Crossover Design Changes Based on Horn Dispersion

[grumpy]

Thanks Todd and Linda for having both Glen and me over.
Very nice place and a very entertaining system.

Context for FR plots to follow:

"L200" is L200 cab with 2235, 175/HL91, 075 and custom crossover.

WT10GTi is in 1.4ft3 CV cab with tweeter left out (leaving a 3/4" long,
2" dia port)... stock port blocked off, woofer coils wired in series.

(Todd, please let me know if my descriptions are off, and I'll correct)

Measuring equipment (conveniently portable):
Intel-Mac/FuzzMeasure v2.0.11 (swept sine technique)
MOTU Firewire audio I/F
Earthworks M30 (actually S30 from when smaart sold equipment)
JBL 6215 amp
Short boom stand

[grumpy]

1) 2235 in L200 cab, playing solo (1m)
2) All drivers, HF L-pad adjustment range (1m)
3) All drivers, MF L-pad adjustment range (1m)
4) Measurements at couch (~3.3m)

I believe the red plot lines were where the L-pads were
adjusted for nominal listening (plots 3 and 4)

Measurement height was approx 075 location.

[grumpy]

1) Orange - WT10GTi in CV cab, no crossover (1m)
Green - WT10GTi in CV cab, with crossover (1m)

(crossover = "keeper" implementation)

2) Blue - WT10GTi in CV cab, no crossover (5mm, between dustcap and cone)

3) CV cab with WT10GTi as bass portion of L200 system (2235 not connected)
three snapshots of minor L-pad adjustments.

[grumpy]

Commentary: Although it appeared that some crossover changes might be
helpful to flatten the system response in areas that are a bit rough, the
follow on listen and A/V demo were very entertaining. Adjustments made
after the initial plots were viewed did result in improved sound quality and
were not far off from the settings Todd had determined by ear.

Fun times folks

-grumpy

[toddalin]

Thanks Todd and Linda for having both Glen and me over.
Very nice place and a very entertaining system.

Context for FR plots to follow:

"L200" is L200 cab with 2235, 175/HL91, 075 and custom crossover.

WT10GTi is in 1.4ft3 CV cab with tweeter left out (leaving a 3/4" long,
2" dia port)... stock port blocked off, woofer coils wired in series.

(Todd, please let me know if my descriptions are off, and I'll correct)

Measuring equipment (conveniently portable):
Intel-Mac/FuzzMeasure v2.0.11 (swept sine technique)
MOTU Firewire audio I/F
Earthworks M30 (actually S30 from when smaart sold equipment)
JBL 6215 amp
Short boom stand

Thanks for coming by. Was a ball! We'll all have to do it again sometime. Maybe when you have time to sit through a move and listen to some SACD.

Glen, it was great! Still don't know how I let you talk me "down" on the 421A. Come on by sometime and lunch/dinner is on me.

Only thing I might add is that the L200 cabinet with the 2235 had one of the ports plugged.

Might also add that no portion of the home theater processor system was used in the testing. Grumpy brought by a dedicated JBL power amp that was connected directly from the computer sound card to the speaker under test so no "inadvertant" eq was added in the tests.

[toddalin]

1) 2235 in L200 cab, playing solo (1m)
2) All drivers, HF L-pad adjustment range (1m)
3) All drivers, MF L-pad adjustment range (1m)
4) Measurements at couch (~3.3m)

I believe the red plot lines were where the L-pads were
adjusted for nominal listening (plots 3 and 4)

Measurement height was approx 075 location.

The dip that centers at 650 Hz is my biggest peeve with the sound of the 2235s. To me, the dip reduces intellegability of the male voice and drives me nuts.
I initially though it was from the crossovers, and was even prepared to take some windings off the inductors. But, they certainly seem to work with the W10GTIs, so... maybe woofer/crossover interactions with 2235s?

[grumpy]

FWIW, I've attached two more plots.

One is a partial, which shows fair agreement with the JBL Tech Sheet plot
showing the 2235H in a 10ft3 box. In this frequency range, it would seem
to validate the measurement system.

http://audioheritage.org/vbulletin/s...ad.php?t=10651

This first plot shows both a 2234H (newly reconed/red) and a
2235H (aged,old-refoam/blue) in the same cabinet (4430)... 1dB/minor
division. 1/24oct smoothing.

Second plot shows same 2235H in 4430 cab trace (blue) vs the 2235 in the 1-port
L200 cabinet (red), approximately the same measurement distance (I've shifted
levels for visualization). I'm a bit surprised at the differences above 300Hz.
Without further testing, I don't have a good explanation. -grumpy

[toddalin]

FWIW, I've attached two more plots.

One is a partial, which shows fair agreement with the JBL Tech Sheet plot
showing the 2235H in a 10ft3 box. In this frequency range, it would seem
to validate the measurement system.

http://audioheritage.org/vbulletin/s...ad.php?t=10651

This first plot shows both a 2234H (newly reconed/red) and a
2235H (aged,old-refoam/blue) in the same cabinet (4430)... 1dB/minor
division. 1/24oct smoothing.

Second plot shows same 2235H in 4430 cab trace (blue) vs the 2235 in the 1-port
L200 cabinet (red), approximately the same measurement distance (I've shifted
levels for visualization). I'm a bit surprised at the differences above 300Hz.
Without further testing, I don't have a good explanation. -grumpy

FWIW, the "2235s" in my L200 cabinets were alnico 2205s recharged and reconed as 2235s by OCS in Dec 2005. The 2235 is a valid replacement cone for the 2205 basket.

[Robh3606]

FWIW, the "2235s" in my L200 cabinets were alnico 2205s recharged and reconed as 2235s by OCS in Dec 2005. The 2235 is a valid replacement cone for the 2205 basket.

If I read Grumpys post correctly that could be the answer. Maybe they didn't recharge them properly. If the magnets are partially demagged you would see a roll off up top. They used JBL kits??

Rob

[grumpy]

FWIW, the "2235s" in my L200 cabinets were alnico 2205s...

We can re-measure and I can bring a fresh 2235H to compare in/ same box, same env.

If I read Grumpys post correctly...

I think you did . 2nd plot: red=2205/2235 in L200 cab, blue=2235H in 4430 cab

[Earl K]

Nice Work Grumpy !

Very Intriguing ( there's quite a mystery happening here ) ;

If I read Grumpys post correctly snip,,,,,,,,snip

- I agree that some of the posts are a tad ambiguous and invite assumptions .


Grumpy, some housekeeping notes ;


(i) It seems that the above picture shows 2 different woofers ( a stock 2235H as the blue trace & a hybrid 2205a/2235 in red ) , measured in 2 different cabinets ( stock 4430 & stock L200 with one port blocked ) and / also measured in different acoustic environments ( your place & Todds' place ) .
- Are those observations all correct ?

- For the sake of clarity ( now & for future reference back to this interesting file ) / this sort of info ought to be stressed or included within the pic-files' info header ( or better yet, IMO , inserted into the pic as an overlay via some image editor ). Anyways ,,,

(ii) I'm really surprised ( shocked somewhat ) at the smoothness of the blue curve . Perhaps this is partially due to the offset location of the woofer on the 4430s' baffle board . That will reduce ( somewhat ) destructive diffraction effects .

- It would be quite illuminating to see if the jagged "Hills & Dales" ( on Todds 2205/2235 hybrid ) smooth out some with his woofs placed ( & remeasured ) in your 4430 cabinets ( & measured in your acoustic environment ). It would be nice to know the relative contribution of your acoustic environment .

- Todds' "refurbished" 2205/2235 woofs should have a full set of TS parameters run on them, to see what's up with them. ( Woofer Tester 3 is now out & is only $100. at P.E. , TODD ??? ) .

- As RobH has suggested, that OCS "remag" on Todds' hybrid, looks very suspect ( a partially demagged alnico would explain quite a lot here ) .
- Checking the TS parameters ( including the BL figure, with Woofer Tester 2 or 3 ) would be a decent QC "reality-check" of OSCs' handiwork .



- The midrange peaks centered at around 680 hz ( in stock 2234s and 2235s, seen immediately above ) , are also pretty typical of the 2225h-style, ribbed cone (FWIW ) .
- It's pretty bizarre, that Todds woofs ( seen below ) show almost the complete opposite characteristic in this critical FR area .



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[grumpy]

Thanks Earl,

- Are those observations all correct ?

Yes... and I could make the explanation both longer and more obvious.
Points taken on annotating plots better I got lazy.

I'm really surprised ( shocked somewhat ) at the smoothness of the blue curve

Well, this was after a bit of measuring and moving in my living room.
It's certainly possible to make things worse.

It would be nice to know the relative contribution of your acoustic environment .

Indeed. Also do have WT2, but we didn't have time to get that far into it.... next time
Anyone want a discount deal on a "MINTY" WT2 ? (works great, new one's faster)

[grumpy]

Nothing really new, but a refresh, given the recent in-situ measurements... and
Todd was interested

So here I've plotted another model of Todd's latest "keeper" crossover.
I used loads closer to actual/current setup with WT10GTi,
and spec'd (not measured) inductor DCRs.

Zilch posted schematic:
http://audioheritage.org/vbulletin/s...6&postcount=62

HF for this "cascaded" version (per schematic) is shown in orange.
Todd wired his HF section in parallel, and is shown in green.
L-pads are set to maximum.

I have not repeated the plots using 8/16/8ohm loads for LF/MF/HF... see referenced
thread/post if interested:
http://audioheritage.org/vbulletin/s...3&postcount=94

Note. Todd's 2205/2235 is getting hi-passed even lower than plot below.
Adding that info to the 2205/2235 FR plot shown earlier in this thread gives a good
hint about why there's a hole in Todd's L200/2235 response.

[Earl K]

Folks, sorry for the blog-like turn of this thread. My intent in adding to it was to share
a history of a "get together" and to provide some measurements for Todd to use as he
sees fit. It certainly is not intended as a how-to for crossover/system design. ...

Well,, I'm not the blog police but ,,,

- I see no need for an apology.


AFAIK ( or remember ) ,,, a working defination of "blogging" ( as it applies to participating here at this forum ) has never been fully worked through .

AFAIC ,,, a thread becomes a blog once it has become nothing more than a "one-way" dictation of personal information or experience .

- IOW, as long as there remains in place ( on some temporal basis ) a 2-way exchange of ideas and information / no blog exists .

<>

ps ; Things here maybe off-topic / but that's a different concern .

[Robh3606]

I see no need for an apology.

Ditto

Rob