Building the best loudspeakers

[ScottG]

Originally posted by Ceibal



I am really set on a closed design. Would this woofer work in that setup? Looks to have to low of a QTS according to what I am reading.

Wanting everything and ultimately ending up with nothing.. This is where you REALLY need to study-up.

Short answer - No.

[ScottG]

Originally posted by ShinOBIWAN


Parts Express have the Usher on special at $89 so that's a good call Scott.

I'm not sure about the Neo 3 PDR but no denying its low distortion. For the tweeter I'd look at the new Seas 27TBCD/GB-DXT or as its more easily remembered part number of H1499. In particular is its impressively linear off axis response and the ability to cross fairly low - I'd imagine 1.5Khz to be no real problem for everyday use. This would be a boon for a 2-way MTM. I'm particularly interested in trying out this tweeter for myself.
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The Neo 3 pdr will provide some of that magic (like the RAAL), that isn't easily "seen". In this case its enclosure volume is fairly critical - other wise it becomes overdamped (if its to large), and you loose that magic (..and you might as well look at something like the Seas at that point).

[ScottG]

Originally posted by Ceibal



Is there a good way to figure out if a woofer will work best in a sealed enclosure or vented? Or, is it just one of those things you just have to try it and see if it works.

..modeling will give you some idea of bass extension.

[sreten]

Hmmm.....

This is one of those threads where the poster knows the names of
some good drivers and has no idea what he does not know about
speaker design but wants the "best".

FWIW electrical engineers generally (my degree) understand
some aspects of loudspeakers and generally next to nothing
about acoustics and physics and its applicability to good design.

The suggested process :

So, I will be taking some time to figure out which driver to go with first for this box I have chosen, then comes the tweeter. Once I have accomplished that I will work my way into the crossover, hopefully by then I can get my TI buddy to sit down and help me do the math. It appears I have a long way to go before I can even start to build this set of speakers. I am not worried about the money so long as I accomplish my goal.

Is simply not the way to do it.

http://www.rjbaudio.com/Audiofiles/FRDtools.html
http://www.geocities.com/woove99/Spkrbldg/

http://www.troelsgravesen.dk/Diy_Lou...r_Projects.htm
http://www.humblehomemadehifi.com/
http://www.rjbaudio.com/projects.html
http://www.zaphaudio.com/

/sreten.

I really dislike any threads with "best" in the title, I usually ignore them.

[ShinOBIWAN]

Originally posted by ScottG



The Neo 3 pdr will provide some of that magic (like the RAAL), that isn't easily "seen". In this case its enclosure volume is fairly critical - other wise it becomes overdamped (if its to large), and you loose that magic (..and you might as well look at something like the Seas at that point).

Can't argue with that.

[ScottG]

Originally posted by sreten
Hmmm.....

This is one of those threads where the poster knows the names of
some good drivers and has no idea what he does not know about
speaker design but wants the "best".

FWIW electrical engineers generally (my degree) understand
some aspects of loudspeakers and generally next to nothing
about acoustics and physics and its applicability to good design.

The suggested process :
Is simply not the way to do it.

Exactly.

The real problem however is that it a re-occurring theme.

With the exception of naïveté with regard to bass extension vs. enclosure volume (sealed vs. vented), what he wants (the end result, NOT a sealed design and some boutique parts selection) is actually do-able at a reasonable price - but I don't know of such a design and I'm not sure there even is one.

Sadly it makes me want to do such a design, BUT I know that I neither have the time nor will I spend the cash on something that I know is no longer what *I* really want.

So the best I can do is offer up a fairly quick suggestion of what I think that person should do based on a guess that *belies* just how much knowledge goes behind that suggestion.

....

What I think is particularly ironic here is that Shin has questioned me on the selection of the Neo 3 pdr. (..don't mind the questioning, but I do appreciate the irony. )

It wasn't *that* long ago when he went through something not altogether dissimilar to this poster's dilemma. While he avoided many of the crossover issues by going digital, there were still many costly driver swaps that occurred - driver swaps well beyond the financial abilities of most DIY'ers.

For most people then in a similar situation it means buying these drivers and being stuck with them and no viable loudspeaker (..i.e. the "wanting everything and ending up with nothing").

And seemingly the pinnacle of this "diy driver bane" are the Seas EXCEL magnesium drivers.

Superbly designed,
Superb measurements,
Good looks,
Detailed sound,

..oh, and ultimately worthless for long term enjoyment (..funny how this just doesn't seem to get through )

-and so we go round and round again.

[ScottG]

Originally posted by ShinOBIWAN


Can't argue with that.

Well, you can.. Hell, I might even.

But I've been putzing with my neo 8's getting a "feel" for them - presumably if they are anything like the neo 3's then my statement *should* hold.

(note that the overdamped nature actually works fairly well when they are in a dipole config. for some reason.)

(..though of course there are no absolutes and I ALWAYS reserve the right to be wrong. )

[ScottG]

Because I thought it was a bit hinky with respect to volume - I went back and actually *looked* at the internal volume of that cabinet..

Net internal = 1/2 cubic foot.

At *that* point you might as well have a sealed system. Because with 2 drivers around 7 inches in diameter you are simply not going to get much bass near the reference level regardless of the design.

*IF* you actually had about a cubic foot internal, well then there would be something more to "play" with.

To get more bass look at the offerings in the 5-5.5 inch driver range, OR go back to the *non*-curved side panel box.

i.e THIS is the box that has 1 cubic foot internal:

http://www.partsexpress.com/pe/showd...number=302-750

[ShinOBIWAN]

Originally posted by ScottG
What I think is particularly ironic here is that Shin has questioned me on the selection of the Neo 3 pdr. (..don't mind the questioning, but I do appreciate the irony. )

I questioned it out of the need for a tweeter that could cross low in a 2-way MTM. I tried such things with the LGT, running both the mids to 1.5Khz and all sorts of other frequencies. The depth of the soundstage and particularly the height just callopses the higher you go. I quickly went back to the original 0.5way on one of the mids.

So, to me, the 2Khz you suggested doesn't really do the job and 1.5Khz looks do-able with the Seas and with a fairly nice power response too.

Just in case your interested you read more info on DXT waveguides here:

http://www.dxt.dk/pages/webside.asp?...menuGuid=15288

They also do one off work for the more adventurous DIY'er.

It wasn't *that* long ago when he went through something not altogether dissimilar to this poster's dilemma. While he avoided many of the crossover issues by going digital, there were still many costly driver swaps that occurred - driver swaps well beyond the financial abilities of most DIY'ers.

Fun times. Think it was around three bass drivers before I was finally content. Some projects just work out like that, especially if you don't want to compromise much. If the individual drivers aren't working well together then eventually you have to swap something out. Sadly this can only really be done with real listening rather than modelling and can, as you pointed out, turn expensive. I expect I'll go through a similar situation in a future project, on the flip side the last design I built worked straight away - nothing to change.

BTW You never avoid crossover issues just by using digital. In fact that presents some different problems to consider. Any flaws in the loudspeaker design will still be apparent if the thing itself isn't thought through correctly. Digital does bring additional flexibility and speed to the crossover design process.

[ScottG]

Originally posted by ShinOBIWAN


I questioned it out of the need for a tweeter that could cross low in a 2-way MTM. I tried such things with the LGT, running both the mids to 1.5Khz and all sorts of other frequencies. The depth of the soundstage and particularly the height just callopses the higher you go. I quickly went back to the original 0.5way on one of the mids.

So, to me, the 2Khz you suggested doesn't really do the job and 1.5Khz looks do-able with the Seas and with a fairly nice power response too.


BTW You never avoid crossover issues just by using digital. In fact that presents some different problems to consider. Any flaws in the loudspeaker design will still be apparent if the thing itself isn't thought through correctly. Digital does bring additional flexibility and speed to the crossover design process.

While I could be wrong, I don't think you would find that problem with the neo 3 pdr and the Ushers and a well "sorted out" crossover. (Note that it doesn't have to be 2 kHz - THAT was just what Dennis had applied for his "plop-in-the-box" part deux.) In particular the Ushers (excepting that resonance at 6+k that needs to be notched out), are not terribly extended. As such midbass combing should be low with an LR - 6db base lowpass. Moreover the neo drivers are strange beasties, lots of emmisive area and a small enclosure volume allows you the ability to cross at *oddly* low freq.s - so long as you can sum flat with the midbass drivers. Even 1.5 should be OK with these drivers - its just a matter of summing with the midbass then (..and excepting a certain loss in ultimate spl). (..the things the Neo 8 will do with a small chamber are just plain WEIRD.)

On the other hand though, no they certainly won't be the equal of the RAAL's (not even close).. but like any really good driver they should have that certain magical quality about them that isn't currently measurable/quantifiable.

I'd strongly disagree about avoiding issues with going digital on the crossover. Number one: complexity and learning. Being able to make all sorts of adjustments "on the fly" allows for so much more flexibility, speed, and ease of learning with respect to prototyping a given design. Its also a LOT less expensive (unless you hit upon something outstanding to begin with). Number two: a passive crossover is another resonant load on the amplifier - it will play a substantial role in the overall sound of the finished design without respect to its intended purpose.

..yeah, no date tonight -

(..its been my experience that dates on and around valentines day are just plain baaaaaaaddddd news, well maybe not initially - but they always end-up very bad. )