Future (active?) recommendations please, for a noob

[jostenmeat]

Makes perfect sense to me Swerd, thanks, not nitpicking at all IMO. TBH, I did at first wonder how less baffle meant less "diffraction loss".

edit: the PDF brought to light something that never occurred to me. My front three are presently raised on cinder blocks, so I am perhaps suffering diffraction loss since it is closer to the idea of 4pi vs 2pi.

Therefore, I have yet discovered another little tidbit that may be upgraded too if I build the ER18s: no more need for stands, and therefore no more diffraction loss than is necessary.


edit #2: Does anyone have a specific forum/subforum to recommend in learning a bit more about active designs? I don't think I'll go that route due to significantly increased costs, but I still want to follow through a little bit on due diligence. Thanks.

 

[Swerd]

Makes perfect sense to me Swerd, thanks, not nitpicking at all IMO. TBH, I did at first wonder how less baffle meant less "diffraction loss".

edit: the PDF brought to light something that never occurred to me. My front three are presently raised on cinder blocks, so I am perhaps suffering diffraction loss since it is closer to the idea of 4pi vs 2pi.

Not sure I understand what you mean. Are you saying that putting your T55 towers on cinderblocks creates a greater baffle step response because they are higher off the floor? Usually when people talk about the 2pi vs. 4pi business they are describing what happens with narrow cabinet speakers (narrower than about 10") as you move them further away from the wall behind them. Closer to the wall gives greater bass, further away gives less bass or greater baffle step response. Because the floor is at right angles to the front baffle, I not sure the same thing applies. But then I haven't thought about this before either.

edit #2: Does anyone have a specific forum/subforum to recommend in learning a bit more about active designs? I don't think I'll go that route due to significantly increased costs, but I still want to follow through a little bit on due diligence. Thanks.

I don't know of any.

 

[jostenmeat]

Swerd, it was my brief attempt at understanding the very beginning of page 2 of the PDF you had linked for me.

It says (going by memory, back and forth):

"The other extreme for measuring speaker performance assumes that the speaker enclosure is suspended and radiating into 4pi space or free space. Free space implies that no reflective surfaces such as a wall, a floor, or a ceiling are close enough to influence the SPL response."

I understand that by raising by speakers only 1ft, that there is surely plenty of boundary interaction. Perhaps mistakenly, I still took that to mean that I might be losing out because of baffle diffraction step.

Anyhoo!

 

[jinjuku]

Swerd, it was my brief attempt at understanding the very beginning of page 2 of the PDF you had linked for me.

It says (going by memory, back and forth):

"The other extreme for measuring speaker performance assumes that the speaker enclosure is suspended and radiating into 4pi space or free space. Free space implies that no reflective surfaces such as a wall, a floor, or a ceiling are close enough to influence the SPL response."

I understand that by raising by speakers only 1ft, that there is surely plenty of boundary interaction. Perhaps mistakenly, I still took that to mean that I might be losing out because of baffle diffraction step.

Anyhoo!

BSC is usually associated with horizontal dispersion. You may be infering ground bounce.

 

[Swerd]

Swerd, it was my brief attempt at understanding the very beginning of page 2 of the PDF you had linked for me.

It says (going by memory, back and forth):

"The other extreme for measuring speaker performance assumes that the speaker enclosure is suspended and radiating into 4pi space or free space. Free space implies that no reflective surfaces such as a wall, a floor, or a ceiling are close enough to influence the SPL response."

I understand that by raising by speakers only 1ft, that there is surely plenty of boundary interaction. Perhaps mistakenly, I still took that to mean that I might be losing out because of baffle diffraction step.

This subject can be difficult to talk about clearly. I'm actually glad to know that you read that pdf file .

I've always understood that the baffle step response varies with the width of the front baffle of the cabinet, and with the distance the speaker is from the wall behind it. You can correct for it (gain lost bass response) by moving the speaker closer to the wall behind.

I suppose the floor and ceiling can have a similar effect, but the floor and ceiling in a room are constant, where the distance between the speaker and the wall behind it is not.

There is another bass effect or problem, called floor bounce. Imagine bass sound coming direct from the speakers to your ears. Bass can also originate from the speaker, bounce off the floor (or ceiling), and arrive at your ears delayed enough to cancel out or add to the sound that takes the direct path. That is why frequency response curves are so uneven below 200 Hz. The distance between the speaker and listener, as well as between the speaker and the floor or ceiling can determine what frequencies are canceled or added to. Raising your speakers higher will change the floor bounce, but a baffle step compensation circuit probably will have little effect.

I hope someone else can weigh in on this.

This also borders on analysis paralysis. Don't worry about floor bounce. Unless you eliminate the floor and ceiling, its always there. We are quite used to hearing it, and may think things sound all wrong if it could be eliminated.

 

[lsiberian]

Every boundary has an effect on sound, but it's nearly always better to isolated speakers/subs from the ground. There are several things things that mess up speakers, but none of them are deal breakers. You can build a speaker without BSC, Zobel, etc and you should probably start with the simple high-pass/low-pass stuff. Then you can add additional things as your heart desires. See if you like it. Remember always do a single speaker first that way if it's a disaster you are only out the cost of a couple drivers.

Remember building good speakers is easy, building great speakers is hard. You only need wood drivers and a simple crossover to build a good speaker. For a great speaker you want a great crossover, quality materials, bracing, damping, shrink, shed, patience, small fortune, first aid kit. You get the idea I hope.

If you'd like to try the RB Kit I'd be willing to pull the drivers(not sure if I can get the crossover out) and send them to you. I even got 4 spare bottoms if you want to go MTM at some point. I need a swift kick to finish the tiger towers.

 

[jinjuku]

There is another bass effect or problem, called floor bounce. Imagine bass sound coming direct from the speakers to your ears. Bass can also originate from the speaker, bounce off the floor (or ceiling), and arrive at your ears delayed enough to cancel out or add to the sound that takes the direct path. That is why frequency response curves are so uneven below 200 Hz. The distance between the speaker and listener, as well as between the speaker and the floor or ceiling can determine what frequencies are canceled or added to. Raising your speakers higher will change the floor bounce, but a baffle step compensation circuit probably will have little effect.

That is why most straight up RTA's suck at adjusting for bass levels. You need something like the SMS-1 or an active speaker management system, REW and a human manning the controllers.

 

[Swerd]

There are several things things that mess up speakers, but none of them are deal breakers.

Its alway good to remember this when Analysis Paralysis (also known as Audio Nirvana Nervosa) threatens .

 

[jostenmeat]

Well, I think we should put the BSC on the backburner then, haha. I didn't read the entire PDF, but only some of it. I made the connection with BSC because I assumed it was the primary topic of the PDF; I must then simply be confusing the meaning/implication of 4pi space.

I do plan on attempting to devour the awaited speaker book, which I ordered from Amazon, but there is no tracking number/date, probably due to book rate snail mail.

Quick question regarding floor bounce, though. Is it true that an unideal horizontal MTM center speaker can be superior in terms of limiting floor and/or ceiling bounce? How does that work?

And thanks Swerd for sending the PDF! I am glad I started to research the possibility of building speakers as soon as I finished my last project, because I can see there is plenty of due diligence to follow through on. Thanks everyone.

I have diagnosed myself to have chronic audio/video nervosa.

 

[Swerd]

Quick question regarding floor bounce, though. Is it true that an unideal horizontal MTM center speaker can be superior in terms of limiting floor and/or ceiling bounce? How does that work?

I realize (now) that much of what you are asking in this thread is really you thinking out loud. Nothing wrong with that. In fact, I think the AH DIY forum exists for just these kind of posts.

But sometimes when you word it as a direct question, I feel obligated to answer, or at least try.

For your above question, I don't have a clue. I've never even heard such a thing said before .

To go back to the subject of speaker cabinet diffraction, Jeff Bagby, an accomplished speaker designer who often writes thoughtfully and intelligently on various subjects, has an article titled Understanding Cabinet Diffraction.

It appears, along with a number of other interesting articles about speaker design and audio, on Salk Signature Sound's Audioblog page. They're all good reads.

 

[jostenmeat]

Thanks for the first link! I look forward to reading that in the future.

Per usual, I was going on mistaken and long term memory regarding floor bounce (I remember a short discussion elsewhere from about 2 years ago, which might be the only* time I've read anything about it . . . )

So, the D'Appolito config will reduce floor/ceiling bounce, without affecting horiz dispersion, but when flipped on its side as a horiz MTM, you get more of that bounce back. (The wording of the poster from two years ago was a bit confusing, and hence my misremembering.) Sorry, and thanks.

I make you scratch your head, wonder out loud back to me, so then I look further into it and then I learn something. Sorry if I ever give you any mental duress or discomfort!

 

[jostenmeat]

I just took the time to read every word of the diffraction article, as well as the ER18 instructuctions. I'm just regurgitating here. Yes, I'm thinking out loud again!

I am assuming that when I am reading what the author says in terms of "baffle width", that I should more specifically be thinking in terms of distance from driver to edge. I assume it is just easier for the author to describe baffle width in the beginning where all of us assume symmetrical driver placement, particularly since he hasn't yet spoken of the solution of the offset tweeter. Please correct me if I am wrong, as I just want to be redundantly sure. Of course, for the woofers in the ER18, baffle width (or specifically half of), and distance to edge can now be synonymous.

I now understand why my PSBs have rounded/radiused baffles!

I wonder if there are any speakers that do all* of the following: rounded baffle, felted baffle, and offset tweeter placement, heh. I wonder why felt isn't used more since most speakers are used with grilles over them.

The paragraph that hurt my head the most was the second paragraph after the triangle diagram, basically the part that describes how half of the full wavelength (of baffle width) will combine constructively, but that the full wavelength direct to edge (half baffle width) will produce the notch. Yeah, it hurt my head, but I think I got through it. I imagine with so many varying distances to baffle edge, and therefore so many half and full wavelengths, one could blow his brain up figuring it all out. I guess roundover bits, rounded baffles, offset drivers, felt, and flush mounted drivers all help so that the ANACIN remains in the medicine cabinet.

What I haven't got my head around is the beginning of the last paragraph:

For most speakers what is known as “baffle step” is usually best handled in the crossover. It is possible to avoid this step altogether in a three way system if the woofer is placed close to the floor and the crossover point is carefully selected. This allows boundary reinforcement to fill in part of the step.

Part of the step? BSC . . . does it imply correction not only for the step, but also for frequencies where the baffle is considered to be "acoustically invisible"? Or am I confused, and perhaps I am supposed to consider frequencies "below the step" to be in fact still part of the "step"? The third possibility is that I have my definition of "step" to be correct, but that BSC assumes correction for all of the above? Oh I don't know, humbug.

Am I wrong here, or are huge baffles the WTG? If we had huge baffles, do we lose out on offaxis response, in that all of the energy is now towards the listener by 6db (or up to the theoretical 9db) since it is no longer radiating into 4pi (or 2pi or whatever)? I suppose there is a threshold of baffle size where it may "sound like offaxis", but perhaps that might have to be an infinite baffle. I am wondering out loud.

Oh boy, half knowledge is the worst knowledge!


Regarding the ER18s, if I accept to choose this mission, I think I will lean towards easy as possible (they would be my first DIY speakers). As in no baffles, no internal dados at .75" wide (which add up to 24 times for me), no finish, no feet, and no grilles! I was a little surprised at the 2" depth of of the braces directly behind the woofer (even when I know the baffle is .75" thick), but I'm sure it is enough if that's what it said. Maybe I'll add felt.

Swerd, did you produce these instructions yourself? I mean outside of basic numbers given to you . . you did the shopping list, diagrams, etc? Well, to all of those who contributed, this is really great, kudos.

 

[Swerd]

I am assuming that when I am reading what the author says in terms of "baffle width", that I should more specifically be thinking in terms of distance from driver to edge. I assume it is just easier for the author to describe baffle width in the beginning where all of us assume symmetrical driver placement, particularly since he hasn't yet spoken of the solution of the offset tweeter. Please correct me if I am wrong, as I just want to be redundantly sure. Of course, for the woofers in the ER18, baffle width (or specifically half of), and distance to edge can now be synonymous.

You might be complexifiying things a bit. Usually the term "baffle width" means the external cabinet width. In the ER18 MTM, that is 9". The distance from the center to the baffle edge is 4½". The woofers are mounted centered, and the tweeter is offset ¾" from the center.

I wonder if there are any speakers that do all* of the following: rounded baffle, felted baffle, and offset tweeter placement, heh. I wonder why felt isn't used more since most speakers are used with grilles over them.

You left out flush mounting the tweeter and woofer, so its edges don't protrude from the front baffle and create a new edge for diffraction.

Felt is difficult to mount so it doesn't peel back at the edges, and I think it looks cheesy.

Dennis Murphy said that if he had to rank these anti-diffraction tweaks, he'd put flush-mounted drivers first, offset tweeters and rounded baffle edges tied for second, and felt a distant fourth. He hasn't seen a case where using felt made measurable improvements to the frequency response curve if the others were done first.

The paragraph that hurt my head the most was the second paragraph after the triangle diagram, basically the part that describes how half of the full wavelength (of baffle width) will combine constructively, but that the full wavelength direct to edge (half baffle width) will produce the notch. Yeah, it hurt my head, but I think I got through it. I imagine with so many varying distances to baffle edge, and therefore so many half and full wavelengths, one could blow his brain up figuring it all out. I guess roundover bits, rounded baffles, offset drivers, felt, and flush mounted drivers all help so that the ANACIN remains in the medicine cabinet.

There are two levels of understanding. The first is knowing that these cabinet modifications make a difference in the frequency response curve. If you could see before and after FR curves, you would easily get it. The second level is understanding why it makes a difference. To build the cabinets, you don't really need to understand why, but you do have to accept the idea that it does make for a smoother FR curve. I know my advice says "just take it on faith" and is contrary to the usual AH mantra. But if understanding it gives you a headache, have faith that this advice is based on sound practice and is not voodoo.

What I haven't got my head around is the beginning of the last paragraph:

For most speakers what is known as “baffle step” is usually best handled in the crossover. It is possible to avoid this step altogether in a three way system if the woofer is placed close to the floor and the crossover point is carefully selected. This allows boundary reinforcement to fill in part of the step.

Part of the step? BSC . . . does it imply correction not only for the step, but also for frequencies where the baffle is considered to be "acoustically invisible"? Or am I confused, and perhaps I am supposed to consider frequencies "below the step" to be in fact still part of the "step"? The third possibility is that I have my definition of "step" to be correct, but that BSC assumes correction for all of the above? Oh I don't know, humbug.

Yes you seem to be confused. Think of a FR curve where we usually look from left to right, from low frequency to high frequency. The "baffle step" is an increase of about 3-6 dB in the FR curve that begins at around 500-1000 Hz. If you use the term "diffraction loss", think of the frequencies below 500 Hz as suffering a 3-6 dB loss in SPL. It is a gradual increase (or loss), and not really step shaped. But the SPL does increase (as you look left to right on a FR curve), and therefore is spoken of as "stepped up".

The increased midrange (baffle step response) or decreased bass (diffraction loss) that occurs in the lower midrange, is best corrected by some equalization that gets built into the crossover. This is often called a baffle step compensation (BSC) circuit. This matters more in a 2-way speaker. In a 3-way, the designer can simply use resistors to lower the midrange and tweeter response relative to the woofer.

Am I wrong here, or are huge baffles the WTG? If we had huge baffles, do we lose out on offaxis response, in that all of the energy is now towards the listener by 6db (or up to the theoretical 9db) since it is no longer radiating into 4pi (or 2pi or whatever)? I suppose there is a threshold of baffle size where it may "sound like offaxis", but perhaps that might have to be an infinite baffle. I am wondering out loud.

Your thoughts about using huge baffles means you really do understand all this . The ultimate huge baffle would be speakers flush-mounted in a wall. This is called Infinite Baffle, or IB. There are good reasons why you wouldn't want to do this for most of the audio frequency range (lost off-axis response that you mentioned), but for bass, this can work well. IB subwoofers, if done right, can sound great.

Regarding the ER18s, if I accept to choose this mission, I think I will lean towards easy as possible (they would be my first DIY speakers). As in no baffles, no internal dados at .75" wide (which add up to 24 times for me), no finish, no feet, and no grilles! I was a little surprised at the 2" depth of of the braces directly behind the woofer (even when I know the baffle is .75" thick), but I'm sure it is enough if that's what it said. Maybe I'll add felt.

You said "no baffles". Did you mean "no rounded baffles"?

Internal dados for installing the cross braces are nice, but not necessary. skyline_123 didn't use them. He butt mounted them and added screws to hold them while the glue dried. If you have a friend with a table saw or router, dados should be easier for him to make.

Swerd, did you produce these instructions yourself? I mean outside of basic numbers given to you . . you did the shopping list, diagrams, etc? Well, to all of those who contributed, this is really great, kudos.

Yes. I wrote it and made the diagrams and tables. Paul Kittinger designed the cabinet and provided all those nice graphs of the predicted bass performance. Dennis Murphy chose the woofers and both tweeters, and designed the crossovers. I chose the crossover parts based on Dennis Murphy's designs. I heard a prototype where Dennis Murphy used those drivers mounted in an unfinished Salk HT2-TL cabinet which has nearly identical dimensions. As far as I know, skyline_123 is the first to build them.

 

[Swerd]

To further explain baffle step response, a picture is worth a thousand words.

Here are FR curves of two small 2-way speakers. They are well-known and will remain unidentified. You can find these, and FR curves of many other well-known speakers here

First example

Second example

In both, if you start looking at about 100 Hz, the SPL is in the mid to upper 80 dB level. As you increase frequency (look from left to right), at roughly 500 Hz the SPL "steps up" about 3 or 4 dB higher. As you go to about 2,000 Hz, the SPL and drops back down a bit. Example 1 is a bit smoother across this region than example 2.

This is classic baffle step response, or diffraction loss. In both examples, they don't look to me like they are corrected by the manufacturers.

If you are not used to looking at these FR curves, the difference in SPL of the stepped-up region may look small, but this occurs in right in the middle of the voice-discrimination audio region. Our ears are very sensitive to small changes here. You will definitely hear these differences.

 

[jostenmeat]

You might be complexifiying things a bit. Usually the term "baffle width" means the external cabinet width. In the ER18 MTM, that is 9". The distance from the center to the baffle edge is 4½". The woofers are mounted centered, and the tweeter is offset ¾" from the center.

Well, I believe I understand all of this. Thanks for trying there. Hm, maybe I'll try to pose a more distilled question.

Am I correct that baffle width is immaterial to diffraction effects, because the driver might be placed at any point between two edges; that only the direct segment between the driver and any particular point on an edge is what matters? I would bet money that I am correct, but like I said, I just wanted to be redundantly sure.

You left out flush mounting the tweeter and woofer, so its edges don't protrude from the front baffle and create a new edge for diffraction.

I realized that.

Felt is difficult to mount so it doesn't peel back at the edges, and I think it looks cheesy.

The author did address the latter, but that's why I was bringing up the point of grilles. I bet 9 out of every 10 AHers leave the grilles on.

Dennis Murphy said that if he had to rank these anti-diffraction tweaks, he'd put flush-mounted drivers first, offset tweeters and rounded baffle edges tied for second, and felt a distant fourth. He hasn't seen a case where using felt made measurable improvements to the frequency response curve if the others were done first.

Very interesting!

There are two levels of understanding. The first is knowing that these cabinet modifications make a difference in the frequency response curve. If you could see before and after FR curves, you would easily get it. The second level is understanding why it makes a difference. To build the cabinets, you don't really need to understand why, but you do have to accept the idea that it does make for a smoother FR curve. I know my advice says "just take it on faith" and is contrary to the usual AH mantra. But if understanding it gives you a headache, have faith that this advice is based on sound practice and is not voodoo.

I'm pretty sure I understand all of the concepts in the article, except for that part I quoted, in terms of nomenclature, and perhaps the presumed application(s).

I understand the "plateaus" and the "rise".

Yes you seem to be confused. Think of a FR curve where we usually look from left to right, from low frequency to high frequency. The "baffle step" is an increase of about 3-6 dB in the FR curve that begins at around 500-1000 Hz. If you use the term "diffraction loss", think of the frequencies below 500 Hz as suffering a 3-6 dB loss in SPL. It is a gradual increase (or loss), and not really step shaped. But the SPL does increase (as you look left to right on a FR curve), and therefore is spoken of as "stepped up".

Then I did have my definitions correct. What I want to know is if, and how much, BSC in a xover corrects for the lower plateau. I suppose there is a limit to what one can do anyhow, depending on the ability of the driver to begin with, and any port/cabinet tuning. I guess I should in the end presume that a 3way is truly "full range", perhaps.

The increased midrange (baffle step response) or decreased bass (diffraction loss) that occurs in the lower midrange, is best corrected by some equalization that gets built into the crossover. This is often called a baffle step compensation (BSC) circuit. This matters more in a 2-way speaker.

Right.

In a 3-way, the designer can simply use resistors to lower the midrange and tweeter response relative to the woofer.

Now this was something I was wondering about (but not necessarily with 3ways only). So, can this technically still be called BSC, or is it not as your post might have me infer? Well, thanks for addressing this thing I was wondering about before it even came out of my mouth . . .

In which case would we choose to depress the HF rather than increase the LF? I would imagine, offaxis response aside, that to use the natural "sensitivity" would be in our benefit? That all extra amplification towards boosting would be a better goal than to waste the energy in resistors? Thanks. I never understood electricity, so forgive me for any gross misunderstandings.

Your thoughts about using huge baffles means you really do understand all this . The ultimate huge baffle would be speakers flush-mounted in a wall. This is called Infinite Baffle, or IB. There are good reasons why you wouldn't want to do this for most of the audio frequency range (lost off-axis response that you mentioned), but for bass, this can work well. IB subwoofers, if done right, can sound great.
You said "no baffles". Did you mean "no rounded baffles"?

Sorry, I meant the extra outer front baffle. (I didn't ask it last night, but well, I presume the extra diffractions created are to be insignificant with said outer baffle?)

Internal dados for installing the cross braces are nice, but not necessary. skyline_123 didn't use them. He butt mounted them and added screws to hold them while the glue dried. If you have a friend with a table saw or router, dados should be easier for him to make.

You said butt. j/k

Yes. I wrote it and made the diagrams and tables. Paul Kittinger designed the cabinet and provided all those nice graphs of the predicted bass performance. Dennis Murphy chose the woofers and both tweeters, and designed the crossovers. I chose the crossover parts based on Dennis Murphy's designs. I heard a prototype where Dennis Murphy used those drivers mounted in an unfinished Salk HT2-TL cabinet which has nearly identical dimensions. As far as I know, skyline_123 is the first to build them.

Well, congratulations on an excellent set of instructions. The diagrams make it sooo much easier to picture, because well it's all pictured already.

The shopping list is a huge convenience as well.

I found it interesting that the various modeled port speeds were so moderate (not that I have any point of reference), if between 1-3% higher than the speed of sound.

If you noted the myriad of my proposed shortcuts, none of them are to sacrifice performance (and perhaps the laziness of excluding the outer front baffle might even increase measured performance). The above said, I hope I can somehow find the 24.7uf caps, even if the improvement is only measurable and not audible (as I would choose the Dayton tweeters for better vertical response).

 

[Swerd]

Everytime I answer a question, you ask 10 more . When am I going to learn?

Am I correct that baffle width is immaterial to diffraction effects, because the driver might be placed at any point between two edges; that only the direct segment between the driver and any particular point on an edge is what matters? I would bet money that I am correct, but like I said, I just wanted to be redundantly sure.

Yes, you are correct.

Dennis Murphy said that if he had to rank these anti-diffraction tweaks, he'd put flush-mounted drivers first, offset tweeters and rounded baffle edges tied for second, and felt a distant fourth. He hasn't seen a case where using felt made measurable improvements to the frequency response curve if the others were done first.

I forgot to add something important about this. When a speaker is designed, you first build the cabinet and mount the drivers, and then design the crossover. All the measurements necessary for designing the crossover are done with the woofer and tweeter mounted on the cabinet. So features like baffle width, tweeter offset, rounded edges, presence or absence of felt are there before crossover design. Changing any of those features, after crossover design, might not be an improvement. For the ER18 MTM (both versions with different tweeters), the crossovers were designed with flush-mounted drivers, rounded edges and offset tweeter, but no felt was used. If you leave out the rounded cabinet edges because you don’t have the right tools, it will make a small difference, but not a major one.

I understand the "plateaus" and the "rise"…

Then I did have my definitions correct. What I want to know is if, and how much, BSC in a xover corrects for the lower plateau. I suppose there is a limit to what one can do anyhow, depending on the ability of the driver to begin with, and any port/cabinet tuning. I guess I should in the end presume that a 3way is truly "full range", perhaps.

Understand that BSC, or any other type of filter or equalization by a passive crossover, can only lower the response. It cannot raise a plateau. In the examples I showed, BSC would lower the raised portion, roughly 500 – 2000 Hz, by 3 to 4 dB, so that region would be the same level as the sound below 500 Hz. You gain by getting a flatter FR, but pay for it by getting lower sensitivity.

Yes you might be able to accomplish this by lowering the response of the tweeter with resistors. But in many 2-ways, the tweeter may not kick in until above 2,000 Hz. The raised baffle step is below that, starting at 500 Hz. So padding down the tweeter won’t really get you a flatter FR curve.

Sorry, I mean the extra outer front baffle. (I didn't ask it last night, but well, I presume the extra diffractions created are to be insignificant with said outer baffle?)

The outer front baffle that I drew into the diagrams is optional. You can leave it out for a simpler build. It is my way to do the rounded edges on a smaller piece than the entire front of the cabinet, and also provides a thicker piece of wood to support the screws holding the woofers. But since you asked, it is not needed for acoustic reasons.

Don’t worry about finding 24.7 µF caps, I don't think they exist. A 25 µF cap is fine. Remember that ±10% applies to crossover parts. So if the spec says 24.7 µF, anything from 22.2 to 27.2 µF will do.

 

[jostenmeat]

Everytime I answer a question, you ask 10 more . When am I going to learn?

If you ever ask a question, and I happen to know something you don't, of course I will help. It's just that day might never come.

I forgot to add something important about this. When a speaker is designed, you first build the cabinet and mount the drivers, and then design the crossover. . . *snip*

Makes sense to me. On a side note, as I forgot to mention it, my PSBs baffle at the tweeter is all dimpled. I figure it must be for diffraction's sake.

Understand that BSC, or any other type of filter or equalization by a passive crossover, can only lower the response. It cannot raise a plateau. In the examples I showed, BSC would lower the raised portion, roughly 500 – 2000 Hz, by 3 to 4 dB, so that region would be the same level as the sound below 500 Hz. You gain by getting a flatter FR, but pay for it by getting lower sensitivity.

Yes you might be able to accomplish this by lowering the response of the tweeter with resistors. But in many 2-ways, the tweeter may not kick in until above 2,000 Hz. The raised baffle step is below that, starting at 500 Hz. So padding down the tweeter won’t really get you a flatter FR curve.
The outer front baffle that I drew into the diagrams is optional. You can leave it out for a simpler build. It is my way to do the rounded edges on a smaller piece than the entire front of the cabinet, and also provides a thicker piece of wood to support the screws holding the woofers. But since you asked, it is not needed for acoustic reasons.

AH-HA! This portion has really enlightened me, and things have really become much clearer to me now in terms of practical application.

Don’t worry about finding 24.7 µF caps, I don't think they exist. A 25 µF cap is fine. Remember that ±10% applies to crossover parts. So if the spec says 24.7 µF, anything from 22.2 to 27.2 µF will do.

Ok, thanks. I like having less things to worry about.

 

[lsiberian]

Seem like JM is really starting to get it. Just don't forget there are 12 inches in a foot not 10. This one always seems to get me toward the end of a cutting session.

 

[jostenmeat]

I'm sorry if I missed it, but can someone tell me what kinds of crossovers these speakers use, particularly when using the Dayton tweeter (though I'm interested in both)? As in type/slope as well as xover point? Thanks.

With the above information, can someone describe a little bit the compromise of having the ears be off-axis on the vertical plane, in terms of lobing/cancellations? I think I could get all listeners to be within +/- 3 deg offaxis, and if I don't replace my present cinder blocks, it would be a hair less than 4 degrees for front row, and closer to something like a little over 2 degrees for the rear row. Thanks, just want to try to cover as many bases as possible, and to make sure that I'm not barking up the wrong tree in terms of speaker choice out of the vast selection out there. I'm sure with such small angles, that I will be perfectly fine, but I guess for a sloucher, we could be looking at 5-6 deg.

The biggest thing that will hold me back with this is the outlay for all of the tools, I think. But, it's pretty fun to think about, and learn in the meanwhile. Thanks again.

 

[Swerd]

I'm sorry if I missed it, but can someone tell me what kinds of crossovers these speakers use, particularly when using the Dayton tweeter (though I'm interested in both)? As in type/slope as well as xover point? Thanks.

The crossovers of the ER18 MTMs are 4th order Linkwitz/Riley type. And by 4th order, I mean that the measured acoustic response of the drivers rolls-off at about 24 dB per octave, within an octave of the crossover point.

If anyone, looking at the crossover schematics, feels compelled to say "no way that these crossovers are 4th order", I will remind them that the no one hears the electrical transfer function of the crossover . We hear the drivers producing the music signal as it passes through the crossover.

I don't remember the exact crossover points. With the dome tweeter, I think its 2000 or 2200 Hz, and with the ribbon, its a bit higher, maybe 2500 Hz.

With the above information, can someone describe a little bit the compromise of having the ears be off-axis on the vertical plane, in terms of lobing/cancellations? I think I could get all listeners to be within +/- 3 deg offaxis, and if I don't replace my present cinder blocks, it would be a hair less than 4 degrees for front row, and closer to something like a little over 2 degrees for the rear row. Thanks, just want to try to cover as many bases as possible, and to make sure that I'm not barking up the wrong tree in terms of speaker choice out of the vast selection out there.

With my SongTowers, 48" tall MTM speakers (including the base and the spiked feet), if I stand up, putting my ears above the main MTM axis, the speakers sound a little less bright. That is, the balance between bass and treble becomes a bit warmer. It doesn't sound bad either way, just a bit different. And that is with familiar music. With movies, I doubt if I would notice.

I think sweating over ± a couple of degrees might be an early onset symptom of Audio Nirvana Nervosa . Being slightly above or below the optimum level will not make Frank Sinatra sound like Barry Manilow. No one, other than you, will notice or care .