Why horn-loaded loudspeakers are subject to design tradeoffs

[Deang]

"I did not take the move by Chris to be an effort build a soap box for himself at all..."

I did, and I thought it was inappropriate to be asked to leave the thread. You are always so gracious...

"Rather, in another thread there was a request for discussion of why horns subjectively sound good. But then there was an additional comment generally requesting that the discussion not be technical."

Yet the thread is filled with technical data and discussion.

It seems silly to have two threads with topics that are more so than not -- connected. For example, Terry's last comment in the other thread probably belonged here, and I see several posts here that probably should have been placed in the other thread.

Engineering involves trade offs, and I don't see much point in having a thread devoted to the positives (only), and another for the negatives (only). They are already beginning to overlap ...

... and I certainly don't appreciate being directed where and how to post - it's both rude and ridiculous. Sorry Chris.

Edited July 13, 2014 by DeanG

[Max2]

After running stacked La Scalas, I can attest to the fact there are other speakers in the world that give and take, everyone is fully aware La Scalas are of the Folded design, however going the route iv gone in the last month, there is something to be said about Direct Raidiators.

Currently im running a "Push/Pull" design and just about have the crossovers dialed in.

The one thing this experiment has taught me is keep an open mind as to sound reproduction.

Good point MM. I have never heard anyone really bad mouth a Cornwall or say all its glorious vented cab bass is just too distorted when compared to a horn cab. Yeah, lets make that mid horn bigger, but lets leave the bass alone

[Max2]

I think its time all the quasi-techno engineers build something better. Time alignment, peaky cycle ranges, yeah i guess my K-horns have them. No low end with my LaScalas's, got that issue too. Just build a horn cab close to same size, same good looks and better performance for the K and L and then we will have something. Until then....

Want something better than a La Scala? Take a Danley SH46 and park it on top of a Bill Fitzmaurice DR280. Drive the pair of them with a DEQX.

Want something better than a K-Horn? Try a Danley J1.

Either way, looks and size are completely out the window. Always has been where horns are concerned. The Klipsch home product struck that fine line between performance and cohabit-ability.

Maybe Im reading the chart wrong, but the 280 looks like its -15db at 60 hz?

[Marvel]

Good point MM. I have never heard anyone really bad mouth a Cornwall or say all its glorious vented cab bass is just too distorted when compared to a horn cab. Yeah, lets make that mid horn bigger, but lets leave the bass alone

I don't like the Cornwall bass at all, really. Bloated and boomy, at least the ones I heard at Klipsch HQ during one of the pilgrimages. I really don't think I'm the only one who feels this way.

Bruce

[Deang]

I would have just called the thread: "Horn loaded loudspeakers are subject to design trade offs (just like every other loudspeaker design)."

I've attached the data sheet for the BMS 4591, which is the ceramic version of the 4592-MID that everyone is so fond of. I'm sure BMS used a horn that would show this driver in its best light. Please note the distortion plot. I see 2nd harmonic distortion only 8dB down at 3kHz. This is with 1 watt applied. Am I reading this wrong? If I'm reading it right, how does it play into this idea that horns generate less distortion than dynamic radiators?

Dynamic radiators have come a very long way in 40 years. Some have sensitivity ratings approaching that of compression drivers.

The Palladium doesn't use a compression driver -- it uses a 4" inverted dynamic radiator. Why?

Below is from: http://sound.westhost.com/articles/pa.htm#s511

5.1.1 - Throat Power Vs. Size Vs. Frequency

For what it's worth (and because you'll find very little on the Net), the maximum acoustic power into the throat depends on several factors. First is the relationship of actual frequency to the horn's cutoff frequency. As the ratio of f/fc (frequency divided by cutoff frequency) increases, so does distortion for a given acoustic power per unit of throat area. A sensible upper limit for throat acoustic power is around 6-10mW/mm², meaning that a 25mm (1") throat should not be subjected to more than 3-5W. A 50mm throat can take 4 times that power, or 12-20W acoustic (see graph [1]). The amount of acoustic power that can be accommodated decreases as frequency increases. For horns intended for operation from (say) 800Hz and above, the normal rolloff of amplitude with frequency (as found in most music) means that the acoustic power also falls with increasing frequency.

If the conversion efficiency of a compression driver is (say) 25%, this means there is absolutely no point supplying more than 20W (electrical) to a compression driver on a 25mm throat, or 80W for a 50mm throat, allowing for a sensible distortion of 2%. Past a certain limit (which varies with frequency vs. horn cutoff), supplying more power creates no increase in SPL, but simply creates more and more distortion. The maximum power must be reduced as frequency increases. CD horns require HF boost, so can easily be pushed much too hard at high frequencies, resulting in greatly increased distortion.

Quite obviously, any horn that has a small throat must have limited power capability, and providing amplifiers that are (much) larger than needed for "headroom" is a completely pointless exercise. It is both convenient and accurate to consider the effect as "air overload".

According to a technical note from JBL [2], the situation is actually worse than the above graph shows. A 200Hz horn at 10kHz can readily generate 48% second harmonic distortion, with as little as 2.5W (electrical) input - a mere 0.75 acoustical Watts. As noted in references 1 and 2, this information was first determined in 1954, but over time seems to have been lost. As you can see, I'm determined that this will not happen.

________________________________________________________________________________________________________________________________________________________

I have NEVER claimed to be an "expert". What I would like is a real "expert" to come in here and explain why this particular issue is not an issue.

Now, I love the sound of horn systems, and went from RB-5s to Jubilees in a decade. I now have LaScalas, and they're quite impressive. Upstairs I'm running some coaxials, which are horn loaded from about 1800Hz on up -- the top octaves are handled by a modest compression driver and the midrange is handled by a very stiff paper cone. Like most, I cut at 80Hz, and dump everything below that to subs. Now, at very high sound pressure levels, the upstairs system sounds subjectively every bit as good as the LaScalas. I would say the LaScalas are marginally more dynamic -- the upstairs system is pretty impressive -- but how can that be with all of those cones pumping out gobs of distortion?

Horns just sound different, and they sound different in a very good kind of way, but if I had a question to add to a FAQ, it would be this: Do horns really produce less distortion just because they're horns?

bms-4591.pdf

[Max2]

Good point MM. I have never heard anyone really bad mouth a Cornwall or say all its glorious vented cab bass is just too distorted when compared to a horn cab. Yeah, lets make that mid horn bigger, but lets leave the bass alone

I don't like the Cornwall bass at all, really. Bloated and boomy, at least the ones I heard at Klipsch HQ during one of the pilgrimages. I really don't think I'm the only one who feels this way.

Bruce

Its obviously not as refined as a horn cab, but it definitely has its place among many two channel listeners. Heck, the Cornwall may be the most well known Klipsch speaker of all time short of the Heresy. I owned a pair of Cornwall II's before LaScalas and K's and really enjoyed them. It was only a short stint of owning a set of Belles that lured me away to the bigger midrange output. My friend still owns the Cornwalls I used to own and I still get to hear them by his pool from time to time. He has friendly neighbors on each side of him that tolerate all that bloated boomy, but some where about the sixth or seventh house down doesn't

[garyrc]

Horns just sound different, and they sound different in a very good kind of way, but if I had a question to add to a FAQ, it would be this: Do horns really produce less distortion just because they're horns?

Is it possible that, in general, horns produce less FM distortion, but equal Harmonic distortion?

I think my old THX packet (from before THX was used in homes) said that T. Holman failed to find that bass horns produced lower harmonic distortion than DRs, but I don't think they described his method, and there was no mention of FM distortion.

Some modern theater systems use DRs in the bass, but horns for the mids/highs. I think the old (horn, sometimes with ports as well) theater speakers sounded like they had better, cleaner, more dynamic bass ... even though they didn't go as low as modern theater subs (rolling off below 40 Hz, or so). The old bass horns I'm thinking of would be the Ampex/JBL horns made for Todd-AO, and the big Altecs used in Cinerama).

[Deang]

Think about it like this: you need to fill a large area with sound. What is the best way to do it? Horns, obviously. High output with a moderate amount of power. But when you get into smaller rooms, there are other options which sound every bit as good. Now, you're probably going to need 200 wpc, but that kind of power is relatively inexpensive these days -- the likes of QSC and Hypex deliver amazing sound for the money.

[kg4guy]

Well I have a pair of Danley SH95's and they are for there size a pretty amazing speaker not much below 50Hz-60Hz but with a few Th118's crossed at 100Hz it doesn't get much better.

[ClaudeJ1]

I would love to hear some Jubs, but they have had their share of pokes on here as well.

I heard Jubes in 4 different places Measured them indoors and out, and helped design a pair of passive versions of a clone with different drivers. I have decades of experience, commercially, and in the home, with ALL of the Klipsch bass bins. The top two are the MWM and the Jubilee, which PWK himself claimed it took 50 years to improve his original Khorn bass bin

Unfortunately, the after he sold the company, the new owners thought it was better, for marketing purposes, not to mess the the legendary longevity of the Khorn, since it's only speaker in the WORLD still being produced since the late 40's. No one has ever been able to top that achievement and they certainly wanted to keep racking up the decades for that physics and construction marvel. I designed a smaller version of an MWMs, with only one 90 degree turn instead of two, that fits in a corner. A few people that have built them think they are better than LaScalas, and one thinks they sound better than Khorn bass. I would say "different" but better is in the ears and room of the beholder. None of this is absolute, but horn bass is the most realistic sounding because of low distortion and superior transient response.

I believe those who have "poked" at the Jubilee have never experienced them, but hey, we all need something to complain about, right? The Jubilee is an amazing "little" horn by any standard and to prefer something else is mostly a matter of taste and not objective measurements. If anyone prefers something else, it's usually another bass horn and NOT a direct radiator bass with 10-40 times the modulation distortion.

[ClaudeJ1]

After running stacked La Scalas, I can attest to the fact there are other speakers in the world that give and take, everyone is fully aware La Scalas are of the Folded design, however going the route iv gone in the last month, there is something to be said about Direct Raidiators.

Currently im running a "Push/Pull" design and just about have the crossovers dialed in.

The one thing this experiment has taught me is keep an open mind as to sound reproduction.

Good point MM. I have never heard anyone really bad mouth a Cornwall or say all its glorious vented cab bass is just too distorted when compared to a horn cab. Yeah, lets make that mid horn bigger, but lets leave the bass alone

Hmmm. Well, making the mid horn bigger allows for a lower crossover point so the high distortion direct radiator can be rolled off sooner, thus reducing the overall distortion where our hearing is most sensitive. IOW, in the band where most of the music resides.

[ClaudeJ1]

Good point MM. I have never heard anyone really bad mouth a Cornwall or say all its glorious vented cab bass is just too distorted when compared to a horn cab. Yeah, lets make that mid horn bigger, but lets leave the bass alone

I don't like the Cornwall bass at all, really. Bloated and boomy, at least the ones I heard at Klipsch HQ during one of the pilgrimages. I really don't think I'm the only one who feels this way.

Bruce

It's peaky at 90 Hz. Some people call it slam. The CW published curves reflect this, even though they have been put through the "marketing smoothing filter" before publications. Besides, the typical room dimensions tend to amplify this further, which makes for yours and others' conclusion.

[ClaudeJ1]

Think about it like this: you need to fill a large area with sound. What is the best way to do it? Horns, obviously. High output with a moderate amount of power. But when you get into smaller rooms, there are other options which sound every bit as good. Now, you're probably going to need 200 wpc, but that kind of power is relatively inexpensive these days -- the likes of QSC and Hypex deliver amazing sound for the money.

I agree with this notion, Dean.

I have a friend who designs DR and OB systems for 2 ch. and 7.1 separately in a beautiful HT room with all the treatments. It is the best room I've ever experienced for listening. He just spent $6k on a Pass pre amp and $13K on a turntable with no cartridge. He is a highly skilled builder or custom homes and cabinetry. His home is magazine cover worthy inside and out. I helped him design a bass horn recently, but he won't build it for a while yet.

He has a huge inventory of passive components and owns professional software for room measurements, box, and Xover design. He has discerning ears and an opinion that I trust. He also owns an amazing range of great music, being a former guitarist. He also built Danley SPUDS for subs.

He used to own LaScalas and built a huge sub for them almost 40 years ago. He upgraded to the big Magneplanars, then went on to strictly building his own Direct Radiator speakers, big and small, for the last 30 years.

He recently heard my system and declared the best balanced all-horn system The only thing lacking in his last setup were the DYNAMICS because of smaller drivers. This inspired him to try and match my horn dynamics with very expensive, exotic drivers made in Europe. I helped him with the measurements outdoors a few weeks back and I have never seen a flatter curve on a speaker than this one. He frets about 0.1 db and adjusts the network accordingly. I only heard a few tunes on a single speaker before I left and it was impressive. Sometives it's good to get away from Klipshitis and listen to other excellent stuff.

So Dean, I agree with your notion that direct radiators can sound very good when done well. Most the speakers being built today are direct radiators for those who think the only good horns are too big for the house. The majority rules because they have wives.

Edited July 13, 2014 by ClaudeJ1

[Don Richard]

I've attached the data sheet for the BMS 4591, which is the ceramic version of the 4592-MID that everyone is so fond of. I'm sure BMS used a horn that would show this driver in its best light. Please note the distortion plot. I see 2nd harmonic distortion only 8dB down at 3kHz. This is with 1 watt applied. Am I reading this wrong? If I'm reading it right, how does it play into this idea that horns generate less distortion than dynamic radiators?

If I'm reading the chart right the distortion curves are shifted up by +10dB. This would make the 2nd harmonic -18 dB referenced to the fundamental, at 3 kHz.

Edited July 13, 2014 by Don Richard

[bobdog]

I've attached the data sheet for the BMS 4591, which is the ceramic version of the 4592-MID that everyone is so fond of. I'm sure BMS used a horn that would show this driver in its best light. Please note the distortion plot. I see 2nd harmonic distortion only 8dB down at 3kHz. This is with 1 watt applied. Am I reading this wrong? If I'm reading it right, how does it play into this idea that horns generate less distortion than dynamic radiators?

If I'm reading the chart right the distortion curves are shifted up by +10dB. This would make the 2nd harmonic -18 dB referenced to the fundamental.

I am very interested in this as I am about to purchase a pair of Eliptracs and 4592-mids. I thought they were well regarded but Deans comments have me worried as the cost is more than I want to spend if they are going to be a try and throw away thing. How do they compare measurement wise to K55s?

[Don Richard]

I am very interested in this as I am about to purchase a pair of Eliptracs and 4592-mids. I thought they were well regarded but Deans comments have me worried as the cost is more than I want to spend if they are going to be a try and throw away thing. How do they compare measurement wise to K55s?

The BMS measurements are at I watt input power and the acoustic output of the driver at that power is 118 dB. If the data on the K55 is also run at 1 watt the acoustic output is going to be about 107 dB, 10 dB less than the BMS. To make a valid comparison it will be necessary to run the K55 such that it also outputs 118 dB @ 3kHz when distortion measurements are taken.

If Dave at Fastlane says the BMS works well on his Eliptrac horns, I wouldn't worry too much.

[Don Richard]

According to a technical note from JBL [2], the situation is actually worse than the above graph shows. A 200Hz horn at 10kHz can readily generate 48% second harmonic distortion, with as little as 2.5W (electrical) input - a mere 0.75 acoustical Watts. As noted in references 1 and 2, this information was first determined in 1954, but over time seems to have been lost. As you can see, I'm determined that this will not happen.

I doubt there is any conventional horn that will go from 200-10,000 Hz. Midbass horns are generally designed to reproduce 3 octaves bandwidth, with a few 200 Hz designs capable of response to 1600 Hz or beyond.

Edited July 13, 2014 by Don Richard

[ClaudeJ1]

I doubt there is any conventional horn that will go from 200-10,000 Hz. Midbass horns are generally designed to reproduce 3 octaves bandwidth, with a few 200 Hz designs capable of response to 1600 Hz or beyond.

100-1Khz is ideal. That way you add a sub and a 1" driver and you have a great system, provided you add time delays for the top end and some inevitable PEQ with 4th order L-R filters. the hard part is a good 100-1Khz. horn.

The best one I've heard is from Sadurni Acoustics and it only makes it to 800. Close enough.

[Chris A]

Horns just sound different, and they sound different in a very good kind of way, but if I had a question to add to a FAQ, it would be this: Do horns really produce less distortion just because they're horns?

Is it possible that, in general, horns produce less FM distortion, but equal Harmonic distortion?

See http://www.hps4000.com/pages/special/woofer_distortion.pdf for an answer to that question. This is a very good article on bass bin modulation distortion with Klipsch professional MWM and bass reflex (vented) bins under test.

Edited July 13, 2014 by Chris A

[garyrc]

Horns just sound different, and they sound different in a very good kind of way, but if I had a question to add to a FAQ, it would be this: Do horns really produce less distortion just because they're horns?

Is it possible that, in general, horns produce less FM distortion, but equal Harmonic distortion?

See http://www.hps4000.com/pages/special/woofer_distortion.pdf for an answer to that question. This is a very good article on bass bin modulation distortion with Klipsch professional MWM and bass reflex (vented) bins under test.

Thanks, Chris! Very interesting.