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Old 24th December 2004, 08:12 PM   #1
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Default 2-way audiophile-grade box - need matching drivers together

Hi there,


I'm going to build two smaller boxes especially for my SE tube amp (12 Watts Class-A).

I've heard of the importance of sensitivity and I've also heard my friend's ribbon tweeters, so I decided to stick to ribbons in this 2-way project.

After searching a lot for an appropriate tweeter, I chose the Expolinear RT7-Pro finally. They cost EUR419.- / each (do you perhaps know a better price in Europe for them???).

So I've got these two beauties, 100db sensitivity each.

What kind of bass-midrange driver could you recommend ?

I'll stick to these two ribbons, except there're better ones at the same price.

The primary goal is to build two small 2-way boxes with 20-25cm (6-8" or 8-10" ???) bass-midranges and the ribbons on top of them.

The ribbons can be crossed at about 2KHz with 12db/oct. so I'll need a bass-midrange which is capable of going a bit above 3k or so..

.. but which brands should I check out ?

www.orcadesign.com sells lots of drivers from PHL, Focal etc.. but actually, the most sensitive PHL driver's page is unavailable right now.


I think, you got what I want to do: match the bass-mid driver to the ribbons.


Or should I try the Sigma Series from Fostex and have built a TL or horn-type speaker?

Actually, I'm afraid of horns, even from "high-end"-like ones. Once at my friend, I heard two Fostex 208 Sigma drivers in two Jericho horns, driven by Audio Innovations "The First" Amp and Preamp, Audio Note TT LP, Note silver cables etc..

.. well, I wasn't impressed much from that Eric Clapton LP. To be honest, ... (his original AN-J speakers performed amazing in contrast to these horn designs).

The second speaker set was - a week later - those thin boxes oh my.. (it's too late for me now, I cannot think) .. it was a TL box, reference something .. VERY small one fullrange speakers in them .. my friend told them much more expensive than the Note-J boxes, and he also told them to be superior to the AN-J ones.

Well, I didn't think so, again. Those boxes had just too much midrange for my ears, I dunno..

So right now at the moment, I'm really stuck, how to go further. What would YOU do ?

Thanks for any advice.
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Old 25th December 2004, 11:37 AM   #2
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Nobody ?
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Old 25th December 2004, 04:46 PM   #3
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Altough no RT-7, they sell a lot of other ribbon/planar speakers at http://www.partsexpress.com for reasonable prices.
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Old 25th December 2004, 10:41 PM   #4
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What do you say to this one here ?


"DAVIS 20TK8 8" KEVLAR DRIVER ALNICO

This top-of-the-line driver has all of the features to make it one of the most musical 8" drivers on the market. A large AlNiCo magnet with precision machined top and bottom plates provide the power for this motor. A shorting ring on the pole piece reduces distortion, while a precision phase plug reduces compression and improves off-axis response. The very rigid Kevlar cone, extremely compliant rubber surround, and cast aluminum basket provide the ultimate in clarity and detail. This is an awesome driver for no-holds-barred 8" two-way systems.
Specifications: *Power handling: 70 watts RMS/100 watts max *VCdia: 1.5" *Le: .19 mH *Znom: 8 ohms *Re: 6.09 ohms *Frequency range: 50-3,000 Hz *Fs: 77 Hz *SPL: 96 dB 1W/1m *Vas: .69 cu. ft. *Qms: 2.79 *Qes: .53 *Qts: .44 *Xmax: 3 mm *Dimensions: Overall Diameter: 9" by 10-5/16" Cutout Diameter: 7-5/8" Mounting Depth: 4-5/8".
"



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Old 25th December 2004, 11:36 PM   #5
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Quote:
Originally posted by Vortex
What do you say to this one here ?


"DAVIS 20TK8 8" KEVLAR DRIVER ALNICO

This top-of-the-line driver has all of the features to make it one of the most musical 8" drivers on the market. A large AlNiCo magnet with precision machined top and bottom plates provide the power for this motor. A shorting ring on the pole piece reduces distortion, while a precision phase plug reduces compression and improves off-axis response. The very rigid Kevlar cone, extremely compliant rubber surround, and cast aluminum basket provide the ultimate in clarity and detail. This is an awesome driver for no-holds-barred 8" two-way systems.
Specifications: *Power handling: 70 watts RMS/100 watts max *VCdia: 1.5" *Le: .19 mH *Znom: 8 ohms *Re: 6.09 ohms *Frequency range: 50-3,000 Hz *Fs: 77 Hz *SPL: 96 dB 1W/1m *Vas: .69 cu. ft. *Qms: 2.79 *Qes: .53 *Qts: .44 *Xmax: 3 mm *Dimensions: Overall Diameter: 9" by 10-5/16" Cutout Diameter: 7-5/8" Mounting Depth: 4-5/8".
"



Click the image to open in full size.


With a 77hz Fs, it could be difficult to make a satisfactory 2-way with this one.

If you use an active crossover somewhere above Fs to a pair of powered stereo subwoofers in large sealed boxes, or in small ELF aligned boxes- this could be OK.

Also, i am a bit concerned about the response curve- the breakup is high enough, but the parts express sample measurement makes it look like it could use a broad notch filter around 2khz.

I would recommend looking at some professional 8 and 10 inch drivers. I would recommend some Eminence drivers if you were in the US or if shipping doesn't cost too much. Remember, increasing efficiency and decreasing distortion can come from using more drivers.

I hope at least some part of that was helpful.

Joe
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Old 26th December 2004, 01:11 AM   #6
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http://www.jblpro.com/pages/pub/components/2012h.pdf

This driver would be ideal except for 3 things: it's expensive, has a resonant frequency of 61Hz (probably higher than you want), and has a frequency response that rises drastically.
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Old 26th December 2004, 09:11 AM   #7
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Quote:
Remember, increasing efficiency and decreasing distortion can come from using more drivers.
What do you mean ?

May I look for two less-sensitive 4-Ohm/each speakers to put them in series and it would be in theory fine to the 100dB RT7-Pro ?
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Old 26th December 2004, 05:46 PM   #8
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Quote:
Originally posted by Vortex


What do you mean ?

May I look for two less-sensitive 4-Ohm/each speakers to put them in series and it would be in theory fine to the 100dB RT7-Pro ?


As I understand it- yes, by about 3 db for a doubling of cone area. That means (assuming the same amplifier going in) you can get 100 db/w/m efficiency at 8 ohms nominal from two 97 db/w/m 4 ohm speakers in series.

Or, you could wire four 94 db/w/m speakers in series/parallel for a network with the same impedance as one of the individual drivers, but with a 6 db gain to 100 db/w/m efficiency.

The important thing to keep in mind here is that this I'm talking about efficiency, not sensitivity. I guess I was a little absent minded about that, since for your application you really need to worry about sensitivity.

You may already know the difference- but sensitivity refers the sound pressure from a given voltage, and efficiency refers to the sound pressure from a given power. That's why you can see a 4 ohm speaker with a greater sensitivity than the 8 ohm version, but with comparable efficiencies.

I really hope that somebody has a link to a good website that explains all this! Anybody? I'm away from all my bookmarks (traveling on holiday) so I've got to explain this from memory.

Vortex, if you had two 16 ohm drivers in parallel, I think that the sensitivity would increase by 3 db. If you wire four drivers in series-parallel (a group of two in series, wired in parallel with another group of two in series), you should get a 6 db gain in sensitivity and efficiency. If you go to 8 drivers, you're getting into line array territory. That can be rewarding too, but I don't think that's where you originally wanted to go!

One last disclaimer- I mostly talk about sound, not looks. I do have to admit, however, that the Davis driver looks a lot nicer than what I recommended.
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Old 26th December 2004, 09:08 PM   #9
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!!!
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Old 27th December 2004, 05:53 AM   #10
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Quote:
Originally posted by joe carrow




As I understand it- yes, by about 3 db for a doubling of cone area. That means (assuming the same amplifier going in) you can get 100 db/w/m efficiency at 8 ohms nominal from two 97 db/w/m 4 ohm speakers in series.

Or, you could wire four 94 db/w/m speakers in series/parallel for a network with the same impedance as one of the individual drivers, but with a 6 db gain to 100 db/w/m efficiency.

The important thing to keep in mind here is that this I'm talking about efficiency, not sensitivity. I guess I was a little absent minded about that, since for your application you really need to worry about sensitivity.

You may already know the difference- but sensitivity refers the sound pressure from a given voltage, and efficiency refers to the sound pressure from a given power. That's why you can see a 4 ohm speaker with a greater sensitivity than the 8 ohm version, but with comparable efficiencies.

I really hope that somebody has a link to a good website that explains all this! Anybody? I'm away from all my bookmarks (traveling on holiday) so I've got to explain this from memory.

Vortex, if you had two 16 ohm drivers in parallel, I think that the sensitivity would increase by 3 db. If you wire four drivers in series-parallel (a group of two in series, wired in parallel with another group of two in series), you should get a 6 db gain in sensitivity and efficiency. If you go to 8 drivers, you're getting into line array territory. That can be rewarding too, but I don't think that's where you originally wanted to go!

One last disclaimer- I mostly talk about sound, not looks. I do have to admit, however, that the Davis driver looks a lot nicer than what I recommended.
It sounds like you're using sensitivity and efficiency interchangeably. Sensitivity is how much sound pressure you get from 1W at 1 meter of distance from the speaker, and efficiency is the ratio of the power radiated as sound to the power fed to the speaker producing the sound, which is equivalent to n0.
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