Waveguide TMM Posted

[Norris Wilson]

Hi John,
I would like to find a good inexpensive dome tweeter that is reasonably efficient. I would like to use them with some Stephens Trusonic 80FR 8"drivers crossed over around 3.5kHz. Your wave guide idea looks worth the effort to try.
I found a Vifa DX25TGO5 that may work out with this 95db efficient fullrange driver.
Have you experiemented with any of the Vifa tweeters and your waveguide? And do you feel the DX25 tweeter would be a good choice with your wave guide implimented?
Thanks
Norris Wilson

[Geenius]

Nice work Zaph! I'll have to try this myself, looks very promising!

[GM]

Originally posted by JonPike



Wondering how much lower one might be able to usefully use a tweeter with the waveguide loading. That too, has gotten touched upon in this thread, but any further thoughts on that John? I know there is only so much Xmax to deal with on a particular tweeter, and as one goes lower in frequency it's easier to use it up... How can we figure out how low can we go before distortion or power handling starts to become a problem?

The SP Technologies site was interesting... and got me wondering if they are using some kind of custom spec tweeter, or are they thru the wonders of proper horn loading, getting something more standard to be usefully crossed over at the 750Hz (or 900) that they quote?

Greets!

At a glance I couldn't see/find enough details to form an opinion, but when loading diaphragms that are easily deformed you rapidly reach a point of diminishing returns between lowering Fc and increasing distortion to an unacceptable level, which of course is listener dependent. I'm not familiar with current tweeters, but FWIW I did fairly extensive experimentation decades ago using cheap RadioShack 1" silk domes and found it could be conically loaded at up to a 2:1 CR @ 0.707*Fs @ >60 deg.. The WG was so big though that all things considered, the ~10x higher cost (at the time anyway) for a 1" exit high SQ aluminum diaphragm compression driver was worth it.

I did find them worth the effort for physically aligning the drivers at the XO point (improving their power response a bit as a side benefit) though, and have periodically suggested doing this on various audio mailing lists/forums, but it's only been since manufacturers recently resorted to this for multi-channel music/movie mastering that it's become the 'Hot Ticket'.

That said, the detractors at the time said we can't hear the minor timing error of offset drivers with the 2-3 kHz XOs of today's typical two/three way designs. I don't know since I've never tried it, but it's plenty audible to me at up to 1.2 kHz, so as always YMMV.

GM

[AJinFLA]

I would like to use them with some Stephens Trusonic 80FR 8"drivers crossed over around 3.5kHz. Your wave guide idea looks worth the effort to try. I found a Vifa DX25TGO5 that may work out with this 95db efficient fullrange driver.
Have you experiemented with any of the Vifa tweeters and your waveguide? And do you feel the DX25 tweeter would be a good choice with your wave guide implimented?

Norris,

the DX25 would be a good candidate for a WG. It already has robust performance in the low end and excellent dispersion. The WG would lower distortion and/or allow for an even low XO point (already low for a "1 inch" dome). The controlled directivity in this range also allows superior matching to the off axis performance of the chosen midbass driver.
Which brings us to the 8" fullrange driver (I know nothing of the specifics of that driver, but this is largely irrelevant). It should be beaming badly at 3.5k. Even if it isn't, the whole point of the WG would be lost, excepy maybe a bit of directional control and time alignment. Also, it functions as a low gain horn. It will have zero effect on the efficiency above loading.
But of course, don't let me stop you from doing it if that is your desire .

Cheers,

AJ

p.s. please, please, not to discourage anyone, but a WG loaded tweeter or a dipole, etc, should be your 20th speaker project, not your 3rd - or 1st. But then again, what would I know ?

[Norris Wilson]

Thanks AJ for your reply.

Unfortunetly I do not have any measurements of the Trusonic 8" fullrange drivers, nor do I have a way to obtain them.

I am not sure about where these drivers start to beam. But, I hope since they lack a wizzer cone, that it may be a little higher than the average 8" fullrange.

I would like to find an affordable driver that is efficient enough to run on 2watts. A driver that will play well from 80Hz to 3kHz or so without a crossover.

Does anyone have a quality high efficiency driver that they would recommend for this application?

I have to agree with you about not trying to build a dipole speaker on your 1st or 3rd project. But, I feel the waveguide should be possible.

I assume the dipole speaker in your picture, is an Orion by Linkwitz.

The Orion would be an ambitious project indeed. Especially since it requires a few thousand dollars investment, and a mass amount of equalization and 8 channels of amplification.

Since I am biased towards vacuum tube amplifiers. I would not try to build an Orion speaker system due to the huge pile of equipment needed to run them, not to include the room heating of the vacuum tubes.

I would think in order to keep the sound character of vacuum tubes, one would need at least a total of 4 channels of tube amplifiers for the midrange and treble drivers.

The Orion has to be one of the finest speakers around based on the dipolar principles and it being fully active, no box colorations.

But I have not had the oportunity to listen to a pair.
Any comments about these speakers for those who have not heard them?

Norris Wilson

[GM]

Originally posted by AJinFLA
p.s. please, please, not to discourage anyone, but a WG loaded tweeter or a dipole, etc, should be your 20th speaker project, not your 3rd - or 1st. But then again, what would I know?

Greets!

In an interview very early in his career, Roger Penske was asked why he chose to start racing in a Corvette (fastest production class) rather than in the time honored way of learning the craft by progressing up through the slower classes, to which he snapped back, "I did!"

GM

[AJinFLA]

Thanks GM .

Hi Norris,

the pic was not to point out a dipole, that's a WG loaded Vifa - the XT19.

Cheers,

AJ

[GM]

Originally posted by Norris Wilson
I would like to find an affordable driver that is efficient enough to run on 2watts. A driver that will play well from 80Hz to 3kHz or so without a crossover.

Does anyone have a quality high efficiency driver that they would recommend for this application?

Greets!

Assuming you want to listen to a variety of music without clipping the amp, then it must be able to handle up to at least +30 dB transient spikes. If your loudest desired average is at a ~live acoustic jazz venue, then with two watts this means ~85 dB + (30-3) dB = ~112 dB/W sens., so the horn or array would be unacceptably big/expensive. At 75 dB avg., or what many folks watch TV movies at, you still need ~102 dB/W. AFAIK, only huge compression or 'top drawer' FR driver (Lowther, AER, etc.) horns are this efficient over this wide a BW, so once you move away from these types of systems, it boils down to how much tube 'euphonic distortion' is acceptable.

GM

[Norris Wilson]

Hi GM,

I agree with your comments about efficiency and available drivers to do the job at realistic listening levels.

This is something that I have been trying to iron out with very little success, and still keep the speaker system simple.

I am about to the conclusion that moderate listening levels are all that I will be able to acheive with this simple fullrange system approach, 75db with peaks on 2 plus watts.

I love the dynamics and lack of distortion of a horn based speaker. But, there are to many variables to consider for my liking. Variables like equalization, huge bass cabinets, with multiple drivers and amplifiers to run such a system to achieve 20Hz to 20kHz.

One of the most enjoyable home audio listening experiences that I have had, was with a four-way horn system.
The system consisted of pair of 18" Bag end subwoofers, a double horn loaded JBL bass bin with 2 x 15" woofers, a 2" JBL mid-range compression driver on multi-cell horn, and a JBL compression tweeter with a slot wave guide.

This system was driven with over 830 watts per channel, and felt like it was rippling my skin from the sound waves at 130db, yipee.

If you have any speaker suggestions that will fill my wide frequency range, less is best, efficient and reasonably priced for DIY applications desires? I am all ears and would like to persue such a speaker.

I am not asking for much, maybe????

In life, we always have to weigh out the compromises and deside which compromises are best for us, especially if it is chasing audio.

I feel like the less is best approach has its merits, and is more realistic for my room, budget, and desire to keep the equipment pile to a reasonable minmum.

Listen to the music!

Thanks

Norris Wilson

[ooheadsoo]

Not to derail the conversation, but I think, through some recent juggling of drivers and design tweaking, the current xover point for the sptechs is 600hz, which is in the Dr. Geddes ballpark.

Eagerly waiting to see measurements of the partsexpress waveguide lip, which I suspect will be bad. But maybe we can sand them down