SDA SRS1.2 with Erse SuperQ inductor modification

OldmanSRS

Recently I changed the stock 16.8 mH air core inductor in the 1.2's in favor of a 17 mH Erse SuperQ iron core inductor resulting in increased low bass, tigher bass, as well as unmasking some of the lower midrange.

However, my initial impression was the speaker sounded a little lean or thin in the warmth department so I took a look at what was going on with the SDA XO response.

I measured -20 dB tones at the output of the XO to the dimensional array produced by the Carver amp. The measurments with the stock inductor are the actual dB levels. The measurements for the Erse 17 and the modified Erse 17 are dB gains or losses referrenced to the stock inductor.

Note that above 80 Hz the XO really starts to roll off and attenuate the SDA. At 100 Hz the output to the array is down 6dB or 1/4 the power at 20 Hz.

With the 17 mH Erse, note the signal increase below 100Hz due to the much lower DCR. There is 3-4 dB of gain or more than twice the power below 100 Hz. Also note the reduced power above 100 Hz with 2-4 dB loss, or 1/2 the power between 100 and 800 Hz. I think this is the reason the speakers sound thin on some recordings.

I decided to remove coils of wire from the Erse and ended up taking off 16 turns (6'10") of wire until I reached a point where the frequency response above 100 Hz was in between the stock inductor and the Erse 17 mH. Note the lower bass increased just slightly (lower DCR) and above 100 Hz the response was only down 1 dB from the stock inductor.

Listening proved the modification was perfect. It added just a hint of upper bass to flesh-out the sound and maintained the super tight low bass and punch from the lower DCR erse coil.



Note I also measured the stereo array response in the far right column. It's running much more "full range" than the dimensional array. In the lower bass it has about the same output but as frequency climes it continues to produce a healthy signal.

Joe08867

Measurements are fine and dandy but how do they sound to you. How long ago listening wise did you change the inductor? They need time to burn in like all other electronic components.

dorokusai

Inductors take a long time to settle.

Joe08867

Exactly my point, if they haven't been in the speaker for at least 150-200hrs they probably still need to settle down.

I wouldn't advise tweaking any of them until then.

Although Oldman, unwinding inductors is a practice I have used to get just the right mH.

OldmanSRS

Joe08867 wrote: »

Measurements are fine and dandy but how do they sound to you. How long ago listening wise did you change the inductor? They need time to burn in like all other electronic components.

I did the initial listening write up here:
http://www.polkaudio.com/forums/showthread.php?t=122576

They have been in for a few weeks and maybe 20 hours. I thought they sounded too large (they have more inductance than the stock 16.8 mH air core's) and the sound was somewhat thin in the upper base. I thought the stock ones were somewhat bloated in the upper bass.

The measurements help me understand how the XO is working and correlate that to what I'm hearing. I like what I'm hearing now. It's someplace between boated and thin, i.e., just about right. It would be interesting to measure them and see what inductance they ended up at. The change from air core to lamineted iron core may impart some sonic difference as well (hysterysis, permeability, saturation etc.)

I'm not a member of the need to burn in the inductors group and don't want to kick that sleeping dog.

dorokusai

Oldman - Rock on and you're the only one who knows how it sounds. I've done a couple dozen xover mods and have had inductors swing everywhere in regards to sonics , so it's just an observation. I don't believe that caps need so much bleed time either but inductors have always thrown a wrench in my work. I'm no DarqueKnight but just audibly they are all different in drastic ways and tend to roller coaster for months until getting tuned up. Do what you want, just commenting. Your initial obervations make sense but I would bet that they change character again.

Mark

OldmanSRS

I save the wire so if need be I can add some back on.

DarqueKnight

OldmanSRS wrote: »

I'm not a member of the need to burn in the inductors group and don't want to kick that sleeping dog.

You might want to contact Erse to see if they have any guidance requiring burn in for their inductors.

FTGV

OldmanSRS wrote: »

However, my initial impression was the speaker sounded a little lean or thin in the warmth department ....

That would be the expected result of removing several ohms of resistance in series with the driver.That extra resistance modifies(increases) the Qts parameter of the DA sections woofers and reduces the control (damping factor) the amplifier will have over it.Raising driver Q by the addition of large amounts DCR can result in reduced definition and this underdamping can result in some response peaking at the bottom end of the woofers range.The latter may account for what some would describe as added warmth.By removing the excess DCR your not only reducing it's attenuation effect your reducing driver Q so one would expect higher bass output(for the same level input) but with better control and definition.

OldmanSRS

In pursuit of lost warmth after the Erse 17's went in and prior to removing windings, I added 2.5 Ohms of DCR in series with them to see what effect that would have, essentially bringing them back to the same DCR and supposedly the inductance of the stock coil. I didn't notice any gain in warmth but noted some loss off deep bass obviously due to the reduced power especially below 100 Hz at the SD array.

I emailed Erse regarding their recommendations for burn in on the inductors.

Face

Fred, what would you recommend for inductor burn in?

FTGV

Face wrote: »

Fred, what would you recommend for inductor burn in?

Soldering iron..I find they work better when soldered in circuit.

TECHNOKID

FTGV wrote: »

Soldering iron..I find they work better when soldered in circuit.

Any wood stove in the igloo, that should do the trick? Just heat-up the iron over the flame then, burn in! (BTW; you cheated and edited at the same time I quoted you! )

FTGV

TECHNOKID wrote: »

(BTW; you cheated and edited at the same time I quoted you! )

Yeah my original 10,000hr figure might be viewed as extreme.

btw.Is Mike in the inductor burn in camp ?

OldmanSRS

FTGV wrote: »

Yeah my original 10,000hr figure might be viewed as extreme.

btw.Is Mike in the inductor burn in camp ?

I'm in the burn-out group more so than the burn-in group :biggrin:



Still waiting on Erse to reply to the email regarding burn-in on the SuperQ.

OldmanSRS

Q: Does the Erse SuperQ require a burn-in period to stabilize, reach its rated inductance, or otherwise change for the better to maximize its sound quality?

A: Thank you for your interest in ERSE Audio. There is not a required burn-in period for any inductors, they are at the correct inductance as soon as they leave our facility. Please contact us with any further questions.

Thank you,
ERSE Audio Sales Team
_________________________________
ERSE Audio
www.erseaudio.com

May sleeping dogs rest once again :rolleyes:

Face

FTGV wrote: »

btw.Is Mike in the inductor burn in camp ?

I haven't heard a notable difference from inductor "break in". But for capacitors and some resistors(Duelund), yes.

drumminman

OldmanSRS wrote: »

I'm in the burn-out group more so than the burn-in group :biggrin:



Still waiting on Erse to reply to the email regarding burn-in on the SuperQ.

Is that an original Shelby Cobra? 427?

My father used to know Carroll Shelby and raced the AC Bristol, which was the forerunner. They look very much alike.

In fact, Shelby bought the bodies for the 289's from AC I believe.

Joe08867

Never noticed a whole lot of burn in of Air-core but definitely Iron core.

That Shelby looks SWEEEEEEET!!!!

OldmanSRS

drumminman wrote: »

Is that an original Shelby Cobra? 427?

My father used to know Carroll Shelby and raced the AC Bristol, which was the forerunner. They look very much alike.

In fact, Shelby bought the bodies for the 289's from AC I believe.

It's a replica that I built at home over 3 years time starting with the Factory Five base kit consiting of: A period correct 4" round-tube powder coated space frame chassis, 50 aluminum panels that get riveted to the frame and a fiberglass body that replaced the orginal's alumium body, windshield, seats, selected suspension parts, misc harware...

The bodywork, paint, engine, tranny, electrical system, cooling system, fuel system, brakes, tires/wheels, instruments, rear end, steering rack, driveshaft, are up to the buyer to acquire and install.


3 pics from a few weeks ago:

inspiredsports

You can't just leave us hanging like that . . . what engine/tranny combo did you drop in ?? :biggrin:

OldmanSRS

It's a 340hp/330ftlbs Ford Racing 302 crate engine coupled to a world class T5Z 5-speed. It has power steering, power 4-wheel disc/ABS brakes, AC/heat. 0-60 in under 4 seconds with is actually better than the original car with the 427. The quickness comes from less weight, wider tires, better rear end geometry, and better gearing. MPG is at least double that of the original 427 engine.

It's REAL car. It will go coast-coast just like a daily driver, all day, every day. No apologies and take no prisoners. :biggrin:

Buildsite: http://www.worldisround.com/articles/123897/index.html

michaeljhsda2

Great looking car!

drumminman

That's great - simply stunning!

TennMan

I just stumbled across this thread. I have been thinking about adding the SuperQ inductors to my 2Bs. Great information about the SuperQs and great photos of an amazing car!

F1nut

Really NICE car!

Hermitism

Wow, beautiful car. Excellent step by step photos on your webpage. Spent a good amount of time looking. Amazing really!

fjross

Very nice Cobra. I picked up my Factory Five kit in 1999 and finished it in 2000. I did all the work except the body and motor.

MAD

Sound and cars... that's what it's all about.

Looks beautiful, you did an excellent job.

I'm sort of waiting for my 92 prelude to break, even though it just doesn't and keeps going.
It gives me more time to find the right classic daily driver.

TennMan

I've always loved cars. I have a Buick Reatta 2 seater. You don't see too many of them around. Not in the same class as the Cobra but still a unique car.

South Dakota Po

I also have Reatta and Polks. Only the top 60 Buick dealers in the country got one of these.