Erse Super Q 17mh 16awg mod to SDA-2B TL's

DarqueKnight

One important performance parameter that is often overlooked is a component's transient response, or how it responds to very brief (on the order of milliseconds) peaks in current. Music signals consist of many transients that may be smeared or clipped off by unresponsive amplifiers and by lower grade electrical components (resistors, capacitors, inductors, etc.) in a speaker's crossover.

The largest SDA SRS's are rated for amplifier power of 1000 watts. Certainly, a continuous amplifier output power of 1000 watts would vaporize the crossover components and voice coils. However, transient peaks in this range can easily be accommodated. In fact, such transients contribute to the realism, sparkle and life-like qualities of recorded music. This quote is from a review of the original SDA SRS published in the November 1985 issue of Stereo Review (p. 90):

"Not surprisingly in view of its large driver complement and rated power-handling of 1,000 watts or more, the Polk SDA-SRS thrives on power levels that would vaporize some lesser designs. We ran out of power from our amplifier (one of the most powerful available for home use) when we attempted to reach the speaker's limits with 1,000 cycle tone bursts. At 100 Hz the amplifier clipped at 1,650 watts into 6 ohms, and at 1,000 Hz it clipped at 765 watts into 20 ohms. Only at 10,000 Hz, where presumably only one driver was in use, did we reach the limits of the speaker and the amplifier at about the same time-1,265 watts into 5 ohms."

My PS Audio Power Plant Premier (PPP) AC regenerator is rated for 50 amps peak current output. My Parasound Halo JC 1 monoblock amps are rated for 135 amps peak current. The JC 1's are plugged into the wall receptacle, which terminates a 20 amp circuit. However, that 20 amp circuit is capable of delivering the full rating of the house electrical service (200 amps) for fractions of a second. That is why the JC 1's sound excellent when plugged into the wall and sounded like crap when plugged into a PPP (wooly bass and loss of dynamics, detail, and clarity). The PPP simply cannot keep up with the frequent peak (transient) current demands of the JC 1.

With regard to SDA inductor selection, it might be prudent to consider the transient performance of various inductors. An inductor that might not saturate under continuous current conditions at normal listening levels might saturate during the frequent current peaks encountered when reproducing music with amplifiers of moderate to high power. The manufacturer of the inductor under consideration should be able to provide information on the transient performance of their parts, particularly if such parts are marketed specifically for loudspeaker crossover applications.

One general comment I'd like to reiterate about modifications is that they should be considered within the context of a product's original design goals. Often, the product that goes to market is a pale reflection of what the designer(s) originally created. Therefore, the product offered for sale is often not the "real" product originally designed. The economic realities of efficient and profitable manufacturing and meeting a price point often dictate many compromises. In such a case, if appropriate modifications are implemented under advisement of the product's design staff, and if such modifications remedy design compromises, then the commercial version is actually moved closer to the "real" product...which never made it to market. Polk Audio, PS Audio and Adcom are three companies that come to mind that have been very forthcoming and enthusiastic about recommending modifications to their products to remedy commercial cost cutting measures.

On the other hand, if modifications are implemented just to suit personal preference, then there is a high risk of ending up with something that strays far from the original design goals and which has severely compromised performance in one or more areas. However, such compromises might not be readily apparent to the ear.

This post is not meant to be critical of anyone's modification philosophy or practice. Every one is free to do whatever they want with their speakers. My goal here is to offer additional perspective.

DarqueKnight

OldmanSRS wrote: »

Install your 5% or 1% tolerance Erse inductors. If the bass sounds thin like I experienced, then what?

Thin bass might be due to more accurate reproduction by the loudspeaker. Clean, higher quality bass, with more speed and control, is often more likely to be felt rather than heard and to sound "thin" until you get used to it.

There is nothing wrong with adjusting the sound of your audio components to your personal preferences. However, some effort (measurement) should be made to determine if the "thin" bass is due to the removal of inaccurate resonances or due to an actual dip in response at certain bass frequencies.

audiocr381ve

Thanks for offering a different perspective DK. I really appreciate it.

Unfortunately, all I'm relying on is my background in music & recording. If it doesn't sound right, I like to think that I would know it lol. So far the difference is such a pleasant surprise. I popped in some Miles Davis this morning and was blown away. The best way to describe the change is that their is a "presence" in the music that was not there before. Saxophones & vocals have more body. I can actually hear upright bass notes now. It's a sweet change and the difference is dramatic, in a good way of course

OldmanSRS

DarqueKnight wrote: »

Thin bass might be due to more accurate reproduction by the loudspeaker. Clean, higher quality bass, with more speed and control, is often more likely to be felt rather than heard and to sound "thin" until you get used to it.

Agreed and it's there and it's wonderfull below 100 hz but it's also thin above 150 hz and I measured it. That's with a 17 +/- 5% mH Erse which falls within the range of the (16.8 mH) stock inductor.

inspiredsports

OldmanSRS wrote: »

Install your 5% or 1% tolerance Erse inductors. If the bass sounds thin like I experienced, then what?

Then what?

First, I don't believe they will sound bad.

I've stated that in my case this is an experiment, and I'll give the Erse Super Q's a long and fair audition, but (as I've also stated) will order 16mH 10 AWG Solens without reservation if the Super Q's don't exceed my expectations.

Last, I believe the Super Q's will be OK in a 500 W handling CRS/2B. If I owned 1,000 W capable SRS/1.2/1.2TL, I don't think I would use iron cores.

OldmanSRS

inspiredsports wrote: »

Then what?

First, I don't believe they will sound bad.

Last, I believe the Super Q's will be OK in a 500 W handling CRS/2B. If I owned 1,000 W capable SRS/1.2/1.2TL, I don't think I would use iron cores.

Awaiting your assessment.

They may be 1000W capable but 100W of clean power is enough for my ears and listening room.

evhudsons

VERY well said! Of course I wouldn't expect anything less from DK. Basically it seems there are basically two schools of thought here, one is to upgrade to what the designers wanted in a finished product, and the other is to continue to tweak and explore to see what else they are capable of doing. Without experimentation, we may not have had the very tweaks that are Polk approved. I'm just saying this in case anyone gets upset again. There are things in life we don't anticipate and most advice is given with that in mind. DK just explained pretty clearly some of the caveats to listen for, but also explained what the original intent may have been by the designers and so is helping to further this thread in experimentation.

This is just awesome. So thanks for all this info.

A question though, the CRS+ can handle 500 watts? That just seems like so much. Does that mean my still yet to arrive high current parasound amp rated at 205 watts can play well but handle occasional bursts up to 500 watts? Just curious..

inspiredsports

Good catch . . .

That made me dig out my old original point of purchase 1986/1987 Polk brochures that Audio Craft in Akron provided me when I bought my 2B's.

2A's/2B's are shown as 10-500 watts/channel

MY APOLOGIES: CRS's are shown as 10-200 watts/channel

I made the (bad) asssumption that because the driver complement is the same, the power handling capability would be the same, forgetting the smaller 10" passive and smaller cubic volume of the CRS.

inspiredsports

OldmanSRS wrote: »

Awaiting your assessment.

They may be 1000W capable but 100W of clean power is enough for my ears and listening room.

I placed them in circuit in a very temporary fashion last night. I'll be updating my personal "SDA-2B Crossover Parts List" thread within the next 10 day with impressions and lots of photos.

The sound right out of the box is stellar, but I want to closely monitor my amps as DCR at the speaker terminals dropped from 3.8 ohms with the stock inductors to 2.9 ohms with the Super Q's. I'm going to recheck my measurements with a fresh battery and another tester, but that's the early report.

This may be an application where Polk Cobra Cable with it's high resistance/capacitance (Doro, are they done yet ?? ) is actually a bonus. Or am I getting that backwards?

evhudsons

thanks for clarifying that about the crs, in case I go crazy one day and over power it. Most unlikely though, but it's nice to know the limits.

Not exactly within the thread, but last night I installed Larry's rings and the bass literally came to life, as did the whole speaker. It was dramatic. Now I'm rethinking the whole bass thing and really want to add the inductors somewhat soon.

Larry, you are a mad genius, as are some others on this forum! I knew the rings would help, but it is on par if not higher than the spikes as far as I can tell with these little speakers. They think they are much bigger now.

Once again, I'm breaking out new music to listen to all over again.

It was good doing that upgrade. Once I get my new amp power hooked up I can really compare. I think that once I put in the inductors I can be more critical overall, but the crs+ is now becoming more of a loudspeaker rather than bookshelf.

Phasewolf

Ok I really don't want to get my head bit off with this but. The one that was in the xo was a air core and there for could handle higher freq without saturation but with a iron core you would hit it fairly quickly. Would this http://search.digikey.com/us/en/products/FIT50-5/237-1186-ND/242598 work better sense it can handle higher freq with out issue? The dcr of the part is also super low and the cost at under 3 dollars would make it cheep one to try. If it would not work could someone tell me why.

OldmanSRS

Intuitively I would say it's not a good choice. That part is used to attenuate the high frequency (10 khz - 50 khz) in the DC output of switching power supplies and other applications where switching noise needs to be removed from circuits. No sure it is well suited for the very low audio range (10 hz - 1 Khz) that we are dealing with. Note is was tested at 10 khz and would probably saturate or perform poorly at much lower frequencies.

Mr. Bubbles

Phasewolf wrote: »

Ok I really don't want to get my head bit off with this but. The one that was in the xo was a air core and there for could handle higher freq without saturation but with a iron core you would hit it fairly quickly. Would this http://search.digikey.com/us/en/products/FIT50-5/237-1186-ND/242598 work better sense it can handle higher freq with out issue? The dcr of the part is also super low and the cost at under 3 dollars would make it cheep one to try. If it would not work could someone tell me why.

The coil you have supplied the link to has a micro rating for the inductance instead of milli (uH vs mH). Another way of saying what i think Oldman was saying is that these would not work because of the incorrect inductance. the frequency would be way too high. The circuit in question is operating below 200Hz and though iron and steel core inductors due have a risk of saturation and distortion from this saturation, the concern for this is somewhat less than it would be at higher frequencies. The inductor in the link you supply actually uses an iron core so it would therefore be susceptible to saturation just as any other iron or steel core inductor.

The design of the inductor should work fine, though i have never used a toroidal inductor in a passive crossover, so i am not familiar with their saturation or sound characteristics. Jantzen actually has a line of these.

evhudsons

I understand that the changing of the inductors would increase the risk of dropping the ohm load, but what is the effect of saturation on both equipment, and the sound? Would you hear saturation? I'm a true layman. I did look up some of this stuff on the internet so I'm not being lazy about learning, but I didn't see these two questions answered in a way I would understand. I'm sure it's such common knowledge that it is not mentioned much.

This is fascinating stuff. It makes me want to start taking classes to learn more. I know it could be another rabbit hole of gear in working on electronics, so I'm not going to go that route, but I want to learn more about how the speakers work. cool stuff.

OldmanSRS

oliverbubbles wrote: »

The coil you have supplied the link to has a micro rating for the inductance instead of milli (uH vs mH).

Good catch. It was before coffee and I did not notice the value was spec'd in uH as you noted. It definitely will not work with that value.

Above the point of saturation the inductor stops acting like an inductor and changes to a resistor (DCR only). In the SDA XO that means under the saturation point, the inductor absorbs the higher bass frequencies and above the saturation point, it will pass them starting with the peaks of the sine wave and more of the sine wave as the power level increases. It would sound like distortion or similar to clipping.

audiocr381ve

OldmanSRS, did you ever try going past 15 turns on your inductor? If so, what happened?

inspiredsports

evhudsons wrote: »

. . . I understand that the changing of the inductors would increase the risk of dropping the ohm load, but what is the effect of saturation on both equipment, and the sound? Would you hear saturation? . . .

It's early in my testing (about 60 hours and the first 12 were using my VTL tube amp) of Erse Super Q's in my 2B's, but I will throw this out.

First, I just got back my NAD 2600A amp that was at In House Stereo Repair for a tune-up.

The 2600 is capable of delivering a sustained 325 watts into a 2 ohm load, and has enough headroom to produce 1000 watts for transients into 2 ohms. The DCR now measures 2.9 ohms for the modded 2B's so the NAD is throwing some pretty high numbers into them.

So far I've push some very dynamic CD's into them at up to 102db in my listening position at 9 feet and centered. The sound quality is stunning. I don't like to listen much above 85db due to the hearing loss risks, but am trying to find the Erse's limitations and have not done so yet.

I don't know exactly what inductor saturation sounds like either, but so far I believe I would sustain brain damage before these things saturate.


NOTE to audiocre8ive: 16 mH is the proper value for SDA 2B's. I don't know if you are willing to send them back to Erse and have them properly unwound and measured, but that's what I would do

OldmanSRS

audiocr381ve wrote: »

OldmanSRS, did you ever try going past 15 turns on your inductor? If so, what happened?

I'm at 16 turns and holding. It sounds perfect to me. Removing turns decreases inductance and increases bass above 100 Hz to the SDA. If I had a way of measuring inductance easily I would check their value. To me, the stock 16.8 mH values sounded too warm and tubby to begin with so taking a few turns off a 17 mH to get the sound I want and observe the corresponding signal to the SDA is my approach.

audiocr381ve

inspiredsports wrote: »

It's early in my testing (about 60 hours and the first 12 were using my VTL tube amp) of Erse Super Q's in my 2B's, but I will throw this out.

First, I just got back my NAD 2600A amp that was at In House Stereo Repair for a tune-up.

The 2600 is capable of delivering a sustained 325 watts into a 2 ohm load, and has enough headroom to produce 1000 watts for transients into 2 ohms. The DCR now measures 2.9 ohms for the modded 2B's so the NAD is throwing some pretty high numbers into them.

So far I've push some very dynamic CD's into them at up to 102db in my listening position at 9 feet and centered. The sound quality is stunning. I don't like to listen much above 85db due to the hearing loss risks, but am trying to find the Erse's limitations and have not done so yet.

I don't know exactly what inductor saturation sounds like either, but so far I believe I would sustain brain damage before these things saturate.


NOTE to audiocre8ive: 16 mH is the proper value for SDA 2B's. I don't know if you are willing to send them back to Erse and have them properly unwound and measured, but that's what I would do

That's awesome man. I'm glad your enjoying the sound.

As far as sending them back, I really don't feel like there is a need to at this point. Everything sounds superb. I may get curious in the future but I really like the way things turned out.

audiocr381ve

OldmanSRS wrote: »

I'm at 16 turns and holding. It sounds perfect to me. Removing turns decreases inductance and increases bass above 100 Hz to the SDA. If I had a way of measuring inductance easily I would check their value. To me, the stock 16.8 mH values sounded too warm and tubby to begin with so taking a few turns off a 17 mH to get the sound I want and observe the corresponding signal to the SDA is my approach.

Do you know where you're at as far as inductance at 16 turns removed?

OldmanSRS

OldmanSRS wrote: »

If I had a way of measuring inductance easily I would check their value.

I don't have an inducance meter.

audiocr381ve

Gotcha.

Phasewolf

Yes I misses the value on that sorry about that. It was late and I was tired just thought it would be good to ask about.

inspiredsports

audiocr381ve wrote: »

Do you know where you're at as far as inductance at 16 turns removed?

Am I missing something here? I thought OldManSRS had 1.2's which originally had 16.8mH inductors and you have 2B's which originally had 16.0mH inductors. I don't see how the same unwinding formula would be perfect for both mH values.

audiocr381ve

inspiredsports wrote: »

Am I missing something here? I thought OldManSRS had 1.2's which originally had 16.8mH inductors and you have 2B's which originally had 16.0mH inductors. I don't see how the same unwinding formula would be perfect for both mH values.

No, you're right. Which is why I want to know where those turns took him. I'm testing between 10-20 turns right now. I may land somewhere between 15-20.

Michael8it

There seems to have been a lot of discussion on this thread about a ‘scientific’ approach and an experimental approach, and the arguments of both sides about unwinding an inductor by hand.
Having some knowledge of the fine tuning process, I thought I would chime in (musical pun intended).

Music is part science and part art. Stradivarius did not design his violins with a CAD program, yet nothing a CAD program can produce can equal a Stradivarius. Same holds true for 1940’s Martin guitars. Both of these were built by hand, and fine tuned by ear. The bracing, the woods used, the type of glue, everything was taken into consideration. The basic template was there for both, but the finished product was all done by ear. The same is still true for custom built acoustic instruments.

I recently had a 1924 Martin guitar complete rebuilt. The Luthier that did the work did some ‘fine tuning’ after it was assembled, matching the bass and treble sides, and the 90 year old guitar sounded fantastic.

What does all this have to do with crossovers? I’m so glad you asked! Every component in the crossover is +/- 5%, even the drivers. You cannot change the drivers actual values, and you cannot change the capacitors. Even if you replace them, you are still dealing with tolerances. The only thing you have left to tune is the inductor. You can manually change that value, and in doing so, you may find a ‘sweet spot’ where all the tolerances of that speaker come together ‘just right’.

What the designers intended on paper never makes it to production. The only way that would happen is if you tighten up the tolerances on all the components, which drives the cost exponentially higher. SO although some would argue that hand tuning an inductor is not scientific, and that you are changing what the designer(s) intended, I would argue the opposite: Although you are not doing the math, and for that matter may not even understand the math, it is in fact scientific. The reality is that the product we get at the store is not what the designer imagined – the designer based his math on a specific set of values, which your speaker does not have. The sound that is produced is the sum of all the components in the chain, and their tolerance affects that sound. In my 12B’s, I have 5 to 7 components in each driver chain, all with +/- 5% tolerances. That equals a total of a 25% total potential variance. The only component you really have to work with that you can change is the inductor. You may be .01 or even .1 (or more) off of what the ‘spec’ is, but if you ear tells you it works, that is the final authority.

So for what it is worth, that is my two cents.

OldmanSRS

Well said but how long do you burn-in a Martin guitar?

Shame on me.

inspiredsports

Michael8it wrote: »

There seems to have been a lot of discussion on this thread about a ?scientific? approach and an experimental approach, and the arguments of both sides about unwinding an inductor by hand.
Having some knowledge of the fine tuning process, I thought I would chime in (musical pun intended).

Music is part science and part art. Stradivarius did not design his violins with a CAD program, yet nothing a CAD program can produce can equal a Stradivarius. Same holds true for 1940?s Martin guitars. Both of these were built by hand, and fine tuned by ear. The bracing, the woods used, the type of glue, everything was taken into consideration. The basic template was there for both, but the finished product was all done by ear. The same is still true for custom built acoustic instruments.

I recently had a 1924 Martin guitar complete rebuilt. The Luthier that did the work did some ?fine tuning? after it was assembled, matching the bass and treble sides, and the 90 year old guitar sounded fantastic.

What does all this have to do with crossovers? I?m so glad you asked! Every component in the crossover is +/- 5%, even the drivers. You cannot change the drivers actual values, and you cannot change the capacitors. Even if you replace them, you are still dealing with tolerances. The only thing you have left to tune is the inductor. You can manually change that value, and in doing so, you may find a ?sweet spot? where all the tolerances of that speaker come together ?just right?.

What the designers intended on paper never makes it to production. The only way that would happen is if you tighten up the tolerances on all the components, which drives the cost exponentially higher. SO although some would argue that hand tuning an inductor is not scientific, and that you are changing what the designer(s) intended, I would argue the opposite: Although you are not doing the math, and for that matter may not even understand the math, it is in fact scientific. The reality is that the product we get at the store is not what the designer imagined ? the designer based his math on a specific set of values, which your speaker does not have. The sound that is produced is the sum of all the components in the chain, and their tolerance affects that sound. In my 12B?s, I have 5 to 7 components in each driver chain, all with +/- 5% tolerances. That equals a total of a 25% total potential variance. The only component you really have to work with that you can change is the inductor. You may be .01 or even .1 (or more) off of what the ?spec? is, but if you ear tells you it works, that is the final authority.

So for what it is worth, that is my two cents.

This is all good stuff, but Polk is the name on these speakers and Matthew POLK is the ONLY one (unless he delegates it) that gets to tune by ear.

What **** on the face of this earth would try to modify a Stradivarius by his/her own ear ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?

audiocr381ve

OldmanSRS wrote: »

Well said but how long do you burn-in a Martin guitar?

Shame on me.

Takes years to "burn in" a guitar. No, seriously. The more you play it, the more the frets wear, the more grime builds on the neck, the easier it becomes to play, etc. It starts to play and sound different.

Michael, well said.

audiocr381ve

inspiredsports wrote: »

This is all good stuff, but Polk is the name on these speakers and Matthew POLK is the ONLY one (unless he delegates it) that gets to tune by ear.

What **** on earth would try to retune a Stradivarius by his/her own ear ???????????????????????????????????????????

Should I not change out strings on my guitar because the designer built the instrument with a gauge he preferred? I bought it, I can do what I want with it right? If I wanted to paint my Polks green, I could right? What if I like it better that way? Just because my truck performs better with city tires doesn't mean I'm not gonna put mud-tires on it for off-road use.

Different strokes....