
Yes, BOM is bill of materials. This is the the crossover parts. I have a PCB if you don’t feel like point to point soldering the XO. The cost of the eggcrate foam is typically $15 to $20 from Amazon. The soccer cones are $15 for a set of 12 I think. The woofers are $90 ea. The 10F is $120ea. You can try other full ranges like B80 or TC9FD and specific crossovers for those are now available. The TL cabinet is probably 1.5 sheets of 5x5 3/4in Baltic Birch ply and that can set you back $200+ and with the Ukraine war and Russia it’s hard to find. Binding post terminals another $25 for good ones. Noico butyl autosound vibration damping sheets $30. I seem to recall a full build is circa $700 to $800 budget for the TL. The sealed one can be done with a single sheet of BB ply for sure.

Good luck!

edit on previous post - you need 4 of the 2.2uF caps.
 
Interested in building these sealed as bookshelves. Are they good at all for short distance listening? 80cm - 1.2m away from the ears (desktop).

They sound best further away than you would use a bookshelf speaker. Too close and you will hear the drivers playing separately. 120cm would be more like a minimum distance for these speakers.
 
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