HOLMImpulse Measurements, Need step by step dummy guide.

[augerpro]

There was a minor point about a shunt resistor in this thread
http://www.diyaudio.com/forums/multi...-vs-16ohm.html

Well that was 20 minutes of my life I'll never get back

[penngray]

Well that was 20 minutes of my life I'll never get back

lmao

Does my Lpad circuit with is 4.7Ohm in parallel play a role in changing the impedance? I never measured if it did.

[Saurav]

Oh, forgot you had an L-pad. Yep, that will definitely be changing the impedance, and flattening it out too (because of the parallel component).

If you measure with the L-pad, you'll have a quick visual of the effect. The parallel leg of the L-pad will flatten the driver's impedance peaks, then the series leg will just add on to everything.

[coctostan]

From what I've gathered, a shunt resistor should have no positive effect in an active system with a decent SS amp. It is primarily useful for passive networks and some tube amps. Whether it has an audible negative effect is debatable.

It shouldn't be difficult to try back to back to see if an effect is heard.

Also, why are you using an L-pad on an active system? You should have enough control with the DCX, right?

Concerning the polars, for which xover settings and drivers were those measurements taken?

[penngray]

From what I've gathered, a shunt resistor should have no positive effect in an active system with a decent SS amp. It is primarily useful for passive networks and some tube amps. Whether it has an audible negative effect is debatable.

It shouldn't be difficult to try back to back to see if an effect is heard.

Also, why are you using an L-pad on an active system? You should have enough control with the DCX, right?

Im using the Lpad to lower hiss of the CD. The DCX can not do this since the CD has a hiss (57dB at the 1") even with the amps and no DCX. The LPAD drops it 10dB, its more of a "That hiss annoys me" thing. It was the same with my Ribbon designs. I know that when I play any music the hiss isnt there but you hear in between songs.

Concerning the polars, for which xover settings and drivers were those measurements taken?

The polars are using the 1200Hz xover settings with the Celestion 1425 CD and TD12M woofer.

This one:

https://www.htguide.com/forum/showpost.php?p=496500&postcount=78

[Saurav]

1200 or 1500? I don't remember doing a 1200 with the 1425.

Edit: OK, saw your edit, I think that was the 1500.

[coctostan]

That makes sense about the hiss.

Any chance to take measurements with the BMS?

[penngray]

That makes sense about the hiss.

Any chance to take measurements with the BMS?

Yes, I wan to try and get them done by tomorrow night.

The BMS is the one Im more excited about since the SQ should be higher.

Im also going to try and get the 1745 (big brother to th 1425) worked into this project. Its low cost too and it performs better below 2KHz then the 1425.

On AVSForums we did a simple 2.2 uF cap in series and man does it flatten out the CD, with one hump left around 4.7K Hz. Im thinking about changing some XO stuff to match what Zilch has been offering over there.

The Lpad, flatttens the Impedance and phase pretty good too so things are definitely interesting/confusing for me now.

More to come....This project is far from over for me.

[penngray]

I have decided to create an actual build thread ( I will copy over all important crossover info). The point of this thread was to learn how to use HOLM properly, It was a great success along with actually learning ARTA.

Thanks guys, I have learned more in a month then I have in 3 years of speaker building.

[penngray]

My speaker XO build will continue here

https://www.htguide.com/forum/showthread.php?t=36341