The subjective modification thread.

[northwest]

Before someone sticks this in the DIY forum, this is not a DIY thread. I will turn it into one eventually but first I would like to discuss the options available to me THEN start the DIY project.
I am going to rebuild my QUAD ESL 57's. I already have the full and complete kit from Rob in Australia. My plan is to refurb both ov these speakers over the bank holiday/easter weekend and use the office for this. I already have the plate glass and all the other tools.
I also intend to buy/make a couple of clamp circuits to protect the treble panels. Buying seems like a good option to me, they are £37 each from One Thing Audio and I fancy going down that route.

The actual asthetics of the panels has been a subject I have worried like a bone and I actually made the four replacement side rails from a piece of white American Oak AND bought the black acoustic cloth. My intention was to build a couple of pedestals as Sheldon did here:
http://www.quadesl.com/graphics/quadGraphics/current_quad.jpg

I hadn't seen anything else and I was starting to suffer tunnel vision, unable to think outside the box, then I saw these on Quadesl.nl:
http://quadesl.nl/img/revisie/quad-esl-gereviseerd-1.jpg

So I have retired the new side pieces and I have drawn up new "spider" leg template so I am going to remake them again in white oak. So of course the black acoustic cloth no longer suits but I have found some terrific cloth here: http://www.autoacoustics.com/speakergrillecloth.htm and I have decided taupe will be the colour of the day. I am going to fume the oak side rails/legs and the black I will spray using two pack.

Now for the contentious bit. I am going to try so called 'Super Tweeters' as a few people have on here and furthermore, I am going to position the tweeters underneath the bottom rail of the framework, so at the bottom, underneath the speaker, where the third centre leg, is.

What should I use for these speakers? Shall I use horns? I am of course going to use L Pads but what shall I use as values for the resistors?

And finally - WILL IT SOUND BETTER? Will the "super tweeters" be worthwhile? The only other thing is, cost. I would like to keep my material costs down to around the £100 mark.

Over to youse.......

[Reid Malenfant]

You are better off having any tweeter & indeed supertweeter at ear level in all honesty. Is there any way you could extend the middle rear leg up so you could attach the supertweeter so it's facing out just above the ESL panel?

I wouldn't use a horn as the sensitivity will be too high & they'll generally run out of steam (output) below 18KHz, I'd be more inclined to use some kind of ribbon or other direct radiator.

The ESLs have low impedance in the upper frequencies, any direct radiator will be pretty high in impedance at those kind of frequencies so shouldn't be as problematic as the panel in all honesty :)

[northwest]

You are better off having any tweeter & indeed supertweeter at ear level in all honesty. Is there any way you could extend the middle rear leg up so you could attach the supertweeter so it's facing out just above the ESL panel?


I just knew some bugger vwould be along to shoot the ankle high tweeter idea in the foot as it were <sigh> Might as well be you Mark.
Okay, I know I can put them on up top so i'll give it a bit of thought. Maybe extend one of the side rails up and have the tweeters up on the top inner corner of each speaker. It's an idea.

[Reid Malenfant]

Sorry Graham :eyebrows: I'd try & get the supertweeters in the middle & just above the panel. I'm no expert on the ESL but I thought the tweeter panel was in the centre so that is where I'd stuff the supertweeter.

It's a question of these things at these frequencies have far more of "I can pick out the direction it's coming from" than bass frequencies. Keeping it at ear level won't all of a sudden get you hearing things down near the floor or to the left or right of the tweeter panel...

Hope that makes some sense :)

[aquapiranha]

http://quadesl.nl/img/revisie/quad-esl-gereviseerd-1.jpg


That is gorgeous! So much better looking than the original, but still a bit retro.. :eek:

[Jonboy]

Townshend (http://www.townshendaudio.com/supertweeters) make a nice little bracket to match thier super tweeters

[northwest]

Townshend (http://www.townshendaudio.com/supertweeters) make a nice little bracket to match thier super tweeters

Yes Jon, very funny. Maybe you were confused - only TWO zero's on my 'price range indication' :lol:


That is gorgeous! So much better looking than the original, but still a bit retro..

I thought so too. Pity I found the pic after I made the new side rails:doh:

Other than the Townshend we are a bit short on suggestions here. Anyone (Mark?) care to step in and suggest a few different super tweeters I might look at as possiblies?

[sq225917]

What about the ones from audiosmile?

[The Grand Wazoo]

Graham,
I think Jon was alerting you to the bracket rather than the tweeters

QUAD BRACKET
Townshend Audio has introduced a bracket which allows the maximum super tweeter to be mounted onto the Quad ESL57 loudspeakers.

Cheers

[The Grand Wazoo]

There's always the Decca ribbon, which with the Quad formed 2/3rds of the HQD system - you'd need massive Hartley woofers to do the full thing.

Murata did make one - the ES105 spherical ceramic super tweeter (http://www.murata.com/speaker/es105.html), which was a neat looking zinc alloy thing.
Before that, they did an ES103.

http://www.notenki.jp/seven/wp-content/uploads/2009/03/es105.jpg


If you're on a real budget, you could try messing with some cheapy piezo tweeters from Maplin.

[The Grand Wazoo]

Big thread about super tweeters here (http://theartofsound.net/forum/showthread.php?t=5498)
....and I expect Andre will be along in a bit to tell you about the Coles.

[Reid Malenfant]

Big thread about super tweeters here (http://theartofsound.net/forum/showthread.php?t=5498)
....and I expect Andre will be along in a bit to tell you about the Coles.
Actually the Coles 4001 isn't a bad idea at all :) As far as I'm aware the diaphram material is the same as the ESL - Mylar...

While they wouldn't be too expensive, they are also available in different impedances which could be handy. They are probably about the same voltage sensitivity as the ESL as well & I think the faceplate would pretty well match the colour of the ESL grilles...

[northwest]

There's always the Decca ribbon, which with the Quad formed 2/3rds of the HQD system - you'd need massive Hartley woofers to do the full thing.

Murata did make one - the ES105 spherical ceramic super tweeter (http://www.murata.com/speaker/es105.html), which was a neat looking zinc alloy thing.
Before that, they did an ES103.

http://www.notenki.jp/seven/wp-content/uploads/2009/03/es105.jpg


If you're on a real budget, you could try messing with some cheapy piezo tweeters from Maplin.

Yes, been offered the Decca ones for a very reasonable £500 :stalks:
It isn't so much as a budget I am on as I am just not going to be selling a lung for it. The modifications/rebuild to the original Quads are between £750 and 2200 Euro's depending on who you talk to. I am going for the 2200 plus renovation and then some but doing it myself. I have already spent around £600 on bits alone.
I really don't want to spend an equivalent amount to voyage into - what is for me - uncharted territory. If they produce the beans who knows where I will take it? For me this is a proof of concept project.

I would really like the Deccas. I am not spending £500 on them.

[Jonboy]

Graham,
I think Jon was alerting you to the bracket rather than the tweeters

QUAD BRACKET
Townshend Audio has introduced a bracket which allows the maximum super tweeter to be mounted onto the Quad ESL57 loudspeakers.

Cheers


Yes the bracket was what i thought you might get some ideas from, i had forgot about the coles ones which could work, or do as i did and use the maplins ones to give you a taste. A tweater at ear level would be best as i don't think you would beneifit otherwise, if you think of the stats as firing their sound out in an Arc you are trying to point the tip arc at your ears if that makes sense, i hope i'm not trying to tell you how to suck eggs

[The Grand Wazoo]

...... or do as i did and use the maplins ones to give you a taste.....

That would be my way of going about things (in fact that's exactly what I did do!)

[northwest]

I like the idea of the Coles. I have found some HERE (http://www.falconacoustics.co.uk/coles-4001k-8-ohm-super-tweeter.html) and to be honest they are not a lot of money. I will make up a sort of "domed mantle clock type" bracket for the centre of the ESL's and it will be straightforward fitting it to the frame. Now the big question - open baqck or closed back? Closed back isn't that difficult either as these things are not very deep though I will take advice on whether or not it needs some sort of enclosure of a specific volume/design.
I looked at the Maplin offerings and though cheap enough I figure I would get my money back if the Coles didn't work out for me (well obviously not ALL of my money!).
Now the L Pads, any suggestions for a starting point anyone?

[Reid Malenfant]

No enclosure needed as they are sealed at the back :)

Before you go buying stuff let me do some research on the reference efficiencies of the different models of the 4001 (& your ESLs). I wouldn't like to recommend anything that would be incompatable :rolleyes:

[Barry]

It's a general rule of thumb that if you extend the response of a speaker system in one direction, you also need to extend the response in the opposite direction for it to sound 'balanced'.

The product of the lower (-3dB) frequency and the upper (also -3dB) frequency (both expressed in Hz) should be 400,000. Thus ideally 20Hz to 20kHz, but a speaker system whose frequency range is 50Hz to 8kHz, will sound equally balanced. Whereas one whose frequency range is say 40Hz to 30kHz will sound 'lop-sided' and wrong.

The un-enhanced Quad 57 has an effective range 40 - 10,000Hz. Increasing the upper limit to 35kHz will mean you ought to add a sub-woofer that has a -3dB point at 11.5Hz.

[Reid Malenfant]

The un-enhanced Quad 57 has an effective range 40 - 10,000Hz. Increasing the upper limit to 35kHz will mean you ought to add a sub-woofer that has a -3dB point at 11.5Hz.
That can be built :) Room gain below the lowest room mode is somewhere around 4 - 6Db per octave, so a gradually rolling off response from the speaker would result in a pretty flat response to silly frequencies. You just need to stop thinking about Anechoic conditions as none of us has them :eyebrows:

[Barry]

That can be built :) Room gain below the lowest room mode is somewhere around 4 - 6dB per octave, so a gradually rolling off response from the speaker would result in a pretty flat response to silly frequencies. You just need to stop thinking about Anechoic conditions as none of us has them :eyebrows:

Yes, but how much power do you need to actually create an 11Hz tone that can be heard (or rather felt)? The room is not infinitely rigid.

[northwest]

Yes, but how much power do you need to actually create an 11Hz tone that can be heard (or rather felt)? The room is not infinitely rigid.

Actually, and without wanting to sound like a smartass, the walls are solid two foot thick, so it isnt going to move that far!

[Barry]

Actually, and without wanting to sound like a smartass, the walls are solid two foot thick, so it isnt going to move that far!

Agreed, but you will still need several hundred watts. The ceiling is not two foot thick, or is it?

[Reid Malenfant]

Yes, but how much power do you need to actually create an 11Hz tone that can be heard (or rather felt)? The room is not infinitely rigid.
Surprisingly not a lot :)

I have had a single 8" woofer reproducing 20 - 25Hz at a quite loud level. Much louder than you need to actually hear the fundamental. If you look at equal loudness curves for different frequencies you'll see that is moving some air.

Like I say, forget about anechoic as you are reproducing stuff in what will be a big closed box (the room) & this will increase the gain at low frequencies. The thing is most people don't design their speakers to go this low :eyebrows: When you do, you'll soon realise that a good deal less power is needed to get a flat response.

Yes, you still need to move some air though... This is why I'm building new speakers to take advantage of this phenomenon.

[Welder]

Call me weird if you like, but i would be happy if we could get 20Hz to 20kHz right, never mind all those frequencies that don't get recorded. ;)

[Reid Malenfant]

Agreed, but you will still need several hundred watts.
Why are Watts a problem? I have over 4KW to do the job of producing over 116Db at 10HZ...

Yes I think you read that correctly, add room gain as the calculation is for a 2Pi situation & you have over 120DB

While you might think I'm nuts I'll be able to listen to anything at any volume level I can withstand & know that the speakers are hardly adding to the level of distortion at all ;)

At any normal listening level I'll be listening to about 20Db less distortion than just about anyone else as well as going down to about 7.5Hz :)

I understand I might have slightly different ideas about how to do things. However, if the speaker can't do it it never will...

[StanleyB]

I have spent a lot of time in a shebeen or two, enjoying music below 20Hz. OK, it might not be clear to many what I am on about, but those who have been there and done it as well know what I am on about :eyebrows:.

[nat8808]

Call me weird if you like, but i would be happy if we could get 20Hz to 20kHz right, never mind all those frequencies that don't get recorded. ;)

I used to think that but I'd say it is possible to go pretty high with a minimalist recording. Mics can do it even if not spec'd that high, a lot will depend though on the processes after and equipment after.

Everyday and also quite expensive mics are spec'd usually from 30Hz - 18KHz but often do go past 30KHz even if at that point they're 20dB down.

Get someone using Mega-expensive Bruel and Kjaer test mics as recording equipment (I'm sure I've seen specialist, lone recording engineers do this) and frequency responses are then limited to the capsule pre-amps which are often flatish to 40KHz..

Still, it's most recording engineer's assertion that humans only hear 20-20Khz so the majority only make decisions that effect that range (if that!). Anything above will probably be a mess and not taken into account at any stage (not least of all because you can't directly hear it! How can you mix, master anything that only gives a 'sense' of something).

Still, I'm yet to hear a supertweeter in use. I would like to think there's still more to experience.

[nat8808]

It's a general rule of thumb that if you extend the response of a speaker system in one direction, you also need to extend the response in the opposite direction for it to sound 'balanced'.

The product of the lower (-3dB) frequency and the upper (also -3dB) frequency (both expressed in Hz) should be 400,000. Thus ideally 20Hz to 20kHz, but a speaker system whose frequency range is 50Hz to 8kHz, will sound equally balanced. Whereas one whose frequency range is say 40Hz to 30kHz will sound 'lop-sided' and wrong.

The un-enhanced Quad 57 has an effective range 40 - 10,000Hz. Increasing the upper limit to 35kHz will mean you ought to add a sub-woofer that has a -3dB point at 11.5Hz.

Is that really the effective range of the 57? Or do you mean a -3dB range but maybe a slow roll off?

[nat8808]

What's the Cole's frequency response like at the higher end?

Many modern ~ £30 tweeters are able to reach into the 40Khz region as standard too and with quite a flat response.

Have you browsed through Falcon Acoustic's range for example? Some of the SB Acoustics tweeters go past 40KHz on axis for about £30 odd.

[Welder]

I used to think that but I'd say it is possible to go pretty high with a minimalist recording. Mics can do it even if not spec'd that high, a lot will depend though on the processes after and equipment after.

Everyday and also quite expensive mics are spec'd usually from 30Hz - 18KHz but often do go past 30KHz even if at that point they're 20dB down.

Get someone using Mega-expensive Bruel and Kjaer test mics as recording equipment (I'm sure I've seen specialist, lone recording engineers do this) and frequency responses are then limited to the capsule pre-amps which are often flatish to 40KHz..

Still, it's most recording engineer's assertion that humans only hear 20-20Khz so the majority only make decisions that effect that range (if that!). Anything above will probably be a mess and not taken into account at any stage (not least of all because you can't directly hear it! How can you mix, master anything that only gives a 'sense' of something).

Still, I'm yet to hear a supertweeter in use. I would like to think there's still more to experience.

It's not that it cant be done; it just isn't by and large.
To the best of my knowledge most recording studios just don't bother with much above 16kHz/18kHz and not much below 20 Hz.
This doesn't mean there are no recordings with frequencies above and below this, it's just not common and obviously, if not audible to the engineer, not mixed.

[Jonboy]

L pads here (http://www.wilmslow-audio.co.uk/index.asp?function=SEARCH)

[Barry]

Why are Watts a problem? I have over 4KW to do the job of producing over 116dB at 10Hz...

Yes I think you read that correctly, add room gain as the calculation is for a 2Pi situation & you have over 120dB

While you might think I'm nuts I'll be able to listen to anything at any volume level I can withstand & know that the speakers are hardly adding to the level of distortion at all ;)

At any normal listening level I'll be listening to about 20dB less distortion than just about anyone else as well as going down to about 7.5Hz :)

I understand I might have slightly different ideas about how to do things. However, if the speaker can't do it it never will...


Agreed the acoustic loading is not free field (or anechoic). The situation is one of the speaker driver-cone acting as a piston in a sealed volume. The operative word here is sealed; no air must escape the listening enclosure, nor must energy be lost during each half cycle through absorption by the walls of the enclosure. Hence my comment on thick, or high density surfaces – all six sides of the enclosure; which obviously includes the ceiling.

Lets do some sums. We will consider the generation of a continuous steady tone of 20Hz.

According to the equal loudness contours for the human ear, the threshold of hearing at 20Hz is +70dB relative to a sound pressure level of 0.0002 dyne/cm². (I apologise for not using SI, but I was educated in the old system. Although I can use both, I often tend to use the older system when it comes to mechanical systems involving pressure.) So to perceive a 20Hz tone readily we should maybe increase this to +100dB, that is a sound pressure level of 20 dyne/cm².

Now for a piston operating in a sealed enclosure of volume V and pressure Po, the pressure P, due to a change in relative volume ΔV is given by


P = γ Po (ΔV/V)

With the nominal pressure for air at 20ºC Po = 1.0133 10^6 dyne /cm², and γ = 1.4.

Thus ΔV/V = 14.1 10^-6 (or 0.014%).

Let us now assume the listening room has an overall volume V = 31m³ (that is a room: 14 foot long x 10 foot wide x 8 foot high), then ΔV = 4.23 10^-4 m³.
Let the speaker have a 12” driver. The effective cone area will be ~ 500 cm², so a change in volume of 4.23 10^-4 m³, implies a cone excursion Δx of 8.5mm.

The motion of the cone, for a continuous steady tone, is simple harmonic so the cone acceleration is


d²s/dt² = - ω²s (where ω = 2πν, and ν = 20 Hz)

then the average force exerted by the cone will be


F = m ω² (Δx/√2).

The energy expended by the moving cone for each half cycle will be E = FΔx = (ωΔx)²(m/√2), so the power dissipated each half cycle will be E/t where t = 25ms (for 20Hz).

Assuming the cone mass for the 12” driver is 20g, then the mechanical power dissipated by the speaker in producing the 20Hz tone into an enclosure of 31m³ is 1.23W.

Being generous, the electro-acoustic efficiency of the speaker at this frequency is likely to be < 1%, implying an electrical power requirement of > 123W (and 1.23kW if the efficiency is only 0.1%).

It’s not that such SPLs at these low frequencies can’t be generated, they can but it does require power.

[nat8808]

Lets do some sums. We will consider the generation of a continuous steady tone of 20Hz.



Err, I'll just watch you do them thanks! :)

[Reid Malenfant]

Agreed the acoustic loading is not free field (or anechoic). The situation is one of the speaker driver-cone acting as a piston in a sealed volume. The operative word here is sealed; no air must escape the listening enclosure, nor must energy be lost during each half cycle through absorption by the walls of the enclosure. Hence my comment on thick, or high density surfaces – all six sides of the enclosure; which obviously includes the ceiling.

Lets do some sums. We will consider the generation of a continuous steady tone of 20Hz.

According to the equal loudness contours for the human ear, the threshold of hearing at 20Hz is +70dB relative to a sound pressure level of 0.0002 dyne/cm². (I apologise for not using SI, but I was educated in the old system. Although I can use both, I often tend to use the older system when it comes to mechanical systems involving pressure.) So to perceive a 20Hz tone readily we should maybe increase this to +100dB, that is a sound pressure level of 20 dyne/cm².

Now for a piston operating in a sealed enclosure of volume V and pressure Po, the pressure P, due to a change in relative volume ΔV is given by


P = γ Po (ΔV/V)

With the nominal pressure for air at 20ºC Po = 1.0133 10^6 dyne /cm², and γ = 1.4.

Thus ΔV/V = 14.1 10^-6 (or 0.014%).

Let us now assume the listening room has an overall volume V = 31m³ (that is a room: 14 foot long x 10 foot wide x 8 foot high), then ΔV = 4.23 10^-4 m³.
Let the speaker have a 12” driver. The effective cone area will be ~ 500 cm², so a change in volume of 4.23 10^-4 m³, implies a cone excursion Δx of 8.5mm.

The motion of the cone, for a continuous steady tone, is simple harmonic so the cone acceleration is


d²s/dt² = - ω²s (where ω = 2πν, and ν = 20 Hz)

then the average force exerted by the cone will be


F = m ω² (Δx/√2).

The energy expended by the moving cone for each half cycle will be E = FΔx = (ωΔx)²(m/√2), so the power dissipated each half cycle will be E/t where t = 25ms (for 20Hz).

Assuming the cone mass for the 12” driver is 20g, then the mechanical power dissipated by the speaker in producing the 20Hz tone into an enclosure of 31m³ is 1.23W.

Being generous, the electro-acoustic efficiency of the speaker at this frequency is likely to be < 1%, implying an electrical power requirement of > 123W (and 1.23kW if the efficiency is only 0.1%).

It’s not that such SPLs at these low frequencies can’t be generated, they can but it does require power.
Wow Barry, I just use winISD & let that show me what I can come up with.

You certainly appear to know your stuff & i'm in no position to even attempt to argue with you (not that I'd dream of it anyway :eyebrows:).

As for the highlighted bit, that is not a problem, as I say I have 2.3KW RMS per channel (8 ohms) at my disposal. I also have 4 x 4 ohm 1KW RMS rated 15" drivers with 30mm linear excursion each way (60mm pk-pk linear), which makes me think that won't exactly hinder things either :cool:

[visionary]

Wow Barry, I just use winISD & let that show me what I can come up with.

You certainly appear to know your stuff & i'm in no position to even attempt to argue with you (not that I'd dream of it anyway :eyebrows:).

As for the highlighted bit, that is not a problem, as I say I have 2.3KW RMS per channel (8 ohms) at my disposal. I also have 4 x 4 ohm 1KW RMS rated 15" drivers with 30mm linear excursion each way (60mm pk-pk linear), which makes me think that won't exactly hinder things either :cool:
I'm glad I don't live in the other half of a semi-detached with you :lol:

[Reid Malenfant]

I'm glad I don't live in the other half of a semi-detached with you :lol:
:rfl: Yes you can imagine I'm very happy living in a detached house, as I'm sure my nearest neighbour is :eyebrows: