Bass Bins + Crossover for March Sointuva to Scanspeak Revelator13"

[concorde1]

I have 2x March Sointuva WG and 2x Scanspeak Revelator 13" drivers and a high wattage power amp (DIY Neurochrome).

Originally I was going to build 2 sealed subs ( https://www.audiosciencereview.com/forum/index.php?threads/scanspeak-revelator-13-subs.47653/ )

Now I wish to build 2 bass bins to go directly underneath the Sointuva's - so that in essence I have 3-way speakers.

And design and build the crossover(s) to go between my stereo amp, Sointuva's, and the bass bins.

I've been advised VituixCAD is useful for the crossover design.

--

I had been going to build 75 Litre sealed subs with these Scanspeak drivers.

How do I figure out the volume / dimensions for these bass bins? WinISD?

How do I design the crossover (I have been advised 250 Hz would be a suitable crossover point)?

How do I volume-match the speakers to the bass bins? (Given different impedance and sensitivity.)

I have worked a little with electronics and personally know an expert in the field who I can work with if necessary.
I have some tools for woodworking - but I would probably get a joiner to cut the baltic birch (inc. holes for drivers).
Funny question: does the input plate (where speaker wire goes in to bass bins) need a hole cut? Or does it just sit on the outside and drill holes just for the wires themselves?

Many thanks

 

[suttondesign]

Hi. Those are awesome drivers. It's so much easier to use this in a sealed enclosure and use a Linkwitz transform to boost down low at the expense of higher frequencies. Use the range of internal volumes recommended by Scan-Speak (2.3 cu. ft. (67L) for a -3db of 36hz), or Madisound (1.5 cu. ft. (42.5L) for a -3db of 45 hz). Anything in that range is just fine -- that's the beauty of building a sealed sub and just using EQ and amplifier power to reach your desired goal. For the larger box, you can use less power and less boost at 20hz; for the smaller box, you'd need quite a lot of power. In your setup, since those are smallish main speakers, even a 2.5 liter taller enclosure would be awesome since it drops the -3db point even lower. When I used BassBox to model my slightly smaller Scan-Speaks, tweaking the box size among the values above didn't make all that much difference since I was going to do a Linkwitz transform anyway.

For the crossover, just use a MiniDSP plate amp or two (these can run bridged mono), whether mounted in the box or, as I've done, mounted in the MiniDSP plate amp box well away from the subs. This allows you to tweak to your heart's content because the MiniDSP software is so flexible.

Scan-Speak's diagram shows that woofer operating beautifully up to 300hz, but you've got speakers that are just fine down to 100hz or even 80hz. The 80hz option lets you simplify the integration if your Sointuvas are sitting on the subs since there shouldn't be any phase shift/delay to speak of, and then the subs are just omni and not readily located by ear. And then you can really focus your amplifier power for the subs where you really need it, for boosting 20hz. That gives you the benefit of the well-designed Sointuva speaker for most of its operating range.

FWIW, I know it's heresy at ASR, but I've used REW over the years to address reinforcing modes but then tweaked by ear using recordings I know very well that have lots of energy at various points from 50hz to 120hz, along with simple step tones from 20hz to 100hz. I've dialed in my 2 dual-opposed subs that way and am very happy -- an incredibly deep floor below my 45hz bottom for my mains. I'm basically running two sealed, potent subs from 20hz-45hz, and I've got power to spare. You can just find your happy place somewhere around 60-80hz, I think, and go to town.

 

[concorde1]

even a 2.5 liter taller enclosure would be awesome since it drops the -3db point even lower.

For the crossover, just use a MiniDSP plate amp or two (these can run bridged mono), whether mounted in the box or, as I've done, mounted in the MiniDSP plate amp box well away from the subs. This allows you to tweak to your heart's content because the MiniDSP software is so flexible.

Thanks for your advice.

I will go for 2.5 cu. ft.

However - what if I want to power the bass bins from my speaker amp?

Since I have such a powerful amp, it may as well drive the bass units as well as speakers. (Instead of getting plate amps.)

Is there a product, or would I need to design my own crossover between Scanspeak and 6.5Purifi?

 

[suttondesign]

Sure. Get that minidsp flex or 2x4hd that are for sale here on asr. The flex is better. The 2x4hd is a steal. It’s super easy to design detailed crossovers with these.

 

[concorde1]

Sure. Get that minidsp flex

Huh - the Flex can input a speaker level signal and split it!?

If this is true . . . is there anything that thing can't do!?

I had been going to use a Flex as a USB DAC with DSP - but this is a new thing I didn't know it could do.

 

[MAB]

Huh - the Flex can input a speaker level signal and split it!?

If this is true . . . is there anything that thing can't do!?

I had been going to use a Flex as a USB DAC with DSP - but this is a new thing I didn't know it could do.

You can't split the amplified signal between mains and subs the MiniDSP. What you describe is a passive crossover.
To implement a passive crossover at subwoofer frequencies requires components in the 10's of mH and 100's of uF. You'll spend nearly much on huge passive components just to build a first or second order crossover as it would cost to implement DSP solution with amps. And would omit the many benefits of DSP, with no upside.

 

[Sokel]

You can't split the amplified signal between mains and subs the MiniDSP. What you describe is a passive crossover.
To implement a passive crossover at subwoofer frequencies requires components in the 10's of mH and 100's of uF. You'll spend nearly much on huge passive components just to build a first or second order crossover as it would cost to implement DSP solution with amps. And would omit the many benefits of DSP, with no upside.

I think there's a misunderstanding here although the title is accurate.
OP is not searching for sub build and integration but rather a W371 bass (not sub) style solution (without the cardioid and passive of course)

A normal 3rd supplemental way as in any other 3-way speaker x-overed at 200-250Hz,right underneath the mains.The drivers are nice and can take it with ease.
It can be active of course but as he wants to avoid amps,cables,DSP boxes and the usual clatter it can be passive just as fine and it won't need enormous inductors x-overed up there.

 

[MAB]

I think there's a misunderstanding here although the title is accurate.
OP is not searching for sub build and integration but rather a W371 bass (not sub) style solution (without the cardioid and passive of course)

A normal 3rd supplemental way as in any other 3-way speaker x-overed at 200-250Hz,right underneath the mains.The drivers are nice and can take it with ease.
It can be active of course but as he wants to avoid amps,cables,DSP boxes and the usual clatter it can be passive just as fine and it won't need enormous inductors x-overed up there.

Yes, thanks. 250 - 350Hz is classic 3-way bass crossover.
Probably less than $20 per crossover. I guess twice that for second order. I never get it right the first time, adjust frequency and slopes, so probably more.

 

[Sokel]

Yes, thanks. 250 - 350Hz is classic 3-way bass crossover.
Probably less than $20 per crossover. I guess twice that for second order. I never get it right the first time, adjust frequency and slopes, so probably more.

These are some of the nicest drives out there for bass,both of them cost more than 1000 euro a pair.
Cabinets will also have a cost,depending the looks,built,etc.I think it's fair for something at 100-200 euros for x-overs comparing with the rest of the built.

 

[MAB]

These are some of the nicest drives out there for bass,both of them cost more than 1000 euro a pair.
Cabinets will also have a cost,depending the looks,built,etc.I think it's fair for something at 100-200 euros for x-overs comparing with the rest of the built.

Yeah. The drivers are luxurious enough to justify a DSP plate amp I think. Or outboard DSP plus a second amp.
You could possibly do this passive. The bass driver is about 7dB more sensitive than the March Audio mains, I guess you size the cabinet to try to match the levels? Then you are stuck with that cabinet response plus in-room response, for which DSP would be incredibly useful.
Passive 3-way speakers really become incredibly difficult with random drivers. Active allows disparate drivers to be integrated without all of the compromises.
So yeah, by the time I got that bass driver integrated, I would probably try half a dozen different crossover configs. And need an inventory of several hundred dollars or more in passives to allow experimentation. Plus perhaps go though a couple prototype cabinets in attempt to get levels matched. And allow for all the time passive crossovers take, including for comparison testing, since I never built a successful speaker without doing a ton of testing, which is actually the fun part. With DSP testing becomes more fun, level matching is now done with gain.
Also, not many people are actually comfortable with all of the variables in a passive crossover. OP is asking basic driver and crossover integration questions for a project that is has at least one significant headwind: integrate two high quality woofers with two fantastic mains with different sensitivities.

How do I volume-match the speakers to the bass bins? (Given different impedance and sensitivity.)

Matching a woofer with higher efficiency than your mains is not straightforward with passive, you are not going to just pad it down. Perhaps make the cabinet small so that the system efficiency is matched between subs and mains. Of course this alignment would benefit from DSP to obtain.

Making a three-way passive speaker is best done starting with driver selection. Taking drivers in-hand and working backwards to fit a crossover isn't easy. Best and most expensive drivers are not a solution. DSP fixes much of this, your plan becomes much more likely to be successful, and even fun. I emphasize you need a large collection of passive components for DIY speakers to actually be successful.

Do you have a measurement mic and stand?

 

[concorde1]

Thanks for the great discussion.

My only reason for passive crossover approach was so as to not waste my speaker amp's potential on just my bookshelf speakers (which only handle maybe 1/2 the power available).

However, you've successfully dissuaded me from this.

I'll go back to original plan: MiniDSP Flex (USB to computer); outboard stereo amp for subs; and build 2x sealed subs of 2.5 cu. ft. (Using Linkwitz Transform EQ via Flex.)

People are still welcome to convince me passive crossover approach might not be so bad.

Do you have a measurement mic and stand?

Yes - MiniDSP UMIK-1 with calibration files from Cross-Spectrum Labs

---

While we're here, I have a couple unrelated beginner-ish questions.

1. Does the input plate (where speaker wire goes in to subs) need a hole cut for the whole plate area? Or does it just sit on the outside of sub cabinet and drill holes just for the wires themselves?

2. Suppose I had the 2 subs set up working. Suppose at some arbitrary volume setting on the MiniDSP Flex, the speakers and subs are volume matched (thanks to the PEQ via DSP). Is sensitivity non-linear? In other words, if I made the Flex volume higher, could I begin to see deviation between speakers and sub volume?

---

P.S. Reason for Flex instead of plate amps w/ DSP is, I want DSP all in one place (the Flex). And one volume control for subs/speakers. It sounds like a mess to have 2 plate amps with DSP, and simultaneously running Equalizer APO for the loudspeakers part of the frequency response. Another reason - the Flex will allow me to EQ despite using ASIO in Cubase.

 

[Sokel]

Thanks for the great discussion.

My only reason for passive crossover approach was so as to not waste my speaker amp's potential on just my bookshelf speakers (which only handle maybe 1/2 the power available).

However, you've successfully dissuaded me from this.

I'll go back to original plan: MiniDSP Flex (USB to computer); outboard stereo amp for subs; and build 2x sealed subs of 2.5 cu. ft. (Using Linkwitz Transform EQ via Flex.)

People are still welcome to convince me passive crossover approach might not be so bad.


Yes - MiniDSP UMIK-1 with calibration files from Cross-Spectrum Labs

---

While we're here, I have a couple unrelated beginner-ish questions.

1. Does the input plate (where speaker wire goes in to subs) need a hole cut for the whole plate area? Or does it just sit on the outside of sub cabinet and drill holes just for the wires themselves?

2. Suppose I had the 2 subs set up working. Suppose at some arbitrary volume setting on the MiniDSP Flex, the speakers and subs are volume matched (thanks to the PEQ via DSP). Is sensitivity non-linear? In other words, if I made the Flex volume higher, could I begin to see deviation between speakers and sub volume?

---

P.S. Reason for Flex instead of plate amps w/ DSP is, I want DSP all in one place (the Flex). And one volume control for subs/speakers. It sounds like a mess to have 2 plate amps with DSP, and simultaneously running Equalizer APO for the loudspeakers part of the frequency response. Another reason - the Flex will allow me to EQ despite using ASIO in Cubase.

If you go with Flex you may consider getting couple of nicer mono amps instead of plate ones since half of usual functionality of these amps is about controls or DSP,etc.
This way you may get something more powerful with the same money,it will be off the cabinets (so better conditions for both the amp and the box+driver) and the complexity to built an enclosure-inside-an enclosure (cause that's the right way to house a plate amp) is gone.

You'll have all the benefits of active amplification and the flexibility to play with whatever amp gets in your hands.

 

[MAB]

Thanks for the great discussion.

My only reason for passive crossover approach was so as to not waste my speaker amp's potential on just my bookshelf speakers (which only handle maybe 1/2 the power available).

However, you've successfully dissuaded me from this.

I'll go back to original plan: MiniDSP Flex (USB to computer); outboard stereo amp for subs; and build 2x sealed subs of 2.5 cu. ft. (Using Linkwitz Transform EQ via Flex.)

People are still welcome to convince me passive crossover approach might not be so bad.


Yes - MiniDSP UMIK-1 with calibration files from Cross-Spectrum Labs

---

While we're here, I have a couple unrelated beginner-ish questions.

1. Does the input plate (where speaker wire goes in to subs) need a hole cut for the whole plate area? Or does it just sit on the outside of sub cabinet and drill holes just for the wires themselves?

2. Suppose I had the 2 subs set up working. Suppose at some arbitrary volume setting on the MiniDSP Flex, the speakers and subs are volume matched (thanks to the PEQ via DSP). Is sensitivity non-linear? In other words, if I made the Flex volume higher, could I begin to see deviation between speakers and sub volume?

---

P.S. Reason for Flex instead of plate amps w/ DSP is, I want DSP all in one place (the Flex). And one volume control for subs/speakers. It sounds like a mess to have 2 plate amps with DSP, and simultaneously running Equalizer APO for the loudspeakers part of the frequency response. Another reason - the Flex will allow me to EQ despite using ASIO in Cubase.

I agree with you appraoch on a Flex instead of a plate amp. I've built several multi-amped systems with Flex. I've have the SHD as well that I use daily. I'm a fan. Wish they had stiffer competition.

I don't know how to have too much amp. I use Bryston 7B-ST all the time. I have PuriFi and Hypex amps too that are overspec'ed on power, I got them for the low noise performance with high efficiency drivers. I also have a Niles 12-channel install amp I keep around for getting systems up and running, even if I could likely live with it forever. And it does seem to be lasting forever. I got it used for $140 .

I still use some passives in my active speaker builds. But now always in combo with active. I have analog active crossovers, but rarely use them anymore.
I often use a Linkwitz transform on sealed woofer instead of a port or passive radiator. I honestly don't miss building cabinets with passive radiators, or even ports. I built a pair of JBL M2 Clones, omitted the fancy JBL ports, which cost a mint to 3D print, and used sealed with transform, and it is fantastic. I need to EQ the bass in my room anyway.

I'm not sure I understand about the input plate. Do you mean this?

Most of these are surface-mount, require a specific size hole to be drilled, routed, or sawn. Has a foam compression gasket. I'm not picky about terminal style, so long as they are reasonably resistant to accidental shorting and/or disconnection. Troels Gravesen has some practical ideas about speaker terminals.

Tips and ideas

I think I understand your question about linearity. All drivers exhibit compression, both from non-linearities in the motor, and temperature. Systems with more power compression on one driver vs. the others should change FR with volume. That being said, my experience is the effect is subtle at worst. Regarding the MiniDSP gain implementation, the master volume will linearly and proportionally control the gain of each driver's channel, and this is the correct way to implement multi-amplification for your purpose.

Good luck.