Dipoles sorta like bob/arvo - long

[Dennis H]

Think biiiiiiigger......

From the first page of the thread:
Per side:
2 - Stryke AE IB15's (already bought) low bass dipole, or IB
2 - Seas L26RFX/P (10'' aluminum) ~ 80 ~ 450 Hz
1 - Seas W18EX001 (6 1/2" magnesium) ~ 450 ~ 2000 Hz
1 - Scan Speak 9700 tweeter ~2000Hz and up

[DearS]

Ok. thats a bit bigger than I thought

[Paul H]

Think biiiiiiigger......

From the first page of the thread:
Per side:
2 - Stryke AE IB15's (already bought) low bass dipole, or IB
2 - Seas L26RFX/P (10'' aluminum) ~ 80 ~ 450 Hz
1 - Seas W18EX001 (6 1/2" magnesium) ~ 450 ~ 2000 Hz
1 - Scan Speak 9700 tweeter ~2000Hz and up

Those are the drivers - crossover points for the 10" to 6.5" and for the mid to tweet are a tad lower, based on my listening and Jon's suggestions. I'll almost certainly try a few different crossover frequencies before I settle on the final setup.

Paul

[DearS]

are dipoles not found of small rooms?

are dipoles not found of small rooms?

I have a room 14x16. do you expect a dipole design to work well. or does it need something bigger. by dipole i"m reffering to the Arvo comes to mind.

[ThomasW]

Room placement for dipoles is fundamentally the same as a box speaker. There is a bit more flexiblity with regard to them being closer to the side walls, due to the nulls at the sides of the speakers

[Paul H]

Could a simple preamp (ie Elliot's "Project 88" http://sound.westhost.com/project88.htm ) be built with this crossover in the same box? I could then feed 2-channel direct to the crossover from say a CD player, and wire in a switch/bypass for the feed from the receiver for multi-channel sound.

It seems like a good 'while I'm at it' idea - but are there downsides I don't know about by putting pre-amp and crossover in one case, or are there other preamp circuits you'd recommend?

Thanks,

Paul

[cjd]

Take a look at this simple (but sonically excellent) pre-amp/buffer circuit.

Should be no trouble putting this in the same box and all that good stuff.

C

[Dennis H]

SL says the minimum room size is 12'x16' so you're okay.

http://www.linkwitzlab.com/orion-faq.htm#Q2

Q2 - How critical is the speaker placement?

A2 - Basically, any dipole speaker needs breathing room around it. Even a conventional box speaker benefits greatly from as much open space around it as possible. When measured from the tweeter of the ORION, the side wall should be at least 2 ft (0.6 m) away, and the wall behind the speaker at least 4 ft (1.2 m). The side wall is not as critical as long as there is a sufficient opening for the acoustic volume flow between front and rear sides of the ORION. This then forms an acoustic pressure null towards the side wall. The wall behind the speaker should be somewhat diffusive to disperse sound that is reflected from it. In addition, the sound path from the speaker to the rear wall and reflected back to the listener is at least twice as long as the direct path from speaker to listener, so that the reflected sound level is far more than 6 dB below the direct sound. It is well below the reverberant sound level in the room to which it contributes. Furthermore, the rear reflected sound arrives at least 8 ms later than the direct sound and does not interfere with the perception of the direct sound. The rear radiation should not be absorbed, though. It is an essential contribution to the dipole polar pattern and power response. The rear radiation becomes part of the reverberant sound. With a speaker separation of 8 ft (2.4 m), and a listening distance of 8 ft, and a 4 ft (1.2 m) minimum distance to any wall behind the listener, the minimum room size for the ORION becomes 12 ft x 16 ft (3.6 m x 4.8 m). The ORION will not live up to its full potential in rooms smaller than 180 ft2 (17 m2). Likewise, placing the speaker closer to the wall behind it will sacrifice smoothness of response, though it still provides good sound overall.
As far as the maximum room size is concerned, there is really no limit to it, if the ORION is listened to from typical distances of 8 ft to 20 ft, consistent with speaker separations between 8 ft and 12 ft. The ORION would be misplaced in a ballroom or on a theater stage. The speaker was designed for more close up listening, though at near realistic sound levels.

[Lazz]

Paul, I was wondering if you looked at the AV15's as opposed to the IB15's.Do you know if the AV are better/suited to this project,greater xmax?The AV are listed at $180 and the IB $100 if you buy 4 or more.The IB are great $.Leon.

[Paul H]

Paul, I was wondering if you looked at the AV15's as opposed to the IB15's.Do you know if the AV are better/suited to this project,greater xmax?The AV are listed at $180 and the IB $100 if you buy 4 or more.The IB are great $.Leon.

More xmax is better, but as I recall the AV15 gave 105dB max down to 33-34 Hz and the IB15's were at 38-39 Hz - so the AV15's will play loud lower in a dipole, but not hugely different.

The IB15 has a lower Fs, and a flatter natural frequency response on the lower end.

The IB15's are also available in 8 Ohm versions, which can be paralleled for an efficient dual 4 Ohm setup which isn't hard on amplifiers. This would have fit nicely with an original plan to do an all passive 4-way dipole, c/w monstrous inductors & caps.

From what feedback and reviews I could find, the IB15's were generally well-regarded, and for $100 each the choice was easy. If I were starting over and spending more money I might consider the Soundsplinter 15's, but no regrets here with the IB15's thus far.

Paul

[Paul H]

I'm still playing with Seas W18EX crossovers - I can confirm the numerous documented previous experiences with its beautiful crystal clear sound and %$#@! resonances.

Anyone around here have a topology/schematic/info on a "cauer elliptic analog active lowpass" ? (Not asking for much, am I? )

Thanks,

Paul

[Dennis H]

Do you have LspCAD or something like it? You could take Jon's Modula circuit and optimize it for the W18. The target is LR8 through the shoulder and for the first 50 dB or so. Call it an octave above and below Fc where you want it to match an LR8 response.

[Paul H]

Do you have LspCAD or something like it? You could take Jon's Modula circuit and optimize it for the W18. The target is LR8 through the shoulder and for the first 50 dB or so. Call it an octave above and below Fc where you want it to match an LR8 response.

I have LSPCad, but I'm looking for an analog active filter - Jon's Modula cauer is a passive.

Thanks,

Paul

[Dennis H]

Ah, gotcha. I suspect all it would take is an extra cap in the 4th order active circuit and then optimize the components with LspCAD. Maybe Jon can chime in here with where to put the cap.

[TomK]

I have LSPCad, but I'm looking for an analog active filter - Jon's Modula cauer is a passive.

Thanks,

Paul

Paul,

Take a look at this site for a starting point:

http://ldsg.snippets.org/FILTERS/Cuadra/elliptic.php3

Tom

[JonMarsh]

This is an approach which could be optimized in LspCAD. Jason's using some of the opamps as gyrators (inductor equivalents), instead of using more conventional HP or LP filters.

Keep in mind that his target transfer function is not very optimal... but this network topology approach is usable, if you want opamps and an active filter.

~Jon

[Paul H]

This may be obvious to some, but not me today - where's the connection to the opamp being made? - that schematic shows a single point connection into the opamps, not a + and a -.

Thanks,

Paul

[TomK]

This may be obvious to some, but not me today - where's the connection to the opamp being made? - that schematic shows a single point connection into the opamps, not a + and a -.

Thanks,

Paul

Paul,

The single point connection to the opamp is the non-inverting (+) input. Each opamp is configured as a unity gain follower with the inverting input (-) connected to the output; gain = +1.

Tom

[Paul H]

Thanks Tom. I was guessing that was the idea, but don't like having too many guesses in the circuit when I flip the amps on to test it.

The first potential problem I see with this eliptical is that it breaks the rules of thumb for maximum resistor and minimum cap size. For example I've read a few recommendations to keep resistors below 100kOhm as noise becomes an issue if they're larger.

I set up the above circuit in LSPCad, and adjusted values for a 1600Hz lowpass frequency (adjustments made as noted in Jason Cuadras's website - Thanks to Jason). I immediately got a typical cauer filter around the right frequency, complete with small ripples and bounceback - so far, so good. When tweaking them for my particular use, I ended up with a 3Mohm resistor, and a couple of other close to that.

Can resistors this size be used without creating excessive noise in the circuit?

Thanks,

Paul

[JonMarsh]

The solution is to use "op amps" with higher current drive capabilitiy (ones comfortable with 600 ohm or lower loads, instead of the typical 2 kOhm), larger capacitors as needed (by an order of magnitude or more) and then adjust the resistor component values.

Note that Jason's transfer functios had significant passband ripple and other issues; what you want to do is use LSPCAD's optimizer or manually tweak values to get something that looks like a clean LR8 down to -50 dB for a start.

Even with FET input opamps, 1-2 megaohm resistors will be a big issue for noise...

~Jon

[Paul H]

Thanks Jon - that actually made sense - I'll get my honorary electrical engineering degree yet (The 'bridges' I studied way back when were concrete and steel)

I'm not sure if I'll pursue the cauer approach - adding the notch filter and lowering the 4th order lowpass (1600Hz) have made a significant improvement - and I hate 'noise'.

I'm going to do some more listening/tweaking before trying anything drastic.

Paul

[Lazz]

Lazz

Hello Paul wondering if you got the dipoles playing,and if so can you try and describe the sound.Leon.

[Paul H]

Leon,

I've got one only playing. Two things strike me most about this speaker - the powerful sound and the bass tonality.

The power may come from the all-active approach - I'm not sure. By powerful I don't mean loud but rather able to hit the hard sections, play with 'slam' when required.

The bass is just excellent - yes I'm biased - but I think the dipole approach combined with some overkill on driver size/volume provides the clean and clear bass lines. There's no monotone thump-thumping at all - the bass guitar lines can be clearly followed, etc.

What hasn't been tested yet, because I need two speakers, is stereo imaging. The driver layout may create some interference with imaging, particularly between the mid-range and the two 10" bass drivers. My intent was to keep the spacing tight enough and the crossover low enough that it wasn't a problem - but the proof is in the pudding.

I'm close enough to finished designing/fiddling to build the (semi) permanent crossover and get the second one going.

I'll report back when progress has been made. I've been sidetracked for the last week or so building a proper box for my tempest sub - but that's a different thread.

Paul

[JonMarsh]

Yeah, Paul, IMO there's nothing quite like the tonality and musicality of a well desigined dipole for reproducing the "MUSIC" in the bass registers- bass guitar, standup bass, drums, etc. The best reproduction of the "tonality" of the instruments.

Glad to see you're making progress- all my CPU cycles are being sucked up by the work zone right now... my new boss is essentially starting a month early in beginning of September, and the old one has just left on vacation the rest of this month and September- he really likes his German vacation plan (they start at 5 weeks per year and go up from there- I'm just hitting 5 weeks per year starting next month, but nothing said about when I can take off for it!

~Jon

[Dennis H]

he really likes his German vacation plan (they start at 5 weeks per year and go up from there

Yeah, my friend / business partner Hans in Germany says the whole thing is a big joke. Everybody gets a month or two off and they go work somewhere for cash during their "vacation." Socialism at its finest.

[Jonasz]

Yeah, my friend / business partner Hans in Germany says the whole thing is a big joke. Everybody gets a month or two off and they go work somewhere for cash during their "vacation." Socialism at its finest.

With the lousy pay we get over here we must be compensated in one way or another and vacation is one way.

[TacoD]

With the lousy pay we get over here we must be compensated in one way or another and vacation is one way.

I prefer vacation above money if you cannot spend it, because you haven't the time for it . How come those Volvo/ Saab cars are so expensive and the payment is so bad in Sweden :B.

[Jonasz]

Are they expensive? Here in Sweden they are a lot cheaper than german cars like Audi, Bmw, and Mercedes at least...

I can think of two reasons, first they don't make a millon of them every year like Toyota, Mitsubichi and similar, second it's about price policy. I've read somewhere that cars have very different pricing in different countries. But what do I know? It's only guesses from me... Btw I'm kind of a Saab enthusiast myself. :T

Jonas

[TacoD]

Sorry for OT ...

An Audi A4 1,8 and Saab 93 1,8 (basic model) cost ~36k euro. In Holland the base price of cars is one of the cheapest in Europe, but we have to pay a lot of extra taxes. For english people its cheaper to buy a new car in the Netherlands (they can even order righthand drive) and import into the UK (they can save a couple of thousends euro's.

[capslock]

This is an approach which could be optimized in LspCAD. Jason's using some of the opamps as gyrators (inductor equivalents), instead of using more conventional HP or LP filters.

Keep in mind that his target transfer function is not very optimal... but this network topology approach is usable, if you want opamps and an active filter.

~Jon

Gyrators always make me nervous, but if I am not completely mistaken, the gyrator in the high pass emulates an inductor to ground. Together with C1, it forms a "passive" second order low pass, followed by another "active" second order high pass around the other op amp. I don't know how he winds up with a Cauer response, but this topology hardly seems optimal.

Your passive Cauers usually consist of two cascaded second order filters with a notch filter in between. Wouldn't it be straightforward to use two cascaded active second order filters and put a notch some place in series? Problem is, though, that emulated inductors must have one leg to ground, so one may have to go passive. Actually, with a large value air core inductor, you get the parallel capacitance for free

[Dennis H]

I think C2 is what adds the notch in the highpass. Everything below C2 emulates the R and L part of a passive series RLC leg to ground.

http://www.linkwitzlab.com/filters.htm#7

[Paul H]

Oops

Did two things this morning, neither of them bad by themself.

1) Removed a 10 uF protective cap from the tweeter.

and a little later, while doing a very last check prior to building the permanent crossover ...

2) Dropped a small screwdriver into the crossover wiring board.

#$%^&()_!


Imagine the sound of nails on chalkboard, packed into a high intensity 1/2 second burst. That was the last sound my tweeter would make this morning. It appears 'fully fried' - no sound at all.

My question - is there a chance this $$ (Scanspeak 9700) tweeter is repairable? If so, and I can take it apart, what should I look for?

Thanks,

Paul

[JonMarsh]

D@mn, that's most unfortunate.... you have my sympathies, BTDT.

Because of the way they're constructed, ScanSpeaks are not usually "user" repairable; they don't have a nice clean dome/faceplate replacement thing, it's partly because of how they route the leads to the back in magnet wire form. But Madisound can rebuild SS drivers, and I'd suggest contacting Josh there about that.

For another possible solution more or less gratis, PM me.

~Jon

[Feyz]

How to take apart a Scan Speak dome assembly

My question - is there a chance this $$ (Scanspeak 9700) tweeter is repairable? If so, and I can take it apart, what should I look for?

It is not that difficult to safely take appart a ScanSpeak dome assembly, if you know how they are built. I placed some links to pictures of certain stages of removing the dome assembly of a ScanSpeak 1.5" Dome tweeter, which is same as their 1" 9X00 series in terms of dome assembly AFAIK.

The first thing you need to do is to straighten the solder terminals so that when later in the process pulled up from front, they will slide through their plastic channels easily. Then remove the four screws that holds the faceplate and than remove the faceplate, which is only the aluminum black disc, as seen in this picture: (ignore the black circular gasket that is seen in the upper part of the picture, it doesn't belong to this tweeter):

Image not available

As seen in this below picture, by pushing a thin knife or similar object underneath, make the voice coil lead and terminal strip soldering points come loose. They are slightly glued to the white ring below them with the soldering paste used.

Image not available

Now again using a thin knife like object, and pushing it under each black extensions of the dome assembly that are on sides of the screw holes, make the black dome assembly come loose, and then gently pull it out. The terminal strips will come out of their channels with the dome assembly as you pull gently.

Image not available

At the end, will look like this, the dome assembly is on the right upside down:

Image not available

Note in the above picture, there is a white thin plastic ring that is staying on top of the top plate at the magnet assembly, with solder paste spots on it. That is glued to the top plate, and that provides the centering of the dome assembly. DON'T do anything that will move this white disc out of its glued position. Note in the above picture also, there is a smaller white ring on the back side of the removed dome assembly, this together with the stationary white ring on the top plate provide the centering of the voice coil.

Below is a picture of an opened up SS 9500, as you can its the same assembly method used:

Image not available

BTW I haven't changed any dome assemblies, I just opened them out of curiosity and in the case of the 1.5" tweeter to modify the pole vent damping with lamb wool. So I put back the same dome assembly, and no harm was given, measured before and afterwards with this way of taking it apart and putting back together. I don't know for sure whether they sell the dome assembly alone, and whether it would come with the ring on it that will be provide the exact self centering. I am guessing it should.

[Paul H]

Thanks Feyz. I opened this one up, and the shape/style is similar, but the dome is attached to the main body, and does not come away with the piece with the black tabs - doesn't appear very user fixable, as Jon suggested.

This just highlights something to be aware of with active systems - it's very difficult to blow a tweeter with a proper passive crossover, even if something nasty does come through the amp - not so with active.

Paul

[Feyz]

Thanks Feyz. I opened this one up, and the shape/style is similar, but the dome is attached to the main body, and does not come away with the piece with the black tabs - doesn't appear very user fixable, as Jon suggested.

Interesting, I had taken apart 9500 the same way. It doesn't appear from the pictures, but 9700 is different then.

[Paul H]

Interesting, I had taken apart 9500 the same way. It doesn't appear from the pictures, but 9700 is different then.

Feyz,

You were correct - the 9700 tweeter can be opened up - it was just glued/attached slightly differently than the 9500, with an additional layer of felt in there also. The essential components of the 9700 appear the same as the pictures you posted. I have actually repaired the 9700 with a replacement dome from solen.


Now what to do with some other really nice tweeters I received from someone else..


I have almost finished my dipoles - excepting a tweeter time-delay circuit for one side, for which I ordered more opamps. I'm using my custom point-to-point active crossover which definitely looks like it was built by a woodworking-type guy


Paul

[Paul H]

Finally ... Here's the dipoles, almost finished - which is to say they're fully functional with one tweeter time-delay circuit to tweak, and a minor ground loop to deal with. Also need to attach the front on the xover box once tweaks are done.

They're pictured here along with last year's diy mtm's, which now go to surround duty (overkill maybe ), and their amplifiers sitting in a quick and ugly threaded rod stand.

The sound is impressive - clearer and cleaner than I've ever heard.

If I was going to do this project all over again I'd create something a little less complicated, but it was a phenomenal learning experience and the resulting full-range dipole is (to my admittedly biased ears) fantastic.

Next up, but not right away, a wmtw horizontal dipole centre speaker using the same or similar drivers with a passive crossover.



Thanks to all for your help and assistance.


Paul

[ThomasW]

Hey looking good Paul.... :T

the resulting full-range dipole is (to my admittedly biased ears) fantastic.

That the response from most people upon hearing them...:wink:

[JonMarsh]

Nice looking job, Paul. I bet they're not light even though there isn't any enclosure behing those pretty panels...