Crossover upgrade / modification - Monitor 10 Series II

McLoki

Ok, all the recent talk about upgrades to crossovers has me ready to run out and try it. Given that I got a decent deal on my Monitor 10's I am willing to spend the money for a decent upgrade (planning on sonic caps and mills resistors). 2 big questions.....

1. I have read before that there is no need to upgrade the coils in the Monitor 10's. Why is this? Just a cost to benefit difference or the ones in the speaker are really nice. I was going to go through Sonic Craft for my parts and they seem to think their inductors are worth purchasing. Is it just not worth it?

2. There has been some talk that the Monitor 10's have imaging issues due to their side by side woofers. (hence the monitor 7's being considered by some the speakers to have in this line) My question is, has anyone tried a 2.5way crossover similar to the LSi9's? Basically cross one of the woofers over lower than the other. Would that potentially solve the imaging issue? I was planning to cross over one of the woofers exactly as it is currently designed in the Monitor 10 series II, and just set up the other woofer to cross over at the same values as the LSi9 bass only woofer. (About 200hz)

It sounds like a fun project to try, but I don't really want to screw up the sound of my speakers to dramatically either.

Has anyone tried this before or have any words of advice. I am willing to scrap the plan and just do a standard crossover upgrade, but it is kind of fun to venture into new waters every once in awhile....

Michael

MillerLiteScott

The imaging issue has more to do with the side by side design of the mid-bass drivers rather than the crossover points. A TM or MTM has a more focused and aligned image than the M 10's side by side design.

Face

I would keep it simple and just upgrade the caps and resistors. Changing inductors may not make a noticeable difference.

Your second question is pretty interesting. Taking a wild guess, you would have to remove the 12uf cap that bypasses the resistor in the HF circuit, then run a filter between the two woofers(large inductor and large cap), greatly increasing the cost of the upgrade. It's doable, but I don't know how it would sound.

jon s

maybe u shud look at the crossover design for the RTA-12B... it uses a cascaded crossover design. one mid-bass driver crosses over at 600Hz and the other 2 kHz. doesn't look too complex but going all Sonicaps (14 of them in the 12B vs 6 on the 10B) gonna cost about $500... A lot more than just upgrading the 10B crossover itself.

on a side note, I just upgraded the crossover on my 10Bs using the Jantzen crosscaps. while it was a cheap upgrade it did make a marked improvement in the soundstage and focus in the music. granted that the sonicaps will make a difference, but you are getting to the point of diminishing returns... where you spend twice as much for a 10-20% improvement... on a pair of 20 year old speakers... if the speakers were a more expensive polk model, i would consider spending more but it's all relative (it did not make sense to spend $300 to upgrade a pair of $50 speakers)... you are just going to have to make that decision yourself.

McLoki

jon s wrote: »

if the speakers were a more expensive polk model, i would consider spending more but it's all relative (it did not make sense to spend $300 to upgrade a pair of $50 speakers)... you are just going to have to make that decision yourself.

I am not looking at them as a lower polk model or a pair of $50 speakers. I more look at it as something that when I am done will closely rival if not exceed my LSi15's with a retail price of $1,849.95. (a comparison that I believe you made as well and mentioned that they got very close. - Just a different way of looking at things I guess...)

Here is the cost breakout as I have it calculated....

[PHP] Sonicaps Solen
C1 capacitor 16uf $24.10 $8.45
C2 capacitor 27uf $34.80 $12.48
C3 capacitor 12uf $19.60 $7.03
R1 Resistor 2.7ohms $3.50 $7.00

Total / speaker $82.00 $34.96
Total / Project $164.00 $69.92[/PHP]

Note:

• Have to add 1.2 and 1.5 resistors as Parts Express does not carry 2.7's in mills. Hence the double cost for the resistors from Parts Express.
• All caps are exact replacement values per schematic. Sonic Craft does not offer a 16uf cap, but said I could get a 15uf or 17uf Cap and they would find one that closely matches the 16uf I need. Excellent service if you ask me.

Total speaker cost after the upgrade would still be lower than most of the monitor series, let alone the LSi's.

I am just trying to decide what to purchase before I place my order.

If I replace the inductors, my cost would shoot up quite a bit ($43.87 per speaker or the project cost would go up by $87.74 totaling out at $251.74) Compared to the LSi15's I am trying to beat, still a great price.

These prices do not include the 2.5 cascade array. I may have to skip it this upgrade and once complete if I am still not happy, take up the option then.

Thoughts anyone?

embo

If you sucumb to the a total upgrade of the crossover and purchase Alpha Core foil inductors from Sonic Craft, keep in mind the lower DCR of the foil inductor. This may necessitate an additional resistor placed in series with the inductor. First, you will have to confirm the inductance of each inductor in order to get the right value. That's fairly simple if you have an LCR meter. If not, you can biuld an inductance adapter for your digital volt meter - http://www.rainbowkits.com/. Complete kit with case is about $32, includes shipping. It is much harder to measure the DCR of an inductor which will run from ~0.1-10 ohms. If you attempt to simply measure such low resistances with a digital volt meter it will fail to provide a stable reading. The resistance from your test leads will give dominate the measurement. I am currently building a milliohm adapter for a digital volt meter. The schematic I am following is provided at http://members.tripod.com/~baec/DEC90/ohmeter.htm

I am in the beginnings of upgrading my SDA1 Signature Edition. I purchased the caps and resistors from Sonic Craft during their 15% off sale last month. I have thought about uprading the inductors as well; but I have decided to put that off for now. Since, I have the inductors out for the cap and resistor upgrade, I thought I would document their inductance and DCR before proceeding.

Face

Also keep in mind, Alpha Core inductors will be larger than the ones they're replacing, sometimes MUCH larger.`

geoff727

Face wrote: »

Also keep in mind, Alpha Core inductors will be larger than the ones they're replacing, sometimes MUCH larger.`

Ya, no doubt there. I bought some from SONICCRAFT to replace some 3.5mh in a pair of Infinity's. I think they weigh more than the cat, and cost about as much as the last vet bill.

McLoki, did Jeff mention anything about trying to get a close match in the DCR of the coils, from the originals to the Alpha-Core's? Or, if needed, what series resistor he would recommend? I'm also curious what sonic benefits he said would be gained in going to the Alpha-Core's from the stock air-cores.

I guess one of us just oughta do it, report back, and then everyone will know!

Face

The Alpha Core inductors will lower distortion. I'm not sure of any other benefits.

I can say I love their speaker cables though.

McLoki

geoff727 wrote: »

McLoki, did Jeff mention anything about trying to get a close match in the DCR of the coils, from the originals to the Alpha-Core's? Or, if needed, what series resistor he would recommend? I'm also curious what sonic benefits he said would be gained in going to the Alpha-Core's from the stock air-cores.

He has not yet. (I called and asked about the 16uf cap and that was when they told me they could get a 15uf or 17uf that was really close to the 16uf I needed.) I have sent my project parameters along with a schematic to sonicraft asking their opinion on parts to replace and mentioned that I am willing to replace the inductors if they feel the sonic benefits would be worthwile compared to what comes in the 10's I have. I have not heard back from them on it yet though. When I do, I will share what I have learned.

Obviously, the inductor upgrade is more involved than I thought. From my limited understanding, I thought you wanted the mH values to be the same with the lowest resistance you can get (hence the heavier guage wire). Apparently, this was my own ignorace showing through. If determined to be worth it, I will replace the parts, but I am a long way from a speaker or crossover designer. (hence dropping the 2.5 way crossover idea for now)

Anyway - sounds like it will be a fun project. Can't wait to get started, Just waiting for a few more responses (from here and sonic craft) and I will order the parts.

I guess one of us just oughta do it, report back, and then everyone will know!

Maybe the way to go about it (even if (especially if) the inductors do get replaced) is to replace the caps and resistors first - break them in, and then do another upgrade later for the inductors. I think that may be the only way to tell what part of the sound change was due to the inductor upgrade. (since most do not do it) Might be best for all of us that way (and I could order parts sooner). What do you think?

geoff727

McLoki wrote: »

...but I am a long way from a speaker or crossover designer.

Me too, unfortunately.

McLoki wrote: »

From my limited understanding, I thought you wanted the mH values to be the same with the lowest resistance you can get (hence the heavier guage wire).

I think if the DCR of the new coil is substantially lower than the DCR of the original, then it could result in an output volume mismatch between the individual drivers. Specifically, the mid/bass driver (and hence, the passive radiator) would play a little louder- and, the overall impedance of the speaker would drop a bit too. Of course, there's that resistor in the tweeter circuit which could be tailored to a different value, too. But, the inductance values of the mid/bass series inductor are not very big. So, the coils aren't real big, and the DCR shouldn't be real big. So, in my thinking, there shouldn't be a real big DCR mismatch between the old and a new AlphaCore, either.

McLoki wrote: »

Maybe the way to go about it (even if (especially if) the inductors do get replaced) is to replace the caps and resistors first - break them in, and then do another upgrade later for the inductors. I think that may be the only way to tell what part of the sound change was due to the inductor upgrade. (since most do not do it) Might be best for all of us that way (and I could order parts sooner). What do you think?

If you don't do it, I am eyeing the coils in my 2.3tl's. Might not be for another year or two (3 Infinity projects to go), but I'd like to try the AlphaCore's in them.

ben62670

I would stick with just the caps, and resistors. If you change inductors you are going to change the DCR. This can throw off your XO's phase, and actual XO point.
Ben

Face

For reference sake, I believe that's a 12 ga, 6.8 mH inductor.

McLoki

Still have not heard from Sonic Craft, but will be purchasing just the caps and resistors in the next week or so. Should I also get solder from them or is the Radio Shack silver solder I have good enough? How about short lengths of wire to hook up the speakers internally? (I could just use some generic 14ga. I have laying around I guess....)

Looking forward to the project.

Michael

Face

I'm a fan of Cardas and WBT solder. IMO, radio shack's silver solder is junk, it doesn't stick to anything but carpet.

Btw, Jeff is a busy guy, it usually takes him a few days to get back to you. But when you have him on the phone, he'll spend as much time with you as needed.

McLoki

Finally heard back from Sonic Craft. Here was their reply to my questions. (I sent them a schematic for the speaker as well)

Michael,

The biggest bang for the buck is the capacitors. The resisters follow because of their price. No need to change L1, but going to a 12ga. foil inductor at L2 would yield deeper cleaner bass extension with faster tighter midbass. However, if you were will to spend the coin on the coils, I recommend substituting Sonicap Platinums in the place of the Sonicap Gen 2s below.

Recommendations:

-Replace C1, C2, and C3 with Sonicap G1. A custom value of 16uF is no problem. Just price a 17uF.
-Bypass C1 and C3 with a 0.10uF/200V Sonicap G2 -Replace R1 with a Mills MRA-12 instead of a MRA-5, not because you need the power handling. The sound of the MRA-12 is more conducive to the timbre of your particular tweeter.

Current prices are here:

http://www.soniccraft.com/sonicaps.htm
http://www.soniccraft.com/sonicap_gen_2.htm
http://www.soniccraft.com/mills_resistors.htm
http://www.soniccraft.com/sonicap_platinum.htm
http://www.soniccraft.com/products/inductors/alphacore_inductors.htm

Best regards,
Jeff

Do you all recommend the bypass caps as well? If so, I think I will just go with the Gen 1 and Gen 2 like he recommends and skip the platinums and inductor upgrade for now.

If that sounds like a good plan I will get the parts ordered this week.

Michael

dcmeigs

I recommend you search the forum for comments on the platinum bypass. I have not used them myself, but many of those who did later removed them. Unpleasant artifacts was the most common complaint, if I remember correctly.

McLoki

So, is that the nature of the .1uf bypass cap or the platinums?

I take it I would be better of staying with the schematic and if I am unhappy with the highs - upgrade to the RDO-198's?

Thanks for the heads up.

Michael

Face

There are some inductor upgrades if you want to go to the RD0-198. Have you heard 198's yet? They're very smooth, my favorite from the vintage/replacement tweeters.

McLoki

No, I have never heard the 198's. I think I may be happy I haven't because it would just be more money I end up pouring into these speakers.

I am enjoying the 2500 tweeter alot. It provides quite a different sound than my LSi15's. I can't wait to compare them when I get the new crossover in place.