Testing one horn/driver now.
Mic shows 360Hz is where things start to get better...much below that, it looks wobbly.
Interestingly, the driver plays very high.....12k+
I have some spare 500Hz 'Altec' xovers which will make for a good starting point. I'll also test MiniDSP with a second amp, using multiple xover points for sound quality checking.
Adapters worked well using hex screws.
Mic shows 360Hz is where things start to get better...much below that, it looks wobbly.
Interestingly, the driver plays very high.....12k+
I have some spare 500Hz 'Altec' xovers which will make for a good starting point. I'll also test MiniDSP with a second amp, using multiple xover points for sound quality checking.
Adapters worked well using hex screws.
Attachments
Your vertical scale doesn't help you much in seeing what is happening. Looks like you are using REW. On your top right side there is a button with an icon that is supposed to look like a screen with a vertical and a horizontal arrow. Hit that and adjust the vertical scale.
Are you planning for a tweeter on top, or this one should do from approx 360Hz on up?
Thanks Lew...I haven't had a lot of experience with REW...plus I only had a few minutes tonight.
I have a small 1,500 tractrix horn and D220Ti Selenium driver. I'll add this into the bass cab, at the top.
I'll use a simple first order xover, say, 6,000Hz.
OK, see mic recording with axis adjusted.
Dip at 500Hz must be xover related, will need to fix. It's a wobbly reading.
On the tweeter/high freq, the bottom line is with mic centred, middle is with tweeter brought forward to the horn edge, top is with mic extended up to match tweeter height.
The attenuation is OK.
The overall sound is great, very lively, big output, detailed sound stage.
Dip at 500Hz must be xover related, will need to fix. It's a wobbly reading.
On the tweeter/high freq, the bottom line is with mic centred, middle is with tweeter brought forward to the horn edge, top is with mic extended up to match tweeter height.
The attenuation is OK.
The overall sound is great, very lively, big output, detailed sound stage.
Attachments
that midrange dip is deadly. this is what you should be getting out of these mid format altecs that are working properly. this is pink noise 3 feet out from horn center with 288g and a 4th order 400 hz crossover. the 290 will probably only do 5-6000 on top - that's what my 292's do
http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=10380&stc=1&d=1128814078
http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=10380&stc=1&d=1128814078
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Thanks. I'm feeling a bit discouraged after all the work put in.
One horn has the throat a bit rough, with 1-2mm overlap with the adapter...I'll smooth that out.
There's still magic with the sound. Phenolic adds warmth/body without much loss of detail (zing normally associated with titanium etc).
One horn has the throat a bit rough, with 1-2mm overlap with the adapter...I'll smooth that out.
There's still magic with the sound. Phenolic adds warmth/body without much loss of detail (zing normally associated with titanium etc).
If we all quit after a failure, we'd still be clubbing women over the head and living in caves
Do or do not, that is the question yes.
For what it's worth, I've seen speakers with hideous graphs that sound superb.
Sit back and enjoy the music for a bit.
Then start planing your next colossus
I don't think you have your measuring system set up right. I have no doubt it sounds good and those horns you built are fantastic. The notch is likely an out of phase midrange driver
Test @ ~88-90dB SPL @ mouth. Use a ~20ufd film cap in series with the driver. No other xover.
You will have no problems and not hurt the driver.
Build ur own xover, imho.
Best would be to do a biamp, with as much of the xover as is needed in the amp. Perhaps a single cap (as suggested above) as a "safety". (although probably not needed, since the diaphragms can be had)
If you don't use high power on the driver, then the effect of the single cap will be to make the excursion of the diaphragm essentially the same as frequency goes down. Now this is NG for PA/SR, but if ur total available power is somewhat less than or equal to the max power rating for the diaphragm/driver, AND you run typically at ~90dB SPL @ listening position in a typical room, ur way under the max excursion of the diaphragm at all frequencies. IM due to excess LF ought not be a significant issue, imo.
I've run other compression drivers for years and years with only the single cap, and flat down to ~250Hz. Even played live guitars/keyboards/bass/e-drums into the system as monitors (in a 14' x 33' room) at average <100dB SPL in the room, no issues. Altec diaphragms (and most all others) are stiffness controlled by the surround and so have mechanical excursion "limiting" to a great extent (yes, you can still overpower them and mess them thoroughly by dumping big LF into them) that is more than sufficient to prevent any damage in most home hifi uses.
Ymmv.
_-_-
PS. the non flat, sort of upside down bowl look to the freq response curve makes hifi use of most Altec compression drivers somewhat problematic - especially when one tries to run them below the ~1kHz point, because they tend to slope down both lower and higher in freq. This was good for their original application, voice/speech clairity, in PA work.
You will have no problems and not hurt the driver.
Build ur own xover, imho.
Best would be to do a biamp, with as much of the xover as is needed in the amp. Perhaps a single cap (as suggested above) as a "safety". (although probably not needed, since the diaphragms can be had)
If you don't use high power on the driver, then the effect of the single cap will be to make the excursion of the diaphragm essentially the same as frequency goes down. Now this is NG for PA/SR, but if ur total available power is somewhat less than or equal to the max power rating for the diaphragm/driver, AND you run typically at ~90dB SPL @ listening position in a typical room, ur way under the max excursion of the diaphragm at all frequencies. IM due to excess LF ought not be a significant issue, imo.
I've run other compression drivers for years and years with only the single cap, and flat down to ~250Hz. Even played live guitars/keyboards/bass/e-drums into the system as monitors (in a 14' x 33' room) at average <100dB SPL in the room, no issues. Altec diaphragms (and most all others) are stiffness controlled by the surround and so have mechanical excursion "limiting" to a great extent (yes, you can still overpower them and mess them thoroughly by dumping big LF into them) that is more than sufficient to prevent any damage in most home hifi uses.
Ymmv.
_-_-
PS. the non flat, sort of upside down bowl look to the freq response curve makes hifi use of most Altec compression drivers somewhat problematic - especially when one tries to run them below the ~1kHz point, because they tend to slope down both lower and higher in freq. This was good for their original application, voice/speech clairity, in PA work.
Altec drivers tend to peak a bit around 2K - not any more than any other mid - large format drivers though. It can be typically be eq'd flat with a cap inductor and resistor though. His graph indicates he is measuring wrong, the bass and midrange are out of phase or the Altec CD is broken.
OK, back from lovely Queensland holiday, tough.
I've done close to what Bear suggested, although I only had caps up to 16uF...which gives a theoretical 2,400Hz xover point (as opposed to approx. 2,000Hz if using 20uF cap).
The bass is staying with the existing xover (500Hz, LR2)...however, I also have a 1,650Hz Altec xover I can use to test the bass on that.
The tweeter is running from 6,000Hz, with single cap.
The attached sweep shows big rise...but then 'levels out' to 5,000Hz.
I can say that it sounds great...'free-er' sounding, big, airy.
I'll invest in a quality 20uF cap to test further....possibly even a larger cap, 30uF gives theoretical xover point of 1,300Hz. Surely, that enough protection?
I'm just typing this listening to Oscar Peterson, Night Train...sounds like in a live bar...cool.
I've done close to what Bear suggested, although I only had caps up to 16uF...which gives a theoretical 2,400Hz xover point (as opposed to approx. 2,000Hz if using 20uF cap).
The bass is staying with the existing xover (500Hz, LR2)...however, I also have a 1,650Hz Altec xover I can use to test the bass on that.
The tweeter is running from 6,000Hz, with single cap.
The attached sweep shows big rise...but then 'levels out' to 5,000Hz.
I can say that it sounds great...'free-er' sounding, big, airy.
I'll invest in a quality 20uF cap to test further....possibly even a larger cap, 30uF gives theoretical xover point of 1,300Hz. Surely, that enough protection?
I'm just typing this listening to Oscar Peterson, Night Train...sounds like in a live bar...cool.
Attachments
OK, I've now added 26uF cap(s) to the horn....plus decreased the attenuation a little.
Also, I swapped the bass over from a 500Hz xover to a 1,600Hz xover. (Remember I'm using Altec 420A woofer which goes high.)
I'm really enjoying the overall sound.
I think I need a few more resisters to play with for the mid horn, as I jumped from about 47 down to 30...with nothing in between. Plus the resistors are puny 10 watt versions.
Next few days, I'll resand the horns and paint more.
Plus I'll add more dampening into the cavities of two sections, as they appear to echo a little compared to the other sections, when knocked.
All good fun.
When I see Wilson Audio promote their new WAMM product for $600k(?), I really wonder about that and how nice it is to build a product yourself that sounds fantastic.
Also, I swapped the bass over from a 500Hz xover to a 1,600Hz xover. (Remember I'm using Altec 420A woofer which goes high.)
I'm really enjoying the overall sound.
I think I need a few more resisters to play with for the mid horn, as I jumped from about 47 down to 30...with nothing in between. Plus the resistors are puny 10 watt versions.
Next few days, I'll resand the horns and paint more.
Plus I'll add more dampening into the cavities of two sections, as they appear to echo a little compared to the other sections, when knocked.
All good fun.
When I see Wilson Audio promote their new WAMM product for $600k(?), I really wonder about that and how nice it is to build a product yourself that sounds fantastic.
Attachments
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