Hivi 3.1A DIY Speaker With Sehlin Mod Review

[AllenW]

I always thought it was interesting (odd) that HiVi chose to include a biwire input cup, but not utilize it. What I would do is connect the upper pair of input terminals to the input + and - positions on the crossover board. The woofer inductor (the longer coil on its side adjacent to the input + and - holes) should have the lead that is connected to input + disconnected and instead connected directly to the lower positive input terminal. The lower negative input terminal can remain connected to the upper negative input terminal as they both go to ground. You can either do that by just leaving the negative copper bus bar in place or by connecting the two negative terminals inside the cabinet to make it mistake-proof.

I wouldn't bother with 2 amps but I love the class A sound and the crown controls woofers like nothing I've ever heard. It makes them sound deeper and faster.

 

[Mudjock]

I certainly agree that the best bass amp is not always the best full range amp. The challenge in the case of the DIY 3.1A is that the woofer is playing up over 1 kHz. The Crown may still be the way to go, but its influence will extend well into the midrange.

 

[AllenW]

I certainly agree that the best bass amp is not always the best full range amp. The challenge in the case of the DIY 3.1A is that the woofer is playing up over 1 kHz. The Crown may still be the way to go, but its influence will extend well into the midrange.

That should work. The crown is only slightly weaker in the mid and upper range than the class A. I had been using it as a sub amp from the time I bought it. Then my main amp went out so I put the crown in it's place and I was very supprised how good it sounds. Actually was much better than the class ab amp it replaced. The class A is just so smooth in the top end though.

 

[Mudjock]

So it would be fine to have the 2 amps grounded together?

In most cases yes. In my 40 years of dealing with various audio components, I have had a couple of cases where grounding issues caused misbehavior. I would expect the Crown to be properly designed in that regard, but less sure about the class A amp. Some lower volume products don't go through UL or ETL certification and are more likely to have issues depending on the expertise and/or priorities of the designer.

 

[AllenW]

In most cases yes. In my 40 years of dealing with various audio components, I have had a couple of cases where grounding issues caused misbehavior. I would expect the Crown to be properly designed in that regard, but less sure about the class A amp. Some lower volume products don't go through UL or ETL certification and are more likely to have issues depending on the expertise and/or priorities of the designer.

No reason to chance it. I'll look at the crossover board real good. Maybe I can cut some traces on the board to separate the negatives.

 

[AllenW]

In most cases yes. In my 40 years of dealing with various audio components, I have had a couple of cases where grounding issues caused misbehavior. I would expect the Crown to be properly designed in that regard, but less sure about the class A amp. Some lower volume products don't go through UL or ETL certification and are more likely to have issues depending on the expertise and/or priorities of the designer.

I think I can cut the trace just before the 47uf cap and combine the input and woofer ground at the woofer output.

 

[AllenW]

As someone who's still struggling to paint these, I like your surfacing. What veneer did you use?

This is the process I used to apply the veneer. As far as the Flush trim bit goes, if you had any misalignment in your panels like I did, there is a risk the bit will dig into some of the surfaces because everything isn't perfectly square. I opted to use a retractable utility knife pushed pretty far out and filed it the rest of the way flat. I did buy one of the shallow flush bits for the dados. I used titebond original instead of the heat lock. It worked fine and was a lot cheaper. I used a IR temperature gun to set my iron to 140f and it bonded fine and won't burn the veneer or cook the glue. Use a teflon coated iron, aluminum will rub off on the veneer. Use paper between the two if it's not coated. The whole proccess was a lot easier than I thought it would be. A lot easier than trying to get paint to look factory.

 

[AllenW]

This is the process I used to apply the veneer. As far as the Flush trim bit goes, if you had any misalignment in your panels like I did, there is a risk the bit will dig into some of the surfaces because everything isn't perfectly square. I opted to use a retractable utility knife pushed pretty far out and filed it the rest of the way flat. I did buy one of the shallow flush bits for the dados. I used titebond original instead of the heat lock. It worked fine and was a lot cheaper. I used a IR temperature gun to set my iron to 140f and it bonded fine and won't burn the veneer or cook the glue. Use a teflon coated iron, aluminum will rub off on the veneer. Use paper between the two if it's not coated. The whole proccess was a lot easier than I thought it would be. A lot easier than trying to get paint to look factory.

If you use a knife don't cut all the way when doing the cross grain cuts. Go most of the way and then cut the rest from the other way. If you don't the end will tear out. He also has anther video on finishing them and so far it's looking really good. I'll post more pics when it's done.

 

[simbloke]

Don't know why but I didn't notice this review when it was first published. I really like the look of these speakers and I think I should be able to put them together without too much trouble - so long as I'm careful painting.

They're not available on Amazon in the UK but it looks like soundimports.ue have them.
https://www.soundimports.eu/en/hivi-diy31-kit-white.html
Not 100% sure but it looks like this kit comes with cabinets assembled, for a higher price of course. Anyone know for sure?

 

[AllenW]

Crossover points are 1.2 kHz between the woofer and mid and 5.8 kHz between the mid and tweeter. The mid-tweeter crossover is more like 24 dB/octave. The woofer-mid crossover is a little shallower and not completely symmetric. Both drivers have pretty wide off axis dispersion at that point, so I think you would be fine starting at 24 dB/octave if doing an active crossover.

Do you think there would be an advantage in putting a 2.5 or even 3 ohm resister in the R3 position on The perfectionist option? like you suggested on the option 3. I'm sensitive to the 1000hz range and would like to bring it down a bit.

 

[AllenW]

I would like to take a little time to provide more information and address a few questions and comments.

First of all, many thanks to Amir for the review. I put him through a lot for this review. I freely admit that most of the speakers I build can best be thought of as prototypes. Drivers are frequently connected with removable connectors as opposed to solder. I've had a last minute defective driver replacement at a DIY event/competition and it's a lot easier than bringing a soldering iron... Crossover boards are often mounted in such a way to be removable for future tweaking. All of these issue came home to roost for this review as Amir's first comment was that something was rattling inside the cabinet, which turned out to be the crossover board that came loose during shipping. When Amir reattached that and ran his tests, it was apparent that the tweeter had no output, so he had to open them back up, reattach the tweeter wires, and remeasure. I wouldn't have blamed him at all for sliding these down on the Panther scale, but he did the opposite. If I send anything in the future, I will at least make sure the assembly methods are fit for commercial ground transportation.

HiVi deserves all the credit the cabinet design and tuning that protects the woofer and the midrange, enabling distortion to stay under control at high output. They picked a good set of drivers for this kit, which is what initially interested me, as I had previously heard all of the drivers (and worked with the midrange on another project).

I always thought it was odd that they chose to design a crossover with such a rising response. This is straight from the swanspeakers website.
View attachment 81674

I saw an assembled pair for sale on our local craigslist and decided that it would be fun to see if they sounded like the manufacturer's response curve indicated and see what it would take to flatten the response curve. I step through the process on the Midwest Audio Club forum

MAC/DIY HiVi DIY 3.1 Post

I summarized the results on my Sehlin Sound Solutions page. The speakers reviewed include the option 4 "perfectionist option" crossover.



This is certainly true. There are a number of reasons for that, but the name is perhaps a bit misleading. I set out to see if simply tweaking resistors could fix the crossover, but that wound up not to be the case. Although I could bring the mids and highs in balance with the bass, the response was very uneven as shown in options 1-3. For option 4, I constrained myself in a couple of ways:

1. Add no complexity to the assembly process versus the original kit
2. Keep the cost low

These considerations meant that whatever I did would allow use of the circuit board that comes with the kit and would not touch the most expensive components (larger inductors and capacitors). The resulting mod only adds about $25 in parts to the $299 kit.

View attachment 81679

I was very relieved that the on axis response and impedance (actual driver measurements with a simulated crossover applied) closely matches the on axis response from the Klippel NFS.



It is possible to tweak the crossover to bring the level down a dB or two where it is elevated. The changes I would recommend include

1. Increase C5 (in the woofer circuit) from 47 uF to 68 uF.
2. Increase R2 from 2 ohms to 3 ohms in the midrange circuit
3. Increase R1 from 5.6 ohms to 6.8 ohms (7 ohms would be fine depending on which is available) in the tweeter circuit.

View attachment 81685

I'm not sure if that will sound better in all rooms as part of the reason I set the mid and tweeter level where I did was to avoid the upper bass region from standing out and sounding too "tubby"



I have long been a fan of dome and other unusual mids. Here is a recent picture of my listening rotation.

View attachment 81683
The 3 way's with the dome mid are an unpublished design because the 3" Tang Band dome mid is no longer available to DIY'ers.

View attachment 81684

This is the Indium 7 design which was one of my Parts Express Design Team projects and still can be built. It uses the same mid as the HiVi DIY 3.1A (except for a slightly different flange).

I ordered these tweak parts. I like how flat that looks.

 

[AllenW]

 

[AllenW]

I just need to wait for some parts and it's going together. I left the holes for the grills open under the veneer, if the grill cloth comes out good I'll route them out. It surprised me that you can't even tell they are there.

 

[Moto]

I just built a set of the 3.1’s but hadn’t read about the mods in advance so have the stock crossover. Would someone who is more knowledgable than I am be willing to propose an eq for the stock setup? I’ll implement it in Roon.
Here is a pointer to the stock fr. https://diy.midwestaudio.club/discussion/550/hivi-diy-3-1-revisited

 

[beagleman]

I just built a set of the 3.1’s but hadn’t read about the mods in advance so have the stock crossover. Would someone who is more knowledgable than I am be willing to propose an eq for the stock setup? I’ll implement it in Roon.
Here is a pointer to the stock fr. https://diy.midwestaudio.club/discussion/550/hivi-diy-3-1-revisited

I know you are looking to DSP them, but would be fairly easy to implement the mods to the crossover still.

 

[Moto]

The thing is that Iwill be using Roon to tweak whatever starting eq I can get anyway for the particular room I have them in. So it makes sense to use software for the basic eq.

 

[Mudjock]

If you haven't already assembled the crossover, I would still recommend doing the perfectionist mod. I'm not saying that because I profit from it in any way (I don't). The reason is that I am concerned about the way the drivers response overlaps around the crossover points with the stock crossover (see below from Swans website). Eq. can flatten the response on axis, but won't fix that issue, which may lead to undesirable behavior off axis. The perfectionist mod cleans up the transitions between drivers and also gets the response most of the way to neutral if you ever decide to repurpose the speakers to a situation where you won't be using parametric eq.

 

[Moto]

If you haven't already assembled the crossover, I would still recommend doing the perfectionist mod. I'm not saying that because I profit from it in any way (I don't). The reason is that I am concerned about the way the drivers response overlaps around the crossover points with the stock crossover (see below from Swans website). Eq. can flatten the response on axis, but won't fix that issue, which may lead to undesirable behavior off axis. The perfectionist mod cleans up the transitions between drivers and also gets the response most of the way to neutral if you ever decide to repurpose the speakers to a situation where you won't be using parametric eq.

View attachment 143017

They are already complete and I am enjoying them. I will definitely do that mod eventually but have no time now to do any projects.

 

[Mudjock]

I understand. I did measure the response of the stock configuration and have a file of that measurement, but would need someone to help with the PEQ setting that would flatten it out.

 

[AllenW]

I plan on getting two more pairs of these for a 5.1 setup. I'll use one set to make a center channel with a tweeter, midrange and two woofers. Would having two woofers be fine with the crossover like it is?