Transmission Line vs Reflex Ported vs Isobaric

[CnoEvil]

Just wanted to know if anyone knows the advantages or disadvantages of each...in layman's lingo.

This would be in terms of quantity, quality and tunefulness of the bass produced.

I have heard that TL is more difficult to get right and so possibly more expensive to produce...as well as being drier sounding and possibly less weighty. I have also read this, which I don't know if it's true, and I paraphrase:

"Real world TL speakers like PMC are really quarter-wave TLs, ie. the line length is 1/4 the wavelength of the resonance frequency the bass driver is tuned to.

This means it's nothing but a Bass Reflex variant, that offers no real advantage over a classic Reflex alignment."

So any comments, preferences or insights would be much appreciated.

Cno

 

[drummerman]

My favorite subject ... na, not really

Personally I think, ports belong on the back, better still radiate downwards but if they have to be to the front, a well damped transmission line is probably the way to go.

regards

 

[chebby]

Why have you left out loudspeakers with sealed cabinets?

The whole industry - barring a few exceptions - have left them out as well. Thirty years ago, sealed cabinet designs occupied every price point including low budget. (AR7s, Videoton Minimax and upwards.)

The world of hi-fi sounded much nicer as a result (better midrange for a start). Have these companies lost the skills they once had? Or is it just too expensive to make them nowadays?

 

[drummerman]

Makes me reminisce of the Sabre's I used to have.

Perhaps it is that cabinets as well as drivers were often larger. Perhaps its speaker sensitivty and show room appeal. It 'looks better' if a volume control is only at 9 ...

With the trend towards ever slimmer/smaller cabinets etc it was probably inevitable that IB's are not that common anymore.

regards

 

[Al ears]

Don't forget the sealed-box (EB2's for example).

I guess each design has its own merits dependant on size of the room. Whilst the reflex ported tend to be more common due to being easier to produce.

I have a thing about rear-ported designs as I have never been fortunate enough to live in a house with rooms large enough to adequately utilise this design. (Downward firing ports are acceptable however).

I have not heard an isobarik design for a long while, I still wonder why it never became more popular, driver costs I suppose.

 

[TheHomeCinemaCentre]

To my mind it is all in the execution - there are good and bad examples of each design. Much like LCD vs Plasma or diesel vs petrol there are pros and cons for each individual user. The great thing is there is plenty of choice.

 

[whiskywheels]

Why have you left out loudspeakers with sealed cabinets?

The whole industry - barring a few exceptions - have left them out as well. Thirty years ago, sealed cabinet designs occupied every price point including low budget. (AR7s, Videoton Minimax and upwards.)

The world of hi-fi sounded much nicer as a result (better midrange for a start). Have these companies lost the skills they once had? Or is it just too expensive to make them nowadays?

+1! Also, it seems to me that every other speaker review these days mentions 'giving them some air' and 'moving out from walls' etc. So we're supposed to put our speakers in the middle of the room? In the real world almost every one places them near a wall, and even, God forbid, in a corner!!

 

[CnoEvil]

Why have you left out loudspeakers with sealed cabinets?

The whole industry - barring a few exceptions - have left them out as well. Thirty years ago, sealed cabinet designs occupied every price point including low budget. (AR7s, Videoton Minimax and upwards.)

The world of hi-fi sounded much nicer as a result (better midrange for a start). Have these companies lost the skills they once had? Or is it just too expensive to make them nowadays?

I purposefully left them out because I grew up with them and have a much clearer idea of the advantages/disadvantages.

When looking at how to get that extra bass depth/efficiency from a cabinet, the above three ways are the most common, so I was just wondering about what made a manufacturer go for one, as opposed to the other.:

Proac/PMC - TL

Kef + most others - Reflex

Linn/Neat - Some Isobaric designs

One doesn't often see this discussed, as it's always Ported vs Sealed that comes up.

Maybe some of the speaker designers on here would like to chip in.

 

[CnoEvil]

To my mind it is all in the execution - there are good and bad examples of each design. Much like LCD vs Plasma or diesel vs petrol there are pros and cons for each individual user. The great thing is there is plenty of choice.

Yes, but if correctly executed, are there any characteristics of the sound that differ, due to the different implementations?

 

[oldric_naubhoff]

Transmission Line vs Reflex Ported vs Isobaric

none of the above.

 

[oldric_naubhoff]

When looking at how to get that extra bass depth/efficiency from a cabinet,

doesn't really matter. ports as well as TLs introduce low midrange noise. and this can actually be quite severe. but I gueass everybody prefers phat bass lines rather than ultimate midrange clarity. otherwise sealed designs would have never go out of fashion.

 

[oldric_naubhoff]

Linn/Neat - Some Isobaric designs

punishing for your amp.

 

[CnoEvil]

Transmission Line vs Reflex Ported vs Isobaric

none of the above.

I appreciate everybody's input, but almost all the answers are for a question I haven't asked.

I'm well aware of the advantages of a sealed cabinet and even Electrostatic/Maggie type panels, but am less sure about the 3 types I've mentioned in the title.....eg. Does the TL type design have a clear advantage, or is a lot of it to do with "marketing mystique".

Don't mean to sound ungrateful for input so far

Cno

 

[lindsayt]

Linn/Neat - Some Isobaric designs

punishing for your amp.

The Linn Isobarik speakers are punishing for amps because the idiot designer wired two nominally 8 ohm drivers in parallel for the bass, midrange and treble, resulting in 4 ohm speakers with dips well below 4 ohms. They'd be an easier amplifier load if he'd used 16 ohm drivers wired in parallel, or 4 ohm drivers wired in series. He also used relatively heavy medium sized bass KEF bass drivers - which keeps the efficiency down. It's no wonder that these speakers make good candidates for active amplification - just to give the amps an easier time.

Linn Saras are also punishing loads for similar reasons.

Ferrograph S1 speakers are basically half an Isobarik in terms of drive units, and possibly better speakers because of it.

I have a feeling that if you took all the drivers from an Isobarik and mounted them all on the front baffle of a larger box you'd have a better sounding speaker. Better imaging for a start, and more dynamic bass too.

The big advantage of the Isobarik design compared to the more conventional approach of putting all the drivers on the front baffle is smaller box size.

The Linn Majik Isobarik design doesn't work at all for me. You've got two bass drivers put inside the box with the sound from them coming out of the bottom and out of a port near the top front. It sounds like it too. Stupid idea. Echoey, boxy bass that can't start and stop like it should.

 

[CnoEvil]

The Linn Isobarik speakers are punishing for amps because the idiot designer wired two nominally 8 ohm drivers in parallel for the bass, midrange and treble, resulting in 4 ohm speakers with dips well below 4 ohms. They'd be an easier amplifier load if he'd used 16 ohm drivers wired in parallel, or 4 ohm drivers wired in series. He also used relatively heavy medium sized bass KEF bass drivers - which keeps the efficiency down. It's no wonder that these speakers make good candidates for active amplification - just to give the amps an easier time.

Linn Saras are also punishing loads for similar reasons.

Ferrograph S1 speakers are basically half an Isobarik in terms of drive units, and possibly better speakers because of it.

I have a feeling that if you took all the drivers from an Isobarik and mounted them all on the front baffle of a larger box you'd have a better sounding speaker. Better imaging for a start, and more dynamic bass too.

The big advantage of the Isobarik design compared to the more conventional approach of putting all the drivers on the front baffle is smaller box size.

The Linn Majik Isobarik design doesn't work at all for me. You've got two bass drivers put inside the box with the sound from them coming out of the bottom and out of a port near the top front. It sounds like it too. Stupid idea. Echoey, boxy bass that can't start and stop like it should.

Thank you for spelling it out further.

Are you saying that all Isobaric speakers are flawed with regard to the load on the amp (eg. Neat models), or is it that Linn's design is worse than most?

 

[gregvet]

I think most Isobarik designs tend to be fairly difficult loads, due to the doubling up of the drivers (I think there are more complex reasons too, i just dont understand them )

The Totem Mani-2's are supposed to be pretty well sorted sound speakers that sound great, using the Isobarik loading design. Maybe it works better for standmounted speakers than floor standers?

As an aside, in my experience the bass from transmission line speakers can sound quite different to rear ported speakers, although I dont fully understand why. IMO a well sorted transmission line speaker (IE PMC for eg) can have fantastic bass quality and quantity, from a relatively small enclosure. They are often easier to postition that rear ported speakers too

 

[Electro]

Transmission Line vs Reflex Ported vs Isobaric

none of the above.

I appreciate everybody's input, but almost all the answers are for a question I haven't asked.

I'm well aware of the advantages of a sealed cabinet and even Electrostatic/Maggie type panels, but am less sure about the 3 types I've mentioned in the title.....eg. Does the TL type design have a clear advantage, or is a lot of it to do with "marketing mystique".

Don't mean to sound ungrateful for input so far

Cno

In my opinion and based only on many years of listening to different types of speaker I would say that all different designs and types of speaker have their individual strengths and weaknesses but ultimately I have chosen speakers using PMC's version of a transmission line as the best all round compromise that suits my idea of what a HiFi system should do .

I think this is because they seem to produce the most life like deep textured bass with real pitch accuracy that does not overwhelm the rest of the music and you can also feel it as well as hear it.

Bass instruments sound like they are part of the music contained within a large sound stage and can be identified in the same way as all the other instruments with their own individual character and separate space much more like real bass instruments playing as part of a real live performance .

When listening to a well recorded piece of music especially a good live recording this real depth and cleanliness in the bass frequencies seems to free up the mid and top frequencies to create a wonderful deep and wide stage behind the speakers that can often appear to be many meters deep and wide , the wall behind the speakers disappears completely and the bass instruments are an equally identifiable part of the illusion in their own space and in proportion to the rest of the instruments .

So in my opinion modern transmission line speakers do have a real and clear advantage , but I am sure many others will disagree.

I am sorry that I can't give you a more technical explanation but I have done my best to explain what my transmission line speakers do for me that other types of speaker don't seem to be able to .

 

[lindsayt]

With Linn Isobariks and Saras it's not particularly the isobaric design that gives amplifiers grief, it's the fact that they use two 8ohm (with dips below 8 ohms) drivers wired in parallel. In general amplifiers, especially valve ones, prefer speaker loads that have impedances that stay above 6 ohms. The relatively inefficient KEF bass drivers don't help either.

There are lots of ported designs that gives amps a hard time too because of wired in parallel drivers and low efficiency. Or the use of single 4 ohm mid-bass drivers.

It's quite possible to design an isobaric speaker with a relatively benign amplifier load.

If you're going to use multiple drivers and want to give your amps an easier time use two 16 ohm drivers wired in parallel, or use four 8 ohm drivers wired in parallel and in series. It's simple schoolboy electronics, with the aim to get 8 ohms or higher.

 

[CnoEvil]

So in my opinion modern transmission line speakers do have a real and clear advantage , but I am sure many others will disagree.

I am sorry that I can't give you a more technical explanation but I have done my best to explain what my transmission line speakers do for me that other types of speaker don't seem to be able to .

I asked for insight, so thank you for that.

Bass that has impressed me has come from the Kef Ref 205/207 and the bigger Focal Utopias.

I really like the way the Kefs have realistic snap and attack while sounding natural, without getting harsh, on the end of a Class A amp....but it is a very well thought out and implemented design.

 

[CnoEvil]

I think most Isobarik designs tend to be fairly difficult loads, due to the doubling up of the drivers (I think there are more complex reasons too, i just dont understand them )

The Totem Mani-2's are supposed to be pretty well sorted sound speakers that sound great, using the Isobarik loading design. Maybe it works better for standmounted speakers than floor standers?

As an aside, in my experience the bass from transmission line speakers can sound quite different to rear ported speakers, although I dont fully understand why. IMO a well sorted transmission line speaker (IE PMC for eg) can have fantastic bass quality and quantity, from a relatively small enclosure. They are often easier to postition that rear ported speakers too

TLs do seem to allow a big sound from a slim cabinet.

 

[lindsayt]

The problem that I have with the transmission line speakers that I've heard is in the bass timing. There are certain bass frequencies where the bass has lagged behind the rest of the music. It's a smearing of the bass signal, especially on repetitive bass transients. It becomes more of an issue at generous to loud volumes.

 

[iceman16]

IME tl is more on the cleaner, taut ,and agile response..but it sometimes it lacks the "oomph" and full bodied other may offer. sorry YMMV

 

[ID.]

Thanks for your insightful posts lindsayt. Particularly on Isobaric speakers. I'd wondered about them but never heard them or knew much about them.

 

[iceman16]

I could'nt agree more to the past post on how each was implemented (TL,Isobaric etc...)

 

[Electro]

So in my opinion modern transmission line speakers do have a real and clear advantage , but I am sure many others will disagree.

I am sorry that I can't give you a more technical explanation but I have done my best to explain what my transmission line speakers do for me that other types of speaker don't seem to be able to .

I asked for insight, so thank you for that.

Bass that has impressed me has come from the Kef Ref 205/207 and the bigger Focal Utopias.

I really like the way the Kefs have realistic snap and attack while sounding natural, without getting harsh, on the end of a Class A amp....but it is a very well thought out and implemented design.

I really must try to listen to some of the new KEF reference range seeing as they seem to be so universally praised , I have never seen a bad word written about them although I doubt that I will be tempted away from my PMC's but you never know

I heard some TL's made by Jean Marie Renaud a few years ago and although they sounded different to the PMC's they had similar effortless natural bass qualities , they were lovely speakers .

Even though I tried to explain in my last post why I prefer transmission line type speakers I forgot the most important reason and that is the ability to reproduce bass sounds that are directional . Why do people say that bass is not directional :O

When listening to live music it is easy to hear where a double bass or bass drum is placed on the stage with your eyes closed , but when listening to most speakers it is not possible to do the same thing.

But transmission line speaker seem to be able to reproduce this directional bass information easily and in my opinion it makes reproduced music sound so much more realistic .