New DIY MTM Towers designed by Dennis Murphy and Paul Kittinger

[David LR]

The NeoCD3.0 itself has fine vertical dispersion. Certainly no less than that of the mtm speaker it is in. Might have a higher crossover point though, i suppose. Higher crossover points do compromise overall dispersion.

Thanks for your reply, it does help. Wish I would have stuck to my guns on that particular ribbon tweeter. I see them used in many well received designs. But, oh well, perhaps next time. I think Richard Swerdlow stated he didn't hear all that much difference between the two tweeters so I'll stop obsessing over that.

Now that I think about it, I believe the Meniscus rep did mention something about the higher crossover point on the ribbon. Really looking forward to hearing a Dennis Murphy design.

 

[Swerd]

David

I'm really glad to hear that you got the dome version. I was ready to start whining that there's not enough love for good dome tweeters around here. The Dayton RS28F is an excellent tweeter. Very low distortion at lower frequencies.

Of course, it's possible that Meniscus had sold out of the Fountek ribbons and needed to move some domes .

It's been a while since heard these two speakers, but I think you remembered correctly what I said. At first listen, both versions sounded pretty similar. The dome version was a bit cleaner sounding in the lower treble range, and the ribbon was a bit cleaner in the upper range. If I remember correctly, the dome crossover point is about 2.2 kHz and the ribbon crossover point is 2.5 kHz.

Dennis tried some other less expensive ribbon and planar tweeters for this design, but they didn't work well at all. The LCY ribbon worked well, but it was nearly $200 each at the time. Also, at that time, there were some supply and QC problems with LCY that since have been ironed out. That was one of the reasons why Salk dropped the LCY for the RAAL tweeter.

Grant's observation about power handling between the Fountek and Dayton tweets is also good.

The reason why the crossovers for the two ER18 MTM versions are so different is because the ribbon tweeter required it. The dome is very robust and can actually be crossed over below 2 kHz. Not the ribbon. Dennis says he was going as low as he dared at about 2.5 kHz. And it required some coaxing.

TLS Guy's description of the the ribbon hi-pass network is very good. It required a resonance or notch filter, the part with the resistor, coil, and cap in series with each other (an LCR filter), but in parallel with the tweeter. This LCR filter, as TLS Guy described, changes the Q of the filter to minimize the broad peak below the crossover point. This changed the shape of the tweeter's roll off curve.

Dennis takes care to make the roll off curves of the woofer and tweeter as symmetrical as possible with each other, so as a result, the woofer circuits have to be different in each version. I believe Grant mentioned this helps ensure good driver phase integration.

Dennis says these speakers have LR 4th order crossover slopes. Some of you may have noticed that the crossover diagrams don't look like 4th order filters. You are correct. Dennis like to make a distinction between the electrical and the acoustic roll off curves. "Electrical" refers to the transfer function of the filter, and "acoustic" refers to the measured sound of the driver combined with the filter.

I've rambled a bit, but I hope this covers your questions. Great conversation .

So David, where are the photos?

 

[mdrake]

David

I'm really glad to hear that you got the dome version. I was ready to start whining that there's not enough love for good dome tweeters around here. The Dayton RS28F is an excellent tweeter. Very low distortion at lower frequencies.

Of course, it's possible that Meniscus had sold out of the Fountek ribbons and needed to move some domes .

It's been a while since heard these two speakers, but I think you remembered correctly what I said. At first listen, both versions sounded pretty similar. The dome version was a bit cleaner sounding in the lower treble range, and the ribbon was a bit cleaner in the upper range. If I remember correctly, the dome crossover point is about 2.2 kHz and the ribbon crossover point is 2.5 kHz.

Dennis tried some other less expensive ribbon and planar tweeters for this design, but they didn't work well at all. The LCY ribbon worked well, but it was nearly $200 each at the time. Also, at that time, there were some supply and QC problems with LCY that since have been ironed out. That was one of the reasons why Salk dropped the LCY for the RAAL tweeter.

Grant's observation about power handling between the Fountek and Dayton tweets is also good.

The reason why the crossovers for the two ER18 MTM versions are so different is because the ribbon tweeter required it. The dome is very robust and can actually be crossed over below 2 kHz. Not the ribbon. Dennis says he was going as low as he dared at about 2.5 kHz. And it required some coaxing.

TLS Guy's description of the the ribbon hi-pass network is very good. It required a resonance or notch filter, the part with the resistor, coil, and cap in series with each other (an LCR filter), but in parallel with the tweeter. This LCR filter, as TLS Guy described, changes the Q of the filter to minimize the broad peak below the crossover point. This changed the shape of the tweeter's roll off curve.

Dennis takes care to make the roll off curves of the woofer and tweeter as symmetrical as possible with each other, so as a result, the woofer circuits have to be different in each version. I believe Grant mentioned this helps ensure good driver phase integration.

Dennis says these speakers have LR 4th order crossover slopes. Some of you may have noticed that the crossover diagrams don't look like 4th order filters. You are correct. Dennis like to make a distinction between the electrical and the acoustic roll off curves. "Electrical" refers to the transfer function of the filter, and "acoustic" refers to the measured sound of the driver combined with the filter.

I've rambled a bit, but I hope this covers your questions. Great conversation .

So David, where are the photos?

Wow, great post!!! That really helps explain how the xover works.

Matt

 

[Dennis Murphy]

Wow, great post!!! That really helps explain how the xover works.

Matt

Thanks Swerd. I haven't been following this thread, but got an alert in a PM today. Just to summarize, and add one point, the woofer crossover is very simple because the crossover point is low. I didn't need a trap circuit to get the breakup point of the ER18 woofer suppressed sufficiently, because the 4th order acoustic slope kicks in early enough to do that by itself. That's one of the reasons
I chose the ER18 woofer--it's extremely well behaved below the breakup peak at 5 kHz, and only needs an inductor and a shunt circuit consisting of a single cap or a cap and small inductor depending on the crossover frequency. The main reason the tweeter crossover is so complex is that MTM configurations often produce strong diffraction peaks and dips, intensified by the woofer cavities at equal distances from the tweeter. I've attached two plots--one of the Fountek tweeter with no crossover, and one with the filter I ended up using. (I can't seem to find my RS dome tweet file, but the same issue is involved.) You get the usual tweeter diffraction peak at the low end, but also a big dip at and above the crossover region. If you don't really work at it, you will end up with a dip in the response where the ear is most sensitive. That's why the tweeter circuit is so complex--I had to bend things around so that I could minimize the dip.

 

[David LR]

David


I've rambled a bit, but I hope this covers your questions. Great conversation .
So David, where are the photos?

First off, thanks for your explanation. You are right, it is a good conversation.

Photos ?? Surely, you are tired of seeing bare MDF speaker carcasess ?

No, I plan to start a thread & post some pictures. It will be the first "build thread" I've ever posted so I'll be doing so with some trepidation.

 

[David LR]

That's why the tweeter circuit is so complex--I had to bend things around so that I could minimize the dip.

Thanks very much for responding, I have no technical or experiential reasons for my crossover questions, the woofer crossover was so simple, the tweeter crossover so involved, it just struck me, that's all. Very nice to have the designer himself answer questions. Really looking forward to hearing them !

 

[Dennis Murphy]

Thanks very much for responding, I have no technical or experiential reasons for my crossover questions, the woofer crossover was so simple, the tweeter crossover so involved, it just struck me, that's all. Very nice to have the designer himself answer questions. Really looking forward to hearing them !

Hi It was an interesting question, and one I happened to know the answer to. Doesn't happen very often.

 

[mdrake]

Thanks Swerd. I haven't been following this thread, but got an alert in a PM today. Just to summarize, and add one point, the woofer crossover is very simple because the crossover point is low. I didn't need a trap circuit to get the breakup point of the ER18 woofer suppressed sufficiently, because the 4th order acoustic slope kicks in early enough to do that by itself. That's one of the reasons
I chose the ER18 woofer--it's extremely well behaved below the breakup peak at 5 kHz, and only needs an inductor and a shunt circuit consisting of a single cap or a cap and small inductor depending on the crossover frequency. The main reason the tweeter crossover is so complex is that MTM configurations often produce strong diffraction peaks and dips, intensified by the woofer cavities at equal distances from the tweeter. I've attached two plots--one of the Fountek tweeter with no crossover, and one with the filter I ended up using. (I can't seem to find my RS dome tweet file, but the same issue is involved.) You get the usual tweeter diffraction peak at the low end, but also a big dip at and above the crossover region. If you don't really work at it, you will end up with a dip in the response where the ear is most sensitive. That's why the tweeter circuit is so complex--I had to bend things around so that I could minimize the dip.

Thanks for explaining in such detail! Any tips on were to learn the in and outs of xover design?

Matt

 

[mdrake]

Refresh

Since the new neoX has been released and has a lower xover point, do you think this design needs a refresh?

Matt

 

[Swerd]

Since the new neoX has been released and has a lower xover point, do you think this design needs a refresh?

After quickly looking over what's written on the new NeoX models at Madisound, it's not clear to me whether the NeoX 1.0 offers any advantage over the old NeoCD 3.0. The price is a bit higher and the rectangular faceplate is ½" shorter than the old round one on the CD 3.0.

Can the NeoX 1.0 be crossed over lower? Will the Neo CD 3.0 still be available? Stay tuned.

 

[mdrake]

This is the fountek I was referring to
Fountek NeoX 3.0 Ribbon Tweeter with Black Faceplate: Madisound Speaker Store
it recommends a 2nd order at 2k!

Matt

 

[Swerd]

This is the fountek I was referring to
Fountek NeoX 3.0 Ribbon Tweeter with Black Faceplate: Madisound Speaker Store
it recommends a 2nd order at 2k!

There are several new Fountek NeoX models listed at Madisound, the 1.0, 2.0 and 3.0. The previous model, NeoCD 3.0, came with a round faceplate 110 mm in diameter. The NeoX 3.0 that you linked is much larger, the faceplate is 144×69.5 mm. In an MTM design, that extra 34 mm (1.3") forces the woofers farther apart, creating interference problems. In general the closer the woofers are to the tweeter, the better. Also the taller a ribbon is, the narrower its vertical dispersion is, another problem.

The NeoX 1.0 has a smaller rectangular faceplate 98×69.5 mm and the NeoX 2.0 comes both with round faceplate 123 mm diameter and rectangular 113.5×69 mm. Either of those allow a closer fit, but they seem, on paper, to have similar properties to the NeoCD 3.0.

Despite what Fountek claims, crossing the NeoCD 3.0 at 2.5 kHz with 2nd order crossover slopes was not possible in an MTM cabinet with a 9" wide front baffle. To have a smooth sound (as Dennis showed), it required steeper 4th order slopes and a notch filter to correct the irregularities in the roll-off curve.

Before anything definite can be said about these new tweeters, more testing is required, to see how low they really can play, and what distortion levels come up at those frequencies.

 

[lorkp]

Jay

I sent you a PM with my email address. I can't send an attachment by PM, but if you email me back, I'll send you the pdf version of the plans.

Richard

I'd PM you, but I don't have enough posts under my belt yet. Would you please PM me and to arrange having the PDF plans emailed to me? Thanks!

 

[williambigears]

I've been reading this thread with great interest. In the proces of selecting what i want to build.
Right now i have an old set of DIYs visaton VIBs, design from 1986 if i remember correctly.
Been in need of something different for a long long time but never got around to it until now.
Had almost made up my mind to go for the mini statements but came across this thread.
Richard, i can't PM you and i'd like the plans in pdf.

The recent posts on tweeters are interesting although the technical side is over my head.
Besides the comments on roll off, the ribbons being a less a bit less noisy and the dome a bit smoother down low is it possible to say something about which type of tweeter gives the "better" overall result/balance or is it strictly taste?

And a question for skyline. somewhere in the thread you mention an issue with a certain song and a certain line in that song giving a sort of blowing acros a bottle effect. Maybe i missed it but did you sort that out?

 

[skyline_123]

And a question for skyline. somewhere in the thread you mention an issue with a certain song and a certain line in that song giving a sort of blowing acros a bottle effect. Maybe i missed it but did you sort that out?

Hi William. Yes, I did sort that out. I'm not sure exactly what I was hearing but the bass definitely caught my attention as being 'different'. I eliminated the issue by putting in the "pillow stuffing". Now it's nice and smooth, very natural sounding. It still amazes me after all this time, even after building the 12" Kappa Perfect and the Tuba HT, the bass from the ER18's is beautiful.

Good luck with this build, you've made a great choice!

 

[capricious]

skyline_123,

I see that you have used precision port ... and i too would like to use the same in my build. Can you please tell me what is the port length you used? Even without the middle port portion, the length comes out to be about 6" which is longer than the 3 3/4" recommended for dual flared ports.

Thanks!

 

[mattsk8]

I've been reading this thread with great interest. In the proces of selecting what i want to build.
Right now i have an old set of DIYs visaton VIBs, design from 1986 if i remember correctly.
Been in need of something different for a long long time but never got around to it until now.
Had almost made up my mind to go for the mini statements but came across this thread.
Richard, i can't PM you and i'd like the plans in pdf.

The recent posts on tweeters are interesting although the technical side is over my head.
Besides the comments on roll off, the ribbons being a less a bit less noisy and the dome a bit smoother down low is it possible to say something about which type of tweeter gives the "better" overall result/balance or is it strictly taste?

And a question for skyline. somewhere in the thread you mention an issue with a certain song and a certain line in that song giving a sort of blowing acros a bottle effect. Maybe i missed it but did you sort that out?

Where do you live (state)? I've heard the mini statements sound almost as good as the full size versions (I think even Jim Holtz says this). Curious because I'm in MI and I'm building the ER18's w/ the ribbons right now and can't wait to compare those w/ the full size Statements. If you're not too far you could listen as well. The Statements I built are nothing short of stunning!! Insane accuracy and detail, plus amazing the way the sound surrounds you.

 

[williambigears]

Where do you live (state)? I've heard the mini statements sound almost as good as the full size versions (I think even Jim Holtz says this). Curious because I'm in MI and I'm building the ER18's w/ the ribbons right now and can't wait to compare those w/ the full size Statements. If you're not too far you could listen as well. The Statements I built are nothing short of stunning!! Insane accuracy and detail, plus amazing the way the sound surrounds you.

I'm from the Netherlands, i'd love to listen and thanks for the very kind offer but i hate flying...however....you're free to come over with those statements so i can have a listen
Interesting that you're buidling the ER18s, wondering how those will compare to the full statements.
The original plan was to go for the full size statements, but my ever so caring GF would stop caring and shoot me if i'd put those in our living room...the mini statements barely pass her judgement but with some extra TLC from me she said yes.
But now i have the hots for the ER18s.
Think i'll be going for the dome version, which already is giving me headaches cause it seems all the part sellers in Europe only sell the A-4 version of that tweeter, and not the F-4.

 

[williambigears]

About the RS28F-4 tweeter, I've been searching and searching but really can't find it anywhere in Europe...which is rather weird. So I'm going to have to order it from the US. Might as well order the ER18s and the other parts at the same time. Since shipping costs are somewhat steep, does anyone know a decent seller who stocks both brands and ships internationally?

 

[doors666]

About the RS28F-4 tweeter, I've been searching and searching but really can't find it anywhere in Europe...which is rather weird. So I'm going to have to order it from the US. Might as well order the ER18s and the other parts at the same time. Since shipping costs are somewhat steep, does anyone know a decent seller who stocks both brands and ships internationally?

You can use the meniscus kit

ER18MTM Dome