New DIY MTM Towers designed by Dennis Murphy and Paul Kittinger

[roadrune]

Got to do the final gluing on both speakers today

Im low on clamps, so a little improv is needed

 

[roadrune]

And finished except from drivers and finish.

On my way to work now next update wont be for a couple of weeks...

 

[Swerd]

Fast work! Good luck and stay safe out there.

 

[FingerlessHackWoodworker]

To listen to them side by side, the ribbons were a tiny bit less noisy sounding to me, but just to say it with those words exaggerates the difference I heard. That Dayton dome is a bit smoother sounding on it's lower freqs than the ribbon.

Swerd, thanks for this critique.

I want to make sure I understand; sorry for my ignorance. What is meant by ribbons being tiny bit less noisy? Does this mean they sound a little more forward/ brighter/ slightly-exaggerated in regards to actual performance? Or, high-freqs at times sound like a buzzy noise?

Dayton dome is a bit smoother sounding on it's lower freqs. Does this also mean the ribbon tends to sound a little louder in comparison?

I think my personal taste is slightly exaggerated tweeter.

 

[Swerd]

I want to make sure I understand; sorry for my ignorance. What is meant by ribbons being tiny bit less noisy? Does this mean they sound a little more forward/ brighter/ slightly-exaggerated in regards to actual performance? Or, high-freqs at times sound like a buzzy noise?

No, the ribbon tweets are not more forward, brighter, or slightly exaggerated in comparison to the dome tweeter version. Both versions of the ER18 MTM have a similar overall balance (properly balanced, in my opinion) between bass and treble. By less noisy, I mean they sounded cleaner. There was less in their performance to notice or criticize. Many domes (even some very good ones) can create a slight sibilant sound depending on the recording, a 'sssssh' sound. A good ribbon tweeter is noiseless in comparison. The differences are subtle. Just by choosing the words I used, I'm exaggerating the differences I heard.

The downside of using a ribbon in a 2-way like the ER18 MTM is finding a crossover point high enough to avoid the frequencies where the ribbon begins to distort, and low enough to avoid the woofers' break up noise. This usually requires some extra effort for a crossover designer, and some extra parts.

Dayton dome is a bit smoother sounding on it's lower freqs. Does this also mean the ribbon tends to sound a little louder in comparison?

The dome has less distortion at lower frequencies, allowing it's crossover frequency to be lower. That lower crossover freq made avoiding the woofer's break-up noise easier and less costly in crossover parts.

I honestly think it's a toss-up between the two different tweeters in this design. It may come down to price.

 

[David LR]

Swerd, thanks for this critique.

I want to make sure I understand; sorry for my ignorance. What is meant by ribbons being tiny bit less noisy? Does this mean they sound a little more forward/ brighter/ slightly-exaggerated in regards to actual performance? Or, high-freqs at times sound like a buzzy noise?

Dayton dome is a bit smoother sounding on it's lower freqs. Does this also mean the ribbon tends to sound a little louder in comparison?

I think my personal taste is slightly exaggerated tweeter.

FingerlessHack:

I have some input here, having been the only builder (as far as I know) to use the Dayton dome verison. When I ordered the kit from Meniscus I had every intention of going with the ribbon version but changed my mind when a Meniscus rep expressed some reservations about too much beaming from the ribbon, so
I chose the dome. In retrospect, I wish I would have chosen the ribbon, not that I have any complaints about the Dayton dome, it sounds great, but I'd never heard a decent ribbon tweeter and still haven't !

As far as beaming goes, Dennis Murphy uses ribbons in his very high-end Philharmonic speakers so I doubt that beaming is a real issue.

Anyway, that's my two-cents worth, hope it helps.

Dave

 

[FingerlessHackWoodworker]

No, the ribbon tweets are not more forward, brighter, or slightly exaggerated in comparison to the dome tweeter version. Both versions of the ER18 MTM have a similar overall balance (properly balanced, in my opinion) between bass and treble. By less noisy, I mean they sounded cleaner. There was less in their performance to notice or criticize. Many domes (even some very good ones) can create a slight sibilant sound depending on the recording, a 'sssssh' sound. A good ribbon tweeter is noiseless in comparison. The differences are subtle. Just by choosing the words I used, I'm exaggerating the differences I heard.

The downside of using a ribbon in a 2-way like the ER18 MTM is finding a crossover point high enough to avoid the frequencies where the ribbon begins to distort, and low enough to avoid the woofers' break up noise. This usually requires some extra effort for a crossover designer, and some extra parts.

The dome has less distortion at lower frequencies, allowing it's crossover frequency to be lower. That lower crossover freq made avoiding the woofer's break-up noise easier and less costly in crossover parts.

I honestly think it's a toss-up between the two different tweeters in this design. It may come down to price.

Swerd, thank you kindly sir! Very informative.

 

[FingerlessHackWoodworker]

FingerlessHack:

I have some input here, having been the only builder (as far as I know) to use the Dayton dome verison. When I ordered the kit from Meniscus I had every intention of going with the ribbon version but changed my mind when a Meniscus rep expressed some reservations about too much beaming from the ribbon, so
I chose the dome. In retrospect, I wish I would have chosen the ribbon, not that I have any complaints about the Dayton dome, it sounds great, but I'd never heard a decent ribbon tweeter and still haven't !

As far as beaming goes, Dennis Murphy uses ribbons in his very high-end Philharmonic speakers so I doubt that beaming is a real issue.

Anyway, that's my two-cents worth, hope it helps.

Dave

Dave, thank you kindly sir. I appreciate the honesty.

 

[Swerd]

… a Meniscus rep expressed some reservations about too much beaming from the ribbon…

As far as beaming goes, Dennis Murphy uses ribbons in his very high-end Philharmonic speakers so I doubt that beaming is a real issue.

The real issue with beaming in a 2-way speaker is not with the tweeter, but with the mid woofer. The frequency range where the crossover occurs, roughly 2-3 kHz, is where most of the harmonic overtones are for the primary tones in the mid range (roughly 250-1500 Hz). If a mid woofer is crossed too high, it beams enough to negatively affect the speaker's ability to create a good stereo image.

Look at the frequency response curve for the ER18 mid woofer (below). The dark black trace is measured on-axis, and the other two lighter traces are measured at 30° and 45° (might be 60° off-axis?) off-axis. The 45° trace begins falling off above 500 Hz, but the 30° trace stays close to the on-axis trace until it goes above 2 kHz. By 3 kHz, its still within 5 dB of the on-axis trace. That's when beaming begins. In the ER18 MTM, the crossover is roughly 2.2 kHz for the dome tweeter version, and roughly 2.6 kHz for the ribbon tweeter version. That Fontek ribbon cannot go lower without distorting. As a result, the dome tweeter version has slightly better dispersion in this critical range, but I'm not sure if I could hear that difference.

There is much less music content at the frequencies where tweeters begin beaming (roughly 10-20 kHz), and most of us don't hear much above 15 kHz anyway.

 

[David LR]

Thanks, Swerd. That's a very useful & educational response, at least for my education anyway. My conversation with Meniscus was over 4 years ago so who knows if I remember it correctly. Perhaps he said dispersion was better with the dome tweeter, I don't know. It would be interesting to see that same type of graph comparing the on-axis & off-axis frequency responses between the dome & ribbon tweeters used in the ER18. Just looking at the shape of a dome versus the flat plane of a ribbon, it would seem logical to assume the dome would radiate or disperse sounds waves more uniformly but I don't know that to be the case.

Any more "learnin" you can swing my way ?

Thanks-

Dave

 

[Swerd]

It would be interesting to see that same type of graph comparing the on-axis & off-axis frequency responses between the dome & ribbon tweeters used in the ER18.

The graph I showed above is the raw, unfiltered freq response for the ER18 midwoofer. Of course, it will look different once Dennis's crossover filter is added. I don't have that graph. Dennis is highly aware of the imaging created by good off-axis performance, especially in the crossover range, and all his designs take that into account.

Here is a graph from the Salk SongTower, a speaker similar to the ER18 MTM. The differences are it uses 5¼" midwoofers, a ¾" dome tweeter, and a crossover frequency a little under 2.5 kHz. The ER18 MTM response will strongly resemble this.

Two traces are shown, on-axis and 60° off-axis. Below 1 kHz, both traces are close and run parallel to each other. Between 1 and 2 kHz, the 60° trace begins falling off a bit, but the difference is still less than 3 dB. Between 2 and 3 kHz, you can see the two traces get closer and coincide at the crossover frequency. The 60° tweeter response stays close to the on-axis response until it gets above 10 kHz.

Just looking at the shape of a dome versus the flat plane of a ribbon, it would seem logical to assume the dome would radiate or disperse sounds waves more uniformly but I don't know that to be the case.

For speakers, horizontal dispersion matters more than vertical dispersion. What determines a driver's horizontal dispersion is not the shape but the diameter (for a round driver), or horizontal size (for a ribbon tweeter).

If the sound wavelength is larger than the diameter of the driver, the sound disperses widely. A driver begins to beam as the sound frequency gets high enough for the wavelength to be similar to its diameter. As the wavelength gets shorter, the beaming gets more pronounced. That's the theory, the real measurements can differ.

To convert the size in inches to sound wavelength:
Sound travels at 1125 feet/second, or 13,500 inches/second. Divide speed of sound (inches/second) by frequency (Hz) to get wavelength (inches).

13,500 inches/sec ÷ 13,500 Hz = 1 inch​

In theory a 1" dome tweeter disperses sound well as long as its lower than 13.5 kHz. But all speaker makers measure this, and in practice beaming usually begins a bit lower than theory predicts.

 

[David LR]

Swerd-

Thanks again. Very interesting. You know your stuff. Do you also design speakers as well ? Seems like you have the knowledge for it. I've thought about trying my hand at a two-way, but then I read info such as above and I know my knowledge is very lacking. Besides, why even try when people like Jeff Bagby & Dennis Murphy release their designs in the public domain. Then I think, hey, would be fun to try anyway !

I've got 4 VIFA P17-00-08 (now Scanspeak) from a former MTM speaker which the ER18s replaced. I know these drivers are probably twenty years old in design, but, Meniscus is actually selling them again, calling them "The beloved P17WJ", and for more money than I paid originally. Meniscus says that Scanspeak got the machine tooling, etc from VIFA (no longer in business ?) and is now producing again.

The guys at Meniscus said they are still good drivers, not to be thrown away. So, I'm looking for something creative to do with them. They don't have much bass, so my two thoughts were a satellite-sub combo or as part of a three-way system. Any opinions would be welcome.

 

[Swerd]

Thanks again. Very interesting. You know your stuff. Do you also design speakers as well ? Seems like you have the knowledge for it. I've thought about trying my hand at a two-way, but then I read info such as above and I know my knowledge is very lacking. Besides, why even try when people like Jeff Bagby & Dennis Murphy release their designs in the public domain. Then I think, hey, would be fun to try anyway!

I can talk about it, but Dennis can do it. I was interested in trying, but didn't own any of the necessary gear & software. Then I met Dennis Murphy, and decided that I could just ask him and do what he says. I've never been sorry with that.

I've got 4 VIFA P17-00-08 (now Scanspeak) from a former MTM speaker which the ER18s replaced. I know these drivers are probably twenty years old in design, but, Meniscus is actually selling them again, calling them "The beloved P17WJ", and for more money than I paid originally. Meniscus says that Scanspeak got the machine tooling, etc from VIFA (no longer in business ?) and is now producing again.

The guys at Meniscus said they are still good drivers, not to be thrown away. So, I'm looking for something creative to do with them. They don't have much bass, so my two thoughts were a satellite-sub combo or as part of a three-way system. Any opinions would be welcome.

The Meniscus guy is right, the Vifa P17WJ was a classic and was widely used 10-20 years ago. You should ask Dennis Murphy! He may have a good 2-way design for it gathering dust somewhere. If I remember it's sound, it's not bad but not nearly as good as the Seas ER18.

 

[roadrune]

I think to much when im at work....

How about a tapped horn sub to complement the er18s in a HT?

Im thinking something like the LilWrecker as the size would be perfect lying under the screen, and used as shelf for center speaker and electronics.

What do you guys think? Bad idea?

 

[Swerd]

I think to much when im at work....

How about a tapped horn sub to complement the er18s in a HT?

Im thinking something like the LilWrecker as the size would be perfect lying under the screen, and used as shelf for center speaker and electronics.

ER18 MTM speakers have a predicted F3 of 35 Hz and can produce useful sound as low as 31 Hz. Wait until you hear yours in your room at home before thinking about a sub woofer.

Compared to designing good speakers, a good sub is much easier. There are probably many good subwoofer designs around. It is important to remember that a sub's location within a room makes a very big difference in it's sound.

Do you have a link for the LilWrecker?

 

[roadrune]

http://industriumvita.com/folded-tapped-horn-subwoofer-tuned-for-17hz/

My main reason for wanting a sub is not the sound, but the "ounch" and vibration from it

 

[David LR]

You should ask Dennis Murphy! He may have a good 2-way design for it gathering dust somewhere. If I remember it's sound, it's not bad but not nearly as good as the Seas ER18.

Well, I just might. Of course I don't know Dennis Murphy. Not sure he would respond to Joe Blow anonymous speaker builder from internet land, but, all he can do is say no, right ? (or ignore me ).

Thank you-

 

[Swerd]

Well, I just might. Of course I don't know Dennis Murphy. Not sure he would respond to Joe Blow anonymous speaker builder from internet land, but, all he can do is say no, right ? (or ignore me ).

He will respond. And if he still has a design, he will send it.

 

[FingerlessHackWoodworker]

The graph I showed above is the raw, unfiltered freq response for the ER18 midwoofer. Of course, it will look different once Dennis's crossover filter is added. I don't have that graph. Dennis is highly aware of the imaging created by good off-axis performance, especially in the crossover range, and all his designs take that into account.

Here is a graph from the Salk SongTower, a speaker similar to the ER18 MTM. The differences are it uses 5¼" midwoofers, a ¾" dome tweeter, and a crossover frequency a little under 2.5 kHz. The ER18 MTM response will strongly resemble this.

Two traces are shown, on-axis and 60° off-axis. Below 1 kHz, both traces are close and run parallel to each other. Between 1 and 2 kHz, the 60° trace begins falling off a bit, but the difference is still less than 3 dB. Between 2 and 3 kHz, you can see the two traces get closer and coincide at the crossover frequency. The 60° tweeter response stays close to the on-axis response until it gets above 10 kHz.

For speakers, horizontal dispersion matters more than vertical dispersion. What determines a driver's horizontal dispersion is not the shape but the diameter (for a round driver), or horizontal size (for a ribbon tweeter).

If the sound wavelength is larger than the diameter of the driver, the sound disperses widely. A driver begins to beam as the sound frequency gets high enough for the wavelength to be similar to its diameter. As the wavelength gets shorter, the beaming gets more pronounced. That's the theory, the real measurements can differ.

To convert the size in inches to sound wavelength:
Sound travels at 1125 feet/second, or 13,500 inches/second. Divide speed of sound (inches/second) by frequency (Hz) to get wavelength (inches).

13,500 inches/sec ÷ 13,500 Hz = 1 inch​

In theory a 1" dome tweeter disperses sound well as long as its lower than 13.5 kHz. But all speaker makers measure this, and in practice beaming usually begins a bit lower than theory predicts.

Swerd, thank you for the info on beaming!!! The wave length info you passed on also applies to speaker-driver placement according to what I read in "Introduction to Loudspeaker Design" by John L. Murphy. As stated, "It is important to try to keep the acoustic centers of the component drivers as close as possible in multi-way speakers in order to assure smooth frequency response off axis. Here is the goal: space the drivers no further than a distance equal to half the wavelength of sound at the crossover frequency."

 

[FingerlessHackWoodworker]

FingerlessHack:

I have some input here, having been the only builder (as far as I know) to use the Dayton dome verison. When I ordered the kit from Meniscus I had every intention of going with the ribbon version but changed my mind when a Meniscus rep expressed some reservations about too much beaming from the ribbon, so
I chose the dome. In retrospect, I wish I would have chosen the ribbon, not that I have any complaints about the Dayton dome, it sounds great, but I'd never heard a decent ribbon tweeter and still haven't !

As far as beaming goes, Dennis Murphy uses ribbons in his very high-end Philharmonic speakers so I doubt that beaming is a real issue.

Anyway, that's my two-cents worth, hope it helps.

Dave

Dave, what did the kit from Meniscus contain?