Cabinet Design for Bass

[GregS]

I have just built an Ampeg Portaflex B15N clone and am trying to figure out a cabinet design.

I like the vintage sound of the B15N but I also need as much volume as I can get from the cab as the amp has limited power and headroom (25-30W I think) and I'm using it in a band.

I tried it out with the band using a rented Traynor 1x15 cab with it. This cab is short but deep with ported openings in the corners of the baffle. At the high volumes of the band I'm not getting good definition on the lowest notes as I'm at the limit of the headroom I suspect. Also, I find this setup is lacking some higher end component that gives more crispness and definition to the notes. It could be the amp/cab I'm used to playing has tweeters/horns that can produce these frequencies or maybe this is the characteristic sound/feel of the B15N.

Originally I was planning to build a cabinet with a single 15" speaker as the original Portaflex had but now I'm wondering about using a 12" speaker and a detuned cabinet design where the port is the same size as the speaker hole. I'm thinking I may get more higher frequency content with the 12" speaker and more apparent loudness as well which would make it better suited to the band. I could be wrong..... The concern I have about the 12" speaker is that I won't have enough bass response.

To summarize, I want to build a cabinet that will give the most loudness for a given power level and hopefully retain the vintage sound as well.

All thoughts, opinions welcome as I don't have much experience with this.

Thanks,

Greg

[Bill Moore]

Look at the EV TL plans.

I don't have the plans handy, but the EV TL series work great. I built one for my wife years ago, the small 3 cu. ft. with an EVM-15B, freq. to 40 hz. We took it to a jam sesion one time,(powered with a Cerwin-Vega BG-250), and another bass player I had worked with in the past got on me about it. When he got up to play, he kept looking at the cabinet, and after we finished the tune, he told me,"this thing blows your pants legs". Built him one sometime later.

[the wizard]

try the talkbass forum here's a link

http://www.talkbass.com/forum/forumdisplay.php?f=15

[GregS]

Thanks for the reply. I found some plans on this forum for a EV TL606 cabinet. I assume these are the plans you were referring to. I am considering building this but am undecided at the moment if I want to build this or a detuned cabinet. Also if I go with the detuned cabinet do I want to use a 12 or 15 inch speaker.

Is a 12" speaker unsuitable for bass? If not, is a 12" speaker better for loudness when you have limited power as in my case? All other things being equal will a 12" speaker produce more high frequency content than a 15"?

If I go with the EV TL606 plan I understand I will also need to get the EV 15" speaker it was designed to work with. Do you think this will work well with a 25W amp? (i.e. good volume and headroom)

Thanks,

Greg

[GregS]

Great. Thanks for the link.

Greg

[black_labb]

reguarding 12's vs 15's, how much high end really depends on the individual speaker. the 12 will have less rolloff of the highs when you are standing off axis (as in the speaker not facing you) but both will have better dispersion of the highs than a traditional 4x10. i'd probably suggest a 15" as they are usually more sensitive due to the extra surface area to move the air. aim for a sensitive speaker, as 25w isnt very powerful. being 25w, you will be able to use any 15 or 12 that is designed for the frequencies bass guitar put out.

[Steve Conner]

I was surprised by the results I got from an EVM12L in a Thiele cabinet. (I got the "Classic" reissue and made my own cab.) It won't reproduce the fundamental of the low E, but with only 25W you don't want to waste power doing that anyway.

If you want to be heard with low power, you have to bark your way through the mix with lots of midrange and distortion harmonics, and a 12 probably does that better than a 15, because the smaller speaker has more midrange response. Health warning: Unless you actually play in a power trio, or are Jaco Pastorius himself, sound guys will hate you and your rig, for stepping outside of your allotted frequency band. Heck, they probably tried to make Jaco turn his midrange down because it was bleeding into the conga mics

For bass, I would prefer a properly tuned cabinet to a detuned one any day. Regardless of what internet experts say about its "huge bottom end", the detuned cab doesn't load the speaker properly, and risks over-excursion of the cone even with low power.

Two low resonance Greenbacks in a ported 2x12" might be interesting too.

[txstrat]

..., I find this setup is lacking some higher end component that gives more crispness and definition to the notes. It could be the amp/cab I'm used to playing has tweeters/horns that can produce these frequencies or maybe this is the characteristic sound/feel of the B15N.

I found the B-15N circuit is sort of lacking the highs and crispness after I'd build one. I even changed the bright function to B-15R specs (with an added resistor) to help that out. No such luck.
A 12'' speaker would only put out less deepness but not more highs IMHO.

Figured I have (or better the bass player in my band has) to live with it. It's got a gorgeous sound anyway. Not for slapping, though.

[GregS]

It's got a gorgeous sound anyway. Not for slapping, though.

Yes, I agree. I'm getting more used to it with the band and liking it more all the time.

For bass, I would prefer a properly tuned cabinet to a detuned one any day. Regardless of what internet experts say about its "huge bottom end", the detuned cab doesn't load the speaker properly, and risks over-excursion of the cone even with low power.

Is this because the air is too easy to move with this design? I would think if I get a speaker with reasonable power handling capability I should be ok.

I've also been considering the EV-TL606 design. It is designed for the EVM-15L driver. However, I didn't notice this on the EV site - only the EVM-12L. Is the EVM-15L still made and available new?

Greg

[billyz]

I believe the EV TL806 is designed for the 12" speaker. This is proven design and it works well with many other speakers too.

http://archives.telex.com/archives/E...rs%20Plans.pdf

[Steve Conner]

Yes, if the hole is too big, the air inside the cabinet just rushes in and out rather than offering any resistance to the cone, so low notes make it flap around wildly. With a properly tuned cabinet, the cone is held back and prevented from rupturing itself, at the same time as the air motion in the port hole is generating extra bass. It's almost like a free lunch.

I guess no matter how badly you mistune a vented cabinet, it can't be any worse for cone excursion than an open-backed guitar combo like the Fender Bassman. And Fender intended people to play bass through those, too.

AFAIK, the EVM-15B is no longer made. Warehouse Guitar Speakers do some nice cast frame 15s, and Eminence have a big selection of regular steel framed ones. Jensen make vintage reissue 15s that might suit a tube amp well, and in the UK and Europe you can get the Celestion Truvox.

TL-806 is for the 12", TL-606 for the 15, IIRC.

[Albert Kreuzer]

I like the plans for the TL606Q
Always wanted a 4x15" just to scare them guitarists.

Cheers,
Albert

[txstrat]

You might look at this thread about the Kappa 15 in a small cabinet:
http://www.music-electronics-forum.c...ad.php?t=11397

A 4x10 would be good as well due to the bigger surface.

Be aware that a bass amps cabinet can put out it's full volume in the fist place at a distance of about 8-10 feet. Due to the long waves of deep frequencies.

[GregS]

Thanks for the replies.

I think I'll try a detuned cabinet and 15" speaker. From what I've read in Kevin O'Connor's DIY speaker cabinet book the port hole size is large enough to not be critically tuned but not so large that it provides no damping. Also, with this design (according to the book) it is not critical to match the cabinet dimensions to the speaker.

I'll give it a try and if it doesn't work out I'll build another cabinet with a different approach.

Thanks again for all input in this thread.

Greg

[black_labb]

by the way, download win isd. its a cabinet design software that allows you to see the theoretical frequency response of the cabinet with certain size and tuning with a certain speaker.