| BobEllis |
Looking for interest in another active filter board group buy.
Each board is a single channel. Two required for stereo 2 way, 4 for stereo 3 way, 6 for stereo 3 way.
Features:
High/Low/bandpass to 4th order.
Sallen Key equal component value topology (jumper for unity gain topology)
Balanced/Single ended input buffer with bandwidth limiting lowpass (optional) can also be configured as shelving low pass filter (baffle step compensation).
Variable attenuation for both high and low pass output buffers.
Independent of the high and low pass filters, the following can be patched into either band:
Linkwitz transform (biquad)
2 notch/peaking EQ sections
first order all pass
The board does not include a +/- 15V power supply. Power supply boards and parts are also available as part of the group buy (if there is enough interest)
Active XO Board Goup Buy WIKI |
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| m0tion |
| quote: | | Two required for stereo 2 way, 4 for stereo 3 way, 6 for stereo 3 way. |
Sorry, could you clarify this? I believe this was a typo. |
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| Davey |
6 for stereo 4 way.
Davey. |
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| BobEllis |
Sorry about the typo.
Each board is a single channel configurable as either high + low pass or bandpass. We chose to keep the boards single channel to allow the other features and still keep within the free version of Eagle's size limits.
Schematic: http://www.delta-audio.com/temp_jen...dio.com.sch.pdf
A single board does a single channel two way, use two for a stereo two way.
For a three way you need two boards per channel - either 1 for High and Low, the other for Mid (bandpass) or one for mids up/lows and the other mids/tweeters.
Similar concept for a four way, three boards per channel. |
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| F1 FAN |
Hi Bob ,
I would be interested in 4 boards but not sure how to add my name on the list.
Thanx Fred |
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| BobEllis |
| Got you covered Fred. Need any power supply boards? |
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| Killjoy99 |
| Added myself for 8 boards |
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| F1 FAN |
Hi Bob, sign me up for 1 PS board also.
I was going to use nasty LM 7815,7915's then I took a look at your Reg's.They should be a big improvment.
Thanks again Fred |
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| BobEllis |
No problem Fred.
All you need to do if you have any changes is click the "click here to edit this page" link at the bottom of the page. You may need to sign in again, but it's really pretty easy. There's a "sandbox" page on the Wiki that allows you to practice without risk of harm. |
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| F1 FAN |
I just read through most of the threads on the filter and PSU boards and must say a big thanks goes out to Bob and Jens for the time and effort that went into these excellent circuit and PCB designs.Your efforts put Hi performance active crossovers in our hands for ridiculously little money.
Great work Gentlemen.
Fred |
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| m0tion |
This might seem like a ridiculous question at this point, but is there a parts list? I'm assuming that because values have to be calculated parts aren't included, but is there a list with Digi-key part #'s and approximate prices?
Basically my question is, if I buy 4 boards, 1 PS kit, what else do i need before i have a functioning crossover (other than enclosure, in/out connectors)? |
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| BobEllis |
A PSU kit will power four boards with no extra parts.
The parts that go with all filter boards are:
2 ea ~220-470nf caps 10 mm dia x 5 mm lead spacing
100 nf decoupling caps (2 per op amp) 2.5 x 7.5 mm, 5 mm lead spacing
Op amps 4-9 depending on features used. 5532s will work, or try your favorite dual op amp. I don't know if anyone has tried LM6172 or other very fast chip on this board. It shouldn't be a problem, but without testing you never know.
Op amp sockets good idea, but not absolutely required.
Trim Pots 1 or 2, top adjust Bourns 3296Y or equivalent.
10K resistors you buy these 1000 at a time, right? ;)
Pin Headers 0.1"/5mm spacing, snappable (optional) for input/output and patching sections together. You may want some jumpers to switch between 2nd and 4th order, etc. Molex (or other) contacts can be used by themselves or with a connector body to make I/O connections.
mounting hardware don't forget to pick up a bunch of extra standoffs and 4-40 x 1/4 (for US builders) screws.
For the filter sections, most target frequencies can be reached using 10-100 nf caps. (5x 7.5 mm, 5 mm lead spacing) You could use 5-10% caps if you buy extras and pick out ones that are within 1-2%.
There is a manual and excel spreadsheet available on my website (button below) as well as Jens' site and in the thread (WIKI links)
It looks like there is enough interest to support a group buy. I'll offer 100 nf and 470 uf caps like last time.
I will be taking a break from technology from 21-30 July - There's no Internet access where I am going (I can't bear dial up). I'll be back to answer questions on 31 July. |
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| BobEllis |
| When adding your request to the WIKI, please update the totals. Not a big deal, it just makes it easier for me. Thanks. |
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| Killjoy99 |
Added 4 PSU boards to my order...
-Brian |
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| kevinkr |
| Added me for 4 boards and two power supply kits.. |
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| BobEllis |
I'm back. Didn't touch a computer for a week and it was great!
Anyone have any questions about the boards?
The buy is a go - I'll post payment details and deadlines shortly. |
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| F1 FAN |
Hi Bob welcome back. Hope you had an enjoyable holiday.
Great to hear that the buy is a go. :)
I do have a couple of questions if I may.
I searched the manual but was unable to find info to design the notch filters and determine component values for Baffle step compensation.I am hoping there is some sort of spreadsheet for these.
Also in your sample (pg.21) using the Focal drivers the Baffle step comp indicates R12 and R16 should be 4.95K but the value of C10 is not mentioned.
This will be about the right amount of BSC needed for my project.
Thanks Bob for your help.
Fred
BTW did you fly F14'S for the US Marines?
Taking off and landing one of those babies on an Aircraft carrier has got to be the craziest but most exciting job period.:D |
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| BobEllis |
There is a page in the spreadsheet for caclulating both notch filters and shelving filters. You'll pick some values and the sheet will calculate the rest. See my website to download it if you haven't already.
I used 100 nf for my BSC, but you could use any convenient value. I'll have to update the manual to show that.
I was a Tomcat RIO (Radar Intercept Officer) in the US Navy - the backseater with no flight controls. Some guys I flew with made landing fairly benign, others made it (landing and the language following) quite colorful ;) |
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| F1 FAN |
Thanks for the quick reply.
Sorry about that Marine remark hope I didnt offend you.:eek:
I can imagine their is substantial skill level differences even between these Elite pilots. Some you would probably rather not fly with.
I can just bet you had some hair raising incidents with some of them. |
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| sqlkev |
how are these boards compare to a behringer?
I might be interested in a few boards. |
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| BobEllis |
These boards make a completely analog single channel two way/bandpass active crossover with several EQ options. I have not listened to the Behringer, so I cannot comment on sound quality. With good opamps and sound component choices you should have at least equal sound quality.
Linkwitz suggests that for dipole use digital crossovers might not be up to the task in terms of dynamic range and processing power.
The notch filters can make virtually any depth notch in one stage, as opposed to the ~15 dB limit per notch of the Behringer (for a 40 dB notch you'd use 3 notches at the same frequency). A notch such as used making a Cauer-Elliptic filter would use a lot of the Behringer's processing power. However if you are simply notching out a large breakup mode, 15 dB is usually enough.
Note that you will need multiple boards for most applications- 2 for a stereo 2 way, 4 for 3 way or 2 way plus sub, 6 for a 4 way. Also, this board is not designed as a prototyping board, rather it is a platform to build your final product. Not that changes can't be made, but ease of repeated adjustment was not a design goal and you'll have to desolder parts to change values. |
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| vatofale |
Added myself for 2 boards and a psu board
Cheers |
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| RDV |
Added myself for two Xover bords and one PSU board.
Regards
RDV |
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| BobEllis |
To simplify my record keeping and try to improve accuracy, I've set up a PayPal shopping cart for purchase of boards and kits. You can use a credit card even if you have no PayPal account. If you don't have a credit card, email me to make arrangements.
Go to http://mysite.verizon.net/vze3xvxs/audio/id19.html. Click on the "add to cart" buttons as desired. You can increase the quantities in the cart.
Be sure to select a shipping option. In the US, most orders will fit in the Priority Mail envelope. Outside the US, I can fit 10 boards or 6 boards and a power supply kit into a small GPM envelope. Small quantities of 100 nf will fit as well. If you have more than one PSU kit, you'll need the large envelope for up to 4 psu kits. If in doubt, email me and I'll figure out shipping cost.
Pricing:
Filter Boards $5
PSU Boards $6.25
PSU Kit $28 (includes board, parts and heat sinks)
I also will offer 470 uF Panasonic FCs for the filter boards (2 required per), 100 nF/100V Epcos Film caps for decoupling, 1500 uF 35V Panasonic FCs and BC546C/BC556C. |
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| pinkmouse |
Bob, Jens, could you just clarify something for me?
I'm just getting used to the topology you used to set your high and low pass filters, as you know it's a little different to the format Rod uses for LR and I'm just trying to get my head round it.
High pass is simple enough, for example, if C3/4= 10nF then C11 is 20nF, and if R6/7/14=10K then R19=17K5.
But for the Low Pass, am I right in thinking that C14/15/21 are all 20nF, R25/26 are 10K, R29 is 20K, and R36 is 35K?
It would be really valuble if you could put values on the components in the worked examples given in the manual rather than just designators. |
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| BobEllis |
Hi Al,
This is the Sallen-Key equal component value topology. C11, C12, C21, C22 are intended to be bandwidth limiters - around 100 to 220 pF. This will bring the gain of the section to unity at high frequency. The four components attached to the + input are the frequency determining components. An advantage of this topology is you don't have to find precision caps that are available in twice the value of your primary cap or double them up for the low pass section when you want LR4 response.
Using your example values, 10 nF and 10K, you get a cutoff frequency of 1591 Hz. The Q is set by the ratio of R14 to R19. For a LR4 electrical response, each filter section must have a Q of .707. This gives R19 of 17K for R14 at 10K.
You can use Rod's calculator for LR4 (and have the same topology) by jumpering R14 and omitting R19 and C11 (or equivalent in the other sections).
For an LR2 electrical response, set Q=.5. This means you leave R19 open and you can jumper R14 or choose the value for lowest DC offset (equal to the parallel equivalent of R6 and R7).
Don't forget that a Linkwitz-Reilly electrical response doesn't necessarily mean that you'll end up with L-R acoustic response. I'm pretty sure you know this Al, it's for the relatively new guy's benefit. For example a Q=.7 natural acoustic rolloff combined with a Q=.707 second order electrical filter at the same frequency will result in an LR4 acoustic sum. You wouldn't use an LR2 electrical response, even though the filter is only second order.
An update of the manual is on my to do list. Do you mean that you'd like to see the schematic in the examples annotated with C3/10 nF, R6/10K, etc?
I put together a spreadsheet for determining component values for those who just want the values without caring how they are derived. There is a link to where I posted it on the Wiki and it is on my web page Here |
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| pinkmouse |
Gotcha. That makes perfect sense now you've broken it down. I was having a wood/trees perceptual glitch I think! The application I'm using the PCB for is actually a LR4 bandpass for a sub, at 20 and 80Hz, I just used those component values for illustrative purposes as the math was more obvious.
As for the schematics in the manual, that's exactly what I meant. For instance, If I looked at your 2 way example with the LR4 crossover, and seen that C11/12/21/22 were all 100pF, it would probably have clicked that they were all compensation caps and not part of the frequency shaping.
Just downloaded the spreadsheet, that makes everything so much more straightforward :) |
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| BobEllis |
Glad my explanation helped.
I'll have to get my photoshop enabled kid on the annotations. ;) |
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| pinkmouse |
Quick question in addition to the above, am I right in thinking that the Fo for the compensation network is given by the usual 1/(2Pi x R x C)?
Thanks. |
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| pinkmouse |
| quote: | Originally posted by BobEllis
I'll have to get my photoshop enabled kid on the annotations. ;) |
Tell me the numbers and I'll update Jens' Eagle schematics. I think I've still got them around somewhere. :) |
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| BobEllis |
| quote: | Originally posted by pinkmouse
Quick question in addition to the above, am I right in thinking that the Fo for the compensation network is given by the usual 1/(2Pi x R x C)?
Thanks. |
Yes it is.
I'll email you the numbers when I get a chance. I appreciate the help. |
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| mrshow4u |
| Hello, I am interested in 6 filter boards and 1 power supply kit. What do I need to do next, plese? |
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| BobEllis |
| quote: | Originally posted by mrshow4u
Hello, I am interested in 6 filter boards and 1 power supply kit. What do I need to do next, plese? |
See Post 24 above.
Note that I will be ordering boards and parts after the close date, expecting to begin shipping in mid September. |
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| p_ete2003 |
Bob, you have email from me.
Best regards,
Pete |
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| BobEllis |
| Buy closes 8/18/06 |
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| samsagaz |
| well, im interested, im from Argentina, but really want to know abt the quality of the kit.... its an good xover? someone tested it? |
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| BobEllis |
Killjoy
Sorry - I was just posting updates in the group buys thread.
Boards will be delivered to me next week, and I will begin shipping shortly afterwards.
samsagaz
There were a few repeat buyers, so I assume they are happy with the crossover design.
The PSU was offered as a kit since most will be doing the same thing with it. I figured everyone would be doing something different with the XO so a kit didn't make sense. It was just a bare board with guidance in the form of a spreadsheet and manual.
I ordered 50 extra boards but all are spoken for. Maybe if there is a round four... |
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| samsagaz |
ok, thanks, i need xovers for the following speakers
pair of 3 way system
pair of 2 way system
and one fron channel 2 way system (MTM)
so i will need 7 kits right?
(thats a lot of money :S) :D |
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| BobEllis |
7 boards would be required to complete the projects you describe.
However, none are available unless there is enough interest for another 100 or more.
That makes 7 for round four. Anyone else? |
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| BobEllis |
The PSU kits are kitted except boards and heat sinks (due to arrive today) I will start packing orders and expect to start shipping by Friday.
I suffered a hard drive crash yesterday. I'm glad PayPal will give me packing lists, since my backups were corrupted. All PayPal orders are fine.
If you did NOT with PayPal, please drop me a note telling me what you ordered
I think I have the few who sent checks, but I want to be sure. |
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| samsagaz |
well, im really new in electornics, im building some amps, and will build some speakers soon, will be great to use Active Filters. i need an kit for each speaker? my system will have 2 and 3 way systems.
with one PSU How many boards i can use?
have you any soft start boards to sale?
Regards. |
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| BobEllis |
Each board is a single channel that can be either two way or bandpass.
A two way stereo setup would require two boards.
A three way stereo system would require four boards.
If you plan a 2.1 system with two way mains and a sub, it counts as a three way system.
Add another board if you plan to use a high pass filter on the sub.
A power supply can deliver 500 mA. This is enough to power 4-6 filter boards depending on features used. Each filter board has up to 9 opamps that typically draw 10 mA each at idle. They probably won't draw much more current into typical loads, but if you try to drive a very low impedance load, expect to see a bit more current drawn.
I had a soft start board ready for prototyping but wasn't smart enough to back it up before my hard drive crashed. I'm working on it again. Hopefully it will be ready to go soon. |
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| samsagaz |
ok, for an Home Theater with
two 3 Ways Front Speakers
one 2 Ways center channel
two 2 Ways Rear Channels
one Subwoofer.
I will need 9 boards, right? so i can use 9 boards and 2 PSU, that will be enough, right?
Im interested in the SoftStart too, but can start with this boards first :)
i relly need each kit with FULL COMPONENTS is not easy to find good and legit components in Argentina.
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| DonoMan |
| Interested, but can I not make a 2-way with a subsonic filter with just 1 board? |
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| BobEllis |
Sam,
OK, for an Home Theater with
two 3 Ways Front Speakers - 4 filter boards
one 2 Ways center channel - 1 filter board
two 2 Ways Rear Channels - 2 filter boards
one Subwoofer. 0, 1, 2 or 3 filter boards
The number of subwoofer boards depends on how you are handling the bass management and whether the sub needs EQ, High pass or LT. The EQ and LT sections are independent - you can patch them into the system anywhere. For example you can use the midrange board's Linkwitz transform for your sub. If that is all you need for the sub, you wouldn't need to use a separate board for it.
If you use your HT processor's subwoofer crossover and your sub does not need a rumble filter, then you don't need any AF4 boards for the sub.
If you use your HT processor's subwoofer crossover and your sub does needs a rumble filter, then you need 1 AF4 board for it.
If you do not use your HT processor's subwoofer crossover (bass management set to send all bass/LFE to the mains) and your sub does not need a rumble filter, then you need 2 AF4 boards. These would perform high pass to the mains and low pass to the sub.
If you do not use your HT processor's subwoofer crossover (bass management set to send all bass/LFE to the mains) and your sub does needs a rumble filter, then you need 3 AF4 boards for it. Two would perform high pass to the mains and low pass/mixing to the sub. The third would provide the high pass.
COMPLETE kits for the crossover are difficult because everyone's needs are different. That's why we designed so much flexibility into it. I can provide the electrolytic and film bypass caps. These are available through my website. Gengis may have some OPA2134s left over. With some thought you might be able to use the same value cap for all of your filter sections and take advantage of quantity pricing. Just keep the resistances reasonable. Some of the major distributors like Digikey and Mouser might be willing to ship to you.
Donoman -
Perhaps you could make the subsonic filter out of an unused EQ or high pass section (say you used 2nd order high pass for the mains there would be an unused high pass section on the board), but it would require some modification to the board. A two way plus sub is a three way system.
This board is set up to be a bandpass (what a sub with subsonic filter uses) or high and low pass filters. A two way plus sub with rumble filter requires two bandpass sections (sub & Woofer) plus a high pass section. This requires three boards. For stereo with a single sub, you could mix the stereo signals from the buffered output and feed to a single board for subwoofer bandpass. |
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| samsagaz |
| ok, so i will purchase 7 boards, so i will need 1 or 2 PSU? |
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| BobEllis |
| With 7 boards using filters but no EQ you're about at the limit for one PSU. I'd suggest two. |
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| F1 FAN |
Hi Bob,
I have finished my 2way crossover and it tested great on an Audio Presicion analyzer but I have found a small problem.When powering up slowly with a variac one or both rails on the regulators fail to start .This has not happened yet when power ing without the variac.
Since the output is direct coupled to my midrange amp I am conscerned that if one rail does not come on then a large DC offset may occur and put the driver at risk.
Have you expierienced this problem?Will this only happen when power is soft started.?
I used the LM4040 ,ommited the pots and used 2k for R11 and R13.every thing else is as in the schematic dated 06-04-2006.
Thanks for your time.
Fred
PS.I will probably want to purchase more boards in the next group buy. |
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| BobEllis |
I haven't had a fail to start when powered straight from the line unless the output was shorted. I got good consistent starts to 900 mA.
I didn't really have any significant instance of not starting when using the variac, although once I verified that the circuit worked I used the variac to set AC input voltage to the PSU and just switched it on.
Come to think of it, I did have an issue with the higher voltage version not starting when bringing it up slowly. Simply turning it on it fires right up.
I suggest verifying reliable starting with your crossovers before connecting your amps. I always use a large value cap (25+ uf) to protect the tweeter, anyway. |
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| F1 FAN |
Thanks Bob
I will cycle the power on and off for several days to see if all is well before putting it in the system.I do have a 47uf Solen poly cap for the tweeter but nothing on the mid/woof. |
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| F1 FAN |
It looks like the start up problem is a non issue.
The regs start properly every time if I turn the unit on without variac. |
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| BobEllis |
I will order AF4 boards this Friday. Orders have just been slowly trickling in, so I don't think I will order too many extras.
If you want AF4 boards, get your order in by Friday or at least let me know.
EDIT: I only have 6 PSU2.2 boards left after filling existing orders. These are also available with the parts kit. |
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| samsagaz |
Active Filter Four PCB
Item #AF4 $38.50 USD
PSU 2.2 Kit
Item #PSU $56.00 USD
its what i have in queue now, btw, please explain me about the
4 pieces 470 uF/25V Panasonic FC capacitors
10 Pieces 100 nF/63V Epcos Polyester Film capacitor
25 pieces BC546C
25 pieces BC556C
i mean, i need to purchase that stuff too? i want to order as much as i can, cos here in Argentina is not easy to get electronic devis at chep price.
if these are part of the boards i will purchase it :) |
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| samsagaz |
| Hope you can give me an small discount for my big order :) at least free shipping to Argentina |
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| BobEllis |
Hi Sam,
The PSU kits are complete with all parts, you don't need to buy anything for them except mounting hardware.
The 470 uF Panasonic caps are used on the AF4 boards for supply decoupling. You might be able to do without them, but I offer them since I buy so many for the PSU kits. There are spots for two per board.
The 100 nf caps are used for local opamp decoupling. This is absolutely required. Of course you can use any 2.5 x 7.5 mm cap with 5 mm lead spacing that you want.
The BC546C and BC 556C are leftovers from the first power supply buy. I needed 500, but at the time I needed to order parts these were only available in lots of 10,000 each. I still have a little over 4,000. I don't see using that many any time soon so I offer them for sale. They are rather low noise, high hfe (420-800) TO-92 devices. They could be used for input differentials and a hose of other places.
Your order is about average for this time around. Board pricing is based on a quantity that has not been reached, so you are getting a discount there. Please contact me off line to arrange shipping before placing your order. Argentina does not accept USPS Global Priority Mail, so it looks like your shipping via airmail will cost a little more.
I'll buy enough boards so that I will reach the break even point when/if the remainder get sold. If they don't sell, I'll just have to build more active speakers. :clown: |
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| BobEllis |
Boards have been ordered for round 4 group buy. Shipment to me is scheduled for December 6.
There are 32 extras coming.
I have 4 PSU2.2 kits left.
Status reporting will be in the group buy thread HERE |
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| Tarasque |
Hi Bob,
I would be interested in the 4 PSU boards. |
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| BobEllis |
| Sorry, all filter and PSU boards/parts are gone. Peraps someone wants to run another group buy? I don't have the time for the foreseeable future. |
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| tcpip |
Great board, but I was wondering about a couple of things:- What high-accuracy caps do you suggest I use for the freq-setting components? I'm wondering about which caps (and from which reseller) will fit into that space.
- I tried the spreadsheet, and it gives me LP and HP only for q of 0.5 or greater. What if I need lower Q? Optimised active filters sometimes have funny Q requirements
Thanks for a great design. |
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| tcpip |
| One high-accuracy cap type that I've been able to find is the Vishay-Roedenstein 1% MKP film caps, 1837 series. They'll require 7.5mm x 9mm of board real estate for the 100nF value. Will these fit? And is there anything better or less expensive that one can use? |
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| AndrewT |
| quote: | Originally posted by tcpip
......I tried the spreadsheet, and it gives me LP and HP only for q of 0.5 or greater. What if I need lower Q? Optimised active filters sometimes have funny Q requirements.... |
try cascading two or more 2pole filters. |
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| tcpip |
Some other options I found were- Panasonic PPS film caps, from their ECHS series, on Digikey. 2% tolerance. Digikey part number for the 100nF cap is PS1H104G-ND. Priced $1.95 in single pieces. Unfortunately you'll need 14.5x6mm board area for each cap, and 10mm lead pitch.
- Panasonic P series polypropylene caps, Digikey part number P3104-ND for the 100nF, 2% tolerance, $0.86 in single pieces. But 17.5x7mm board real estate needed.
- Panasonic ECQ-P(Z) series polyprop film caps, Digikey part number P3925-ND for the 100nF value, 2% tolerance, $0.82 in single pieces, but 17x7.5mm board area needed, 7.5mm lead pitch.
Which of these will fit?
So, am a bit confused about what caps to look for. :( |
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| tcpip |
| quote: | Originally posted by AndrewT
try cascading two or more 2pole filters. |
Won't cascading increase the Q? Or are you talking about cascading two filters at two different "knee" frequencies, to spread the slope out? |
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| AndrewT |
Hi,
cascade a pair of Butterworth (Q=1/sqrt(2)) and the output is Q=0.5 (Bessel) just right for 4pole Linkwitz Reilly.
Cascade a pair of Q=0.5412 (gain =1.1523) and Q=1.3065 (gain =2.2346) gives Q=0.7071 (Butterworth and overall gain of 2.575, +8.2db)
The resulting Qt=Q1*Q2....*Qn
That's the beauty of this topology, ECV S&K, gain and Q can be varied without changing F, they are independant.
Unity gain filtering involves a lot of maths and unmatched component values that require absolute accuracy rather than just matching but at a fixed gain cf +8.2db of the ECV Butterworth. |
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| tcpip |
| quote: | Originally posted by AndrewT
The resulting Qt=Q1*Q2....*Qn |
Does this mean I can cascade a pair of filters, each with Q=0.5, and I'll get a resultant Q of 0.25? |
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| tcpip |
And any idea what caps to use with this board? The manual specifies 7.5x5.5mm cap footprint, with 5mm lead pitch. I can't seem to find any reasonably tight tolerance cap of the size we need in that footprint.
Maybe I should just switch to 5% tolerances. After all, for passive XO we use 10% tolerance caps anyway. |
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| AndrewT |
Hi,
buy 100s of 5% and select MATCHING values for each frequency. Try to better 1% for caps and better than 0.3% for resistors.
Polyester are rarely available in 1%.
1% polystyrene used to be readily available, but more difficult now.
1% or 2% polypropylene are available at more cost and in the larger values in bigger packages.
1% Mica are available in smaller values but have the wrong pin pitch.
No easy answer.
BTW,
single pole fiters can get away with 5%, 10% is rubbish,
as the filter steepness increases the required accuracy increases to match.
for 2pole you may get away with 2% and for 4pole 1% but I would go for closer matching, absolute accuracy is not required for frequency, but it is needed for gain (just as well DMMs are more acurate on DC voltage, pity about the resistance accuracy) |
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| tcpip |
This is BC Components metallised polyprop filter caps, 416 series. 2% tolerance. The 100nF has footprint of 6x 7.2mm, lead pitch 5mm. Digikey part number BC2054-ND. Sold for $0.63 each.
This one is a shade shorter in length and half a millimetre wider in fatness, than what the board seems to allow. Maybe it'll do, maybe it won't.
What do the rest of you use? |
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| tcpip |
| quote: | Originally posted by AndrewT
Polyester are rarely available in 1%.
1% polystyrene used to be readily available, but more difficult now.
1% or 2% polypropylene are available at more cost and in the larger values in bigger packages.
1% Mica are available in smaller values but have the wrong pin pitch.
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I guess Bob and Jens had some cap in mind when they did their designing? What were they planning to use? And I don't remember this factor being discussed in the threads either. Is it only me who's struggling to find good caps? Some people have posted photos of populated XO boards, I wonder what they used. |
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| AndrewT |
an old gripe of mine.
I did not see any value in flogging it yet again, but I joined this one very (too) late to have any influence. |
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| tcpip |
| quote: | Originally posted by AndrewT
an old gripe of mine.
I did not see any value in flogging it yet again, but I joined this one very (too) late to have any influence. |
It's a relief that Jens has allowed the posting of his Eagle files on the thread; one can try making more space for the caps if at all there is any space to play with. Getting a DSPTH board made at this end of the world is easy; I can get them done quite inexpensively. |
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| BobEllis |
If you can live with only 10 nf, Wima FKP2 1% will fit.
I have also used Panasonic ECQ series 2% polyprops - they are a bit big at 100 nf but if you can live with the lead length of them standing above (or below) the board they sound nice.
Otherwise I pull out the big bag of 5-10% caps and my meter and pick matching caps.
The cap footprint was a tradeoff between available board space and the functions available on the board. One of the design constraints was to make the board fit the free version of Eagle's 80 x 100 mm footprint. I would have preferred two all pass sections, but I cannot cope with SMDs... |
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| AndrewT |
Hi Bob,
can you explain when/what circumstances an all pass becomes advisable?
Some low pass crossover sections are shown fed direct from the input buffer and others show the LP fed from the LP section of the band pass section. Why the difference? |
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| tcpip |
| quote: | Originally posted by BobEllis
If you can live with only 10 nf, Wima FKP2 1% will fit. |
Who sells these?
| quote: | | I have also used Panasonic ECQ series 2% polyprops - they are a bit big at 100 nf... |
A bit big??? They are huge by the standards of this board. As per my Digikey data sheet, they're 17mm long, as against this board's limit of 7 or 7.5mm. :(| quote: | | ...if you can live with the lead length of them standing above (or below) the board they sound nice. |
You mean let them float so high that they are above other components? Okay... that's a thought. Options increase.
| quote: | | Otherwise I pull out the big bag of 5-10% caps and my meter and pick matching caps. |
Yes, that'd do too, I guess. I can just use ordinary polyester caps I guess.
Any pointers about which types of caps "sound" better?
| quote: | | I would have preferred two all pass sections, but I cannot cope with SMDs... |
Oh absolutely. I'd agree on that SMD front totally. Thank God you haven't gone SMD, though Jens seems quite comfortable with the idea.
And about Q less than 0.5, do I just cascade stages as AndrewT was suggesting? |
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| AndrewT |
Hi Tcpip,
what use have you in mind that requires Q<0.5? |
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| F1 FAN |
Hi tcpip,I used the BC components MKP 417 series 2% polyprop
available at digikey.They fit the board perfectly. |
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| BobEllis |
Mouser sells the Wima FKP2s, there must be another distributor on your side of the world.
I like the sound of polyprops better than polyester, not that I have done a direct comparison. I've heard that the FKP (polypropylene film and foil) sound better than the MKP (metalized polypropylene film), but I haven't used them yet.
Polystyrene and Teflon are supposedly the holy grail. Mouser has some polystyrene caps that I used in a crossover. They are cheap, have 2 mm lead spacing and are only 10% so it was buy a big batch and sort. I was surprised how tightly they grouped, mostly within 1% of each other, but 5% off specified capacitance. This is my best sounding crossover to date, but I went from ~LR4 with notch for woofer to 8th order initial rolloff Cauer at a lower frequency. Again, no direct comparison to the previous polypropylene version.
F1 Fan, thanks for the suggestion. |
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| F1 FAN |
Your welcome Bob,I should mention I used 24nf and 47nf from the 417 series for the filter sections.The 100nf has bigger spacing but the 416 series 100nf will fit.
I used the 100nf Panasonic ECQ stacked films for the bypass caps.Digikey part P4525-ND
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| tcpip |
| quote: | Originally posted by AndrewT
what use have you in mind that requires Q<0.5? |
Basically, I've done paper designs of many active xo's by taking their passive xo's and trying to convert them to active with exactly the same phase and SPL curves. I have found that this can be done, but after optimising the curves, I get filter stages with very strange Q sometimes. Omitting those stages is not an option; I get clearly unacceptable levels of phase errors.
During these experiments, I've seen that Q < 0.5 often occurs in one of the stages. That's why I was asking.
For a report of one such experiment, see here. In this example, there was no low-Q stage, but in other cases, it's happened. |
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| tcpip |
| quote: | Originally posted by F1 FAN
Hi tcpip,I used the BC components MKP 417 series 2% polyprop
available at digikey.They fit the board perfectly. |
Yes, those were the closest fit among the ones I found. Thanks for the confirmation. :)
| quote: | Originally posted by BobEllis
Mouser sells the Wima FKP2s, there must be another distributor on your side of the world. |
Thanks. I'll check Mouser. Let's hope their Website will be easier to use than the nighmarish www.mcminone.com --- that's easily the worst online retailing electronics components Website I've seen.
| quote: | | I like the sound of polyprops better than polyester, not that I have done a direct comparison.... |
Thanks a lot. I'll keep these in mind. Of course, actually selecting caps for any project may be influenced more by size than type, given this tight-fit board. :)
BTW, how do you design your active xo's? Do you use SoundEasy, LSPCad or some similar package? |
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| BobEllis |
When it comes to hobby software, I am a tightwad. I use Speaker Workshop to measure in the cabinets. Then I use an eyeball approach to add a little higher Q to compensate for a droop near the crossover and vice versa. I get the impression that Linkwitz does it this way. So I figure with careful measurement and willingness to go a few iterations, I can get pretty good results, too.
Notches and shelving are done the same way. Baffle step is almost a textbook thing, although I tend to reduce it if the speakers will be close to the wall. I use "The Edge" for predicting baffle step response.
I build the XO, measure and tweak from there. Tweaking will be a lot easier now that I have a few of Jens' active filter 2 boards running. Nicely adjustable, with a prototype area that I have populated with sockets for adjustable notch filters.
SWCad from Linear is a nice free program that allows me to verify my spreadsheet calculations. It is particularly handy when doing Cauer filters.
It would be nice to have software to predict off axis response, but measure/tweak/repeat gives satisfactory results. Besides, for me much of the fun is the building. Wouldn't want that to go too fast. ;) In some ways I get more satisfaction out of an unsuccessful experiment - it makes it easy to justify the next project. Thank goodness I only have my bank account to answer to. :cool: |
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| Primetime |
Hi,
I'm more than a bit late in joining this GB... I would be greatful if any of you have a board or two to spare... Pls let me know..
I'm not sure if it is too much to ask, but if Jen or Bob could be kind enough to send me a pdf of the pcb layout, I could try to etch one myself ;) though I would much prefer to have a professionally made board. |
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| frez |
Hi,
I'm, also interrested in a pair of PCBs. Any chance there's someone out there with a soft spot for a fellow DIYer?
THNX
/Frez |
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