miniDSP SHD - but without DAC, streamer, and Dirac…

[cany89]

Hi everyone!

I’m looking for a device that takes the XLR out of my preamp, split it to 4 XLR (2x for bookshelfs so XLR to power amp, 2x to active subs XLR or RCA). Then I need crossover, delay, and convolution filter for each output. So that I can set delay to bookshelfs if needed, and use impulse response file for both room correction and my studio monitors.

SHD got these features and many more, but I really don’t want to pay for all these unnecessary features. Anyone know a unit with only 2x4 + DSP features?

I got JBL 705i + 2x subs, and just getting 2x SVS 2000 to replace my crappy 8 inch subs. Using the subs crossovered around 180 hz and place them near JBLs. I will measure it once I got subs but I assume I will need some delay on 705s to match them with the subs. Any comment is welcome here as well…

Thanks!

 

[abdo123]

You need a computer with a 4-channel (or more) audio interface.

 

[abdo123]

Also 180Hz is preposterously high. I would not do anything higher than 100Hz or the -3dB point of the speaker sealed.

 

[abdo123]

Or maybe a digital MiniDSP flex plus two MiniDSP OpenDRC-DI plus two stereo DACs.

 

[JRS]

Also 180Hz is preposterously high. I would not do anything higher than 100Hz or the -3dB point of the speaker sealed.

Depends on how close to the mains they are, in which case they could be called bass bins. Just saying as I can run my system either as a 2 way, or as a 3 way with the XO at 300Hz. If I want to go loud and deep I run it as a three way. Sound as if the OP may be doing the same. I do it for the dynamics in addition to the bass extension. So maybe calling them subs isn't quite accurate?

 

[cany89]

@abdo123 thanks for the suggestions. Unfortunately my system is locked. I got macbook pro with RME Adi-2 as DAC + Pre. I’m 100% happy with the sound. I managed to get convolution filter for my 705 as well. Currently applying the filter with vst on pc out - before DAC.

Also 180Hz is preposterously high. I would not do anything higher than 100Hz or the -3dB point of the speaker sealed.

I measured the 705s and they got huge drop from around 200 Hz, than I added my subs and the FR evened out pretty nicely. (Subs start to drop around 60 Hz) So I have to do it to compensate the near field monitors…

You need a computer with a 4-channel (or more) audio interface.

One time I tried a very outrageous idea! I got 2x Adi-2 at home. So I tried to create an output on Mac with 2x out. One for 705, other for subs and apply filters to outputs. That didn’t worked out too. It would have if I had the Pro and use both XLR and RCA outs…

 

[abdo123]

Depends on how close to the mains they are, in which case they could be called bass bins. Just saying as I can run my system either as a 2 way, or as a 3 way with the XO at 300Hz. If I want to go loud and deep I run it as a three way. Sound as if the OP may be doing the same. I do it for the dynamics in addition to the bass extension. So maybe calling them subs isn't quite accurate?

the center of the two drivers have to be less than 20 inches apart for a 180Hz crossover, for a 300Hz crossover they have to be less than 12 inches apart for 300Hz.

Otherwise linearity of the direct sound will be effected, it is often refereed to as lobing.

 

[cany89]

Depends on how close to the mains they are, in which case they could be called bass bins. Just saying as I can run my system either as a 2 way, or as a 3 way with the XO at 300Hz. If I want to go loud and deep I run it as a three way. Sound as if the OP may be doing the same. I do it for the dynamics in addition to the bass extension. So maybe calling them subs isn't quite accurate?

That is actually correct. It sounds like 3 way. But I want to add crossover to my mains. Either via PEQ or just xover function…

 

[abdo123]

Unfortunately my system is locked.

Then so are your options sorry .

you either need some sort of computer to do convolution (like you're doing with the vst plugin) or digitize the outputs of the RME DAC.

 

[cany89]

the center of the two drivers have to be less than 20 inches apart for a 180Hz crossover

This is OK with current setup but with cabins like SVS 2000, I will have to place the 705s on top of subs to match this distance. Will vibration hurt the 705s?

 

[cany89]

Then so are your options sorry .

you either need some sort of computer to do convolution (like you're doing with the vst plugin) or digitize the outputs of the RME DAC.

That’s bummer! I will try 2x Adi-2 once more than.

What do you think about delay issue? Does 12-13 inch subs need delay on mains to match he phase?

 

[abdo123]

That’s bummer! I will try 2x Adi-2 once more than.

What do you think about delay issue? Does 12-13 inch subs need delay on mains to match he phase?

there will be no issues using two DACs once the clock control is not in the hands of the DACs (use the SPDIF inputs somehow instead of USB).

you don't need delays if the drivers are exactly on top of each other.

but this is really a messy way to go about things, have you considered a good old analogue passive crossover?

 

[DWPress]

You say you're using a Mac so this time around try creating an Aggregate Device in Audio Midi Setup to combine your 2X Adi-2. This will present you with 4 output channels as 1 device. Not sure of the other functionality of Adi-2 for onboard processing but if your subs are active and have XO controls presumably you'll only need 2 channels of convolution.

Check the link in my signature for other possible ways of doing it on a Mac.

 

[cany89]

but this is really a messy way to go about things, have you considered a good old analogue passive crossover?

I know! It’s all because I’m trying to use studio monitors without their dsp or amp pair that applies the filters…

No need for delay is good news!

 

[cany89]

Thanks @DWPress , I was reluctant to sacrifice my second Adi to this but I will try again to see if it works.

 

[JRS]

the center of the two drivers have to be less than 20 inches apart for a 180Hz crossover, for a 300Hz crossover they have to be less than 12 inches apart for 300Hz.

Otherwise linearity of the direct sound will be effected, it is often refereed to as lobing.

Are those center to center or edge to edge dimensions? I'm curious because if so, not just mine but countless speakers would violate the 1/4 wavelength rule of thumb? I've wondered about a null, but it's a bitch to measure accurately at that freq--at least quasi-anechoically.

 

[abdo123]

Are those center to center or edge to edge dimensions? I'm curious because if so, not just mine but countless speakers would violate the 1/4 wavelength rule of thumb? I've wondered about a null, but it's a bitch to measure accurately at that freq--at least quasi-anechoically.

Countless speakers do violate it and show cancelations or lobing in their vertical directivity. It’s center to center.

 

[JRS]

Ok, thanks for clarifying that. One quick related question: do waveguides or an MTM do anything to mitigate the difference? See, my trouble is that I have never seen a depiction as to how waves combine--on the one had I see them colliding in space away from the baffle when the wave fronts interact, but I also see it as a case of 2 near point sources of pressure doing their thing and modeling the output as a single bigger sound source with a mouth that is larger than the space the drivers occupy with these two independent elements contributing to output, as they rotate in phase about one another versus frequency.

I gather that the infinite point source view is more accurate. But then I wonder about larger transducers like electrostatics or even the 7 x 1" ribbon tweeters I use. Or my 15' woofers--surely these can't be modelled as points Do I take the center point of those? These are things I really don't have a firm handle on, so I appreciate your helping me out here. It seems a bit like classroom physics versus the real world where things get squishy. When is a point source no longer a point source?

 

[cany89]

@JRS Directivity starts after 100 cycle. So if your 15’ woofers are crossed below that, I don’t think you need to worry about this. I’m just guessing here btw

 

[abdo123]

When is a point source no longer a point source?

This is a very good question, i'm not an academically trained expert either btw but from what i gathered is that a point source and constant broadband directivity are often refereed to as one and the same.

Constant broadband directivity has been achieved using horns, a very good example of this is unity horns by Danley Sound labs, you have 3 different types of drivers in the horn but they all blend nicely both vertically and horizontally ressembing a point source.

Genelecs the ones do a very good job of resembling a point source with their coaxials, however they violate the distance rule i mentioned earlier VERY slightly.

the other way is by lying the multiple sources in a way that resembles a sphere. Arcs work too if you're interested in constant broadband directivity in one dimension (as in vertical OR horizontal).

For the case of the later where you have multiple sources working simultaneously, the point source behavior stops when the distance between the center of the drivers is more than ~75% of wavelength. for example for linearity to 10000Hz the distances between the centers of the drivers need to be 1 inch or less, that means a 0.95inch tweeters with 1mm of distance between them.