Need Help with Building OB Speakers with MiniDSP

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taipan1013

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Need Help with Building OB Speakers with MiniDSP
« on: 27 Feb 2022, 03:20 am »
I need site members help in building an open baffle speaker with 2 Eminence Beta 15a woofers (45-3.7k hz), Tang Band W1808 (45-20K hz) and MiniDSP 2x4 HD active Crossover.  I have the following questions:

- What would you use as the MiniDSP crossover setting for the Beta 15a woofers?
- What would you use as the MiniDSP crossover setting for the Tang Band W1808
- Any additional comments in setting up the MiniDSP would be greatly appreciated (first time using an active crossover).
- Would you wire the 2 woofers in series or parallel?
- I have two OddWatt Mono Tube Amps (45 watts each) and Hafler 200 solid state stereo amp.  I was planning to use the tube amps for Tang Band speakers and Halter for woofers.  Is this a good configuration.

Please let me know if you have any additional suggestions.  Thank you very much for considering to help.

Greg

uncola

Re: Need Help with Building OB Speakers with MiniDSP
« Reply #1 on: 27 Feb 2022, 09:21 am »
Good luck with your speaker.  That design is what I'd build if I had the room

DannyBadorine

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Re: Need Help with Building OB Speakers with MiniDSP
« Reply #2 on: 27 Feb 2022, 02:59 pm »
This is a difficult question to answer without knowing the size and shape of the enclosure that you will put them in.
I would wire the Eminence woofers in parallel. I would shoot to cross them over between 200Hz and 500Hz with the Tang Bang going from that area all the way up to 20KHz.
You will get better results if you design the enclosure based on the driver characteristics then put the speakers in the enclosure and test their response.  Once you see how they act in the box you can design the crossover better.  The advantage of having DSP is that you can bi-amp them and test several different crossover possibilities before you decide on the final crossover.
Also, using two completely different amplifiers on the drivers is a potential mismatch.  When bi-amping, I think it is best to use the same amplifier for each channel so that you have some uniformity on how the speakers will be driven.

Woodsage

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Re: Need Help with Building OB Speakers with MiniDSP
« Reply #3 on: 27 Feb 2022, 03:10 pm »
I don’t see much reason to limit the TB, just let it roll off naturally on the low end. Measure how low it has good output then bring the woofers up to meet it. I’ve used the TB in a small open box and it didn’t go very low so I’m guessing your woofers will end up coming in at 125-200 Hz depending on your baffle size.

Good luck with your build.

Poultrygeist

Re: Need Help with Building OB Speakers with MiniDSP
« Reply #4 on: 11 Mar 2022, 02:37 pm »
It may or may not be a problem in your case but my SET amps lost much of their magic when paired with an active crossover. Actives can often add their own sonic signature to the mix. I'd try the TB's running full range with nothing in the signal path while using the mini DSP only on the separately powered woofers.

andyr

Re: Need Help with Building OB Speakers with MiniDSP
« Reply #5 on: 5 May 2022, 02:10 am »
It may or may not be a problem in your case but my SET amps lost much of their magic when paired with an active crossover. Actives can often add their own sonic signature to the mix. I'd try the TB's running full range with nothing in the signal path while using the mini DSP only on the separately powered woofers.

That seems bizarre to me ... in that with an active XO, the amps come after it in the signal chain.  As there's nothing between the SET amp and the driver it's powering ... it's hard to see how the SQ of the SET can've been altered.

However, with a passive XO - which sits between the amp and the drivers ... I could understand how the quality of the SET magic could be altered.

Andy

Poultrygeist

Re: Need Help with Building OB Speakers with MiniDSP
« Reply #6 on: 5 May 2022, 09:28 am »
When the active crossover divides the frequency before amplification it can impart its own sonic signature.

Do you find it bizarre that a preamp can add its sonic signature although it also occurs upstream of the amplifier?

MarvinTheMartian

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Re: Need Help with Building OB Speakers with MiniDSP
« Reply #7 on: 5 May 2022, 09:40 pm »
The MiniDSP 2x4 HD would be the weak link in your signal path , its technical performance is … perfectly adequate.
Sure the 2x4HD  can do a full stereo 2-way crossover, 
but I don’t think you are going to be sonically satisfied with it in your  TB signal path.
The 2x4HD is fine for the beta woofer low pass signal path, it just doesn’t shine on the top end.

So three DSP options
- Try the 2x4HD 2-way crossover and see if you are satisfied .
- Previously suggested  2x4HD lowpass only to the Beta’s  and run the TB full range,.
- Upgrade to newest MiniDSP Flex, now the 2-way crossover path becomes more promising but at twice the price.

Amirm gave the Flex a thumbs up  here …
https://www.audiosciencereview.com/forum/index.php?threads/minidsp-flex-review-audio-dsp.30804/

Your choice
Either way, you had better be completely intimate with the REW measurement flow.
Shawn

andyr

Re: Need Help with Building OB Speakers with MiniDSP
« Reply #8 on: 5 May 2022, 11:36 pm »
Do you find it bizarre that a preamp can add its sonic signature although it also occurs upstream of the amplifier?

Good point - no I don't (find it bizarre).

When the active crossover divides the frequency before amplification it can impart its own sonic signature.

Then so will a passive XO, surely?

Andy

Tyson

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Re: Need Help with Building OB Speakers with MiniDSP
« Reply #9 on: 5 May 2022, 11:38 pm »
Everything imparts it's sonic signature.  Regardless of where it occurs in the chain.

Early B.

Re: Need Help with Building OB Speakers with MiniDSP
« Reply #10 on: 6 May 2022, 02:11 am »
Everything imparts it's sonic signature.  Regardless of where it occurs in the chain.

Even your wall outlet has a sonic signature. So does your room.

kd4ylq

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Re: Need Help with Building OB Speakers with MiniDSP
« Reply #11 on: 11 Oct 2022, 02:02 pm »
Concerning Reply #7 from MarvinMartian "you had better be completely intimate with the REW measurement flow". OK, since I want to use the MiniDSP as well, what would you recommend reading and working with to be completely intimate with the REW measurement flow? Any advice from others to helpo me get going with DSP based active crossovers? Thanks much!

richidoo

Re: Need Help with Building OB Speakers with MiniDSP
« Reply #12 on: 11 Oct 2022, 03:34 pm »
I need site members help in building an open baffle speaker with 2 Eminence Beta 15a woofers (45-3.7k hz), Tang Band W1808 (45-20K hz) and MiniDSP 2x4 HD active Crossover.  I have the following questions:

Beta 15 has 2" voice coil (weak for 15" cone) and Q .58 which is good for passive dipole when EQ is not available, but gives up too much cone control and tonal detail when active EQ is available to boost the bass. High Q allows more low bass but has less detail.

Kappa 15A has 3" voice coil, and Q .32. It will have much better cone control and power rating, and better transient response. If there is too little bass you can easily boost the bass electronically with your active crossover.

Quote
- What would you use as the MiniDSP crossover setting for the Beta 15a woofers?
Beta15 is poorly damped which will blur the detail at all frequencies, but more noticeable in comparison to 1808 as you move higher into midrange band, so you would want to roll it off as steeply as possible and as low as possible to avoid smearing the midrange from the very detailed 1808.

Delta 15 is much better damped electrically and mechanically, so it will blend with the detailed 1808 up into the midrange so you can run it a little higher to get better integration.

In either case you must adjust the crossover freq by ear, because it affects the meatiness and fullness of the tone through the low midrange and upper bass. Especially if the two drivers are very different tonally, like 1808 and Beta. If drivers have more similar tonal color then it is less critical. XO should be steep, probably 24dB/octave, and probably 150-250Hz.

My crossover freq with 2x12" bass drivers Q.7 and one 5" full range driver was 175Hz. If you like a fuller sound, richer bass then XO freq might be higher so woofers play higher. If you like clean detailed bass then lower so 1808 plays lower. But 1808 being smaller cone doesn't grip the air at lower freqs, so it will slip and lose detail and it can't play loud and low. So the louder bass you need the higher the XO must be. Voicing a speaker involves many compromises.

Quote
- What would you use as the MiniDSP crossover setting for the Tang Band W1808

Above 150Hz, if possible. As low as 100Hz if necessary. Below that it will blur bass detail (in comparison to dual 15" cones) due to low acoustic impedance. The lower it is forced to play the more midrange distortion you get from the low freq cone movement. So getting out of the bass range is ideal. But the bass drivers must be able to blend with it through the XO band and your woofer candidates will have trouble playing cleanly up past 300Hz. Beta won't play super clean at any freq, but it will play low and loud with blur without any external EQ boost.

Quote
- Any additional comments in setting up the MiniDSP would be greatly appreciated (first time using an active crossover)

Trust your ears. The speaker system is intended to serve your brain, through your ears. It is not intended to serve your ego obsession with scientific validation through measurement.

Make small changes slowly. Listen to what each change does so you can learn what is happening, not just reacting emotionally to instant AB comparisons. Allow time for the changes to settle in, and your brain to adjust and assimmilate the changes. At first, yesm, the changes will be fast and large until to get a basic workable system. Then listen a lot between changes. Take notes about what sounds good and what sounds bad across lots of different music. Don't use the same test tracks. Allow your intuition and imagination to assist the tuning process, allow new music to come in.

Have a reference speaker that you like, which makes most music sound pretty good to you. It may be your car, or other hifi system, or home theater, whatever. Compare it to your dipole speaker voicing.

Quote
- Would you wire the 2 woofers in series or parallel?

Either will work, but you have to try each to see which sounds better tonally.
Beta and Kapa have higher sensitivity than 1808, so you can wire them in series for net 16 ohm load and retain the specified sensitivity rating for one speaker. In other words, 2 Kappas in series is 100dB sensitivity at 16 ohms. This would be good if you were using tube amps on the  bass drivers.
But you might find that your ampliifer prefers and sounds better playing at higher current, so a parallel load would be better. 2 Kappas in parallel is 4 ohm nominal load, with 106dB sensitivity, so you would have to attenuate the woofer signal in your miniDSP mix to match the SPL level of your 1808. Easy to do.

Quote
- I have two OddWatt Mono Tube Amps (45 watts each) and Hafler 200 solid state stereo amp.  I was planning to use the tube amps for Tang Band speakers and Halter for woofers.  Is this a good configuration.

Try both. With Kappas in series the tubes might be nice in the bass, especially if the Hafler sounds better than tubes on the 1808.
The different amplifiers will have different voltage gain which adds another variable to compensate in your miniDSP level mix.
You'll want to generate a few different profiles in DSP so you can swap gears around for comparison without the delay of manually adjusting all the gains. 
If you like to play very loudly, and like bass slam on popular genre music then you might prefer the superior current sourcing advantage of SS amp on the bass drivers. Try both and see. Give each adequate time to listen to assortment of different music to learn the pros and cons of each. Don't just play Led Zep and decide that's it! Let you brain adjust to both so the pros and cons are obvious and clear. Then you can decide and make fwd progress.

Quote
Please let me know if you have any additional suggestions.  Thank you very much for considering to help.

A successful speaker project is half building it and half tuning it. It takes time. The real work is mental, in design stage and in voicing it. Allow 6 months before you feel comfortable to stop messing around. But it should sound pretty close after 1 month of diligent listening with minor constructive tweaking with firm hand on the tiller according to your notes.

Go ahead and measure if you want, it can speed up the process dramatically especially in the beginning, setting up XO and levels. But don't let measurements make final artistic decisions. You are not professional mastering engineer, it doesn't have to be flat. Make it sound good and feel good or else you'll never use it.

Get the Kappas or even a different brand of woofer to maximize the transient response in the bass band. Choosing active XO/EQ enables a higher level of sound quality with dipole bass, so don't piss that away on high Q woofers which the active XO cannot control. EQ can easily raise Q (force woofer to play lower and louder, but EQ cannot lower Q (force it to play more detail and bass slam.)

Any "full range driver" will beam the treble frequencies. This is why tweeters are small, to make them spray the highs more widely. 1808 uses a wizzer cone to simulate a smaller tweeter, but it still beams very strongly. You don't want to be in that beam. Your ending FR will be rolled off. That's OK. Musical treble goes up to 8-10kHz. Audiophile fireworks treble goes higher, but you're not building an audiophile hifi speaker by design. If you listen outside the beam, them EQ to flat 20kHz then the reflected treble will be too hot. Your best sounding compromise will be measured rolled off treble. Trust your ears!

Since the 1808 requires listening off axis, you can toe it to the side or you can tilt it back to aim the axis away from you. Tilting it back has a couple advantages. The beam lights up the ceiling more, so you get more height image. The beam is always shot over all the listeners who are seated at the target listening area. Tilting baffle back aligns the 1808 acoustic center with the woofers' acoustic center for flatter phase less blurring through the crossover zone. Meaning the sound from 1808 and sound from woofers arrive at your ear at the same time, so they don't blur each other by slight delay caused by different travel distance. At these lower frequencies in the bass crossover where they are both playing same notes together, a couple inches of phase distortion is not a big deal, especially with a slow woofer like beta, but with kappa it will be more audible so just depends on the results you're shooting for and how detailed you want to make your design.

An alternative for dipole bass that is popular with AudioCircle members is to use servo subs offered by GR Research. They are high Q driver that allows playing low and loud with low power, but the Q is electronically lowered by a feedback sensor on the voice coil. So the driver cone is forced by the special servo amplifier in feedback to follow the (EQ'd) input signal accurately. It is functionally the same as using a well behaved, self-damping driver with low Q, and boosting the amplifier input signal to play low and loud with EQ.  If you already have the amp DSP and drivers then stay the course.

MarvintheMartian's advice about the sound quality of inexpensive electronic crossover appliances is worth considering. The cheap digital XOs are tempting, and probably worthwhile for your first step, but if you are already "ruined" by high end sound quality then you will want to move on to something better. Passive XO is an option, but then your forced into high Q woofer. Active analog XO filters can have excellent high end sound quality, especially if you know the quirks of the buffer amplifiers you are using. You can use the miniDSP to determine what functions you ant to apply to your input signal, then you can design analog filters to perform those functions to get the high end sound quality. Or you can buy a digital XO that has high end sound quality like DEQX. Or you can enjoy miniDSP and not perceive any deficiency. Give it a try, might be plenty good enough for 1808 even if it's not good enough for a audiophile dome tweeter.

360audio

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Re: Need Help with Building OB Speakers with MiniDSP
« Reply #13 on: 13 Dec 2022, 10:19 pm »
I know this thread might have gone a bit cold, but I thought I just throw in a word of advise from someone who learned the hard way.

Do consider adding a capacitor for protection between the tweeters and their amps whilst tinkering. If something unexpected happens you could save your tweeters from blowing up.
There are plenty of online crossover calculators for finding a value that won't interfere with your active crossover points. I've used a couple of 20µF when trialling active crossover points for 2000Hz and up. I bought a set of various values of cost effective bipolar MKT metallised polyester film capacitors for when elaborating.

Cheers,

Mattias

richidoo

Re: Need Help with Building OB Speakers with MiniDSP
« Reply #14 on: 13 Dec 2022, 11:52 pm »
Do consider adding a capacitor for protection between the tweeters and their amps whilst tinkering. If something unexpected happens you could save your tweeters from blowing up.

Good advice! An alternative solution without the signal coloring from a capacitor is this

DannyBadorine

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Re: Need Help with Building OB Speakers with MiniDSP
« Reply #15 on: 14 Dec 2022, 02:07 pm »
Good advice! An alternative solution without the signal coloring from a capacitor is this

This is good advice, but remember that the capacitor will affect the phase and frequency response on your measurements.

NeilBlanchard

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Re: Need Help with Building OB Speakers with MiniDSP
« Reply #16 on: 14 Dec 2022, 02:41 pm »
Using the miniDSP 2x4 HD to design a crossover - is the best thing to do with a miniDSP 2x4 HD, in my opinion. I have done this several times - and some key things to know are that you can link two channels in the 2x4 HD, so that the drivers in the left and right speakers will always be set the same. Label the outputs with tape and marker, to eliminate confusion.

I would use the Tang Band as low into the bass as they can comfortably go. I would use 1st order slopes, so that if/when you go to building the equivalent analog crossover, it will be simpler and less expensive. On the woofers, you may want 2nd order to better slope off any output to minimize duplicate sources in the critical midrange.

As for the frequencies to use - this is exactly why using the 2x4 HD is so useful - you can experiment in seconds. You can set up 4 (up to) variations, and switch between them with the remote, and hear real time how they sound. This is the whole point/benefit of doing this!

Edit: the Tang Band drivers are wideband, so I don't think you need to protect them from bass with a cap.

Go back and forth - the frequencies are most likely *not* going to be exactly the same for the drivers - with lower order slopes, there needs to be a "gap" where the sum of the output will "make up" for the "gap".

Set the volume of the two filters by ear. And you may want to get a UMIK-1 and use REW to measure things. Try to avoid using any PEQ - unless one of the drivers is really *not* behaving. Doing a notch filter in analog is possible, but if you can work things out without it, then you're better off.

Check the gain of your amps - if they are different, that will need to be taken into account when you go to analog XO.

Ask any questions you have, please. There is a learning curve, and if I can get you past an issue, then you can keep going.

DannyBadorine

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Re: Need Help with Building OB Speakers with MiniDSP
« Reply #17 on: 18 Dec 2022, 03:04 pm »
Using the miniDSP 2x4 HD to design a crossover - is the best thing to do with a miniDSP 2x4 HD, in my opinion. I have done this several times - and some key things to know are that you can link two channels in the 2x4 HD, so that the drivers in the left and right speakers will always be set the same. Label the outputs with tape and marker, to eliminate confusion.

I would use the Tang Band as low into the bass as they can comfortably go. I would use 1st order slopes, so that if/when you go to building the equivalent analog crossover, it will be simpler and less expensive. On the woofers, you may want 2nd order to better slope off any output to minimize duplicate sources in the critical midrange.

As for the frequencies to use - this is exactly why using the 2x4 HD is so useful - you can experiment in seconds. You can set up 4 (up to) variations, and switch between them with the remote, and hear real time how they sound. This is the whole point/benefit of doing this!

Edit: the Tang Band drivers are wideband, so I don't think you need to protect them from bass with a cap.

Go back and forth - the frequencies are most likely *not* going to be exactly the same for the drivers - with lower order slopes, there needs to be a "gap" where the sum of the output will "make up" for the "gap".

Set the volume of the two filters by ear. And you may want to get a UMIK-1 and use REW to measure things. Try to avoid using any PEQ - unless one of the drivers is really *not* behaving. Doing a notch filter in analog is possible, but if you can work things out without it, then you're better off.

Check the gain of your amps - if they are different, that will need to be taken into account when you go to analog XO.

Ask any questions you have, please. There is a learning curve, and if I can get you past an issue, then you can keep going.

This is great advice, and I didn't realize that the Tang Bang was a full range driver.  You don't need a cap to protect it while testing.  You only need a cap to protect tweeters (mostly ribbon and AMT's).
Definitely use the mini DSP to design the crossover.  Use an amplifier with two channels, send the outputs of the minidsp to each channel and then each channel to the different drivers in the test speaker.  Do your testing with the amplifier volumes all of the way up and attenuate with the minidsp (be careful with this).  Design the crossover slopes in the minidsp then build your passive crossover around that. 
The difficulty is that switching to passive components doesn't yield the same results as active so it takes a lot of experimentation to get the passive right.    The key is to take measurements in REW.  Test many different crossover slopes and settings.  See what gives you the flattest line, but make sure that the drivers are summing correctly.  Post some results on here and you'll get some guidance on if the phase is correct between the drivers.

Desertratt

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Re: Need Help with Building OB Speakers with MiniDSP
« Reply #18 on: 10 Jan 2023, 07:43 pm »
I recently finished my FIRST OB speaker, and I used the miniDSP HD for the crossover.
My setup is--

EV-12SP 12" for the "full range" (> 100Hz to about 12kHz)
15" Alpha woofer for the bass (<100Hz)
Those two are crossed over at 18dB 100Hz in the Mini.

After setting it up, I decided a tweeter might be needed. I added a 3/4" dome with a passive crossover 12dB at 12kHz. Passive X/O sits between the EV and Tweeter.

I am VERY happy with the SQ. It is nothing at all like any of the dozens of box speakers I've owned, and nothing like my Magnepan 1.7i speakers. It's bigger, more relaxed, more spacious and more lush. The bass is a tad "loose", but it doesn't bother me.

The miniDSP HD was very simple to setup and use. I was expecting more of a geeky thing, but it's well designed from a UX perspective and I enjoyed using it and setting things up. What I liked was the "live use". As music is playing, I can jiggle all the settings in the DSP from my laptop. I did this with dozens of CDs until I got good SQ by ear. Then I ran REW. Well, that's a whole other topic. It will take me some time to properly use REW.

But I wanted to assure the OP that miniDSP is easy to use. I am sure some quibble with putting an ADA between the amps and speakers, but for me the CHARACTER of the OB sound erased any deficiencies of this added signal processor. Well, that's how I fee TODAY! Might change...

Good luck to the O/P!

kd4ylq

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Re: Need Help with Building OB Speakers with MiniDSP
« Reply #19 on: 10 Jan 2023, 08:11 pm »
Desertratt,
                 thanks for your posting! I have been anxious (to say the least), about using the MiniDSP for the active crossover of the "Live edge" speakers designed by Perry Marshall. Your related experience is so positive than I am now very much encouraged to proceed, even as a newbie to DSP.