brother

A second photo.

The attached photo is a custom built Heresy based center to match my LaScala mains. The cabinet size is an exact match for the LaScala tweeter and mid section. It is built to provide an F3 of 53 Hz using Focal woofers. I built the crossover to match the modified type A's in my LaScalas using Solen inductors and Hovland caps. The sound matches the LaScala's seamlessly. The rotated mid and tweeter work very well in my HT room configuration, but would need to be evaluated for each specific case.

The easiest way to convert the AA to an A is to go from terminal 5 on the autoformer to one of the 2 mF caps and then directly to the tweeter terminal. This will bypass the second 2 mF cap, the 245 microHenry inductor and the tweeter protection switches and give you a type A crossover. A word of warning: the tweeter protection switches are there for a reason. Although the high frequency energy is much lower than the mid or bass, high power signals can overrun the capabilities of the tweeter and some tweeter models are more vulnerable than others. One watt will not hurt them (on a LaScala that is 104 dB...loud!) and I believe others have estimated very high SPL's before issues could occur(personally I don't like to take chances with tweeters). Also, carefully trace the wiring as you make the modification to ensure accuracy.

I kept my AA's intact rather than modify them and built a set of modified type A's for my LaScalas using Hovland caps for the HF and Solen inductors and caps for the mid (with a 3619 autoformer)and bass. I listened to the original type AA's for a couple of months, ALK's for a couple of months, and then installed the modified type A's. I prefer the modified type A's.

Try speakercity.com they have a fair sampling of top quality drivers. All the other suggestions are good as well.

Guitars sound "sweeter" with age due to slight variations in the resonance of the strings/body/pickups. The wood type, construction, and age all figure into this and provide a coloration of the sound; this is why performers use various tube types and guitar types to get the "sound" the want for a particular song (example: Eddie Van Halen and his famous "brown sound"). Most of this is the interaction of the body/neck and the pickups. This is why a Les Paul sounds so different from a Fender Stratocaster. Speakers on the otherhand do not necessarily (and normally don't) rely on wood resonance to get a particular "sound" as they are designed to be accurate reproducers of sound, not producers of sound. The speaker manufacturer wanting to provide accurate audio reproduction would not want a varying color added to the sound due to the age of the wood; this would be a negative effect. So, the best solution to the finishing issue to provide the best sound would most likely be to get a high quality or DIY natural finish to the wood and enjoy the beauty. Good Luck and happy listening!

I think the processed sound is noticeable as well. Again, I am not familiar with the Onkyo, but the 3803 has what they call a "pure direct" mode that bypasses all the processors and sends the input directly to the amplifiers in 2 channel stereo mode. This is my standard music listening position, but could be used for monophonic audio or standard TV listening. That doesn't keep the center going though. You might also check into boosting or limiting the various channels and saving that configuration as a mode. This may be a case where HT killed the audio "star".

Look at the settings on your Onkyo - you may be able to change the mode and make standard program audio distribute around the system in a simulated surround mode. My Denon does this and it sounds better. I have experienced this same condition and playing with the audio modes will give you some relief.

The grille is original Heritage grille cloth. I put one of the LScala grilles on it for the photo so you could see how the finished product should look. I'm trying to locate a portion of the cloth for the center and a subwoofer that is under construction.

A second photo.

Attached is my Heresy based center designed to match the timbre of my LaScala mains. Using the same vintage mid and HF drivers and a set of Focal 7" woofers provides an exact timbre match to the LaScalas. I'm very pleased and with an F3 of 54Hz, they are well rounded. The crossovers utilize Hovland caps and Solen inductors to provide the same crossover points as the original Heresy and match the sound of the modified A series crossovers in the LaScalas. The blending of the mains and the center is excellent. The cabinet design and construction is built to match the face size of the mid and HF section of a LaScala. The grille has the same dimensions as the LaScala grille. The horns are mounted vertically to make it all fit though there was originally some concern about dispersion patterns. After obsessing about it and calculating all of it ad nauseum, the dispersion pattern was found to be more than sufficient to provide uniform performance in my HT area. This has been verified by SPL testing. Of course, sitting arrangements in other rooms may vary and the performance testing verifies my HT room configuration only.

I am not familiar with the 910's, but I used to have a pair of ADS 620's that I was very fond of at the time. A buddy had recently purchased a pair of Heresy's (this occured about 1977 or 78) and we did a major A/B sound test on them. They were very comparable to the Heresy. As I recall the Heresy was considerably more efficient, but the sound was similar, although we both gave a slight edge to the Heresy. We were running them through a Luxman receiver of the same vintage. If you can find components for the necessary replacements, I'd say they are definitly keepers.

My LaScalas are 1987 models with a modified type A custom built crossover network. I'm driving them with a Denon AVR-3803 receiver and use a Hersey based custom center channel for "timbre" matching in the HT system. I just finished the center last week. After I give it a more diverse "hearing", I may give some comments on it. My brother calls it a "Frankenstein", but I swear you can't see the stitches and bolts.

Here is another run at trimmimg out a LaScala. I used 3/8 by 11/16 cherry strip to cover the raw plwood edges. It gives a nice finished look to the LaScala.

I think the cost of the various quality caps (Solen vs Hovland or Jensen) has more to do with the manufacturing process than the quality or performance. The metallized polypropylene uses a thin film deposition technique to apply metal to the PP, where the film and foil; and paper, foil, and oil use a wound layering of film and foil. I think the film and foil caps just cost more to produce. It seems the film and foil caps show the most improvement in the HF range and have a marginal if any effect in the mid frequencies. Using a Solen in the HF may work as well as a Hovland. I used Hovlands in the HF of the modified "A" I built and am very pleased. Al K. has probably tested both and may be a good resource. As you know I'm sure, cost doesn't always mean performance.

In response to Al K.'s suggestion about a poly switch, I have revised the schematic to provide a .5 A polyswitch for those who may prefer it. The polyswitch will open at 2 watts and provide the same limiting as the bulb. It will automatically reset when it cools and restore the circuit. It is done in the same fashion as Klipsch applies it in some of their other crossover networks. At this point, I prefer the uninterupted limiting of the bulb to the switch. But this is offered as an alternate means of providing tweeter protection. Unless you're really cranking the system, a person won't hit the danger threshold on the 5 watt K-77's using either version. Obviously, the older 2 watt versions will be more susceptable to problems. Either solution will address the issue.

The attachment shows a revised schematic for the crossover with an additional resistor to balance the network to 8 ohms with the inclusion of the #561 power limiting bulb (the bulb adds 0.9 ohms to the high freq circuit). An additional effect is that the tweeter sensitivity is now balanced with the other drivers at 104 dB/W/m. The bulb limits the power to 2 watts and should keep the tweeter from being overpowered. Another option would be to use a 3.0 mF tweeter cap and omit the resistor to maintain the 6K crossover point.

2.83 volts @ 1 watt into an 8 ohm load. The voltage on motor start caps will normally be upwards of 120 volts depending on the motor circuit they're applied to. Audio usage won't push the voltage rating at all in most cases. For instance 100 watts into an 8 ohm load gives 28.3 volts. If you are using Heritage series speakers, cover your ears!

This is the schematic for the crossover including the tweeter protection.

Sounds like the old bait and bait and bait and.........

Tweeter is running a 30% off sale on Denon, Klipsch, etc. in town. It may be nationwide. Get 'em while their hot!

Klewless concern is valid. The crossover rolls off at 6K @ 6dB / octave which is more than enough to stay out of the driver's lower limit if you project the curve on the tweeter response plots I had for evaluation. John's suggestion of utilizing the light will aditionally help limit the power to the tweeter and is an addition I will make to help protect the driver. That additional component was intended to be included, I just didn't get them before I had the time to build the networks. It's an easy mod. I've just got to keep the teen out of the volume until then.

Thanks Al! Actually, all the terminals are soldered; I used the ground lugs because of difficulty obtaining the posts you use. The connections are banded, soldered, and then placed in the lugs to secure them. The ring connectors are tin plated copper crimped and soldered onto the wiring before attaching to the terminal strips. The circuitry is a low pass, bandpass, high pass with each element directly fed from the positive signal terminal ( a variation of the published crossover). Many of the other circuits I've seen pull the tweeter cap from inside the bandpass cap. I chose to do it differently. The inspiration (?) comes from a 1958 article by PWK on LPads where he shows a new crossover similar to this one. The idea is to eliminate all possible insertion losses, etc. Obviously, the bandpass section is more complicated due to the squawker driver characteristics. Cut Throat, the inductors are mounted just as Al K does using holes drilled into the mounting board and plastic tie wraps threaded through. The Al's design helped me a lot on these types of details.

I finally finished my first order crossovers for the LaScalas this weekend. These are inspired from PWK's preference and the quest for simplicity in design. I thought you guys might like to see them. I've only listened to them for a couple of days, but the sound is simply sparkling. The improved clarity and definition of string instruments is the most noticeable and harmonizing vocals are improved as well. The bass is strong for the LaScala and as expected is very tight. I played the Eagles "Hell Freezes Over" DVD and it was remarkably improved over the stock Type AA crossovers. I lost my electronic version of the wiring diagram in a hard drive crash, but will soon redraw it and will post it as well.

The Denon 3803 is a winner. They make several models one of which will be in your price range. They downgrade power supplies and processors the farther down the line you go, but all have a nice sound. Listen a play with lots of models and brands and you will find the one that best fits your needs. The best advice is to take your time when evaluating.