"Into The Abyss", Tweeters in low places

[xmax]

By chance do you have the new peerless tweets? These might be a match made in heaven.

Yes I do and plan on trying the combo.

[xmax]

All the variants of the XT25 hate going low - only 0.1mm xmax.

SB29 and DA25TX should deliver the goods. My current speakers use the 29RDC at 2kHz LR2 and there is no sign of distortion at 100dB/1m.

I have a couple of the WG148R waveguides too. I find that due to most full size tweeters having slightly dished faceplaces, once you fill the gap with a spacer/gasket, the throat becomes a little too deep for >10kHz to behave properly off axis. I predict about 3-4mm needs to be milled off the rear side of the 'guide, which means you lose the mounting holes.

One thing not to forget with horns/waveguides is that below the frequency range that gets boosted, distortion gets worse. So if you use a waveguide which gives you +6dB from 2-6kHz but +0dB at 1kHz, while distortion is a few dB better from 2-6kHz, distortion at 1kHz becomes 6dB worse than without the waveguide. That makes a practically sized waveguide (shallow, ~6.5" diameter) less useful at making a beast dome tweeter that is already happy to cross at say 1.5kHz, cross any lower.

The idea is to have tweeters go lower than they normally would, but happily, I very much dislike the sound of tweeters strained even before distortion rears it's ugly face.
If you look at some of my other threads you will see that several variants of the SB29 do NOT like going low, a WG could certainly change that.
I will custom CNC faceplates for the tweeters if necessary.

As for distortion raising at 1K with a wave guide, hopefully that won't be a problem because I'm not on that many drugs and would not ask any 1" dome tweeter to go that low.

[Drummer]

I'm interested as to whether or not more possibilities for a two way rs225 based system will open up. Two of the 8 ohm, ran parallel to up the sensitivity, while still keeping the upper level clean. Thanks for all the time and info, Xmax. Glenn.

[xmax]

I'm interested as to whether or not more possibilities for a two way rs225 based system will open up. Two of the 8 ohm, ran parallel to up the sensitivity, while still keeping the upper level clean. Thanks for all the time and info, Xmax. Glenn.

I have no doubt it is possible, I am trying to set a baseline measurement as we speak.

[Pete Basel]

Interesting here how Troels routes out the woofer recess right into the waveguide:

http://www.troelsgravesen.dk/C17_II.htm

[xmax]

Interesting here how Troels routes out the woofer recess right into the waveguide:
http://www.troelsgravesen.dk/C17_II.htm

I was thinking of doing something similar to keep driver spacing close but maybe not as extreme.

[xmax]

Ok here is perhaps a baseline microphone placement and gain setting. This is the RS28 on a 19"x19" test baffle
There is a active filter at 450hz and the sweep starts at 400hz, comparing my measurements to Zaph's they seem ball park.

[xmax]

And now the SB29SDAC with my same gain settings compared to HiFi Compass' work.

[xmax]

The goal is to maintain this mic gain and 6" distance and start measuring the victims with different XO's and WGs. Now that I have established the
baseline, let's see how low we can get them to go and see how low we can make the distortion.

[spasticteapot]

I would be keen to see a measurement on the new RS28 tweeters at higher output levels. I dimly recall the XT25 does not look too good if you turn the volume up - distortion above 2.5khz is quite reasonable even at 102dB/1m, but below 2, it's....sub-optimal.

Wouldn't mind seeing a waveguide comparison either. I'm currently trying to sort out the Sure DSP modules with some help, so maybe I'll be taking another crack at speaker design after all...

[Shawn_K]

I like the sound and improved imaging of 3/4" tweeters due to the wider dispersion >10kHz. The issue with the smaller tweeters is few can crossover below 3kHz LR2. I experimented with the Peerless OX20 in a waveguide to crossover at around 2.5kHz but the reflections in the waveguide caused a large dip in the response around 13kHz. I gave up on using that tweeter at that time and instead used the XT19 ring radiator in a waveguide - the phase plug blocks the reflection and had smoother frequency response. The XT19 has less radiation area and I had to do 3kHz LR2, the other issue with the XT19 is the overall diaphragm diameter is close to the size of a 1" tweeter and doesn't have as wide of dispersion as the OX20 tweeter. I'm thinking I'll experiment with the OX20 in waveguides in the future; one idea I have to try and solve the reflection issue is to make the throat of the guide small by having it overlap about half of the tweeter surround. The OX20 has a wide surround for a tweeter this size - I think the wider surround lowers the spring rate and allows a lower FS without the need for a large chamber; I think the same idea was applied to it's bigger brother DX25.

[xmax]

I would be keen to see a measurement on the new RS28 tweeters at higher output levels. I dimly recall the XT25 does not look too good if you turn the volume up - distortion above 2.5khz is quite reasonable even at 102dB/1m, but below 2, it's....sub-optimal.

Wouldn't mind seeing a waveguide comparison either. I'm currently trying to sort out the Sure DSP modules with some help, so maybe I'll be taking another crack at speaker design after all...

Yes I will be experimenting with the XT25 and XT19 they both clearly dislike going low http://hificompass.com/en/speakers/measurements makes it very
apparent.

That's why they are fine candidates to see what is possible.

As far as the "wider" dispersion of smaller domes, wave guides might compromise that aspect, but a 3/4" in a WG will still beat a 1.125" in a WG in that regard.

[johnnyrichards]

I have crossed the XT25 as low as 1850 2nd in the past. Room full of people at decent volumes - nobody complained publicly or privately. My considered and educated opinion is the reputation for the XT25 sounding bad crossed lower than X Fc is due to the Zaph effect.

My testing over the years has also confirmed that reputation is due in part to people hammering the bottom end of a tweeter using a high Q 4th LR to fill in on-axis dips. This is the equivalent of a bass boost on a subwoofer, and is a guaranteed way to increase distortion down low.

The XT25 with a shallower slope and some attention paid to transfer functions will handle 2K all day, no need to stick it behind a honk box.

[xmax]

If honk box is a reference to a proper wave guide...

[xmax]

Vistaton WG and Peerless DA25TX, the faceplate mounting screws are not quite countersunk,
fixing those and adding some holes to mount the guide to the tweet should be all it takes for a
good fit, more soon.