Lowther Array Open Baffle?

Browntrout · « **on:** 11 Aug 2009, 05:30 pm »

Has anyone implimented multiple Lowther full range drivers in an open baffle array? Say four or five drivers per side. With the idea being to generate good bass without losing speed and a boomy cabinet. Very interested to hear the results if someone has been brave enough.

FullRangeMan · « **Reply #1 on:** 11 Aug 2009, 05:55 pm »

I like fullranges and linearrays, and with OB capacity this speakers is perfect to me.
A problem: Lowthers are expensive drivers.
I think the definitive speaker is fullrange driver + linearray + OB + 16 ohms to be driven by a tube amp.
Regards.

Mariusz · « **Reply #2 on:** 11 Aug 2009, 06:15 pm »

Super 8 Alnico - Audio Nirvana drivers would be cheaper and might be a better choice for DIY.
(2 super 12s AN per side might be even better)

My 2 cents

Mariusz

Angaria · « **Reply #3 on:** 11 Aug 2009, 06:27 pm »

While the beaming of larger drivers should help avoid comb filtering, you're still going to have a large c2c distance if you do this....

Scott F. · « **Reply #4 on:** 11 Aug 2009, 06:30 pm »

I've got a fair grip on the pulse of the Lowther guys out there and nobody that I'm aware of has tried that. I do know several people that are doing Lowthers on top and 15"s on an OB bottom. In fact, I've got in house a prototype active crossover (from a well know mfgr) who within the XO has switches to provide not only notch filtering for the (mostly) FR driver but also a bit of EQing and boost for the OB woofer. Its a very cool concept that works quite well. All of this is done with JFets rather than opamps and digital conversion.

As FRM mentioned, a line array of Lowthers, even the cheap ones, would be really freakin' expensive. I would seriously suggest if you are thinking of going that route, do like me and a few of the other local GAS guys are doing an invest in a PM6A, or better yet the PM2A (what I personally use) then do a vintage 15" (Altec 416 please) in a vented enclosure. Cross it at 150Hz (actively), SET on top, SS on the woofer. The sound quality is phenomenal and integration between the two drivers is seamless. Oh, and no notch, shelving or baffle step compensation is needed...at all.

Here are a few pics of my Lowther OB setup

BPT · « **Reply #5 on:** 11 Aug 2009, 06:43 pm »

If you are going to try a relatively full range line, a 4" is probably as big as you want to go. 3-5 drivers should get you down to 150-200 Hz. or so. Right now I am using 7 drivers and getting down to 100Hz. (4th order crossover) with no problems. My line using 40 drivers is in construction. aa
Chris H.

smbrown · « **Reply #6 on:** 13 Aug 2009, 02:49 pm »

Scott, beautiful set up! Do you have problems with phase? If I'm seeing this correctly the woofers are a fair distance back from the OBs. Can you share any more info on the electronic cross over manufactur / model? Thanks!

Scott F. · « **Reply #7 on:** 13 Aug 2009, 06:23 pm »

Hiya,

Thanks for the compliment

When it comes to phase I had a couple of minor issues that were easily solved by placement of the open baffles. Basically I moved the speakers further out away from the walls until everything snapped into place and the crossover point hole (cancellation due to phase) was gone. Right now they are about 6' out from the wall. One thing that is so impressive about the sound is when you listen to full orchestral pieces that have been recorded with a simple pair of stereo mics, placement of the different sections of the orchestra is like no other speakers I've heard. They have tremendous depth, placement and a monstrous soundstage. Regarding the XO, I probably shouldn't talk too much about it since it isn't in production yet and may not be for a little while, sorry. When the design does become finalized, I'll be happy to get into all of the gory details

Quote from: smbrown on 13 Aug 2009, 02:49 pm

Scott, beautiful set up! Do you have problems with phase? If I'm seeing this correctly the woofers are a fair distance back from the OBs. Can you share any more info on the electronic cross over manufactur / model? Thanks!

Browntrout · « **Reply #8 on:** 13 Aug 2009, 06:33 pm »

Thanks for all the replies, Scott your setup is beautifull I especially like the see through baffles very in keeping with the sound I imagine.

FredT300B · « **Reply #9 on:** 13 Aug 2009, 08:58 pm »

There's a technical problem with an array of full range drivers. The CTC spacing would result in a very audible comb filter effect starting at a relatively low frequency. See Jim Griffin's line array white paper for an explanation of the effects of CTC driver separation. It' on page 11:
http://www.audioroundtable.com/misc/nflawp.pdf

For a graphical example of comb filtering see the unsmoothed graph of the Kuze 3201 full range driver line array. Even with 2" drivers having relatively close CTC spacing, the comb filter effect is clearly visible:
http://www.parts-express.com/projectshowcase/kuze3201/kuze3201weqnosmooth.jpg

Browntrout · « **Reply #10 on:** 13 Aug 2009, 09:44 pm »

Very usefull indeed Fred, thanks. It would seem that the effect of having centre to centre distances that are greater than 2 Lambda coould be countered by focusing each driver at the point of listening.
Would this create sweet spot (altering the sound of a line array from wide spacious to concentrated and focused like a single driver) whilst retainind the increase in dynamics and lower end frequency capability? I could handle that.

JoshK · « **Reply #11 on:** 14 Aug 2009, 02:40 am »

Quote from: Angaria on 11 Aug 2009, 06:27 pm

While the beaming of larger drivers should help avoid comb filtering, you're still going to have a large c2c distance if you do this....

I wouldn't think it would actually help much against comb filtering. The c-t-c is just too far away. I don't know the wavelengths off the top of my head but I don't think you can get away with much larger than 2" drivers without using a tweeter unless you want a roller coaster for the FR of top octave.

That is a lot of money in drivers to be dissapointed in the results. If you are sure you want to do it, try cheaper drivers first as proof of concept and save yourself a lot of money if it doesn't work out.

Danny Richie · « **Reply #12 on:** 14 Aug 2009, 03:22 am »

Fred is right. The response would be a real mess.

The guys over on the AV123 forum were discussing stacking speakers on top of each other.

So I did that and showed the measured results so they would understand how sever the cancellation would be. The same thing applies to stacking multiple full range drivers.

See link: http://forums.av123.com/showthread.php?t=15154&highlight=cancellation&page=2

Paul Hynes · « **Reply #13 on:** 14 Aug 2009, 11:13 am »

Hello Browntrout,

I have built open baffle line arrays using eight Visaton B200 full range drive units per line. These are nominally eight inch drive units and so this would be a theoretical no-no regarding comb effects. However, in practice they sound great and I am not finding any audible problems with combing effects at a listening distance of around twelve feet although you may find problems if your listening position is very close to the speakers.

I decided to go for it with the B200 because I recalled using 10? and 12? drive units, in line arrays, as vocal PA speakers, when playing in a band as a youngster in the 60?s and 70?s. I cannot remember suffering any audible combing effects from these line arrays. I do remember they were excellent as PA speakers and that they were very articulate and coherent with voice.

Out of interest, I wired my drive units in such a way that I could program series parallel/wiring or parallel wiring of the drive units, using 4mm plugs and sockets. It is very audibly obvious that wiring any drive units in series/parallel causes drive unit interaction that diffuses the image and makes it dynamically unstable. This problem does not occur if you wire the drive units in parallel as each drive unit sees the same drive signal from the amplifier. The whole line then behaves as one drive unit electrically. The image is very stable under all dynamic conditions. It does, however, present an awkward load to the amplifier, so I designed a power amplifier specifically to work into these low impedances. It may be that some of the audible problems attributed to combing effects are caused by series/parallel wiring of the drive units as line arrays tend to be wired in series/parallel to give an impedance that standard amplifiers can drive.

Regards
Paul

BPT · « **Reply #14 on:** 14 Aug 2009, 01:54 pm »

One solution that will get you a single driver continuous 6' line down to 300hz (150Hz. if you don't listen at high volume) is the BG planar. http://www.parts-express.com/pe/showdetl.cfm?Partnumber=264-700
Chris H.

FullRangeMan · « **Reply #15 on:** 14 Aug 2009, 05:33 pm »

Quote from: Paul Hynes on 14 Aug 2009, 11:13 am

Hello Browntrout,
I have built open baffle line arrays using eight Visaton B200 full range drive units per line. These are nominally eight inch drive units and so this would be a theoretical no-no regarding comb effects. However, in practice they sound great and I am not finding any audible problems with combing effects at a listening distance of around twelve feet although you may find problems if your listening position is very close to the speakers.
I decided to go for it with the B200 because I recalled using 10? and 12? drive units, in line arrays, as vocal PA speakers, when playing in a band as a youngster in the 60?s and 70?s. I cannot remember suffering any audible combing effects from these line arrays. I do remember they were excellent as PA speakers and that they were very articulate and coherent with voice.

Out of interest, I wired my drive units in such a way that I could program series parallel/wiring or parallel wiring of the drive units, using 4mm plugs and sockets. It is very audibly obvious that wiring any drive units in series/parallel causes drive unit interaction that diffuses the image and makes it dynamically unstable. This problem does not occur if you wire the drive units in parallel as each drive unit sees the same drive signal from the amplifier. The whole line then behaves as one drive unit electrically. The image is very stable under all dynamic conditions. It does, however, present an awkward load to the amplifier, so I designed a power amplifier specifically to work into these low impedances. It may be that some of the audible problems attributed to combing effects are caused by series/parallel wiring of the drive units as line arrays tend to be wired in series/parallel to give an impedance that standard amplifiers can drive.
Regards
Paul

I agree with Paul Hynes above. This comb filter effect seems exist only very close to the speakers,
I built a LA of four 10 inches fullranges, sealed box and there was no problem, even close the speaker, the space between the Aluminium round frames is 45mm.
This IDS25 picture of Engineer Roger Russel use 25 cheap 4inches fullranges per sealed box and the sound is very beautiful according the reviews.
www.ids25.com
Regards.

Danny Richie · « **Reply #16 on:** 14 Aug 2009, 05:48 pm »

I am afraid that you (fullrangeman) and Paul are getting cancellation effects that will result in +/-15db swings (or more) from any measuring (or listening point). Keep in mind that the wave lengths in the top octave are only 1 to 2 inches long so a time delay of only 1 or 2 inches is all that it will take to create a good 15db hole in the response.

Also due to the length of those lines you guys will get comb filtering effects well down into the ranges of 2 and 3kHz.

And BTW, I heard a speaker like the one pictured below a few years ago at RMAF.

FullRangeMan · « **Reply #17 on:** 14 Aug 2009, 07:31 pm »

Quote from: Danny on 14 Aug 2009, 05:48 pm

And BTW, I heard a speaker like the one pictured below a few years ago at RMAF.

Do you listen this same IDS25 at RMAF?
What are your opinion about this LineArray do you listen?

Regards.

JohnR · « **Reply #18 on:** 14 Aug 2009, 07:52 pm »

Quote from: Danny on 14 Aug 2009, 05:48 pm

I am afraid that you (fullrangeman) and Paul are getting cancellation effects that will result in +/-15db swings (or more) from any measuring (or listening point). Keep in mind that the wave lengths in the top octave are only 1 to 2 inches long so a time delay of only 1 or 2 inches is all that it will take to create a good 15db hole in the response.

I think it's worth clarifying, though, that the measurements you linked were for two drivers (in the same freq range), not an array of them.

Danny Richie · « **Reply #19 on:** 14 Aug 2009, 08:07 pm »

You are correct John.

The two speakers I measured were stacked tweeter to tweeter and the center to center distance of the tweeters was about 7".

For an array of drivers, like the one pictured, the center to center spacing is much greater and the cancellation is much worse, and much lower in the range that it cancels.

Quote

What are your opinion about this LineArray do you listen?

Do you really want to know?