Speaker Types....

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Im looking to get a sub for an amp im building but i need some help on picking the right one, I need a 400w rms minimum with a fq response of somewhere between 20-35hz to 600-1200hz
with a sensitivity of 98+ db

does anyone have any suggestions on what to go for in a price range of £120?

ps. it has to have a nice fq response line
diyAudio Moderator Emeritus
Joined 2001
First, you did not mention how big an enclosure space you have available.

Second, how big a speaker did you have in mind? A 12", 15", or 18"? This is related to the first question.

Third, on a typical 15" PA cabinet of 3 cubic feet, the -3dB cutoff is generally around 55 Hz-if you want to go deeper, you have to make the cabinet larger. Forget those published ratings-those are invariably misstated to make the frequency response seem much lower than it is.

Since you said you needed "to get a sub for an amp" I assume you are talking professional equipment. Usually, only professional equipment has sensitivity ratings so high. It is typical for pro equipment manufacturers to exaggerate the sensitivity of their speakers by 3 dB or so. If your speaker is within 3 dB of the pubished spec, it is to be considered OK. I mean, almost all of them do it. Some exaggerate worse than 3 dB.

To check, download one of the loudspeaker design programs that gives you the actual sensitivity as figured from such published measurements as Vas, Qes, etc.

Finally, be aware that professional equipment is made with relatively short voice coil and excursions compared to the best home equipment. This is one of the factors that gives it such a high sensitivity rating. This factor will tend to hold down the total amount of air you can move, and therefore limit the the SPL of your deepest bass notes. Of course, you can overdrive them out of the linear zone, if you want to.
diyAudio Moderator Emeritus
Joined 2001
One of the programs that gives the sensitivity of a speaker from it's Vas, Qes, and other measurements-a more accurate method than going by published specs-is BoxModel. It is a free download. It will also predict the results of any speaker when placed in a box of a certain size, and tuned to a certain frequency-but then, any speaker program will do that.

Eminence is a very popular speaker. It is one of those which exagerates the sensitivity by 2 or 3 dB, but then, so do most others. It is frequently available for considerable discount at Parts Express, www.partsexpress.com. I think they ship overseas.

I have also heard some good things about McCauley speakers.

A friend in Cork, Ireland, who runs a DJ business used to swear by Eminence, but has lately become somewhat disenchanted. He has heard good things about Volt loudspeakers from DJ friends in England, but has not had time to check them out.

One of the impressive things about Volt is that their sensitivity specs match their specs for Vas, Qes, etc. Which means that they are honest about the sensitivity of their speaker. Refreshing. One 15 inch, the 3823, has a really smooth response-for a PA speaker-right through the range you mentioned.

The sensitivity of the 3823 is 96 dB, but it is an honest 96 dB. So it is the equivalent of 99 dB listed the way other speakers list sensitivity.

Alas, I do not know the price of the Volts, but you can check that from contacting the distributors listed on their website. Here is the frequency response for the 3823:


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diyAudio Moderator Emeritus
Joined 2001
Another word about the Volts. Because there is more magnetic material behind the voice coil than in front of it, PA speakers often experience a phenomenon where at resonance, they travel all the way back to the end of their travel and give out a clipped waveform. High quality hi-fi speakers often deal with this situation, PA speakers rarely do. The Volts' design appears to deal with this problem, though I have not confirmed this.

Finally, Volt also has an 18" speaker, the 4504, which is also rated at 96 dB. We can expect that to be an honest 96 dB like it's 15" brother, therefore equivalent to others' 99 dB. The thing about this speaker is that it has an incredible excursion-for a PA speaker-of (+ or -) 10 mm linear. It can go (+ or -) 25 mm mechanical-two inches throw!! Unheard of for a PA speaker. With a throw at least twice what other PA speakers put out, the 4504 should output 6 dB more deep bass than other PA speakers with half the excursion.

If these specs are anywhere near accurate, what a monster the 4504 must be!!

Click on "Loudspeakers", then "Radial", then picture.

Graph below.

Let me emphasize that I have never used the Volts, so I cannot say for sure what their quality is. But they look very good, their specs are consistent with each other-which other manufacturers' are not-and they have some interesting design ideas.

I hope I given you some possible options for investigation.


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I personally have never had any problem with <a href="http://www.jblpro.com/pages/components/componts.htm">JBL pro</a> speakers not meeting spec. Read the design performance dislaimer on their spec sheets: doesn't sound like someone making false claims. Had good luck with <a href="http://www.electrovoice.com/">EVs</a> too. I hear very good things about <a href="http://www.mccauley.com/mainframe.htm">McCauleys</a> ( I want to get some to play with),<a href="http://www.beyma.com/"> Beyma</a>, <a href="http://www.fane-acoustics.com/pages/misc/aboutc.htm">Fane</a> and Precision Dynamics (no link, don't sell to public) from people who use them hard day in day out. Eminence and Selenium woofs I have no experience with yet, though I have two Eminence Omega Pro 18s on order, and will be getting about a dozen 12" customs for the new basshorns that will be built mid year.

The Volts are available from <a href="http://wilmslow-audio.co.uk">Wilmslow Audio (UK)</a>. The prices are on their <a href="https://secure.wilmslow-audio.co.uk/acatalog/Wilmslow_Audio_Volt_Drive_Units_22.html">Volt page</a>. The RV 4504 radial lists for UKP 392.77 ex VAT, and the smaller 15" R3853 for UKP 205.18 ex VAT. Not exactly cheap, but not bad for pro drivers. For example here some of the JBL 18"s list for about the equiv of UKP 650, and the PDs can be near to $US2000 / driver.

The Volts have interested me for some time because of their apparently well thought out design and funky looks, but aren't available here and small quantity imports are an expensive PITA. <a href="http://www.pmcloudspeaker.com/">PMC</a> use the radials in a few of their monitor systems.

AudioFreak---Some 15" prosound woofers meant for motion-picture theaters and studios sound very good even at frequencies well above 1000hz, Altec 604 and 605 co-axes cross at 1600hz and sound very good. Getting the highs out is simply a matter of low-mass paper cones and a very strong motor. There may be break-up modes but evidently judgeing from the good sound of these drivers there are worse things that can happen.
AudioFreak----You can raise theoretical objections to any design, all have compromises but Lansing and Hilliard were exceedingly clever designers with ample resources, the proof of the pudding...... Note that the 15" driver of the 604 is of extremely high quality: 3" edgewound coil in a very narrow underhung gap, 4 pounds of Alnico. I hope some time you get to hear a set of Altec DuPlexes, I presume you've heard the Tannoy Dual Concentrics down in Oz, very similar. Besides, a great deal of the music you listen to was probably mixed on Altec 604s and 605s, on so much music they just sound so "right". Great speakers for the music-lover.
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