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speakerdave
06-18-2003, 01:15 AM
I am cooking up a plan for improving these speakers. I think I have it worked out, but I wanted to run it by you to see what you think. I have some L65As. The first thing I noticed about these speakers was that the bass wasn't very good. There was obvious cabinet resonance and the bass was so boomy I had to get them a foot off the floor to be listenable. Even then it didn't sound so much like music as it did a little woofer doing a decent job. The mids and highs were good, but so hot that I have the controls turned almost all the way down. I have pretty good amplification available and have tried these with a Mac C20/Audio Research VT60 and a Luxman 1000/McIntosh 2200, my usual amp. In general the fundamentals don't seem to be keeping up with the overtones. It may be that the refoaming the 122s underwent has made them less efficient. The cabinet is not the ideal size indicated by the T/S parameters for these woofers, and it could use some more bracing, but I think I will jettson these woofers and cabinets both. I want to move toward the 4315 and the 250ti. I would be happy to buy a set of these speakers, but they come up for sale so seldom, that I have decided to take action. I have some woodworking tools and speaker-building experience, so that is no problem.

I've assembled some 1400nd woofers and some 2118H mid-woofers to use with the 2105 mids I now have and the 077s from the originals. I have woofer housing recommendations that originated with Greg Timbers. Here's the thing. I can use the original crossovers and bi-amp the woofers, but I prefer not to. I'm now using a Phillips SA1000 straight into the MC2200 since it has input level controls. If I bi-amp I must put a preamp into the chain, and I think none is better. Anyway, I prefer the simplicity of one amp. I would like to cross over the woofers at no higher than 400, preferably 300. What crossover should I use? Any other suggestions would be heartily considered and appreciated.

Thanks,
speakerdave

Robh3606
06-18-2003, 05:59 AM
Hello

You could always do a passive but its big coils and caps that low. With the actives there are several good ones. Some guys like the vintage Crowns, the Marchland kits are supposed to be very good and you can select your slopes. I use JBL M552/553 nice and quiet but slopes are set @24db L/R. You could also grab vintage JBL 5234,5235 to get the job done. Sounds like you will have some nice sounding speakers !

Rob:)

speakerdave
06-30-2003, 12:17 AM
This is a follow-up question to my original posting. The library page on the K2 says that the bass tuning used was Bessel transform because it yields tighter bass, better transient response, at the expense of bass roll off. I am interested in experimenting with this alignment. Can anyone tell me how to achieve it?

Thank you,

speakerdave

listening to
Phillips SA1000 SACD player
McIntosh 2200
JBL L65As

GordonW
06-30-2003, 09:00 AM
The things I would do differently- and this is just my opinion- would be to use the 104-H2 or H3 mid instead of the 2105 (flatter, doesn't have the top-end peaking), and use the 035Ti tweeter instead of the 077. Basically, you'd be making a very close functional equivalent to the 250Ti... but with improved mid and HF drivers. The advantage of this. over the arrangement you mention, would be the ability to cross over the mid to tweeter at a lower point, and therefore, have better dispersion characteristics.

I would think that you should be able to put up the L65s for sale (if you wished to do so- they seem to bring good money- or were you thinking of keeping the parts around for a future re-assembly of the original?), and just buy a pair of 035Tis and 104H2s... and probably have significant money left over...

Also, one thing to check: What is the output impedence of the Philips CD? Amplifiers are designed to be driven by a relatively LOW output impedence, lower than line level, in many cases. The peak signal levels into an amp, can also exceed normal line-level signal levels, to reach the maximum output of the amp for dynamics. In some cases, systems actually sound BETTER by the addition of a preamp, just because of the improvement in the gain structure of the system... and if this is the case, then active crossovers would be easy enough to rationalize, once you're to that point.

IMHO, active bass crossovers almost always sound better than passive crossovers in that region. It's just a matter of getting passive crossover components (especially inductors) of the sizes needed, that can do the job without saturation on peaks. We're talking MONDO inductors here... like coils the size of a mixed nut can, in some cases, for drivers of the power handling of the JBL woofers you mention...

Regards,
Gordon.

speakerdave
07-02-2003, 03:36 PM
Gordon, thanks for your response with its many useful ideas. I am using the old midranges because of their Alnico magnets--well not specifically the Alnico. It's the low-loss structures. Because of the layout of my room and the TV placement my speakers are quite close to the CRT. Those old JBL magnet structures with the cast pots really emit very low stray fields. I swapped out the LE5-5s that were stock and put in some 2105s. I'm not sure I can hear a difference in how they sound. If anything the LE5-5s were smoother, but the swap takes so long, it is hard to tell. I'm hoping I will be able to cool down the midrange a little bit when I come to building crossovers.

You make a good point about selling off the L65s. I've thought of doing that, but going into the market for a pair of 077s just about negates the economic benefit, and the ones I have are very clean, very mint. I hate to think of parting out a mint pair of L65s, but I may end up doing that.

Your point about the output impedance of my SACD player has me wondering. My manual doesn't give me that number. The McIntosh 2200 has output transformers, so its input impedance is much higher than most solid state power amps. Would that help?

Thanks,

speaker dave

GordonW
07-03-2003, 12:54 AM
You know what would be interesting? Get a pair of LE5-2 or other alnico can-magnet baskets, and load them with a 104-H2/3 cone assembly. Giskard, shouldn't that fit? If so, you could have what amounted to a video-shielded 104-H2...

However, if you're attached to the 077s (and I can't say I blame you, they're rather addictive in some ways :-) ), then using the 2105 with them may be a better idea, due to the lower cone damping and mass of the 2105 (ie, it'll go higher, faster). I see no real reason why a good crossover computermeasurement and modelling program (Speaker Workshop, SoundEasy, etc), shouldn't be able to work out a good blend with that and the 077... I'd try to stay in the 6000-7000 Hz range, with 18 dB highpass on the 077, for safety, and let the program optimize as much as it can.

Also, I was just thinking about it- I think the 2105 is also more efficient than the 104-H2. With a 2105 and the right crossover tweaks, you might be able to do a 3-way with the 2118, with just a little padding on the 077... a VERY HIGH efficiency midbass-and-up section. This reduces the load on the mid-high amp with a bi-amp situation... more headroom!

Regards,
Gordon.