Can modern large woofers produce midrange ?

[ligs]

Intuitively, I don’t think a 12 inch woofer can reproduce midrange properly due to the large cone diameter which limits the dispersion at the higher end.

However, the widely popular JBL L-100 has a woofer/midrange crossover at around 3.5k Hz. I never owned JBL L-100 but I recently acquired a pair of Pioneer HPM100 which was designed by the same designer, Bart Locanthi, who also was the one behind JBL L-100 and later involved in the TAD division of Pioneer. http://en.wikipedia.org/wiki/Pioneer_HPM-100

The woofer/midrange crossover of Pioneer HPM 100 is about 3k Hz and uses a 12 inch graphite-reinforced woofer. Upon auditioning, HPM’s have a very clean and clear midrange with an overall fairly light balance without any thickness in sound. I seldom have seen any recent speaker designs from PE which lets a 12 inch woofer run that high up as JBL L100 and Pioneer HPM100. Are wide-band large-diameter woofers no longer available?

[Sydney]

Re: Can modern large woofers produce midrange ?

Intuitively, I don’t think a 12 inch woofer can reproduce midrange properly due to the large cone diameter which limits the dispersion at the higher end.

Yup - the Ka works against it.
A work around is create/use separate radiating area or device for the shorter wavelengths.

[ligs]

Re: Can modern large woofers produce midrange ?

A talented speaker designer can probably work around the physical limitations of the drivers and still create a good sounding speaker. Yet I wonder for someone in the enviable position to make any drivers from the scratch if there is any inherent advantage to use one single driver to cover the widest frequency possible? Say from the bass all the way to 3k Hz or higher?

[Sydney]

Re: Can modern large woofers produce midrange ?

I remember there were a lot of L-100's around in the 70's. I certainly heard a lot of them - but that was a long time ago as a frame of reference.
Used as a studio monitor ( listening on-axis ) the off-axis dispersion wasn't an issue

I've not heard a single cone full range large woofer that had respectable off-axis response at mid and high frequency ONLY co-ax ( ie separate tweeter center mounted )

One of my favorite links

http://www.acs.psu.edu/drussell/Demos/BaffledPiston/BaffledPiston.html

[Sydney]

Re: Can modern large woofers produce midrange ?

It just occurred to me...
Are you talking about the JBL L100 that was a 3 way?
It had a crossover from the woofer to the LE-5 5"cone mid of 800Hz and 5Khz* to the LE25 tweeter ( 12db ) so it's somewhat moot to talk about the woofer response @ 3.5KHz - it's in the range of the cone mid.

* BTW PE has a Jantzen Crossover Kit Pair for JBL L100 Century that lists those xover values - I've seen some subtle variances.

[rhubarb9999]

Re: Can modern large woofers produce midrange ?

FYI, the woofer on the L-100/4311/4312 runs wide open .. so it goes as high as the natural roll off of the driver. I think the crossover to the mid varied depending on the model. There was also a level control for both the mid and tweeter.

I have a pair of JBL 4430s in my theater .. it uses a 15" and a horn. The mids are very nice .. but I know the horn is reaching pretty low.

[ligs]

Re: Can modern large woofers produce midrange ?

I made a guess of the crossover point of 3.5 k Hz of JBL -L100 based on the graph in

http://www.troelsgravesen.dk/JBL_L100.htm

With a shallow slope XO in the original L-100, the midrange probably overlaps with the woofer a lot thus helping with the directivity issue.

Still, it is amazing the XO is just a cap for the mid and a cap for the high, L-100 is one of the best rock and roll speakers. Pioneer HPM 100 has one additional choke for the woofer, but otherwise is almost as simple as L100.

[carlspeak]

Re: Can modern large woofers produce midrange ?

2-way designs with large woofer/mid & tweeter just aren't 'in' these days. If you go back and study some audio history a little you'll find some classic designs like you describe. Advent, EPI and KLH are examples where the designers put a lot of time into developing those large woofers that could go out to 1 Khz or so with little edge resonance effects that would require at minimum, 2nd or 3rd order LP sections. Instead they used 1st order or no coil at all (EPI 100 for example).
Those kinds of woofers just aren't being mass marketed today. EnABLE technology (painting dots or woofer periphery's) has been around awhile that was developed to mitigate those peaky 1-4 kHz resonance peaks. You could look into that. The experts on that reside over at DIYaudio, multi-way speaker forum.

[bwaslo]

Re: Can modern large woofers produce midrange ?

Not sold by PE, but AE speakers make some that have more than decent midrange. Their venerable 15 inch TD15M is usable to over 2kHz. The limited off-axis response (a.k.a "directivity") can be a good thing in a controlled directivity design when using a waveguide. Not cheap, though.

The PE PA380 isn't bad up for up to about 1kHz, though it has some funniness around 500Hz to be worked around.

[jcpahman77]

Re: Can modern large woofers produce midrange ?

I know you're talking about home speakers but as you did reference JBL, my church uses these:


VRX932LA-1

And while I have no idea what the crossover frequency is to the triplet of horns is, I know they produce some of the cleanest mids I've ever heard without sacrificing other frequencies. They don't play terribly low, but they do feature a 12" woofer.

[ligs]

Re: Can modern large woofers produce midrange ?

I am quite surprised by the decent midrange performance of the Pioneer HPM100. But then this 12 inch woofer has a cast frame, copper shortening rings, treated accordion surround and weighs almost 13 lbs. It obviously is not just a typical woofer.

http://www.ebay.com/itm/Pioneer-12-Woofer-HPM-100-Pioneer-Speaker-NEW-/260846603477?pt=Vintage_Electronics_R2&hash=item3cbbab4cd5

[johnnyrichards]

Re: Can modern large woofers produce midrange ?

Dont laugh, but the GRS 12" is smooth to 2k with virtually no break up. It could be used in a 2-way if one wanted to deal with the inherent physical drawbacks of such a design.

[jcpahman77]

Re: Can modern large woofers produce midrange ?

Forgive me, but:

It could be used in a 2-way if one wanted to deal with the inherent physical drawbacks of such a design.

Could you elaborate as to the drawbacks?

[donprice]

Re: Can modern large woofers produce midrange ?

Forgive me, but:

Could you elaborate as to the drawbacks?

Big woofers mean big boxes and that often results in low WAF. That is an obvious drawback for some.

Beaming of the woofer (related to diameter, basically) means you generally want to cross as low as possible...often below the limits of the more common and inexpensive dome tweeters. The econowave designs use a crossover around 1600 Hz, Wayne Parham's 4Pi (1300 Hz?) and the JBL 4430 referenced above crosses at 1000 Hz (or is it 1200?). All of these use relatively expensive compression drivers and horns/waveguides used in pro audio applications. Tons of discussion regarding directivity, beaming, and other design issues can be found by searching for "econowave" or 4pi.

I'm sure there are other drawbacks related to size but these seem the most obvious to me.

[johnnyrichards]

Re: Can modern large woofers produce midrange ?

Forgive me, but:



Could you elaborate as to the drawbacks?

12" drivers start becoming directional at a very low frequency, which leads to erratic off-axis performance when crossed to a regular tweeter (say 1800hz and up).

Of course, it is endlessly debatable how important that is but IMHO the most pleasant sounding speakers are those that exhibit a smooth off-axis as well as on-axis response.

Then again, sitting a little off-axis of a 12" 2-way with a dome tweeter will probably emphasize the bass and treble and might make for a really fun rock and roll party speaker