New Tweeter for Forte ll ?

[moray james]

Have been thinking about upgrading the tweeters in my Forte ll
speakers. On my consideration list are the Beyma CP25 which has been
sucessfully used to replace the T35 or K77 by Electrovoice. There are
also some other Beyma models which look very interesting and might be
worth consideration. Each of the following have very good response both
on and off axis. They are the SMC2012/N which has incredibly smooth
response, the SMC8060 and the CP12N which is vey smooth and while a
conical horn is well controlled at 40 degrees. I do not know what the
dispersion characteristics of the Forte ll mid horn is and am wondering
if any of the faithfull here do. While a similar polar response is
probably a safe bet for intigrating a new tweeter into the Forte ll the
tight polar response of the CP12N seems very attractive and might help
minimize room interaction though the price to pay for this will probably
be more toe in than is normal with a Forte ll. I have not yet found out
what the prices of these tweeters is but I have sent out a request to
Greg Roberts at Volti as he is a Beyma dealer (I would like to support
those who contribut here) for unit costs. I would expect that since the
CP25 costs about $125.00 each the other tweeters on my list are likely
at least that much or or possibly more and that may well be the deciding
factor. Like most I don't want to spend any more than I feel I have to.

As an aside of interest would be any horn replacements which
any of you have found to be sucessful. My guess is that it may be the
horn of the T35/K77 which is responsible for a large part of how this
tweeter sounds and that the stock phenolic compression driver may in
fact be perfectly suitable if mated with a new horn. This approach would
also negate any need to touch the crossover in the Forte ll and the
only modification necessary would be to the baffle itself. Your
comments would be most welcome and any accounts of your experience with
any of these or other tweeters or horns would be most useful. Thanks in
advance for any assistance regarding this matter.Best regards Moray
James.

www.beymaamerica.com

[wuzzzer]

I've been extremely pleased with the tweeter diaphragms listed in my signature below.

[moray james]

Wuzzer: thanks for the comment regarding your titanium domes on the T35's. Many here seem very pleased with them. I did consider that route but it is almost a third of the cost of a new set of modern tweeters. While the T35's don't sound bad they have a scary response curve and roll early. I see them as the real weak link in the forte ll. I don't suppose that anybody has a set of curves with the new metal domes on a T35 do they?

Regarding the new tweeters I think I have decided upon a set of Beyma slot radiators the CP21F. Very good response to 20K and smooth both on and off axis 105 efficient 140 degrees horizontal and 40 degrees vertical. Am hoping this will blend well from a dispersion point of view with the tractrix mid horn on the Forte ll . I may have to pad it down but I don't think that is likely and the only real change will be to install it on the baffle.

Can anybody here point me to any threads pertaining to the Tractrix mid horm in the Forte ll? I am particularly interested in curves showing the response on and off axis efficiency and the xover point in the Forte ll. Thanks in advance for any assistance. Regards Moray James.

[djk]

The T35/K77 was never used in the Forte, and there is not a titanium diaphragm available for it.

There is a titanium diaphragm available for the Quartet, Heresy II, Forte, etc. BEC has graphs on it, it looks good.

[moray james]

DJK: thank you very much for catching me I really appreciate it. I have had the speakers all of two weeks and the previous owner told me the tweeter was a T35. I must admit to being very careless in that while I have had the grills off a half dozen times I did not stop to really look at the tweeters. I was much more interested in the mids as I was told they were very good. Do you have any links to data on the drivers and horns in the Forte ll? I have been looking and found a post which said the Forte ll tweeter is a K75K and the mid is a K61K is this correct?

Is there info on these units curves efficiency and dispersion? I would be most interested to see the response of the K75K to see how it compares with the K77. If the forte ll tweeter is in the 101 db range that means that the Beyma SCM2012/N could be a good replacement choice. Thanks again for you help. Regards Moray James.

[moray james]

Have been doing my homework and found this so no curves though.

Specifications

FREQUENCY RESPONSE	32Hz-20kHz(+-)3dB
POWER HANDLING	100 watts maximum continuous (500 watts peak)
SENSITIVITY	99dB @ 1watt/1meter
MAX ACOUSTIC OUTPUT	119dB SPL
NOMINAL IMPEDANCE	8 ohms
CROSSOVER FREQUENCY	HF 7,000 Hz LF 650 Hz
MAXIMUM ACOUSTIC OUTPUT	119dB SPL
TWEETER	K-75-K 1" (2.54cm) Polymer diaphragm compression driver
HIGH FREQUENCY HORN	90(o)x40(o) Exponential Horn
MIDRANGE	K-61-K 1.5" (3.81cm) Phenolic diaphragm compression driver
MID FREQUENCY HORN	90(o)x40(o) Tractrix® Horn
WOOFER	K-25-K 12" (30.48cm) Fiber-composite cone active / KD-15 15" (38.1cm) Fiber-composite cone passive
ENCLOSURE MATERIAL	Medium density fiberboard construction (MDF)
ENCLOSURE TYPE	Bass reflex via passive radiator
DIMENSIONS	35.4" (89.92cm) x 16.5" (41.9cm) x 12.25" (31.1cm)
WEIGHT	67 lbs. (30.42kg)
FINISHES	Walnut Oil, Oak Oil, Oak Clear, Finished Black
BUILT FROM	1989
BUILT UNTIL	1996

[John Chi-town]

Scour the internet you can find graphs out there as I have before. I, like Wuzzer believe that you will be very happy with the result of adding Bob Crite's Titanium replacements on the tweeter.

[djk]

http://forums.klipsch.com/forums/p/49715/472087.aspx#472087

Anyway, the blue is the common soft poly dome, the red is phenolic and
green is titanium. The poly (blue trace) drops off a lot just above 15
Khz. The titanium (green trace) continues on up to around 18 khz. The
phenolic (red trace) is right there with the titanium, in fact going a
bit higher before it drops off.

I would give a slight nod to the
phenolic based on this test. Problem is the phenolic is no longer
available. So the titanium beats the poly and those (poly and titanium)
are the only ones you can buy as far as I know.

Now we could say
it this way. If I had a diaphragm go bad in one of these tweeters, I
would replace both with titanium. If I had phenolic to start with, I
would keep using them and replace them with titanium once one had
failed. If I had poly in these tweeters, I would replace it with
titanium.

Bob Crites

[moray james]

Thanks DJK: I just saw that set of comparrison curves and that was my impression also. Several members had commented likewise. I spoke to Bob C yesterday about how to compensate for a new tweeter witha different efficiency from the stock K75K,. Bob suggested to use an auto transformer as the best way to adjust the tweeter level. So I am still thinking that the Beyma SMC2012/N would be an excellent replacement from a response point of view. It is one of the smoothest compression tweeter units I have yet found regardless of cost. The only issue is its tighter dispersion in the horizontal plane at 50 degrees. I wonder if this willl cause issues when the mid horn (at 90 degrees horizontal) crosses over to the Beyma at 50 degrees horizontal. Any coment regarding this would be most welcome. I suppose that with the Beyma SMC2012/N only costing about $70.00 each it might just be worth while to bite the bullet and get a set then try them out. I would expect it to sound excellent.Thanks for the help. Regards Moray James.

[BEC]

Things have changed some in the 6 years since I posted that set of diaphragm curves. I have better equipment now and I have a completely different titanium diaphragm now that was not available in 2004. So, the trace below will update things to modern times.

Bob Crites

[BEC]

This test was done with the same K-76K tweeter. We ran the exact same test on the tweeter each time just with a diaphragm change between traces.

For a quick analysis, we can see the major difference is the drop off in high frequency response between the three different diaphragm materials. If we look at the titanium diaphragm output near 20khz compared to the phenolic and poly, we see that the phenolic is about 6 or so db lower and the poly is about 10db lower.

The phenolic and poly are both original (new) Klipsch diaphragms.

The titanium diaphragm used in the 2004 test was a new one from Klipsch. The titanium diaphragm used in today's test is my titanium replacement.

Bob Crites

[moray james]

I was given the suggestion to have a look at some Fostex tweeters. The FT17H looks very good at 98.5 db efficient and with excellent extension way past 20K. If the response graph is accurate it is the smoothest tweeter that I have found so far.

[djk]

It doesn't look any better than the stock tweeter.

"If the response graph is accurate it is the smoothest tweeter that I
have found so far."

A huge amount of smoothing has been applied to those traces.

[moray james]

Well that's the problem the fostex response graph is not exactly one which instills confidence. I can't do a measurement so I can't check it I can only listen. I had a set of the Fostex a few year back for another project and they were very smooth and did not draw attention in any way.I guess that I could look for some of the stock Forte Mk l tweeters and exchange the diaphragms but that seems like a project. The undercurrent seems to be that the stock tweeters are good. I just thought that better might be available by now. I have not seen any one inch exit comp drivers which are flat and extend to 20K for the tweter though I have found a couple of tweeters that look the part. Nor have I found any affordable one inch comp drivers that will extend low enough to replace the driver on the K61K mid horn. Are there any who have done any upgrade mods to the stock Klipsch compression drivers? If not I will have to leave well enough alone. Do any of you know which Klipsch horns use the same phenolic tweeter diaphragms as in the Forte l ? That way I can keep my eyes open for a set if they show up used and then be able to run phenolic diaphragms on both the mids and the tweeters.Regards Moray James.

[wuzzzer]

If you go to Bob Crites' website he lists the horns that are compatible with his titanium diaphragms. That could help you in your search.

I still think you should give his titanium diaphragms a try. For about $60 its a pretty small investment.

http://www.critesspeakers.com

[moray james]

Thanks Wuzzer: for the information. I asked Klipsch about when the made the change from phenolic to poly in the tweeters. Their response is in blue below. I may just end up going with Bob's new titanium diaphragms for the tweeter, time will tell.

Is there anybody who has measured the efficiency of the K61K and the K75K drivers? Bob said that 99 db ought to do for a replacement driver. If I change the tweeter it would make sense to use a horn with the same horizontal dispersion as the stock one. If I decide to stay with the stock tweeter horn then I could be loooking for a comp driver with very smooth response from about 4K to 20k and then deal with the level compensation in the crossover. Starts to turn into a project huh? I will continue looking for the time being but those BC Titanium diaphraqgms are looking better each day.

The
forte II actually used phenolic as the forte did, even though the web site says
poly in the II

Phenolic
was used up to and maybe past the KG-5.5 as I have found phenolic in KG-5.5
factory tweeters

Current
replacement dia kits use poly.

Phenolic
suppliers have dwindled and poly dia offered tighter tolerances over
phenolic.

[moray james]

Last friday night I took the Forte ll's over to a friends place for him to use while he works on a set of ESS Heil AMT 1D's. We worked and listened and after some play with the position the Forte's got happy. I have to say that this being the first chance I had to listen to them with some horse power and they are great. First audition at the last owners home was on a Grant Fidelity 300 B set amp and they sounded very nice. This time was on a fully rebuilt Sansui AU-Dll Mkll at 130 watts per channel fully balanced and bridged amp with ultra low distortion. I have to say the stock Forte ll exceeded my expectations. As for the tweeter horn I really don't think I could justify the necessary work and cost involved and the possible miss match in switching them out. With the phenolic diaphragms they sound excellent, smooth open and they don't distract in any way. I will likely try a set of Bob's titanium domes after I upgrade the mid diaphragms with the new phenolics later this week. Reports here would indicate the titaniums (for the tweeters) sound excellent. As they stand now the tweeters in the stock condition don't sound like they need to be replaced. So it was an interesting time looking into all of this and I very much appreciate the assistance from the fine folks on this forum. I will buy a set of Bob's titaniums soon and try them out and report back as to my findings. As it stands I thank PWK for a job well done and I am most pleased to have joined a community such as this one. Best regards Moray James.