Heil with a JBL woofer

[dkalsi]

You could, I didn't. You could also limit a sine sweep or just use Impulse. Just do whatever you are comfortable with.

Rob

I don't think I will use a protection cap. They can be safely played down to 800hz with a second-order crossover <- that makes them pretty robust in my book. Plus given their efficiency, I plan on feeding them minimal power for messurement purposes.

I just really hope they measure the same.

[jmpsmash]

I scan them without protection cap from 200Hz upwards with a 4W amp. No problem.

[dkalsi]

Hi All,

Can someone please post raw measurements of the AMT drivers? Both Left and Right - just the AMTs.

I just measured my pair and there is about 3-4 db in overall variance, with one measuring an almost flat 4.2 impedance, and another one measuring 3.3 impedance.

[toddalin]

Both of mine have a dc resistance of 2.9 ohms, which is why I run a 5 ohm resistor in series and use an 8 ohm L-pad.

[Ian Mackenzie]

Hi All,

Can someone please post raw measurements of the AMT drivers? Both Left and Right - just the AMTs.

I just measured my pair and there is about 3-4 db in overall variance, with one measuring an almost flat 4.2 impedance, and another one measuring 3.3 impedance.

I made a comment in other diy thread about QC. I am told from a very reliable source when the Heil was introduced by ESS that they were difficult to manufacture with close consistency.

So if yours actually measure different that’s how it is.

It would not be difficult to adjust the output in the crossover so that they match. The FR possibility won’t match.

[dkalsi]

I made a comment in other diy thread about QC. I am told from a very reliable source when the Heil was introduced by ESS that they were difficult to manufacture with close consistency.

So if yours actually measure different that’s how it is.

It would not be difficult to adjust the output in the crossover so that they match. The FR possibility won’t match.

You are right. I'm in the process of building a bass cabinet to go along with these. I'll see how difficult it would be to get them to match (moreorless) via the crossover.

[Ian Mackenzie]

Btw those schematics are only accurate for the original woofers involved. You don’t know the frequency response character so the woofer schematic is only ball Park. As I recall ESS only went for 8, 10 and 12 inch ? drivers.

So what really works is a matter of experimentation per usual.

As they say nothing is plug and play and in real audio everything matters.

[badman]

I made a comment in other diy thread about QC. I am told from a very reliable source when the Heil was introduced by ESS that they were difficult to manufacture with close consistency.

So if yours actually measure different that’s how it is.

It would not be difficult to adjust the output in the crossover so that they match. The FR possibility won’t match.

I visited the current ESS factory some years back. The diaphragms are difficult to make and are actually folded manually, but the current generation of diaphragms seems to have pretty good QC. Older diaphragms are challenging- there have been a number of variants over the years, including polyethylene and mylar variants. Currently it's mylar, but the polyethylene would likely have higher internal membrane damping (not sure it matters for an AMT). My PE phragms are badly deformed, PE is soft and heat sensitive.

Basically, you have to measure and validate.

[jmpsmash]

I have a pair of current production Heil. Let me make some comparative measurement this weekend.

[SEAWOLF97]

Older diaphragms are challenging- there have been a number of variants over the years, including polyethylene and mylar variants. Currently it's mylar, but the polyethylene would likely have higher internal membrane damping (not sure it matters for an AMT). My PE phragms are badly deformed, PE is soft and heat sensitive. .

good info ... is there a way to tell what your AMT is ? Mine seem very smooth sounding and as I presume they are supposed to be.

[toddalin]

Mine came from the AMT 1D line. They actually look a bit different than the earlier/later versions.

[dkalsi]

I have a pair of current production Heil. Let me make some comparative measurement this weekend.

Thank You! - I look forward do it.

[dkalsi]

Took few measurements this evening:

(1) Sample 1 vs Sample 2 - Frequency Response
(2) Sample 1 - Distortion (2.83v at terminal - mic 20in from driver)
(2) Sample 2 - Distortion (2.83v at terminal - mic 20in from driver)

Distortion seems awfully high and maybe that's why I haven't been super impressed (just yet).

Its almost as if some assembly is resonating inside (not just the diaphragm - but the whole diaphragm assembly inside is resonating).

[toddalin]

Took few measurements this evening:

(1) Sample 1 vs Sample 2 - Frequency Response
(2) Sample 1 - Distortion (2.83v at terminal - mic 20in from driver)
(2) Sample 2 - Distortion (2.83v at terminal - mic 20in from driver)

Distortion seems awfully high and maybe that's why I haven't been super impressed (just yet).

Its almost as if some assembly is resonating inside (not just the diaphragm - but the whole diaphragm assembly inside is resonating).

Your plots confirm what I see on my RTA. I don't know why these people keep showing plots with a decrease in volume after the 5KHz hump. My plots, even without the crossover, show a continuing rise above this point which is why I devised the wedgie. I don't know why you don't show the drop after ~14K, (my soft room?) but if you are using the Heils as pictured above by Seawolf, they are not the "Great Heils" as I use.





With the wedgie:

[Earl K]

Hi "D"

This pic is ( IMHO ) un-necessarily cluttered with distortion products that are usually ignored.



I'd suggest displaying only the 2nd, 3rd & 5th harmonics as seen in the following pic ( clipped from the previously mentioned german pdf article highlighting these AMT's ).



I also believe your measured distortion numbers would be a lot more comparable ( to what's seen immediately above ) if you measured at 90db ( at 1 meter distance ) like the magazine did.

( Just saying > measuring at 1/2 a meter at 2.83 volts will naturally jack-up the distortion readings ! )