I’d like to use a plate amp to drive an EBS subwoofer. I’d need to fit a subsonic filter to avoid over excursing. Restricting the choice of plate amps to those with subsonic filters built-in, cuts out many good options (including one I already own, below)
How easy would it be fitting a filter? I was thinking of this amp
http://www.jaycar.com.au/productVie...d2=&pageNumber=&priceMin=&priceMax=&SUBCATID=
and this configurable subsonic filter
http://sound.westhost.com/project99.htm
Thanks
How easy would it be fitting a filter? I was thinking of this amp
http://www.jaycar.com.au/productVie...d2=&pageNumber=&priceMin=&priceMax=&SUBCATID=
and this configurable subsonic filter
http://sound.westhost.com/project99.htm
Thanks
jag
Is this what you were referring to
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=266-242
That appreantly attenuates across all frequencies
A configurable subsonic filter can be set to filter out at say 24 dB/ ocatve, below a configurable (by change of components) frequency, ie below say 18 Hz.
the http://sound.westhost.com/project99.htm does that, but I dont know if/ how it could be used with a plate amp
Is this what you were referring to
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=266-242
That appreantly attenuates across all frequencies
A configurable subsonic filter can be set to filter out at say 24 dB/ ocatve, below a configurable (by change of components) frequency, ie below say 18 Hz.
the http://sound.westhost.com/project99.htm does that, but I dont know if/ how it could be used with a plate amp
No that's just an attenuator, that makes EVERYTHING quieter, so it's useless in this discussion.
Here's one by the same manufacturer, this is a 12db/oct, 30 hz high pass filter, aka rumble filter. http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=266-248
Or you can make your own. Also, don't discount the fact that the reason that most plate amps have no rumble filter is usually because they naturally drop off fast below 20 or 30 hz anyway, which is a type of rumble filter anyway. Try to find response graphs of the amps you are interested in. They probably won't be strong down low anyway.
Passive line level crossovers can be used up to 12 db/oct slope. If you need more, you need active, in which case the thing you linked to probably does everything you need. IMO, I would get a behringer xo if I needed to go active. The project rumble filter is probably cheaper though.
Here's one by the same manufacturer, this is a 12db/oct, 30 hz high pass filter, aka rumble filter. http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=266-248
Or you can make your own. Also, don't discount the fact that the reason that most plate amps have no rumble filter is usually because they naturally drop off fast below 20 or 30 hz anyway, which is a type of rumble filter anyway. Try to find response graphs of the amps you are interested in. They probably won't be strong down low anyway.
Passive line level crossovers can be used up to 12 db/oct slope. If you need more, you need active, in which case the thing you linked to probably does everything you need. IMO, I would get a behringer xo if I needed to go active. The project rumble filter is probably cheaper though.
jag
A high pass filter at 30 hz (the lowest of the filters at PE of that brand) would attenuate all the gains at 15 – 30 Hz ~ for HT ~ that I’d get with an EBS.
The subsonic filter I posted is “a pair of cascaded 18 dB/octave filters, giving an ultimate rolloff of 36 dB/octave”: perfect for EBS. The -3 dB point is chosen by the capacitor values.
There’s no response graph posted for the plate amp I’d like to use, but the vendor says its one of their best. I’d assumed that a reasonable plate amp might only drop off say 1-3 dB between say 25 Hz and 12 Hz.
I don’t have a problem making my own, the link I’ve posted is a diy project.
My only uncertainty is how to connect it with a plate amp . . your links have suggested (doh!) it should best be connected between the HT sub out, and the plate amp.
cheers
A high pass filter at 30 hz (the lowest of the filters at PE of that brand) would attenuate all the gains at 15 – 30 Hz ~ for HT ~ that I’d get with an EBS.
The subsonic filter I posted is “a pair of cascaded 18 dB/octave filters, giving an ultimate rolloff of 36 dB/octave”: perfect for EBS. The -3 dB point is chosen by the capacitor values.
There’s no response graph posted for the plate amp I’d like to use, but the vendor says its one of their best. I’d assumed that a reasonable plate amp might only drop off say 1-3 dB between say 25 Hz and 12 Hz.
I don’t have a problem making my own, the link I’ve posted is a diy project.
My only uncertainty is how to connect it with a plate amp . . your links have suggested (doh!) it should best be connected between the HT sub out, and the plate amp.
cheers
otto88 said:
I don't know of any subwoofer plate amp that doesn't have a subsonic (aka "rumble") filter. The Jaycar amp almost certainly has one, since it has a boost at 35Hz. The boost is usually added by making the subsonic filter have a high Q. This results in a peak at the boost frequency followed by a 12-db rolloff for the low frequencies.
There is a small spreadsheet at the following link to calculate the resistor values for different amounts of boost and different cutoff frequencies. Look at the schematic on this page for some ideas on how to modify the filter to fit your needs: http://home.comcast.net/~neilrdavis/Plate_amp_mods/30009_Mods.htm
I just posted that as an example. These are very easy and cheap to make, much cheaper and easier than the active project you linked to, so I only thought I 'd mention it if you haven't heard about it. You can make them with a 6db or 12db slope at any frequency you like.
Sounds like you do not want a passive solution though, and that's fine. That project should work for you, but how much will it cost? There are a variety of options that don't cost much, but if you want to try that project, it should work for you. (Just to clarify, I only read the title of your link, and assume it's what you want.)
Both your link and my link are both line level solutions, so they have to be placed before the sub amp.
Sounds like you do not want a passive solution though, and that's fine. That project should work for you, but how much will it cost? There are a variety of options that don't cost much, but if you want to try that project, it should work for you. (Just to clarify, I only read the title of your link, and assume it's what you want.)
Both your link and my link are both line level solutions, so they have to be placed before the sub amp.
An externally hosted image should be here but it was not working when we last tested it.
This is pretty typical of plate amp performance. IIRC it's from one of the current partsexpress plate amps. Plate amps are a notoriously bad choice for low frequency apps. Ymmv, but I think they all pretty much work like this. Plate amps are cheap and not really meant for serious subsonic duty.
Along the same lines as Elliot's circuit is this filter circuit board:
Originally from Audio Amateur 4/75:
http://www.audioxpress.com/bksprods/products/pcbf-6.htm
This basic circuit has been updated over time ( w better op amps as they became available ).
I first built one as a (HP) rumble filter for my turntable in the 70's.
It can be modified to fit a variety of needs
Originally from Audio Amateur 4/75:
http://www.audioxpress.com/bksprods/products/pcbf-6.htm
This basic circuit has been updated over time ( w better op amps as they became available ).
I first built one as a (HP) rumble filter for my turntable in the 70's.
It can be modified to fit a variety of needs
Neil
Thanks for the link to the spreadsheet
> I don't know of any subwoofer plate amp that doesn't have a subsonic (aka "rumble") filter. The Jaycar amp almost certainly has one, since it has a boost at 35Hz. The boost is usually added by making the subsonic filter have a high Q. This results in a peak at the boost frequency followed by a 12-db rolloff for the low frequencies.
Yes the Jaycar amp has a boost at 35 Hz. While a high Q gives a boost at the filter frequency, how do we know the amount of rolloff below that?
It probably is enough for most sealed alignments; some vented alignments up to a watts input, down to a Hz, etc; but safe EBS requires a very steep rolloff, dependent on the driver used and output needed.
To avoid risk of blowing the sub driver, I believe its bets to implement an appropriately designed subsonic filter
Thanks for the link to the spreadsheet
> I don't know of any subwoofer plate amp that doesn't have a subsonic (aka "rumble") filter. The Jaycar amp almost certainly has one, since it has a boost at 35Hz. The boost is usually added by making the subsonic filter have a high Q. This results in a peak at the boost frequency followed by a 12-db rolloff for the low frequencies.
Yes the Jaycar amp has a boost at 35 Hz. While a high Q gives a boost at the filter frequency, how do we know the amount of rolloff below that?
It probably is enough for most sealed alignments; some vented alignments up to a watts input, down to a Hz, etc; but safe EBS requires a very steep rolloff, dependent on the driver used and output needed.
To avoid risk of blowing the sub driver, I believe its bets to implement an appropriately designed subsonic filter
just a guy
"This is pretty typical of plate amp performance"
Those smooth curves to me look to me like modelled performances of a plate amp - combined with mid level sub drivers, at different upper XO frequencies.
While I dont think plate amps are generally that great, I dont believe that the amp alone drops as shown on the graph - between 20 and 10 hz by about 10! dB
"This is pretty typical of plate amp performance"
Those smooth curves to me look to me like modelled performances of a plate amp - combined with mid level sub drivers, at different upper XO frequencies.
While I dont think plate amps are generally that great, I dont believe that the amp alone drops as shown on the graph - between 20 and 10 hz by about 10! dB
otto88 said:
Every plate amp that I have looked at uses a 2-pole Sallen-Key rumble filter. The two poles give you a 12db rolloff. If you make the filter Q greater than .7, it will give you boost before the rolloff, but it will still result in the 12db rolloff. So you know what the subsonic filter is and the spreadsheet helps you change the Q and cutoff frequency.
Usually 12db/octave is considered an appropriately designed subsonic filter. Also, there are usually coupling capacitors in the circuit that provide additional rolloff. So you are likely to get good protection for your sub from any subwoofer plate amp. Whether or not you want additional rolloff is your design decision.
I thought I'd add my two--cents.
Hard for any manufacturer to make and to advertize an amp with any diminution in the 20-20k band.
But, in my fairly long experience, you really want a really really sharp cutoff (like 36dB/8ave) and you really need it to start somewhere north of 20 Hz, like 25... since there is likely to be a little bump at that point (good) and no real cut till below 20 Hz. If you start at a fantasy point, like 18 Hz, you end up cutting too little.
I guess it would be good to keep those useless subsonics out of the amp chain right from the start and again right before the amp. I bet there's lots of overloading going on inside those DC-to-llight amps from junk you can't hear anyway.
Given the inaccuracies of filters esp. LF cut, best to have a single bass line. Otherwise, maintaining two (or more) woofer channels, you are creating separate bass pseudo-phases, and pseudo-sounds where none existed before. All this and many more reasons are real good rpersuasion to mix your base below, say 100-140 Hz. I think you should do so even if you choose to use two independent woofers for some odd reason.
Hard for any manufacturer to make and to advertize an amp with any diminution in the 20-20k band.
But, in my fairly long experience, you really want a really really sharp cutoff (like 36dB/8ave) and you really need it to start somewhere north of 20 Hz, like 25... since there is likely to be a little bump at that point (good) and no real cut till below 20 Hz. If you start at a fantasy point, like 18 Hz, you end up cutting too little.
I guess it would be good to keep those useless subsonics out of the amp chain right from the start and again right before the amp. I bet there's lots of overloading going on inside those DC-to-llight amps from junk you can't hear anyway.
Given the inaccuracies of filters esp. LF cut, best to have a single bass line. Otherwise, maintaining two (or more) woofer channels, you are creating separate bass pseudo-phases, and pseudo-sounds where none existed before. All this and many more reasons are real good rpersuasion to mix your base below, say 100-140 Hz. I think you should do so even if you choose to use two independent woofers for some odd reason.
Neil
> Every plate amp that I have looked at uses a 2-pole Sallen-Key rumble filter
Thank you, I didn’t know that.
12 db/octave could be an adequate subsonic filter in most situations, but not for EBS. If I knew how to post a graph of the excursion requirements from Unibox, I would. While (in one alignment I’m considering) with a 100 watt amp, excursion required is comfortably under Xmax at 13 Hz; by 10 Hz its nearly double Xmax.
In the vast majority of material, there’s no signal below 13 Hz. But a 1 in 100 (?) soundtrack could easily blow the sub driver. So 12 db/octave isn’t adequate.
rabbitz
Thank you, I didn’t know that Jaycar and Altronics had kits.
So if Neil’s general comment that most plate amps has a 2-pole Sallen-Key rumble filter of 12 db/octave does apply to the Jaycar AA0508 (do you know?) and an 18 db/octave filter is added between the LFE and the plate amp input, that’s 30 db/octave, which I think would be ok for EBS.
> Every plate amp that I have looked at uses a 2-pole Sallen-Key rumble filter
Thank you, I didn’t know that.
12 db/octave could be an adequate subsonic filter in most situations, but not for EBS. If I knew how to post a graph of the excursion requirements from Unibox, I would. While (in one alignment I’m considering) with a 100 watt amp, excursion required is comfortably under Xmax at 13 Hz; by 10 Hz its nearly double Xmax.
In the vast majority of material, there’s no signal below 13 Hz. But a 1 in 100 (?) soundtrack could easily blow the sub driver. So 12 db/octave isn’t adequate.
rabbitz
Thank you, I didn’t know that Jaycar and Altronics had kits.
So if Neil’s general comment that most plate amps has a 2-pole Sallen-Key rumble filter of 12 db/octave does apply to the Jaycar AA0508 (do you know?) and an 18 db/octave filter is added between the LFE and the plate amp input, that’s 30 db/octave, which I think would be ok for EBS.
just a guy
(I wasn’t suggesting that you drew the graph) Even if they “only for low bass” I’m amazed that *any amps can have such a highly limited bandwidth.
If you’re doing a 0.1 LFE sub on a budget, and want say 15 - 150 Hz +/- 3 dB, would a PA amp be better?
Ben
We agree about the need for a sharp cutoff (like 36 dB) the 18 Hz I mentioned wasn’t so much a starting point, but as an example point by which the cut needs to start ‘kicking in, to protect below 13 Hz, where its needed.
That’s what I like about http://sound.westhost.com/project99.htm - it’s configurable.
> best to have a single bass line. Otherwise, maintaining two (or more) woofer channels, you are creating separate bass pseudo-phases, and pseudo-sounds where none existed before. All this and many more reasons are real good persuasion to mix your base below, say 100-140 Hz. I think you should do so even if you choose to use two independent woofers for some odd reason.
Not sure what you meant by “a single bass line”. Being an 0.1 for HT, it’s a single channel, only for LFE, below 120 Lz. Maybe you’re referring to eg a two way + sub(?)
Cheers
(I wasn’t suggesting that you drew the graph) Even if they “only for low bass” I’m amazed that *any amps can have such a highly limited bandwidth.
If you’re doing a 0.1 LFE sub on a budget, and want say 15 - 150 Hz +/- 3 dB, would a PA amp be better?
Ben
We agree about the need for a sharp cutoff (like 36 dB) the 18 Hz I mentioned wasn’t so much a starting point, but as an example point by which the cut needs to start ‘kicking in, to protect below 13 Hz, where its needed.
That’s what I like about http://sound.westhost.com/project99.htm - it’s configurable.
> best to have a single bass line. Otherwise, maintaining two (or more) woofer channels, you are creating separate bass pseudo-phases, and pseudo-sounds where none existed before. All this and many more reasons are real good persuasion to mix your base below, say 100-140 Hz. I think you should do so even if you choose to use two independent woofers for some odd reason.
Not sure what you meant by “a single bass line”. Being an 0.1 for HT, it’s a single channel, only for LFE, below 120 Lz. Maybe you’re referring to eg a two way + sub(?)
Cheers
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