Using PA Cab As A Bass Cab?

[agedhorse]

My comments about basses being flat is, I think, being misunderstood. If a bass as an instrument was "flat" all notes would consist of just the fundamental and all notes at the same level, essentially a chomatic sine wave generator. The fact that every bass sounds different, and that each player has distinctly different tastes in basses and playing styles has led to the evolution of the instrument. The evolution resulted in an instrument that produces a series of harmonically rich sine waves that in many cases exceed the level and energy of the fundamental. A simple sine wave at the fundamental would sound dreadful, really awful.

With regards to designing cabinets, I am primarily a pro audio guy and have designed my fair share of successful commercial high dollar speaker products. They are plenty flat and low distortion. For most players (not all) they are not as desireable as the cabinets that I have designed specifically for the bass industry. In play test after play test with top national players, those designed with the characteristics of bass guitar are more preferred. It doesn't matter if the pa version is flatter or whatever, I must design for the customer's preference and who am I to say these top players are wrong? Not every speaker philosophy is right for every player, not every bass is right for every player and to think so is ignoring personal preference, tastes and choice.

Yes, there really is (or should be) a lot of engineering involved in the design of a quality bass speaker product. There is also a lot of testing, failure analysis, statistical analysis involved.

Originally Posted by Arjank

I do not share your thoughts on this matter.
My cab measures extremely flat and now I can hear how a bass CAN sound and that is far, far from sterile and lifeless. On the contrary, every guy who played his bass through it found that they never heard their bass like it before, their sound came more to life then ever. Btw it's not only linearity that's important, there are several other factors involved.

That basscabs aren't linear and color a lot is because their production has to be cheap and easy. There ain't much engineering and thought in 95% of the basscabs.

[DrumsAndBass]

Mr. agedhorse, I thank you for all that you do here on TB.

Originally Posted by john nam

Has anyone used a "really decent" PA cab, like a JBL, as a bass cab? Volume-wise, did you find that the PA cab farted out sooner than a "really decent" bass cab (Ampeg, GK?) would have, assuming all else is very similar (ex: same speaker size, wattage handling, sensitivity, freq response, etc)?

I know a lot of people are going to ask why I'm asking this, but it's a long story that I wouldn't want to bore you guys with

Yes, I spent about $1200.00 on a JBL PRX 618s XLF.
Check it out: http://www.jblpro.com/catalog/genera...?PId=365&MId=3

It's not heavy although it's got some bulk. I have to smile as I consider the part of your inquiry "... did you find that that the PA cab farted out ..." Man, I assure you that I have never heard a more glorious sounding low response out of my rig. I am not a pro. I did my musical homework (and saving) on this cab and I tell you it gave my stage rig an astounding amount of volume and clean low frequencies. I stacked my regular rig on top of it - an Aguilar 4x10 powered by an AG 500sc. The sub would overpower the mighty Aguilar rig by a long long shot so I had to really twist knobs. But after I balanced out the eq levels and gains it was a very very very nice blend of sounds. Near as I can tell, I heard the fundamentals. But you know what? It was fatiguing to play through it for a few hours on a gig. It was a hard sonic massage for me about 5' in front of the stack. And in reality, I don't play particularly loud. But I'm still learning about tone and the bass. This stack was short lived for me.

I gigged with it 3 times a month for a year and believe it or not I sold off that entire rig. Thing is, I play 99% Reggae from the 60's - 90's. It might be generalized that I like a lot of low bass in my tone - well, yes I do. I've got no use for horns and tweeters at all. But I learned that my stage rig need not produce so very very very much low end. And there's lot's of reasons why I applied that learning - actually I have several people on TB to thank for posting their research and practice based tips here on TB. They'll remain nameless in my post. I wanted a better bass sound from an all - in - one cabinet. So, I payed JHawk to build me the cab in this link - the one for "dubbass." It's the absolute best cab that for me. Here it is:
http://www.jhawkcustoms.com/finished.htm

[DrumsAndBass]

Mr. agedhorse I want to thank you for all the great things you do here on TB.

[agedhorse]

I am very familiar with the 618-XLF, one of the challenges is going to be the alignment between the sub and your 410 because these particular cabinets are tuned very differently and the phase response between 50Hz and 120Hz is (probably not) not going to be very complimentary. Doesn't mean that it won't sound impressive, but there may be artifacts that you also find unattractive. This particular combination might sound better with the JBL on board low pass feeding the sub and the high pass out feeding a power amp to power the 410. You would use your existing amp as a preamp (unless you can interrupt and insert the high pass signal from the x-over out on the sub into the power amp in on your amp. You can not do this on a parallel effects loop generally.

The crossover on the sub is an 8th order LR alignment so at the crossover point there is some serious phase shift happening. Not so much a problem where accompanied by the complimentary phase shift and level rolloff on the high passed top. Without it, the artifacts may become noticeable.

This is just an engineering hunch based on y familiarity with the sub, which is a very well executed pro audio design BTW, IMO.

[DrumsAndBass]

I spent considerable time trying to balance the sound of that stack - 410 on top of the JBL and it was tough to get it right. Some notes just jumped out and were quite a bit more pronounced. Was that a phasing deal ?

[agedhorse]

Originally Posted by DrumsAndBass

I spent considerable time trying to balance the sound of that stack - 410 on top of the JBL and it was tough to get it right. Some notes just jumped out and were quite a bit more pronounced. Was that a phasing deal ?

Yes, more than likely you were getting "sum and difference" issues as a result of conflicting phase response.

I have taken a bit of heat here for suggesting that mixing driver sizes is ALWAYS bad. In fact, when phase response is considered as part of the design equation, there is absolutely nothing wrong with this... BUT where there are phase response conflicts this is one of the results that can occur.

The problem with absolute statements is that that they are almost always inaccurate for a significant number of applications. There are few absolutes in engineering, as a large part of what an engineer does is manage the art of compromise. To do so requires a real and thorough understanding of all parts of the problem and the various solutions, otherwise it's just an uninformed, inaccurate statement.

When developing speaker designs, I look at the phase response on and off axis to look for potential issues that may make the design or tuning unsuitable in combination with other speaker products of the family. Not doing so is really throwing speakers in a box and calling it done IMO. I don't know how many bass cabinet manufacturers analyse phase response but it's pretty darn standard in pro audio.

[will33]

So, last weekend we were playing at this bar in Brenham called Lil Mikes. There was this one chick who'd been partying all day who was getting way too close for comfort, dancing on cables (suggestively dancing), reaching past my mic stand touching my bass, making weird eyes, etc. She had these small, but really pointy, breasts that were causing a diffraction problem from the main that was right there to my left and taking the sparkle out of our acoustic guitar for the rest of the crowd. At first, I pulled my neck back and gave her a face like "you're too close" but that didn't seem to do much good. She invaded my space even further next tune and I even made a comment to my bandmates between songs that if she did that again, I was going to kick her.

Then my cooler head prevailed. I talked to her on a setbreak and explained that her less than ample breasts were messing up my singers acoustic sound for the rest of the audience and how they didn't have anywhere near the mass, texture, or density to help with this 1khz ring problem I was having. Well, she looked at me as if I had antennae's growing out of my head....totally clueless. Are schools really that bad nowdays?


So, I got a better idea. I told her just how damn hot she looked in that leather biker jacket that was hanging on the back of her stool and how much I wished she would wear it for me......that worked. This rounded off the diffraction points and turned her whole body into more of a cylindrical shape, which really helped out my 1k ring. I had also told her she was free to touch any of my strings as long as they were on the headstock side of my hand.


This solved about 4 problems in one fell swoop. The sound improved in 2 areas, she was able to get down up close and interact with the band, and I didn't have to do anything nasty considering I didn't know where that's been but wherever it was couldn't be good, especially considering her equally wasted oldman/biker boyfriend. In the end a good time was had by all.




Moral of the story?.........there is no blanket solution that is the best for everybody in every case, wvery time. If a PA cab gets you a aound you like, run with it. If a bass cab gets you a sound you like....run with it. Don't be confused by labels....follow your ears....


problem I was having.

[Arjank]

Allways good to see some humor on these threads, thnx will33!

[Arjank]

Originally Posted by agedhorse

Not every speaker philosophy is right for every player, not every bass is right for every player and to think so is ignoring personal preference, tastes and choice.

This is very true.
I never said that "flat" or "neutral" cabs are good for any bassplayer, the cab I build works excellent for me (and all other bassplayers who tested it).
IMO it's easier to get several good sounds out of a "neutral" cab (with the help of the bass and/or pre-amps tone controls) then to get that out of a cab with a baked in sound/character.
With only a few knob twist I can get any tone I want, from deep reggae bass, up to Stanley leadbass tones.

[Arjank]

Originally Posted by DrumsAndBass

I spent considerable time trying to balance the sound of that stack - 410 on top of the JBL and it was tough to get it right. Some notes just jumped out and were quite a bit more pronounced. Was that a phasing deal ?

Could be.
I have no experience with that JBL unit, in most of these cases a DSP would do the trick, then you can fiddle around with different slopes and time allignments.
Btw. is that Aguilar 410 ported? Maybe you should close the ports, that may give you a better chance of getting it work together with that sub.

[Tommy504]

I'm playing exclusively through a PA system right now. My duo has bass, guitar, drum machine, vocals. Running through vintage Peavey SP2 PA speakers. They are 1X15 (Black Widow) with a horn. My Fender jazz never sounded so full. Must be the wood cabinet...I love it. I would recommend trying before buying. I did. Sounds better than my GK unit IMO.

[agedhorse]

Originally Posted by Arjank

Allways good to see some humor on these threads, thnx will33!

I agree, got a good laugh out of me too.

[agedhorse]

Originally Posted by Arjank

Could be.
I have no experience with that JBL unit, in most of these cases a DSP would do the trick, then you can fiddle around with different slopes and time allignments.
Btw. is that Aguilar 410 ported? Maybe you should close the ports, that may give you a better chance of getting it work together with that sub.

The problem is the low pass filter on the sub causes a 720 degree phase rotation through the crossover point (say 90Hz), so if the top cabinet was not high passed complimentary, then these phase shifts would cause significant ripple from say 80-120Hz, that's a pretty big chunk of acoustic territory. Since it's a LR alignment. the corner is pretty soft by comparison to a BW alignment.

It ay work ok, but this is an instance where the engineering says there may indeed be a problem in spite of everything else, so trying before assuming it's ok is wise advice.

With a high pass on the top cabinet, I wouldn't expect there to be a problem, but that assumes that the signal routing of the bass amp itself would allow for this.

I should also say that DSP correction is not likely to solve the problem because it's time domain based and any single delay that might seem like a solution just moves the problem around a bit. This is something that we do consider in depth in the pro audio world.

[Downunderwonder]

Originally Posted by will33

So, last weekend we were playing at this bar in Brenham called Lil Mikes. There was this one chick who'd been partying all day who was getting way too close for comfort, dancing on cables (suggestively dancing), reaching past my mic stand touching my bass, making weird eyes, etc. She had these small, but really pointy, breasts that were causing a diffraction problem from the main that was right there to my left and taking the sparkle out of our acoustic guitar for the rest of the crowd. At first, I pulled my neck back and gave her a face like "you're too close" but that didn't seem to do much good. She invaded my space even further next tune and I even made a comment to my bandmates between songs that if she did that again, I was going to kick her.

Then my cooler head prevailed. I talked to her on a setbreak and explained that her less than ample breasts were messing up my singers acoustic sound for the rest of the audience and how they didn't have anywhere near the mass, texture, or density to help with this 1khz ring problem I was having. Well, she looked at me as if I had antennae's growing out of my head....totally clueless. Are schools really that bad nowdays?


So, I got a better idea. I told her just how damn hot she looked in that leather biker jacket that was hanging on the back of her stool and how much I wished she would wear it for me......that worked. This rounded off the diffraction points and turned her whole body into more of a cylindrical shape, which really helped out my 1k ring. I had also told her she was free to touch any of my strings as long as they were on the headstock side of my hand.


This solved about 4 problems in one fell swoop. The sound improved in 2 areas, she was able to get down up close and interact with the band, and I didn't have to do anything nasty considering I didn't know where that's been but wherever it was couldn't be good, especially considering her equally wasted oldman/biker boyfriend. In the end a good time was had by all.




Moral of the story?.........there is no blanket solution that is the best for everybody in every case, wvery time. If a PA cab gets you a aound you like, run with it. If a bass cab gets you a sound you like....run with it. Don't be confused by labels....follow your ears....


problem I was having.

You win the internetz for the year, nominations remain open but doomed to fail.

[Arjank]

Originally Posted by agedhorse

The problem is the low pass filter on the sub causes a 720 degree phase rotation through the crossover point (say 90Hz), so if the top cabinet was not high passed complimentary, then these phase shifts would cause significant ripple from say 80-120Hz, that's a pretty big chunk of acoustic territory. Since it's a LR alignment. the corner is pretty soft by comparison to a BW alignment.

That 720 degree phase rotation is pretty nasty, the highpass should indeed be 8th order to to work. It will also not be easy to highpass that 410 to get that same slope. IMO such high orders are way to steep. They, ofcourse, have their purpose.

Originally Posted by agedhorse

I should also say that DSP correction is not likely to solve the problem because it's time domain based and any single delay that might seem like a solution just moves the problem around a bit. This is something that we do consider in depth in the pro audio world.

I only mentioned DSP because it's the best way to create a suitable low- and highpass on these low frequencies. But that would, in this case, mean one has to bypass that jbl crossover, use seperate poweramp(s) and insert a dsp between the sub and the 410......A pitty that jbl dsp is not accesable through usb else you could reprogramm it.....

[Downunderwonder]

HUH? 720 degrees is right back in phase.

[Arjank]

Originally Posted by Downunderwonder

HUH? 720 degrees is right back in phase.

Actually we have to look at the slope of the lowpass which is 48dB/oct(8th order) in the case of the jbl sub. To make things work the highpass needs to have the same (mirrored) (acoustical)slope. Some people make the mistake in only looking at the electric slope, it's the acoustical slope that matters.
Same with designing passive crossovers, I don't think in terms of LR, Bessel, Butterworth or whatever. All I want is that both drivers have a nice mirrored acoustical slope that sum nicely.

[Downunderwonder]

Baffling, good job.

I don't concern myself with trying to battle phase differences, I don't have the gear to analyse or do anything about it. My lo-tech biamped experiments have been a revelation with a steep crossover, blowing away my mixed full range cabs which aren't too shabby. But it's lots more gear to drag for a bass rig.

At my jazz gig I'm direct into a subwoofer PA with a Crown XTI2000 crossover, total overkill for the venue. It's some juicy bass, I have to trim my low end more than usual to stop it booming but otherwise it's sublime, lucky me, not a bass cab to be seen.

[Arjank]

Here a short example of good and faulty summation of a 15" and 8" driver. I used Boxsim to simulate it. The simulation shows a 15" and an 8" mid in a regular sized cab (bafflestep is taken into account with this simulation).

Example 1 shows the result with an 24db/oct aktive lowpass @150hz(Q=0.7) of the 15" and an 24db/oct aktive highpass @150hz(Q=0.7) on the 8" mid. Flat response, nice summation, no phase issues here.

Example 2 shows the result with the 24dB/oct highpass changed to 12dB/oct..... the summation suffers, phase issues here.

Example 3 shows the result with the highpass changed to 6db/oct. At this point I had to reverse polarity on the 8"mid, else the result was even worse.

As you can see, different acoustical slopes give bad summation, thus, phase issues.
If we look back at combining the jbl sub with it's 48db/oct lowpass @90hz and the 410 Aguilar (which is ported?) we can without doubt say that this will not work properly because that situation is worse as in example 2 and 3 that I showed here.

[Arjank]

Here's the simulation of example 3

Btw, If there is a need to, I can also post the phase response of example 1 and 2.