Speaker Ideas for 500 bucks

[jteef]

First of all, I listen to a whole lot of electronica with a lot of material in the lower octaves.

I would love to stick with a 2 way setup, but everything I have tried to model thus far doesn't seem like it will work very well. i.e. woofers needing to be lowpassed at 800-1200hz vs tweeters needing to be high passed at 1.5-2khz. A substantial gap. I realize I am not going to get an F3 of 30hz in a 2 way sealed cabinet like I want so 50-55hz might be more reasonable. I am hesitant to go ported now because the music i listen to is relatively fast and these will likely be delegated to a surround sound role when I have the opportunity to build or buy what I want for my mains.

One thing I have considered is adding a 1-3 ohm resistor in series with the voice coil of the midwoofer to raise QES and shift the F3 down 10-20hz. I know this will kill the efficiency, and increase box volume, but I should have plenty of power. What are the other effects this might have on the sound ?

I would like to keep each channel all in one cabinet no taller than about 4 feet high and 12-15" square on the bottom. Going to a 3 way design, or even an MTM will likely push me over budget. I might consider a pair of bookshelf's and a separate sub, but then money and power start to become the determining factors.

I have 120 watts x 2 into 8 ohms, and around 190x2 into 4 ohms (until i can upgrade the transformer) to work with now, and I will probably build another amp with some the national semiconductor overture series IC's for 40 or 50 more watts per channel available for biamping.

Any ideas or designs you have had success with given my parameters?

Thanks a lot

jt

 

[kelticwizard]

A) Is that 500 bucks going to include the cost of the enclosure itself-the wood, glue, etc.-or the cost of the drivers and crossover?

B) Why do you think that acoustic suspension crosses over higher than ported designs? If anything, a ported design suppresses cone motion, (but NOT output), through it's greatest range-the lowest octave. This makes for less intermodulation distortion through the midrange. Anyway, I don't think you are going to get a two way that goes down to 30 Hz, ported or acoustic suspension.

Assuming that the 500 bucks is for drivers and crossover only, I think your parameters for 30 Hz through 20,000 Hz and up for 500 bucks can be met. It would be a 3 way, though.

[Edited by kelticwizard on 10-19-2001 at 10:11 PM]

 

[ThomasW]

Might want to consider these, completed they'll end up right in your budget.

http://www.adireaudio.com/cd/kit281.htm

Numerous builders have been very pleased with the performance. If you want to ask question of builders post on the DIY section of HomeTheaterTalk forum. They had many builders due to a group buy a while back

 

[jteef]

If i implied that i thought acoustic suspension crossed over higher than ported, i didn't mean it. I mean to say that of the drivers i have modeled so far, they all needed to be crossed over fairly low. I understand I wont see 30hz in a sealed 2 way design, so I am willing to give up some low end for now. If I can get down to 50-55, I will be satisfied.

I've looked so far at the focal 7k4411, scan speak 18w/8545 and 18w8546, and peerless 850122. I guess I could go 3 way if i used cheaper drivers. But then I am into another amp for the mids, or expensive passive xovers.

$500 for drivers, electronic crossovers and 2 sheets of mdf. So figure about $420-450 for the drivers. Exact figures aren't of great concern, but I would rather stay closer to $500 than $600.

jt

 

[ThomasW]

The ScanSpeaks have approx 50% more Xmax and much lower Fs (28Hz), so they're a better choice than the Focals. But like most 6.5" drivers they are limited as to how loud they can play in a 2-way MT config. In a MTM config they would be extremely good, but $$$$

You might find Tony Gee's Andromeda of some interest.



[Edited by ThomasW on 10-20-2001 at 08:42 AM]

 

[kelticwizard]

One woofer I would recommend would be the Peerless 831727, a 10 1/2" model. This used to be one of the best subwoofers you can buy. The super-pushers have taken over, but at + or - 9 mm, this one still isn't that far behind today's new subwoofers.

Available http://www.madisound.com for $54. The crossover to the midrange-both lowpass for subwoofer and highpass for mids-together should cost about $25 or less. This is for a 200 Hz crossover You want to spend no more than $225 a side. So far, you have only spent $90.

With that big woofer expense out of the way, you should still be able to afford an MTM configuration, crossing over to the Peerless 10 1/2 inchers at 200 Hz or so.

The MTM configuration using 6 1/2 inchers is nice, but consider intermodualtion distortion. The highest notes on the piano are about 5,000 Hz. If you cross over at 2,000 Hz, (about an octave below), then all but the top octave on the piano will be played by the same woofers you expect to pump out bass at 45 Hz or so. There has to be muddiness.

At 2 cu ft., the Peerless 10 1/2" is 3 dB down at 30 Hz. At 3 cubic feet, it is 3 dB down at 25. These volumes and prices are well within your parameters.

Remember, two mids require only one crossover. Two 5" or 6 1/2" mids, a 1" tweeter and crossover should be possible for $135-the remainder of your $225 per side budget.

You should be able to have the focus of an MTM plus the bass of a real subwoofer for your price.

This is just a suggestion.

[Edited by kelticwizard on 10-20-2001 at 01:42 AM]

 

[ThomasW]

The Peerless is an interesting budget woofer, but will most likely have problems functioning as a 'subwoofer' given the fact it starts to roll-off pretty quickly below 75Hz. Also one should consider poly cone breakup modes and the fairly small 39mm voice coil. It's always best to use drivers in the FR range where they are most pistonic/linear=flattest response. This avoids most distortion based problems

[IMGDEAD]http://www.peerless.dk/data/freq/831727.gif[/IMGDEAD]

[Edited by ThomasW on 10-20-2001 at 02:03 AM]

 

[baby_huey0]

Well this is definitely a thread I can go with. For the last 3 months I have been designing a set of speakers. In your budget you mentioned on about $50 for crossovers. As I quickly found out, this is not enough for a 3way speaker. The price of my speakers have doubled from $500 to $1000(Canadian) very easily.

You also mentioned using Focal or Scan-Speak. These drivers are very expensive, I know they are less in the US but they still aren't cheap. Something from Seas, Audax, or Peerless migth be a little cheaper and still give you great sound. The Seas or Audaxs were recommended by Tony Gee to me. I'm using all Seas drivers: 25TAC/D, P17REX, and P21REX. It comes out to about $570cdn, which is about half that American probably(between taxes, exchange etc.)

I think in the end I would agree with ThomasW on the Kit281s. They would probably give you enough low end to satisfy your needs. Also with the money you would save under $500 you could save it to buy a Shiva, then all your bass needs would be satisfied.


[Edited by baby_huey0 on 10-20-2001 at 07:59 AM]

 

[Super]

Another project I've seen for 500 bucks can be found at http://www.speakerbuilder.net

Take a look at the Veritas speaker. It uses a ribbon tweeter, dome midrange, and has dual 10 inch drivers in a sealed cabinet. It could be what you're looking for.

 

[kelticwizard]

In reference to the Peerless 10 1/2 inch subwoofer, Thomas W. wrote:

"will most likely have problems functioning as a 'subwoofer' given the fact it starts to roll-off pretty quickly below 75Hz."

Thomas, the chart you showed is one of the Peerless subwoofer in free air!

If you took the free air response of the Shiva, it would have almost exactly the same response curve as the Peerless. It will roll off gradually down to 21 Hz, where it will be about 8 dB down, (the Peerless will be 9 dB).

Bass reflex and even sealed boxes require woofers with a low Q to start with. That means at the free air resonance, they will be several decibels down. Any quality subwoofer designed to go into a reflex or sealed enclosure will be the same way. When placed in a box, the low frequency range raises up.

I have used these woofers, and I am more than satisfied. As far as the voice coil goes, yes it is only 1.5 inches diameter, but it is a 4 layer wound on a fairly long voice coil, (1 inch). The Peerless is rated at 220 watts music power.

Poly cone breakup? Well, I haven't measured it, but most breakup starts in the higher ranges. Cross over at 200 Hz, and it probably won't be much of a problem.

The Peerless SWR 260 is an older subwoofer, but it was ahead of it's time. It has a shorting ring to prevent voice coil "suck in", (a condition where as the speaker approaches the tuned box frequency, it travels from the midpoint to the end of it's voice coil and and clips the wave form in one direction). American subwoofer manufacturers virtually ignored the problem, European manufacturers dealt with it only on extremely expensive models. The SWR 260 dealt with it at a resonable price.

This speaker may or may not be the way for jteef to go. It has been superseded by other subwoofers now, but at much greater cost. At $54 each, I think it is a good place to look when building a "keep it under budget" system.

[Edited by kelticwizard on 10-20-2001 at 11:46 AM]

 

[kelticwizard]

Jteef:

You mentioned cost as the reason you did not want a sub/satellite combo. Two Peerless 260's and one Shiva cost about the same. With two 8 ohm voice coils, crossing over at 200 Hz will cost the same, passive crossover wise, as to the Peerless or any low frequency speaker. Even a 150 Hz crossover would not be that much more.

The maximum box size you mentioned-48" high, 15" square-will yield an internal volume, (assuming 1" building materials) of 4.5 cubic feet. Enough to put a Shiva into and go way down into the low twenties for a 3 dB cutoff.

The sub/satellite idea, using the Shiva, might be posible within your budget.

 

[ThomasW]

Wiz...

Of course the plot is free-air, ever seen a mfgr's plot that wasn't?

Oh, and thanks for the box design tutorial. I'd appreciate your learned assistance for our next project, it's a klone of the Krell MRS sub.....

BTW, cone breakup can easily occur at lower frequencies, depends on how hard the unit is being driven. Poly is the least rigid of any of the commonly used cone materials.

Regards
ThomasW
http://www.Klone-Audio.com

 

[Super]

ThomasW: Would you happen to be one of those who runs the Klone-Audio site? If so, when are we ever going to see some SLAMM Klone updates?

Sorry for the inconvenience.

Oh, and Keltic: When you said that the Shiva would be -8db at 21 hz, you are referring to the free air resonance, right?

 

[jteef]

The shiva kit281 doesn't appeal to me. Mostly because of the crossover. I think I can do better.

Although it isn't essential, I would like to stick with active xovers. I think the speakers I was referring to above might work fine in a TM design if I can notch out the large peaks that many of these drivers exhibit around 2khz before they really break up. This way I can still use nicer drivers and stay within budget.

I'll probably end up building a sealed test enclosure to see if the bass is satisfactory in the room

I will wait to see how the LM3886 amp turns out before I decide to go 3 way. Although, I kinda wanted to keep my leach amp on the midrange.

What about something like the Seas T17RE in an MTM design? Vented it would have an F3 of about 45 hz and be pretty cheap. sealed F3 is a high 75hz. Any comments on the series filters that are shown on Tony Gee's page ? I've never used anything like them before, but they seem to work well.

keep the ideas coming!

thanks a lot

jt

 

[kelticwizard]

Super:

Yes, that is for a free air woofer. The formula for the output of any free air woofer at resonance is given by: 20 Log Qts. So in free air, the Shiva, at .39 Qts, is down 8.18 db from the midpoint when it hits it's free air resonance of 21 Hz. The Peerless, at a Qts. of .34, is down 9.4 dB from the midpoint.

For illustration, check out the output of the Swan 12 inch at http://www.madisound.com. Also, a Skaaning woofer response can be found at http://www.flexunits.com Click flex units-specification for 12"-. Note the specs page: Fs=25 Hz, Qts=.3, sensitivity=92 dB. Then click Frequency Scale.

Note that the speaker is 84 dB at 25 Hz resonance. The sensitivity is listed as 92 dB, but it sure looks like 94 dB from that chart.

In both the Skaaning speakers and the Swan speaker, the output starts rolling off around 60 or 70 Hz. Any speaker with a Q lower than 1 will do a gradual rolloff down to it's resonance frequency.

However when enclosed and ported, the story changes entirely. No more rolloffs from 70 Hz down.

The Shiva, for instance, when enclosed in a box equal to it's Vas, and tuned to it's free air resonance, (21 Hz), will be 3 dB down from it's midpoint.

PS: The chart on the Shiva white paper is for an enclosed woofer. It is not a free air chart, (I am not saying you thought it was).

[Edited by kelticwizard on 10-20-2001 at 08:33 PM]

 

[ThomasW]

Super

Yes Klone-Audio is my site. The projects are a collaborative effort between JonMarsh and I. We've been designing and building speakers as a team for more than 30yrs.

Jon's finally frozen the X-1 top module XO design, I'll be uploading that data later this weekend. He decided to forgo a Audio-X-Press article for the SLAMM's, so everything will be posted to the website as the documentation is finished.

There will be an Audio-X-Press article published for the latest M8 project. Actually jteef might find these of interest, Focal 8V4211, combined with a MBQuart TT1. There's a thread about them on the DIY section of
http://www.htguide.com/CFBoards/index.cfm?CFB=1

[IMGDEAD]http://server2045.virtualave.net/ttriff/M8_PrelimView.jpg[/IMGDEAD]

 

[kelticwizard]

Thomas W:

I freely bow to your superior audio knowledge as displayed at your excellent and informative website.

However, you did claim in your post that the Peerless has a rolloff below 70 Hz, and used the free air response as evidence.

Are you saying that this rolloff will occur if the Peerless is enclosed in a 2 cu. ft box and ported to 30 Hz?

If it does not occur in the enclosed box, why post the free air response as an illustration that it will?

Not all readers of a discussion forum post there. The enthusiastic novice unfamiliar with the way ported and sealed boxes work, when searching for his low frequency driver, may well be doomed to examining free air response chart after free air response chart, 70 Hz rolloff after 70 Hz rolloff, until he throws his hands in the air. Indeed, he is likely to conclude that flat response down to 30 Hz and below is a myth, as any examination of the manufacturer's free air response chart will show!

Surely, we don't want that to happen.

 

[Super]

jteef: Seas drivers are an excellent value for the money. Personally, I'm pretty much a Scanspeak only man nowadays, but I don't exactly have the funding for a few pairs of carbon fiber/paper cone drivers. However, for electronica, I'd more than likely sacrifice optimal midrange "warmth" for 2 drivers if cost permitted me to go with 4 good quality drivers for an MTM. In any event, it sounds like your going to be needing a sub, so I wouldn't fret too much over the f3 of your midrange drivers. In fact, considering the low, fast beats often found in electronica, you may want to consider the use of a multi driver sub, or better yet, stereo sub (or, theres always the "Grey option" of 12 subs, heh heh)

 

[ThomasW]

Wiz

Items people should consider for subwoofer design include, cabinet/alignment, baffle shape/baffle size, cabinet construction, effects of room gain/room placement, size of room and desired SPL's.

For those designing subs on a budget, Unibox is a very good and accurate freeware modeling program, it doesn't have the glitches inherent in WinISD. For those with some disposable income, LspCAD/LspCAD Pro are extremely accurate and powerful modeling tools.

Hope this eliminates any possible confusion that was created

Regards
Thomas

BTW, guys what's wrong with using 12-12" subs?

[Edited by ThomasW on 10-21-2001 at 01:52 AM]

 

[baby_huey0]

My guess is your trying for something like Tony Gee's Proteus design. Try emailing him if you have a question.

I think I agree with Super, a sub might be essential for the low range. Being the bass head I am ! Something like the Seas P25REX might be good without killing you budget.

But as to the limited amount of knowledge I have, I think the rest of these guys in here could recommend some other(probably better) drivers.

Cheers
Jeremy Hopkins

BTW There is absolutly nothing wrong with 12-12" subs!