Adding a supertweeter to Model 19s

[travisty]

Greetings all,
A friend has a pair of super-tweeters which he has offered to loan me and I wanted to see if my otherwise stock M19s would be improved if I added some.

Being far from an electronics guru, I would love some advice on the easiest appropriate way to add them in.

If anyone has done this before, please add comments about crossover frequency.

The M19s are being driven by an EAR 859 integrated amp (big OPTs, 13W, should push 4ohms and up).

[Mr. Widget]

More info on the supertweeter would be needed to give you any really useful advice... a proper supertweeter is likely an excellent idea though.

There may be something of use for you to glean from this thread... as I recall, people got off on some weird tangents, but it is more or less related to your subject.

http://www.audioheritage.org/vbulletin/showthread.php?t=14690


Widget

[travisty]

I actually read through the whole thing today (all 59 pages) and gleaned that the Valencias could be improved, and that the 19s might not be worse off for a the addition of a super-tweeter. Fascinating thread!

That said, I am wondering what the best way to accomplish that is... because in that thread, while the Valencias eventually had a couple of good recipes completely unveiled, the actual implementation of the 19s' changes was hinted at more than revealed.

Anyone have any experience adding supertweets to 19s?

[travisty]

The borrowable tweeters are Fostex GS90As. I can also get my hands on a pair of Fostex T90As.

[Zilch]

That said, I am wondering what the best way to accomplish that is... because in that thread, while the Valencias eventually had a couple of good recipes completely unveiled, the actual implementation of the 19s' changes was hinted at more than revealed.The problem is integrating a tweeter into the system, and we found the best answer was to mount it within the horn, which implies finding one small enough and then optimizing its location to minimize effects on the horn's output.

We subsequently determined that the Altec compression drivers commonly used on 811B in M19 had other issues, HF response undulations, namely, further arguing in favor of the alternative solution developed in that thread, BMS 4550 or 4552nd, both of which have higher sensitivities than the Altecs, and require a supplemental L-Pad, fixed or variable, to bring them down into the "Optimum" adjustment ranges of the M19 crossover controls.

Several members of another forum did a group buy of 4552nd, and those who used them in M19s reported excellent results. One member of this forum has decided to go back to Altec drivers; the BMS solution works too well for some "vintage" listening preferences, apparently.... ;)

http://audioheritage.org/vbulletin/showthread.php?t=23067

[stuck.wilson]

'doh...

called out!

a new crossover topology can work wonders too, i hear ;)

i'll give ya that they'll go high, fo shiz, as they say....

[travisty]

Thanks Zilch,
I had kept those two points in my head but somehow I had thought you had said 'wait a minute I'm still working on something' after that.

I assume the 8 ohm version is the one to go for. What L-Pad values do you recommend?

Is it a fairly simple drop-in mod?

[DaveV]

Travisty,

Since you can borrow the tweeters you have nothing to lose by trying what I did in adding tweeters to my Model 19's.
It's worth a shot for the cost of some caps if you don't already have them.

I am not at all unhappy with the results of a simple 6db/octave xover at around 18,000 HZ that I now have by using 1uf caps in series with the tweeter.

The tweeters are wired direct to the amp speaker terminals in parallel with the 19 wires as in a bi-wire setup. (not bi-amp) and I have the tweeters sitting on top of the 19 cabinets toward the back edge.

Theres no change to the 19 xover so the 802G's are running full out and I find in my system I need to set the so called HF xover controls at the o for optimum rather than into the optimum zone.

Try reversing the leads on the added tweeters, red and black (or plus and minus) and try different front to back locations.
My setup sounds better with the tweeters (EV T-350's)reversed in polarity from the 19's and set toward the back edge of the cabinets.

Once in a while I disconnect the tweeters and turn the HF controls back up only to find that I don't enjoy the 19's without the added tweeters.

The EV T-350's aren't really "super tweeters" because they start rolling off around 14KHZ so I know I'm not adding much extension to the high frequencies BUT it seems to me the reinforcement to the dropping response of the 802G's plus an added extension of maybe 3KHZ makes a huge difference to me.

I tried HF EQ and also setting the HF controls at max but I was not at all happy with the resulting "lift" from the 802G's. I thought the result was distorted and garbled sound and the added tweeters sound far better to me.

I think it's worth a shot before you go to other more complicated or costly routes but you do need tweeters that are pretty efficient.
My EV T35's and Altec 3000's didn't do it.

[Zilch]

I assume the 8 ohm version is the one to go for.Yes.


What L-Pad values do you recommend?Seems to me I recall it was somewhere in the range of 6 - 8 dB additional attenuation required. Best answer is to start with adjustables, and once you get everything balanced to your satisfaction, measure the resistance values to convert to fixed L-pads.

Having response measurement capabilities helps with this, too. Adjusting the balance and comp of M19s is tough without that. You can get it "by ear" eventually, but "eventually" is the operative term here.


Is it a fairly simple drop-in mod?Direct swap of the drivers, yes. You'll need the right size metric bolts for BMS, is all.... :yes:

[robertbartsch]

I did this 30 years ago with a pair of Altec VOTT. I added JBL 077 slot tweeters (UHF) and JBL crossovers.

This worked well since the drivers all had similar sensitivities rating.

Altecs are VERY efficient drivers, so I assume this will be your biggest issue.

[Zilch]

Altecs are VERY efficient drivers, so I assume this will be your biggest issue.Uhmm, we just discussed that the BMS drivers have to be ATTENUATED to balance with M19 LF.

Do we know the actual sensitivity of the Altec drivers after filtering in M19? :blink: