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Multi-Way Conventional loudspeakers with crossovers

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Old 4th October 2012, 03:58 PM   #8201
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Quote:
Originally Posted by Lynn Olson View Post
The HF driver is a Radian 745Neo or Altec/GPA 288 with Alnico magnet and standard 288 aluminum diaphragm with 16-ohm voice coil. I have no preference so far; both are very very good, but the Radian might measure just a little flatter, while the Alnico-magnet 288 might have just slightly better tonality. Prices for both drivers are similar.

The horn is an Azurahorn AH425, which is a custom-designed (bespoke) LeCleac'h with a T ratio of 0.707 and matched for a compression driver with an exit angle of 8 degrees. The AH425 diameter is 16.5" and works best in free-air mounting with about 2 inches of separation from the top of the bass cabinet.

The preferred lowpass crossover for the bass unit is 3rd-order Bessel at 700 Hz, with a Zobel compensator for the woofer inductor. I use a nominal value of 12 ohms as the design-center for the 700 Hz lowpass filter.

The preferred highpass crossover for the HF driver is a 700 Hz 4th-order that is transitional between Bessel and Linkwitz-Riley 4th-order. This is based on subjective auditioning with the Radian 745Neo and might be a little different for the Altec/GPA 288. The attenuation is best accomplished with an autoformer or transformer with selectable taps at -15, -14, -13, and -12 dB, and a 16-ohm shunt resistor between the highpass filter and the autoformer/transformer. The design center for the 700 Hz highpass filter is 15 to 16 ohms (the shunt resistor in parallel with the input Z of the transformer sets this value).
DId you scrap the RAAL Lazy Ribbon?
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Old 4th October 2012, 04:03 PM   #8202
Pano is offline Pano  United States
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Quote:
Originally Posted by Lynn Olson View Post
For late arrivals bored by all this phonograph talk; the LTO Apollo (or Athena) has the following architecture:
Thanks for the very clear update and rundown, Lynn. With your permission, I'll link to your current LTO description in the very first post.

I'm surprised that you were able to get where you need to with electrical crossovers at the same point - 700Hz. In my A5 there was such a rising response from the woofer that I had to electrically cross it much lower. I.E., i had to spread the electrical points to get the acoustic points to sum.

It's nice that you did not have to do the frequency spread that I did. Your LTO box size is also surprisingly small, which is a great thing for living rooms.
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Old 4th October 2012, 05:45 PM   #8203
badman is offline badman  United States
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Quote:
Originally Posted by Lynn Olson View Post
As mentioned in my Web page, it take me about six months to design a speaker, and isn't something I do on a whim, or something to "use up" some drivers that are lying around.
Took almost 6 years
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Old 4th October 2012, 09:21 PM   #8204
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yea but it's been so much fun who cares?

My vote goes yes for any form of Decca London style cartridge. That blurb was one of the few advertising spiels I can entirely agree with, but that's just my opinion.
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Old 5th October 2012, 09:09 AM   #8205
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To RockLeeEV:

I'm still going to use the RAAL Lazy Ribbons for my own personal system. For one thing, I own them; Alexander was kind enough to send me the first prototypes he built, and I'm certainly going to use them. They sound absolutely wonderful and are a superb match for the Altec/GPA 288 and Radian 745Neo compression drivers. Although they are pricey, they are in a different league than the standard RAAL - much more dynamic, and do not need in-band equalization. Cross them over with a 3rd or 4th-order highpass, and you're good to go.

I also found out that typical (non-RAAL) ribbons are not such a good dynamic match for compression drivers - you wouldn't think that a ribbon crossed over at 7 to 10 kHz would need much in the way of dynamics, but it's audible as dynamic flattening and a certain lack of tonal vividness right at the top of the spectrum. Integrating a conventional ribbon with a small-format compression driver might work out better, since they don't have the seemingly unlimited dynamics of large-format drivers, but then again, small-formats typically make it out to 15 to 20 kHz without any help from supertweeters.

Heil AMT-type drivers are also a good match, with dynamics similar to compression drivers - you just need to use an AMT with efficiency of 99 dB/meter/watt or higher.

The horn supertweeters were more problematic than I expected. Dynamically, yes, they match the large-format driver, but many of them have a sandpapery coarseness to the sound that spoils the effortless silky smoothness of the 288 or Radian 745Neo. In other words, the small-format metal-diaphragm sound comes back - pinched, tight, and harsh. I haven't tried the hard-to-find EV T350 with the phenolic diaphragm; prices in the collector market are as high as a new RAAL Lazy Ribbon, and I'm always reluctant to recommend unobtanium for any project.

The other downside of many horn supertweeters is surprisingly poor dispersion, with beamwidths that don't seem to be any greater than 20 to 30 degrees in the 10 to 20 kHz top octave. Sure, you can throw crazy money at a horn supertweeter and get a Goto or Ales, but the ones I've heard didn't sound any better than the RAAL Lazy Ribbon, and were way more expensive with limited dispersion.

To Corelement: Sorry, I don't have anything to do with the Jamo speakers. I've seen photos of them, but I've never even heard one, so can't comment one way or the other. Olson is a very common name for people of Scandinavian ancestry, and folks from the frozen North seem attracted to audio - the long dark winters, maybe?

To Badman: I avoided horn speakers for decades because I was afraid of going down the rabbit hole on horn design. I didn't really like the sound of commercial horns, and it took a huge amount of research to reach the point of collaborating with JMLLC, Bjorn Kolbrek and Martin to get the sound I wanted. I'm finally out on the other side of that now - the rest of the speaker is a lot easier to design. The resulting AH425 is a nice little bonus for people who are interested in integrating a medium-size horn into their own speaker designs.

The dipole project was waylaid by the ugly necessity of massive equalization; not a problem for the transistor folks, but the amps I enjoy are direct-heated triode and pentode amplifiers with pretty modest power outputs.

Last edited by Lynn Olson; 5th October 2012 at 09:35 AM.
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Old 5th October 2012, 02:20 PM   #8206
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- but where are the Lazy's compared to say the 288's with regards to sensitivity?
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Old 5th October 2012, 05:00 PM   #8207
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Quote:
Originally Posted by Lynn Olson View Post
Olson is a very common name for people of Scandinavian ancestry, and folks from the frozen North seem attracted to audio - the long dark winters, maybe?
A little explanation of the name Olson

Yes, we are pretty productive here in Scandinavia when it comes to audio.

Especially Denmark is known for some famous brands in audio, e.g.: Gryphon Audio, Vitus Audio, Dali, Bang & Olufsen, Lyngdorf Audio, Steinway Lyngdorf, Dynaudio, Scan-Speak, Duelund, Audio Technology, HÝrning Hybrid

The first practical application of moving-coil loudspeakers was established by Danish engineer Peter L. Jensen and Edwin Pridham, in Napa, California.
I'm proud to be a dane!

We also have a long tradition for DIY here in Denmark, Norway & Sweden. One of the better speaker web-sites on the web might be of your interest: Troels Gravesen.

Lynn, can we have a picture of your prototype speakers? Have you considered using a horn/waveguide in front of the GPA/Altec 416B as in some of the older Altec and JBL speakers?
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Old 6th October 2012, 01:19 AM   #8208
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Lynn ... you mentioned 1" drivers for mids which requires a different AH horn if going that direction or would need an adapter for the 425's. How about manifolding a 425 so you could have the good 2" horn and use two alnico 1" drivers on each horn. Not sure of availability for adapters, eBay? My manifolds are JBL with screw-on 1"; perfect for Atlas alnico's (uncle Paul seemed to do well with them) or flat adapters into manifold can use other drivers (Altec, JBL, etc.).
No clue how they will sound but it's an idea. You would always have tweets for the top end if they suck in higher ranges. I know they would not be a production thing; mainly aimed at us DIYers.
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Old 6th October 2012, 01:46 AM   #8209
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All, let me clarify last post. Edit didn't take (Pano?) Errors from stupidity abounded.
Lynn ... you mentioned 1" drivers for mids. How about manifolding a 2" horn and use two alnico 1" drivers on each horn? Not sure of availability for them, eBay? My manifolds are JBL with screw-in 1"; perfect for Atlas alnico's (uncle Paul seemed to do well with them).
No clue how they will sound but it's an idea. You would always have tweets for the top end if they suck in higher ranges. I will be using two JBL 2420's. I know they would not be a production thing; mainly aimed at us DIYers. I will be using two JBL 2420's.
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Old 6th October 2012, 04:03 AM   #8210
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You can get an adapter to 1.4" at a reasonable price here:
You can get an adapter to 1.4" at a reasonable price here:
Altec Lansing GPA 21216 21216A Horn Adaptor NEW | eBay

I would think manifolding 2 x drivers really only achieves more power, which you don't need.

If you want to depart further from Lynn's spec and raise the cross over point JBL2420s sound great on 550Hz le Cleac'h horns - possibly 550 horns are more suitable for 1" drivers in general. That's my impression. Bear in mind the plot is with the mic at the horn mouth - purely to show horn/driver interaction - not a standard or comparable method. No flames please.

http://azurahorn.com/JBL2420_on_550.pdf

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