20-20k "omni" IB active 5-way build. Relativelly affordable.

[Ardacer]

Title says it all. This will be a build in progress.

It absolutelly should have a completely perfect and uniform dispersion, very low thd, very, very low imd through the whole range. It will be built in a wall, left and right to the tv. I expect the left channel to be about 6db max reinforced through the whole range, should be an easy fix.
This means that every single possible reflection should be spectrally as close to the front wave as possible.

The left and right notch in the wall will be filled with drywall, spaker goes inside.

This kind of directivity is what I believe I can pull off with this.

We'll see.


Every GRS sub will have a 100W rms ljm mx50se ab class amp. All other drivers will be driven by 30w rms D class amps, each driver it's own amp.
Subs will be naturally full vibration and even order distortion cancelling.

 

[alex-z]

I don't much see the point of running both a 13 and 28mm tweeter. Even with your extremely steep crossover slopes and close driver spacing, that will still cause slight time arrival differences.

I understand your goal is low distortion, but a good quality tweeter like a $60 Seas Prestige 27TDC can fulfill the role of the 13+28mm tweeters, and have extremely low distortion even with a 2200Hz crossover point.

Same again with the SB13PFC25 and PC83. Rather than using two relatively low quality drivers, why not go with a single 5" mid-range, like the Scanspeak 15W 435G00?

 

[Ardacer]

Simple. this costs nothing. All of this combined is close to one scanspeak driver. Also, 1 inch dome will simply not have the dispersion caracteristics I'm looking for. Small timing errors that high up I'm not concerned with (I should probably not be with dispersion either). Same with 5 inch driver. Crossing a 5 inch around 2000 hz will have a -7db radiation at 90 deg. This configuration here has at most -2db at all crossover points at 90 deg. Also this has a -6db at 90 deg at 20khz. 1 in dome would have a -20db.

Is this probably pointless? Why yes, it is.
Total cost of drivers was below 300$, however, and there simply is no way to do this without going either quality and expensive 4way or affordable 5way. It's perfectly doable as a 3way if you are willing to make some sacrifices (which would make sense), like forget about the 5inch, cross the 3inch at 200hz, and use a 3/4 dome or a 5/8 and who cares about what happens at 12k hz. The added cost from that to this was about 40 usd so I went with it.

Also what's cool is that by having a 5way you absolutelly destroy any IMD (worst offender to ears), so no point that I see in going for expensive quality amps. It literally costs me 2usd for a single channel d class 30w rms.

 

[jamescarter1982]

what programme or hardware are you going to use for the crossover please ?

 

[Ra1zel]

Also what's cool is that by having a 5way you absolutelly destroy any IMD (worst offender to ears)

I agree that IMD is really bad, much worse than HD but a 4 way probably does the job already, with good drivers at least.

 

[Ardacer]

It's finally done. I'll just paste an imgur album link here, it's a hassle to embed everything manually.

https://imgur.com/a/P8ub4ka

 

[Ardacer]

I've eq-ed the sub bass and did some more tests.

This is the horisontal directivity plot. I'll do vertical later but it won't be very different. There isn't any data for 90+ cause there isn't 90+, it's a wall.

This is the final EQed listening postition FR, all over the sofa - see following.

Decay, listening position, upper line is the worst offender, still 40 db below.

Excess GD for speaker.

Excess GD subs. Small resonance at 55 hz.

Subs. Small 55 hz resonance.

Low mid box.

High mid box. Tweeters are perfect, but that's pointless.

Subs distortion, 80db. Can't do proper ground plane so no proper complex pulses testing I'm afraid.

Listning position spectrum after EQ.

Listening positions (all around the sofa) before EQ.

Some other room positions.

All spots on sofa, after EQ.

With some other room spots.

Cross to the low mid woofer.