TangBand 75-1558SE on a Waveguide with Measurements

[JochenM]

Re: TangBand 75-1558SE on a Waveguide with Measurements

Just realized I did not take any pictures last year when I built the final design. To your question: after routing the chamfer of the waveguide, I routed that ring away. Then I attached the foam where that ring was instead of to the driver flange like I showed in that first post. So basically the foam takes up the space better than the little ring did, which had a unavoidable small gap.

Thanks a lot, that was exactly what I wanted to hear ;)

I think I'm going to use gasket tape and maybe modeling clay for finetuning.

[augerpro]

Re: TangBand 75-1558SE on a Waveguide with Measurements

It was indeed on the first page ;)
Did you again use that slight 1/8" "ring" that was not routed away and that you've marked in the picture on page 1?

Thanks a lot.

Just realized I did not take any pictures last year when I built the final design. To your question: after routing the chamfer of the waveguide, I routed that ring away. Then I attached the foam where that ring was instead of to the driver flange like I showed in that first post. So basically the foam takes up the space better than the little ring did, which had a unavoidable small gap.

[JochenM]

Re: TangBand 75-1558SE on a Waveguide with Measurements

It was indeed on the first page ;)
Did you again use that slight 1/8" "ring" that was not routed away and that you've marked in the picture on page 1?

Thanks a lot.

[augerpro]

Re: TangBand 75-1558SE on a Waveguide with Measurements

Hi Brandon,

sorry to resurrect this thread but I'm curious how you treated the gap created by the faceplate when mounted to a even surface/from behind? Modeling clay?
I want to use the mid exactly the same way soon.

Thanks
Jochen

I used the speaker gasket material from PE, basically 1/8" thick black weather stripping. I think I posted somewhere in this thread about the effect without the foam strip, it is measurable. But just flush with the mouth of the waveguide corrects it just fine.

[JochenM]

Re: TangBand 75-1558SE on a Waveguide with Measurements

I think I have a usable waveguide now. Very simple 3/4" deep, 3/4" chamfer, and 3 13/16" throat. And after a lot of baffle sims and a few prototypes to see just how well the sims' results work with an actual crossover in place, I measured on the final baffle design. My 3 way will move forward now: 8" Peerless HDS woofer (for now), hopefully a Transducer Lab tweeter, and one version with the TB dome mid and another using the BG Neo8. Here is a pic of the mockup of the final baffle, raw response of the TB, and after a LR4 bandpass crossover is in place at 700hz and 2600hz:

Not sure if I'll do anything about the higher frequency response peak. I was listening to this (and a few other drivers) unfiltered the other day and it sounds really smooth, the higher frequencies just melt away. No wonder midband distortion is so low.

Hi Brandon,

sorry to resurrect this thread but I'm curious how you treated the gap created by the faceplate when mounted to a even surface/from behind? Modeling clay?
I want to use the mid exactly the same way soon.

Thanks
Jochen

[Pete Schumacher]

Re: TangBand 75-1558SE on a Waveguide with Measurements

Was the ripple introduce by the edge largely present in the horizontal off-axis plots? If so, the horizontal directivity would be largely fixable in the crossover although not the vertical.

The most informative way to study all this in a quantifiable way is probably to perform a set of acoustic wave simulations. A few years ago it was near the top of my to-do list but it has steadily slipped down. The lack of enthusiasm of the local TB distributor for the 3" dome was what started things rolling down hill.

It only stands to reason that a sharp edge will introduce more ripple on axis than a smooth transition. And because these types of monitors are usually listened to fairly close to on-axis, getting a smooth response on axis would seem to be more important than worrying about the forward lobe being a couple degrees narrower, IMO.

[andy19191]

Re: TangBand 75-1558SE on a Waveguide with Measurements

Spreading the guides apart pushed the CTC spacing 3/8" wider then what the spacing would be with the TB75 and XT25TG30 on a flat baffle. With the guides overlapping as in the Genelec and K&H guides the CTC was 4" in my test guide. Spreading them apart made for a 5.5" spacing. I do not believe I posted the results as I was developing these for a client in France at the time. With the crossover point being between 1.6 kHz and 2.0 kHz I didn't think the CTC was as important as a smoother on axis measurement. I should have the measurements on my laptop and could post them if there is interest.

Was the ripple introduce by the edge largely present in the horizontal off-axis plots? If so, the horizontal directivity would be largely fixable in the crossover although not the vertical.

The most informative way to study all this in a quantifiable way is probably to perform a set of acoustic wave simulations. A few years ago it was near the top of my to-do list but it has steadily slipped down. The lack of enthusiasm of the local TB distributor for the 3" dome was what started things rolling down hill.

[davepellegrene]

Re: TangBand 75-1558SE on a Waveguide with Measurements

Spreading the guides apart pushed the CTC spacing 3/8" wider then what the spacing would be with the TB75 and XT25TG30 on a flat baffle. With the guides overlapping as in the Genelec and K&H guides the CTC was 4" in my test guide. Spreading them apart made for a 5.5" spacing. I do not believe I posted the results as I was developing these for a client in France at the time. With the crossover point being between 1.6 kHz and 2.0 kHz I didn't think the CTC was as important as a smoother on axis measurement. I should have the measurements on my laptop and could post them if there is interest.

Dave

[andy19191]

Re: TangBand 75-1558SE on a Waveguide with Measurements

I think the pros and cons are pretty clear cut. Dave has shown that smoother response results from two distinct guides. It may add a little CTC distance which would be the down side. But improved performance for the tweeter response is the obvious benefit. Genelec and K&H simply made the choice to go with a little extra diffraction ripple and keep the spacing tighter.

Has Dave shown results for the sharp edge case that I have missed?

[Pete Schumacher]

Re: TangBand 75-1558SE on a Waveguide with Measurements

That would be an interesting comparison to see. Both K&H and Genelec have opted to keep the sharp edge which suggests the pros and cons may not be clear cut. Perhaps an answer in your thread rather than Brandon's would be tidier.

I think the pros and cons are pretty clear cut. Dave has shown that smoother response results from two distinct guides. It may add a little CTC distance which would be the down side. But improved performance for the tweeter response is the obvious benefit. Genelec and K&H simply made the choice to go with a little extra diffraction ripple and keep the spacing tighter.

[andy19191]

Re: TangBand 75-1558SE on a Waveguide with Measurements

While doing research on the combo guide using the TB75 I came across this link. My first prototype was taken from it. What I had found was the sharp edge between the two guides added quite a bit of diffraction on the tweeter on axis. Spreading the guides apart so each is a full guide took care of the diffraction and also added a couple dbs of boost on the bottom end.

That would be an interesting comparison to see. Both K&H and Genelec have opted to keep the sharp edge which suggests the pros and cons may not be clear cut. Perhaps an answer in your thread rather than Brandon's would be tidier.

[davepellegrene]

Re: TangBand 75-1558SE on a Waveguide with Measurements

Since we are looking at German speakers here is a documented similar effort.

While doing research on the combo guide using the TB75 I came across this link. My first prototype was taken from it. What I had found was the sharp edge between the two guides added quite a bit of diffraction on the tweeter on axis. Spreading the guides apart so each is a full guide took care of the diffraction and also added a couple dbs of boost on the bottom end.



I'm just finishing up a combo guide with the TB75 and the SS D2604. I plan to do an A/B test against the Audax TW25.

I'll be posting my results in my thread with the combo guide here.
http://techtalk.parts-express.com/sh...ombo-Waveguide

Dave

[andy19191]

Re: TangBand 75-1558SE on a Waveguide with Measurements

Since we are looking at German speakers here is a documented similar effort.

[JochenM]

Re: TangBand 75-1558SE on a Waveguide with Measurements

Looks a lot like Dave Pellegrene's waveguide design, have you seen that?

Absolutely. And regarding the fact that Klein&Hummel/Neumann were the first ones with waveguides like that for dome mids, Dave is right on track.
They made about 200 prototypes for the O500 back in 2000 I think.

[augerpro]

Re: TangBand 75-1558SE on a Waveguide with Measurements

Looks a lot like Dave Pellegrene's waveguide design, have you seen that?

BTW I have the Transducer Lab tweeters ont eh way Everything is proceeding as I have foreseen...Going to take some vacation this month to pound these out, along with the 9 bookshelf TM's and 3 MTM's I was working on today.