Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Topic started by: debk on January 30, 2013, 01:16:21 AM
-
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
-
I saw those. They looked to be in good condition. Was it someone on the board?
And what a deal!
-
They are listed under the members list for our forum, but have not been active for over a year
-
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.
-
Thanks Doc, when I pick them up I was going to look at possible upgrades
Deb
-
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
-
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...
-
thanks for all the suggestions. It will be fun to experiment with them
Deb
-
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.
-
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
-
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.
-
Anyone have any source to get the ST324 tweeter. I was able to buy one on eBay but still need another one
Thanks
Deb
-
http://www.parts-express.com/pe/showdetl.cfm?partnumber=264-360 (http://www.parts-express.com/pe/showdetl.cfm?partnumber=264-360)
-
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
-
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".
-
Bummer!
I see some on eBay at the moment; also I think Amazon. A quick look around suggests it's been discontinued. That's a pity, the phenolic diaphragm is said to sound much cleaner and more relaxed than the titanium one. I haven't listened to the titanium myself. I have some big-ass JBL 2441s with Ti and they do have the "tinfoil" character, so I know I don't like Ti that much. But I am familiar with the ST324 in the Climax, and to a somewhat lesser extent in the Straight 8, and I personally do like it - especially with the Climax tweaks.
For what it's worth, the Raal ribbon is better. However, all ribbons including the Raal have been really problematical as far as crossovers go. We have a decent setup at present in the Bottlehead Big System, but it's probably 60% experimentation vs. 40% measurement/calculation, and it's a multi-amp active crossover setup that has been tweaked for years. I don't know any other ribbon that can go low enough reliably - especially if you like Nine-Inch Nails.
I do have one pair of ST324 in the back corner of the lab (basement), new but in mismatched boxes for some reason, with the same label. I'll never use them, so if you or anyone else wants them, let me know.
-
Paul
If you are offering them I will take them
Deb
-
I don't know any other ribbon that can go low enough reliably - especially if you like Nine-Inch Nails.
I know what we can listen to on the ride to the office next week!
-
@PB, maybe I'll drive myself this time ... :^)
@Deb, they are yours - I'll PM after Hidden Egg Day (insane family holiday, you know...)
-
Thanks Paul
Have a great Easter!
Deb
-
I have been studying the crossover for the ST324 on the climax page. While I understand the the straight 8 version 3 crossover and can calculate values fairly close to the given values. I am having trouble understanding the Climax high pass filter. The Climax ST324 crossover seems to have a crossover frequency of 20KHz. The explanation given on the Climax page if I follow it correctly is that the normal roll off of the ST324 combined with the 1st order 20KHz high pass filter will give a flat response for the tweeter that aproximates a 4th order high pass filter with a cut off around 3.15KHz
Am i close or have i missed something?
Thanks
Deb
-
Yup, you got it right. Imagine that the stock treble response above 3kHz is more or less a first order slope rolling off from 4kHz to about 15kHz. The trick is that the sensitivity of the driver is so much higher than the bass array that the 20kHz 1st order 'bass' roll off actually flattens the falling treble response of the driver and drops the output sensitivity to the same level as the woofers. Below 3 or 4kHz the bass rolloff of the tweeter combines with that first order slope from the cap and makes that nice steep crossover point.
-
Thanks that helped. I have been trying to wrap my head around all afternoon
Deb
-
For what it's worth, we did a lot of measurements that time, and the match with a 4th order Linkwitz/Riley at 3.15kHz is really remarkable in the crossover region - +/- 10-15 degrees of phase, for one thing, which startled the heck out of me when we made the measurement. This tracks through the full 360 degree phase rotation.