| Variac |
This is the Discussion Thread for this paid advertising thread:
http://www.diyaudio.com/forums/show...996#post1234996
It is for for product support, discussion, or feedback and can be posted to by all members. It cannot be edited by the advertising thread renter. |
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| SY |
I got some of the upper bass and midrange drivers for the 3.3s, one of my favorite cone-and-box speakers. My idea is to do a design generally based on the 3.3, but with some appropriate updates. Jack was kind enough to give some suggestions based on their experience, most of which will be incorporated. These include multiamping, steeper acoustic crossover slopes, some rearrangement of the box loading of the upper bass driver, and the substitution of multiple 10" woofers for the 12" Foster 1259. I'll probably separate the bass cabinets from the other three drivers, but I'm still pondering that one.
If anyone else wants to participate in the design, construction, and modification of an updated 3.3 clone (it's not really a clone, it's a clown), I'd be delighted. The NHT version of the H453 seems to be an excellent midrange, and it's silly-cheap. |
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| Variac |
It was SY who dropped in on NHT who are in his hometown, and was talking to Jack Hidley who mentioned he had lots of cool stuff for members at blow-out prices and viola: a great deal for us all.
I have to say , the first thing that I thought of was some kind of standard speaker that lots of us could build. So grabbing some of the drivers SY has might be wise ;) |
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| BWRX |
| I snagged some of the shielded and unshielded 4" seas drivers, dome tweeters, and the 8" woofers. Can't do speaker projects without the drivers! |
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| PB2 |
| quote: | Originally posted by SY
I got some of the upper bass and midrange drivers for the 3.3s, one of my favorite cone-and-box speakers. My idea is to do a design generally based on the 3.3, but with some appropriate updates. Jack was kind enough to give some suggestions based on their experience, most of which will be incorporated. These include multiamping, steeper acoustic crossover slopes, some rearrangement of the box loading of the upper bass driver, and the substitution of multiple 10" woofers for the 12" Foster 1259. I'll probably separate the bass cabinets from the other three drivers, but I'm still pondering that one.
If anyone else wants to participate in the design, construction, and modification of an updated 3.3 clone (it's not really a clone, it's a clown), I'd be delighted. The NHT version of the H453 seems to be an excellent midrange, and it's silly-cheap. |
The NHT-3.3 crossover schematic was published on the web many years ago. I considered cloning it years ago and did some simulations. The upper mid is a custom version of the SEAS MP12 as I recall, Ken Kantor states that different adhesives were specified. It is a true midrange with a short voice coil and therefore throw.
I also considered separate bass cabinets, so that the mains could be simple towers.
Pete B. |
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| SY |
| The part number is slightly different on the midrange and the Xmax limitation (1mm) definitely marks it as a midrange. 300Hz acoustic 4th LR as a high-pass makes sense to me. |
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| bzo |
| wow, I'd like to make my own Sub Two with the VT-3 amp and the drivers. I wonder if using the amp is as simple as hooking up the power, adding RCA connections and feeding it a suitable low frequency signal? Jhidley's comment about posting design guidlines makes me wonder if there is more to it than that? |
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| SY |
| Not much more than that. Some active crossover work (probably about $10 of Radio Shack parts) and you've got a sub with an amazing ratio of performance to cost. |
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| Jack Hidley |
The SubTwo used the same Sunfire power amp as the VT-3. However, both the VT-3 and SubTwo controllers had some excursion and thermal limiters built into them. These would be very difficult to replicate. I don't think the thermal limiting is really needed, but the excursion limiter is needed if you are stupid with the program material and volume knob.
We are considering offering an option to the VT3 amplifiers, of an already installed RCA or XLR connector. This way the amp would be plug and play. If you combine this with an NHT X2 crossover, you can do basically any crossover stuff you want. I'll post some details on the site once we get it worked out. |
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| Jack Hidley |
| We've modified the sale site to reflect that all of the VT3 amplifiers now come with an RCA jack installed. Just turn it on and use it. The price has been adjusted to $90 to reflect this. |
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| badman |
Hi:
I was hoping to get a little more info on the steel framed 10"s: most specifically, what kind of 'high' end response they have: could they be used to 300Hz? Any chance of getting more info on these? |
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| Jack Hidley |
The npt-11-075-2 10" woofers have a standard poly cone with a large rubber surround. The cone/surround combo will work fine up to 300Hz. It doesn't start doing bad things until 700-800Hz.
The voice coil is 50mm diameter and 34mm long. So we are talking about a lot of inductance. The general response shape from 100-800Hz will definitely slope downwards slightly due to this. Also the large inductance and inductance shift will cause more IM type distortion the higher in frequency you use the driver. I wouldn't use it above 300Hz from this standpoint, unless it was for some pro sound application. |
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| bzo |
Jack, thanks for the info and updates on the VT3. I'm definitely going to be ordering a set. The question is whether to build one set or two! :D
Dumb question: the 2 woofers are hooked up in parallel with the VT3 right? |
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| Jack Hidley |
There are no dumb questions, only people to dumb to ask them!
Yes, they are wired in parallel. |
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| phoneisbusy |
| quote: | Originally posted by Jack Hidley
There are no dumb questions, only people to dumb to ask them!
Yes, they are wired in parallel. |
Well, I shall try to prove you wrong then! ;)
I'm thinking of ordering the VT3 woofers and amp. Based on the T/S parameters, I seem to get an F3 at about 30 hz in a sealed enclosure. I think the VT3 went down to about 22 hz so should I assume there is some equalization done at the bottom end by the controller as well as excursion control?
Thank you for your generosity and patience with these questions.
Dave |
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| Jack Hidley |
Dave,
Yes, the controller has a funky shelving circuit to eq the low end down to 22Hz. This part of the circuit design is stupid. It doesn't work well and is very hard to tweak. I would just use a normal shelving circuit (ie Linkwitz transform).
There are a bunch more stages in the controller for the various limiters, crossover filters, video/audio mode eq, etc. I can supply the controller schematic with the VT3 amps.
The VT3 amps also have a +/-18VAC output from the power supply. Just add a small rectifier with filter caps, and you can build your own eq circuit into the physical amplifier.
One of my friends is using eight of the tens in a cabinet with 80l per driver and a port tuning of about 18Hz. With only about 6dB of eq it will be -3dB at 16Hz or so. Luckily his A/V system is against one of the walls to his three car garage. The entire cabinet will be about 6' x 8', but only a foot or so thick. From inside the house, you will only see two 20" x 20" inwall speaker grilles. |
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| valveitude |
Does a schematic come with the 250W@8 ohm amps? Which output devices do they use? Any other info you would like to share about them would be appreciated as well.
Thanx,
Casey |
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| Jack Hidley |
| I added the VT3 amplifier and controller schematics to the sale site. I'll post schematics for the 250W amplifier modules and power supplies tomorrow. |
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| Jack Hidley |
| 250W amplifier and power supply schematics are up. |
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| valveitude |
Hi Jack,
First, I forgot to thank you for offering your "table scraps" to us hacks before tossing them in the bin :). Thanx also for posting the prints so quickly. As soon as my replacement credit card arrives (about a week) I will be ordering some of those 250W modules to play with.
I don't suppose you know the rail voltages? Trying to do a little prelim reverse engineering. I'm assuming something on the order of +/- 80V ?
FYI for others considering this amp:
These amps appear to be pretty long in the tooth, as such, almost all of the semi's are obsolete numbers. The good news however, is that http://www.electronix.com still carries everything except the BF422/423 semis in the protection circuit (the only ones that aren't obsolete), and the output pairs 2SA1302/2SC3281 have a direct replacement in the 2SA1943/2SC5200.
Casey |
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| DAVE CC |
Hi guys,
The NPT-11-075-2 and the VT-3 amp is exactly what I am looking for to build my first twin box sub system, but I have no idea how to build a EQ by using a rectifier in a filter cap, can anyone help me here ?
My inner volume of each of the box is about 1.68 cubic ft, should I make these a sealed or vented system ?
Thanks.
Dave Chang |
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| Jack Hidley |
Mr. Chang
With 1.68 cu ft per driver, you definitely need to keep the enclosure sealed.
You need to build a 2nd order HP filter (12dB/octave) with a corner frequency of 23Hz and a Q of 2.3. This filter can be placed inside the VT3 amplifier or in some other signal processor upstream.
The 075 driver in a 42l enclosure, with the filter from above will give you a -3dB frequency of 23Hz. |
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| DAVE CC |
Hi, Jack
Thank you for your fast responce and info, all sounded great what you sugested, eventhgough i have no idea how to build that filter. I figure some body out there may have something already buit, or will build it for me.
Please also let me know, how can order a pair of the drivers and the VT-3 from you, is it easier for you if i send you a check ?
If you can point me to the direction as how to build this filter,( such as components that I need, and where to get them, or if you can build this filter into the VT-3 and charge me for it.)
I am glad that SY recommented me to this forum and look into your drivers and amps. Thanks SY.
Can't wait to bild these subs...
Dave Chang
PS. If anyone can share any info how to build the filter Jack mentioned, It would be greatly appreciated, maybe I can return the favor by building a custom box in exchange, I work in a high end cabinet mfg, and have unlited free cut-off MDF and other materials.
Thanks guys. |
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| BWRX |
| quote: | Originally posted by DAVE CC
Please also let me know, how can order a pair of the drivers and the VT-3 from you, is it easier for you if i send you a check ? |
Hi Dave. Scroll to the bottom of Jack's sale page: http://home.comcast.net/~jhidley/ for terms and ordering information. |
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| Jack Hidley |
| I updated the quantites of parts available. |
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| al2002 |
| quote: | Originally posted by Jack Hidley
I updated the quantites of parts available. |
Thanks Jack.
What is the 11-080? I don't see it on your home page, only in the XLS file. |
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| Jack Hidley |
| The 080 was used in the VT3, VR3 and VC3 as a midrange. The 081 was used in the VS2.4 and VT2.4 as a woofer/midrange. I'm 99% sure that they are the exact same driver. We probably gave the 080 a different part number, because we QCed it to a tighter standard. I'm trying to confirm the difference now, but this is from two owners ago. |
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| al2002 |
| quote: | Originally posted by Jack Hidley
The 080 was used in the VT3, VR3 and VC3 as a midrange. The 081 was used in the VS2.4 and VT2.4 as a woofer/midrange. I'm 99% sure that they are the exact same driver. We probably gave the 080 a different part number, because we QCed it to a tighter standard. I'm trying to confirm the difference now, but this is from two owners ago. |
Thanks. Please let us know what you find. |
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| Jack Hidley |
| The 081 has a voice coil that is 14.9mm long. The 080 has a voice coil that is 12.7mm long. Except for that, the drivers appear identical. I'll try to post some specs for the 080 driver on Monday. |
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| rspamr |
I received my VT3 amp yesterday. I rewired the RCA jack, hooked up the output wires to the binding posts, and soldered the jumper wire in place. When I turned on the amp, I measured 270mV of DC on the output. I verified with an old speaker and there is in fact enough DC to cause issues. I tried hooking up a source, a source with a low-pass filter, and a short at the input, but I still measured (and saw in the speaker) approximately 270mV of DC. It seems to be amplifying correctly, as I saw higher amplitude AC when playing the source, but the DC offset is still there. I tried disconnecting the jumper and had the same results.
Would adjusting the V+ or V- offset trimmers (as seen on http://home.comcast.net/~jhidley/SubTwoi_Amplifier.pdf) allow me to reduce this offset, or is my amp damaged? |
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| liasom |
| I have two VT3s. Similar results. 274mV on one, 268 mV on the other. |
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| Jack Hidley |
| I'll post a response later tonight. |
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| badman |
Hi all:
I've designed the basics of an unconventional 3 way using the 5.25" peerless and the 10" Foster (the $20 unit). This is going to my not-for-profit day job, for use to be built by the students, and for use with some of their new media gear in the classrooms. We're building a 3 way with these two drivers and a tang band W2-803SM 2" Driver. The idea is for pretty decent power handling through the mid/tweet, so we're using the 2" and crossing over low. Ragged 10k-20k response but we can live with that. Another nice feature of the 2" is the small frame- much smaller than most 1" domes, giving us good driver-driver spacing for better point source behavior.
We're figuring on first order at 1.2k and 2nd order at 300Hz, which should keep the cones all pretty much in pistonic mode up until the 2" breaks up. The only real limitation is the power handling down low- the 10"s would max out with some serious movie bass, but if they're playing loud enough to max out two 10" subs.... something's wrong :)
These will also be used as stage monitors and other types of usage in the school.
A triangular cabinet is being planned, I may post some drawings and other info if people are interested later on. These are made to be used up against walls (or the floor), so there's no baffle step compensation. Sub will be somewhere between max flat and .55 Qtc, sealed. |
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| Jack Hidley |
Whatever you do, don't mess with the V+ and V- adjustments!
The amplifier uses a power supply that tracks the audio output voltage requirements. It's target is to keep about 6V across the output devices at all times. This keeps the output devices in their SOA. Since there is so little voltage drop across the output devices, the amplifier needs less heatsink and is more efficient. If you adjust the V+ and V- controls, you can increase the standoff voltage enough to blow the outputs under the right conditions.
The 280mV or so at the speaker output is there as a bootstrap voltage used to start up the - tracker. It can't be removed or the amplifier won't function correctly.
I ran some measurements with the 10" Foster woofers. With 270mV DC across the woofer coil and the driver mounted axis horizontal in free air, the DC causes a cone displacement of 0.45mm. This is the worst case condition. Place the driver in a sealed box and the displacement will drop down below 0.2mm.
If the amplifier had an output relay, which it doesn't, the DC might be an issue from a turn on/off noise standpoint. You would get a nice audible DC step at the off/on or on/off time. The trackers and the amplifier form a feedback system that takes some time to stabilize during turn on. During this time, the output voltage swings around quite a bit. The small amount of DC present after things have stabilized is completely masked. |
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| bzo |
thanks for the explanation Jack. I think it makes sense that this amount of offset should have minimal impact. After all, using the simple V^2/R formula for power, there is only 15mW of power going into the offset.
I got my MDF cut for my SubTwo clone. Hopefully, I'll have them assembled this weekend!
Jack, you mentioned that the EQ circuit for the SubTwo was not optimal. Do you have a recommendation for the EQ parameters for a homebuilt one that is about the same size as the original (i.e. 1.2 cu ft per speaker)? |
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| Jack Hidley |
I've updated the sale website with information on the npt-11-080-1 driver. It is in fact different than the npt-11-081-1 driver.
The EQ circuit in the Sub 1 and 2 controllers is optimal from a shape standpoint. It is not optimal from a circuit design standpoint. If you want to tweak the shape of the curve at all, it takes a lot of trial and error. I would just use any of the free speaker design programs/spreadsheets out there to determine what eq settings you need. |
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| wyomoose |
Jack,
I currently have a set of SB2's and a SC1 center channel. I like them quite abit, but I want a to built a three way to amtch them as losely as I can for fronts. I also want to build a three center to replace the SC1. Can you make any suggestions from the drivers that are for sale.
Thanks
Todd |
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| Jack Hidley |
Todd,
If you use a pair of npt-11-079-1 6.5" woofers, one npt-11-080-1 5.25" midrange and one npt-11-096-1 tweeter, you will have built virtually a VC3 or VR3 speaker. The 096 isn't the original tweeter, but it is very close. I can even supply an exact crossover schematic. You will only have to modify it for the small tweeter differences.
If you want to build a smaller version, you could just use one of the npt-11-079-1 woofers. This will make the crossover entirely new though. |
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| wyomoose |
Jack,
Thanks for your reply and time. I will probably be placing an order for the 80 and 81 drivers and the tweeter sometime today. I would like to get a copy of the crossover schmatic from you when I place the order. I was going to have a custom builder build the cross over for me because I have never done it before, but if I have the design why not go ahead and try it. Thanks again.
Todd |
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| Ang |
Which driver do you think would be appropriate for a floor to ceiling bass array? I'm crossing over to a rd75 ribbon @ 500Hz active, slope TBA.
I'm concerned about vocal clarity near the crossover point using the 10" foster, even though the modeled freq-resp curve seems like it's still relatively flat at that point. The 8" peerless clone seems like it has a better chance at combining smoothly with the ribbon. The only alternative I see is NPT-11-077-1 pulled from the center channel. If anyone has experience with these let me know how it's gone. Thanks! |
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| Spasticteapot |
| I'd like to know how many drivers are left. I want to stock up! |
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| SY |
I was just over there a few days ago and apparently there's plenty, and even more of the plate amps.
For Burning Amp participants, Jack is bringing some down to the meet along with a Klippel for measurement- anyone who buys drivers gets them measured individually on the spot. Disclaimer: no financial interest here, but my garage lab is now stuffed to the rafters with NHT gear. |
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| Jack Hidley |
I wouldn't use the 10" Foster driver up that high. The distortion from the inductance is going to be fairly high compared to the ribbon drivers.
The 8" Peerless or clone would work pretty well. The 079 will work well, but require more drivers. The 081 will give you the lowest distortion because of the shorting rings, but will require the greatest number of drivers.
I've updated the spreadsheet on the sale site.
We're planning on bringing our Klippel system and an AP to Burning Amp in SF, so we can do linear and nonlinear driver measurements for people. |
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| al2002 |
Can you please update the driver list and quantities available?
Thanks. |
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| Jack Hidley |
| Already done. |
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| Spasticteapot |
| Has anyone here done anything with the VT2.4 or VT3 drivers? |
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| patch |
| quote: | Originally posted by Jack Hidley
Already done. |
I'm wondering if Jack might have more of those woofers in stock?
I have a job waiting for some of them. I'll pay for the move, rent is paid up, the power is on.
patch |
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| liasom |
Jack,
I'm already satisfied with a plan I have to use a 2.1 approach with some Seas drivers (ER18RNX H1456 and 27TDFC H1189) in a two-way loudspeaker and a single NHT 1259/SA-3 amplifier that I already own, but want to explore a three-way version of the system using two separate subwoofer enclosures with active crossovers and 6-channel amplification.
I've read your earlier post #13 in this thread about the high end behavior of the NPT-11-075-2 Foster driver. So, this is about the NPT-11-075-2 vs. NPT-11-083-2 10" Foster drivers. Oh, since the difference is $40 for 4 drivers, price isn't a consideration between the two.
I've modeled both drivers used as two in parallel, 80 liters sealed enclosure, and have also modeled the Linkwitz Transform needed for both and they are very close. Unless I've missed something I don't see any issues that would prevent using either driver.
So, In your opinion which of the two drivers would be best to utilize in the following context?
- My main objective is lowest overall distortion of all types.
- Music only system with moderate playback levels. Quality is FAR more important than quantity.
- Each subwoofer would be two of the Foster 10s in appx. 80 liters sealed.
- LR4 low-pass active filter for the Foster woofers with the crossover point somewhere between 80-90 Hz.
- A Linkwitz Transform (or other slight EQ) to shape the bottom-end response of the Foster woofers.
Thanks, Mike |
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| Jack Hidley |
Mike,
It doesn't really make any difference which driver you use, the 075 or 083. They are nominally the exact same driver except for the frame materials.
Obviously the T/S parameters for the two drivers posted are not identical. That is because the data is pulled from two different samples with no averaging of multiple units. All of the difference between these two samples is because of the difference in Cms. Once you install either driver in a relatively small sealed enclosure, you will find that the frequency responses will be nearly identical. Compare the data from the Klippel analysis's. There it is more obvious how the drivers are the same.
The 083 will have slightly higher power handling due to the cast aluminum frame having lower thermal resistance and more thermal mass than the 075 driver, but the difference won't be much. |
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| Variac |
Jack will be at the Burning Amp show in San Francisco on Oct 21st.
He will have lots and lots of drivers for sale and will demonstrate how to measure drivers to get their parameters.
AND!!! anyone who buys a driver gets the parameters custom measured for that particular piece!!! :eek: Quite a service I think.. |
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| Spasticteapot |
| Will all the drivers be brought to sell at Burning Amp? I'm still trying to organize a group buy for my high school. |
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| Jack Hidley |
| We'll probably bring half of the inventory listed on the website, plus some more top secret stuff (other drivers, used test equipment, etc). But you will have to show up in SF to find out what they are! Remember to max out your ATM cash on Friday and Saturday nights:) |
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| Spasticteapot |
| quote: | Originally posted by Jack Hidley
We'll probably bring half of the inventory listed on the website, plus some more top secret stuff (other drivers, used test equipment, etc). But you will have to show up in SF to find out what they are! Remember to max out your ATM cash on Friday and Saturday nights:) |
I'm on the wrong side of the country. :(
I dare say I'd like some of that stuff, though. Being a student = being broke. |
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| liasom |
| quote: | Originally posted by Jack Hidley
Mike,
It doesn't really make any difference which driver you use, the 075 or 083. They are nominally the exact same driver except for the frame materials... |
Jack, Thanks for the response. Ordering some more stuff today! |
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| Spasticteapot |
| quote: | Originally posted by liasom
Jack, Thanks for the response. Ordering some more stuff today! |
Just don't order all of it! |
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| timbarnes |
Hi Jack:
Just a note to thank you for the speaker cabinets and drivers you were kind enough to give me at the Burning Amp on Sunday.
They will be perfect for my desk / home studio setup once I get them sorted.
Can you please point me to some information about the drivers (they seem to be labelled 8ns 87-11,24 and made in Denmark for the woofer, and 1-11-020 for the tweeter). Neither seem to be in the spreadsheet you published.
You also mentioned that it would be possible to download a crossover design. Could you please point me in the right direction? Any information about the original product would be interesting and useful.
Thanks again,
tim |
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| Jack Hidley |
Tim,
Just PM me your e-mail address and I'll send the schematic. The woofer is a Peerless TP165R. Quite an old model.
The tweeters we gave you are about 1-2dB less sensitive than the tweeter designed for the product. You will just need to adjust the series resistor in the HP section of the crossover and rescale the L and C values. |
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| Spasticteapot |
Can you adjust the totals?
I'm currently buisily selling off my posessions so I can make an appropriately large order. |
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| Jack Hidley |
It will take me a couple of days to accurately adjust the inventory numbers. Here is brief rundown.
077 drivers. All gone.
082 drivers. All gone.
Terminal plate. All gone.
250W amplifier modules and power supplies. All scrapped.
All of the above adjustments are currently reflected in the spreadsheet online. Beyond that:
079 drivers. Running low. Maybe 15 pieces.
All other drivers. Quite a lot left. |
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| Jack Hidley |
I've updated the driver quantities available in the spreadsheet.
We'll be adding two highish efficiency woofers soon. An AR 12" woofer used in the Limited model 3 loudspeaker and a Jensen 15" woofer used in their Cerwin Vega clone line from about eight years ago. Parameters for the AR 12" are already up. Parameters for the Jensen 15" should be up within a week. |
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| patch |
The numbers for the 12-inch from the Limited #3 have me interested.
I am wondering about sizing a sealed chamber for it. That Vas is shown at 269 l ... maybe a Vas that big is normal for the driver's build and purpose and a much smaller box will do. For sure that original cabinet looks a well short of, say, 9 cubic feet, if I have the size converted correctly. Any ideas?
Also, I am wondering if anyone might recall the frequency that this one was crossed in the original LTD. Was this one used like other ARs I remember with rather high and gentle glide points? I have not turned up anything other than pics of those pretty boards.
patch |
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| Jack Hidley |
The brochure for the AR Limited 3 speaker can be found here:
http://www.classicspeakerpages.net/...rs_Brochure.zip
The pictures aren't very good. The bass enclosure goes from the the bottom of the grille up to the break in the front baffle just below the bottom midrange dome. The bass enclosure was probably around 70l (2.3 cu ft)total volume. No where near as large as it could be given the overall size of the speaker.
The woofer was crossed over at 300Hz at 12dB/octave. The combination of a 0.2 Qts, Fs of 20Hz and cabinet volume of 70l all combine to give the woofer an f3 of about 55Hz. A woofer with this low a Qts has no place in an acoustic suspension enclosure. It must be a ported enclosure to get any bass out of it.
In a vented enclosure I would use around 35l tuned to about 37Hz. This will give you an f3 around 45Hz. If you have eq available, you can put it in a 45l enclosure tuned to 32Hz, add a 2nd order HP filter with an Fs of 30Hz and Q of 1.2. That will give you an f3 of about 35Hz.
The easiest way to get more bass extension out of this driver is to add a high power 0.5 to 1.5 ohm resistor. This will raise the Qts quite a bit. Then just calculate the enclosure parameters based upon the new Qts.
This speaker was NOT designed by AR employees. It was designed by people from another company that International Jensen also owned at the time. It is very clear that they had no clue about acoustics or electronics for that matter. |
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| patch |
Jack, thanks for that.
Gads, what a mis-match, sounds like a real waste of potential. I can imagine the owners back then didn't sell all that many at $6,700/pair.
Really helpful information on using this driver. I think everyone marvels when a good designer brings out an exceptional result from raw material - seeing the flash just sitting in there latent (or that could be sitting there) and finding a way to pull it out. Teachers, audio engineers, gardeners, etc.
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| Jack Hidley |
| AR sold seven pairs. They purchased enough raw materials for 500 pairs. |
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| patch |
Wooo. I'd want to distance myself way far away from the project manager on that one. Three floors up.
I wonder why someone picked that particular 12" speaker, its parameters, and the original main application target for the unit. I am guessing, was it something tweaked up from off the shelf, maybe mostly intended for PA, theater, instruments? |
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| Jack Hidley |
| I've just added two more woofers to the sale website. One is an AR 12" cast frame unit. The other is a Jensen/Foster 15" cast frame unit. |
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| badman |
| Wow: that 15" looks spectacular (for $60), very functionally similar to Eminence Magnum 15HO, a much more expensive speaker used in Dick Olsher's "Basszilla" |
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| fishball79 |
Hi,
Would anyone know if the VT3 plate amp's toroid can be rewired for 220v operation? |
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| mordikai |
Mr. Hadley,
any idea what the upper end of the Jensen woofer is? I'm thinking two of these crossed to a horn open baffle. The Qts is a little low for ob but a little EQ might work. Also couldn't I add a resister across the terminals of the woofers and change the Qts?
thanks,
Mordikai |
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| Jack Hidley |
The VT3 amplifiers are 115V only. The transformers are not multi voltage. There is only one primary winding.
I don't know how high the Jensen 15" will go. I'm sure it goes to at least 500Hz. Yes, you can raise the Qts of the driver as high as you like by adding a series resistor with it. Of course, you will lower the sensitivity at the same time. |
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| patch |
A request for information: who might have the crossover pattern(s) for the M3.3 or the 2.9? Or did I miss them somewhere on this forum or the web?
I have been focused on jiggering the 025/070 balance on my test mule - and these two drivers have feathered up a nice baritone/tenor duet in several combinations. But I'm driving in circles in another part of town not finding that right middle of the original.
The 025s and 070s are hugely good deals all around, fine product, doubly the same for the 077s. Thanks to Jack and NHT for making this happen, and to SY and Variac also there in the north bay for letting rest of us know.
Thanks! patch |
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| Spasticteapot |
| I need to get some of these before they're all sold! |
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| patch |
Spasticteapot,
Oh, do it. I'm sure a local pawn shop would be delighted to help out in any way they can. As they might correctly say: pawns produce cash faster than ebay or the driveway :D
No need to cash out your gold, as SY said earlier these drivers are silly-cheap.
Tip: buy by the case - Jack will ship the 070s from the original sealed box (6 speakers). They arrive in perfect condition. And Jack ships quickly.
patch |
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| SY |
| Patch, I'm doing a set of mods on the 3.3s suggested by Jack and will post them here soon. Drop me an email and I'll send you a scan of the stock 3.3 schematic. |
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| Jack Hidley |
| If anyone needs a schematic for the M2.9 or M3.3, just send me an e-mail or PM. |
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| patch |
By chance, has anyone tried using any of the larger drivers for PA work? If so, how did they work for you, how you arrange them?
Thank you SY for the schematic for the M3.3! |
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| Jack Hidley |
| No one has purchased any of the 12" or 15" drivers yet, so I think it's safe to say that no one has used them yet. |
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| CFC |
Are there VT3 amplifiers still available? I'm looking into getting one soon.
Thanks,
CFC |
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| Jack Hidley |
| Yes, all of the products on the sale site are still available. Just look at the spreadsheet to see what the quantities are. |
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| CFC |
Yes, thanks :o
I thought the spreadsheet only had info on the drivers ... I failed to look properly ... sorry.
Expect an email in the coming week.
Thanks,
CFC |
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| h82missafire |
Hello, looking for suggestions for an active or passive variable crossover with gain control for the VT-3 amp that wont break the bank.
Thanks |
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| Jack Hidley |
The NHT X1 and X2 are excellent crossovers. They have a lot of features that you regular run of the mill active crossovers don't have. If you go to the NHT website and download the X2 owners manual, it has a block diagram inside it. Schematics are available for both units.
The X2 is designed to be a general use sub/sat active crossover. It has a wide range of crossover choices and a 2nd order HP filter at 15Hz on the subwoofer output. The X1 is designed to be used with specific NHT subwoofer models. As such it has a narrower range of crossover adjustments and a high Q 2nd order HP on the subwoofer output (about +12dB at 26Hz). You need to change about 12 resistors and caps to modify an X1 into an X2. Instructions are available.
Here is a link to a new X1 I just found on Ebay. Full list on the crossovers is $350. Probably kind of expensive for the DIY market, but at $190, I think it is a great deal.
http://cgi.ebay.com/NHT-X-1-Crossov...1QQcmdZViewItem |
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| pinkmouse |
| Jack, just a quick question. Any idea what the power handling is for the tweeters on your list? |
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| CFC |
| Are there DIY solutions for simple gain control? |
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| Jack Hidley |
Mr Trotsky,
Coming up with a power handling specification for a tweeter is very difficult. It is too much a function of the frequency distribution sent to the driver and the duty cycle of the applied power. It is easy to overdrive the tweeter at 1kHz and damage it mechanically with only 2-3W. The exact crossover frequency and slope therefore has a huge effect on the power rating. Most companies that give specifications for tweeter power handling are not talking about how much power the tweeter can take without damage. They are talking about how much "power" you can send into the input side of the crossover. Once the crossover filters out the low frequencies, there isn't nearly as much power getting to the tweeter.
A well designed tweeter can handle 50W of power for a second or so without damage. If you drive it with 50W for 30 seconds, it will be destroyed. Take a look at a tweeter voice coil sometime. It is usually a 1" diameter coil wound with very small gauge copper wire (0.005" diameter or so). The winding height is usually only about 2-3mm. Even when this is put on an aluminum former, the total mass of copper wire and aluminum former is well below 1gram! Put 50W of thermal energy into this and do the math. The temperature rise is going to be huge. Easily 100+ Degrees F.
The best solution is to use ferrofluid. This allows the heat from the voice coil to flow into the motor structure with much less resistance, so it flows faster and the voice coil heats up much less. When used with typical ceramic magnets, the power handling of a tweeter, at high frequencies (above 4kHz), can be an honest 25W RMS. As soon as you use a neo magnet in the motor, you have about 1/10th the physical mass of magnet and steel in the motor. With a neo motor, the tweeter heats up much faster than with a ceramic motor. The solution we used was to install a heatsink on the tweeter to increase the thermal mass available for the input power. We typically made these out of aluminum bar stock that was 15-20mm in diameter and about 200mm long. One end was tapped with a M4x0.7 hole. A small set screw was put in the end of the bar then this was screwed into the M4x0.7 hole in the back ofthe tweeter. The opposite end of the bar was also tapped for a 1/4"-20 hole. We made a through hole in the back of the cabinet. Then a 1/4"-20 machine screw was run into the hole and into the end of the bar. This bar performed a couple jobs. It was a heatsink for the tweeter and a brace for the cabinet. With the aluminum bar installed, the tweeters have as much power handling as any 1" voice coil tweeter made. Without the bar installed, the tweeters have a lot less power handling than a normal ceramic motored tweeter, but have the same power handling as ANY other 1" voice coil neo tweeter.
The tweeters on the sale page have 1" voice coils, ferrofluid, neo motors, fabric surround and tinsel lead out wires. When used with the heatsink, we have used virtually identical tweeters in speakers such as the VT3, which is a four way tower speaker that can play very loudly.
I hope this answers your question. |
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| pinkmouse |
| Thank you very much Jack. Time to find some ali bar. :) |
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| patch |
I found that this type of heatsink/brace setup is a little harder to make than it appears in the pic, esp. without a nice aluminum bar. Today I'm trying a steel pipe loaded with aluminum washers.
http://www.smr-home-theatre.org/ces...image_010.shtml
By the way, what model is that driver? Looks similar in design to the 077 6.5" that Jack sold out of quickly. |
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| Jack Hidley |
The only way to make a proper heatsink for the driver is with a solid metal bar. Aluminum is good, since it is cheap and has good thermal conductivity. You can purchase it online from www.mcmaster.com. The cut the bar ends square, drill the small counterbore in one end and tap both ends, you really need a lathe. With a lathe, it is very easy to do.
The woofer in the photo is that from an SB1. It has nothing to do with any of the drivers on the sale page. The frame is ABS plastic. |
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| Jack Hidley |
| I just added a second page to the sale site, with some examples of subwoofers that have been built with the drivers on it. Only one subwoofer is up now, but a couple more should be up by the end of the week. |
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| h82missafire |
Jack, would either a SUBONE or SUBTWO controller, including their respective umbilicus cords, work with the VT-3 amp? I can see from your pic of the amp that it has a unique 'S-Video in' type receiver labeled 'FROM VT-3 CONTROLLER'. From a pic of the SUBONE controller I can just make out the same type of connection labeled 'FROM SUB'.
Thanks |
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| Jack Hidley |
Both the VT-3 controller/amp and the Sub1/Sub2 controller/amps used a cable with mini-DIN connectors on the ends. The photos of the VT-3 amplifiers show the amplifiers as they are now. I'm actually removing the preamp card and relacing it with an RCA jack before shipping them. It would be easier for me to not do that at all and just leave the mini-DIN jack there.
I'll have to do some poking around to see if the Sub1 or Sub2 controllers will work with the VT-3 amp. At some level, I'm sure they will. You may have to cut some traces on one end or the other to make this work. You definitely will have to modify the limiting circuits in the controller and the eq to suit your particular subwoofer. |
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| h82missafire |
Thanks for the info Jack.
I will be using two 12" 's with the folowing specs in a 4cu/ft sealed box.
Qts : .375
Qes : 0.49
Qms : 1.506
Fs : 25 Hz
Re : 1.8
Vas : 157 L
MMS : 90g
BL : 7.2 Tm
SPL : 89.1 dB
SD : 510 M^2
Xmax : 9.1 MM
Power max : 250w
Music power : 200w |
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| h82missafire |
Jack, I will be buying one of the VT-3 amps and whether I require one with the preamp card and mini-DIN jack left in place or replaced with an RCA depends on how my negociations for a SUBTWO controller go.
Eagerly awaiting your feedback on whether or not the SUBONE/TWO controllers will work with the VT-3's amp.
Thank you! |
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| Jack Hidley |
It looks like you can use the Sub2 controller with the VT-3 amplifier. I haven't tested the actual combination, I've just looked at the relevant schematics. You will need to modify the eq and limiting circuits in the controller for your particular subwoofer. I would just remove the limiting circuits completely. If you don't get the DIN cable with the Sub2 controller, you will need to buy one from NHT. A generic one won't work.
You do plan on wiring your drivers in series I hope? Do you know what the top plate thickness, voice coil winding height and how many layers of wire are in the voice coils? I assume they are four, but they might be two. |
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| Jack Hidley |
| The second sub project has been added to the sale site. |
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| PB2 |
Is there a cabinet construction diagram or plans for the NHT3.3?
I'd like to know the volume of the lower bass driver enclosure.
Pete B. |
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| Jack Hidley |
| The woofer volume on the M3.3 was about 70l. Cabinet drawings are available if you have a good need for them. |
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| PB2 |
Sorry, I meant the lower mid bass enclosure volume.
I seem to remember talk of how the upper and lower mid drivers had enclosures designed to reduce standing waves. Just wanted to see how that was done. Also to compute the lower mid enclosure volume.
Thanks,
Pete B. |
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