Bought a pair of Straight 8's

[debk]

I just bought a pair of Straight 8's on ebay. I feel kind of guilty about it since the auction closed at only $5.50. Told the seller that at that price if he did not want to sell them I would understand, but he was just glad another Bottlehead enthusiast will give them a home.  Still have to pick them up since they are in Vermont about 4 hours from me.   They are said to be in excellent condition.
It will be interesting to see how they sound when I get them.

Deb

[Grainger49]

I saw those.  They looked to be in good condition.  Was it someone on the board? 

And what a deal!

[debk]

They are listed under the members list for our forum, but have not been active for over a year

[Doc B.]

My suggestion is to replace the stock tweeters with Selenium ST-324 slot tweeters and replace the tweeter crossover components with a single cap. Ahh if I could only remember the value...the climax tweeter crossover should have a similar value. Use the last version of the midwoofer part of the crossover linked to the straight 8 page.

The bigger the room, the better. Get as far away from them as possible, at least 12 feet, and they will give you a pretty nice image with smooth vocals and good lower midrange and upper bass. They measure down to maybe 55Hz in the open, probably more like into the 40s in a room. And they will play loud with 300Bs. A sub set to 40Hz will work to fill in the bottom stuff.

If anyone is interested there is a pair at Bottleheadquarters with Aurum Cantus ribbon tweeters and really nice maple cabinets that needs a home.

[debk]

Thanks Doc, when I pick them up I was going to look at possible upgrades

Deb

[Paul Birkeland]

Hello Deb,

If you get interested in installing the ribbon tweeter, shoot me a PM.  I sold my Straight 8's locally many years ago and I ran into them recently and was really sad at what happened to the cabinets when the ribbon tweeter was installed.

For under $100, a custom pair of tweeter mounting plates can be made to replace the stock flanges to fit perfectly in the existing cabinet, and I would draw those up for you if you were interested.

-PB

[Doc B.]

My suggestion would be to use the ST324 over the ribbon. Though the 324 only gets up around 15 or 18 Khz I think they integrate just a little better with the midwoofers. IIRC you can enlarge the tweeter mounting hole by removing some of the recessed part that the stock tweeter flange sits against. Then simply surface mount the ST324 over the hole and do some felt diffraction treatment around the mouth, as PJ describes in the Climax article. BTW with the ST324 in there with that fairly high crossover point the speakers should be able to take a fair amount of power, like 150W easily. I have run them with 75 and 150W amps. They would make great PA speakers for a smaller club. Always thought it would be interesting to make them into active PA monitors by mounting a dedicated digital amp for each driver on the rear. Just add some metal grills over the midwoofers and it would be reasonably rugged - and pretty heavy...

[debk]

thanks for all the suggestions.  It will be fun to experiment with them

Deb

[Paul Joppa]

There were several iterations of the crossover. I still have my notes from the development, so PM me when you're ready to experiment.

For the ST-324, as Doc B said, read the Climax paper (linked off the Community page) - that reflects the most recent work we've done. Lots of fun tweaks! I can give you an appropriate woofer crossover schematic to match it.

We did have a fairly sophisticated crossover for the stock tweeter, which I don't think was actually produced but was disseminated on the Forum. The ST324 is better.

[2wo]

I have a pair of the 8's. I use them for my quote, unquote "home theater" setup. I still drag them out when I want rock out a bit. I bought the ST-324's but have not implemented them...John 

[Paul Joppa]

So I did a bit of poking around and all the crossover information is already posted.

On the Community page, near the top, is the article on the Climax design. The tweeter crossover is suitable for use with the latest Straight-8 woofer crossover (see below). At the time, I actually did that on purpose. Notice all the cool mechanical upgrades we did to the ST324! Each of them was tested and found to be an improvement - the article does not include any of the things we tried that didn't help but there were a few ...  :^)  you will also notice that the tweeter improvements are, shall we say, cosmetically challenged - we had to give up the project before we got that part worked out. Room for your own creativity!

Incidentally, all this was with the phenolic diaphragm 324; there are other versions of that tweeter with titanium diaphragms but they just don't sound as good.

Near the bottom of the same Community page is the last Straight-8 crossover. The woofer portion is suitable for use with the above ST324 crossover. You may notice that the values are NOT classical theory values - they are chosen to work with the actual measured response of the 8's woofer array.

You will also note the fairly complex crossover for the original metal dome tweeter - again, based on our measurements of the tweeter. It was an improvement over the previous two or three designs, though as I recall the difference was not huge.

[debk]

Anyone have any source to get the ST324 tweeter.  I was able to buy one on eBay but still need another one

Thanks

Deb

[Doc B.]

http://www.parts-express.com/pe/showdetl.cfm?partnumber=264-360

[debk]

The part is discontinued and no longer available.

They recommend the ST304 as a replacement.  Any one have any experience with the ST304 in the Straight 8

Deb

[Doc B.]

My apologies, I didn't read the fine print. PJ picked out the ST324 back in the day, so I will let him weigh in on whether the other tweeter would work. I suspect he will say "smoke it and see".