Advice on DSP + Amp Upgrade for 2-Way Build (RSS210HF-4 & SEAS DXT)

[TomSR]

Hey everyone,


I’m looking to upgrade the DSP and amps in my 2-way build and could use some advice.


The setup is a sealed box using a Dayton RSS210HF-4 woofer and a SEAS 27TBCD/GB-DXT tweeter. I’m using DSP to extend the low end, and the speakers are mainly used for mixing.


Up until now, I’ve been running a pair of first-gen Hypex FA122 plate amps, but I’ve run into a couple of issues. First, 125W per channel just isn’t enough when mixing raw signals like kick drums at decent volume. They clip too easily. Also, I’ve been wanting to use FIR filters for better crossover control, but the FA122s don’t support them.


To make things worse, one of the amps recently died after a short circuit on the PCB. Totally my fault, I mounted them a bit too sketchily into a metal 19" rack enclosure. So now I’m in the market for replacements.


The obvious upgrade path would be going for a Hypex FA253, bridging the 250W channels for the woofer and using the 100W channel for the tweeter. But honestly, I’m not a big fan of the plate amp format. I’d rather have a standalone unit or something rack-mountable. That said, if the FA253 is still the best option performance wise, I’ll just build a proper wooden enclosure and stick with Hypex.


I’ve also looked into the IMG Stage Line STA-1000D and STA-2000D. From what I’ve heard, they use Pascal Class D modules, which seem to be well regarded. My idea was to use the 1000D for the woofers and something smaller for the tweeters, or just go with the 2000D and run everything from that. But then I’d need to find a separate DSP.


That’s where I’m stuck. I’m having a hard time finding a reliable, good-sounding DSP unit that fits the bill. My budget is around €1200 ex VAT, including both amps and DSP. I’d prefer not to go the DIY route with something like a Raspberry Pi. I want something reliable and relatively easy to set up.


If anyone has recommendations for:

• Solid standalone DSPs with FIR support and decent DACs
• Rack-mount Class D amps that would be a good match
• Or general advice or experience with similar setups

I’d really appreciate your input.


Thanks in advance

 

[RickS]

Welcome to ASR!

Your DSP choices may be limited to affordability of amps. Have you looked at Audiophonics amps?

 

[mcdn]

You probably want 500W for the woofers (they are rated 280W RMS)

Nord (https://nordacoustics.co.uk/) have an NC122 and an NC502 - with the optional rack fronts those would be about EUR1200. If you ask nicely they should be able to do it in one case for slightly less. There are many Hypex packagers, Nord was just the one I checked first because I know they have a good reputation.

Then a MiniDSP 2x4HD is EUR200 direct from MiniDSP.

 

[mcdn]

The cheaper but less elegant option would be a pair of Fosi V3 mono amps for the woofers (each with 48V/10A power brick) and a Fosi stereo amp for the tweeters. That would have a bit less headroom in the bass but would be under EUR700. Again, other TPA3255 brands exist but Fosi is well tested here.

 

[RickS]

Minidsp 2x4 is good but a Flex is much better. Notably, if you want to use balanced i/o throughout. This leaves you with less to spend on amplification but the better DAC/dsp is worth it imo. Do not need overwhelming amplification in nearfield use. How big is your studio and what software are you using?

If you are producing music, the proposed solution could look much different than if just for music reproduction.

 

[mcdn]

Minidsp 2x4 is good but a Flex is much better. Notably, if you want to use balanced i/o throughout.

True about the balanced output options and other features like bluetooth and display, but if it's going to sit out of sight it's the same DSP chip and 10dB better SINAD (100 vs 110dB) for a lot more money.

 

[RickS]

True about the balanced output options and other features like bluetooth and display, but if it's going to sit out of sight it's the same DSP chip and 10dB better SINAD (100 vs 110dB)

Not going to parse further here until the OP states his application requirements first. I realized had jumped to solutions before having a full picture of the problem set. Not much point in talking minidsp diffs if he really needs an audio interface (upgrade) or something different entirely.

 

[Keith_W]

Welcome to ASR! You specifically mentioned that you want FIR. May I ask you why you want FIR?

Things like MiniDSP and nearly all hardware DSP units have FIR, but very few taps. At most 4096 taps per channel (for two channels) for some MiniDSP models. This means that the bin size is quite large, and they would be close to useless for bass equalisation. The heavy lifting in those DSP units is done with IIR biquads. IIR biquads have their own disadvantages, mostly that they distort phase.

This is not to say that mixed-phase filtering with MiniDSP is inadequate, it will probably be good enough for most people. But if you want FIR, you will need FIR with a lot of taps, at least 64k taps per channel if you want to use it for low frequencies. And FIR with a lot of taps means high computational requirements, which is why people use ARM chips and PC's.

So if you want FIR, it would be good to understand exactly why you want FIR because you have to pay a price. FIR has some advantages over mixed-phase or IIR, but whether those advantages apply to you, or whether you are willing to accept the price is another story.

If you want to understand the difference between IIR biquads and FIR taps, I suggest you read this thread.

 

[mcdn]

Not going to parse further here until the OP states his application requirements first. I realized had jumped to solutions before having a full picture of the problem set. Not much point in talking minidsp diffs if he really needs an audio interface (upgrade) or something different entirely.

It's to replace a pair of plate amps, so absent any other requirements a "back stage" set and forget solution seems appropriate.

 

[mcdn]

Worth noting that the MiniDSP can do FIR and IIR at the same time, so as @Keith_W says avoid using FIR in the bass, save it for the XO region and higher (if indeed you need it at all, his epic thread has all the detail you need)

 

[ppataki]

@TomSR Have you considered using a computer as a DSP? (running Jriver)
It will give you literally unlimited DSP capability
You can use a USB multichannel DAC to feed your power amps via balanced connection
I have been doing this for ages and I love it

 

[TomSR]

Welcome to ASR!

Your DSP choices may be limited to affordability of amps. Have you looked at Audiophonics amps?

I had not yet, taking a look as we speak! Any that you recommend looking at?

 

[TomSR]

You probably want 500W for the woofers (they are rated 280W RMS)

Nord (https://nordacoustics.co.uk/) have an NC122 and an NC502 - with the optional rack fronts those would be about EUR1200. If you ask nicely they should be able to do it in one case for slightly less. There are many Hypex packagers, Nord was just the one I checked first because I know they have a good reputation.

Then a MiniDSP 2x4HD is EUR200 direct from MiniDSP.

Would the MiniDSP 2x4HD be sufficient? I read some mixed reviews on here?

 

[TomSR]

Minidsp 2x4 is good but a Flex is much better. Notably, if you want to use balanced i/o throughout. This leaves you with less to spend on amplification but the better DAC/dsp is worth it imo. Do not need overwhelming amplification in nearfield use. How big is your studio and what software are you using?

If you are producing music, the proposed solution could look much different than if just for music reproduction.

Thanks for the input.

The studio is relatively small, but I’m mostly a live audio engineer, so these monitors are mainly used to prep mixes that will eventually be played on large PAs. I don’t need crazy SPL, but I’d like them to comfortably hit around 98 dBA Leq (5 min) with musical content, just to do short bursts of louder listening when needed. I sit about 1 meter from the speakers.

I’m using an EVO 16 audio interface, and ideally I’d feed the DSP via the Toslink output to keep the signal path fully digital. In some cases, I also run my mixer into the EVO via XLR or through Waves SoundGrid if I want to stay digital on that end too. This signal then ends up into reaper and going out to the monitors.

On top of that, I use the same computer for general tasks like listening to music while soldering or doing other work, so I’d like the system to be a bit flexible in terms of routing.

 

[TomSR]

True about the balanced output options and other features like bluetooth and display, but if it's going to sit out of sight it's the same DSP chip and 10dB better SINAD (100 vs 110dB) for a lot more money.

Very curious at this. Would the flex be worth it looking at it's DAC's etc?

 

[TomSR]

Welcome to ASR! You specifically mentioned that you want FIR. May I ask you why you want FIR?

Things like MiniDSP and nearly all hardware DSP units have FIR, but very few taps. At most 4096 taps per channel (for two channels) for some MiniDSP models. This means that the bin size is quite large, and they would be close to useless for bass equalisation. The heavy lifting in those DSP units is done with IIR biquads. IIR biquads have their own disadvantages, mostly that they distort phase.

This is not to say that mixed-phase filtering with MiniDSP is inadequate, it will probably be good enough for most people. But if you want FIR, you will need FIR with a lot of taps, at least 64k taps per channel if you want to use it for low frequencies. And FIR with a lot of taps means high computational requirements, which is why people use ARM chips and PC's.

So if you want FIR, it would be good to understand exactly why you want FIR because you have to pay a price. FIR has some advantages over mixed-phase or IIR, but whether those advantages apply to you, or whether you are willing to accept the price is another story.

If you want to understand the difference between IIR biquads and FIR taps, I suggest you read this thread.

I want to experiment with linear phase, mainly around the crossover frequency. I know it’s not strictly necessary, but I’m curious to hear the difference and see if it’s worth it for my setup.

Appreciate the info on tap counts and limitations, I hadn’t looked that deeply into it. I’ll read through the thread you linked!

 

[TomSR]

@TomSR Have you considered using a computer as a DSP? (running Jriver)
It will give you literally unlimited DSP capability
You can use a USB multichannel DAC to feed your power amps via balanced connection
I have been doing this for ages and I love it

I have considered it, only I was a bit worried about the stability of the whole setup. Once i have it set up I preferibly don't want to have to mess with it ever again so no drivers crashing or having the software forget the crossovers etc. How stable is this in your experience?

 

[TomSR]

Also to everyone, thanks for the warm welcome really appreciate it!

 

[Keith_W]

I want to experiment with linear phase, mainly around the crossover frequency. I know it’s not strictly necessary, but I’m curious to hear the difference and see if it’s worth it for my setup.

Appreciate the info on tap counts and limitations, I hadn’t looked that deeply into it. I’ll read through the thread you linked!

IMO there is a definite audible difference between linear phase and minimum phase. Minimum-phase creates time distortion and smears sound across time. Once this is removed, the result is exceptional clarity and attack.

But I suspect the others will pounce on me for saying so because I just made a subjective statement without a blind test to back it up on a fairly controversial topic. OK I admit I don't have a blind test, but I do have linphase and minphase filters which I designed to be as close as possible to each other. I can hear a difference, and i'll stake my reputation on it If you want to read about whether phase distortion is audible ... once again, ASR delivers. Read this thread (particularly the last 10 pages) and this thread (also the last 4-5 pages).

If you want linear phase, you're going to need a lot of taps.

Anyway, enjoy your reading and check back with any questions!

 

[TomSR]

Oh, one requirement I forgot to mention is that the latency can't be more than 20ms and preferably switchable to low latency mode with less phase correction so you'd be able to play instruments through your DAW.