Another 511B/902? alternate driver?

[iain42]

Let me first say that I love the sound and performance of this combo. Here is a measurement from my room with no xover. It isn't a perfect measure but it gets me in the ballpark.
http://lh3.ggpht.com/_NVQujPOPx2c/Sh8XHWnesEI/AAAAAAAAHEo/WdKDwT2unps/s800/511b9028.jpg
Is there a driver I can buy other than TAD that will go out a little flatter to 600 with about the same performance out to 20khz. A drop around 17khz is ok. I don't want to put that much eq boost at the 600hz-1khz.

thanks :)

[Earl K]

Is there a driver I can buy other than TAD that will go out a little flatter to 600 with about the same performance out to 20khz. A drop around 17khz is ok. I don't want to put that much eq boost at the 600hz-1khz.

- The JBL 2426H has better performance below 1000hz than Altecs' 902 . This might be attributable to the 2426s' lower Fs ( free air resonance / the JBL is about one octave lower if I recall correctly ) .


Let me first say that I love the sound and performance of this combo. Here is a measurement from my room with no xover. It isn't a perfect measure but it gets me in the ballpark.

-The sonics of the titanium diaphragmed 2426H may disappoint you if your "gaga" over the 902 ( & the sound of it's aluminum diaphragm ).

- I suspect your better off working with what you have ( & love ) & finding someone to design a 2-pole "bump-filter" for you to use as the Hipass within your crossover . A "bump-filter" may buttress up the FR weakness below 1K .

- If I had a 511 horn I'd give it a go on your behalf / unfortunately I don't / I don't even have an 811 . :( ( Too bad Zilch is ignoring Altec these days .)

- What are you presently using for a crossover with this horn/driver combo ?

cheers >< :)

[Earl K]

On a separate matter ;

- Would you please reshoot your horn/driver combo (using the following settings when setting up TrueRTA ).

(a) Vertical Scale : 40 db instead of the 110 db currently displayed .
- Manipulate the "db Top" & "db Bottom" controls to achieve this .

(b) Range : make "Lo Freq Limit" 200 hz & the "Hi Freq Limit" 20 kHz

(c) RTA Resolution : 1/24th Octave

(d) Test Signal Type : Please use the "Quick Sweep" .

(e) I'd suggest 18" to 24" on axis as your test distance ( this distance should reduce most reflective errors ).

- This will give a much more critical look at this combo .
- The reason I ask is; I don't think there's any documented response graph of the GPA 902 driver on a 511b ( anywhere public ) .

Thanks >< Earl K

[iain42]

On a separate matter ;

- Would you please reshoot your horn/driver combo (using the following settings when setting up TrueRTA ).

(a) Vertical Scale : 40 db instead of the 110 db currently displayed .
- Manipulate the "db Top" & "db Bottom" controls to achieve this .

(b) Range : make "Lo Freq Limit" 200 hz & the "Hi Freq Limit" 20 kHz

(c) RTA Resolution : 1/24th Octave

(d) Test Signal Type : Please use the "Quick Sweep" .

(e) I'd suggest 18" to 24" on axis as your test distance ( this distance should reduce most reflective errors ).

- This will give a much more critical look at this combo .
- The reason I ask is; I don't think there's any documented response graph of the GPA 902 driver on a 511b ( anywhere public ) .

Thanks >< Earl K

Let me say I am no expert at measuring but it is to get me in the ballpark and I don't take it as gospel but rather something to work with in my room. I will be more than happy to measure again. I'll try to do it with your recommended settings this weekend.

Thanks again.

[Earl K]

Hi,


Let me say I am no expert at measuring but it is to get me in the ballpark and I don't take it as gospel but rather something to work with in my room. I will be more than happy to measure again. I'll try to do it with your recommended settings this weekend.

Thanks for any & all efforts that you make in measuring your horn/driver combo .

( It's the GPA 902-8A that you have in your possession , right ? )

- On a different matter ; there's a new acoustic test program ( which is "free" for now ) that's worth downloading & test-driving .
- You may want to check it out ( though, it is some-what more complicated than TrueRTA ) .

- DownLoad details are available within this thread (http://www.diyaudio.com/forums/showthread.php?s=&threadid=144984) ( over at diyAudio ) .

- Here's the response curve for one of my Altec 288s ( measured on a Emilar EH-500-2 radial horn with foam lip extensions ) .
- This petite radial horn is a fraction smaller than the H811-b .
- This is raw data ( unsmoothed ) .
- ( I can't remember if it was made with a sinewave sweep or a full-frequency chirp .)
- For those with keen eyes / one should be able to make out the effects of a mild 2-pole "bump-filter" acting as the HiPass .

http://www.audioheritage.org/photopost/data//500/Altec_288K_EmilarEH-500-2_test_1_PNG_.png


>< cheers :)

ps : & btw; these aren't the default colors for the FR display / but obviously, they are selectable .

http://www.audioheritage.org/photopost/data//500/PNG_test_3.png

[Earl K]

"Emilar EH-500-2 radial horn with foam lip extensions"...
is this pointed to elsewhere? Nice pointer to HOLMImpulse S/W, btw.

- Does this question mean that you can't see either of the 2 .png files on your browser ? ( called "Emilar EH-500-2 radial horn with foam lip extensions"...)

>< cheers :)

[Earl K]

- Oh okay, glad you can see the pics .


FR plots in post #5? I can see them... was trying to find out if there was some
documentation or pictures of your foam-lip implementation on the EH-500's.
A search here came up MT...


- Right now there's no ( organized ) documentation that I wish to story-tell over . This is a work in progress / it's basically to see if I can get the Emilar Radials up to scratch ( or close enough ) to replace my H5038 ( paragon horns ) / on a temporary basis .

- "Up To Scratch" equates to their imaging capabilities / ( FR is easy enough to manipulate passively ) / massaging the imaging "thing" is a whole different matter .

>< cheers :)

[iain42]

Ok I have been researching the 902's and measurements other people have made. I have GPA 902-8 that are only a few years old. I have seen many different measurements of the 902 on 511bs and I am very confused. It looks like there are two different drivers on the loose. The difference is some perform very well to 500hz and some like mine drop fast after 900hz. I want the 902's that perform best down to 500. I haven't had a chance to measure again but it is clear to me that not all 902s are created equal. What should I start looking for?

[analog addict]

Maybe try a set of Altec 902-8B's (http://www.altecpro.com/pdfs/vintage/SpeakerAndMics/drivers/902-8B%20HF%20Driver.pdf). The other option would be to cover the lower midrange you're interested in from the other end, say with an Altec 515 or 416 of some type...;)

[speakerdave]

. . . . Is there a driver I can buy other than TAD . . . .

Unfortunately, I think you are excluding the ONE driver that can cover the range you want, and it can do it on the low end because of its massive body, which the Altec and JBL 1" drivers lack. It's not just diaphragm resonance that limits the low end, the resonance of the body matters too, and it's the body mass of the large format compression drivers that helps them go low, not just the lower resonance of the "moving" parts. I think the Tad TD 2001 may be the solution you are looking for. Why exclude it?

[iain42]

Analog Addict,
Thanks I'll try to find a 902-b.


SpeakerDave,
Maybe your right and I should just save money for the TAD drivers. I've heard the TAD 4001's a few times and they are nice. Sure does give the wallet a beating.


I'll start researching the 2001 and 4001. Perhaps I can pick them off ebay.

Thanks

[speakerdave]

New ones would be my recommendation (shop for a price--they're out there)--or extreme care buying used. As with all used compression drivers diaphragms may need replacement, and with Be buying them will almost surely wipe out the savings of buying used drivers, unless you know you are buying cores.

[iain42]

New ones would be my recommendation (shop for a price--they're out there)--or extreme care buying used. As with all used compression drivers diaphragms may need replacement, and with Be buying them will almost surely wipe out the savings of buying used drivers, unless you know you are buying cores.

You are correct. I've seen good looking cores sell for $100 -$200 but those be diaphragms are $475-$600 each. At that price I could get a pair intact for $1300.

Does anyone have a fr curve of the 2001?

[JeffW]

- Here's the response curve for one of my Altec 288s ( measured on a Emilar EH-500-2 radial horn with foam lip extensions ) .

Earl, can you post a pic of the EH-500-2 with the foam lips? I've seen the EH-500, but not the foam lip extensions.

TIA

[Earl K]

Earl, can you post a pic of the EH-500-2 with the foam lips? I've seen the EH-500, but not the foam lip extensions.

Okay, I'll take a picture tomorrow and post it then .

To make this info relevant to the thread I'll include a new FR graph of the JBL 2426/7 on the Emilar radial-horn .

>< cheers :)

[Mr. Widget]

You are correct. I've seen good looking cores sell for $100 -$200 but those be diaphragms are $475-$600 each. At that price I could get a pair intact for $1300. Clean cores with properly installed new diaphragms are always my choice over a pair of mystery drivers with an unknown history.


Widget

[Earl K]

Earl, can you post a pic of the EH-500-2 with the foam lips? I've seen the EH-500, but not the foam lip extensions.


- Here's the FR of the JBL 2427H on the Emilar EH-500 radial horn . A single in-line cap ( 17.5 uF ) helps form the high-pass .
- There's no EQ applied ( ie; no HF contouring ).

- This was "shot" on-axis at 16" / this is swept-sine with no gating / with two flavours of smoothing applied to the same captured impulse signal .

http://www.audioheritage.org/photopost/data//500/JBL2427H_Emilar_Horn.png

- Here are some grainy pics of the added foam bell extensions ( thanks to "bfish" from the Altec Forum for the suggestion ) .
- These "lip extensions" are closed-cell pipe insulating foam that have a 1 5/8" outside diameter .
- Eventually, I intend to add a layer of open-cell foam over the closed cell foam ( to try to mitigate the remaining diffraction anomalies such as that "hole" between 700 and 850 hz ).

>< cheers :)

[JeffW]

Thanks for those pics, Earl. I've heard of other horns using foam "lips", but never actually saw any in place.

[iain42]

Is this the bit of info I have been searching. Should I look for a 902-8T?
http://lh6.ggpht.com/_NVQujPOPx2c/SlzPxkSnZzI/AAAAAAAAJCY/GhQokYjSy8I/s800/902T.jpg
I think this would explain the different curves I've seen on the electroweb. However, it seems most people remove the loading cabs but if it gives better performance from 500-1khz that is great. I'll gladly keep the light diaphragm and loading cap for better performance in this region. Am I on the right track or got it all wrong? Wouldn't be the first time.

I'm currently using a pair of GPA902-8.

[Earl K]

Is this the bit of info I have been searching (for) ? Should I look for a 902-8T?

- I suspect it's wishful thinking ( on your part ) to believe that the text you just included isn't anything more than old "AltecSpeak" .

>< cheers :)

[iain42]

- I suspect it's wishful thinking ( on your part ) to believe that the text you just included isn't anything more than old "AltecSpeak" .

>< cheers :)

Thanks LOL...... Wouldn't be the first time.

I guess I'll pick up an old 902-A just for curiosity sake.

[Earl K]

http://www.audioheritage.org/photopost/data//500/GPA_902-8_on_511b_5.png

Here's a cropped enlargement ( of your GPA 902-8 on a 511b ) seen in a more discriminating scale .

It clearly shows the weakness of your combo below 1000 hz / specifically when compared to sfoggs' ( original Altec 902-8B ) on a 511b horn ( seen below ) .

http://forums.klipsch.com/idealbb/files/902-8b.JPG



<> cheers

[Altec Best]

But to these eyes it looks like the top end is slightly better slightly.

Am I reading it right Earl ???

[Earl K]

But to these eyes it looks like the top end is slightly better.

Am I reading it right Earl ???

- Seems similar enough to be called a draw IMO .

- OTOH, the thread has always been about the performance of iain42(s)' GPA 902 / down in the 500 to 1000 hz area .

- The anedoctal evidence ( like which is posted here in this thread ) suggests that GPAs' move to the 9 slit radial phase plug has helped increase the top-end performance ( when using the stock 34647 diaphragm ).
- Unfortunately, it appears these HF gains have been accomplished at the expense of the performance of the drivers' bottom octave . This is a normal engineering tradeoff ( btw ) .

- There aren't enough ( independant ) FRs posted on the internet of either combination , so nothing here is conclusive .
- ie; it's ( the suggested differences between old & new 902s are ) all still conjecture at this point .


<> cheers

[Altec Best]

- Seems similar enough to be called a draw IMO .

- OTOH, the thread has always been about the performance of iain42(s)' GPA 902 / down in the 500 to 1000 hz area .

- The anedoctal evidence ( like which is posted here in this thread ) suggests that GPAs' move to the 9 slit radial phase plug has helped increase the top-end performance ( when using the stock 34647 diaphragm ).
- Unfortunately, it appears these HF gains have been accomplished at the expense of the performance of the drivers' bottom octave . This is a normal engineering tradeoff ( btw ) .

- There aren't enough ( independant ) FRs posted on the internet of either combination , so nothing here is conclusive .
- ie; it's ( the suggested differences between old & new 902s are ) all still conjecture at this point .


<> cheers

OK Thanks for the explanation Earl, as I have learned WRT audio there are no Free Lunches ! :(

[blvdre]

No measurements, so only more anecdotal BS. I ran a pair of the GPA902's in a 2-way, and can confirm that they do indeed suffer below 1K. Sounded very nice in the pass band though.

[Zilch]

There's also a fiber gasket between the diaphragm and front plate recess, visible at right....

[Earl K]

Thanks for that Z .

Here's your pic, reframed and then enlarged ( to my preferred vertical scale of ; 10 db to @ 1 inch )




http://www.audioheritage.org/photopost/data//500/902_M14_on511A_D34647.PNG
Hmmmm, very weak response below 2K / I wonder what's up with that ? :dont-know:

- Maybe the weakness is a "pooched" diaphragm/gap alignment / or maybe / a loading cap effect ( specifically for this model diaphragm ) ? :crying:
- Or perhaps the 34647 diaphragm never did perform very well below 1.5 K :confused: ( FWIW & coincidentally ???, this seems to have become Altecs' preferred crossover point for these small format drivers / by the time this diaphragm was released ) .
- Anyways, I really do need way more data for any final determination .

Seen below are your older 2008 measurements ( again, enlarged ) of both of Skywaves' 902-8B drivers ( measured on 811 & 511 horns ).
- His 902s are loaded with 35480 diaphragms .
- I think this was run with a simple HP cap in place , along with the Altec "T" filter ( used to contour the HF somewhat ) .
- These particular samples have much better LF performance .
- Of some note here, your 511 measurement is in pretty good agreement with sfoggs old ( circa; Oct 2003 ) measurement ( of his 902-8B on a 511 / also loaded with a 35480 diaphragm ) .

http://www.audioheritage.org/photopost/data//500/SkyW_811vs511_902_35480_PlusSize.PNG

http://forums.klipsch.com/idealbb/files/902-8b.JPG

And finally, here is GPAs newer Alnico 802-8G series II ( 9 slit radial ) on a 511 horn ( loaded with the ubiquitous 34647 diaphragm ) .
- The HF linearity has been improved , while the LF performance is maintained at an "acceptable " ( IMO ) level below 1K .

http://www.audioheritage.org/photopost/data//500/802-8G_II_511B_stretched3.PNG
http://www.audioheritage.org/photopost/data//500/802-8G_II_511B.png

<> cheers Earl

[Zilch]

My guess is loading cap don't get the low end; Model 14 was crossed high (1.5 kHz?) so they didn't likely give a whit what happens below 1 kHz.

I'm surprised the last-octave VHF is so poor in this one; I'll clean the gap and remeasure. 34647 is the "standard" diaphragm, not the "lite," correct? (It's been a while since I thought about any of this.) Skywave's 36480s were what type? Symbiotik?

Only reason I'm back at Altec is I scored a single mint M14 locally to measure and document. When that's done, it'll likely go to some "enthusiast...." ;)

[Altec Best]

[QUOTE=Zilch;297129 When that's done, it'll likely go to some "enthusiast...." ;)[/QUOTE]

Like Me !!!! :D I've been meaning to measure a Brand new 802G actually it is a 033952 before it's 802G designation.But have been busy with a new project.That have original 23744 diaphrams that are also brand new that i would like to throw into the mix.Only difference will be on a 511E w/21216A attachment and M19 XO as well.I'm really curious to see how they measure up to the current GPA 802G's

BTW- Zilch were do you have the L-pads set on the M19 X-over when you take your measurements ? Optimum or fully clockwise-counterclockwise ?

[Earl K]

I've been meaning to measure a Brand new 802G actually it is a 033952 before it's 802G designation.But have been busy with a new project.That have original 23744 diaghrams that are also brand new that i would like to throw into the mix.Only difference will be on a 511E w/21216A attachment and M19 XO as well.I'm really curious to see how they measure up to the current GPA 802G's


Yes, I'd like to see those measurements too .

How about taking a few measurements and posting them all ? ( all taken from the same location ) ;

ie;

(i) Raw ( no cap, no crossover, no HF contouring ) , at about 75 -80 db ( start your sweep at 300 hz ) .
(ii) Hipass cap only ,say 22 uf , suse the same drive level but don't worry if the HP cap steals a bit of volume .
(iii) HiPass cap ( 22uF ) now with a HF contour circuit after it ( ie; say a 6 ish uF cap paralleled with an 8 ohm resistor / both put in series with the driver ) , allow the level to be less ( ie ; don't turn up the drive level just to get back up to 75 db reference level ) .
(iv) then chuck all of the above and substitute in the N1201-8A network before the driver .

<> cheers

[Zilch]

BTW- Zilch were do you have the L-pads set on the M19 X-over when you take your measurements ? Optimum or fully clockwise-counterclockwise ?Max and min; it's playing with an LE14A LF section.

902, actually, with a ceramic magnet, it's the M14 will go to an "enthusiast...." ;)

23744 = "Lite?"

[Earl K]

My guess is loading cap don't get the low end; Model 14 was crossed high (1.5 kHz?) so they didn't likely give a whit what happens below 1 kHz.

- I'd be surprised if all the weakness below 2K is 100% attributable, to using a loading cap on a 902 body . Maybe I'm wrong ,:dont-know:, I think we need more data .:p



I'm surprised the last-octave VHF is so poor in this one; I'll clean the gap and remeasure. 34647 is the "standard" diaphragm, not the "lite," correct? (It's been a while since I thought about any of this.) Skywave's 36480s were what type? Symbiotik?

Yes, the 34647 is the standard diaphragm / while the 35480 that Skywave has is reputed to be a modernized version of the 23744 "Lite" . ( IME, it does seem to act that way ) .



http://www.audioheritage.org/photopost/data//500/Altec_802-8t_on_PH230_with-EQ_LCR.PNG
http://www.audioheritage.org/photopost/data//500/Altec_802-8t_on_SH-350_expo_EQ_FR.PNG

- Above are 2 ( passive EQed ) FRs of an 802-8T body ( same as a "G" ) loaded with a 34647 diaphragm, seen on 2 different exponential horns .
- These measurements have the loading cap in place .
- These are smallish horns / ( much smaller than Altec 511s ) / & yet I can obtain good response down to 1K .
- These alnico 802s have the Tangerine phase plug , use the 34647 diaphragm , and have the loading-cap in place .

( For reference ) here's a pic that shows the raw curve for one of the above combos ( before EQ was applied ) .

http://www.audioheritage.org/photopost/data//500/Altec_802-8t_on_PH230_with-EQ.PNG

<> cheers

[Zilch]

We appear to have the same response in the top octave.

It's doing better in the top octave on the M14 Mini-Mantaray.

[That could just be because I opened it up to take its pic, tho.... ;) ]

[Altec Best]

Yes, I'd like to see those measurements too .

How about taking a few measurements and posting them all ? ( all taken from the same location)

1 meter On-Axis or closer ? I read somewhere where you like to measure closer than that 18"-20" IIRC

[Earl K]

1 meter On-Axis or closer ? I read somewhere where you like to measure closer than that 18"-20" IIRC

Each person ( unless they are selling product ) needs to experiment somewhat to find a testing distance that they can trust gives good consistant results .

In my case, I use 1/2 meter or less because I test in my small living room .
- Here, the device under test ( DUK ) is just about always less than a meter away from something really reflective ( which contaminates the readings ) .
- I prefer not to use gating to remove these reflections since gating also imposes more smoothing ( on top of the typical 1/6 octave that a lot of people use ) / as a consequence I must move the mic closer to avoid reflections .
- You can see this extra smoothing being applied in the lower octaves ( in HolmImpulse ) by going to the impulse window & then grabbing the little pointer [that says "gate" ] and then sliding it back & forth / all the while, looking at the FR in the main window change .

Anyways, 20" to 40" , the choice is yours , just try to keep away from imposing unnecessary smoothing on the final result &/or capturing those pesky reflections .

<> cheers

[Earl K]

We appear to have the same response in the top octave.

Yes, above 2.5K , there's pretty good agreement in the raw FRs of our 2 plots ( ie; this combo can be made linear out to @ 12 to 13K ) .

Still, this thread is really about what's happening below 1K with this horn/driver/diaphragm/combo ( more for the interest of the corner-horn Klipsch crowd I suppose ) . ;0)

ie; I'm merely continuing to explore the original question ( since the OP, is AWOL ) . ;)

<> cheers

ps; Zilch, I know you are a bit more concerned with what's happening above 2k, so have a gander at this ;

http://www.audioheritage.org/photopost/data//500/802_35480Fram_2_Sammi_Horn_Raw_EQed_b.PNG

This combo gets good response out to @ 16K . That's with the loading cap in place , while using the "Modern-Lite" 35480 diaphragm in the 802D magnetic assembly ( which btw, has the older style circumferential phase plug;) ) .

[Altec Best]

Should we start a new thread ? It is a year and a half old !

Earl I'm using Holm, so what are you using for posting your plots/graphs.And as you know I'm just starting out WRT measuring and I don't have all the resistors,specific caps,etc.. Lying around so I won't be able to do that at the moment.I do have a few pairs of M19 X-over's.You guys have been doing this for some time and have all that stuff.I only purchase what I need at the moment for a X-over.

So I can't participate, unless just measuring the 802-8G with M19/1201-8A X-over will be fine.

With a starting Freq.sweep of 300Hz :dont-know: I'm just trying to help out with some usable data.Because Earl you know I'm in the middle of a big project so I can't spend too much time on it at the moment unfortunately ! I got to get my Bass bins built ASAP !

[Earl K]

I got to get my Bass bins built ASAP !

Yes, yes you do ;)


Should we start a new thread ? It is a year and a half old !

Nawww, I'm posting here for reference purposes ( just call me the stealth librarian ) .

My concern ( well really the OPs ) is that not all 902s are created equal ( trust the Klipsch crowd to notice this ) .

It's an interesting hypothesis ( though granted , it's pretty academic to those not concerned with crossing over at a frequency less than 1.5K .


Earl I'm using Holm, so what are you using for posting your plots/graphs.And as you know I'm just starting out WRT measuring and I don't have all the resistors,specific caps,etc..

Those recent plots were from ARTA, a program worth @ $125.00 ( I think ) .
- ARTA is overkill for most casual users .
- I also use HolmImpulse , as well as REW .
- REW is freeware and is a better program ( at most things ) than Holm is ( IMHO ) .
- It's ( REW ) nicely setup to do polars, as well as offering an FR prediction for active EQing / which I used when I posted EQ compnsation for your 288-8E ( #1 ) over at Hostboard .


<> cheers

[Zilch]

M19 XO is good for testing out HF comp. Note, however, that the HF level is derived from the lowpass.

I've never tried to move the highpass frequency lower, but the HF comp is done with an adjustable version of 30904/30923, the Altec bridged-T filter, which does work stand-alone, and which they used at 500 Hz, 800 Hz, and 1.2 kHz in both consumer and pro products. That's just five components, and I posted both 8- and 16-Ohm variants here several years ago....

[Altec Best]

[QUOTE=Earl K;297241]
( just call me the stealth librarian )


The Stealth Librarian I like that. :D




REW is freeware and is a better program ( at most things ) than Holm is ( IMHO ) .
It's ( REW ) nicely setup to do polars, as well as offering an FR prediction for active EQing / like I posted for your 288-8E ( #1 ) over at Hostboard .


Thanks Earl I will check out REW ;)

[kwingylee]

Earl, Altec best, Zilch and all:

Thank you for resurrecting this. I was about to order a set of GPA-902-8As to replace by ALTEC 808-8Bs until I saw this thread.

The lack of energy below 1K is not going to work for me as I plan to use this with my Klipsch Jub clone bottoms.

Clearly I need the Altec 902-8Bs, or have something done with the 808-8Bs that I have. II am trying to get more HF extension and smoothness.

Would replacing the 808-8B diaphragms with the GPA lites be a better route? The 902-8Bs are kind of hard to find nowadays.

Happy Holidays

Kwing